Convexity Dura-Based Cerebral Cavernous Malformation Mimicking Meningioma: A Case Report and Literature Review.

Cavernous angioma, cavernoma, cavernous hemangioma, also called cerebral cavernous malformation (when present in the brain), are benign vascular malformations, usually intraparenchymal; however, a few reported cases are in the extra-axial location-as middle cranial fossa, near the cavernous sinuses, and in the cerebellopontine angle-and are rarely reported as dura-based convexity lesion resembling meningioma. We report a giant dura-based, convexity, a cerebral cavernous malformation. We wish to notify the case as occurring at a rare location and a large-sized cerebral cavernous malformation. A case of young female presented with a long-standing history of headache. Computed tomography scan and magnetic resonance imagings (MRIs) suggested right occipital dura-based large mass lesion of approximately 5 cm in diameter. The lesion was excised and pathology studies confirmed the diagnosis of a cerebral cavernous malformation. A follow-up MRI confirmed total resection of the lesion and the patient had a smooth postoperative recovery. Asian Congress of Neurological Surgeons. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. ( https://creativecommons.org/licenses/by-nc-nd/4.0/ ).

Background and Importance

Cavernous angioma is an angiographically occult vascular malformation, related to the fact that it is not usually visible on conventional cerebral angiography. Cavernomas are not neoplastic lesions, but vascular malformation. Cerebral cavernous malformation is present in approximately 0.5% of the general population, usually intra-axial lesions. But occasional extra-axial locations of cerebral cavernous malformation are reported in the middle cranial fossa or near the cavernous sinus. Cavernous malformation has the classical mulberry appearance with engorged purplish cluster of vessels, caverns, with diameters varying from 2 mm to several centimeters. Histologically, it consists of a dilated thin-walled capillary with simple endothelium and thin adventitia, vessels wall lack of smooth muscles, and leakage of blood through the thin walls, lead to surrounding hemosiderin, it may also contain calcification.

Developmental venous anomalies are associated with cavernous malformation in approximately 10 to 20%. Most of cavernous malformation remain asymptomatic, but they may present with headache, seizures, or focal neurological deficit secondary to bleeding. In many occasions, these lesions are discovered incidentally when performing imaging to unrelated symptoms. The best diagnostic imaging is the Susceptibility Weighted Images, and the gradient-echo magnetic resonance imaging (MRI) sequences.

Case Description

Clinical Presentation

A 24-year-old female presented with frequent episodes of nonspecific headache. There was no history of seizures; she had an unremarkable past medical history. She had no focal neurological deficit.

Computed tomography (CT) scan suggested a dura-based right occipital mass lesion, with calcifications, and evidence of scalloping of the inner table ( Figs. 1 2 3 4 ).

Fig. 1

CT scan without contrast.

Fig. 2

Brain magnetic resonance imaging (MRI) showing right occipital dura-based mass lesion. T2 and fluid-attenuated inversion recovery-weighted images displaying intermediate to high signal. Blooming dark low signal intensity on susceptibility weighted images. There is no obvious dura tail, and from the previous computed tomography scan, there is no hyperostosis, suggested differential diagnosis of atypical meningioma, or hemangiopericytoma.

Fig. 3

The lesion shows evidence of diffusion restriction with heterogeneous enhancement on contrast sequences, while reduced cerebral blood volume and cerebral blood flow in magnetic resonance perfusion study.

Fig. 4

Follow-up magnetic resonance imaging scan showed total excision of the mass lesion.

Surgery

An elective craniotomy and resection of the mass lesion was done.

There was no overlying bone hyperostosis; the dura could be separated from the mass lesion, which appeared highly vascular with surrounding small vessels feeders ( Figs. 5 6 7 8 ).

Fig. 5

Surgical specimen A.

Fig. 6

Surgical specimen B.

Fig. 7

Surgical specimen C.

Fig. 8

Surgical specimen D.

Histopathology confirmed the diagnosis of cavernous hemangioma. It was reported as a pack of thin-walled ectatic dilated blood vessels, lined by flat endothelium, which contained fresh and old blood; the lesion showed area of extensive hyalinization with nodule formation, calcification, fibrosis, and organized hemorrhage.

The adjacent brain tissue showed gliosis with organizing inflammation ( Figs. 9 , 10A , 10B , 11 ). The final diagnosis was cavernous hemangioma.

Fig. 9

Back-to-back thin-walled blood vessels lined by flat endothelium (hematoxylin and eosin ×100).

Fig. 10

Endothelial cells are highlighted by D2–40 (A, red arrows ) and CD31 (B, red arrows ) (immunohistochemistry ×100).

Fig. 11

Endothelial cells are negative by meningothelial marker (immunohistochemistry ×100).

Discussion and Literature Review

Cavernomas are usually intra-axial lesions; the developing MRI technology allows accurate diagnosis of cavernoma; but, it is a diagnostic challenge when unusual, location, as extra-axial, or even rare presentation as dura-based lesion.

Most of cerebral cavernomas are silent and could be discovered incidental when imaging is done for other reasons, like vague headache, or even after car accident; other presentation is secondary to bleeding.

The clinical presentation is widely variable depending on the location of the lesion, and if any bleed, still headache is the most common presenting symptoms; seizures and neurological deficit are usually after bleeding event, which is usual limited.

There are few reported cases of extra-axial cavernoma, but fewer cases of dura-based, and convexity-dura-based are even rare.

We reviewed 61 papers through PubMed search using related keywords (see Table 1 ).

Table 1

Literature review of extra-axial cavernoma

Location	Reference	Number of cases
Cavernous sinus	1 2 3 4 (4 cases) 5 (12 cases) 6 (2 cases) 7 8 9 10 11 (6 cases)	31
Suprasellar and parasellar	12 13 14 15 16 17 18	7
Anterior clinoid	19	1
Superior sagittal sinus	20 21	2
Parietal	22 23 24 25	6
Convexity	26
Temporal convexity	27 28	2
Frontal convexity	29 30 31	3
Occipital convexity	32 33	2
Falx cerebri	4 34 35 36 37	6
Sphenoid wing	383940 (2 cases)	4
Anterior cranial fossa	41	1
Cerebellopontine angle	42 43 44 45 46 47 48 49	8
Lateral medullary	50 51	2
Third nerve	52 53	2
Fifth nerve	54	1
Foramen magnum	55 56	2
Falx cerebelli	57 58	2
Posterior cranial fossa	59 60	2
Tentorial cerebelli	61	1

When reviewing the current data, most of the extra axial located cavernoma are diagnosed around and in the cavernous sinus, 1 2 3 4 5 6 7 8 9 10 11 parasellar, suprasellar, 12 13 14 15 16 17 18 in the cerebellopontine angle, 42 43 44 45 46 47 48 49 and lateral to midbrain and medulla.

There is few reported cavernoma presented as convexity dura-based location, mimicking meningioma; among the convexity-located group we found the parietal convexity is the common; 22 23 24 25 there are only two reported cases of occipital convexity. 32 33

In case of dura-based lesions that lack the other radiological feature of meningioma, like dura tail, and adjacent bone hyperostosis, other differential diagnosis should be considered rather than meningioma, like hemangiopericytoma, metastasis to dura, and even cavernoma.

We present a case of large occipital dura-based lesion mimicking meningioma; however, in reviewing the CT scan bone window, there was bone scalloping (not hyperostosis); in MRI scan, we could not see the typical dura tail. These findings raised possible other differential diagnosis as atypical meningioma, hemangiopericytoma, and metastasis to dura, but cavernoma was not in our differential diagnosis.

Conclusion

We report a case of large dura-based, occipital convexity, cavernous malformation; we report the rare location and the large size of the lesion.

Cerebral cavernous malformation may present as a dura-based lesion, but it is rare radiological feature of cavernous malformation, still could be considered as one of differential diagnosis of dura base lesion, especially when other classical feature of meningioma is missing (dura tail, adjacent bone hyperostosis). Such atypical radiological location and large size of the cerebral cavernous malformation are under-reported. We report this case to be an addition to the literature, and to be available for reviewers.