Authors
Kathryn Lewis, BS, Mehul Patel, MD, Naveen Jayakumar, MD
Introduction
Tick paralysis is a rare cause of paralysis in the general population. The purpose of this clinical vignette is to broaden our differential diagnosis for ataxia and explore a rare presentation of paralysis.
Case Presentation
An 88 year old male with dementia, dyslipidemia, and status-post cochlear implantation presented to a community hospital after new onset gait instability. The patient was on a road trip from Wisconsin when he developed an inability to walk at dinner after arriving in the Coachella Valley. The patient was unable to ambulate and experienced worsening instability in his trunk. History was negative for atrial fibrillation, transient ischemic attacks, and strokes. Given progressive truncal ataxia, patient was admitted for suspected cerebellar stroke.
On exam, patient was alert and oriented to person, place, and time without sensory or cranial nerve deficits. Strength was 5/5 in all limbs, and exam was remarkable for ataxia of the trunk with instable gait. CT revealed stable age-related atrophy without evidence of acute ischemia or hemorrhage. Complete evaluation for cerebellar stroke was limited as MRI could not be done due to cochlear implantation.
Three days into admission, a tick was found on the left lateral chest wall with surrounding ecchymosis during bathing. Upon further questioning, the patient reported hotel stays and visiting national parks throughout his travels. He denied animal exposures, camping, and use of insect repellant. Following tick removal, truncal ataxia dramatically improved. Patient worked with physical therapy for an additional two days and was discharged without ataxia.
Discussion
Tick paralysis is a rare condition caused by the release of neurotoxins by female Dermacentor ticks in the United States. Most cases are reported from April to June in the Rocky Mountains and Pacific Northwest. Classically, paralysis is preceded by a nonspecific prodromal phase marked by fatigue, fever, and generalized weakness. Paralysis develops 4-7 days after the bite, known as the neurotoxic phase. While most patients present with ascending paralysis, other presentations include ophthalmoplegia and quadriplegia. Full recovery of paralysis has been reported within 24-48 hours of tick removal1.
This case highlights a unique presentation of tick paralysis as the patient presented with truncal ataxia, without evidence of ascending paralysis or other findings on exam. The patient denied previous fever or fatigue, which would be consistent with a prodromal phase. Additionally, the age of diagnosis of tick paralysis is unusual as most patients are young girls with bites along the hairline and neck.
With a presentation of ascending paralysis, tick paralysis is often misdiagnosed as Guillain-Barre Syndrome2. Less frequent misdiagnoses include botulism, encephalomyelitis, and stroke2. This case further illustrates the importance of establishing and considering a broad differential diagnosis for better management and treatment of patients, while also reducing health care costs.
References
- Kleszczowy P. Tick Paralysis. Przegl Epidemiol 2018;72(1): 17-24.
- Diaz, JH. A Comparative Meta-Analysis of Tick Paralysis in the United States and Australia. Clinical Toxicology, 53:9, 874-883.
Back to the February 2020 issue of ACP IMpact