Male, 9 years old, with left scapular winging and palpable mass in the superior medial angle of the scapula. The left trapezius muscle is atrophic relative to the right. However, the left sternocleidomastoid muscle demonstrates normal caliber. The scapulae are only partially visualized on this examination, but the left scapula was fully visualized on the accompanying shoulder MRI. Elsewhere in the neck, no obvious masslike lesion is seen. Scattered cervical lymph nodes are within normal limits for age. The aerodigestive mucosa is unremarkable as are the salivary glands and the thyroid. The visualized osseous structures of the cervical spine are within normal limits. No significant compromise of the spinal canal or neural foramina is suspected. The spinal cord demonstrates normal signal characteristics. No enhancing lesions are seen.
Atrophy of the left trapezius muscle is demonstrated, implying dysfunction of the left spinal accessory nerve. Sparing of the sternocleidomastoid muscle would imply that the affected segment is relatively more distal along the course of the nerve. No obvious mass or impinging lesion is identified on this examination to account for the findings. In general, dysfunction of the spinal accessory nerve can result from prior trauma, though it can also be idiopathic.