Intrasphenoidal encephalocele
Intrasphenoidal encephaloceles represent encephaloceles which extend into the sphenoid sinus yet confined by its floor
Clinical presentation
Patients present with spontaneous cerebral spinal fluid (CSF) rhinorrhea.
Pathology
Intrasphenoidal encephaloceles are divided into medial perisellar and lateral sphenoid recess encephaloceles
- medial perisellar encephaloceles occur within the sphenoid sinus and are more common
- lateral sphenoid encephaloceles are rare and are usually associated with lateral pneumatization of the sphenoid sinus into the pterygoid recesses
Contributing factors to lateral intrasphenoid encephalocele include arachnoid pits/weaknesses in the skull base and intracranial hypertension
- CSF pressure and the hydrostatic pulsatile forces may lead to the development of pit holes on the middle fossa at the sites of arachnoid villi with herniation of dura/arachnoid or brain tissue
- If those defects are located over pneumatized lateral extension of the sphenoid sinus, encephalocele can develop and lead to CSF leakage into the sinus
Congenital lateral intrasphenoidal encephaloceles occur secondary to the persistence of the Sternberg's canal and are located medial to the foramen rotundum .
Radiographic features
CT
CT cisternography demonstrates sphenoid sinus pneumatization, a defect in the superior wall of the left lateral recess of the sphenoid sinus and anteromedial temporal lobe herniating through the bony defect.
MRI
MR cisternography is a non-invasive technique that can reveal CSF leakage in multiple planes. On T2-weighted spin-echo sequence, the bright CSF signal is well appreciated against the signal void air of the paranasal sinuses .
See also
