Intention tremor
Intention tremor | |
---|---|
Other names | Cerebellar tremor |
Specialty | Neurology |
Intention tremor is a dyskinetic disorder characterized by a broad, coarse, and low-frequency (below 5 Hz) tremor evident during 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 one's target, a condition known as dysmetria.[1][2] 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.[1]
Several causes have been discovered to date, including damage or degradation of the cerebellum due to
Signs and symptoms
Patients with intention tremors 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.
Causes
Intention tremors are common among individuals with multiple sclerosis (MS). One common symptom of MS is ataxia, a lack of coordinated muscle movement caused by cerebellar lesions characteristic of MS. The disease often destroys physical and cognitive function of individuals.[citation needed] 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.[1][4]
Intention tremors have a variety of other recorded causes, as well, including a variety of
Intention tremor is also known to be associated with
Mechanism
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, instead, seem to be a temporary worsening of a small tremor that is present in every human being. These tremors generally go away with time.[5]
More persistent intention tremors are often caused by damage to certain regions of the brain. Their most common cause is 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, a person may have difficulty executing a fine motor movement, such as attempting to touch one's nose with one's finger. One common way for the cerebellum to become damaged is through the development of cerebellar lesions.[13] 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.[3] 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 MS, damage occurs due to demyelination and neuron death, which again produce cerebellar lesions and an inability for those neurons to transmit signals.[13] Because of this tight association with damage to the cerebellum, intention tremors are often referred to as cerebellar tremors.[1]
Intention tremors can also be caused as a result of damage to the
Diagnosis
A working diagnosis is made from a
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 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.[citation needed] Important historical elements to the diagnosis of intention tremor are:
- Age at onset[citation needed]
- Mode of onset (sudden or gradual)[citation needed]
- Anatomical affected sites
- Rate of progression
- Exacerbating and remitting factors
- Alcohol abuse
- Family history of tremor[15]
- Current medications[12]
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.[1][12]
Management
Treatment of intention tremor is very difficult.[16] The tremor may disappear for a while after a treatment has been administered and then return. This situation is addressed with a different treatment. First, individuals are asked if they use any of the drugs known to cause tremors. If so, they are asked to stop taking the medication, and then are 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, including surgery such as and thalamic deep brain stimulation.[14]
Intention tremors are known to be very difficult to treat with
Physical therapy has had great results in reducing tremors, but usually does not cure them. Relaxation techniques, such as meditation, yoga, hypnosis, and biofeedback, have seen some results with tremors. Wearing wrist weights to weigh down one's hands as they make movements, masking much of the tremor, is a proven home remedy. This is not a treatment, since wearing the weights does not have any lasting effects when they are not on, but they do help the individual cope with the tremor immediately.[12]
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, is surgical intervention. Deep brain stimulation and surgical lesioning of the
Deep brain stimulation treats intention tremors, but does not help related diseases or disorders such as dyssynergia and
Thalamotomy is another surgical treatment where lesions of the thalamic nucleus are created to disrupt the tremor circuit. Thalamotomy has been used to treat many forms of tremors, including those that arise from trauma, MS, stroke, and those whose cause is unknown. This is a very invasive, 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. Thalamotomy is in clinical trials to determine the validity of the treatment of intention tremors with all its high risks.[1][19]
Research directions
Research has focused on finding a pharmacological treatment that is specific for intention tremor. Limited success has been seen in treating it with drugs effective at treating essential tremor.
History
In 1868, French neurologist
References
- ^ a b c d e f g h i j k l [1] Archived 2011-07-21 at the Wayback Machine Seeberger, Lauren. "Cerebellar Tremor-Definition and Treatment." The Colorado Neurological Institute Review. Fall 2005.
- ^ [2] Archived 2016-12-15 at the Wayback Machine National Institute of Neurological Disorders and Stroke. “Tremor Fact Sheet.” Jan 2011. National Institutes of Health.
- ^ PMID 16344298.
- PMID 10908187.
- ^ a b c [3] Hoch, Daniel MD. “Tremor.” Updated 6/15/2010. U.S. National Library of Medicine.
- ^ [4] Archived 2012-03-21 at the Wayback Machine Hagerman, Paul, Hagerman, Randi. “Fragile X-Associated Tremor/Ataxia Syndrome-An Older Face of the Fragile X Gene.” 2007. In Nature Clinical Practice Neurology. Nature Publishing Group.
- ^ [5] Archived 2015-03-06 at the Wayback Machine Eidelberg, David, Pourfar, Michael. "Tremor." 2007. In The Merck Manuals Online Medical Library.
- G. Bernhard Landwehrmeyer, Carl H. Lücking, Freimut D. Juengling. The Journal of Radiology, June 2003
- PMID 16932563.
- ^ [7] “Epidemiological Notes and Reports Elemental Mercury Poisoning in a Household – Ohio 1989.” 1990. In Morbidity and Mortality Weekly Report. Centers for Disease Control and Prevention.
- ^ [8] “Medical Management Guidelines for Acute Chemical Exposures.” 1992. U.S Department of Human Health Services.
- ^ PMID 16392266.
- ^ a b c [9] Archived 2011-05-03 at the Wayback Machine Purves, Dale et al. Neuroscience. Fourth Edition. 2008. Sinauer Associates, Inc.
- ^ PMID 15250610.
- ISBN 978-0-409-95003-8.[page needed]
- ^ Emrich, Lisa (Dec 4, 2012). "Tremor in Multiple Sclerosis: Prevalence, Cause and Treatment". Remedy Health Media, LLC.
- PMID 14570832.
- PMID 21225515.
- S2CID 23216296.
- ^ Clinical trial number NCT00430599 for "The Effect of Levetiracetam (Keppra) on the Treatment of Tremor in Multiple Sclerosis" at ClinicalTrials.gov
- ^ Clinical trial number NCT01100073 for "Kinetic Tremor in Parkinson's Disease: Its Course Under Pramipexole (Mirapexin®) Treatment and Impact on Quality of Life" at ClinicalTrials.gov
- ^ Clinical trial number NCT01104649 for "Efficacy of Riluzole in Hereditary Cerebellar Ataxia" at ClinicalTrials.gov
- PMC 1142241.