ABSTRACT
A 21-year-old woman developed an acute myotonic reaction while undergoing anaesthesia using succinylcholine. Examination later showed she had shoulder, neck and calf hypertrophy, bilateral symmetrical ptosis and eyelid, handgrip and percussion myotonia. Peripheral neurophysiology studies identified significant, continuous myotonic discharges in both upper and lower limbs. Genetic analysis identified a c.3917G>A (p.Gly1306Glu) mutation in the SCN4A gene, confirming a diagnosis of sodium channel myotonia. Succinylcholine and other depolarising agents can precipitate life-threatening acute myotonic reactions when given to patients with myotonia. Patients with neuromuscular disorders are at an increased risk of perioperative anaesthetic complications. We report a woman who developed an acute myotonic reaction whilst undergoing anaesthesia, in the context of an unrecognised myotonic disorder. We then discuss an approach to the diagnosis of myotonic disorders.
Subject(s)
Anesthesia , Myotonia , Myotonic Disorders , Female , Humans , Young Adult , Adult , Succinylcholine/adverse effects , Hand Strength , Myotonic Disorders/chemically induced , Myotonic Disorders/diagnosis , Myotonia/chemically induced , Myotonia/genetics , NAV1.4 Voltage-Gated Sodium Channel/geneticsABSTRACT
Although colchicine induced myopathy has been described in patients with chronic renal failure, colchicine induced myopathy with myotonia has been reported very rarely. A 49-year-old man with chronic renal failure was hospitalised for investigation of fatigue, malaise and severe pain in all extremities. He was on colchicine therapy for 5 months. Neurological examination showed mildly decreased sensation in a distal symmetric pattern in lower extremities, moderate proximal limb weakness, hyporeflexia and severe myalgia on palpation. No clinical evidence of myotonia was present. Laboratory studies showed elevated creatine phosphokinase (CK), lactic dehydrogenase (LDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. Electromyographic (EMG) findings were compatible with myopathy and abundant, widespread myotonic discharges were determined. Muscle biopsy was consistent with vacuolar myopathy. After withdrawal of colchicine, CK, LDH, AST and ALT levels were normalised and the symptoms were disappeared gradually. In conclusion, the detection of myopathic motor unit potentials with myotonic discharges on EMG in patients on colchicine therapy is an important finding and it is possible to suggest that this clue may lead to the invasive procedure of muscle biopsy unnecessary.
