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Children with acute peripheral facial palsy have often suffered tick bites and/or erythema migrans in the head/neck region on the same side. With respect to the pathogenesis of neuroborreliosis this topographical association was investigated in an animal model.
A Borrelia garinii strain, isolated from the CSF of a child with acute facial palsy, was injected in 9 rats intracutaneously in the right subauricular region. Infected rats were examined for clinical symptoms of
Lyme disease, the spread of the spirochetes was investigated by PCR of necropsies (facial nerves, trigeminus nerves, heart, brain, skin) up to 47 days after infection. The nerve tissues were investigated by histology, immunohistochemistry and electron microscopy.
None of the rats developed a facial palsy or other symptoms of
Lyme disease. Borrelia DNA was found in the heart after 5 days and in the brain after 7 days of infection up to the end of investigation (47 days), as well as in the ipsilateral peripheral nerves after 7 to 33 days. Borrelia was detected by electron microscopy near endoneural vessels of the facial nerve. Peri-, epi-, and endoneural infiltrations of macrophages, plasma cells and B cells characterized an inflammation of the facial and trigeminus nerves ipsilateral to the infection site.
An infection with Borrelia garinii in the subauricular region induces an ipsilateral neuritis of peripheral nerves. The particular vulnerability of the human facial nerve may be a result of its long intraosseus course. Thus, an inflammatory edema may injure the nerve in the canalis facialis.