[Benign solitary tumors of the peripheral nerves]

Solitary tumors of the peripheral nerves are uncommon and found to be benign in 90 p. 100 of the cases. They develop from the elements constituting the nerve and are generally schwannomas (80 p. 100). Other tumors are much more exceptional and exhibit wide histological variability. The diagnosis of a tumor of the peripheral nerve must be envisaged for all cases with tumefaction or pain on the path of a nerve exacerbated at percussion. Magnetic resonance imaging is the preferred exploration technique, particularly useful in case of a deep tumor. Preservation of nerve continuity is the underlying goal of the therapeutic strategy, irrespective of the type of tumor. Extricable tumors are to be distinguished from inextricable tumors. Extricable tumors (schwannomas, intranervous lipomas) displace nerve fiber bundles without penetrating into the bundle itself and can thus be resected without interrupting nerve continuity. Prognosis is excellent if no recurrence or degeneration occurs. In case of persistent symptoms, a new exploration may be required to search for other localized tumor(s) unperceived at the first procedure. Inextricable tumors (solitary neurofibromas, hemangiomas of the Schwann sheath, neurofibrolipomas) infiltrate the structural elements of the nerve fibers making complete excision impossible without altering the nerve fibers. Epineurotomy (associated with an interfascicular biopsy for pathology examination) allows decompression and can often provide symptom relief although moderate paresthesia may persist. Patients must be informed of this possibility prior to surgery. Any recent and rapidly evolving modification in the clinical findings is suggestive of recurrence and should be followed by revision exploration. Malignant degeneration has not been observed in solitary tumors to our knowledge. Our own experience with 51 cases is generally in agreement with reports in the literature.