Classification and clinical symptomatology of extrapyramidal syndromes

1. Big picture

The extrapyramidal system is the motor control system that modulates movement outside the direct pyramidal/corticospinal pathway. It does not mainly produce voluntary power like the corticospinal tract. Instead, it regulates:

• initiation of movement;
• speed and amplitude of movement;
• muscle tone;
• posture;
• automatic associated movements;
• suppression of unwanted movements;
• smoothness and fluency of motor activity.

The key exam idea:

Extrapyramidal syndromes are movement disorders caused mainly by basal ganglia circuit dysfunction.

Clinically they are divided into two major groups:

1. Hypokinetic-hypertonic syndromes Less movement + increased tone, mainly parkinsonism.

2. Hyperkinetic-hypotonic syndromes Excess involuntary movement + often reduced/variable tone, including chorea, ballism, athetosis, dystonia, myoclonus and tics.

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