Unruptured Vascular Malformation and Subarachnoid Hemorrhage
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P1: KWW/KKL P2: KWW/HCN QC: KWW/FLX T1: KWW GRBT050-109 Olesen- 2057G GRBT050-Olesen-v6.cls August 17, 2005 1:42 ••Chapter 109 ◗ Unruptured Vascular Malformation and Subarachnoid Hemorrhage John R. Østergaard and Nabih M. Ramadan International Headache Society (IHS) code and diag- Patients with AVMs usually present with either an intra- noses: parenchymal hemorrhage (50 to 60%) or seizures (30%) 6.2.2. Headache attributed to subarachnoid hemor- (5,21,71). Patients with perimesencephalic or pretruncal rhage SAH, in whom a saccular aneurysm or AVM cannot be 6.3. Headache attributed to unruptured vascular demonstrated, may develop an explosive headache similar malformation to that described by patients with an aneurysm, but loss of 6.3.1. Headache attributed to saccular aneurysm consciousness is exceptional and the course of the illness 6.3.2. Headache attributed to arteriovenous malfor- is generally benign (62,70). mation (AVM) Unruptured saccular aneurysms often remain asymp- 6.3.3. Headache attributed to dural arteriovenous tomatic for many years but may suddenly produce warning fistula symptoms, including headache, because of either impend- 6.3.4. Headache attributed to cavernous angioma ing rupture (25,47) or progressive enlargement, leading to World Health Organization (WHO) codes and diag- compression of neighboring structures (47). Unruptured noses: G44.810 AVMs may mimic migraine (8,31). Epilepsy is the most 644.810 Headache attributed to subarachnoid common clinical presentation of cavernous malformations hemorrhage (54), followed by signs and symptoms of cerebral hem- 644.811 Headache attributed to saccular aneurysm orrhage. Venous malformations are incidental findings in 644.811 Headache attributed to arteriovenous patients presenting with seizures or headache. In the ma- malformation jority, a causal relationship between the angioma and the 644.811 Headache attributed to dural arteriovenous presenting symptoms is not established (49). fistula 644.811 Headache attributed to cavernous angioma Short description: Subarachnoid hemorrhage (SAH) oc- EPIDEMIOLOGY curs when blood leaks between the layers of the pia- arachnoid membrane. Arteries and veins passing through The true prevalence of saccular aneurysms and other in- this potential space are both possible sources of bleed- tracranial vascular malformations is not precisely known. ing. The majority of SAHs arise from ruptured saccular Venous malformations and capillary telangiectasias have a aneurysms or AVMs (38). Miscellaneous causes include low risk of bleeding or causing symptoms by other mech- cavernous and venous malformations and capillary telang- anisms and are often found incidentally at autopsy (71). iectasias. The headache of SAH typically is abrupt in onset, They occur in approximately 2.6% of subjects (71). developing within seconds, and is often described as the The prevalence of cavernous malformations is 0.5% in worst ever experienced. The headache is usually followed autopsy series and 0.4 to 0.9% in serial magnetic resonance by pain radiating into the occipital or cervical region and (MR) studies (55). They affect both sexes with equal fre- is often accompanied by blunting of consciousness, vom- quency. Most cavernous malformations appear as solitary iting, phono- and photophobia, and neck stiffness. The lesions; however, they have been reported in associa- headache remains severe for hours and then clears over tion with other vascular lesions such as capillary telang- several days to a few weeks. iectasias, AVMs, and venous malformations (55). The 893 P1: KWW/KKL P2: KWW/HCN QC: KWW/FLX T1: KWW GRBT050-109 Olesen- 2057G GRBT050-Olesen-v6.cls August 17, 2005 1:42 894 The Secondary Headaches prevalence of cavernous malformations range between encephalic hemorrhage about 10%; and AVMs, cavernous, 0.02% in autopsy series and 0.9% in MR studies (40). venous malformations, or capillary telangiectasias the rest One retrospective MR angiography study indicated that (62). Patients with angiographically negative SAH (e.g., unsuspected aneurysms are seen in 2.8% of studies (24). perimesencephalic or pretruncal hemorrhage) have an Conversely, their frequency in prospective studies is 3 to excellent prognosis and are unlikely to rebleed (62,70). 6% (53). Postmortem studies of consecutive autopsies indi- Rupture of a dilated vein or venous malformation in the cate that approximately 5% of the population may harbor prepontine or interpeduncular cistern is believed to be re- one or more saccular aneurysm (9,60). In these studies, sponsible for the majority of these cases (53). more than half of the demonstrated aneurysms were un- Up to 50% of patients with saccular aneurysms who are ruptured and unrecognized prior to death. Long-term admitted to neurosurgical departments experience warn- follow-up studies of patients harboring incidentally dis- ing symptoms in the form of minor bleeding episodes, covered cerebral aneurysms suggest that the vast majority days or even several months before a major hemorrhage never rupture or cause any symptoms (68). (25,47,65). Headache is the most common symptom of this The annual risk of rupture of incidental aneurysms less warning leak (47), occurring in 9 of 10 patients. Minor than 7 mm in diameter is low (0.1%), but the risk is higher leaks occur with AVM as well, as evidenced by pathologic (1.5% with aneurysms between 7 and 12 mm). The annual documentation of hemosiderin adjacent to the malforma- risks for additionally discovered aneurysms are 0.4% and tion (71). At surgery, at least 10% of AVMs show evidence 0.8%, respectively (41). of minor bleeding episodes. Small AVMs are more likely to Twenty to 30% of patients with cerebral aneurysms cause minor bleeding than large ones (71). have multiple lesions (aneurysms), usually two or three (47,53). Arterial hypertension and the presence of multi- ple aneurysms highly positively correlate and, considering GENETICS both experimental and epidemiologic studies, arterial hy- pertension is considered a risk factor for aneurysm forma- There is no significant genetic predisposition to the devel- tion (47). The significance of hypertension for aneurysmal opment of AVMs (71). In contrast, a familial form of cav- rupture, however, is less conclusive (47). ernous malformations, which is characterized by multiple Overall, aneurysmal SAH is more common in women lesions and an autosomal-dominant inheritance pattern, is than in men (39,65). However, in considering the gender caused by mutations in the CCM1–CCM3 genes on chro- difference by decade, a 4:1 male:female ratio is encoun- mosomes 7 and 3, respectively (11,14). tered in the first decade of life, which becomes 1:1 by Evidence supporting the role of genetic factors in the fifth decade of life (67). The increased incidence of the pathogenesis of intracranial aneurysms stems from aneurysmal SAH in women is most probably related to the association of intracranial aneurysms with inherited their greater susceptibility to aneurysm formation, rather connective-tissue disorders (e.g., autosomal polycystic kid- than an increased risk of aneurysmal rupture (47). In ney disease, Ehlers-Danlos syndrome type IV [vascular contrast, there is a modest male preponderance among EDS]) and their familial occurrence (56). In contrast to patients with AVMs (71). sporadic aneurysms, familial ones (a) occur less often An AVM and a saccular aneurysm coexist in approxi- on the anterior communicating artery; (b) rupture at a mately 10% of patients. Because the associated aneurysms younger age; and (c) are smaller in size at rupture (34). In have a predilection to the AVM feeding arteries, it is be- a segregation analysis of published pedigrees, several pos- lieved that increased blood flow is a major factor in the sible patterns of inheritance of saccular aneurysms were formation of the saccular aneurysm (76). When bleeding identified, with autosomal transmission being the most occurs, it is more often from the aneurysm than from the likely (57). This suggests that genetic heterogeneity is an AVM (62). important feature of intracranial saccular aneurysms (56). Estimates of the annual incidence of SAH depend on the population surveyed, the methods used for analysis, and the accuracy and extent of the investigations. Reports can ANATOMY AND PATHOLOGY be divided into epidemiologic surveys and referral centers or large-scale cooperative studies. Epidemiologic studies After a hemorrhage, the subarachnoid space contains a include not only hospitalized patients, but also those 15 to variable mixture of cerebrospinal fluid (CSF) and clotted 20% of individuals with SAH who died before receiving and liquid blood. The extent of dissemination varies con- medical treatment. In the Western countries, the average siderably. Bleeding on the surface of the brain spreads out annual incidence of SAH is estimated at 11 per 100,000 and collects later at the base, whereas a hemorrhage at population, with variations for age, sex, and geographic the base initially fills the cisterns. In cases of severe SAH, locations (56,62). The incidence of SAH has remained sta- the blood spreads within minutes over the convexities ble over the last 30 years. Saccular aneurysms account of the cerebral hemispheres. The average SAH releases for approximately 85% of SAH; nonaneurysmal perimes- 7to10mLofblood into the CSF. A red blood cell (RBC) P1: KWW/KKL P2: KWW/HCN QC: KWW/FLX T1: KWW GRBT050-109 Olesen- 2057G GRBT050-Olesen-v6.cls August 17, 2005 1:42 Unruptured Vascular Malformation and Subarachnoid Hemorrhage