We experienced 3 cases with ulnar nerve palsy at Guyon's canal caused by a schwannoma.
On preoperative examination, all cases had a tender mass at Guyon's camal. There was also loss of sensation in the volar side of the ring and little finger, and a positive Tinnel's sign. Atrophy of the first dorsal interosseus muscle was present in two cases.
On electromyographical examination, termnal latency time of the abductor digiti minimi was delayed in all cases.
Surgical exploration was performed in all cases and the tumour excised easily.
When only using clinical examination, it was very difficult to distinguish between schwannoma with other causes of Guyon's canal syndrome.
