A dyskinetic disorder consisting of wide tremor during voluntary movements.
Worsens when a person is moving, particularly when reaching the end of the movement.
The result of dysfunction of the cerebellum in particular of the cerebellar hemispheres.
Intention tremor (IT) is a dyskinetic disorder.
It is characterized by a broad, coarse, and low-frequency (below 5 Hz) tremor evident during deliberate and visually-guided movement.
An intention tremor is usually perpendicular to the direction of movement.
Intention tremor, one often overshoots or undershoots one’s target, a condition known as dysmetria.
It 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.
These tremors can be either unilateral or bilateral.
Several causes including damage or degradation of the cerebellum due to neurodegenerative diseases, trauma, tumor, stroke, or toxicity.
No pharmacological treatment has been established, but some success has been seen using treatments designed for essential tremors.
Patients usually complain of difficulties with activities of daily living, including drinking from a cup, grabbing utensils to eat, and problems with coordination eye to an object or ambulation.
Associated cerebellar signs can include nystagmus, dysmetria, dysdiadochokinesia, hypotonia, proprioception deficits, and gait ataxia.
Intention tremors are common among individuals with multiple sclerosis.
Intention tremors can be a first sign of MS, since loss or deterioration of motor function and sensitivity are often one of the first symptoms of cerebellar lesions.
Intention tremors causes, include a variety of neurological disorders, such as stroke, alcoholism, alcohol withdrawal, peripheral neuropathy, Wilson’s disease, Creutzfeldt–Jakob disease, Guillain–Barré syndrome, and fragile X syndrome, as well as brain tumors, low blood sugar, hyperthyroidism, hypoparathyroidism, insulinoma, normal aging, and traumatic brain injury.
Intention tremor is also known to be associated with infections, such as West Nile virus, rubella, H. influenza, rabies, and varicella.
Poisons can cause intention tremor, including mercury, methyl bromide, and phosphine.
Vitamin deficiencies have been linked to intention tremor, especially deficiency in vitamin E.
Pharmaceuticals such as anti-arrhythmic drugs, anti-epileptic agents, benzodiazepine, cyclosporine, lithium, neuroleptics, and stimulants can cause intention tremor.
Ingesting too much caffeine, cigarettes, and alcohol, along with stress, anxiety, fear, anger, and fatigue can cause intention tremor by negatively affecting the cerebellum, brainstem, or thalamus.
Intention tremors that are 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 a result of temporary worsening of a small tremor that is present in every human being, and tremors generally go away with time.
Persistent intention tremors are often caused by damage and/or degeneration in the cerebellum, the part of the brain responsible for motor coordination, posture, and balance, and especially fine motor movements.
When the cerebellum is damaged, difficulty in executing a fine motor movements occur.
The most common site for cerebellar lesions that lead to intention tremors is the superior cerebellar peduncle,
The superior cerebellar peduncle fibers carry 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 causes this damage to the cerebellum.
The alcohol abuse causes degeneration of the anterior vermis of the cerebellum leading to an inability to process fine motor movements in the individual and the development of intention tremors.
In MS, damage occurs vis demyelination and neuron death, which 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: these structures are involved in the transmission of information between the cerebellum and the cerebral cortex, and 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 upon which it is trying to act is compromised, resulting in the development of a tremor.
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 determine 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, tumors, hemorrhages, demyelination, or other damage may be causing dysfunction of the cerebellum and correspondingly the intention tremor.
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.
With intention tremors has coarse 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, in a supine position, places one heel on top of the opposite knee and is then instructed to slide the heel down the shin to the ankle while being monitored for coarse and irregular side-to-side movement as the heel approaches the ankle.
Secondary symptoms commonly observed are dysarthria, nystagmus, gait problems and postural tremor or titubation.
A postural tremor may also accompany intention tremors.
Treatment of intention tremor is very difficult.
The tremor may disappear for a while after a treatment has been administered and then return.
First, individuals are asked if they use any of the drugs known to cause tremors, and are asked to stop taking the medication.
If the tremor persists, treatment that follows may include drug therapy, lifestyle changes, and more invasive forms of treatment, including surgery such as and thalamic deep brain stimulation.
Intention tremors are known to be very difficult to treat with pharmacotherapy and drugs.
Drugs: Isoniazid, buspirone hydrochloride, glutethimide, carbamazepine, clonazepam, 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.
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, is an effective treatment of intention tremors.
Physical therapy can reducing tremors, but usually does not cure them.
Relaxation techniques, such as meditation, yoga, hypnosis, and biofeedback, have seen some results with tremors.
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.
In the case of an intention tremor, the thalamic nuclear region is targeted for treatment.
This form of treatment causes reversible changes and does not cause any permanent lesions.
Reduction in tremor amplitude is almost guaranteed and sometimes resolved.
Thalamotomy has been used to treat many forms of tremors.
Thalamotomy is a high-risk treatment with many negative effects, such as MS worsening, cognitive dysfunction, worsening of dysarthria, and dysphagia.
Immediate positive effects are seen in individuals treated with a thalamotomy procedure, but the tremor often comes back, so is not a complete treatment.
Differential diagnosis include medical drugs, alcohol intoxication, multiple sclerosis, stroke and tumors