Sensory Ataxia
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Clinic
- Sensory Ataxia is a form of ataxia caused not by cerebellar dysfunction but by loss of sensory input into the control of movement
- Ataxia due to loss of proprioception, the loss of sensitivity to the positions of joint and body parts.
- Caused by dysfunction of the dorsal columns of spinal cord, because they carry proprioceptive information up to brain.
- Or dysfunction of the various parts of the brain that receive positional information, including the cerebellum, thalamus, and parietal lobes.
Sign / Symptoms
- Postural instability: Unsteady "stomping" gait with heavy heel strikes.
- Positive Romberg's test
- Worsening of the finger-pointing test with the eyes closed.
- Ataxic hand: When patients are standing with arms and hands extended toward the physician, if the eyes are closed, the patients' fingers tend to "fall down" and then be restored to the horizontal extended position by sudden muscular contractions.
Sensory ataxia also lacks the associated features of cerebellar ataxia such as
- Pendular tendon reflexes: Increased, decreased, or absent reflexes.
- Scanning dysarthria
- Nystagmus
- Broken pursuit eye movements: Smooth pursuit movements are much slower tracking movements of the eyes designed to keep a moving stimulus on the fovea. Such movements are under voluntary control in the sense that the observer can choose whether or not to track a moving stimulus
- Sensory ataxia often has pseudoathetosis.
Causes
Sensory large fiber peripheral neuropathies or dysfunction of dorsal columns of the spinal cord due to:
- Infectious
- Auto-immune
- Metabolic, toxic
- Vascular diseases
- Hereditary diseases
Sensory vs Cerebellar ataxia
| Romberg's sign | Tendon reflexes | Scanning dysarthria | Nystagmus | Pursuit eye movements | Pseudoathetosis | |
|---|---|---|---|---|---|---|
| Sensory ataxia | +++ | --- | --- | --- | --- | +++ |
| Cerebellar ataxia | --- | Pendular / Abnormal | +++ | +++ | Broken | --- |
The presence of the following are associated with SA:
- Kinetic Tremors which appear only on the closure of the eyes. It appears in the last part of a movement toward a target. Its amplitude is low.
- Deep Sensory Loss such as - proprioception, kinesthetic awareness, vibration sense.
- Positive Rhomberg's Test
- Sensory Gait/ High Stepping Gait/ Feet Slapping Gait:
- Heavy strike of the ground on walking due to lost deep sensation.
- High-stepping gait due to associated motor weakness
- Feet-slapping gait - to assist with sound-induced sensory feedback.