Dear Sir, A 62-year-old man presented with numbness of the radial side of the left index finger that had begun 1 month previously. A cervical disorder had been excluded. On examination there were no deformities or abnormal skin conditions. There was diminished sensation on the palmar aspect of the radial side of the involved digit from just distal to the distal interphalangeal joint. There was a Tinel sign over the radial digital nerve just distal to the PIP joint. X-ray and MRI examinations showed no abnormal findings that might indicate a tumour-like lesion in the finger. To identify the lesion in the digital nerve, we explored it from the PIP to the DIP joint. Under an operating microscope, two hourglass-like constrictions were revealed just distal to the PIP joint at the same level as the Tinel sign (Fig 1). An external and internal neurolysis of the constricted segment revealed torsion of the nerve. Postoperatively, the numbness gradually improved. Five months after surgery there was diminished sensation over just the radial pulp and the level of the Tinel sign had advanced to the pulp.
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