Cerebellar Lesions

The main causes of cerebellar lesions are:

• Trauma
• Cerebrovascular event
• Neoplasm
• Degenerative
• Demyelinating disease e.g. multiple sclerosis

As cerebellum associated with movement control, lesions produce a range of movement disorders (ataxias).¹ These can be differentiated by their time course

Acute onset ataxia

• Either due to cerebellar haemorrhage or infarction. Haemorrhage presents with:
  • Occipital headache
  • Vertigo
  • Vomiting
  • Altered consciousness

Sub acute ataxia

May occur from:

• Viral infection - children aged 2-10 years; with pyrexia, limb and gait ataxia, dysarthria appearing over hours or days; takes up to six months for full recovery
• Post-infectious encephalomyelitis - in older patients; commonly related to varicella infection but other organisms may be involved
• Other causes include - hydrocephalus, posterior fossa tumours, abscess, parasitic infection and various toxins

Episodic ataxias

• May appear bizarre and be misdiagnosed as of hysterical origin. Causes include:
  • Drugs
  • MS
  • Transient vertebrobasilar ischaemic attacks
  • Foramen magnum compression
  • Inherited periodic ataxia, dysarthria, nystagmus and vertigo
  • Intermittent obstruction of ventricular system of which there are two types:

1. Brief attacks which may benefit from acetazolamide or phenytoin and patient normal between attacks.
2. More prolonged attacks which are often associated with nausea, vertigo and vomiting. More severe in childhood with drowsiness, headache and fever and interictal nystagmus; slow deterioration in the ataxia and responds to acetazolamide; (screen for metabolic disorder).

Chronic progressive ataxias

• Commonly caused by chronic alcohol abuse associated with malnutrition
• May improve with thiamine
• May also occur with other deficiencies including zinc and vitamin E
• Other causes:
  • Ingestion of drugs - especially anticonvulsants, particularly phenytoin (may reverse once drug stopped)
  • Solvent abuse
  • Heavy metals
  • Structural lesions
  • Paraneoplastic cerebellar degeneration associated with carcinomas of the lung or ovaries
  • CJD (rare)

• Dysdiachokinesis
• Slurred speech and dysarthria
• Hypotonia
• Intention tremor
• Past pointing
• Nystagmus
• Optic atrophy may be present in demyelination disorders
• Gait abnormality - heel-toe walking

Note that Romberg's test is positive with the presence of abnormal joint position sense. In cerebellar disease the patient is unable to balance whether eyes open or not - but this is not true Romberg's positive.

• Often only cause is non-specific motor development
• Later develop nystagmus, incoordination and truncal ataxia on attempting to sit
• Often associated with mental retardation³
• Non-progressive and coordination usually improves with age
• Other causes include:
  • Pontocerebellar hypoplasia - need to look further for metabolic or degenerative disorders⁴
  • Joubert syndrome
  • Anorexia nervosa
  • Trisomies
  • Pyruvate dehydrogenase deficiency
  • Spastic ataxic syndrome

These should be guided according to the differential diagnosis based upon the initial assessment. This may include

• Blood tests - full blood count, liver function tests, cholesterol, protein electrophoresis, copper and caeruloplasmin, immunoglobulins and glycoproteins
• EEG
• EMG
• Imaging - MRI is the modality of choice

This depends upon the underlying cause.