Myoclonus, commonly associated with tremor, is a common movement disorder. The majority of cases are associated with encephalopathy/delirium and the commonest causes in South Africa are probably encephalitis related to an underlying infectious process (typically HIV, but also other forms of meningitis) and to organ failure.

It is probably reasonable to approach patients presenting with myoclonus on the basis of age; the following groups represent common causes but it should be emphasized that there are many other causes.

Elderly:

Neurodegenerative diseases, chiefly:

  1. PD with dementia and dementia with Lewy bodies (DLB)
  2. Alzheimer disease
  3. Corticobasal syndrome (CBS), noting that a common pathology for CBS is of Alzheimer type, as well as PSP and FTD, and that a presentation of CBS does not reliably predict corticobasal disease (CBD).
  4. Multi-system atrophy: classically this is associated with polyminimyoclonus, which may be stimulus responsive. Low amplitude, tremulous movements occur in the distal arms and fingers, particularly with posture or during voluntary movements (jerky postural tremor).
  5. Creutzfeldt-Jakob disease is a classical cause but is uncommon.

Drugs: opiates, sodium valproate

3rd to 4th decade to Elderly:

  1. Coeliac disease
  2. Opsoclonus myoclonus syndrome in HIV positive patients
  3. Encephalitis
  4. Lafora body disease
  5. Biotin deficiency (rare)

 

Adolescent:

All cons

Encephalitis

 

Gaucher

Lafora body disease

Autosomal dominant cortical tremor myoclonus and epilepsy [ADCME])

 

Paediatric

Epileptic encephalopathies and a large number of metabolic illnesses, of which the following are likely most important:

Tay-Sachs

Opsoclonus myoclonus syndrome in childhood is typically associated with neuroblastoma

medulloblastoma