Familial congenital mirror movements

Familial congenital mirror movements (also known as congenital mirror movements or bimanual synkinesis) is a rare neurological condition characterized by involuntary movements of one side of the body that mirror intentional movements made on the opposite side. These mirror movements predominantly affect the hands and fingers, meaning that when a person performs a voluntary movement with one hand, the other hand simultaneously and involuntarily performs the same movement. The condition is present from birth or early infancy and typically persists throughout life, though the severity of mirror movements may slightly decrease with age in some individuals. The underlying cause involves abnormal development of the corticospinal tract, the major nerve pathway that connects the brain to the spinal cord and controls voluntary movement. In healthy individuals, the corticospinal tract is predominantly crossed (contralateral), meaning each hemisphere of the brain controls the opposite side of the body. In familial congenital mirror movements, there is an abnormal ipsilateral (same-side) corticospinal projection, resulting in both hemispheres simultaneously activating muscles on both sides. Mutations in the DCC (deleted in colorectal carcinoma) gene on chromosome 18q21.2 and the RAD51 gene on chromosome 15q15.1 have been identified as causes. The DCC gene encodes a receptor involved in axon guidance, particularly in the midline crossing of corticospinal tract fibers. The condition primarily affects the motor system, and individuals generally have normal muscle strength, coordination, and cognitive function. However, mirror movements can cause significant functional impairment in daily activities requiring independent bimanual hand movements, such as typing, playing musical instruments, or performing fine motor tasks. There is currently no curative treatment for familial congenital mirror movements. Management is supportive and may include occupational therapy to help individuals develop compensatory strategies for tasks requiring independent hand use. The condition does not typically worsen over time and is not associated with other neurological deterioration.

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