Cat-scratch disease is caused by a systemic infection with Bartonella henselae, a bacteria colonizing cat saliva. The infection typically presents as a skin lesion at the site of a cat scratch with ensuing local lymphadenopathy. Infection is manifested by lymphadenopathy, but infected individuals may display fever, fatigue, anorexia, or headaches. It is most commonly a pediatric disorder, affecting individuals usually younger than 21 years of age. Neurologic involvement is estimated to affect 2% to 3% of patients, presenting as encephalopathy, seizures, cerebellar ataxia, hemiparesis, myelitis, or cranial neuropathies. Curiously, neurologic involvement has an increased incidence in adult patients. Facial nerve involvement is considered rare (65).
The mechanism of facial nerve involvement remains unclear. Parotid enlargement is found in 3% of cases and may cause direct involvement of the peripheral branches of the facial nerve (66). Other authors have theorized direct invasion due to the granulomatous lesions around the facial nerve (67). Alternatively, the bacteria could have a direct effect on the facial nerve or cause injury to the nerve secondary to edema along its course within the temporal bone.
Diagnosis is made clinically and confirmed using serologic titers for antibodies to B. henselae. Histopathologic findings are not diagnostic but typically demonstrate microabscesses with necrotic centers surrounded by epithelioid cells. Warthin-Starry staining can identify the causative bacterium. Treatment of the infection is symptomatic. Suppurative lymphadenopathy is treated by aspiration. The prognosis for facial nerve recovery is considered good, but too few cases exist for meaningful data to be extrapolated.
Chapter 11 contains a detailed discussion of cat-scratch disease.
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