Cauda Canis: Variation of a Tinel’s Sign for a Sciatic Nerve Tumor

Abstract

A patient with a prior history of intradural schwannoma and disc herniation presented with radicular pain after being hit in the thigh by a dog’s tail. She was worked up and found to have a tumor of her right sciatic nerve. The tumor was resected and histology was consistent with schwannoma. The dog’s tail acted as a Tinel’s sign maneuver and led to timely identification of her peripheral nerve tumor. Peripheral nerve schwannomas can present in unusual forms, and Tinel’s maneuver may be a useful tool in diagnosis.

Schwannoma of the Sciatic Nerve as a Cause of Extra-articular Knee Pain: Case Report and Literature Review

“…Benign sciatic nerve schwannomas are usually isolated, solitary, well-circumscribed, and well-capsulated tumors and are rarely in the plexiform [ 3 , 10 ]. Lower limb extremities schwannoma is commonly found in the posterior tibial nerve, and involvement of sciatic nerve schwannoma is rare at 1% [ 4 , 10 , 11 ]. It has an incidence of 0.3–04/100.000 cases per year [ 12 ].…”

“…It has an incidence of 0.3–04/100.000 cases per year [ 12 ]. There are 72 previous reported cases of lower limb sciatic nerve schwannoma that we identified from the literature review from the past 51 years until December 2020 [ 1 , 3 , 4 , 5 , 6 , 8 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ].…”

“…Sciatic nerve schwannoma is rarely associated with neurofibromatosis, with a reported incidence of 3%. 90% are sporadic, 2% have schwannomatosis, and 5% have meningiomatosis with or without neurofibromatosis type 2 [ 7 , 11 , 12 ]. Among the benign sciatic nerve tumors schwannomas account for 38%, while 60% are represented by neurofibromas [ 12 ].…”

“…Schwannoma’s clinical presentation is non-specific, which leads to delayed diagnosis and treatment. They present with a compression effect such as radicular pain (difficult to diagnose or painless), neuropraxia or paresthesia, the Tinel sign of palpation, and difficulty palpating the mass [ 6 , 11 , 12 ].…”

“…Blood vessels may be present with a hyalinized layer. Immunohistochemically, schwannomas show intense and relatively uniform staining for S-100 protein, which is a marker for Schwann cells [ 4 , 6 , 9 , 11 , 12 , 13 , 30 ].…”