synkinesis

Synkinesis is a neurological symptom in which a voluntary muscle movement causes the simultaneous involuntary contraction of other muscles. An example might be smiling inducing an involuntary contraction of the eye muscles, causing a person to squint when smiling. Facial and extraocular muscles are affected most often; in rare cases, a person's hands might perform mirror movements.

Synkinesis is usually caused by dysfunction of a particular nerve. Potential causes include improper healing after nerve trauma or neurodegeneration, as occurs in Parkinson's disease. In congenital cases, mutations of genes involved in nerve growth, specifically axonal growth have been found. Rarely, it occurs as part of syndromes with neuroendocrine problems, such as Kallman syndrome. The prognosis is usually good with normal intelligence and lifespan. Treatment depends on the cause, but is largely conservative with facial retraining or mime therapy, if needed, while Botox and surgery are used as last resort.