Cerebellar Ataxia

Cerebellar ataxia is a disorder of coordination due to a lesion affecting the cerebellum. It is a symptom or syndrome rather than a diagnosis, with many possible causes. Cerebellar ataxia may not be an isolated finding and many causes are associated with other lesions.

• Vascular: stroke or transient ischaemic attack (TIA)
  • Usually with other brainstem features
  • Infarction of the posterior inferior cerebellar artery causes lateral medullary syndrome (Wallenberg syndrome) with hemiataxia, vertigo, dysarthria, ptosis and miosis
• Space-occupying:
  • Hydrocephalus
  • Posterior fossa tumours or abscess

  Note: enlarging masses in the cerebellum may obstruct CSF flow, causing hydrocephalus and raised intracranial pressure. Coning of the cerebellar tonsils can occur rapidly (within hours), causing respiratory arrest.1

• Nutritional:
  • Thiamine deficiency - Wernicke's encephalopathy (triad of acute confusion, ataxia and ophthalmoplegia); requires urgent thiamine treatment
  • Vitamin E deficiency (including a genetic form)⁴
  • Gluten sensitivity (gluten ataxia):⁵
    • Neurological dysfunction can be the only manifestation of coeliac disease, and in this situation, typically presents as cerebellar ataxia, ± peripheral neuropathy
    • Intestinal symptoms and histological changes may be absent
    • The neurological features may reverse with gluten free diet
  • Zinc deficiency (rarely)
• Infections:
  • Bacterial: meningo-encephalitis or intracranial abscess
  • Viral: acute infections (e.g. varicella); chronic infections e.g. human immunodeficiency virus (HIV); post-viral syndromes (e.g. postinfective cerebellar syndrome in childhood)
  • Parasitic infections (e.g. toxoplasma, falciparum malaria, Lyme disease)
  • Prions: Creutzfeldt-Jakob disease, kuru
• Toxins: alcohol, mercury, other heavy metals, solvents, carbon monoxide poisoning
• Drugs: barbiturates, phenytoin, piperazine, antineoplastic drugs
• Trauma
• Multiple sclerosis
• Paraneoplastic cerebellar degeneration:
  • This is cerebellar disease occurring with cancer, but not due to brian secondaries; it may be related to antibodies
  • It can occur with any cancer but most commonly with lung, gynaecological or breast cancer and Hodgkin's lymphoma
• Genetic: there are a number of inherited cerebellar ataxias:
  • Many of these present in adulthood
  • Examples are Friedreich's ataxia (the commonest) and ataxia telangiectasia
• Metabolic and endocrine:
  • Cerebral oedema of hypoxia
  • Wilson's disease (rare)
  • Hypothyroidism (rarely)
  • Inherited metabolic disorders, e.g. Leigh’s syndrome and the mitochondrial disorders
• Congenital:
  • Developmental anomalies e.g. cerebellar hypoplasia, Dandy-Walker syndrome, Arnold-Chiari malformation
  • Cerebral palsy
• There are various other uncommon neurological or metabolic diseases which may involve the cerebellum
• Idiopathic cerebellar ataxia - a diagnosis of exclusion

Episodic ataxia³

This is episodes of ataxia lasting minutes – hours. There are various causes:

• TIA
• Inherited episodic ataxias
• Structural lesions (e.g. intermittent obstruction of the ventricular system).

Lesions of the midline vermis of the cerebellum cause truncal ataxia, while lesions of the cerebellar hemispheres cause limb ataxia of the ipsilateral side.

Symptoms

• Gait disturbance.
• Clumsiness, e.g. with handwriting and difficulty carrying objects.
• Dysarthria.
• Vertigo (sometimes).
• Ask about symptoms of raised intracranial pressure (headache, vomiting, symptoms worse in the morning). These symptoms may indicate dangerous hydrocephalus (see box above).
• Onset and time course help indicate possible causes.
• Other neurological symptoms, systems review and travel history may be relevant.

Signs

• Gait and posture:
  • Broad based gait; heel-toe walking will emphasise the problem; with unilateral lesions patient may fall towards the side of the lesion.
  • Difficulty standing/sitting unsupported (with truncal ataxia).
• Limbs:
  • Observe patient's outstretched hands and gently push each hand downwards. There may be rebound, i.e. overshoot when the hand is pushed and released.
  • Finger-nose and heel-shin movements may show:
    • Intention tremor – occurs during movement and becomes worse during the course of the movement.
    • Dysmetria – misreaching or past-pointing.
  • Test repeated movements such as tapping the finger or rapidly pronating/supinating the hand - may reveal dysdiadochokinesia, i.e. difficulty controlling the rate, rhythm and force of movement.
  • Handwriting.
• Dysarthria - speech may be slurred or scanning (jerky), due to difficulty controlling its rate and rhythm.
• Other possible signs:
  • Check for other neurology and signs of raised intracranial pressure.
  • Rhythmic head movements (titubation) can occur.
  • Nystagmus.

Infants³

Cerebellar dysfunction in an infant is easily overlooked. It may present as delayed motor development in the second year of life.

Distinguish cerebellar ataxia from:

• Other types of tremor
• Spinal or peripheral nerve lesions affecting limb function or sensation
• Vestibular disorders

Depending on the clinical picture, possible investigations are:

• Blood tests: haematology, liver and renal function; vitamin levels (above); infection screens.
• Vitamin E deficiency and gluten sensitivity should be excluded before labelling cerebellar ataxia as idiopathic.
• Radiology: MRI and/or CT.²

• Management depends on the underlying cause.
• For the genetic ataxias, there is useful guidance for GPs from ataxia.org.⁴