Tick Paralysis

Tick Paralysis

Ascending paralysis naturally evokes concern for Guillain-Barre syndrome, but one entity that should be on your differential and requires special action is Tick Paralysis.  Let’s take a minute to refresh our memories about this interesting and important condition.


  • Prodrome con be seen and generally lasts < 24 hours.
    • Restlessness and Irritability
    • Fatigue
    • Paresthesias
    • Myalgias
    • Fever is seldom present
  • Acute symmetric ascending flaccid paralysis.
    • Unsteady gait can be the initial finding.
    • Usually develops 2-6 days after tick attachment (so consider where the patient may have been over the past several days).
    • Decreased deep tendon reflexes.
  • Progressive Ascending Weakness if the tick continues to feed.
    • Can see weakness of upper extremities.
    • Cranial nerve involvement can also be seen – drooling, dysphagia, dysphonia, and facial weakness.
    • Opthalmoplegia and pupillary dilation have been reported.
    • Atypical presentations have noted focal weakness or isolated facial weakness or isolated cerebellar ataxia.
  • Involvement of the respiratory muscles can occur.
    • Without supportive care, can lead to death.
    • Historically, 6% of patients with tick paralysis died.


Risk Factors

  • Girls with long hair
  • < 8 years of age
  • Spring and Summer months
  • Regions:
    • Australia (Ixodes holyclus)
    • North America
      • Rocky Mountain region, Pacific Northwest, Southwest Canada (Dermacentor andersoni)
      • Southeast region (Dermacentor variabilis)



  • The paralysis is caused by a neurotoxin that is produced in the tick’s salivary glands.
  • The exact mechanism is not fully characterized.
  • Believed to decrease the presynaptic acetylcholine release at the neuromuscular junction.
  • May function similar to botulinum toxin.


Other Diagnoses Often Confused with Tick Paralysis

Naturally, evaluating a patient who presents with acute ascending weakness with hyporeflexia will generate concern for the following, and Tick Paralysis is important to consider as well.  When you are considering any of these conditions, you should look closely for any attached ticks and ask about potential exposure.  22% of cases in the USA were initially misdiagnosed and the mean time for correct diagnosis was >2 days.

      • Botulism
      • Guillain-Barre Syndrome
      • Myasthenia gravis
      • Lambert-Eaton syndrome
      • Diptheria
      • Poliomyelitis
      • Transverse myelitis
      • Periodic paralysis
      • Spinal Cord Compression
      • Heavy metal poisoning
      • Organophosphate poisoning



  • Tick paralysis is diagnosed based on clinical findings concurrent with discovering an engorged tick.
  • There is not a specific test that is advocated to confirm the diagnosis.
  • Laboratory studies and imaging is often done to rule out other entities.
    • This is why considering Tick Paralysis and performing a Tick Check is important.
    • There are known cases of MRIs being done for the evaluation of the weakness only to demonstrate an engorged tick (kinda creepy really– but also a waste of money to obtain an MRI of a Tick — ticks don’t have insurance).
    • CSF studies are normal.



  • Simple – remove the tick
    • With Dermacentor ticks, the symptoms tend to improve shortly after removal.
    • With Ixodes ticks, the symptoms may persist for 1 – 2 days after removal.
    • Some cases of prolonged symptoms have been noted in Australia.


Moral of the Morsel

Keep Tick Paralysis on your DDx when evaluating a patient with acute weakness and look closely for any attached ticks, as this may dramatically alter your potentially expensive and expansive evaluation.



Taraschenko OD1, Powers KM2. Neurotoxin-induced paralysis: a case of tick paralysis in a 2-year-old child. Pediatr Neurol. 2014 Jun;50(6):605-7. PMID: 24679414. [PubMed] [Read by QxMD]

Chagnon SL1, Naik M, Abdel-Hamid H. Child neurology: tick paralysis: a diagnosis not to miss. Neurology. 2014 Mar 18;82(11):e91-3. PMID: 24638220. [PubMed] [Read by QxMD]

Pecina CA. Tick paralysis. Semin Neurol. 2012 Nov;32(5):531-2. PMID: 23677663. [PubMed] [Read by QxMD]

Sean M. Fox
Sean M. Fox

I enjoy taking care of patients and I finding it endlessly rewarding to help train others to do the same. I trained at the Combined Emergency Medicine and Pediatrics residency program at University of Maryland, where I had the tremendous fortune of learning from world renowned educators and clinicians. Now I have the unbelievable honor of working with an unbelievably gifted group of practitioners at Carolinas Medical Center. I strive every day to inspire my residents as much as they inspire me.

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