Cavernous malformations of the orbit a distinct e

Authors: Nedal Hejazi Werner Hassler Felix Offner Antonius Schuster

Publish Date: 2006/11/07

Volume: 30, Issue: 1, Pages: 50-55

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Abstract

We collected data to provide evidence that orbital cavernous malformations CMs are histopathologically neuroradiologically and clinically different from cerebral CMs and may represent a distinct entityIn this study the main clinical histopathological and radiological characteristics of 19 patients 11 females and eight males mean age 491 years with orbital CMs out of a series of 376 orbital tumors are analyzed and compared with 107 cases with cerebral CMs treated in the same period Decrease of visual acuity and painless progressive proptosis were the main clinical signs observed in 17 patients 89 Complete microsurgical excision of lesions via individualized approaches was obtained in all cases Followup examinations were obtained after a mean of 31 years 11 months to 7 years and yielded complete recovery in 14 patients while five remained clinically unchanged Based on clinicopathological and neuroradiological studies of these 19 patients with orbital and 107 patients with cerebral CMs treated in the same period we found evidence that orbital CMs have specific features to distinguish them from cerebral CMs Orbital CMs in contrast to the cerebral CMs showed nondegenerated welldeveloped vessel walls and were covered by a hard and compact capsule Clinical symptoms are characterized by the growth of orbital CMs due to intraluminal thrombosis and subsequent recanalization of cavernous vessels there were no signs of hemorrhage We found evidence to suggest that orbital CMs represent a distinct clinicopathologic and neuroradiologic entityCavernous hemangiomas are generally considered vascular hamartomas nevertheless some authors find several lines of evidence that they could be neoplastic in nature These lesions are composed of endotheliumlined caverns filled with blood at different stages of thrombosis and organization embedded in a collagenous matrix It is assumed that cavernous hemangiomas grow by hemorrhage luminal thrombosis hemorrhage resolution and organization but less frequently they increase in size without evidence of hemorrhages Besides de novo cavernoma formation commonly occurring in children after cranial irradiation has been described 1 Finally the identification of KRIT1 mutations in patients with cavernomas suggests a molecular basis for the neoplastic expansion of endothelial cells 2We treated 34 orbital cavernous hemangiomas 519 of 654 orbital tumors the same percentage as the authors The approach to this wellcircumscribed rounded lesion is determined by its location Twentyone of them were intraconal in the orbital apex and were operated on by means of a supraorbital craniotomy Eight were located in the lateral part of the intraconal space and could be resected by a lateral approach and five inferiorly located were operated on by means of a transmalar approach that allows excellent exposure of the inferolateral aspect of the orbitTypically there is a clear plane of cleavage that allows an easy dissection of the lesion from the surrounding structures and a clean “en bloc” resection We did not found indication for a contralateral pterional approach for this pathology We agree with the authors that orbital cavernomas present some differences with its intracranial counteroparts They do not present with hemorrhages as orbital lymphangiomas frequently do they are well encapsulated may be a fibroblastic reaction of the orbital fatty tissue as the authors pointed out they are not associated with venous angiomas and enhance markedly with contrast media both in CT and MR imaging scans Perhaps the molecular biology study of orbital and cerebral cavernous malformations ie KRIT1 mutations PCNA analysis etc could shed light on their true nature and explain their differencesIn this retrospective review the authors discuss their experience with orbital and cerebral cavernous malformations In their study 19 patients presented to their institutions between 1988 and 2005 with orbital cavernous malformations out of 376 total orbital tumors During the same time period 107 cases of cerebral cavernous malformations were treated Based on differences in the clinical histopathological and radiographic characteristics of the orbital lesions the authors conclude that orbital cavernous malformations are a distinct entity from cerebral cavernous malformations The authors of this paper have done a commendable job in collecting and analyzing data from their patients with orbital and cerebral cavernous malformations The clinical histopathological and radiographic characteristics of these lesions were thoroughly described and their differences analyzed The authors found that in contrast to cerebral cavernous malformations orbital cavernous malformations were not observed to have hemorrhaged In addition orbital cavernous malformations were homogenously enhancing lesions on T1weighted MR imaging after contrast administration compared with cerebral lesions that were nonenhancing Pathologically orbital cavernous malformations were encapsulated and composed of wellformed endothelium lined microvasculature while cerebral cavernous malformations were unencapsulated and possessed degenerating collagenous tissue in their walls In addition orbital cavernous malformations were not associated with other vascular anomalies such as venous angiomas Based on the differences between orbital and cerebral cavernous malformations the authors’ conclusion that these are distinct entities is justified Understanding this distinction is important in that the lesions’ natural histories are different as are the indications for treatment The distinction between orbital and cerebral cavernous malformations may have important implications for their future treatment Significant progress has been made toward understanding the genetic and molecular basis of cerebral cavernous malformation development As a different clinical entity different molecular mechanisms may underlie the development of orbital cavernous malformations however Novel therapies created for cerebral cavernous malformations and based upon their unique molecular pathogenesis may not be efficacious in treating orbital cavernous malformations that develop through different mechanisms And although this will be frustrating this situation does present unique opportunities as well Investigating the distinct molecular mechanisms of orbital cavernous malformation development may identify novel genes involved in vascular development It may be through further study of orbital cavernous malformation development that surprising insights into angiogenesis and vascular development may be discovered

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