Routine Screening of First-Degree Relatives of Patients With Sporadic SAH is Not Necessary
abstract & commentary
Source: The Magnetic Resonance Angiography in Relatives of Patients with Subarachnoid Hemorrhage Study Group. Risks and benefits of screening for intracranial aneurysms in first-degree relatives of patients with sporadic subarachnoid hemorrhage. N Engl J Med 1999;341:1344-1350.
The risk of subarachnoid hemorrhage (sah) among first-degree relatives of affected persons is three to seven times greater than in the general population (Bromberg JE, et al. BMJ 1995;311:288-289; Schievink WI, et al. J Neurosurg 1995;83:426-429). Magnetic resonance angiography (MRA) can detect intracranial aneurysms and makes possible noninvasive screening of asymptomatic individuals.
The Dutch Group studied the risks and benefits of screening first-degree relatives of 160 patients with sporadic SAH. MRA was used to screen 626 first-degree relatives (30 parents, 346 siblings, and 250 children). Their mean age was 41 ± 12 years and 325 were women. Conventional angiography was used in subjects thought to have aneurysms on the basis of the MRA results. Six months after elective surgery outcome was assessed by means of the modified Rankin scale of neurologic function. The efficiency of screening was defined by the number of relatives who needed to be screened in order prevent one SAH.
MRA disclosed one or more definite aneurysms in 18 subjects, possible aneurysms in 30, and no aneurysms in 578. Two subjects with definite aneurysms declined further assessment. Including these two, the study found 33 unruptured aneurysms in 25 of 626 first-degree relatives (4.0%).
Eighteen of 25 relatives underwent elective surgery. Five of the 18 patients had medium-sized aneurysms (5-11 mm in diameter), 11 had small aneurysms (< 5 mm in diameter), and two had both small and medium-sized aneurysms. At surgery, all aneurysms were clipped except for one aneurysm in the cavernous sinus in a subject with multiple aneurysms.
Surgery increased estimated average life expectancy by a total of 2.5 years (from 32.5-35.0 years) or by four weeks per person screened. In 11 of 18, surgery resulted in a decrease in function that was disabling in one person. If these sequelae persist for an average of 21 of the expected 35 years of life after surgery compared to an average of only two years of disability expected from SAH in the 32.5 remaining years of life in unoperated subjects, the difference is 19 average years of decreased function per surgical person.
The number of relatives who would need to be screened in order to prevent one SAH on a lifetime basis was 149, and 298 would have to be screened in order to prevent one fatal SAH. The group, therefore, concludes that screening first-degree relatives of patients with sporadic SAH is not warranted.
Estimates of the risk of rupture of intact aneurysms and the outcome after SAH hemorrhage available from previous studies were used to calculate life expectancy. Previous studies (Rinkel GJE, et al. Stroke 1998;29:251-256) have shown a clear association between rates of rupture and size of aneurysms. The rupture rate for aneurysms less than 10 mm in diameter may be less than 0.05% per year (The International Study of Unruptured Intracranial Aneurysms Investigators. N Engl J Med 1998;339:1725-1733). The present group initially used a higher value of 0.5% annual risk of rupture for aneurysms smaller than 5 mm in diameter. This figure may better represent the risk of rupture in persons with familial cases, based on the recent finding that asymptomatic aneurysms are more likely to rupture in relatives of patients with SAH than in relatives of patients with unruptured aneurysms (Kojima M, et al. Neurosurgery 1998;43:776-781). Nevertheless, one may question the wisdom of operating on patients with unruptured small aneurysms.
The group found a prevalence of unruptured aneurysms (4%) that is twice the prevalence in the general population as derived from autopsy and angiographic studies (Rinkel GJE, et al. Stroke 1998;29:251-256) but is one-half the 8% prevalence among persons who have at least two relatives with SAH (Ronkainen A, et al. Lancet 1997;349:380-384; Raaymakers TW, et al. Neurology 1998;51:1125-1130). It is possible that their figure of 4% is an underestimation because of the limited sensitivity of MRA in detecting small aneurysms (Atlas SW, et al. Radiology 1997;203:807-814).
The study confirms that the angiographic evaluation and surgical treatment of intracranial aneurysms have risks and that positive and negative effects, as well as costs, must be taken into account when making general recommendations about a screening program such as the one reported. It remains for the individual physician, when relatives of a patient with sporadic SAH seek advice, to weigh the pros and cons of screening in making a recommendation for further diagnostic imaging and elective surgery. The study conclusions were "Implication of a screening program for first-degree relatives of patients with sporadic subarachnoid hemorrhage does not seem warranted at this time. . . ," Neurology Alert agrees. —jjc
The percent prevalence of unruptured aneurysms among persons who have at least two relatives with SAH is: