Idiopathic intracranial hypertension
Encyclopedia
Idiopathic intracranial hypertension (IIH), sometimes called by the older names benign intracranial hypertension (BIH) or pseudotumor cerebri (PTC), is a neurological disorder
that is characterized by increased intracranial pressure
(pressure around the brain) in the absence of a tumor
or other diseases. The main symptoms are headache
, nausea
and vomiting
, as well as pulsatile tinnitus
(buzzing in the ears synchronous with the pulse), double vision
and other visual symptoms. If untreated, it may lead to swelling
of the optic disc
in the eye, which can progress to vision loss
.
IIH is diagnosed with a brain scan
(to rule out other causes) and a lumbar puncture
; lumbar puncture may also provide temporary and sometimes permanent relief from the symptoms. Some respond to medication
(with the drug acetazolamide
), but others require surgery to relieve the pressure. The condition may occur in all age groups, but is most common in young women, especially those with obesity
.
, such as cough
ing and sneezing
. The pain may also be experienced in the neck and shoulders. Many have pulsatile tinnitus
, a whooshing sensation in one or both ears (64–87%); this sound is synchronous with the pulse. Various other symptoms, such as numbness of the extremities, generalized weakness, loss of smell, and incoordination
, are reported more rarely; none are specific for IIH. In children, numerous nonspecific signs and symptoms may be present.
The increased pressure leads to compression and traction of the cranial nerves, a group of nerves that arise from the brain stem
and supply the face and neck. Most commonly, the abducens nerve (sixth nerve) is involved. This nerve supplies the muscle that pulls the eye outward. Those with sixth nerve palsy
therefore experience horizontal double vision which is worse when looking towards the affected side. More rarely, the oculomotor nerve
and trochlear nerve
(third
and fourth nerve palsy
, respectively) are affected; both play a role in eye movements. The facial nerve
(seventh cranial nerve) is affected occasionally –- the result is total or partial weakness of the muscles of facial expression on one or both sides of the face.
The increased pressure leads to papilledema
, which is swelling of the optic disc
, the spot where the optic nerve
enters the eye
ball. This occurs in practically all cases of IIH, but not everyone experiences symptoms from this. Those who do experience symptoms typically report "transient visual obscurations", episodes of difficulty seeing that occur in both eyes but not necessarily at the same time. Long-term untreated papilledema leads to visual loss, initially in the periphery but progressively towards the center of vision.
Physical examination of the nervous system
is typically normal apart from the presence of papilledema, which is seen on examination of the eye with a small device called an ophthalmoscope or in more detail with a fundus camera
. If there are cranial nerve abnormalities, these may be noticed on eye examination
in the form of a squint
(third, fourth, or sixth nerve palsy) or as facial nerve palsy. If the papilledema has been longstanding, visual field
s may be constricted and visual acuity
may be decreased. Visual field test
ing by automated (Humphrey) perimetry is recommended as other methods of testing may be less accurate. Longstanding papilledema leads to optic atrophy, in which the disc looks pale and visual loss tends to be advanced.
may be increased due to medications such as high-dose vitamin A
derivatives (e.g. isotretinoin
for acne
), long-term tetracycline antibiotics
(for a variety of skin conditions) and hormonal contraceptives. There are numerous other diseases, mostly rare conditions, that may lead to intracranial hypertension. If there is an underlying cause, the condition is termed "secondary intracranial hypertension". Common causes of secondary intracranial hypertension include obstructive sleep apnea
(a sleep-related breathing disorder), systemic lupus erythematosis (SLE), chronic kidney disease, and Behçet's disease
.
(CSF) and blood inside the bony cranial vault. Three theories therefore exist as to why the pressure might be raised in IIH: an excess of CSF production, increased volume of blood or brain tissue, or obstruction of the veins that drain blood from the brain
.
The first theory, that of increased production of cerebrospinal fluid, was proposed in early descriptions of the disease. However, there is no experimental data that supports a role for this process in IIH.
The second theory posits that either increased blood flow to the brain or increase in the brain tissue itself may result in the raised pressure. Little evidence has accumulated to support the suggestion that increased blood flow plays a role, but both biopsy
samples and various types of brain scans have shown an increased water content of the brain tissue. It remains unclear why this might be the case.
The third theory suggests that blood flow from the brain may be impaired or congested. Only in a small proportion of patients has underlying narrowing of the cerebral sinuses or veins been demonstrated. Congestion of venous blood may result from a generally increased venous pressure, which has been linked to obesity.
, usually with computed tomography
(CT/CAT) or magnetic resonance imaging
(MRI), is used to detect any mass lesions. In IIH these scans may be normal, although small or slit-like ventricles
and "empty sella sign
" (flattening of the pituitary gland
due to increased pressure) may be seen. An MR venogram is also performed in most cases (or according to some experts, only in atypical cases) to exclude the possibility of venous obstruction or cerebral venous sinus thrombosis
.
Lumbar puncture
is performed to measure the opening pressure, as well as to obtain cerebrospinal fluid
(CSF) to exclude alternative diagnoses. If the opening pressure is increased, CSF may be removed for relief (see below). The CSF is examined for abnormal cells, infections, antibody levels, the glucose
level, and protein
levels. In indiopathic intracranial hypertenssion, by definition all of these are within their normal limits. Occasionally, the pressure measurement may be normal despite very suggestive symptoms. This may be attributable to the fact that CSF pressure may fluctuate over the course of the normal day. If the suspicion of problems remains high, it may be necessary to perform more long-term monitoring of the ICP by a pressure catheter.
in 1937.
They were modified by Smith in 1985 to become the "modified Dandy criteria". Smith included the use of more advanced imaging: Dandy had required ventriculography
, but Smith replaced this with computed tomography
. In a 2001 paper, Digre and Corbett amended Dandy's criteria further. They added the requirement that the patient is awake and alert, as coma precludes adequate neurological assessment, and require exclusion of venous sinus thrombosis as an underlying cause. Furthermore, they add the requirement that no other cause for the raised ICP is found.
In a 2002 review, Friedman and Jacobson propose an alternative set of criteria, derived from Smith's. These require the absence of symptoms that could not be explained by a diagnosis of IIH, but do not require the actual presence of any symptoms (such as headache) attributable to IIH. These criteria also require that the lumbar puncture is performed with patient lying sideways, as a lumbar puncture performed in the upright sitting position can lead to artificially high pressure measurements. Friedman and Jacobson also do not insist on MR venography for every patient; rather, this is only required in atypical cases (see "diagnosis" above).
The first step in symptom control is drainage of cerebrospinal fluid by lumbar puncture. If necessary, this may be performed at the same time as a diagnostic LP (such as on in search of a CSF infection). In some cases, this is sufficient to control the symptoms, and no further treatment is needed.
The procedure can be repeated if necessary, but this is generally taken as a clue that additional treatments may be required to control the symptoms and preserve vision. Repeated lumbar punctures are regarded as unpleasant by patients, and they present a danger of introducing spinal infections if done too often. Repeated lumbar punctures are sometimes needed to control the ICP urgently if the patient's vision deteriorates rapidly.
(Diamox), which acts by inhibiting the enzyme carbonic anhydrase
, and it reduces CSF production by six to 57 percent. It can cause the symptoms of hypokalemia
(low blood potassium levels), which include muscle weakness and tingling in the fingers. Acetazolamide cannot be used in pregnancy, since it has shown to cause embryonic abnormalities in animal studies. Also, in human beings it has been shown to cause metabolic acidosis
as well as disruptions in the blood electrolyte levels newborn babies. The diuretic furosemide
is sometimes used for a treatment if acetazolamide is not well-tolerated, but this drug sometimes has little effect on the ICP.
Various analgesic
s (painkillers) may be used in controlling the headaches of intracranial hypertension. In addition to conventional agents such as paracetamol
, a low dose of the antidepressant amitriptyline
or the anticonvulsant topiramate
have shown some additional benefit for pain relief.
The use of steroids
in the attempt to reduce the ICP is controversial. These may be used in severe papilledema, but otherwise their use is discouraged.
. Surgery would normally only be offered if medical therapy is either unsuccessful or not tolerated. The choice between these two procedures depends on the predominant problem in IIH. Neither procedure is perfect: both may cause significant complications, and both may eventually fail in controlling the symptoms. There are no randomized controlled trial
s to guide the decision as to which procedure is best.
Optic nerve sheath fenestration is an ophthalmological
operation that involves the making of an incision in the connective tissue lining of the optic nerve
in its portion behind the eye. It is not entirely clear how it protects the eye from the raised pressure, but it may be the result of either diversion of the CSF into the orbit
or the creation of an area of scar tissue that lowers the pressure. The effects on the intracranial pressure itself are more modest. Moreover, the procedure may lead to significant complications, including blindness in 1–2%. The procedure is therefore recommended mainly in those who have limited headache symptoms but significant papilledema or threatened vision, or in those who have undergone unsuccessful treatment with a shunt or have a contraindication for shunt surgery.
Shunt surgery, usually performed by neurosurgeons
, involves the creation of a conduit by which CSF can be drained into another body cavity. The initial procedure is usually a lumboperitoneal (LP) shunt
, which connects the subarachnoid space in the lumbar spine with the peritoneal cavity
. Generally, a pressure valve is included in the circuit to avoid excessive drainage when the patient is erect and therefore has a relatively high ICP. LP shunting provides long-term relief in about half the cases; others require revision of the shunt, often on more than one occasion—usually due to shunt obstruction. If the lumboperitoneal shunt needs repeated revisions, a ventriculoatrial or ventriculoperitoneal shunt may be considered. These shunts are inserted in one of the lateral ventricles
of the brain, usually by stereotactic surgery
, and then connected either to the right atrium
of the heart or the peritoneal cavity, respectively. Given the reduced need for revisions in ventricular shunts, it is possible that this procedure will become the first-line type of shunt treatment.
In cases of severe obesity, gastric bypass surgery
has been shown to lead to a marked improvement in symptoms.
IIH does not normally affect life expectancy. The major complications from IIH arise from untreated or treatment-resistant papilledema
. In various case series, the long-term risk of ones vision being significantly affected by IIH is reported to lie anywhere between 10 and 25%.
On average, IIH occurs in about one per 100,000 people, and can occur in children and adults. The median
age at diagnosis is 30. IIH occurs predominantly in women, especially in the ages 20 to 45, who are four to eight times more likely than men to be affected. Overweight
and obesity
strongly predispose a person to IIH: women who are more than ten percent over their ideal body weight are thirteen times more likely to develop IIH, and this figure goes up to nineteen times in women who are more than twenty percent over their ideal body weight. In men this relationship also exists, but the increase is only five-fold in those over 20 percent above their ideal body weight.
Despite several reports of IIH in families, there is no known genetic cause for IIH. People from all ethnicities may develop IIH. In children, there is no difference in incidence between males and females.
From national hospital admission databases it appears that the need for neurosurgical intervention for IIH has increased markedly over the period between 1988 and 2002. This has been attributed at least in part to the rising prevalence of obesity, although some of this increase may be explained by the increased popularity of shunting over optic nerve sheath fenestration.
, who described it in 1893 under the name serous meningitis. The term "pseudotumor cerebri" was introduced in 1904 by his compatriot Max Nonne
. Numerous other cases appeared in the literature subsequently; in many cases, the raised intracranial pressure may actually have resulted from underlying conditions. For instance, the otitic hydrocephalus reported by London neurologist Sir Charles Symonds
may have resulted from venous sinus thrombosis caused by middle ear infection
. Diagnostic criteria for IIH were developed in 1937 by the Baltimore neurosurgeon Walter Dandy
; Dandy also introduced subtemporal decompressive surgery in the treatment of the condition.
The terms "benign" and "pseudotumor" derive from the fact that increased intracranial pressure may be associated with brain tumor
s. Those patients in whom no tumour was found were therefore diagnosed with "pseudotumor cerebri" (a disease mimicking a brain tumor). The disease was renamed "benign intracranial hypertension" in 1955 to distinguish it from intracranial hypertension due to life-threatening diseases (such as cancer); however, this was also felt to be misleading because any disease that can blind someone should not be thought of as benign, and the name was therefore revised in 1989 to "idiopathic (of no identifiable cause) intracranial hypertension".
Shunt surgery was introduced in 1949; initially, ventriculoperitoneal shunts were used. In 1971, good results were reported with lumboperitoneal shunting. Negative reports on shunting in the 1980s led to a brief period (1988–1993) during which optic nerve fenestration (which had initially been described in an unrelated condition in 1871) was more popular. Since then, shunting is recommended predominantly, with occasional exceptions.
Neurological disorder
A neurological disorder is a disorder of the body's nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord, or in the nerves leading to or from them, can result in symptoms such as paralysis, muscle weakness, poor coordination, loss of sensation, seizures,...
that is characterized by increased intracranial pressure
Intracranial pressure
Intracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...
(pressure around the brain) in the absence of a tumor
Brain tumor
A brain tumor is an intracranial solid neoplasm, a tumor within the brain or the central spinal canal.Brain tumors include all tumors inside the cranium or in the central spinal canal...
or other diseases. The main symptoms are headache
Headache
A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...
, nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
and vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, as well as pulsatile tinnitus
Tinnitus
Tinnitus |ringing]]") is the perception of sound within the human ear in the absence of corresponding external sound.Tinnitus is not a disease, but a symptom that can result from a wide range of underlying causes: abnormally loud sounds in the ear canal for even the briefest period , ear...
(buzzing in the ears synchronous with the pulse), double vision
Diplopia
Diplopia, commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, or diagonally in relation to each other...
and other visual symptoms. If untreated, it may lead to swelling
Papilledema
Papilledema is optic disc swelling that is caused by increased intracranial pressure. The swelling is usually bilateral and can occur over a period of hours to weeks. Unilateral presentation is extremely rare....
of the optic disc
Optic disc
The optic disc or optic nerve head is the location where ganglion cell axons exit the eye to form the optic nerve. There are no light sensitive rods or cones to respond to a light stimulus at this point. This causes a break in the visual field called "the blind spot" or the "physiological blind spot"...
in the eye, which can progress to vision loss
Vision loss
Vision loss or visual loss is the absence of vision where it existed before, which can happen either acutely or chronically .-Ranges of vision loss:...
.
IIH is diagnosed with a brain scan
Neuroimaging
Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function/pharmacology of the brain...
(to rule out other causes) and a lumbar puncture
Lumbar puncture
A lumbar puncture is a diagnostic and at times therapeutic procedure that is performed in order to collect a sample of cerebrospinal fluid for biochemical, microbiological, and cytological analysis, or very rarely as a treatment to relieve increased intracranial pressure.-Indications:The...
; lumbar puncture may also provide temporary and sometimes permanent relief from the symptoms. Some respond to medication
Medication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
(with the drug acetazolamide
Acetazolamide
Acetazolamide, sold under the trade name Diamox, is a carbonic anhydrase inhibitor that is used to treat glaucoma, epileptic seizures, Idiopathic intracranial hypertension , altitude sickness, cystinuria, and dural ectasia...
), but others require surgery to relieve the pressure. The condition may occur in all age groups, but is most common in young women, especially those with obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
.
Signs and symptoms
The most common symptom of IIH is headache, which occurs in almost all (92–94%) cases. It is characteristically worse in the morning, generalized in character and throbbing in nature. It may be associated with nausea and vomiting. The headache can be made worse by any activity that further increases the intracranial pressureValsalva maneuver
The Valsalva maneuver or Valsalva manoeuvre is performed by moderately forceful attempted exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut...
, such as cough
Cough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...
ing and sneezing
Sneeze
A sneeze is a semi-autonomous, convulsive expulsion of air from the lungs through the nose and mouth, usually caused by foreign particles irritating the nasal mucosa...
. The pain may also be experienced in the neck and shoulders. Many have pulsatile tinnitus
Tinnitus
Tinnitus |ringing]]") is the perception of sound within the human ear in the absence of corresponding external sound.Tinnitus is not a disease, but a symptom that can result from a wide range of underlying causes: abnormally loud sounds in the ear canal for even the briefest period , ear...
, a whooshing sensation in one or both ears (64–87%); this sound is synchronous with the pulse. Various other symptoms, such as numbness of the extremities, generalized weakness, loss of smell, and incoordination
Ataxia
Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...
, are reported more rarely; none are specific for IIH. In children, numerous nonspecific signs and symptoms may be present.
The increased pressure leads to compression and traction of the cranial nerves, a group of nerves that arise from the brain stem
Brain stem
In vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...
and supply the face and neck. Most commonly, the abducens nerve (sixth nerve) is involved. This nerve supplies the muscle that pulls the eye outward. Those with sixth nerve palsy
Sixth nerve palsy
Sixth nerve palsy, or abducens nerve palsy, is a disorder associated with dysfunction of cranial nerve VI , which is responsible for contracting the lateral rectus muscle to abduct the eye...
therefore experience horizontal double vision which is worse when looking towards the affected side. More rarely, the oculomotor nerve
Oculomotor nerve
The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is...
and trochlear nerve
Trochlear nerve
The trochlear nerve is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye....
(third
Oculomotor nerve palsy
Oculomotor nerve palsy is an eye condition resulting from damage to the third cranial nerve or a branch thereof. As the name suggests, the oculomotor nerve supplies the majority of the muscles controlling eye movements. Thus, damage to this nerve will result in the affected individual being unable...
and fourth nerve palsy
Fourth nerve palsy
Fourth nerve palsy is a condition caused by weakness or paralysis of the superior oblique muscle. This condition often causes double vision as the weakened muscle prevents the eyes from moving in the same direction....
, respectively) are affected; both play a role in eye movements. The facial nerve
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
(seventh cranial nerve) is affected occasionally –- the result is total or partial weakness of the muscles of facial expression on one or both sides of the face.
The increased pressure leads to papilledema
Papilledema
Papilledema is optic disc swelling that is caused by increased intracranial pressure. The swelling is usually bilateral and can occur over a period of hours to weeks. Unilateral presentation is extremely rare....
, which is swelling of the optic disc
Optic disc
The optic disc or optic nerve head is the location where ganglion cell axons exit the eye to form the optic nerve. There are no light sensitive rods or cones to respond to a light stimulus at this point. This causes a break in the visual field called "the blind spot" or the "physiological blind spot"...
, the spot where the optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
enters the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
ball. This occurs in practically all cases of IIH, but not everyone experiences symptoms from this. Those who do experience symptoms typically report "transient visual obscurations", episodes of difficulty seeing that occur in both eyes but not necessarily at the same time. Long-term untreated papilledema leads to visual loss, initially in the periphery but progressively towards the center of vision.
Physical examination of the nervous system
Neurological examination
A neurological examination is the assessment of sensory neuron and motor responses, especially reflexes, to determine whether the nervous system is impaired...
is typically normal apart from the presence of papilledema, which is seen on examination of the eye with a small device called an ophthalmoscope or in more detail with a fundus camera
Fundus camera
A fundus camera or retinal camera is a specialized low power microscope with an attached camera designed to photograph the interior surface of the eye, including the retina, optic disc, macula, and posterior pole A fundus camera or retinal camera is a specialized low power microscope with an...
. If there are cranial nerve abnormalities, these may be noticed on eye examination
Eye examination
An eye examination is a battery of tests performed by an ophthalmologist, optometrist, or orthoptist assessing vision and ability to focus on and discern objects, as well as other tests and examinations pertaining to the eyes....
in the form of a squint
Strabismus
Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...
(third, fourth, or sixth nerve palsy) or as facial nerve palsy. If the papilledema has been longstanding, visual field
Visual field
The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while 'field of view' "refers to the physical...
s may be constricted and visual acuity
Visual acuity
Visual acuity is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain....
may be decreased. Visual field test
Visual field test
A visual field test is an examination that may be performed to analyze a patient's visual field. The exam may be performed by a technician in one of several ways. The test may be performed by a technician directly, with the assistance of a machine, or completely by an automated machine...
ing by automated (Humphrey) perimetry is recommended as other methods of testing may be less accurate. Longstanding papilledema leads to optic atrophy, in which the disc looks pale and visual loss tends to be advanced.
Causes
"Idiopathic" means "of unknown etiology". Therefore, IIH can only be diagnosed if there is no alternative explanation for the symptoms. Intracranial pressureIntracranial pressure
Intracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...
may be increased due to medications such as high-dose vitamin A
Vitamin A
Vitamin A is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal, that is necessary for both low-light and color vision...
derivatives (e.g. isotretinoin
Isotretinoin
Isotretinoin, INN, is a medication used mostly for cystic acne. It was first developed for brain, pancreatic and other cancers. It is used to treat harlequin-type ichthyosis, a usually lethal skin disease, and lamellar ichthyosis. Its effects are systemic and nonselective...
for acne
Acne vulgaris
Acne vulgaris is a common human skin disease, characterized by areas of skin with seborrhea , comedones , papules , pustules , Nodules and possibly scarring...
), long-term tetracycline antibiotics
Tetracycline antibiotics
Tetracyclines are a group of broad-spectrum antibiotics whose general usefulness has been reduced with the onset of bacterial resistance. Despite this, they remain the treatment of choice for some specific indications....
(for a variety of skin conditions) and hormonal contraceptives. There are numerous other diseases, mostly rare conditions, that may lead to intracranial hypertension. If there is an underlying cause, the condition is termed "secondary intracranial hypertension". Common causes of secondary intracranial hypertension include obstructive sleep apnea
Obstructive sleep apnea
Obstructive sleep apnea or obstructive sleep apnea syndrome is the most common type of sleep apnea and is caused by obstruction of the upper airway. It is characterized by repetitive pauses in breathing during sleep, despite the effort to breathe, and is usually associated with a reduction in...
(a sleep-related breathing disorder), systemic lupus erythematosis (SLE), chronic kidney disease, and Behçet's disease
Behçet's disease
Behçet's disease is a rare immune-mediated systemic vasculitis that often presents with mucous membrane ulceration and ocular involvements...
.
Mechanism
The cause of IIH is not known. The Monro-Kellie rule states that the intracranial pressure (literally: pressure inside the skull) is determined by the amount of brain tissue, cerebrospinal fluidCerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
(CSF) and blood inside the bony cranial vault. Three theories therefore exist as to why the pressure might be raised in IIH: an excess of CSF production, increased volume of blood or brain tissue, or obstruction of the veins that drain blood from the brain
Cerebral veins
The cerebral veins are divisible into external and internal groups according to the outer surfaces or the inner parts of the hemispheres they drain into....
.
The first theory, that of increased production of cerebrospinal fluid, was proposed in early descriptions of the disease. However, there is no experimental data that supports a role for this process in IIH.
The second theory posits that either increased blood flow to the brain or increase in the brain tissue itself may result in the raised pressure. Little evidence has accumulated to support the suggestion that increased blood flow plays a role, but both biopsy
Biopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
samples and various types of brain scans have shown an increased water content of the brain tissue. It remains unclear why this might be the case.
The third theory suggests that blood flow from the brain may be impaired or congested. Only in a small proportion of patients has underlying narrowing of the cerebral sinuses or veins been demonstrated. Congestion of venous blood may result from a generally increased venous pressure, which has been linked to obesity.
Diagnosis
The diagnosis may be suspected on the basis of the history and examination. To confirm the diagnosis, as well as excluding alternative causes, several investigations are required; more investigations may be performed if the history is not typical or the patient is more likely to have an alternative problem: children, men, the elderly, or women who are not overweight.Investigations
NeuroimagingNeuroimaging
Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function/pharmacology of the brain...
, usually with computed tomography
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
(CT/CAT) or magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(MRI), is used to detect any mass lesions. In IIH these scans may be normal, although small or slit-like ventricles
Ventricular system
The ventricular system is a set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal of the spinal cord.-Components:The system comprises four ventricles:* right and left lateral ventricles* third ventricle...
and "empty sella sign
Empty sella syndrome
Empty sella syndrome is a disorder that involves the sella turcica, a bony structure at the base of the brain that surrounds and protects the pituitary gland...
" (flattening of the pituitary gland
Pituitary gland
In vertebrate anatomy the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 g , in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity covered by a dural fold...
due to increased pressure) may be seen. An MR venogram is also performed in most cases (or according to some experts, only in atypical cases) to exclude the possibility of venous obstruction or cerebral venous sinus thrombosis
Cerebral venous sinus thrombosis
Cerebral venous sinus thrombosis is a rare form of stroke that results from thrombosis of the dural venous sinuses, which drain blood from the brain. Symptoms may include headache, abnormal vision, any of the symptoms of stroke such as weakness of the face and limbs on one side of the body, and...
.
Lumbar puncture
Lumbar puncture
A lumbar puncture is a diagnostic and at times therapeutic procedure that is performed in order to collect a sample of cerebrospinal fluid for biochemical, microbiological, and cytological analysis, or very rarely as a treatment to relieve increased intracranial pressure.-Indications:The...
is performed to measure the opening pressure, as well as to obtain cerebrospinal fluid
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
(CSF) to exclude alternative diagnoses. If the opening pressure is increased, CSF may be removed for relief (see below). The CSF is examined for abnormal cells, infections, antibody levels, the glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
level, and protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
levels. In indiopathic intracranial hypertenssion, by definition all of these are within their normal limits. Occasionally, the pressure measurement may be normal despite very suggestive symptoms. This may be attributable to the fact that CSF pressure may fluctuate over the course of the normal day. If the suspicion of problems remains high, it may be necessary to perform more long-term monitoring of the ICP by a pressure catheter.
Classification
The original criteria for IIH were described by DandyWalter Dandy
Walter Edward Dandy, M.D. was an American neurosurgeon and scientist. He is considered one of the founding fathers of neurosurgery, along with Victor Horsley and Harvey Cushing...
in 1937.
| 1 Signs & symptoms of increased ICP – CSF pressure >25 cmH2O |
| 2 No localizing signs with the exception of abducens nerve palsy |
| 3 Normal CSF composition |
| 4 Normal to small (slit) ventricles on imaging with no intracranial mass |
They were modified by Smith in 1985 to become the "modified Dandy criteria". Smith included the use of more advanced imaging: Dandy had required ventriculography
Cerebral ventriculography
Cerebral ventriculography is a medical procedure developed by Walter Dandy, and designed to enable visualization of structures inside the skull. In this procedure, holes are drilled in the skull, and air pumped through the holes in to the ventricles, to facilitate clearer imaging on X-rays.It has...
, but Smith replaced this with computed tomography
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
. In a 2001 paper, Digre and Corbett amended Dandy's criteria further. They added the requirement that the patient is awake and alert, as coma precludes adequate neurological assessment, and require exclusion of venous sinus thrombosis as an underlying cause. Furthermore, they add the requirement that no other cause for the raised ICP is found.
| 1 Symptoms of raised intracranial pressure (headache, nausea, vomiting, transient visual obscurations, or papilledema) |
| 2 No localizing signs with the exception of abducens (sixth) nerve palsy |
| 3 The patient is awake and alert |
| 4 Normal CT/MRI findings without evidence of thrombosis |
| 5 LP opening pressure of >25 cmH2O and normal biochemical and cytological composition of CSF |
| 6 No other explanation for the raised intracranial pressure |
In a 2002 review, Friedman and Jacobson propose an alternative set of criteria, derived from Smith's. These require the absence of symptoms that could not be explained by a diagnosis of IIH, but do not require the actual presence of any symptoms (such as headache) attributable to IIH. These criteria also require that the lumbar puncture is performed with patient lying sideways, as a lumbar puncture performed in the upright sitting position can lead to artificially high pressure measurements. Friedman and Jacobson also do not insist on MR venography for every patient; rather, this is only required in atypical cases (see "diagnosis" above).
Treatment
The primary goal in treatment of IIH is the prevention of visual loss and blindness, as well as symptom control. IIH is treated mainly through the reduction of CSF pressure and, where applicable, weight loss. IIH may resolve after initial treatment, may go into spontaneous remission (although it can still relapse at a later stage), or may continue chronically.Lumbar puncture
The procedure can be repeated if necessary, but this is generally taken as a clue that additional treatments may be required to control the symptoms and preserve vision. Repeated lumbar punctures are regarded as unpleasant by patients, and they present a danger of introducing spinal infections if done too often. Repeated lumbar punctures are sometimes needed to control the ICP urgently if the patient's vision deteriorates rapidly.
Medication
The best-studied medical treatment for intracranial hypertension is acetazolamideAcetazolamide
Acetazolamide, sold under the trade name Diamox, is a carbonic anhydrase inhibitor that is used to treat glaucoma, epileptic seizures, Idiopathic intracranial hypertension , altitude sickness, cystinuria, and dural ectasia...
(Diamox), which acts by inhibiting the enzyme carbonic anhydrase
Carbonic anhydrase
The carbonic anhydrases form a family of enzymes that catalyze the rapid interconversion of carbon dioxide and water to bicarbonate and protons , a reversible reaction that occurs rather slowly in the absence of a catalyst...
, and it reduces CSF production by six to 57 percent. It can cause the symptoms of hypokalemia
Hypokalemia
Hypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low...
(low blood potassium levels), which include muscle weakness and tingling in the fingers. Acetazolamide cannot be used in pregnancy, since it has shown to cause embryonic abnormalities in animal studies. Also, in human beings it has been shown to cause metabolic acidosis
Metabolic acidosis
In medicine, metabolic acidosis is a condition that occurs when the body produces too much acid or when the kidneys are not removing enough acid from the body. If unchecked, metabolic acidosis leads to acidemia, i.e., blood pH is low due to increased production of hydrogen by the body or the...
as well as disruptions in the blood electrolyte levels newborn babies. The diuretic furosemide
Furosemide
Furosemide or frusemide is a loop diuretic used in the treatment of congestive heart failure and edema. It is most commonly marketed by Sanofi-Aventis under the brand name Lasix...
is sometimes used for a treatment if acetazolamide is not well-tolerated, but this drug sometimes has little effect on the ICP.
Various analgesic
Analgesic
An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....
s (painkillers) may be used in controlling the headaches of intracranial hypertension. In addition to conventional agents such as paracetamol
Paracetamol
Paracetamol INN , or acetaminophen USAN , is a widely used over-the-counter analgesic and antipyretic . It is commonly used for the relief of headaches and other minor aches and pains and is a major ingredient in numerous cold and flu remedies...
, a low dose of the antidepressant amitriptyline
Amitriptyline
Amitriptyline is a tricyclic antidepressant . It is the most widely used TCA and has at least equal efficacy against depression as the newer class of SSRIs...
or the anticonvulsant topiramate
Topiramate
Topiramate is an anticonvulsant drug. It was originally produced by Ortho-McNeil Neurologics and Noramco, Inc., both divisions of the Johnson & Johnson Corporation. This medication was discovered in 1979 by Bruce E. Maryanoff and Joseph F. Gardocki during their research work at McNeil...
have shown some additional benefit for pain relief.
The use of steroids
Glucocorticoid
Glucocorticoids are a class of steroid hormones that bind to the glucocorticoid receptor , which is present in almost every vertebrate animal cell...
in the attempt to reduce the ICP is controversial. These may be used in severe papilledema, but otherwise their use is discouraged.
Surgery
Two main surgical procedures exist in the treatment of IIH: optic nerve sheath decompression and fenestration and shuntingCerebral shunt
Cerebral shunts are commonly used to treat hydrocephalus, the swelling of the brain due to excess buildup of cerebrospinal fluid . If left unchecked, the cerebral spinal fluid can build up leading to an increase in intracranial pressure which can lead to intracranial hematoma, cerebral edema,...
. Surgery would normally only be offered if medical therapy is either unsuccessful or not tolerated. The choice between these two procedures depends on the predominant problem in IIH. Neither procedure is perfect: both may cause significant complications, and both may eventually fail in controlling the symptoms. There are no randomized controlled trial
Randomized controlled trial
A randomized controlled trial is a type of scientific experiment - a form of clinical trial - most commonly used in testing the safety and efficacy or effectiveness of healthcare services or health technologies A randomized controlled trial (RCT) is a type of scientific experiment - a form of...
s to guide the decision as to which procedure is best.
Optic nerve sheath fenestration is an ophthalmological
Ophthalmology
Ophthalmology is the branch of medicine that deals with the anatomy, physiology and diseases of the eye. An ophthalmologist is a specialist in medical and surgical eye problems...
operation that involves the making of an incision in the connective tissue lining of the optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
in its portion behind the eye. It is not entirely clear how it protects the eye from the raised pressure, but it may be the result of either diversion of the CSF into the orbit
Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...
or the creation of an area of scar tissue that lowers the pressure. The effects on the intracranial pressure itself are more modest. Moreover, the procedure may lead to significant complications, including blindness in 1–2%. The procedure is therefore recommended mainly in those who have limited headache symptoms but significant papilledema or threatened vision, or in those who have undergone unsuccessful treatment with a shunt or have a contraindication for shunt surgery.
Shunt surgery, usually performed by neurosurgeons
Neurosurgery
Neurosurgery is the medical specialty concerned with the prevention, diagnosis, treatment, and rehabilitation of disorders which affect any portion of the nervous system including the brain, spine, spinal cord, peripheral nerves, and extra-cranial cerebrovascular system.-In the United States:In...
, involves the creation of a conduit by which CSF can be drained into another body cavity. The initial procedure is usually a lumboperitoneal (LP) shunt
Lumbar-peritoneal shunt
A lumbar-peritoneal shunt is a type of cerebral shunt.-Lumbar-peritoneal shunt:A shunt is described as a tube, catheter or "surgically created anastomosis" and is designed to bypass or redirect bodily fluids from one point in the body to another....
, which connects the subarachnoid space in the lumbar spine with the peritoneal cavity
Peritoneal cavity
The peritoneal cavity is a potential space between the parietal peritoneum and visceral peritoneum, that is, the two membranes that separate the organs in the abdominal cavity from the abdominal wall...
. Generally, a pressure valve is included in the circuit to avoid excessive drainage when the patient is erect and therefore has a relatively high ICP. LP shunting provides long-term relief in about half the cases; others require revision of the shunt, often on more than one occasion—usually due to shunt obstruction. If the lumboperitoneal shunt needs repeated revisions, a ventriculoatrial or ventriculoperitoneal shunt may be considered. These shunts are inserted in one of the lateral ventricles
Lateral ventricles
The lateral ventricles are part of the ventricular system of the brain. Classified as part of the telencephalon, they are the largest of the ventricles....
of the brain, usually by stereotactic surgery
Stereotactic surgery
Stereotactic surgery or stereotaxy is a minimally invasive form of surgical intervention which makes use of a three-dimensional coordinates system to locate small targets inside the body and to perform on them some action such as ablation, biopsy, lesion, injection, stimulation, implantation,...
, and then connected either to the right atrium
Right atrium
The right atrium is one of four chambers in the hearts of mammals and archosaurs...
of the heart or the peritoneal cavity, respectively. Given the reduced need for revisions in ventricular shunts, it is possible that this procedure will become the first-line type of shunt treatment.
In cases of severe obesity, gastric bypass surgery
Gastric bypass surgery
Gastric bypass procedures are any of a group of similar operations that first divides the stomach into a small upper pouch and a much larger lower "remnant" pouch and then re-arranges the small intestine to allow both pouches to stay connected to it. Surgeons have developed several different ways...
has been shown to lead to a marked improvement in symptoms.
Prognosis
It is not known what percentage of people with IIH will remit spontaneously, and what percentage will develop chronic disease.IIH does not normally affect life expectancy. The major complications from IIH arise from untreated or treatment-resistant papilledema
Papilledema
Papilledema is optic disc swelling that is caused by increased intracranial pressure. The swelling is usually bilateral and can occur over a period of hours to weeks. Unilateral presentation is extremely rare....
. In various case series, the long-term risk of ones vision being significantly affected by IIH is reported to lie anywhere between 10 and 25%.
Epidemiology
Median
In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...
age at diagnosis is 30. IIH occurs predominantly in women, especially in the ages 20 to 45, who are four to eight times more likely than men to be affected. Overweight
Overweight
Overweight is generally defined as having more body fat than is optimally healthy. Being overweight is a common condition, especially where food supplies are plentiful and lifestyles are sedentary...
and obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
strongly predispose a person to IIH: women who are more than ten percent over their ideal body weight are thirteen times more likely to develop IIH, and this figure goes up to nineteen times in women who are more than twenty percent over their ideal body weight. In men this relationship also exists, but the increase is only five-fold in those over 20 percent above their ideal body weight.
Despite several reports of IIH in families, there is no known genetic cause for IIH. People from all ethnicities may develop IIH. In children, there is no difference in incidence between males and females.
From national hospital admission databases it appears that the need for neurosurgical intervention for IIH has increased markedly over the period between 1988 and 2002. This has been attributed at least in part to the rising prevalence of obesity, although some of this increase may be explained by the increased popularity of shunting over optic nerve sheath fenestration.
History
The first report of IIH was by the German physician Heinrich QuinckeHeinrich Quincke
Heinrich Irenaeus Quincke was a German internist and surgeon. His main contribution to internal medicine was the introduction of the lumbar puncture for diagnostic and therapeutic purposes...
, who described it in 1893 under the name serous meningitis. The term "pseudotumor cerebri" was introduced in 1904 by his compatriot Max Nonne
Max Nonne
Max Nonne was a German neurologist.Max Nonne was educated at the Gelehrtenschule des Johanneums. He studied in Heidelberg, Freiburg, and Berlin, receiving his doctorate at Hamburg University in 1884...
. Numerous other cases appeared in the literature subsequently; in many cases, the raised intracranial pressure may actually have resulted from underlying conditions. For instance, the otitic hydrocephalus reported by London neurologist Sir Charles Symonds
Charles Symonds
Sir Charles Putnam Symonds KBE CB was an English neurologist.His initial medical training was at Guy's Hospital, followed by specialised training at the National Hospital for Neurology and Neurosurgery...
may have resulted from venous sinus thrombosis caused by middle ear infection
Otitis media
Otitis media is inflammation of the middle ear, or a middle ear infection.It occurs in the area between the tympanic membrane and the inner ear, including a duct known as the eustachian tube. It is one of the two categories of ear inflammation that can underlie what is commonly called an earache,...
. Diagnostic criteria for IIH were developed in 1937 by the Baltimore neurosurgeon Walter Dandy
Walter Dandy
Walter Edward Dandy, M.D. was an American neurosurgeon and scientist. He is considered one of the founding fathers of neurosurgery, along with Victor Horsley and Harvey Cushing...
; Dandy also introduced subtemporal decompressive surgery in the treatment of the condition.
The terms "benign" and "pseudotumor" derive from the fact that increased intracranial pressure may be associated with brain tumor
Brain tumor
A brain tumor is an intracranial solid neoplasm, a tumor within the brain or the central spinal canal.Brain tumors include all tumors inside the cranium or in the central spinal canal...
s. Those patients in whom no tumour was found were therefore diagnosed with "pseudotumor cerebri" (a disease mimicking a brain tumor). The disease was renamed "benign intracranial hypertension" in 1955 to distinguish it from intracranial hypertension due to life-threatening diseases (such as cancer); however, this was also felt to be misleading because any disease that can blind someone should not be thought of as benign, and the name was therefore revised in 1989 to "idiopathic (of no identifiable cause) intracranial hypertension".
Shunt surgery was introduced in 1949; initially, ventriculoperitoneal shunts were used. In 1971, good results were reported with lumboperitoneal shunting. Negative reports on shunting in the 1980s led to a brief period (1988–1993) during which optic nerve fenestration (which had initially been described in an unrelated condition in 1871) was more popular. Since then, shunting is recommended predominantly, with occasional exceptions.