Petrous apex cephalocoele

Petrous apex cephalocoele (PAC) is a rare form of cephalocoele centered typically in the posterolateral part of Meckel cave with variable extension into the petrous apex. They can be unilateral or bilateral (commoner).

Epidemiology

There may be a slight female predilection.

Clinical presentation

The lesions are incidentally detected and are asymptomatic most of the times. Though they may present with trigeminal neuralgia, headache, CSF otorrhea, and sensorineural hearing loss.

Associations

Recognized associations include

• empty sella
• Usher syndrome - Graefe-Usher syndrome

Radiographic features

CT

• homogenously low density area is noted in the petrous apex with sharply defined margins

MRI

MRI can demonstrate the continuation with Meckel cave and hence helps in providing a confident diagnosis thereby preventing unnecessary surgical intervention. The signal intensities follow that of CSF.

• T1: hypointense
• T2: hyperintense
• FLAIR: typical CSF suppression 
• DWI: no restriction

Differential diagnosis

As a general differential consider

• petrous apex lesions