Kyste arachnoïdien du sinus sphénoïdal: diagnostic différentiel d’une mucocèle

We here report the case of a 45 year old patient, with no previous history of head injury, presenting with isolated intermittent headache which had evolved since the young age. Clinical examination was normal. Cerebral CT scan showed osteolytic expansive hypodense lesion of the sphenoidal sinus extending inferiorly into the infratemporal fossa and superiorly into the temporal fossa (A). This mass wasn’t contrast enhanced. A mucocele was suspected. MRI was performed which showed that the mass had the same enhancement as the cerebrospinal fluid (CSF) and was in continuity with the temporal meninx, without modification in the cerebral parenchyma (B, C). The diagnosis of arachnoid cyst was retained. Given the extension of the cyst and the absence of nerve paralysis, therapeutic abstention as well as clinical and radiological monitoring were performed. Cystic lesions expanding from the sphenoid sinus are relatively rare and can cause non-specific symptoms. Even though these lesions are very rare they should be suspected. Quite often, diagnosis can be determined by CT scan data associated with MRI with diffusion-weighted sequence data, allowing the differential diagnosis of other injuries, in particular mucocele.