gms | German Medical Science

Objective: Neuromuscular choristoma is a rare entity of peripheral nerve sheath lesion. Pathologically it is a hamartoma, in particular skeletal muscle fibres are admixed within nerve fibres of a peripheral nerve. They grow longitudinal inside the nerve sheath, which results in a diffuse thickening of the nerve and in a progressive compression of nerve fibres. It cannot be removed completely without sacrificing the affected nerve.

Methods: We treated a seven year old female, who presented with progressive weakness of the peroneal innervated muscles and an enlarged sciatic nerve as the supposable cause in the MR-Neurography. Initially the differential diagnosis was perineurioma. We performed an epineuriotomy and a biopsy of an affected fascicle. Clinical finding after surgery were identical. Pathological studies found well differentiated skeletal muscle fibres with small groups of nerve fibres. Also a review of the literature was performed.

Results: There are only a few cases reported in the literature and the most commonly affected nerve is the sciatic nerve. Some authors describe an aggressive fibromatosis of the nerve and its surrounding tissue, occurring after a performed nerve-biopsy. The pathomechanism of this complication is not clear. Also there are attempts to distinguish this lesion from other primary nerve tumors by MRI.

Conclusion: Little is known about neuromuscular choristomas due to the very small number of cases that could be studied so far. In our case we plan neurological and MRI controls once a year and we have already contacted other centers for optimal diagnosis and treatment of these extremely rare nerve tumors.