Intracranial actinomycosis of odontogenic origin masquerading as auto-immune orbital myositis: a fatal case and review of the literature

A 58-year-old man presented with diplopia and progressive pain behind his left eye. Six weeks earlier he had undergone a dental extraction, followed by clindamycin treatment for a presumed maxillary infection. The diplopia responded to steroids but recurred after cessation. The diplopia was thought to result from myositis of the left medial rectus muscle, possibly related to a defect in the lamina papyracea. During exploration there was no abnormal tissue for biopsy. The medial wall was reconstructed and the myositis responded again to steroids. Within weeks a myositis on the right side occurred, with CT evidence of muscle swelling. Several months later he presented with right hemiparesis and dysarthria. Despite treatment the patient deteriorated, developed extensive intracranial hemorrhage, and died. Autopsy showed bacterial aggregates suggestive of actinomycotic meningoencephalitis with septic thromboembolism. Retrospectively, imaging studies showed abnormalities in the left infratemporal fossa and skull base and bilateral cavernous sinus.

In conclusion, intracranial actinomycosis is difficult to diagnose, with potentially fatal outcome. An accurate diagnosis can often only be established by means of histology and biopsy should be performed whenever feasible. This is the first report of actinomycotic orbital involvement of odontogenic origin, presenting initially as bilateral orbital myositis rather than as orbital abscess. Infection from the upper left jaw extended to the left infratemporal fossa, skull base and meninges and subsequently to the cavernous sinus and the orbits.