Keywords
angiolipomas - epidural - laminectomy - spinal cord compression - neoplasms - paraparesis
Introduction
Extradural tumors of the spine usually arise from hematologic malignancies like lymphoma,
multiple myeloma, or from metastasis. Primary extradural tumors are mostly osseous
in origin, like aneurysmal bone cyst, giant cell tumor, osteosarcoma, chordoma, etc.[1] Spinal extradural angiolipomas (SEALs) are extremely rare, benign, extradural lesions.
They constitute approximately 0.04 to 1.2% of all spinal tumors and 2 to 3% of spinal
extradural lesions.[2] Only approximately 120 cases were reported from 1800 to 2020 to the best of our
knowledge. These tumors are more common in females, usually diagnosed in the fifth
decade of life.[3] They are usually located in the posterior surface of the dura. The tumor often molds
itself to the epidural space (noninfiltrating) with occasional “nipple-like projections”
extending into the intervertebral foramina.[4] Most of the time SEALs are noninfiltrating but can rarely infiltrate the adjacent
bony structure of the spine. Also, infiltrating angiolipoma tends to localize in the
anterior epidural compartment. Nonetheless, both have excellent prognosis after surgical
removal.[5]
Case Report
Case 1
A 55-year-old male presented with complaints of back pain along the dorsal and lumbar
regions for the past 10 days. He also experienced lower limb weakness and progressive
difficulty in walking during the last 10 days. He had a history of slip and fall 15
days back. There was no history of bowel or bladder disturbance. On examination, bilateral
lower limbs were hypertonic and hyper-reflexic with a positive Babinski sign. The
muscle power was 3/5 (Medical Research Council [MRC] grade) in both lower limbs. Hypoesthesia
was present below the T4 (thoracic) dermatome level. Magnetic resonance imaging (MRI)
revealed a well-defined T2 hyperintense extradural lesion measuring 6.4 × 1.1 × 1.7 cm
in the D2–D5 (dorsal/thoracic spine) level, situated in the posterior epidural space.
The lesion compressing the spinal cord also showed avid post-contrast enhancement
([Fig. 1]). The lesion was reported to be suggestive of metastatic deposit/sarcoma/plasmacytoma.
We proceeded with laminectomy from D2 to D5 levels, which revealed a reddish-brown,
well-defined, sausage-like mass over the dura mater ([Fig. 2]). It was easily mobilized from the dura and complete surgical excision was done.
Postoperatively, neurological deficit improved and the patient started walking with
assistance on POD (postoperative day) 3 before gaining full motor power and sensations
by 3 months. Histopathology revealed the encapsulated tumor to be made of proliferating
capillary and cavernous blood spaces admixed with mature adipose tissue. There was
no evidence of pleomorphism, mitosis or necrosis, and the tumor was reported as an
angiolipoma ([Fig. 3]).
Fig. 1 (A) Green arrow pointing the well-defined T2-hyperintense extradural mass extending
from the D2 to D5 level in the posterior aspect of the spinal canal. (B) Yellow arrow pointing the mass with avid post-contrast enhancement.
Fig. 2 Intraoperative images showing (A) the tumor after laminectomy and (B) the dura after excision of the tumor.
Fig. 3 Histopathology image showing proliferating capillary and cavernous blood spaces admixed
with mature adipose tissue that were divided by hyalinized fibrous septa.
Case 2
A 47-year-old female presented with complaints of inability to walk, paresthesia of
both lower limbs, and gait disturbance for the past 2 weeks. There was no history
of incontinence. The patient also gave an unreliable history of a trivial fall from
standing height 3 days before. On examination, the patient had spastic paraparesis
(MRC grade 3/5) associated with exaggerated deep tendon reflexes, ankle clonus, and
bilateral Babinski signs. Light touch, position, and vibration sensations were decreased
below the level of the umbilicus. MRI revealed an extradural lesion of size 4 × 1 × 0.7 cm
extending from D8–D10 in the posterior aspect of the spinal canal ([Fig. 4]). The lesion was isointense on T1 and hyperintense on T2-weighted sequences and
was reported to have features suggestive of subacute epidural hematoma. We proceeded
with laminectomy in view of neurological deficit. Intraoperatively, the lesion was
recognized as a brown, elastic, soft extradural tumor of the above-mentioned dimensions.
The lesion was nonadherent to the dura and was excised in toto. Postoperatively, neurological
deficits improved, and the patient started walking with assistance and was discharged
on POD 5. The patient came with full motor power and sensations during the follow-up
visit after 2 months. Histopathological examination revealed the tumor to be an angiolipoma
with vascular elements and adipose tissue.
Fig. 4 Arrow pointing the well-defined T2-hyperintense, extradural lesion in the posterior
aspect of spinal canal extending from the D8 to D10 level.
Discussion
Spinal angiolipomas are most commonly found at the thoracic level. The patients mostly
present with complaints of back pain, progressive paraparesis, hyper-reflexia, and
sensory changes in the lower extremities.[6]
[7] The time between onset and diagnosis of symptoms in most cases is 1 year or less.[8] Subacute paraparesis can develop in extramedullary lesions, where symptoms progress
due to the slow growth of the tumor.[4] Extradural angiolipomas receive their vascular supply from the recurrent radicular
arteries. Interestingly, these lesions occur predominantly in the mid-thoracic region,
which is a relatively avascular zone of the spinal cord.[9]
Acute deterioration of neurological status can occur as a result of rapid increase
in tumor volume due to vascular causes such as thrombosis, intratumoral hemorrhage,
or “steal phenomenon,” resulting in acute compression of the spinal cord.[7]
[10] Von Hanwehr et al have speculated that the enlargement of abnormal vessels can lead
to tumor expansion. Further, degeneration of tumor vessel walls might lead to changes
in tumor blood supply and hemorrhage with resultant epidural compression. Events like
blood volume and extracellular fluid volume changes that occur in pregnancy and alterations
in fat mobilization patterns (due to hormonal changes) also may cause an increase
in tumor mass. All these can accelerate the symptoms of SEALs.[7]
[9]
Si et al have classified spinal angiolipomas into two types: type I—intraspinal: type
IA: without lipomatosis, type IB: with lipomatosis; type II—dumbbell-shaped (both
intra and extra-dural). Both our cases were type IA, which has a good outcome compared
with type IB. It is because type IB-associated lipomatosis remnants may cause spinal
cord compression even after excision of angiolipoma.[2] Computed tomography (CT) shows a hypo- to hyperdense mass depending on the amount
of vascular component or the presence of calcification. Angiolipoma can be suspected
in the presence of erosive bone changes with hypo/hyperdense mass in the epidural
space. However, CT-scan findings are nonspecific.[9]
[11] MRI is the modality of choice to detect SEALs. The fat content of angiolipoma appears
hyperintense in both T1- and T2-weighted images, while the vascular component is isointense
in T1- and hyperintense in T2-weighted sequences, respectively. Type IA tumor appears
as a homogeneous lesion that is isointense or hypointense (occasionally) on T1 and
hyperintense on T2 images.[2] The degree of central hypointensity on T1-weighted images is predictive of the tumor
vascularity.[6] On fat suppression sequences, the abnormal intensities within the fatty tumor may
be enhanced. There is an avid post-contrast enhancement.[2] The vascular component of the type IB tumor has a similar appearance as described
above, while the lipomatosis component appears hyperintense in both T1- and T2-weighted
sequences. Lipomatosis appears hypointense in the fat suppression sequence and does
not show contrast enhancement.[2]
These tumors are highly vascular, composed of proliferating capillary and cavernous
blood spaces admixed with mature adipose tissue. Both components do not display cytological
atypia, mitosis, or nuclear pleomorphism.[12] Various theories have been proposed on the histopathogenesis of angiolipomas. They
are speculated to arise from abnormal primitive pluripotent mesenchymal cells. Angiolipomas
are suggested by some authors to be true hamartomas.[8]
It is imperative to distinguish angiolipoma from its close differentials histopathologically.
When the fat component predominates, abnormal pericytic proliferation and complex
branching patterns of the capillaries within the tumor distinguish angiolipoma from
lipoma.[13] Similarly, the presence of identifiable adipocytes rules out a vertebral body hemangioma
extending into the extradural space.[14] Liposarcoma is a possible differential diagnosis to be considered, as pleomorphic
and myxoid liposarcomas have been reported to occur in the intradural and extradural
space. The absence of pleomorphic lipoblasts with areas of high-grade sarcoma may
help in ruling out the pleomorphic variant. Also, well-differentiated liposarcoma
without pleomorphism can be identified against angiolipoma by the presence of lipoblasts.[12]
[15] The presence of a myxoid background, a distinctive “chicken wire” pattern of blood
vessels, and some signet ring-like (mononuclear) lipoblasts are mandatory for the
myxoid variant to be considered. In all, the bland histology of angiolipoma is not
easily confused with the above differentials.[16]
Total surgical resection is the mainstay of treatment, as most extradural angiolipomas
are noninfiltrating and are completely removable by laminectomy. The majority of patients
have excellent outcomes after surgery, with complete recovery from paraplegia.[17] In the case of infiltrative angiolipoma, the goal is to achieve a complete excision,
which may not be feasible in some instances. In such scenarios, treatment must focus
on removing the epidural part and cord decompression. Even adjuvant radiotherapy is
not indicated as the tumors grow slowly and usually do not recur.[5]
[18]
Conclusion
SEALs pose a diagnostic challenge to both the surgeons and radiologists, as they are
seldom encountered in day-to-day practice and also mimic other spinal lesions. MRI
is the diagnostic modality of choice. T2-weighted, fat-suppressed, and post-contrast
images can reliably point toward the diagnosis. Current experience and literature
support curative surgical resection to avoid progression of symptoms and relieve the
neurological deficit. In the case of infiltrating angiolipomas, total resection to
provide adequate decompression can be challenging. However, prognosis is excellent
in most cases due to the slow-growing nature of the tumor and absence of malignant
transformation.
