Intention tremor
Encyclopedia
Intention tremor, also known as cerebellar tremor, is a dyskinetic
disorder characterized by a broad, course, and low frequency (below 5 Hz) tremor
. The amplitude of an intention tremor increases as an extremity approaches the endpoint of deliberate and visually guided movement (hence the name intention tremor). An intention tremor is usually perpendicular to the direction of movement. When experiencing an intention tremor, one often overshoots or undershoots their target, a condition known as dysmetria
. Intention tremor is the result of dysfunction of the cerebellum
, particularly on the same side as the tremor in the lateral zone, which controls visually guided movements. Depending on the location of cerebellar damage, these tremors can be either unilateral or bilateral.
A variety of causes have been discovered to date, including damage or degradation of the cerebellum due to neurodegenerative diseases, trauma
, tumor
, stroke
, or toxicity. There is currently no established pharmacological treatment, however, some success has been seen using treatments designed for essential tremor
s.
. One common symptom of multiple sclerosis is ataxia
. This is a lack of coordinated muscle movement is caused by cerebellar lesions characteristic of multiple sclerosis. The disease often destroys physical and cognitive function of individuals. Intention tremors can be a first sign of multiple sclerosis, since loss of deteriorated motor function and sensitivity are often one of the first symptoms of cerebellar lesions.
Intention tremors have a variety of other recorded causes as well. These include a variety of neurological disorders, such as stroke
, alcoholism
, alcohol withdrawal
, peripheral neuropathy
, Wilson's disease
, Creutzfeldt-Jacob disease, Guillain–Barré syndrome and fragile X syndrome
, as well as brain tumor
s, low blood sugar
, hyperthyroidism
, hypoparathyroidism
, insulinoma
, normal aging, and traumatic brain injury
. Holmes tremor
, a rubral or midbrain tremor, is another form of tremor that includes intention tremors, among other symptoms. This disease affects the proximal muscles of the head, shoulders, and neck. Tremors of this disease occur at frequencies of 2–4 Hz or more. Intention tremor is also known to be associated with infection
s, West Nile Virus
, rubella
, H. influenza
, rabies
, and varicella. A variety of poisons have been shown to cause intention tremor, including mercury
, methyl bromide, and phosphine
. In addition, vitamin
deficiencies have been linked to intention tremor, especially deficiency in vitamin E
. Pharmacological agents such as anti-arrhythmic drugs, anti-epileptic
agents, benzodiazepine
, cyclosporine, lithium
, neuroleptics, and stimulants have been known to cause intention tremor. Some ordinary activities including ingesting too much caffeine
, cigarette
s, and alcohol
, along with stress, anxiety, fear, anger and fatigue
have also been shown to cause intention tremor by negatively effecting the cerebellum, brainstem, or thalamus, as discussed in mechanisms.
Intention tremors caused by normal, everyday activities, such as stress, anxiety, fear, anger, caffeine, and fatigue do not seem to result from damage to any part of the brain. These tremors instead seem to be a temporary worsening of a small tremor that is present in every human being. These tremors go away with time.
More permanent intention tremors are caused by damage to certain regions of the brain. The most common cause of intention tremors is damage to the cerebellum
. The cerebellum is a part of the brain responsible for motor coordination, posture and balance. It is responsible for fine motor movements. When the cerebellum is damaged, a person has difficulty executing a fine motor movement, such as attempting to touch one's nose with one's finger. One of the most common ways for the cerebellum to become damaged is through the development of cerebellar lesion
s. The most common site for cerebellar lesions that lead to intention tremors has been reported to be the superior cerebellar peduncle, through which all fibers carrying information to the midbrain pass, and the dentate nucleus
, which is also responsible for linking the cerebellum to the rest of the brain. Alcohol abuse is one typical cause of this damage to the cerebellum. The alcohol abuse causes degeneration of the anterior vermis
of the cerebellum. This leads to an inability to process fine motor movements in the individual and the development of intention tremors. In Multiple Sclerosis, damage occurs due to demyelination
and neuron
death, which again produces cerebellar lesions and an inability for those neurons to transmit signals. Because of this tight association with damage to the cerebellum, intention tremors are often referred to as cerebellar tremors.
Intention tremors can also be caused as a result of damage to the brainstem or thalamus
. Both of these structures are involved in the transmission of information between the cerebellum and the cerebral cortex
, as well as between the cerebellum and the spinal cord
, and then on to the motor neurons. When these become damaged, the relay system between the cerebellum and the muscle
on which it is try to act upon is compromised, resulting in the development of a tremor.
and evaluation. Parts of a complete examination include a physical examination, MRI
, patient history, and electrophysiological
and accelerometric
studies. A diagnosis of solely intention tremor can only be made if the tremor is of low frequency (below 5 Hz) and without the presence of any resting tremors. Electrophysiological studies can be useful in determining frequency of the tremor, and accelerometric studies quantify tremor amplitude. MRI is used to locate damage to and degradation of the cerebellum that may be causing the intention tremor. Focal lesions such as neoplasms, tumor
s, hemorrhages
, demyelination
, or other damage may be causing dysfunction of the cerebellum and correspondingly the intention tremor.
Physical tests are an easy way to determine the severity of the intention tremor and impairment of physical activity. Common tests that are used to assess intention tremor are the finger-to-nose and heel-to-shin tests. In a finger-to-nose test a physician has the individual touch their nose with their finger while monitoring for irregularity in timing and control of the movement. An individual with intention tremors will have course, side-to-side movements that increase in severity as the finger approaches the nose. Similarly, the heel-to-shin test evaluates intention tremors of the lower extremities. In such a test, the individual places their heel on the top of their opposite knee and is then instructed to slide their heel down their shin to their ankle while being monitored for course and irregular side to side movement as the heel approaches the ankle.
Important historical elements to the diagnosis of intention tremor are:
Secondary symptoms commonly observed are dysarthria
(a speech disorder
characterized by poor articulation and slurred speech), nystagmus
(rapid involuntary eye movement, especially rolling of the eyes), gait
problems (abnormality in walking
), and postural tremor or titubation (to-and-fro movements of the neck and trunk). A postural tremor may also accompany intention tremors.
.
Intention tremors are notoriously known to be very difficult to treat with pharmacotherapy
and drug
s. Although there is no established pharmacological treatment for an intention tremor, several drugs have been found to have positive effects on intention tremors and are used as treatment by many health professionals. Isoniazid
, buspirone hydrochloride, glutethimide
, carbamazepine
, clonazepam
, buspirone
, topiramate
, zofran, propranolol and primidone
have all seen moderate results in treating intention tremor and can be prescribed treatments. Isoniazid
inhibits γ-aminobutyric acid
-aminotransferase, which the first step in enzymatic breakdown of GABA
, thus increasing GABA, the major inhibitory neurotransmitter
in the central nervous system. This causes a reduction in cerebellar ataxia
s. Another neurotransmitter targeted by drugs that has been found to alleviate intention tremors is serotonin
. The agonist buspirone hydrochloride, which decreases serotonin's function in the central nervous system, has been viewed as an effective treatment of intention tremors.
There are also alternative treatments available. Cannabis
has offered as an effective treatment for individuals with tremors, but the inclination to find conclusive scientific data on such a treatment has not existed in the medical community. Equally, it should be pertinent to remember there has been no research conducted of any kind on the potential benefits of therapeutic Cannabis
treatments, not merely a lack of positive research, something that may well be attributed to political
or social
constraints on the exploration of such a therapy. Also, physical therapy
has had great results in reducing tremors, but usually does not cure the tremors. Relaxation techniques, such as meditation
, yoga
, hypnosis
, and biofeedback
, are other alternative treatments that have seen some results with tremors. Wearing wrist weights which will weigh down one's hands as they make movements, masking much of the tremor, is a proven home remedy. This is not a true treatment, since wearing the weights does not have any lasting effects when they are not on, however they do help the individual cope with the tremor immediately.
A more radical treatment that is used in individuals who do not respond to drug therapy, physical therapy, or any other treatment listed above, with moderate to severe intention tremors, would be surgical intervention. Deep brain stimulation
and surgical lesioning of the thalamic nuclei has been found to be an effective long-term treatment with intention tremors. Deep brain stimulation, treats intention tremors but does not help related diseases or disorders such as dyssynergia and dysmetria
. Deep brain stimulation involves the implantation of a device called a brain pacemaker
, shown in the picture above. This medical device sends electrical impulses to specific parts of the brain, changing brain activity in a controlled manner. In the case of an intention tremor, the thalamic nuclei is the region of the brain targeted for treatment. This form of treatment causes reversible changes and does not cause any permanent lesions. Since it is reversible, deep brain stimulation is considered fairly safe, and reduction in tremor amplitude is almost guaranteed and sometimes it is even resolved. Some individuals with multiple sclerosis have seen sustained benefits in MS progress. Thalamotomy
is another surgical treatment where lesions of the thalamus nucleus are created to disrupt the tremor circuit. Thalamotomy has been used to treat many different forms of tremors, including tremors that arise from trauma, multiple sclerosis, stroke, and those whose cause it unknown. This is a very invasive, high-risk treatment with many negative effects, such as multiple sclerosis worsening, cognitive dysfunction, worsening of dysarthria
, and dysphagia
. Immediate positive effects are seen in individuals treated with a thalamotomy procedure. However, the tremor often comes back after some time, thus it is not a complete treatment. Thalamotomy is currently in clinical trials to determine the validity of the treatment of intention tremors with all its high risks.
, and pramipexole
, used to treat resting tremor, have recently been completed to establish their effectiveness in treating kinetic tremor. A clinical trial for riluzole
, typically used to treat amyotrophic lateral sclerosis
, is currently underway at the Sapienza University of Rome to evaluate its effectiveness of treating cerebellar ataxia
and kinetic tremor.
first characterized the distinction between MS and its resulting intention tremor from resting tremor, characteristic of Parkinson’s disease. Intention tremor became known as part of Charcot's triad which, along with nystagmus and scanning speech, act as strong indications of MS.
Dyskinesia
Dyskinesia is a movement disorder which consists of effects including diminished voluntary movements and the presence of involuntary movements, similar to tics or choreia. Dyskinesia can be anything from a slight tremor of the hands to uncontrollable movement of, most commonly, the upper body but...
disorder characterized by a broad, course, and low frequency (below 5 Hz) tremor
Tremor
A tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving to-and-fro movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, face, head, vocal folds, trunk, and legs. Most tremors occur in the...
. The amplitude of an intention tremor increases as an extremity approaches the endpoint of deliberate and visually guided movement (hence the name intention tremor). An intention tremor is usually perpendicular to the direction of movement. When experiencing an intention tremor, one often overshoots or undershoots their target, a condition known as dysmetria
Dysmetria
Dysmetria refers to a lack of coordination of movement typified by the undershoot or overshoot of intended position with the hand, arm, leg, or eye...
. Intention tremor is the result of dysfunction of the cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
, particularly on the same side as the tremor in the lateral zone, which controls visually guided movements. Depending on the location of cerebellar damage, these tremors can be either unilateral or bilateral.
A variety of causes have been discovered to date, including damage or degradation of the cerebellum due to neurodegenerative diseases, trauma
Trauma (medicine)
Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
, tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
, stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
, or toxicity. There is currently no established pharmacological treatment, however, some success has been seen using treatments designed for essential tremor
Essential tremor
Essential tremor is a slowly progressive neurological disorder whose most recognizable feature is a tremor of the arms that is apparent during voluntary movements such as eating and writing...
s.
Causes
Intention tremors are common among individuals with multiple sclerosisMultiple sclerosis
Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...
. One common symptom of multiple sclerosis is ataxia
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...
. This is a lack of coordinated muscle movement is caused by cerebellar lesions characteristic of multiple sclerosis. The disease often destroys physical and cognitive function of individuals. Intention tremors can be a first sign of multiple sclerosis, since loss of deteriorated motor function and sensitivity are often one of the first symptoms of cerebellar lesions.
Intention tremors have a variety of other recorded causes as well. These include a variety of neurological disorders, such as stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
, alcoholism
Alcoholism
Alcoholism is a broad term for problems with alcohol, and is generally used to mean compulsive and uncontrolled consumption of alcoholic beverages, usually to the detriment of the drinker's health, personal relationships, and social standing...
, alcohol withdrawal
Alcohol withdrawal syndrome
-Protracted withdrawal:A protracted alcohol withdrawal syndrome occurs in many alcoholics where withdrawal symptoms continue beyond the acute withdrawal stage but usually at a subacute level of intensity and gradually decreasing with severity over time. This syndrome is also sometimes referred to...
, peripheral neuropathy
Peripheral neuropathy
Peripheral neuropathy is the term for damage to nerves of the peripheral nervous system, which may be caused either by diseases of or trauma to the nerve or the side-effects of systemic illness....
, Wilson's disease
Wilson's disease
Wilson's disease or hepatolenticular degeneration is an autosomal recessive genetic disorder in which copper accumulates in tissues; this manifests as neurological or psychiatric symptoms and liver disease...
, Creutzfeldt-Jacob disease, Guillain–Barré syndrome and fragile X syndrome
Fragile X syndrome
Fragile X syndrome , Martin–Bell syndrome, or Escalante's syndrome , is a genetic syndrome that is the most commonly known single-gene cause of autism and the most common inherited cause of intellectual disability...
, as well as 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, low blood sugar
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...
, hyperthyroidism
Hyperthyroidism
Hyperthyroidism is the term for overactive tissue within the thyroid gland causing an overproduction of thyroid hormones . Hyperthyroidism is thus a cause of thyrotoxicosis, the clinical condition of increased thyroid hormones in the blood. Hyperthyroidism and thyrotoxicosis are not synonymous...
, hypoparathyroidism
Hypoparathyroidism
Hypoparathyroidism is decreased function of the parathyroid glands with under production of parathyroid hormone. This can lead to low levels of calcium in the blood, often causing cramping and twitching of muscles or tetany , and several other symptoms...
, insulinoma
Insulinoma
An insulinoma is a tumour of the pancreas that is derived from beta cells and secretes insulin.Beta cells secrete insulin in response to increases in blood glucose. The resulting increase in insulin acts to lower blood glucose back to normal levels at which point further secretion of insulin is...
, normal aging, and traumatic brain injury
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
. Holmes tremor
Holmes tremor
Holmes' tremor is a combination of rest, action, and postural tremors. It is a "wing-beating" type of tremor that is caused by cerebellar damage. It may arise from various underlying structural disorders including multiple sclerosis, stroke, or tumors. So far, few studies on Holmes' tremor...
, a rubral or midbrain tremor, is another form of tremor that includes intention tremors, among other symptoms. This disease affects the proximal muscles of the head, shoulders, and neck. Tremors of this disease occur at frequencies of 2–4 Hz or more. Intention tremor is also known to be associated with infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
s, West Nile Virus
West Nile virus
West Nile virus is a virus of the family Flaviviridae. Part of the Japanese encephalitis antigenic complex of viruses, it is found in both tropical and temperate regions. It mainly infects birds, but is known to infect humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels, domestic...
, rubella
Rubella
Rubella, commonly known as German measles, is a disease caused by the rubella virus. The name "rubella" is derived from the Latin, meaning little red. Rubella is also known as German measles because the disease was first described by German physicians in the mid-eighteenth century. This disease is...
, H. influenza
Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
, rabies
Rabies
Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...
, and varicella. A variety of poisons have been shown to cause intention tremor, including mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
, methyl bromide, and phosphine
Phosphine
Phosphine is the compound with the chemical formula PH3. It is a colorless, flammable, toxic gas. Pure phosphine is odourless, but technical grade samples have a highly unpleasant odor like garlic or rotting fish, due to the presence of substituted phosphine and diphosphine...
. In addition, vitamin
Vitamin
A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
deficiencies have been linked to intention tremor, especially deficiency in vitamin E
Vitamin E
Vitamin E is used to refer to a group of fat-soluble compounds that include both tocopherols and tocotrienols. There are many different forms of vitamin E, of which γ-tocopherol is the most common in the North American diet. γ-Tocopherol can be found in corn oil, soybean oil, margarine and dressings...
. Pharmacological agents such as anti-arrhythmic drugs, anti-epileptic
Anticonvulsant
The anticonvulsants are a diverse group of pharmaceuticals used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder, since many seem to act as mood stabilizers, and in the treatment of neuropathic pain. The goal of an...
agents, benzodiazepine
Benzodiazepine
A benzodiazepine is a psychoactive drug whose core chemical structure is the fusion of a benzene ring and a diazepine ring...
, cyclosporine, lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
, neuroleptics, and stimulants have been known to cause intention tremor. Some ordinary activities including ingesting too much caffeine
Caffeine
Caffeine is a bitter, white crystalline xanthine alkaloid that acts as a stimulant drug. Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants...
, cigarette
Cigarette
A cigarette is a small roll of finely cut tobacco leaves wrapped in a cylinder of thin paper for smoking. The cigarette is ignited at one end and allowed to smoulder; its smoke is inhaled from the other end, which is held in or to the mouth and in some cases a cigarette holder may be used as well...
s, and alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....
, along with stress, anxiety, fear, anger and fatigue
have also been shown to cause intention tremor by negatively effecting the cerebellum, brainstem, or thalamus, as discussed in mechanisms.
Mechanism
More permanent intention tremors are caused by damage to certain regions of the brain. The most common cause of intention tremors is damage to the cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
. The cerebellum is a part of the brain responsible for motor coordination, posture and balance. It is responsible for fine motor movements. When the cerebellum is damaged, a person has difficulty executing a fine motor movement, such as attempting to touch one's nose with one's finger. One of the most common ways for the cerebellum to become damaged is through the development of cerebellar lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
s. The most common site for cerebellar lesions that lead to intention tremors has been reported to be the superior cerebellar peduncle, through which all fibers carrying information to the midbrain pass, and the dentate nucleus
Dentate nucleus
The dentate nucleus is located within the deep white matter of each cerebellar hemisphere, and it is the largest single structure linking the cerebellum to the rest of the brain. It is the largest and most lateral, or farthest from the midline, of the four pairs of deep cerebellar nuclei, the...
, which is also responsible for linking the cerebellum to the rest of the brain. Alcohol abuse is one typical cause of this damage to the cerebellum. The alcohol abuse causes degeneration of the anterior vermis
Cerebellar vermis
The cerebellar vermis is located in the medial, cortico-nuclear zone of the cerebellum, residing in the posterior fossa of the cranium. The primary fissure in the vermis curves ventrolaterally to the superior surface of the cerebellum, dividing it into anterior and posterior lobes....
of the cerebellum. This leads to an inability to process fine motor movements in the individual and the development of intention tremors. In Multiple Sclerosis, damage occurs due to demyelination
Demyelinating disease
A demyelinating disease is any disease of the nervous system in which the myelin sheath of neurons is damaged. This impairs the conduction of signals in the affected nerves, causing impairment in sensation, movement, cognition, or other functions depending on which nerves are involved.The term...
and neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
death, which again produces cerebellar lesions and an inability for those neurons to transmit signals. Because of this tight association with damage to the cerebellum, intention tremors are often referred to as cerebellar tremors.
Intention tremors can also be caused as a result of damage to the brainstem or thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
. Both of these structures are involved in the transmission of information between the cerebellum and the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
, as well as between the cerebellum and the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
, and then on to the motor neurons. When these become damaged, the relay system between the cerebellum and the muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
on which it is try to act upon is compromised, resulting in the development of a tremor.
Diagnosis
A working diagnosis is made from a neurological examinationNeurological examination
A neurological examination is the assessment of sensory neuron and motor responses, especially reflexes, to determine whether the nervous system is impaired...
and evaluation. Parts of a complete examination include a physical examination, MRI
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...
, patient history, and electrophysiological
Electrophysiology
Electrophysiology is the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart...
and accelerometric
Accelerometer
An accelerometer is a device that measures proper acceleration, also called the four-acceleration. This is not necessarily the same as the coordinate acceleration , but is rather the type of acceleration associated with the phenomenon of weight experienced by a test mass that resides in the frame...
studies. A diagnosis of solely intention tremor can only be made if the tremor is of low frequency (below 5 Hz) and without the presence of any resting tremors. Electrophysiological studies can be useful in determining frequency of the tremor, and accelerometric studies quantify tremor amplitude. MRI is used to locate damage to and degradation of the cerebellum that may be causing the intention tremor. Focal lesions such as neoplasms, tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s, hemorrhages
Bleeding
Bleeding, technically known as hemorrhaging or haemorrhaging is the loss of blood or blood escape from the circulatory system...
, demyelination
Demyelinating disease
A demyelinating disease is any disease of the nervous system in which the myelin sheath of neurons is damaged. This impairs the conduction of signals in the affected nerves, causing impairment in sensation, movement, cognition, or other functions depending on which nerves are involved.The term...
, or other damage may be causing dysfunction of the cerebellum and correspondingly the intention tremor.
Physical tests are an easy way to determine the severity of the intention tremor and impairment of physical activity. Common tests that are used to assess intention tremor are the finger-to-nose and heel-to-shin tests. In a finger-to-nose test a physician has the individual touch their nose with their finger while monitoring for irregularity in timing and control of the movement. An individual with intention tremors will have course, side-to-side movements that increase in severity as the finger approaches the nose. Similarly, the heel-to-shin test evaluates intention tremors of the lower extremities. In such a test, the individual places their heel on the top of their opposite knee and is then instructed to slide their heel down their shin to their ankle while being monitored for course and irregular side to side movement as the heel approaches the ankle.
Important historical elements to the diagnosis of intention tremor are:
- age of onset
- mode of onset (sudden or gradual)
- anatomical affected sites
- rate of progression
- exacerbating and remitting factors
- alcohol abuse
- family history of tremor
- current medications
Secondary symptoms commonly observed are dysarthria
Dysarthria
Dysarthria is a motor speech disorder resulting from neurological injury of the motor component of the motor-speech system and is characterized by poor articulation of phonemes...
(a speech disorder
Speech disorder
Speech disorders or speech impediments are a type of communication disorders where 'normal' speech is disrupted. This can mean stuttering, lisps, etc. Someone who is unable to speak due to a speech disorder is considered mute.-Classification:...
characterized by poor articulation and slurred speech), nystagmus
Nystagmus
Nystagmus is a condition of involuntary eye movement, acquired in infancy or later in life, that may result in reduced or limited vision.There are two key forms of Nystagmus: pathological and physiological, with variations within each type. Nystagmus may be caused by congenital disorders,...
(rapid involuntary eye movement, especially rolling of the eyes), gait
Gait
Gait is the pattern of movement of the limbs of animals, including humans, during locomotion over a solid substrate. Most animals use a variety of gaits, selecting gait based on speed, terrain, the need to maneuver, and energetic efficiency...
problems (abnormality in walking
Walking
Walking is one of the main gaits of locomotion among legged animals, and is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults over the stiff limb or limbs with each step...
), and postural tremor or titubation (to-and-fro movements of the neck and trunk). A postural tremor may also accompany intention tremors.
Management
It is very difficult to treat an intention tremor. The tremor may disappear for a while after a treatment has been administered, and then return after some time. This situation must be addressed with a different type of treatment. First, individuals will be asked if they use any of the drugs known to cause tremors. If so, they are asked to stop taking the medication and then evaluated after some time to determine if the medication was related to the onset of the tremor. If the tremor persists, treatment that follows may include drug therapy, lifestyle changes, and more invasive forms of treatment, such as surgery and thalamic deep brain stimulationDeep brain stimulation
Deep brain stimulation is a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain...
.
Intention tremors are notoriously known to be very difficult to treat with pharmacotherapy
Pharmacotherapy
Pharmacotherapy is the treatment of disease through the administration of drugs. As such, it is considered part of the larger category of therapy....
and drug
Drug
A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
s. Although there is no established pharmacological treatment for an intention tremor, several drugs have been found to have positive effects on intention tremors and are used as treatment by many health professionals. Isoniazid
Isoniazid
Isoniazid , also known as isonicotinylhydrazine , is an organic compound that is the first-line antituberculosis medication in prevention and treatment. It was first discovered in 1912, and later in 1951 it was found to be effective against tuberculosis by inhibiting its mycolic acid...
, buspirone hydrochloride, glutethimide
Glutethimide
Glutethimide is a hypnotic sedative that was introduced in 1954 as a safe alternative to barbiturates to treat insomnia. Before long, however, it had become clear that glutethimide was just as likely to cause addiction and caused similarly severe withdrawal symptoms...
, carbamazepine
Carbamazepine
Carbamazepine is an anticonvulsant and mood-stabilizing drug used primarily in the treatment of epilepsy and bipolar disorder, as well as trigeminal neuralgia...
, clonazepam
Clonazepam
Clonazepamis a benzodiazepine drug having anxiolytic, anticonvulsant, muscle relaxant, and hypnotic properties. It is marketed by Roche under the trade name Klonopin in the United States and Rivotril in Australia, Brazil, Canada and Europe...
, buspirone
Buspirone
Buspirone is an anxiolytic psychoactive drug of the azapirone chemical class, and is primarily used to treat generalized anxiety disorder Bristol-Myers Squibb gained FDA approval of buspirone in 1986 for treatment of GAD...
, 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...
, zofran, propranolol and primidone
Primidone
Primidone is an anticonvulsant of the pyrimidinedione class, the active metabolites of which, phenobarbital and phenylethylmalonamide , are also anticonvulsants...
have all seen moderate results in treating intention tremor and can be prescribed treatments. Isoniazid
Isoniazid
Isoniazid , also known as isonicotinylhydrazine , is an organic compound that is the first-line antituberculosis medication in prevention and treatment. It was first discovered in 1912, and later in 1951 it was found to be effective against tuberculosis by inhibiting its mycolic acid...
inhibits γ-aminobutyric acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
-aminotransferase, which the first step in enzymatic breakdown of GABA
Gabâ
Gabâ or gabaa, for the people in many parts of the Philippines), is the concept of a non-human and non-divine, imminent retribution. A sort of negative karma, it is generally seen as an evil effect on a person because of their wrongdoings or transgressions...
, thus increasing GABA, the major inhibitory neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
in the central nervous system. This causes a reduction in cerebellar ataxia
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...
s. Another neurotransmitter targeted by drugs that has been found to alleviate intention tremors is serotonin
Serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...
. The agonist buspirone hydrochloride, which decreases serotonin's function in the central nervous system, has been viewed as an effective treatment of intention tremors.
There are also alternative treatments available. Cannabis
Cannabis
Cannabis is a genus of flowering plants that includes three putative species, Cannabis sativa, Cannabis indica, and Cannabis ruderalis. These three taxa are indigenous to Central Asia, and South Asia. Cannabis has long been used for fibre , for seed and seed oils, for medicinal purposes, and as a...
has offered as an effective treatment for individuals with tremors, but the inclination to find conclusive scientific data on such a treatment has not existed in the medical community. Equally, it should be pertinent to remember there has been no research conducted of any kind on the potential benefits of therapeutic Cannabis
Cannabis
Cannabis is a genus of flowering plants that includes three putative species, Cannabis sativa, Cannabis indica, and Cannabis ruderalis. These three taxa are indigenous to Central Asia, and South Asia. Cannabis has long been used for fibre , for seed and seed oils, for medicinal purposes, and as a...
treatments, not merely a lack of positive research, something that may well be attributed to political
War on Drugs
The War on Drugs is a campaign of prohibition and foreign military aid and military intervention being undertaken by the United States government, with the assistance of participating countries, intended to both define and reduce the illegal drug trade...
or social
The Rhetoric of Drugs
The Rhetoric of Drugs, Rhétorique de la drogue in the original French title, is a 1990 work by French philosopher Jacques Derrida. Derrida, interviewed, discusses the concept of "drug", and says that "Already one must conclude that the concept of drug is a non-scientific concept, that it is...
constraints on the exploration of such a therapy. Also, physical therapy
Physical therapy
Physical therapy , often abbreviated PT, is a health care profession. Physical therapy is concerned with identifying and maximizing quality of life and movement potential within the spheres of promotion, prevention, diagnosis, treatment/intervention,and rehabilitation...
has had great results in reducing tremors, but usually does not cure the tremors. Relaxation techniques, such as meditation
Meditation
Meditation is any form of a family of practices in which practitioners train their minds or self-induce a mode of consciousness to realize some benefit....
, yoga
Yoga
Yoga is a physical, mental, and spiritual discipline, originating in ancient India. The goal of yoga, or of the person practicing yoga, is the attainment of a state of perfect spiritual insight and tranquility while meditating on Supersoul...
, hypnosis
Hypnosis
Hypnosis is "a trance state characterized by extreme suggestibility, relaxation and heightened imagination."It is a mental state or imaginative role-enactment . It is usually induced by a procedure known as a hypnotic induction, which is commonly composed of a long series of preliminary...
, and biofeedback
Biofeedback
Biofeedback is the process of becoming aware of various physiological functions using instruments that provide information on the activity of those same systems, with a goal of being able to manipulate them at will...
, are other alternative treatments that have seen some results with tremors. Wearing wrist weights which will weigh down one's hands as they make movements, masking much of the tremor, is a proven home remedy. This is not a true treatment, since wearing the weights does not have any lasting effects when they are not on, however they do help the individual cope with the tremor immediately.
A more radical treatment that is used in individuals who do not respond to drug therapy, physical therapy, or any other treatment listed above, with moderate to severe intention tremors, would be surgical intervention. Deep brain stimulation
Deep brain stimulation
Deep brain stimulation is a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain...
and surgical lesioning of the thalamic nuclei has been found to be an effective long-term treatment with intention tremors. Deep brain stimulation, treats intention tremors but does not help related diseases or disorders such as dyssynergia and dysmetria
Dysmetria
Dysmetria refers to a lack of coordination of movement typified by the undershoot or overshoot of intended position with the hand, arm, leg, or eye...
. Deep brain stimulation involves the implantation of a device called a brain pacemaker
Brain pacemaker
"Brain pacemakers" are used to treat people who suffer from epilepsy, Parkinson's disease, major depression and other diseases. The pacemaker is a medical device that is implanted into the brain to send electrical signals into the tissue. Depending on the area of the brain that is targeted, the...
, shown in the picture above. This medical device sends electrical impulses to specific parts of the brain, changing brain activity in a controlled manner. In the case of an intention tremor, the thalamic nuclei is the region of the brain targeted for treatment. This form of treatment causes reversible changes and does not cause any permanent lesions. Since it is reversible, deep brain stimulation is considered fairly safe, and reduction in tremor amplitude is almost guaranteed and sometimes it is even resolved. Some individuals with multiple sclerosis have seen sustained benefits in MS progress. Thalamotomy
Thalamotomy
First introduced in the 1950s, thalamotomy is an invasive procedure, primarily effective for tremors such as those associated with Parkinson's Disease , where a selected portion of the thalamus is surgically destroyed...
is another surgical treatment where lesions of the thalamus nucleus are created to disrupt the tremor circuit. Thalamotomy has been used to treat many different forms of tremors, including tremors that arise from trauma, multiple sclerosis, stroke, and those whose cause it unknown. This is a very invasive, high-risk treatment with many negative effects, such as multiple sclerosis worsening, cognitive dysfunction, worsening of dysarthria
Dysarthria
Dysarthria is a motor speech disorder resulting from neurological injury of the motor component of the motor-speech system and is characterized by poor articulation of phonemes...
, and dysphagia
Dysphagia
Dysphagia is the medical term for the symptom of difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, the term is sometimes used as a condition in its own right. Sufferers are sometimes unaware of their dysphagia....
. Immediate positive effects are seen in individuals treated with a thalamotomy procedure. However, the tremor often comes back after some time, thus it is not a complete treatment. Thalamotomy is currently in clinical trials to determine the validity of the treatment of intention tremors with all its high risks.
Research directions
Current research has focused on finding a pharmacological treatment that is specific for intention tremor. Currently, limited success has been seen in treating intention tremor with drugs effective at treating essential tremor. Clinical trials of levetiracetam, typically used to treat epilepsyEpilepsy
Epilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
, and pramipexole
Pramipexole
Pramipexole is a non-ergoline dopamine agonist indicated for treating early-stage Parkinson's disease and restless legs syndrome...
, used to treat resting tremor, have recently been completed to establish their effectiveness in treating kinetic tremor. A clinical trial for riluzole
Riluzole
Riluzole is a drug used to treat amyotrophic lateral sclerosis. It delays the onset of ventilator-dependence or tracheostomy in selected patients and may increase survival by approximately 3–5 months....
, typically used to treat amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis , also referred to as Lou Gehrig's disease, is a form of motor neuron disease caused by the degeneration of upper and lower neurons, located in the ventral horn of the spinal cord and the cortical neurons that provide their efferent input...
, is currently underway at the Sapienza University of Rome to evaluate its effectiveness of treating cerebellar ataxia
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...
and kinetic tremor.
History
In 1868, French neurologist Jean-Martin CharcotJean-Martin Charcot
Jean-Martin Charcot was a French neurologist and professor of anatomical pathology. He is known as "the founder of modern neurology" and is "associated with at least 15 medical eponyms", including Charcot-Marie-Tooth disease and amyotrophic lateral sclerosis...
first characterized the distinction between MS and its resulting intention tremor from resting tremor, characteristic of Parkinson’s disease. Intention tremor became known as part of Charcot's triad which, along with nystagmus and scanning speech, act as strong indications of MS.