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USMLE – Tremor

Abnormal movements usually imply a disorder in the basal ganglia, in which there is disinhibition of the activity of intrinsic rhythm generators or a disorder of postural control. Some, like tremor, are common place. Others, like chorea, athetosis and dystonia, have become more common as a result of pharmacological treatment of Parkinson’s disease and psychiatric disease.

TREMOR Men’s Tremblant Full Zip Hoody
A tremor is a rhythmic oscillating movement of a limb or part of a limb, or of the head. Tremors are usefully divided into those occurring at rest and those seen only when a limb is in action. The other characteristic by which tremors can be classified is their frequency.

Rest tremor
This is pathognomonic of Parkinson’s disease. The tremor is characteristically ‘pill-rolling’, and usually presents asymmetrically. However, patients with Parkinson’s disease may have an abnormal action tremor as well. Tremor of the head in the upright position (‘titubation’) is not a rest tremor since this is a postural tremor, disappearing when the head is supported.

Action tremor
This is more frequently seen than rest tremor and potential, causes are more numerous. A physiological tremor (frequency between 8-12 Hz) can be identified in the limbs of normal subjects and exaggeration of this physiological tremor occurs in anxiety and other situations. Multi-Zone Collection Men

Essential tremor is distinct from a physiological tremor, although resembling it superficially. This tremor is slower than a physiological action tremor and may become quite disabling. The condition is often familial and in some families the tremor is most obvious during certain specific actions such as writing, and here there is an overlap with focal dystonias. Characteristic of essential tremor is that alcohol suppresses it, sometimes to the extent that the patient becomes addicted. Centrally acting beta-adrenoceptor antagonists such as propranolol are often effective in treatment.

An ‘intention tremor’ is the characteristic oscillation at the end of a movement which occurs in cerebellar disease, due to the breakdown of feedback control of targeted movements. Asterixis, the ‘flapping’ tremor seen in metabolic disturbances, is the result of intermittent failure of the parietal mechanisms required to maintain a posture. Thus, when a patient is asked to hold out the arms with the hands extended at the wrists, this posture is periodically dropped, allowing the hands to transiently drop before the posture is taken up again. Occasionally, unilateral asterixis can be seen in an acute parietal vascular lesion.

A more dramatic action tremor occurs with lesions in the superior cerebellar peduncle (the site of the cerebellar outflow towards the red nucleus). This ‘peduncular’ or ‘rubral’ tremor is a violent, large-amplitude postural tremor which worsens as a target is approached. This is common in advanced multiple sclerosis and may be a source of considerable disability. Stereotactic thalamotomy can reduce the tremor, although the overall functional result is often disappointing.

Lillian Thompson By Lillian Thompson

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