High-frequency ultrasound imaging findings in the diagnosis of segmental schwannomatosis of the ulnar nerve: case report and literature review

Schwannomatosis is characterized by the development of multiple schwannomas without evidence of vestibular tumors. Segmental schwannomatosis is defined as being limited to one limb or five or fewer contiguous segments of the spine. We report a case of a 20-year-old male with the painful masses of the left upper extremity with associated numbness and paresthesia in the ulnar nerve distribution. The high-frequency ultrasound showed that the ulnar nerve fascicles were enlarged and expanded with beadlike growth. The patient underwent surgery twice and all the tumors were pathologically confirmed to be schwannomas. Together, the medical history, imaging, and pathology findings indicated the diagnosis of segmental schwannomatosis. By the imaging diagnostic tools, MRI is the most commonly used in assistance with diagnosis of segmental schwannomatosis while high-frequency ultrasonography is rare. In this paper, we discuss the value of high-frequency ultrasonography in the diagnosis of this rare disease. This case report provides a deeper understanding of segmental schwannomatosis and may help improve the accuracy of preoperative diagnosis.