A 12-year-old boy is brought to the emergency department due to unsteadiness, weakness, and falls. The patient recently went on a week-long family camping and hiking trip to the mountains in Washington State. On returning home to California 2 days ago, he experienced a sense of fatigue and a tingling sensation in his fingers. Yesterday, the patient started having bilateral leg weakness and is now unable to walk without assistance; he sways from side to side when standing and then falls to the floor. The patient has had no fever, headache, joint pain, or skin rash and has no history of recent respiratory or gastrointestinal illness. Vital signs are within normal limits. He is alert and active but can stand only briefly before requiring assistance. There is no increased resistance to neck flexion. Cranial nerve examination is normal and sensation is not impaired. Muscle strength is 4/5 in the upper extremities and 2/5 in the lower extremities. Deep tendon reflexes are absent at the knees and ankles but are normal elsewhere. Finger-to-nose testing shows dysmetria of the arms. Item 1 of 2
Which of the following is the best next diagnostic intervention that should be performed for this patient?

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Quizplus · Accepted Answer

Explanation: This patient with ataxia, weakness, and absent deep tendon reflexes after a camping trip to Washington State most likely has tick paralysis. Tick paralysis is a rare, potentially life-threatening disorder seen primarily in Australia and Western North America. Although more than 40 species of ticks can cause tick paralysis, most cases in North America are due to Dermacentor andersoni (Rocky Mountain wood tick) and D variabilis (American dog tick). Neurotoxins in the tick saliva are transmitted to the host over 4-7 days of tick attachment and result in: A brief prodrome of fatigue and paresthesias Gait ataxia and ascending paralysis that develop over hours Absent deep tendon reflexes Fever is typically absent and sensation is rarely affected. Laboratory and imaging studies are usually normal. Patients with suspected tick paralysis require a meticulous skin examination to identify the tick. (Choices A and C) Electrodiagnostic studies and cerebrospinal fluid analysis (elevated protein with normal leukocytes) are often obtained to support the diagnosis of Guillain-Barré syndrome. This syndrome causes ascending paralysis with absent deep tendon reflexes, but usually follows a gastrointestinal or respiratory infection and typically progresses over several days or weeks (rather than hours). This child who recently camped in the woods should first be examined meticulously for ticks to rule out tick paralysis. (Choice B) A spinal cord lesion can cause motor dysfunction and diminished deep tendon reflexes. However, sensation is likely to be affected, and most etiologies (eg, infection, tumor) result in slowly progressive symptoms over several days or weeks (not hours). (Choice E) Clostridium botulinum toxin can be found by serum analysis. Botulism usually causes an afebrile, descending paralysis starting with the cranial nerves. This patient with motor weakness of the legs and normal cranial nerves is unlikely to have botulism. Educational objective: Tick paralysis is a rare, potentially life-threatening disorder caused by neurotoxins found in tick saliva. Manifestations typically arise after 4-7 days of tick attachment and include rapidly progressive gait ataxia and ascending paralysis. Neurologic examination usually reveals absent deep tendon reflexes and normal sensation. Fever is uncommon. A meticulous skin examination to identify the tick is required. References: Tick paralysis. (http://www.ncbi.nlm.nih.gov/pubmed/20842579) Tick paralysis. (http://www.ncbi.nlm.nih.gov/pubmed/15257515) A 60-year meta-analysis of tick paralysis in the United States: a predictable, preventable, and often misdiagnosed poisoning. (http://www.ncbi.nlm.nih.gov/pubmed/20186584)

A 12-Year-Old Boy Is Brought to the Emergency Department Due