Essential tremor (ET) is the most common type of tremor belonging to the group of neurodegenerative diseases with hyperkinetic movement disorders. The group of tremors also includes enhanced physiological, Parkinson’s, orthostatic, cerebellum, rubral and psychogenic tremor.
ET is a monosymptomatic disorder, with no other neurological symptoms besides shaking. The disease was reported for the first time in 1836, but only in 1930 it was described in detail by Minor. It is also called ‘familial tremor’ or ‘senile tremor’. It affects 5% of the population and can develop at any age. Three subtypes of ET exist: familial, sporadic and senile. There are data that the first subtype runs in the families and another member of a family can have the same disease. It starts at a younger age, at about 20. The second type starts after the age of 40, and the senile type comes after the age of 65.
While the pathogenesis is still knot known, the studies demonstrated loss of Purkinje cells and accumulation of Lewy bodies in cerebral structures.
There are clinical manifestations of postural tremor (when outstretching arms in front of body) which is more marked in the dominant arm. It can affect the head, lips, chin, voice, and more rarely the legs. It is not characterized by resting tremor, rigidly increased muscle tone and slowness of movement (bradykinesia). ET can manifest mainly as the inability to make fine, directed movements and feeding gets considerably difficult. Any psychoemotional stress tends to make the tremor worse, and the consumption of small amounts of alcohol has been shown to give short term relief from tremor. ET progresses slowly, therefore patients ask a neurologist for help several years after the occurrence of first symptoms.
Based on electromyographic criteria, ET can be divided into two types: Type A of 6-8 Hz frequency and synchronous activity; and Type B of alternating pattern. Type B patients can develop symptoms of Parkinson’s disease at a later stage. A patient is diagnosed with Minor’s essential tremor based on diagnostic clinical and electromyographic criteria.
In differential and diagnostic plan, ET should be distinguished from Parkinson’s tremor which is characterized by mainly resting tremor and the usual age of occurrence is >55-65 years. Rigidly increased muscle done and bradykinesia are observed as part of the Parkinson’s disease. Unlike ET which can be treated with beta-blockers (propranolol) and/or antiepileptics (primidone, gabapentin, clonazepam), Parkinson’s tremor can be treated with anticholinergics and levodopa.
It is assumed that patients with ET have a higher survival rate compared to the rest of the population. The disease does not result in severe disability; however, it can affect the fine movements of arms.
Treatment is administered with specific medications.