Presentation
Left proptosis.
Patient Data
Low-density mass in the left middle cranial fossa with thin peripheral calcification. Extensive expansive cortical thinning and patchy dehiscence of the middle cranial fossa floor, pterion and lesser sphenoid wing.
The mass deforms the posterolateral wall of the left orbit resulting in reduced volume as compared to the right with left proptosis noted. No orbital mass.
Mass effect on the left temporal pole, which is posteriorly displaced. Anterior left temporal lobe volume loss with dilatation of the left temporal horn, and cortical calcification of the posterolateral left temporal lobe.
Widening of the inferior left sylvian fissure with mass effect on the frontal insular.
Left middle cranial fossa mass following CSF signal intensity on all sequences. The left sphenoid wing is expanded anteriorly resulting in the left proptosis. The left middle cerebral artery courses through the posterior aspect of the mass with the M2 branches appear somewhat smaller caliber than the right. Cortical vein courses through the mass inferiorly. Left temporal pole volume loss with dilatation of the temporal horn.
Gyriform low signal intensity of the anterior left temporal lobe in keeping with calcification demonstrated on the prior CT. Post contrast imaging there is adjacent leptomeningeal enhancement.
Mild chronic small ischemic changes within the supratentorial deep white matter. Enhancing left parietal calvarial lesion, not seen on the prior CT, probably an incidental hemangioma.
Case Discussion
Arachnoid cysts are a relatively common intracranial mass, although resulting in proptosis, as in this case, is uncommon.
The adjacent gyral calcification and leptomeningeal enhancement is of unknown origin and any relationship to the arachnoid cyst is uncertain.