Dural Infantile Hemangioma Masquerading as a Skull Vault Lesion

Discussion

IHs (previously termed “capillary hemangiomas”) are the most common vascular tumors of infancy. They are benign neoplasms of endothelial cells that rapidly proliferate initially, usually in the first 5 months of life, followed by a plateau phase and slow involution.¹ On histologic examination, these lesions comprise lobules of tightly packed endothelial cells forming capillary-like structures, separated by septa of fibrous connective tissue.^1,2 Identification of the Glut-1 protein on immunohistochemical staining is used to distinguish these lesions from other vascular lesions.¹ More commonly, they involve the skin and soft tissues. Involvement of the neural axis is rare.

There have been 28 cases of intracranial IH published in the literature.^{3⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓–16} Classically, these cases involve the extra-axial basal cisterns, subarachnoid and ventricular spaces, and cavernous sinus.^{7⇓⇓–10,12⇓–14} Two articles reported dural attachment,^10,16 and only 4 cases were intra-axial.^3,4 Most intracranial IHs (71%)^4,7,9,12,14 were associated with extracranial soft-tissue extension or cutaneous hemangiomas.

While spinal dural capillary hemangiomas have been described, this is the first case of cranial dural IH. Cranial IH typically presents in childhood (86%),^{3⇓⇓⇓⇓⇓–9,12,14⇓–16} and in a few cases, in adolescence,^3,10,11,13 while spinal IH usually presents in an older population, (range, 40–62 years).¹⁷

The imaging characteristics of IH within the neural axis are consistent with those found elsewhere, with iso- to low-T1 signal intensity, high T2 signal intensity, and avid contrast enhancement typical on MR imaging.^14,17 Intralesional flow voids are a common feature,^10,14 and foci of high T1 signal intensity are also described.^4,10,17 This may represent thrombosis in some of the small vascular spaces or hemorrhage.

Our initial interpretation of the imaging findings was that this was primarily a bony lesion, an intradiploic IH, with hyperostosis and secondary dural reaction. However, the features were atypical and of concern. There was hyperostosis but no abnormal diploic space enhancement or large abnormal diploic space vessels. The dural reaction was too extensive and florid to be a secondary dural reaction to an intradiploic IH or an essentially benign-appearing bone lesion. Meningioma was considered a possibility, given the florid hyperostosis and dural thickening; however, the appearance was also atypical for this condition. The extensive dural thickening on imaging, therefore, raised concern of a primary dural lesion of sinister etiology.

Hydrocephalus was been described in 10% of intracranial IHs. It is uncertain whether this represents an association with or a consequence of the hemangioma. It could be postulated that thrombosis of small venous structures associated with the hemangioma or the direct mass effect of the lesion alters local CSF flow dynamics, resulting in hydrocephalus. The mild ventricular dilation in our case may reflect such a prior CSF flow alteration because we postulated that this lesion was already involuting at diagnosis.

Given that IHs are self-limited, management is dependent on size, location, and any associated complications, which include visual and neurologic deficits for the intracranial lesions. Contemporary management of IH is with propranolol; however, systemic steroid and interferon therapy has been described.^12,13 In the absence of complicating features, observation in expectation of involution is favored.