Peripheral Nerve Tumors

Background

Peripheral nerve tumors are a varied group of mostly benign tumors that are rare in the general population. Most commonly they represent neurofibromas and schwannomas which may occur sporadically or in association with conditions such as neurofibromatosis (NF).

Causes

Often the cause is unclear. Some tumors are connected to known genetic syndromes, such as neurofibromatosis (type 1 and 2) and schwannomatosis. In these conditions, tumors develop on or adjacent to nerves in any part of the body. These tumors are not infrequently multiple and can lead to symptoms spanning from painful lumps to weakness, numbness and tingling. In other cases, the tumor may be due to a malfunctioning gene. A history of radiation can also increase the risk of developing a peripheral nerve tumor. More often these tumors are benign, but in certain cases, they can be malignant.

Symptoms

Symptoms can vary from a painless lump to focal neurologic deficits, numbness, tingling, weakness in the affected nerve. Pain can occur, and the tumor itself can be tender to touch. They often continue to grow over time.

Diagnosis

The diagnosis is often made with cross sectional imaging such as MRI or ultrasound. The location is critical when deciding how to proceed in terms of treatment.

Treatment

If the tumor is located in a non-critical location, then it can be simply excised/removed. If it is located within or adjacent to other critical structures, a biopsy can be helpful, especially when a malignant nerve tumor is suspected. Surgical excision with nerve monitoring may be the safest option for a benign appearing peripheral nerve tumor.

Belakhoua SM, Rodriguez FJ. Diagnostic Pathology of Tumors of Peripheral Nerve. Neurosurgery. 2021 Feb 16;88(3):443-456. doi: 10.1093/neuros/nyab021. PMID: 33588442; PMCID: PMC7884141.

This is the case of a young graphic designer with a tumor of the ulnar nerve at the elbow with weakness as well as numbness and tingling. She also has evidence of ulnar nerve compression as in cubital tunnel syndrome. The plan is to resect the tumor and to decompress and transpose the nerve at the same time.

In order to preserve nerve function, intraoperative nerve monitoring was performed which means that we were able to perform an EMG and nerve conduction study during the operation itself. The many electrical leads are seen in the picture below.

This image shows the planned incision. The dotted circle represents the site of the tumor.

Here, the tumor has been dissected out.

Once the tumor is excised, the nerve is decompressed and transposed in front of the elbow. Postoperatively, the patient had full ulnar nerve function at 3 months.