Hyperkinetic movement disorders: Clinical

The cerebrum, cerebellum, and basal ganglia all help coordinate movements, so movement disorders can be traced back to these structures.

Broadly - there are hypokinetic disorders which cause slowness of movement, and hyperkinetic disorders, which cause excessive involuntary movement. We’ll be talking about the hyperkinetic disorders.

First up is tremor, which is an involuntary, rhythmic movement of a body part, and is the most common of all of the movement disorders.

Tremors can be classified into resting, postural, and action tremors.

Resting tremors develop when the affected body part is resting, and is gravity-dependent, and they usually disappear when the person begins a voluntary movement.

Action tremors are further grouped into kinetic tremors and postural tremors.

Kinetic tremors are simple - if they occur uniformly throughout a voluntary movement - intentional - if it worsens as the affected body part approaches the target - and task-specific - if it occurs during a specific task, like writing.

Intention tremors are often associated with a problem with the cerebellum, and can accompany other cerebellar signs like ataxia and dysmetria.

Postural tremors occur when the individual is in a specific position, such as extending their arms out.

One very specific type of tremor is called a flapping tremor, or asterixis, and it’s induced when a person fully extends their wrists. In a flapping tremor a person will flap their wrists, like a bird flapping it’s wings. It’s a classic sign of a metabolic disorder, like hepatic encephalopathy in liver disease, uremic encephalopathy in kidney disease, and carbon dioxide retention in lung disease.