Orbital frontal nerve schwannoma-distinctive radiological features

This retrospective study catalogued the imaging characteristics of people with orbital frontal nerve schwannoma.

Study design

The authors reviewed neuro-imaging characteristics of 13 patients with orbital frontal nerve schwannoma who underwent surgical excision following preoperative imaging.

Outcomes

The majority (84.6%) of frontal nerve schwannomas extended between the supraorbital notch and superior orbital fissure. The most common shape seen in patients with frontal nerve schwannoma was a multilobulated "beaded" appearance (46.2%), followed by dumbbell (30.8%), oval (15.4%) and fusiform (7.7%) shapes.

On CT imaging, all patients had bony remodeling. Target sign, fascicular sign and cystic degeneration were seen in 76.9%, 35.8% and 46.2% of patients, respectively. On radiological-pathologic correlation, the zone of tightly packed cellular solid portion (Antoni A pattern) corresponded to the hypointense area on T2-weighted MRI and the hyperintense area on gadolinium-enhanced T1-weighted MRI.

Limitations

This study was limited by its retrospective nature and small sample size. Furthermore, CT scans were not available for all patients, though all patients underwent MRI.

Clinical significance

This study describes radiological findings that can facilitate an accurate diagnosis of frontal nerve schwannomas, including multilobulated beaded or dumbbell shape, the target and fascicular signs, and cystic degeneration.