Ataxia = lack of coordination of movements.
Types = cerebellar, sensory, vestibular.
Cerebellar
Vestibulocerebellar: Eye movements; causes postural instability. The patient tends to separate her feet when standing to avoid body oscillations (especially forward-backward ones. The instability is therefore worse when standing with feet together, regardless of whether the eyes are open or closed (eyes are defective). Romberg's test is negative, denoting the patient's inability to carry out the test because she feels unstable even with open eyes.
Spinocerebellar: Body and limb movements; causes wide-based 'drunken sailor' gait.
Cerebrocerebellar: Voluntary, planned movements:
- Intention tremor (could involve the head and eyes and torso and limbs).
- Handwriting abnormality: Large unequal letters; irregular underlining.
- A particular pattern of dysarthria: Slurred speech, sometimes characterised by explosive variations in voice intensity despite a regular rhythm.
Sensory
Ataxia due to loss of proprioception. Usually caused by dysfunction of the dorsal columns of the spinal cord. However, the cause may also be dysfunction of the parts of the brain that receive postural information, including the thalamus, cerebellum, parietal lobes.
- Unsteady, 'stomping' gait with heavy heel strikes.
- Postural instability that is worsened when there is no visual input, e.g. poorly lit environment. Romberg's positive.
- Worsening of the finger-pointing test with eyes closed.
- Pyramidal (corticospinal) drift when eyes are closed. The patient's arms will tend to drop and then be restored to the horizontal extended position by sudden muscular contractions (the 'ataxic hand').
Vestibular
Symptoms of vestibular dysfunction:
- Acute & unilateral: Vertigo, nausea, vomiting.
- Chronic & bilateral: Vertigo, nausea and vomiting may be absent. Dysequilibrium may be the sole presentation.
