Congenital mirror movement disorder

A rare neurological disorder characterized by involuntary movements on one side of the body mirroring voluntary movements on the opposite side.

Congenital mirror movement disorder
Synonyms	CMM disorder
Pronounce
Field	Neurology, Medical genetics
Symptoms	Involuntary mirroring of intentional movements on the opposite side of the body (typically hands)
Complications	Motor coordination difficulties, functional limitations in daily tasks
Onset	Birth or early infancy
Duration	Lifelong
Types	Isolated (nonsyndromic) or syndromic forms
Causes	Mutations in the DACT1, RAD51, or DNAL4 genes; disruption in corticospinal tract development
Risks	Family history of CMM; autosomal dominant inheritance pattern
Diagnosis	Clinical examination, electromyography (EMG), genetic testing
Differential diagnosis	Parkinson's disease, Klippel–Feil syndrome, Moebius syndrome
Prevention	None
Treatment	Supportive care, occupational therapy, physical therapy
Medication	None specific; botulinum toxin in some cases
Prognosis	Typically stable; symptoms may improve with therapy but usually persist
Frequency	Rare
Deaths	Not life-threatening

Congenital mirror movement disorder (CMM) is a rare neurological disorder characterized by involuntary movements on one side of the body that mirror voluntary movements on the opposite side. This condition is present from birth and is typically noticed in early childhood.

Presentation

Individuals with congenital mirror movement disorder exhibit involuntary movements that occur simultaneously with intentional movements on the opposite side of the body. For example, when a person with CMM moves their right hand, their left hand may involuntarily perform the same movement. These mirror movements are most commonly observed in the upper limbs, particularly the hands and fingers, but can also affect the lower limbs.

Pathophysiology

The exact cause of congenital mirror movement disorder is not fully understood, but it is believed to involve abnormal development of the nervous system. In typical development, the motor cortex in the brain controls movements on the opposite side of the body. In individuals with CMM, there may be abnormal connections or lack of proper inhibition between the two hemispheres of the brain, leading to simultaneous activation of both sides.

Genetics

Congenital mirror movement disorder can be inherited in an autosomal dominant pattern, meaning a single copy of the altered gene in each cell is sufficient to cause the disorder. Mutations in the DCC gene have been associated with CMM. The DCC gene is involved in the development of the nervous system, particularly in the guidance of neurons and the formation of neural circuits.

Diagnosis

Diagnosis of congenital mirror movement disorder is primarily clinical, based on the observation of mirror movements. Neurological examination and electromyography (EMG) may be used to assess the extent and nature of the movements. Genetic testing can confirm the presence of mutations associated with the disorder.

Management

There is currently no cure for congenital mirror movement disorder. Management focuses on minimizing the impact of the disorder on daily activities. Physical therapy and occupational therapy may help improve motor skills and coordination. In some cases, botulinum toxin injections have been used to reduce the severity of mirror movements.

Prognosis

The prognosis for individuals with congenital mirror movement disorder varies. While the condition is lifelong, many individuals learn to adapt to the involuntary movements and lead normal lives. The severity of the disorder can vary widely among affected individuals.

Related pages

• Neurological disorder
• Motor cortex
• Autosomal dominant
• DCC gene