Clonus reflex is an abnormal neurological sign characterized by involuntary, rhythmic muscle contractions that occur in response to a sudden stretch. It's a type of hyperactive reflex.
Understanding Clonus
Clonus is not a normal reflex. Reflexes, in general, are automatic movements your body makes in response to stimulation. These reflexes are protective, helping you avoid injury. However, clonus indicates an underlying neurological issue.
Key Features of Clonus
- Involuntary: You cannot consciously control the muscle contractions.
- Rhythmic: The contractions follow a regular, repeating pattern.
- Muscle Stretch Induced: It's triggered by a quick stretch of the muscle.
How Clonus Differs from Normal Reflexes
| Feature | Normal Reflex | Clonus |
|---|---|---|
| Occurrence | Expected response to a stimulus | Abnormal response, indicating neurological issues |
| Contraction Type | Typically a single, brief contraction | Rhythmic, sustained contractions |
| Control | Under normal neurological control | Involuntary and uncontrollable |
| Clinical Significance | Indicates normal neurological function | Indicates an upper motor neuron lesion or other neurological abnormality |
Example
A common site to test for clonus is the ankle. The examiner sharply dorsiflexes the foot (bends the foot upwards). In a normal response, there is no clonus. If clonus is present, the foot will rhythmically beat up and down.
