Neurology · Neuromuscular Disorders
The facts most likely to be tested
Tick paralysis is caused by a neurotoxin in the saliva of a female tick, most commonly *Dermacentor* species.
The clinical presentation is an acute, ascending, symmetric flaccid paralysis that mimics Guillain-Barré syndrome.
Patients typically lack fever and sensory deficits, which helps distinguish this condition from other infectious or inflammatory neuropathies.
The deep tendon reflexes are characteristically absent or diminished in the affected extremities.
The definitive treatment is the complete removal of the tick, which usually leads to rapid clinical improvement within 24 hours.
Failure to remove the tick can lead to respiratory failure and death due to bulbar muscle paralysis.
A thorough skin examination, particularly of the scalp and hair-bearing areas, is mandatory to locate the embedded tick.
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A 6-year-old girl is brought to the emergency department by her parents due to a 2-day history of progressive weakness starting in her legs and moving upward. The parents report she has been irritable and unsteady on her feet, but she has had no fever, cough, or recent viral illness. On physical examination, she has symmetric 2/5 strength in the lower extremities and absent deep tendon reflexes bilaterally. Her sensory exam is intact, and cranial nerve function is normal. A careful inspection of her scalp reveals a firm, engorged tick attached to the skin behind her right ear.
What is the most appropriate next step in management?
Complete removal of the tick
The patient presents with classic signs of tick paralysis, which is a toxin-mediated process; the most important intervention is the immediate removal of the offending tick to halt toxin production.
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Etiology / Epidemiology
Caused by neurotoxin in tick saliva; most common in children during spring/summer.
Clinical Manifestations
Rapidly progressive ascending flaccid paralysis; afebrile presentation is classic.
Diagnosis
Clinical diagnosis; tick search is the gold standard for confirmation.
Treatment
Tick removal is curative; symptoms resolve within 24 hours.
Prognosis
Excellent recovery if caught before respiratory failure.
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Epidemiology & Etiology
Primarily caused by *Dermacentor* species in North America. Occurs most frequently in children due to higher toxin-to-body-mass ratio. Exposure typically occurs in wooded or grassy areas during peak tick season.
Pertinent Anatomy
The toxin acts at the neuromuscular junction and peripheral nerves. It does not affect the central nervous system, explaining the preservation of sensorium.
Pathophysiology
The tick secretes a neurotoxin that inhibits the release of acetylcholine at the presynaptic terminal. This results in a failure of nerve impulse transmission to the muscle. The process is reversible once the source of the toxin is removed.
Clinical Manifestations
Patients present with ascending flaccid paralysis that mimics Guillain-Barré syndrome. Key features include loss of deep tendon reflexes and an afebrile state. Respiratory failure is the primary life-threatening complication if the paralysis reaches the diaphragm.
Diagnosis
Diagnosis is strictly clinical. The gold standard is a meticulous full-body skin exam to locate and remove the tick. No specific laboratory or imaging tests are required for confirmation.
Treatment
The definitive treatment is complete tick removal. Symptoms typically show rapid improvement within 24 hours. Supportive care including mechanical ventilation may be required if the patient presents with advanced respiratory compromise.
Prognosis
Prognosis is excellent with full recovery expected shortly after tick removal. The primary risk is respiratory failure if the diagnosis is delayed.
Differential Diagnosis
Guillain-Barré syndrome: usually preceded by viral illness or Campylobacter
Botulism: presents with descending paralysis and cranial nerve involvement
Myasthenia gravis: characterized by fatiguability and ptosis
Spinal cord compression: associated with sensory levels and bowel/bladder dysfunction
Polio: associated with fever and asymmetric weakness