This is a large case series of orbital Schwannomas managed at a single centre over a 26-year period. Twenty Schwannomas are reported, all but one of which was managed surgically. The tumours were all benign, had an insidious onset and typically presented with proptosis. Less frequent symptoms included discomfort, blurring and diplopia. They were most commonly located within the superior orbit and the mean size was 25mm. Six extended through the superior orbital fissure and 40% involved the orbital apex. Most were on sensory nerves (50% frontal, 20% lacrimal) but three originated from motor nerves. CT imaging showed well-defined homogenous lesions isodense to brain with minimal enhancement. On MRI, Schwannomas tended to be isointense on T1 and hyperintense on T2, enhance more avidly with gadolinium than on CT, but showed a wide spectrum of appearances which varied with the age of the lesion and the histological sub-type. Antoni type A lesions were hypercellular with tightly packed spindle cells and were hyperintense on T1, whereas Antoni type B had loosely packed myxoid cells and were hypointense on T1 imaging. The overall shape varied from round to lobular, dumb-bell and multi-lobular. A quarter had cystic changes. One patient refused surgery and underwent stereotactic fractionated radiotherapy with improvement in vision. All others underwent surgical resection, which included image-guided neurosurgery where there was intracranial extension. Complete resection was achieved in 11 patients. Following surgery, two patients had significant improvement in visual acuity, one was significantly worse, and overall mean acuity was unchanged. Although previous studies have reported surgical complications including loss of vision, diplopia, globe dystopia and cerebrospinal fluid (CSF) leaks, the outcomes in this series were generally favourable and interestingly only one patient had persistent paraesthesia. Previous study authors also found this and have suggested this may be due to the lesions arising from minor sensory branches. This is a comprehensive case series, and the authors conclude early surgical intervention is more likely to produce a good outcome even if there is optic neuropathy of recent onset. The role of radiotherapy remains uncertain.
Orbital Schwannomas
Reviewed by James Hsuan
Orbital Schwannomas – Management and clinical outcomes.
