Abnormal movements include epilepsy, tremor (figure 18; e.g. Parkinson’s disease), spasm, the clonus of upper motor neurone disease, and the athetoid and choreiform movements of birth injuries and chorea. Fascicular movements (flickering) of muscles occur in motor neurone disease and may indicate a hyperexcitable muscle, the movements are precipitated by gentle tapping.

In summary, upper motor neurone lesions initially produce paralysis and hypotonia but subsequently develop weakness, spasticity, hyper-reflexia and an extensor plantar response. Extrapyramdial lesions interfere with the balance of muscle activity, affecting tone, coordination and involuntary movement, without marked loss of power. Cerebellar lesions produce hyptonia and ataxia; lower motor neurone lesions produce weakness, wasting, hypotonia and areflexia.