[Case of myotonic dystrophy eventually diagnosed by preoperative Allen's test]

A 59-year-old woman was scheduled for resection of a parotid tumor under general anesthesia. Preoperative interview was done 7 days before the operation. Laboratory data were normal except for a slightly elevated CPK level. Though ECG showed abnormal P and T waves, exercise ECG was normal. Respiratory function test revealed decreased %VC. She did not complain of motor weakness and atrophy of distal muscles. When the anesthesiologist did Allen's test, slow relaxation of hand grip, i.e. grip myotonia, was observed. Further history taking disclosed that she had a family history of myotonic dystrophy (MD) in her son. She was diagnosed as MD by a neurologist on the day of preoperative interview, although she lacked obvious symptoms and consciousness of MD. The operation was performed as scheduled and she was anesthetized with oxygen-nitorous oxide, propofol, fentanyl and vecuronium. Vecuronium was not antagonized because of the adverse effect of neostigmine reported in MD patients. The operation and anesthesia were conducted uneventfully. Her recovery from anesthesia was so smooth that she was discharged uneventfully. In this case, careful examination led to diagnosis of MD and prevented perioperative complications associated with MD. It is important to examine patients meticulously not to miss trivial symptoms in our daily visits.