A test used to check neurological function for balance, driving under the influence of an intoxicant (alcohol or drug), and neurological decompression sickness.
It is based on the premise that a person requires at least two of the three following senses to maintain balance while standing:
- Proprioception: Ability to know one's body position in space.
- Vestibular function: Ability to know one's head position in space.
- Vision: Ability to monitor and adjust for changes in body one's body position.
In the test, the standing person is asked to close one's eyes. An increased loss of balance is the positive sign.
- Unknown: A tendency to sway and fall that is already evident with eyes open is suggestive of dizziness of vestibular or cerebellar origin.
- Positive: A tendency to sway and fall with eyes closed is suggestive of a spinal disorder (e.g., polyneuropathy).
Ataxia: Loss of motor coordination.
- Cerebellar ataxia: Caused by dysfunction of the cerebellum, that is responsible for integrating a significant amount of neural information used to coordinate smoothly ongoing movements and to participate in motor planning.
- Sensory ataxia: Caused by loss of proprioception, the loss of sensitivity to the positions of joint and body parts. It is generally caused by dysfunction of the dorsal columns of the spinal cord, because they carry proprioceptive information up to the brain. In some cases, it is caused by dysfunction of the cerebellum, thalamus, or parietal lobe, that receives positional information.
- Vestibular ataxia: Caused by dysfunction of the vestibular system. In acute and unilateral cases, it is associated with prominent vertigo, nausea, and vomiting. In chronic bilateral cases, dysequilibrium may be only the symptom.