Arrested pneumatization of sinus sphenoid, revealed by hypo-acusis: A case report

The sphenoid bone is a complex structure in terms of its embryological origin. At birth, the sphenoid sinus is not pneumatised. Pneumatisation begins at around 4 months of age until the age of 12-14 years. If this process is absent or interrupted for reasons that are often unknown, it is called arrested pneumatisation. This report describes the case of a 15 year old patient, who consulted an ENT specialist for chronic headaches and hearing loss on the left side. Clinical ENT examination (including otoscopy) is normal. Tonal audiometry revealed a sensorineural hearing loss in the left ear. A CT scan of the petrous bone was normal but revealed a hypodense lesion in the left sphenoid bone. Lipoma was suggested. A brain MRI was performed in a clinic to better characterize the lesion. MR images showed a well-defined lesion with fatty content. The diagnosis was nasosinus fibrous dysplasia. In view of the diagnostic discrepancy, the patient was referred to our department for a specialist opinion. An additional brain scan revealed a non-eroded, non-expansive fatty density lesion with well-defined internal curvilinear calcification in the left sphenoid sinus location. Our final diagnosis was arrested pneumatisation. Most patients with arrested pneumatization of the skull base are asymptomatic. Sometimes it may be revealed by nonspecific signs and be confused with severe skull base disease, especially if the radiologist is not familiar with its existence or its typical features.