Akbar, 24 years old male, factory worker presented to us with a complaint of synergistic movement of both upper limbs that create difficulty during his work and the condition persists since birth 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.
Bimanual Synkinesis occurs when left and right upper limbs, especially the hands and fingers execute exactly the same movement even though only one hand is intentionally moved. It is also called “mirror hand movements” and persists throughout life. When it occurs by itself without other associated signs and symptoms it is associated with normal intelligence and lifespan. It can also develop in the course of Parkinson’s disease. In association with other abnormalities, mirror hand movements are a hallmark of Kallmann syndrome. Genetic mutations associated with (congenital) mirror hand movements are in the DCC (gene) or RAD51 gene, which account for about 35 percent of cases. In DCC mutation, impaired or missing netrin 1 receptor protein impairs control of axon growth during nervous system development.
Almost all cases of synkinesis develop as a sequel to nerve trauma. (The exception is when it is congenitally acquired as in Duane-Retraction Syndrome and Marcus Gunn phenomenon.) Trauma to the nerve can be induced in cases such as surgical procedures, nerve inflammation, neuroma, and physical injury.