Thoracic extraosseous, epidural, cavernous hemangioma: Case report and review of literature

Radiology

Magnetic resonance imaging (MRI) of the thoracic spine revealed an extradural lesion, opposite the T2-T4 vertebral bodies, which was homogenously isointense on T1- and hyperintense on T2-weighted images. The lesion was located dorsally and had compressed the thoracic cords ventrally. The axial sections revealed that the mass was located eccentrically; more on the patient's left side, with a small projection into the intervertebral foramen. The spinal cord at that level could be seen displaced ventrally and to the right. A central hyperintensity on T2-weighted imaging, within the cord substance, was also observed. Of note was the presence of a remote intraosseous T8 vertebral hemangioma. The lesion enhanced avidly and homogenously with contrast [Figure 1]. Computerized tomography (CT) of the upper dorsal spine did not reveal any bony destruction or widening of the intervertebral foramen. A radiological differential of an extradural schwannoma or meningioma was considered.

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Figure 1

a: T2-weighted, mid-sagittal magnetic resonance image revealing a thoracic, hyperintense, solitary, extradural mass (black arrows) opposite the D2-4 vertebral bodies. The signal intensity differs from that of the cerebrospinal fluid, but is similar to that of a remote intraosseous hemangioma within the D8 vertebral body. Axial magnetic resonance images reveal an eccentrically placed dorsal extradural mass (asterisk), which is isointense on T1- (b) and hyperintense on T2- (c) weighted images, with left foraminal extension (black dashed arrow)

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Figure 2

Photomicrograph showing numerous dilated vascular channels filled with blood and separated from each other by fibrous septae. These vascular channels do not communicate with each other (H and E ×200)

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Surgery

The patient underwent a T2-T4 laminectomy. Intraoperatively, the mass was encountered within the epidural fat and immediately beneath the laminae. It was reddish in color, firm, friable, and highly vascular. It was located epidurally, mostly dorsal to the thecal sac, but also extended laterally to the left, along the left T2 nerve root sheath. Its blood supply was derived from the intervertebral foramina on both sides. Initially, the tumor's dorsal surface was devascularized, with bipolar cautery, under the operating microscope. Its arterial feeders were then sequentially cauterized and interrupted, just medial to the intervertebral foramina, taking care not to injure the dorsal nerve roots. The lesion was then peeled off the surface of the dura and the adjacent nerve sheaths. The lesion was excised en bloc. The underlying dura was then opened, taking care to preserve the arachnoid, to ensure total microsurgical excision.

The patient was discharged 48 hours after surgery. His postoperative course was significant for a subjective improvement in spasticity and numbness. The histopathological examination indicated a CH [Figure 2]. On the last follow-up, 12 months after surgery, a check craniospinal MRI confirmed complete excision, with no recurrence at the operative site and no other new lesions. His power and sensations were nearly normal and he had returned to work.

Epidemiology

Cavernous hemangiomas are ubiquitous. Within the central nervous system, they tend to occur predominantly within the cranial cavity's supratentorial compartment.[7] Within the spine, CH are rare. Hillman and Bynke (1991) reported an incidence of 0.22 cases/million/year.[21] Although EECH are supposedly rarer, slightly less than a 100 cases have been reported in the literature to date, since Globus and Doshay first described this entity in 1929.[122] In this specific subgroup, a female preponderance is noted (70%). The average age at diagnosis has been reported to be around 40 years, which is the exact age of our patient. EECH are generally seen in the thoracic spine (60%), and are typically located posterolaterally and may extend into the neural foramina (19%). An extraspinal component may be evident in about 13% of all cases. The most common presentation is that of slowly progressive paraparesis (71%) and radiculopathy (10%).[8101819] Taking all these features into account, our patient had a fairly classical presentation. Rarely, acute paraparesis has also been reported and been ascribed to intralesional thrombosis and/or hemorrhage, with subsequent compression from an epidural hematoma.[78101118]

Investigations

An MRI is the investigation of choice and demonstrates a well-circumscribed, lobulated lesion, iso- to-hypointense to the spinal cord on T1- and hyperintense on T2-weighted images, with avid homogenous post-contrast enhancement.[6789101422] The peripheral rim of hypointensity, resulting from hemosiderin deposition, is usually seen in the intramedullary CH and not in EECH. EECH also differs from their intracranial counterparts in that they are homogenously hyperintense on T2-weighted images, and enhance avidly with contrast. In this, they may resemble the CH arising from the cavernous sinus more. The absence of popcorn-like peripheral blood products may be explained by the fact that these may be washed away as EECH lie outside the blood-brain barrier.[14] It may be impossible to differentiate between extradural CH and extradural schwannomas or neurofibromas.[56781014] We were certainly unable to differentiate between the two preoperatively. During surgery too, our first thought was that of a vascular metastasis, as the lesion lacked a classical multilobulated purplish mulberry/blueberry appearance and was instead reddish. This was described by other surgeons too.[12141822] Feng et al.[9] had described the visual effect of contrast enhancement within these tumors as that of ‘wafting silk’, with lobules bulging into the interlaminar space on the sagittal images, especially so in the thoracic spine. They also described widening intervertebral foramina and bone erosion. Elegant as it sounds, we have seen this appearance before in schwannomas, meningiomas, and round cell tumors, and still believe that to make a preoperative diagnosis reliably, in a classical case such as ours, it is not possible by using MRI alone. However, the addition of angiography may make a difference. EECH are angiographically occult, but enhance brilliantly with contrast. Osseous CH show up on angiograms as would vascular schwannomas and meningiomas.[23]

Round cell tumors and even tubercular granulation tissue may be differentiated from classical EECH by a hypointense signal on T2-weighted images.[23] Similarly meningiomas too would be hypo- to-isointense to the spinal cord on T2-weighted images in a majority of the cases. Theoretically, extradural, extraosseous CH are homogeneously hyperintense on T2-weighted images, unlike schwannomas, which are likely to be heterogenous and may display a ‘target sign’.[24] Practically, differentiation may not be reliable, especially when reports in the literature describe juxtapositioned intradural schwannomas and EECH.[25] Lesions that are hyperintense/heterogeneous on both T1- and T2-weighted images should raise a greater doubt about the preoperative diagnosis of EECH.[518]

Our case, in hindsight, did deliver one additional pearl of instruction. The remote vertebral hemangioma at T8 shared nearly the exact MRI signal characteristics as the EECH at T2-T4. This was especially so on the T2-weighted images. The EECH [Figure 1] has a signal different from the epidural fat and CSF, but similar to the vertebral hemangioma.

Management

The majority of patients with EECH present with thoracic compressive myelopathy, secondary to lesions that are dorsally located, and pose a diagnostic conundrum on MRI. For these very reasons they are excellent surgical candidates. In expert hands, total excision via a posterior approach is the norm, with excellent results.[81214151617182122] Postoperative radiotherapy has been described, but is perhaps, reserved only for patients with incomplete resection where the risks of redo surgery are deemed unacceptable.[26] More recently, spinal image-guided Stereotactic Radiosurgery (SRS) has been reported for the adjuvant therapy of residual biopsy-proven extraforaminal EECH.[13]

Once a histopathological diagnosis has been established, it may be worthwhile to scan the craniospinal axis, as 40% of the patients with spinal CH may have cranial lesions.[27]