ataxia

see also:

• neurology
• examination of cranial nerves
• ataxia
• stroke (CVA)
• transient ischaemic attack (TIA)
• vertigo - peripheral vs central

• 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

• 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

• 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

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

• various intoxications may cause cerebellar or vestibular ataxia
  • eg. ethanol, anticonvulsants, lithium carbonate toxicity, ketamine, benzodiazepines, mercury poisoning
• peripheral vestibular causes:
  • BPV
  • viral labyrnthitis
  • Menieres disease
• stroke may cause cerebellar, sensor or vestibular ataxia
• brain tumour
• multiple sclerosis (MS)
• radiation exposure
• vitamin B12 deficiency may cause both sensory and cerebellar ataxia
• hypothyroidism
• cerebellar degeneration:
  • chronic alcoholism
  • head injury
  • paraneoplastic
  • normal pressure hydrocephalus
  • cerebral oedema
  • cerebellitis
  • coeliac disease
  • 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

• 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

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

• 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

• 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