History
Neurologic symptoms of Wyburn-Mason syndrome (WMS) are extremely variable and depend on the size, location, and configuration of the central nervous system (CNS) AVM. Mental status or neuropsychiatric changes, headaches, seizures, stroke, hemiparesis, visual-field abnormalities (homonymous hemianopia), subarachnoid hemorrhage, intracerebral hemorrhages, increased intracranial pressure (papilledema), cranial neuropathies, and/or hydrocephalus may occur. Extracranial AVMs may manifest as potentially life-threatening oral hemorrhages or epistaxis. [4, 1]
Similarly, neuro-ophthalmic signs and symptoms of Wyburn-Mason syndrome result from retinal or intracranial AVMs and are related to AVM size, extent, and location. Small AVMs may produce no visual symptoms, whereas larger AVMs may lead to profound vision loss. These signs and symptoms include retinal and vitreous hemorrhages, retinal detachment, venous occlusive disease (and secondary risk of rubeosis iridis and secondary glaucoma), optic disc edema, or optic atrophy. Intracranial AVMs may produce secondary neuro-ophthalmic manifestations, including papilledema, pupillary changes, homonymous hemianopia, ptosis, proptosis, gaze paresis, cranial nerve palsies, strabismus, nystagmus, and, in childhood, superimposed amblyopia. [1, 6, 7, 8, 9, 10, 11]
Physical
Associated intracranial AVMs are more commonly found in patients with large, racemose retinal vascular anastomoses. CNS vascular lesions are typically ipsilateral to the involved eye, and they frequently involve the midbrain. [1, 6, 12, 13] In some cases, retinal lesions may result from an extension of an intracranial vessel malformation, extending anteriorly along the visual pathway, through the optic foramen, and along the optic nerve to the retina.
The ophthalmoscopic appearance of the retinal AVM may vary from small, abnormal vessel communications to extensive racemose involvement of the entire fundus. Retinal AVMs typically appear as dilated and tortuous retinal vessels extending from the optic disc to the retinal periphery, resembling a “bag of worms.” Also referred to as cirsoid aneurysm, arteriovenous aneurysm, arteriovenous communication of the retina, racemose hemangioma, and arteriovenous varix, these abnormal retinal vessels typically remain stable and do not demonstrate leakage on fluorescein angiography (FA).
Archer et al classified retinal AVMs into 3 groups, as follows [14] :
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Group I is characterized by small arteriole-venule anastomoses, which may be subtle and difficult to clinically detect. These vessels are usually isolated to a sector or quadrant of the retina.
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Group II represents direct artery-to-vein communication without intervening capillary or arteriolar elements causing hyperdynamic flow through low-resistance veins. This group may represent an exaggerated form of the abnormalities included in group I and is likewise geographically segmented within the fundus. Complications can range from edema to hemorrhage.
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Group III includes malformations characterized by markedly convoluted, dilated, and tortuous retinal vessels extending throughout the entire fundus, making it virtually impossible to differentiate between arterial and venous components. These eyes usually are severely vision impaired, typically leading to earlier diagnosis in childhood. Patients in this group are at higher risk for systemic vascular involvement.
Theron and coworkers reviewed 80 cases of retinal vascular anastomoses and found that 30% of these patients also had CNS AVMs, a rate that is much lower than the 81% association reported by Wyburn-Mason. [15] Bech and Jensen believe that the original statistics from Wyburn-Mason are too high, noting that many of Wyburn-Mason's patients had no angiographic or pathologic evidence of intracranial vascular malformations. [16] The preponderance of patients with more advanced retinal lesions in the Wyburn-Mason study may have made associated CNS lesions more likely.
Intracranial and retinal AVMs occasionally are accompanied by vascular malformations in the facial skin, oronasopharnyx, orbit, lung, and bone. Facial lesions may involve the eyelids, cheeks, forehead, and other regions. Orbital involvement can present with proptosis, which may be pulsatile and have an accompanying bruit.
Causes
The etiology of Wyburn-Mason syndrome is unknown.
Complications
Retinal AVMs rarely may be complicated by vascular decompensation and ischemia-related changes.
Vision loss may occur secondary to photoreceptor damage, loss of the nerve fiber layer, or macular ischemia. [17, 18] In addition, orbital or retro-orbital AVMs may induce optic neuropathy and progressive visual disturbances by compressing the optic nerve. [19]
Retinal ischemia eventually can lead to neovascular glaucoma.
Intracranial AVMs may be complicated by headaches, visual-field abnormalities, and seizures. Patients also may experience irritability, cerebellar dysfunction, developmental delay, and/or Parinaud syndrome. [20] Lesions may rupture, resulting in significant morbidity.
AVMs within the mandible or the maxilla may result in excessive bleeding following dental procedures.
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The dilated and abnormal retinal vasculature characteristic of a retinal arteriovenous malformation.
