Radial Nerve Palsy Caused by Desmoid-Type Fibromatosis: A Case Report and Review of the Literature.

Radial nerve palsy (RNP) is classified as traumatic, non-traumatic, or iatrogenic. The most frequent etiologic agent is the fracture of the humerus of the shaftand distal. We experienced a case of RNP caused by desmoid-type fibromatosis around the radial nerve. The RNP caused by desmoid-type fibromatosis has not been reported in the literature. We present this case here with a review of the RNP literature. The patient is a 16-year-old female, right-hand dominant, who became aware of the difficulty in extending her right little finger without any triggers five months ago. She was also aware of the difficulty in extending the ring finger, and her symptoms gradually worsened. She was referred to our hospital after consulting a home doctor. MRI of the elbow showed a high-intensity occupying lesion on T2-weighted images (T2WI) slightly proximal to the elbow joint. Ultrasonography (US) showed a partial nerve constriction and radial nerve enlargement on the distal side of the constriction. The approach was made from the posterior lateral side of the distal upper arm, and the radial nerve was exposed. There was a 1 cm white tissue strongly adherent on the radial nerve, which was compressing the radial nerve, and it was resected piece by piece. After the resection, the radial nerve was indented. The pathological diagnosis of the resected tissue was fibromatosis. Gradually, she was able to extend her fingers after the surgery and recovered completely in six months.