A radiological classification system for intraneural vascular anomalies: assessment of potential for resection with high-resolution MRI.

Background: Intraneural hemangiomas and vascular malformations are rare, with approximately 50 cases reported in the literature. They present a therapeutic challenge; surgical resection can result in damage to the nerve and lesion recurrence is common. We introduce a new framework to classify intraneural vascular anomalies in relation to the anatomic compartments of the nerve and assess amenability to surgical resection.

Methods: We retrospectively reviewed cases of intraneural hemangiomas and vascular malformations treated at our institution between 2003 and 2013 that had high-resolution 3-T magnetic resonance imaging (MRI). A review of the literature was also performed. Our cases and reports in the literature with available MRI data were sub-categorized according to their relationship to the paraneurium and epineurium of the nerve.

Results: Nine patients were identified with intraneural (subparaneurial or subepineurial) vascular lesions. Two patients had a predominantly subparaneurial involvement of the nerve, six patients had predominantly subepineurial involvement, and one patient exhibited extensive involvement in both compartments. Four patients were managed surgically and the rest conservatively. Targeted resection of two subparaneurial hemangiomas provided complete relief of symptoms and freedom from recurrence at 18 month and 24 months respectively. One patient with extensive subepineurial and extraneural vascular malformations did not appear to benefit from sub-total resection with interfascicular dissection. No surgical morbidity was noted in any of the cases.

Conclusions: We believe that the subparaneurial compartment-a potential space between the epineurium and paraneurium-provides a tissue plane within which benign vascular lesions can occur. Hemangiomas and vascular malformations are complex and can occupy different intraneural and extraneural compartments. The anatomic framework aids surgical decision-making and ensures that all components of the lesion are considered. We advocate a multimodal approach in the treatment of these rare lesions.