Schwannomas are benign, usually slow-growing tumors that originate from Schwann cells surrounding peripheral, cranial, or autonomic nerves. The most common form of these tumors is acoustic neuroma. Schwannomas of the brachial plexus are quite rare, and symptomatic schwannomas of the brachial plexus are even rarer. A 47-year-old woman presented with a 1-year history of dysesthesia, neuropathic pain, and mild weakness of the right upper limb. Results of physical examination and electrodiagnostic studies supported a diagnosis as thoracic outlet syndrome. Conservative treatment did not relieve her symptoms. After 9 months, a soft mass was found at the upper margin of the right clavicle. Magnetic resonance imaging showed a 3.0×1.8×1.7 cm ovoid mass between the inferior trunk and the anterior division of the brachial plexus. Surgical mass excision and biopsy were performed. Pathological findings revealed the presence of schwannoma. After schwannoma removal, the right hand weakness did not progress any further and neuropathic pain gradually reduced. However, dysesthesia at the right C8 and T1 dermatome did not improve.
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True neurogenic thoracic outlet syndrome (TOS) is an uncommon disease and is difficult to diagnose at the early stage and then completely cure. We experienced a case of true neurogenic TOS with typical clinical symptoms and electrophysiologic findings as a result of repetitive habitual sleep posture. A 31-year-old woman who had complained of progressive tingling sensation on the 4th and 5th fingers with shoulder pain was diagnosed of brachial plexopathy at the lower trunk level by electrodiagnostic studies. There was no other cause of brachial plexopathy except her habit of hyperabduction of shoulder during sleep. This case demonstrated that the habitual abnormal posture can be the only major cause of neurogenic TOS. It is of importance to consider TOS with the habitual cause because simple correction of the posture could stabilize or even reverse disease progress.
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