edema surrounding the AVM produced this reversible phenomenon.

Children with AVMs may be more prone than adults to present with a hemorrhage and to experience recurrence of the lesion after treatment. In one study,663 61% of children with spontaneous intra-cerebral hemorrhage were found to have AVMs. Many surgeons favor resection for most AVMs and use embolization as a preoperative strategy for Grades II to V lesions treated surgically. Prehemorrhagic Grade IV and V lesions may best be treated conservatively and observed carefully for the development of symptoms.114 Although AVMs have been called the “most frequent abnormality of the intracranial circulation in childhood,”411 their natural history is poorly understood. They are generally considered congenital although some authors have recently challenged this notion.354,606

Children constitute 3–20% of patients with AVMs, and these lesions cause 30–50% of intracranial hemorrhages in children.169 Humphreys et al reported a fourfold higher prevalence of AVMs than aneurysms in children with subarachnoid hemorrhage compared with that in adults.411,829 The perioperative mortality rate was 3.7%. The recurrence rate was 5.6% over 3.3 years, consistent with rates in other pediatric series. The advent of the operating microscope and recent advances in endovascular and radiosurgical techniques (e.g., stereotactic guidance, intraoperative angiography) and have improved the success rate of treatment and offer more options for treatment of AVMs.

Cavernous Angiomas

Cavernous angiomas are congenital blood vessel hamartomas composed of irregular venous sinusoidal channels separated by fibrous septae.564 They are often referred to as cryptic or occult vascular malformations because they are difficult to identify with angiography; however, they are now detected much more readily with MR imaging. Patients with cavernous angiomas may remain asymptomatic or present with seizures, intracerebral hemorrhage, or symptoms of an intracerebral mass lesion. Although rare in children, cavernous angiomas of the optic nerve and chiasm have been reported to produce visual loss.564 Chiasmal cavernous angiomas may present with insidious vision loss or acute visual loss associated with a throbbing headache (termed chiasmal apoplexy).563,564 Cavernous angiomas are now initially diagnosed by MR imaging and confirmed by biopsy. Some cavernous hemangiomas of the CNS occur in conjunction with cavernous hemangiomas of the retina and skin.331,332 When the diagnosis is established, other family members should also be examined because the conditions are often familial.564

Intracranial Aneurysms

Intracranial aneurysms are uncommon in children. When they occur, aneurysms in the pediatric population are more commonly of the giant type (greater than 2.5 cm in size), and they more commonly arise peripheral to the circle of Willis than in the adult population.685 In a joint study of pediatric aneurysms, Roche et al747 found a marked sex predilection, with 70% of aneurysms arising in males. Several studies have noted an unequal topographic incidence in the circle of Willis, with 50% arising from the internal carotid bifurcation, 25% from the anterior cerebral artery, and 12.5% from the posterior cerebral artery in one study.422 Subarachnoid hemorrhage is the most common clinical presentation and may produce severe headache, vomiting, and obtundation, sometimes progressing to coma. Surgical treatment, consisting of removal of the aneurysmal sac, produces more favorable results than in adults, presumably due to cerebral plasticity and tolerance to vasospasm in children.747

Neuro-ophthalmologic signs of aneurysm in children usually result from subarachnoid hemorrhage (i.e., papilledema and sixth nerve palsy) rather than from compression. In some cases, hyperacute elevation in intracranial pressure associated with aneurysmal rupture results in Terson syndrome (papilledema with retinal and vitreous hemorrhage). Children with giant intracranial aneurysms (which constitute 20–40% of pediatric cases) may present with focal neurological symptoms and signs as a result of compression of the surrounding brain by the aneurysm.58 Posterior communicating artery aneurysms are particularly rare in children,37 but because of their immediate proximity to the third nerve, their enlargement may allow them to be diagnosed before rupture and subarachnoid hemorrhage occur, unlike other intracranial aneurysms that must reach giant size before producing signs of compression without subarachnoid hemorrhage.310 There have been only a handful of documented cases of acute third nerve palsy in children with posterior communicating artery aneurysms, all within the second decade of life. The question of whether to obtain cerebral angiography in children with acute third nerve palsy with pupillary involvement and headache but no signs of subarachnoid hemorrhage remains controversial.310

Most pediatric aneurysms are surgically clipped, but endovascular obliteration of the aneurysm can be performed in cases in which surgery is unsuccessful or when the aneurysm has no definable neck.376 Ocular hemorrhages (8% Terson syndrome and 9% other ocular hemorrhages) have been estimated to occur in 17% of patients with ruptured intracranial aneurysms.320