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ataxia

ataxia

Introduction

  • ataxia is the inability to maintain motor coordination and this may be:
    • gait - which could be unilateral disturbance
    • speech
    • ocular movements
  • normal balance requires at least two of the following sensory inputs to be functional:
    • vision
    • proprioception (dorsal column of the spine)
    • vestibular apparatus
  • in addition, it also requires the cerebellum and the tracts (thalamus and parietal lobes) to be functional

Cerebellar ataxia

  • ataxia due to dysfunction of the cerebellum which, depending on which cerebellar structures are damaged and whether unilateral or bilateral, may manifest in a number of ways:
    • clumsiness / asynergy
    • inability to accurately assess passage of time (dyschronometria)
    • “ataxic” gait which may demonstrate:
      • inability to stand on one leg
      • inability to perform tandem gait (toe-heel walking)
      • widened base
      • high stepping gait
      • impaired ability to turn resulting in falls risk
      • truncal ataxia - staggering / lurching / drunken gait (spinocerebellum impairment)
      • inability to stand on two legs (hence unable to even perform a Romberg's test thus is not negative or positive test)
    • dysarthria:
      • scanning“ speech (slower speech with irregular rhythm and variable volume)
      • tremor of voice
      • ataxic irregular respiration
      • slurred speech
    • dysphagia
    • dysmetria (eg. finger-nose pointing test and heel-shin test)
      • if motor and sensory systems are intact, an abnormal, asymmetric heel to shin test is highly suggestive of an ipsilateral cerebellar lesion
    • decreased muscle tone
    • dysdiadochokinesia (impaired ability to perform rapidly alternating movements)
    • titubation - forward-backward body/head oscillations
    • intention tremor
    • ocular movements are controlled by the flocculonodular lobe

Sensory ataxia

  • ataxia due to loss of proprioception as a result of dysfunction of either:
    • the dorsal columns of the spinal cord / peripheral neuropathy
    • cerebellum
    • thalamus
    • parietal lobes
  • Romberg's sign should be positive
  • hands out with eyes closed test results in drift
  • finger nose test with eyes closed may be positive
  • often has unsteady “stomping” gait with heavy heel strikes
  • loss of balance when visual inputs impaired such as in darkened rooms

Vestibular ataxia

  • usually associated with vertigo, nausea and vomiting if acute
  • nystagmus is usually present and the patient tends to veer to one side when walking
  • this may be peripheral (labyrinthine apparatus) or central (vestibular areas of the cerebral cortex)

Aetiology

  • various intoxications may cause cerebellar or vestibular ataxia
  • peripheral vestibular causes:
    • BPV
    • viral labyrnthitis
    • Menieres disease
  • stroke may cause cerebellar, sensor or vestibular ataxia
  • brain tumour
  • radiation exposure
  • vitamin B12 deficiency may cause both sensory and cerebellar ataxia
  • cerebellar degeneration:
    • chronic alcoholism
    • head injury
    • paraneoplastic
    • normal pressure hydrocephalus
    • cerebral oedema
    • cerebellitis
    • hereditary ataxias
      • Friedreich's ataxia
      • Niemann Pick disease
      • ataxia-telangiectasia
      • abetalipoproteinaemia
      • fragile X-associated tremor/ataxia syndrome
  • Arnold-Chiari malformation
  • Wilson's disease
  • gluten ataxia - 15% of all cerebellar ataxias
  • succinic semialdehyde dehydrogenase deficiency

clinical tests

can the patient walk normally?

  • a normal gait excludes severe truncal ataxia
  • veering to one side suggests:
    • vestibular ataxia
    • cerebellar ataxia
    • unilateral weakness such as with stroke
  • wide based gait suggests cerebellar ataxia
  • unsteady “stomping” gait with heavy heel strikes suggests sensory ataxia

can the patient stand up normally with eyes open?

  • inability to do this may be due to a number of causes:
    • severe pain
    • weakness
    • cerebellar ataxia
    • decreased mental state

can they walk heel-toe (tandem gait)?

  • inability to do this may be due to a number of causes as for standing, but also in general decline of old age or tremors

Romberg's test

  • this is NOT a test for cerebellar disease
  • positive test is the inability to stand for 60 seconds with the feet together and the eyes closed
  • inability to stand with eyes open is NOT a negative or positive result and may be caused by either:
    • midline cerebellar lesion
    • severe proprioceptive or vestibular lesion
  • it may be positive in any of the types of ataxia
  • it has poor sensitivity (~55-60%) and specificity (~60%) but has better sensitivity for severe sensory ataxia than for other ataxias, especially when tested on foam
  • clinical triad of a pathologic Romberg test on foam, decreased dynamic visual acuity, and catch-up saccades after head impulses to both sides is pathognomonic for a bilateral vestibular loss
ataxia.txt · Last modified: 2018/09/16 19:38 (external edit)