Tremor

Tremor may be classified as rest, postural, and intentional, according to its relation to activity. Rest tremor is best seen when the limbs are relaxed, resting in the patient’s lap; when necessary, mental exercises may help to “bring out” the dyskinesia. A 3- to 5-Hz rest tremor is a characteristic feature of Parkinson disease (“pillrolling” tremor), in which it often starts asymmetrically. One important feature of this type of tremor is its disappearance or improvement with limb movement. Although the tremor may become bilateral with disease progression, it commonly remains more severe on the initially affected side.

Postural tremor is seen when the limbs are actively maintained in a particular posture against gravity and disappears when the limbs are at rest. Examples of postural tremors are essential tremor, drug- or toxininduced tremor, metabolic conditions, and alcohol withdrawal states. Physiologic tremors are also postural in nature and are seen in all individuals at a frequency of 8 to 12 Hz. They are enhanced by caffeine, fear, or anxiety.

Essential tremor is a sporadic condition, but in approximately 50% of those affected, a family history may be elicited (familial tremor). Typically, a 5- to 8-Hz tremor is present bilaterally in the hands or arms. A tremor of the head or vocal cords is also common. Patients often noticed an improvement in tremor after having a sip of alcohol. Most cases are mild and do not require treatment, but when necessary, propranolol, primidone, or certain antiepileptic drugs may be effective.

Intention tremor is the tremor most commonly associated with disease of the cerebellum and its associated pathways, but it may be seen in patients with advanced essential or familial tremor. The tremor, which occurs during movement, can be unilateral or bilateral, depending upon the cerebellar lesion, and may affect upper and lower limbs. It has a frequency of 2 to 4 Hz and characteristically worsens as the limb approaches its target (end-point accentuation). Another term used for cerebellar outflow tremor is rubral tremor. We discourage the use of such a term because these are not specific for lesions found only at the red nucleus. We prefer the term cerebellar outflow tremor to describe intention, rubral, or cerebellar tremor.

A “wing beating” tremor has been described in patients with Wilson disease and in patients with multiple sclerosis or stroke involving the superior cerebellar peduncular region. In these patients, the tremor is most prominent when flexing the forearms at the elbows and elevating the shoulders laterally to reach a 90-degree angle in the fully abducted position. This “phenomenology” is similar to that in cerebellar outflow tremor, particularly when severe, and probably represents involvement of cerebellothalamofugal pathways.

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