Ataxia

Ataxia

Ataxia is an impaired ability to coordinate limb movements. There must be no motor paresis (e.g. monoparesis) or involuntary movements (e.g. the characteristic cog-wheel tremor in Parkinson’s disease is not ataxia).
Ataxia may be:

•  Cerebellar.
•  Vestibular.
•  Sensory.

Note: Many forms of ataxia are hereditary (but are uncommon).

Hereditary causes

•  Friedreich’s ataxia.
•  Ataxia telangiectasia.
•  Spinocerebellar ataxia.
•  Corticocerebellar atrophy.
•  Olivopontocerebellar atrophy.
•  Hereditary spastic paraplegia.
•  Xeroderma pigmentosa.

Investigations

• 2 Family studies.
• Genetic analysis (discuss with regional genetics laboratory—counselling may be required).
• Vestibular ataxia
• Acute alcohol intoxication.
•  Labyrinthitis.
• Sensory ataxia
•  Loss of proprioception—peripheral neuropathy, dorsal column disease.
•  Visual disturbance.

Investigations

•  Venous plasma glucose (diabetic neuropathy).
•  Serum vitamin B12 (subacute combined degeneration of the cord—rare, but serious).
•  LFTs.
•  Cryoglobulins.

Cerebellar ataxia

•  Demyelinating diseases, e.g. multiple sclerosis (MS).
•  Cerebellar infarct or haemorrhage.
•  Alcoholic cerebellar degeneration.
•  Cerebellar tumour—primary in children, metastases in adults. Note: Von Hippel Lindau disease
•  Nutritional deficiency:
• Vitamin B12.
• Thiamine.
•  Cerebellar abscess.
•  Drugs (supratherapeutic blood levels):
• – Carbamazepine.
• – Phenytoin. 
• Tuberculoma.
•  Paraneoplastic syndrome.
•  Developmental.
•  Arnold Chiari malformation.
• Dandy Walker syndrome.
• Paget’s disease of skull.
• Wilson’s disease (hepatolenticular degeneration).
• Hypothyroidism.
• Creutzfeldt-Jacob disease and other chronic infections.
• Miller Fisher syndrome.
• Normal pressure hydrocephalus.
• Ataxia should be distinguished from movement disorders, e.g. Chorea
• Huntingdon’s, Sydenham’s, thyrotoxicosis (very rare).
• Athetosis
• Hemiballismus
• Characteristic movement disorder; rare.
• Tardive dyskinesia
• Chronic phenothiazine therapy.

Investigations

•  Cranial CT
• MRI brain (if demyelination suspected).
• CXR (cerebellar metastases from bronchogenic carcinoma; paraneoplastic syndrome).
• TFTs.
• Triple evoked potentials (demyelination).
• Lumbar puncture 
•  LFTs.
•  Serum drug concentrations esp. anticonvulsants.
•  Serum vitamin B12.
•  Erythrocyte transketolase (5 in thiamine deficiency, e.g. alcoholism).
•  Isotope bone scan (Paget’s, metastases).
•  Serum alkaline phosphatase (ALP)—bone isoenzyme (Paget’s, metastases).
•  Urine hydroxyproline (Paget’s disease—reflects bone turnover).
•  Caeruloplasmin (Wilson’s disease).
•  Serum and urine copper (Wilson’s disease).

Consider whether the movement disorder is psychogenic (uncommon)
rather than due to neuropathology. Uncommon and should not be confidently
assumed.