Intention tremor, also known as cerebellar tremor, is a dyskenetic disorder characterized by a broad, course, and low frequency (below 5 Hz) tremor of increasing amplitude as an extremity approaches the endpoint of deliberate, visually guided movement (hence the name intention tremor). Intention tremor is usually perpendicular to the direction of movement and one often overshoot or undershoot their target known as dysmetria.[1] [2] It is the result of dysfunction of the cerebellum in particular on ipsilateral side of the lateral zone. Depending on the location of cerebellar damage, intention tremor can be either unilateral or bilateral. [1]
A variety of causes including: damage or degradation of the cerebellum due to multiple sclerosis, degenerative diseases, trauma, tumor, stroke, or toxicity can cause intention tremors. There is currently no established pharmacological treatment specifically for intention tremors, however, some success has been seen using treatments designed for essential tremor. [3] [1] Intention tremors are often seen in conjunction with other cerebellar dysfunctions such as dysarthria (speech problems), nystagmus (abnormal eye movements) and unsteady gait. Postural tremor may also accompany intention tremor. [1]
History
editIn 1868, French neurologist Jean-Martin Charcot first characterized the distinction between MS and its resulting intention tremor from resting tremor, found in Parkinson’s disease. Intention tremor became known as part of Charcot's triad along with nystagmus and scanning speech, other strong indications of MS. [4]
Diagnosis
editA working diagnosis is made from a neurological examination and evaluation including using 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 resting tremor.[1] Electrophysiological studies can be useful in determining frequency of the tremor and accelerometric studies quantify tremor amplitude. MRI is used to locate damage and degradation to 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. [5]
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 tremors are the finger-to-nose and heel-to-shin tests. Finger-to-nose test is where the physician will have the patient touch their nose with their finger while monitoring for irregularity in timing and control. A patient with intention tremor will have course, side-to-side movement that increases as the finger approaches the nose. Similarly, the heel-to-shin test evaluates intention tremor of the lower extremities. In such a test, the patient places their heel on the top of their opposite knee and is then instructed to slide their heel down their shin, to their ankle as they are 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 of gradual)
- anatomical affected sites
- rate of progression
- exacerbating and remitting factors
- alcohol abuse
- family history of tremor. [6]
Current medications are also an important factor in diagnosis as, many different pharmacological agents can cause tremor. [7]
Current and Future Research
editCurrent research has focused on finding a pharmacological treatment that is specific to intention tremor. Currently, limited success has been seen in treating intention tremor with agents successful in treating essential tremor.[7] Clinical trials of Levetiracetam, typically used to treat epilepsy, and Pramipexole, used to treat resting tremor, have recently been completed to establish their effectiveness in treating kinetic tremor. [8][9] A clinical trial for Riluzole, initially used to treat amyotrophic lateral sclerosis, is currently underway at the Sapienza University of Rome to evaluate its effectivenes of treating cerebellar ataxia and kinetic tremor. [10]
References
edit- ^ a b c d e Seeberger, Lauren Cerebellar Tremor-Definition and Treatment the Colorado Neurological Institute Review Fall 2005
- ^ [ http://www.ninds.nih.gov/disorders/tremor/detail_tremor.htm] National Institute of Neurological Disorders and Stroke “Tremor Fact Sheet” Jan 2011 National Instititues of Health
- ^ Bhidayasiri, R Review: Differential diagnosis of common tremor syndromes Post grad Medical Journal 2005 vol 81 p756–762
- ^ Orrell, Richard (2005) “Review of Multiple Sclerosis: The History of a Disease by T Jock Murray” J R Soc Med 98 (6): 289
- ^ Chou, Kevin (May 2004) “Diagnosis and management of the patient with tremor” Medicine/Health Rhode Island 87 (5): 138
- ^ Walker, H. Kenneth (1990) The Cerebellum in (Eds.)Walker HK, Hall WD, Hurst JW Clinical Methods: The History, Physical, and Laboratory Examinations Ch 69 Reed Publishing
- ^ a b Wyne, Kevin T. (Dec 2005) “A Comprehensive Review of Tremor” JAAPA 18 (12): 43-50
- ^ [ http://clinicaltrials.gov/ct2/show/NCT00430599?term=Levetiracetam+tremor&rank=2] Nichols, P “The Effect of Levetiracetam (Keppra) on the Treatment of Tremor in Multiple Sclerosis” Sept 2009 Clinicaltrials.gov
- ^ [1] Boehringer Ingelheim Pharmaceuticals ”Kinetic Tremor in Parkinsons Disease: Its Course Under Pramipexole (Mirapexin®) Treatment and Impact on Quality of Life” Sept 2010 Clinicaltrials.gov
- ^ [2] Ristori Giovanni “Efficacy of Riluzole in Hereditary Cerebellar Ataxia” April 2010 Center for Experimental Neurological Therapies ClinicalTrials.gov