# A Case of Pediatric Retroperitoneal Schwannoma Presenting with Myoclonus of the Lower Limb: A Case Report and Review

## TL;DR

A rare case of a 6-year-old boy with a retroperitoneal schwannoma causing leg myoclonus is reported, with successful surgical removal and no recurrence.

## Contribution

This is only the fifth reported case of retroperitoneal schwannoma in children and the first to present with myoclonus.

## Key findings

- A retroperitoneal schwannoma was successfully resected in a 6-year-old boy.
- Post-surgery, the patient's myoclonus resolved and there was no recurrence after 9 months.
- Only four pediatric retroperitoneal schwannoma cases have been reported in English previously.

## Abstract

Schwannomas arise from Schwann cells of the peripheral nerve sheath. Schwannomas are usually benign, and most of them are located in the head, neck, or distal extremities. The retroperitoneal region is an unusual location for schwannomas. Schwannomas are usually seen in adults and are very rare in the pediatric population.

A 6-year-old boy was referred to our institution with a right abdominal mass. His main complaint was intermittent myoclonus of his right lower limb. Abdominal computed tomography (CT) and magnetic resonance imaging scans revealed a round-shaped solid mass measuring 78 × 61 mm adjacent to the caudal side of the right kidney. Right hydronephrosis and hydroureters resulting from ureteral compression were present. A positron emission tomography-CT scan showed mild accumulation of fluorodeoxyglucose. Tumor resection was performed by laparotomy, and the mass was completely excised. Postoperative pathologic examination showed a benign schwannoma. The myoclonus of the right lower limb that had been present before surgery disappeared after surgery. At 9 months since the operation, there has been no recurrence.

We present a pediatric case of a retroperitoneal schwannoma causing myoclonus of the lower limb. Retroperitoneal schwannomas in children are extremely rare, with only 4 cases having been reported in English.