Clinical presentation

• presentation of a patient with ataxia
  • may be:
    • transient (eg following a viral infection in a child)
    • episodic (eg in a patient with multiple sclerosis)
    • progressive (eg in Friedreich’s ataxia, an inherited neurodegenerative disorder)
  • onset may be:
    • acute (eg in a patient with stroke)
    • slow (eg vitamin or thyroid deficiencies)
  • age of onset should be considered:
    • types of disorders presenting with ataxia in children or young adults (frequently developmental, metabolic or inherited causes) tend to differ from those presenting in older people (vascular, neoplastic or neurodegenerative)
  • family history is important
    • almost all forms of genetic transmission are recognised, but generally speaking young-onset ataxias tend to be of autosomal recessive [AR] inheritance (eg Friedreich’s ataxia) whereas the autosomal dominant [AD] ataxias tend to present in young adults and in early middle life
    • with AR inheritance
      • there is a 1 in 4 risk of further siblings also being affected, but the parents of the patient whilst carriers of the mutated gene are themselves clinically unaffected. Parental consanguinity is sometimes identified
    • with AD transmission
      • one of the parents is likely to have similar clinical characteristics, but especially if carrying an unstable triplet repeat containing gene may have much milder clinical features and also may themselves have presented at a later stage in their lives
        • sometimes paternal transmissions particularly tend to lead to dramatically reduced ages of onset and more severe clinical phenotypes in offspring. Mitochondrial disease may be an under-diagnosed cause of ‘inherited’ ataxia, but here the mechanisms of transmission may be complex- including only maternal transmission, AR and rarely AD. Premutations of the fragile-X gene may be a cause of adultonset ataxia (‘Tremor-ataxia syndrome’), and affects men and women
  • presenting symptoms and signs of ataxia are well known, and are usually attributable to dysfunction of the cerebellum or its connections
    • patients complain of slurred speech, clumsiness, incoordination and unsteadiness. Rarely oscillopsia (due to nystagmus) is reported
    • clinical signs of cerebellar dysfunction can be summarised as follows:
      • speech may be slurred (dysarthric) and have a staccato quality
      • extra-ocular movement testing may demonstrate horizontal gaze-evoked nystagmus, hypermetropic/hypometropic saccades and saccadic interposition (jerky smooth pursuit)
      • outstretched arms when displaced show limb hypotonia and rebound phenomena
      • intention tremor
      • dysmetria or ‘past-pointing’
      • dyssynergia
      • dysdiadochokinesis
      • gait ataxia and in extreme cases impaired sitting balance
  • midline cerebellar disease may only be detected by testing walking, especially heel-to-toe or tandem gait
    • important to recognise that impairments in motor function and sensation (especially joint position sense) can mimic cerebellar ataxia
    • Romberg’s sign may detect impaired joint position sense, but in some forms of (spino)cerebellar ataxia, the posterior column sensory modalities are also impaired

Reference:

• (1) Ataxia UK (March 2007). Management of Ataxia: Guidelines on Best Clinical Practice.