Other movement disorders

Essential tremor

Essential tremor is a common problem, with a prevalence of 3 in 1000. It is a slowly progressive 5–8 Hz tremor that is postural and worse on action. It is usually asymmetrical, involving the hands and affecting writing and fine movements (Fig. 1). It may affect the head (yes-yes head titubation). Patients usually present later in life but have generally been aware of the tremor for many years. About 60% of patients will notice a marked improvement with small amounts of alcohol. About half the patients have a family history when the inheritance is dominant.

Fig. 1 Writing in essential tremor. Note the spiral has become larger (cf. Parkinsonism).

The diagnosis is clinical. Most patients respond well to propranolol. Primidone, an anticonvulsant, may be useful if beta-blockers are contraindicated or ineffective. Very occasionally, in severely affected patients, stereotactic thalamotomy may be needed.

Other tremors

Physiological tremor. A tremor of 8–12 Hz that is normally present but can be enhanced by anxiety, hyperthyroidism, drugs (such as beta agonists or sympathomimetics) and alcohol withdrawal.

Cerebellar tremor. A slower tremor (3 Hz) that increases as the limb is moved towards the target (intention tremor). There may be yes-yes head titubation.

Rest tremor. See section on Parkinsonism.

Orthostatic tremor. A rare tremor which appears in the legs on prolonged standing. It is treated with clonazepam, gabapentin and levodopa.

Cervical dystonia

This is a common condition. The involuntary contraction in the neck muscles results in:

abnormal head movements

abnormal head position

neck pain.

The direction of movement and abnormal head position vary depending on which muscles are overactive. For example, if one sternocleidomastoid is overactive, the head will turn to the opposite side; if both splenius capitis are affected, the head will look up (retrocollis). Often the patient will be aware that a particular manoeuvre, for example touching the cheek in a certain position (referred to as a ‘geste’), can stop an abnormal movement.

In most patients no cause is found. Sometimes this can be triggered by neuroleptics or, occasionally, structural lesions in the basal ganglion.

Patients can be treated symptomatically with botulinum toxin. This toxin weakens the affected muscle for 3–4 months, so relieving symptoms. Side effects are infrequent, mostly producing weakness in the treated muscles or, rarely, adjacent muscles, for example muscles of speech and swallowing.

Writer’s cramp and other task-specific dystonias

These conditions, of unknown aetiology, were previously considered to be psychiatric. During a specific activity, an abnormal tension and posture develop in the hand. This most commonly occurs during writing, but has been associated with a range of skilled motor tasks such as typing, playing the guitar or playing darts. In writer’s cramp, the way the pen is held often changes and the patient may complain of breaking pens and pressing very hard on the paper.

The response to treatment is poor. Patients do best if there are ways of avoiding the activity involved, for example moving from handwriting to using a computer. Occasionally botulinum toxin can help.