Schwannoma of the Tibial Nerve

Schwannoma is a benign, well-defined, and solitary nerve sheath tumor and accounts for 5 % of all soft tissue tumors. It can occur anywhere along the peripheral nervous system. It is a slowly growing tumor and usually presents as a painless, discrete, and firm swelling before being diagnosed, unless it grows in a confined place. Preoperative diagnosis of schwannoma is often difficult. Computed tomography, magnetic resonance imaging, and sonography are useful imaging modalities in the preoperative assessment of nerve sheath tumors. Although imaging may not be reliable in distinguishing nerve sheath tumors from each other, certain imaging characteristics should raise the suspicion of schwannoma. Keywords sonography, schwannoma, tibial nerve Schwannoma is a benign, well-defined, and solitary nerve sheath tumor and accounts for 5 % of all soft tissue tumors.1 It can occur anywhere along the peripheral ner-vous system. It is a slowly growing tumor and usually presents as a painless, discrete, and firm swelling before being diagnosed, unless it grows in a confined place. Pre-operative diagnosis of schwannoma is often difficult. Computed tomography (CT), magnetic resonance imag-ing (MRI), and sonography are useful imaging modalities in the preoperative assessment of nerve sheath tumors.2 Although imaging may not be reliable in distinguishing the type of nerve sheath tumors, certain imaging charac-teristics should raise the suspicion of schwannoma. Case Report A middle-aged woman presented to the emergency department at our institution with a prolonged history of left leg pain that was increasing gradually over 7 years along with a recent onset of left knee pain. There was no history of trauma. Physical and neurological examina-tions on admission revealed no abnormalities except for a limited and painful 65-degree flexion of the left knee. The patient was referred for a sonographic examina-tion to rule out deep vein thrombosis (DVT). A sono-graphic examination of the left leg using a 9-MHz linea