Schwannomatosis of the Spinal Accessory Nerve: A Case Report

Abstract

Schwannomatosis is a distinct syndrome characterized by multiple peripheral nerve schwannomas that can be sporadic or familial in nature. Cases affecting the lower cranial nerves are infrequent. Here, the authors present a rare case of schwannomatosis affecting the left spinal accessory nerve. Upon genetic screening, an in-frame insertion at codon p.R177 of the Sox 10 gene was observed. There were no identifiable alterations in NF1, NF2, LZTR1, and SMARCB1. This case demonstrates a rare clinical presentation of schwannomatosis in addition to a genetic aberration that has not been previously reported in this disease context.

Keywords: diffusion tensor imaging; neck mass; schwannoma; schwannomatosis; spinal accessory nerve tumor.

Fig. 1

( A–C ) Positron emission tomography–computed tomography (PET CT) was performed, which demonstrated increased fluoro-2-deoxy-d-glucose uptake in both masses (standardized uptake value of 7.3 for the larger mass and 2.7 for the smaller mass).

Fig. 2

Magnetic resonance imaging (MRI) neurogram demonstrated a larger 4.6 × 3.2 × 2.5 cm mass deep to the left sternocleidomastoid muscle just below the angle of the mandible (A–C) and a bilobed 2.4 × 2.2 × 1.3 cm mass in the left posterior supraclavicular region (D–F) .

Fig. 3

Further imaging characterization of lesions. (A) Diffusion tensor imaging with tractography demonstrated abnormal thickened nerve fibers coursing through the two spinal accessory nerve tumors. (B) Axial diffusion weight imaging (left) and apparent diffusion coefficient (ADC) images (right) of the lesions. ADC values were 1.3 × 10 ⁻⁶ and 1.8 × 10 ⁻⁶ mm ² /second for the larger and smaller masses, respectively.

Fig. 4

Intraoperative findings. (A) Two separate incisions were required to remove both lesions. (B) The smaller bilobed lesion mass was accessed through the posterior triangle of the neck and was located on the distal spinal accessory nerve. (C) The larger more proximal mass was approached medial to the sternocleidomastoid muscle in the upper neck. Both masses underwent a gross total resection.