Cavernous Venous Malformations
Key Points
Cavernous venous malformations, previously called cavernous hemangiomas, are rarely observed in the eyelids
They are low flow developmental venous malformations and not true tumors, and the exact pathogenesis remains elusive to this day
Growth results from relative stasis of vascular elements and repeated bouts of thrombus formation, followed by recanalization with endothelial cell proliferation to line the newly formed spaces
In the eyelid, CVM can be located subcutaneously, are not encapsulated, and tend to adhere to the dermis
Alternatively, they may arise from the palpebral conjunctiva, usually in the caruncle
Eyelid CVMs were thought in the past to be associated with the blue rubber bleb nevus syndrome or sinusoidal hemangioma
Surgical excision is the preferred method of treatment
Surgical excision is both curative and safe with very few recurrences
Cavernous venous malformations (CVMs), previously called cavernous hemangiomas, are the most common primary lesions in the orbit in adults, but they are rarely observed in the eyelids or on the ocular surface.1,2,3,4,5,6,7,8,9
Because their endothelium lacks a proliferative potential, CVMs are currently considered low flow developmental venous malformations and are not true tumors.3,4 Although the term cavernous hemangioma is deeply entrenched in the ophthalmic literature and remains heavily used up to the present day,8 the suffix oma is incorrect and should not be used in clinical practice.1,3,4,5,6 However, taking a radical approach in the opposite direction and referring to CVMs simply as venous malformations,9 instead of the traditional term cavernous hemangioma, may be misleading as well. The term “venous malformation” is a generic collective term that is currently recommended by the International Society for the Study of Vascular Anomalies (ISSVA) to describe venous anomalies in general.7 Adopting this simplistic approach does not differentiate between distensible venous malformations, referred to in the ISSVA classification as common venous malformations, and CVMs of the orbit.7 This approach is based on a misinterpretation of the ISSVA classification, which does not include the term “cavernous” in its orbital context.7,10 Nevertheless, the term “cavernous” is still repeatedly used by ISSVA in relation to cerebral CVM. Therefore, we believe that what should be discarded is the term “hemangioma” only, whereas the discerning nomenclature “cavernous” should be retained for now because discarding it may add to the confusion rather than reduce it.10 To solve this dilemma, it was recently proposed to subclassify orbital venous malformations (OVMs) into three3 or five10 distinct types. Cavernous hemangiomas are termed orbital venous malformation type 1 (OVM1), while orbital varices are referred to as OVM2. OVM3 is a more extensive version of OVM2 with widespread communication between the orbital and intracranial venous systems,3 OVM4 is glomuvenous malformation (glomus tumor), and OVM5 is intraosseous VM.10 As a trade-off, until a formal classification that takes into consideration the unique spectrum of all periocular vascular anomalies is adopted, the term CVM will be used in this chapter while the term distensible venous malformations will be used in the chapter about eyelid varices (see Chapter 60).
Etiology and Pathogenesis
Despite the numerous articles that have been published about CVMs in the literature, research has not been very active regarding the origins and pathogenesis of these curious lesions, and surprisingly very little is known about their etiology.10,11 Unfortunately, the question that was raised in the 1980s “What is cavernous hemangioma of the orbit?”12—still lingers unanswered in early 2022.10 The growing consensus in the past 2 decades, which is frequently quoted and inadequately explained, maintains that (1) CVMs are slow flow malformations and not tumors; (2) they are exclusively venous malformations (akin to a PUIG type I pure venous malformation); therefore, they should fall under the ISSVA category of venous malformations; and (3) their growth is attributed to ectasia and hypertrophy rather than endothelial proliferation, which is attributable to local hormonal changes or local hemodynamic disturbances resulting from the sluggish blood flow and ischemia or hypoxia.1,10,11,12,13,14,15,16,17,18,19,20 Although a great deal of evidence
exists in support of the scientific idea that CVMs are relatively stable venous malformations, and not true tumors, there are considerable clinical differences between vascular malformations and orbital CVMs, which might challenge the current consensus that CVM is a true malformation. There is no overlap in the age of presentation between CVM and vascular malformations as the onset of CVM is typically much later (around the 5th decade). Their growth pattern is also different as malformations generally grow commensurately with the growth of the child and, by definition, should not regress or involute, while orbital CVM may present suddenly, may have a variable growth pattern, and may even reduce in size postmenopause.10 The confusion is buttressed even further by their vastly dissimilar prognosis. While CVM rarely recurs even after incomplete excision, recurrences or rather recrudescences are the rule rather than the exception in malformations.10
exists in support of the scientific idea that CVMs are relatively stable venous malformations, and not true tumors, there are considerable clinical differences between vascular malformations and orbital CVMs, which might challenge the current consensus that CVM is a true malformation. There is no overlap in the age of presentation between CVM and vascular malformations as the onset of CVM is typically much later (around the 5th decade). Their growth pattern is also different as malformations generally grow commensurately with the growth of the child and, by definition, should not regress or involute, while orbital CVM may present suddenly, may have a variable growth pattern, and may even reduce in size postmenopause.10 The confusion is buttressed even further by their vastly dissimilar prognosis. While CVM rarely recurs even after incomplete excision, recurrences or rather recrudescences are the rule rather than the exception in malformations.10
Moreover, numerous histopathological studies have demonstrated that orbital CVMs are not that static and may potentially have a low proliferative capacity, as they express several immunohistochemical vascular enhancers like vascular endothelial growth factor A (VEGFA) and its receptor VEGFr2 in 27% to 100% of the lesions.19,20,21 However, the current consensus or counterargument is that the overexpression of those proangiogenic regulators or vascular enhancers by orbital CVM is simply a secondary effect of ischemia and recurrent bouts of thrombosis, which might stimulate mitotic activity resulting in the vascular remodeling observed in CVM. According to that scenario, VEGF is not a “true engine of growth”17; nevertheless, what these results merely suggest is that VEGF, which is a major effector and promoter of endothelial cell proliferation and differentiation, is somehow involved in the growth of CVM, and perhaps more research is needed in this area to clarify its exact role.20 Furthermore, the purely venous nature of CVM is not firmly established either, and over the years, the thought of an arterial contribution to CVM has repeatedly been entertained in the oculoplastic literature.14,18,22
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