Tick paralysis
Tick paralysis is an acute ascending flaccid paralysis caused by a salivary neurotoxin from a female tick that has been feeding for several days; it mimics Guillain-Barre syndrome but evolves over hours to two days rather than weeks. The diagnosis is clinical, cerebrospinal fluid protein is normal, and the definitive treatment is a systematic skin search that finds and removes the tick.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
A neurotoxic envenomation, not an infection: an acute ascending flaccid paralysis caused by a salivary neurotoxin from a female hard tick attached and feeding for several days, distinct from the…
- Epidemiology
Young children, most often girls, are disproportionately affected, largely because long or thick hair conceals an attached scalp tick longer than in boys or adults.
- Risk factors
Prolonged tick attachment, since toxin delivery requires several days of feeding by an engorging female; a tick attached only hours does not cause this syndrome.
- Pathophysiology
The toxin targets the presynaptic terminal of the motor neuron, interfering with calcium-dependent release of acetylcholine-containing vesicles so neuromuscular transmission fails despite an intact postsynaptic receptor.
- Clinical features
An afebrile, symmetric, ascending flaccid paralysis that begins in the lower extremities with an unsteady, ataxic gait, then ascends to the trunk, upper limbs, and, in advanced cases, bulbar and respiratory muscles.
- Differential diagnosis
Guillain-Barre syndrome, including the Miller Fisher variant: shares ascending flaccid weakness, areflexia, and, in Miller Fisher, ataxia and ophthalmoplegia, but evolves over days to weeks, not…
- Diagnosis
First, the diagnosis is established clinically by finding an attached, engorging tick on a patient with an acute, afebrile, ascending flaccid paralysis with areflexia and preserved sensation; if no…
- Management
First, while simultaneously assessing airway, breathing, and oxygenation, perform a systematic, head-to-toe skin and hair examination to find every attached tick, since this single step is both diagnostic and curative.
- Complications
Respiratory failure requiring mechanical ventilation, the dominant cause of death, following ascending progression to diaphragmatic and bulbar weakness in a patient whose tick was never found.
- Prognosis
Excellent once the tick is found and removed: in North America, Dermacentor-associated paralysis characteristically begins improving within hours of removal and resolves within about a day, with no residual weakness.
- Prevention
Perform a full-body tick check after any outdoor exposure in wooded, brushy, or grassy terrain, focusing on the scalp and hairline, behind the ears, the neck, the axillae, the groin, the waistband, and behind the knees.
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Guillain-Barre syndrome
Guillain-Barre syndrome is an acute, post-infectious autoimmune polyradiculoneuropathy causing rapidly progressive ascending flaccid weakness and areflexia. Diagnosis is clinical, supported by albuminocytologic dissociation on CSF and demyelinating changes on electrodiagnostic studies; first-line treatment is IVIG or plasma exchange with close monitoring for respiratory failure.
- Botulism
Botulism is a descending, symmetric flaccid paralysis caused by Clostridium botulinum neurotoxin, which blocks presynaptic acetylcholine release at the neuromuscular junction and autonomic synapses. Diagnosis is clinical, supported by toxin assay of serum, stool, or wound, and management is early antitoxin administration plus supportive respiratory care, since antitoxin halts progression but does not reverse existing paralysis.
- Myasthenia gravis
Myasthenia gravis is an autoimmune disorder of the postsynaptic neuromuscular junction, most often caused by acetylcholine receptor antibodies, producing fluctuating, fatigable weakness of ocular, bulbar, and limb muscles. Diagnosis rests on antibody testing and electrodiagnostics; first-line treatment is pyridostigmine, with glucocorticoids and steroid-sparing immunosuppression for generalized disease and thymectomy for eligible patients.
- Lyme disease
Lyme disease is a tick-borne spirochetal infection caused by Borrelia burgdorferi that progresses from erythema migrans through early disseminated cardiac and neurologic disease to late arthritis, diagnosed clinically when erythema migrans is present and otherwise by two-tiered serology, and treated with staged doxycycline, amoxicillin, or cefuroxime regimens.
- Rocky Mountain spotted fever
Rocky Mountain spotted fever is the most common and most severe spotted fever rickettsiosis in the United States, caused by Rickettsia rickettsii and transmitted by the dog tick. The hallmark petechial rash typically lags days behind fever onset, so empiric doxycycline must be started on clinical suspicion alone, since treatment delay drives the disease's disproportionate mortality.
- Poliomyelitis
Poliomyelitis is caused by poliovirus, a fecal-orally transmitted picornavirus that destroys anterior horn motor neurons after hematogenous spread from the gut, producing asymmetric lower motor neuron flaccid paralysis in under 1% of infected people. Diagnosis rests on the clinical picture supported by cerebrospinal fluid lymphocytic pleocytosis and isolation of the virus from stool or throat secretions, treatment is supportive with ventilatory support for respiratory muscle involvement, and prevention is universal inactivated poliovirus vaccination in childhood.
- Transverse myelitis
Transverse myelitis is inflammation across one or more contiguous spinal cord segments causing subacute weakness, a sensory level, and bladder or bowel dysfunction; diagnosis requires spinal MRI showing cord enhancement or CSF inflammation with exclusion of compressive and infectious causes, and idiopathic disease is treated with high-dose intravenous methylprednisolone.
- Spinal cord compression
Spinal cord compression is mechanical narrowing of the spinal canal by tumor, hematoma, abscess, disc herniation, or trauma that produces myelopathy; it is a neurologic emergency requiring urgent MRI of the affected level and immediate treatment of the cause, since surgical decompression rarely restores function once paraplegia develops.