Cases That Test Your Skills

The boy whose arm wouldn’t work

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B, age 10, develops an unsteady gait and sustained flexion of his wrist. He has autism spectrum disorder and has maintained the same medication regimen for the last year. How do you proceed?



CASE Drooling, unsteady, and not himself

B, age 10, who is left handed and has autism spectrum disorder, is brought to the emergency department (ED) with a 1-day history of drooling, unsteady gait, and left wrist in sustained flexion. His parents report that for the past week, B has had cold symptoms, including rhinorrhea, a low-grade fever (100.0°F), and cough. Earlier in the day, he was seen at his pediatrician’s office, where he was diagnosed with an acute respiratory infection and started on amoxicillin, 500 mg twice daily for 7 days.

At baseline, B is nonverbal. He requires some assistance with his activities of daily living. He usually is able to walk without assistance and dress himself, but he is not toilet trained. His parents report that in the past day, he has had significant difficulties with tasks involving his left hand. Normally, B is able to feed himself “finger foods” but has been unable to do so today. His parents say that he has been unsteady on his feet, and has been “falling forward” when he tries to walk.

Two years ago, B was started on risperidone, 0.5 mg nightly, for behavioral aggression and self-mutilation. Over the next 12 months, the dosage was steadily increased to 1 mg twice daily, with good response. He has been taking his current dosage, 1 mg twice daily, for the past 12 months without adjustment. His parents report there have been no other medication changes, other than starting amoxicillin earlier that day.

As part of his initial ED evaluation, B is found to be mildly dehydrated, with an elevated sedimentation rate on urinalysis. His complete blood count (CBC) with differential is within normal limits. A comprehensive metabolic panel shows a slight increase in his creatinine level, indicating dehydration. B is administered IV fluid replacement because he is having difficulty drinking due to excessive drooling.

The ED physician is concerned that B may be experiencing an acute dystonic reaction from risperidone, so the team holds this medication, and gives B a one-time dose of IV diphenhydramine, 25 mg, for presumptive acute dystonic reaction. After several minutes, there is no improvement in the sustained flexion of his left wrist.

The authors’ observations

B presented with new-onset neurologic findings after a recently diagnosed upper respiratory viral illness. His symptoms appeared to be confined to his left upper extremity, specifically demonstrating left arm extension at the elbow with flexion of the left wrist. He also had new-onset unsteady gait with a stooped forward posture and required assistance with walking. Interestingly, despite B’s history of antipsychotic use, administering an anticholinergic agent did not lessen the dystonic posturing at his wrist and elbow.

EVALUATION Laboratory results reveal new clues

While in the ED, B undergoes MRI of the brain and spinal cord to rule out any mass lesions that could be impinging upon the motor pathways. Both brain and spinal cord imaging appear to be essentially normal, without evidence of impingement of the spinal nerves or lesions involving the brainstem or cerebellum.

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