Diagnostic difficulties in a patient with multiple sclerosis who presents with cranial nerve palsies: an unusual complication of dental work.

A woman in her 60s with multiple sclerosis (MS) presented with right-sided ptosis, right sixth nerve palsy, right facial paraesthesia and signs of sepsis. She had a recent diagnosis of a dental abscess. Investigations revealed a right submasseter abscess leading to bacterial meningitis (Streptococcus intermedius) and a cavernous sinus thrombosis. She was managed in intensive care and underwent surgical drainage of the abscess. Anticoagulation for 6 months was planned. Cavernous sinus thrombosis is a very rare complication of a dental abscess, and even less frequently associated with submasseter abscesses. The case was complicated by a history of MS, to which the patient's symptoms and signs were initially attributed to. This case highlights the diagnostic pitfalls, and aims to enhance learning around similar cases. To the best of our knowledge, this is the first case report of a masseter/submasseter abscess leading to cavernous sinus thrombosis.