Vertebral Hemangioma

Introduction

Vertebral hemangiomas (VHs) are benign vascular tumors frequently encountered as incidental findings on computed tomography (CT) or magnetic resonance imaging (MRI). The vast majority are quiescent, with classic imaging features that are reassuring to radiologists and patients, and are called typical hemangiomas. VHs that are clinically quiescent but do not demonstrate classic imaging features are frequently referred to as atypical hemangiomas. These may produce a diagnostic challenge, requiring additional diagnostic tests and potentially even confirmatory biopsy but incur little risk to the patient. A small percentage of VHs can display active behavior, demonstrating aggressive imaging features that can mimic primary bone malignancies or metastases. These “aggressive hemangiomas” are frequently clinically symptomatic, resulting in pain or neurologic compromise. Treatment options vary by patient and institution, but most commonly include radiotherapy and/or surgery.

Evolution: Overview

According to a large autopsy and radiography study, VHs are present in 10% to 12% of the adult population, but this is likely an underestimate because MR can now detect an extremely large number of small VHs. Histologically, VHs are composed of capillary or cavernous blood vessels, lined by a single layer of flat endothelial cells set in a loose, edematous stroma. These vessels permeate bone marrow and surround preexisting trabecula. Secondary reactive phenomena, such as fatty or fibrous involution of bone marrow, frequently occur ( Fig. 29.1 ). Although the exact mechanism for hemangioma formation and growth has yet to be discovered, studies have cited the importance of local tissue ischemia and estrogen signaling in promoting vasculogenesis.

Typical hemangiomas reflect the histology, demonstrating low attenuation interspersed between vertically oriented bony trabecula on CT, and hyperintense signal on T1- and T2-weighted MR images due to their fatty content ( Fig. 29.2 ). These are considered incidental and inconsequential, requiring no further diagnostic work-up or routine follow-up. Atypical hemangiomas have less fatty and greater vascular content, thereby demonstrating reduced T1 signal. Although this may produce a diagnostic challenge, CT showing vertically oriented trabecula will frequently aid in establishing lesions as benign. If discovered incidentally and clinically asymptomatic, atypical VHs also require no further work-up. Aggressive VHs comprise a small subset (1%) of all VHs, in which fat becomes replaced by vascular stroma. On imaging, this results in background soft tissue attenuation on CT and hypointense T1 signal on MR. Additional aggressive imaging features may also be present and include involvement of the entire vertebral body, extension into the neural arch, cortical expansion, and an associated soft tissue mass. Patients with aggressive VHs frequently become symptomatic, with lesions producing pain (55%) or neurologic deficits (45%). Recognizing remnant bony trabeculation on CT will provide the best chance at arriving at the correct preoperative diagnosis ( Fig. 29.3 ).