Could she have Lyme disease?
Audrey, a previously well nine-year-old girl, presents to her local emergency department with sudden-onset unilateral facial weakness.
One month earlier, she had been bitten on the neck by a tick while in France.
The next day, Audrey developed flu-like symptoms, which rapidly resolved over 24 hours.
Ten days later, a rash developed at the site of the tick bite.
The rash was macular, erythematous and pruritic, with 2-3 small vesicles, but no eschar. She was treated by her GP with 10 days of oral sulfamethoxazole and trimethoprim, with associated slow improvement in the rash.
Examination and investigation
On examination in the ED, Audrey has a complete left-sided unilateral facial nerve palsy, with a lower motor neuron pattern.
The remainder of the neurological examination is normal.
There are no vesicles in the ear canal and no other rash. The tympanic membranes are intact and non-inflamed. There is non-tender posterior chain cervical lymphadenopathy.
Blood tests in ED show a normal CRP (<0.3mg/L) and full blood count.
Management and progress
In ED, Audrey is diagnosed with Bell’s palsy and treated with 1mg/kg/day of prednisone for 10 days. The facial nerve palsy resolves in three days.
Two days after completing the course of prednisone, Audrey develops lower back pain, severe enough to wake her at night, along with fatigue.
There is no headache, photophobia, neck pain or stiffness.
She is reviewed again by her GP, who suspects Lyme disease and starts doxycycline 100mg, bd orally. Screening serology for Borrelia burgdorferi is positive.
A confirmatory Lyme Western blot is positive for all three species tested (Borrelia burgdorferi, Borrelia afzelii, Borrelia garinii), likely due to cross-reactivity among the species or mixed infection.
She is reviewed by an infectious diseases physician who recommends a 14-day course of doxycycline.
She tolerates this well with complete resolution of back pain and fatigue.
Lyme disease is a spirochetal infection transmitted by the bite of infected Ixodes ricinus complex ticks.
Borrelia burgdorferi and Borrelia mayonii are the causes of Lyme disease acquired in North America, while Borrelia afzelii and Borrelia garinii are the leading causes of Lyme disease in Europe and North Asia.
Infection is most common in spring and summer when nymphal ticks, the primary vectors of Borrelia spp. are most actively biting.
The clinical stages of Lyme disease are analogous to those of syphilis, another spirochetal infection.
The stages, in order of progression, are early localised disease, early disseminated disease and late disease.
However, overlap can occur between stages, especially between early localised and early disseminated disease.
Early localised disease is characterised by erythema migrans, which appears at the site of the tick bite 1-2 weeks later.
While classic erythema migrans has a characteristic ‘bull’s eye’ appearance, the rash can be uniformly erythematous and not circular, particularly early in the course.
Patients may describe a burning sensation or pruritus. Vesicles are a rare association. Importantly, early localised Lyme disease is a clinical diagnosis.
The sensitivity of acute serological testing is only 20-50%, rising to only 67% in the convalescent phase if antibiotics have been given.
Early disseminated disease occurs weeks to months after the initial tick bite.
Clinical manifestations include cranial nerve palsy, especially isolated facial nerve palsy, multiple erythema migrans, meningitis, radiculopathy (rare in children) and carditis.
Pseudotumour cerebri has also been described in children. Headache, fatigue, arthralgia and fever are common.
In the absence of a clear history of erythema migrans, the diagnosis of Lyme disease in a patient with isolated facial nerve palsy can be difficult.
While serology is positive in more than 90% of patients with early disseminated disease, there can be a delay of up to a month to serological positivity after the onset of facial nerve palsy.
Lumbar puncture is only recommended if there is a strong clinical suspicion of meningitis or encephalitis.
Late Lyme disease occurs months to years after the tick bite and most commonly causes arthritis of the large joints, especially the knee.
Other manifestations include Lyme encephalopathy, chronic axonal polyneuropathy and, in disease acquired in Europe, chronic encephalomyelitis and acrodermatitis chronica atrophicans.
The sensitivity of serology for late disease approaches 100%.
A 14-28 day course of oral doxycycline 100mg bd (2mg/kg/dose bd for children aged eight and over up to 100mg/dose) is the recommended treatment for isolated facial nerve palsy secondary to Lyme disease.
For pregnant and breastfeeding women and those under the age of eight, use amoxycillin or cefuroxime.
Intravenous antibiotics (for example, ceftriaxone) for 14-28 days are recommended for the other acute neurological manifestations of Lyme disease, such as meningitis and radiculitis.
Antibiotic therapy does not have a significant impact on the natural history of Lyme-disease associated facial nerve palsy, which has a median recovery time of one month.
Nevertheless, antibiotics are recommended to prevent other complications of disseminated Lyme disease. Glucocorticoids do not impact on time to recovery and are not recommended.
Dr Jim Newcombe is a paediatrician, infectious diseases physician and clinical microbiologist at Royal North Shore Hospital and Douglass Hanly Moir, Sydney.
Dr Bernard Hudson, Royal North Shore Hospital, Infectious Diseases Physician and Microbiologist, is acknowledged for his expert review of this article.