Congenital mirror movement disorder

Congenital mirror movement disorder is a condition in which intentional movements of one side of the body are mirrored by involuntary movements of the other side. For example, when an affected individual makes a fist with the right hand, the left hand makes a similar movement. The mirror movements in people with this disorder primarily affect the arms, and the hands and fingers are always involved. This pattern of movements is present from infancy or early childhood and usually persists throughout a person's life.

People with congenital mirror movement disorder can have some difficulty with certain daily activities, particularly with those that require different movements in each hand, such as typing on a keyboard. They may experience discomfort or pain in their arms during prolonged use of the hands.

The extent of the mirror movements in people with congenital mirror movement disorder can vary, even within the same family. In most cases, the involuntary movements are noticeable but less pronounced than the corresponding voluntary movements. The extent of the movements typically stay the same throughout the lifetime of an affected individual.

In general, mirror movements are the only feature associated with this condition. In some cases, however, people with congenital mirror movement disorder can have partial or complete absence (agenesis) of the tissue that connects the left and right halves of the brain (corpus callosum).

Mirror movements can also occur in people who do not have congenital mirror movement disorder. Mild mirror movements are common during the normal development of young children, and they typically disappear before age 7. They can also develop later in life in people with neurodegenerative disorders such as Parkinson's disease. Mirror movements may also be present in people with certain conditions that have a wider range of signs and symptoms (syndromes).