A 10-Year-Old Boy with Muscle Cramps

A 10-year-old boy was evaluated for a 4-month history of muscle cramps. Initially, the cramps occurred twice weekly, usually in his calves. More recently, he had been having cramps in both arms and hands which lasted for up to 5 minutes. On occasion, his fi ngers would get “stuck” for several minutes before he could straighten them. Although he still participates in gym class, his mother reported he had become more cautious about physical activity. There was no history of fever, chills, night sweats, weight loss, visual problems, nausea, vomiting, or diarrhea, although in the past year, he also has noted “dark spots” on his ankles and lower extremities. His past history was unremarkable, although his brother has autism with sensory integration problems. On exam, the patient was alert and appeared healthy. Weight and height were in the 50th percentile. Pulse 88, respiratory rate 16, blood pressure 107/61. There were several 2 to 3 cm hyperpigmented patches with irregular borders on his lower extremities. HEENT exam was unremarkable. Lungs were clear. S1 and S2 were normal without murmurs, rubs, or gallops. Abdomen was soft and non-tender without masses or organomegaly. He was Tanner 1. Both testes were descended. Back was straight. Extremities were normal. Muscle mass was normal without tenderness. On neurologic examination, deep tendon refl exes were 2+ bilaterally. Toes were downgoing. Muscle strength was 5/5 throughout. Cranial nerves II through XII were intact. On initial laboratory evaluation, hemoglobin was 9.7 g/dL, white blood cell count 8,600/mm3 with 45% neutrophils, 41% lymphocytes, 10% monocytes; platelet count 178,000 mm3. MCV was 74, MCH 21, RDW 22 (normal 12.5-16), reticulocyte count 4.5%. Chem14 and ionized calcium were normal save for an albumin of 2 g/dL. GGT was normal. Sedimentation rate and C-reactive protein were normal; CPK was 510 IU/L (normal 27-248 IU/L). Robert Listernick, MD, moderator: I know this may be a profound metaphysical, philosophical question, but what’s a muscle cramp? Nancy Kuntz, MD, pediatric neurologist: You couldn’t have picked a topic more sure to create excitement and argument among neuromuscular specialists than, “What are cramps?” and “What does one do about them?” Both clinicians and patients refer to cramps as persistent or continuous unwanted muscle activity beyond what’s functional. The sensation of “getting stuck” is myotonia, in which there’s delay in relaxation of the muscles; the contraction is normal, but muscle membrane abnormalities make it diffi cult for the muscle to relax. Myotonia is uncomfortable, and people complain about pain. In the evaluation of cramps, family history is important, looking for other individuals with cramping, weakness, or who have the sensation of muscles “getting stuck.” What some patients label “cramps” is instead myokymia — localized involuntary muscle quivering — which may be caused by certain drugs or occur as a result of a paraneoplastic process. Finally, sometimes a cramp is just a cramp. Dr. Listernick: Are there clues on exam to the presence of myotonia rather than simple cramps? Dr. Kuntz: One clue is the presence of percussion myotonia. You hit a relaxed muscle with a refl ex Dr. Listernick is professor of pediatrics at Feinberg School of Medicine, Northwestern University, and director of the Diagnostic and Consultation Service, Division of General Academic Pediatrics, Children’s Memorial Hospital, Chicago, IL. fi rm rounds • fi rm rounds • • fi rm rounds • fi rm rounds

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