sphenoid wing dysplasia
Sphenoid wing dysplasia is a characteristic but not pathognomonic feature of neurofibromatosis type 1 (NF1), it can also occur in isolated cases.
Sphenoid wing dysplasia is seen in 5-10% of cases of NF1 and is one of the diagnostic criteria of NF1 .
Its exact etiology is not clear. It can be seen isolated or associated with underlying plexiform neurofibroma.
- hypoplastic/absent sphenoid wing resulting in widening of the superior orbital fissure, elevation of the lesser sphenoid wing and ipsilateral orbital enlargement
- gapping bony defect in the posterior aspect of the orbit
- absence of the innominate line (which represents the projection of the greater wing of the sphenoid bone) on plain radiograph and CT scan giving the bare orbit sign
- expansion and anteroposterior enlargement of the middle cranial fossa, usually associated with anterior temporal arachnoid cysts
- herniation of the dura, peritemporal subarachnoid space or the temporal lobe into the posterior aspect of the orbit, causing anterior displacement of the orbital contents