Poster 160: Scaphoid-Lunate Disassociation, an Often Missed and Under Diagnosed Condition Presenting as Carpal Tunnel Syndrome: A Case Report

Abstract

Setting: Veteran's outpatient rehabilitation clinic. Patient: A 50-year-old Hispanic woman. Case Description: The patient presented as a referral from her primary care physician for nerve conduction studies (NCS) and needle electromyography (EMG) to rule out carpal tunnel syndrome (CTS). The patient complained of left chronic wrist pain (>3y) with numbness of the thumb and index finger. Physical examination of the upper extremities revealed no muscle atrophy or abnormalities. On palpation of the left radiocarpal joint, extreme pain was elicited, which also caused referred pain into her thumb. Active range of motion (ROM) was within normal limits for all joints in the upper extremity. With passive ROM, extreme pain with left wrist extension into the barrier was elicited. The motor exam was normative; however, there was exacerbation of her pain with left wrist extension against resistance. Light touch sensation was intact. Deep tendon reflexes were all within normative limits. The Tinel's test was negative. Although the Phalen's test was also negative, the patient had difficulty with extending her left wrist secondary to pain. Nerve conduction studies were performed in the bilateral upper extremities. X-rays of her left wrist were also performed (postero-anterior, lateral, oblique and closed fisted with ulnar deviation with right hand comparison). Assessment/Results: Sensory NCS of the bilateral median, left ulnar and left radial nerves were all within healthy limits. Motor NCS of the bilateral median and left ulnar were also all within normal limits. Given the low index of suspicion for neuropathy and radiculopathy, normal conduction studies of the upper extremities and patient's preference, needle EMG was not performed. X-ray of the left wrist showed a left Grade 3 ventral scaphoid-lunate disassociation with a gap greater than 4mm, also referred to as the Terry-Thomas Sign. Conclusions: Chronic wrist pain associated with numbness of the thumb and index finger is often considered and diagnosed as CTS. Scaphoid-lunate disassociation, a very prevalent but often missed diagnostic entity, was the etiology in this patient and can be a source of median nerve compression.