An attempt should also be made to measure, record and grade tremor severity.

The classification of tremor agreed by the International Tremor Foundation, Tremor Investigation Group (TRIG) should be followed (see below). Although tremor may be physiological, there are many different pathological causes and the clinical differential diagnosis will determine the subsequent investigations and treatment pathway.

TRIG classification of tremor

• Rest tremor
• Action tremor:
  • Postural tremor
  • Kinetic tremor
  • Intention (terminal) tremor
  • Isometric tremor
  • Task-specific tremor

Assessment of tremor

• Clinical rating scales
• Spirography, e.g. Archimedes spirals
• Handwriting assessment
• Volumetric methods
• Activities of daily living questionnaires
• Quality of life questionnaires

Treatment of tremor is usually aimed at restoring or improving quality of life. It is therefore important to be aware of the consequences of the tremor for the patient (e.g. diagnostic anxiety, social embarrassment) and the effects on their everyday life. The overall assessment of tremor severity should reflect these effects.

There is often no immediate need to start medication. Decisions should be made after discussions between the patient, their spouses or carer and the clinician about the degree of disability and the risks and benefits of starting drug therapy. If referral to a specialist is considered appropriate, it is preferable to delay starting treatment until they have been seen by the specialist.

In general, start only one new class of medication at a time. Dose titration should always be gradual - medication intended to alter nervous system neurotransmission should never be started or stopped suddenly. It may take three months or more on a therapeutic dose before the full symptomatic benefits become apparent.

Tremor is often refractory to treatment.

The commonest example of a rest tremor is that seen in Parkinson's disease.

Parkinsonian tremor should be treated as Parkinson's disease (see Parkinsonian Tremor section of Parkinson's disease guidance).

Essential tremor is the commonest example of an action tremor. Essential tremor is not uncommonly misdiagnosed as Parkinson's disease, but should also be distinguished from dystonic tremor.

Essential tremor

Essential tremor is usually a postural tremor of 4-10Hz. In contrast to Parkinson's disease, it is a monosymptomatic disorder.

Propranolol

• The mechanism of action of beta-blockers in tremor is not known. Although lipid soluble beta-blockers are more likely to enter the brain and are thus assumed to be more effective in essential tremor, some (but not all) water soluble drugs such as sotalol do seem to work. Atenolol is not effective in tremor.

Primidone

• Start with 50mg at night. Increase slowly (at weekly intervals) to 250mg at night. If no effect, slowly increase further to a maximum of 750mg daily, if tolerated.
• The mechanism of action of antiepileptic drugs on tremor is unknown. Dose is usually limited by side effects, particularly somnolence. Gabapentin may also be tried for this indication using the same dose schedule as for neuropathic pain and epilepsy.

Alcohol in essential tremor

• Two to three units on occasional use. While alcohol consumption should always be enquired about and the recommended weekly maximum intake for men and women applied, the problems of alcohol misuse are reported to be no more common in patients with essential tremor than in the general population.
• Essential tremor is reported to be responsive to alcohol in 50-75% of patients, although the dose required is variable and a marked rebound in tremor severity can occur when the dose wears off.

Dystonic tremor

Dystonic tremor should be treated as for dystonia. Antimuscarinics or dopamine agonists may be helpful. Specialist referral to a dystonia clinic may be required for treatment with either Botulinum toxin type A or Botulinum toxin type B by intramuscular injection.

See section 4.9 Drugs used in parkinsonism and related disorders