Essential Tremor

Essential tremor is the commonest movement disorder: a bilateral action tremor of the arms, with or without head, voice or leg tremor, lasting 3 years or more.

• Prevalence is 0.9% overall and 5 to 10% over age 65; bimodal onset (adolescence, over 60).

• Autosomal dominant in about 50% (genetically heterogeneous).

• Cerebellar thalamocortical network involvement; ethanol response.

• Associated mild cognitive and gait changes in elderly.

• Postural and kinetic tremor (4 to 12 Hz) of the hands: difficulty writing, drinking, holding utensils; head "yes yes" or "no no" titubation, voice tremor.

• Improvement with alcohol, worsening with stress, caffeine, fatigue, fasting.

• No rest tremor or bradykinesia (unlike Parkinson disease); mild tandem gait difficulty.

• Clinical diagnosis (Movement Disorder Society criteria).

• Exclude enhanced physiological tremor (thyrotoxicosis, caffeine, drugs: valproate, lithium, salbutamol, SSRIs), Parkinson disease, dystonic tremor, cerebellar disease, Wilson disease in the young, hepatic and renal disease.

• TSH, calcium, liver tests; copper and caeruloplasmin under 40 years.

• DaTscan if diagnosis uncertain (normal in essential tremor).

• Remove aggravating drugs, reduce caffeine.

• Propranolol 40 mg twice daily increased to 120 to 320 mg daily (reduces tremor amplitude by 50% in 60%); avoid in asthma, heart block, diabetes with hypoglycaemia unawareness; extended release 60 to 80 mg daily.

• Primidone 12.5 to 25 mg at night, increased to 250 mg three times daily (initial dose often poorly tolerated).

• Second line: topiramate 25 to 400 mg daily, gabapentin 300 to 1200 mg three times daily, alprazolam 0.125 to 0.5 mg, clonazepam.

• Botulinum toxin for head and voice tremor (focal injections).

• Refractory disabling tremor: deep brain stimulation of the ventral intermediate nucleus (VIM), MR guided focused ultrasound thalamotomy (unilateral), stereotactic radiosurgery.

• Occupational therapy, weighted utensils.