(Stroke. 1999;30:1974-1981.)
© 1999 American Heart Association, Inc.
Letters to the Editor |
Perimesencephalic Hemorrhage
Interventional Radiology, Radiology Department, Emory University Hospital, Atlanta, Georgia
Key Words: cerebral aneurysm • angiography, digital
subtraction • tomography, x-ray computed
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To the Editor:
The article by Velthuis et al1 in the May 1999 issue of Stroke was an interesting case series, but I feel that their results do not logically lead to their conclusions. A small series of 16 patients with perimesencephalic hemorrhage with no aneurysm detected on CT angiography or digital subtraction angiography (DSA) does not prove that CT angiography alone is adequate for the detection of cerebral aneurysms in patient with perimesencephalic subarachnoid hemorrhage.
Velthuis et al1 are proposing that CT angiography is an adequate screening examination for cerebral aneurysms in patients with perimesencephalic hemorrhage. The most important issue in a screening study is sensitivity, not specificity. In their discussion, Velthuis et al point out that the specificity of CT angiography for the detection of cerebral aneurysms is 89% to 100%, according to a number of references.2 3 4 5 6 7 8 9 They do not discuss the fact that the sensitivity of CT angiography in these studies ranged from 67% to 96%.2 3 4 5 6 7 8 9 In fact, Velthuis et al reported in a study5 that CT angiography at their institution depicted 90% of aneurysms confirmed with DSA. One must assume that this 90% sensitivity of CT angiography at their institution also applies to vertebrobasilar aneurysms in patients with perimesencephalic hemorrhage. If one fails to detect 10% of aneurysms that present with the perimesencephalic hemorrhage pattern, and 5% of patients with this pattern actually have an aneurysm,1 a ruptured aneurysm will not be detected in about 0.5% of cases. The risk of rebleeding from a ruptured aneurysm without surgery or endovascular treatment is between 20% and 30% for the first month after hemorrhage.10 Patients who rebleed from ruptured aneurysms have an 80% mortality rate.11 The risk of CT angiography in patients with perimesencephalic subarachnoid hemorrhage can be summarized as follows: (1) because there is an approximately 5% risk that the patient has a ruptured aneurysm, there is a 0.5% risk that a ruptured aneurysm will not be detected by the CT angiogram; (2) this translates into a 0.13% risk that such an undetected ruptured aneurysm will rebleed; and (3) there is an approximately 0.1% risk that the patient will die from rebleeding of the undetected aneurysm within 1 month. The risk of permanent neurological complication associated with cerebral angiography in patients with subarachnoid hemorrhage, cerebral aneurysm, and arteriovenous malformation is known to be extremely low (0.07%) from a meta-analysis of recent, prospective studies.12 The neurological deficits complicating angiography tend to be much less severe than the morbidity and mortality caused by rebleeding of a ruptured aneurysm.
If the diagnostic value of CT angiography is less than that of DSA, and the risk of missing an aneurysm by performing CT angiography is higher than the risk of DSA, how can one contend that CT angiography is preferrable in patients with perimesencephalic hemorrhages? CT angiography has been touted as being useful for patients who are too critically ill to undergo the delay necessary for angiography prior to surgery. However, based on the definition of the clinical syndrome associated with perimesencephalic hemorrhage, these patients are not critically ill. One might argue that CT angiography is less expensive than DSA and therefore more cost effective, but this would have to be evaluated with a cost-effectiveness study. In this select group of patients with perimesencephalic hemorrhage, the rate of aneurysm detection on a second angiogram may, in fact, be too low to warrant a second angiogram if no aneurysm is detected on an initial DSA.13 But the diagnostic value of performing an initial study with DSA rather than CT angiography in patients with perimesencephalic subarachnoid hemorrhage is quite clear at the present time.
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References |
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TopIntroductionReferencesIntroduction References |
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1. Velthuis BK, Rinkel GJ, Ramos LM, Witkamp TD, van Leeuwen MS. Perimesencephalic hemorrhage: exclusion of vertebrobasilar aneurysms with CT angiography. Stroke. 1999;30:1103–1109.
2. Anderson GB, Findlay JM, Steinke DE, Ashforth R. Experience with computed tomographic angiography for the detection of intracranial aneurysms in the setting of acute subarachnoid hemorrhage. Neurosurgery. 1997;41:522–527.[Medline] [Order article via Infotrieve]
3. Hope JK, Wilson JL, Thomson FJ. Three-dimensional CT angiography in the detection and characterization of intracranial berry aneurysms. AJNR Am J Neuroradiol.. 1996;17:439–445.[Abstract]
4. Alberico RA, Patel M, Casey S, Jacobs B, Maguire W, Decker R. Evaluation of the circle of Willis with three-dimensional CT angiography in patients with suspected intracranial aneurysms. AJNR Am J Neuroradiol. 1995;16:1571–1578.[Abstract]
5.
Velthuis BK, Rinkel GJ, Ramos LM, Witkamp TD, van der
Sprenkel JW, Vandertop WP, van Leeuwen MS. Subarachnoid
hemorrhage: aneurysm detection and preoperative
evaluation with CT angiography. Radiology. 1998;208:423–430.
6.
Liang EY, Chan M, Hsiang JH, Walkden SB, Poon WS, Lam
WW, Metreweli C. Detection and assessment of intracranial
aneurysms: value of CT angiography with shaded-surface display.
AJR Am J Roentgenol. 1995;165:1497–1502.
7. Ogawa T, Okudera T, Noguchi K, Sasaki N, Inugami A, Uemura K, Yasui N. Cerebral aneurysms: evaluation with three-dimensional CT angiography. AJNR Am J Neuroradiol. 1996;17:447–454.[Abstract]
8. Lenhart M, Bretschneider T, Gmeinwieser J, Ullrich OW, Schlaier J, Feuerbach S. Cerebral CT angiography in the diagnosis of acute subarachnoid hemorrhage. Acta Radiol. 1997;38:791–796.[Medline] [Order article via Infotrieve]
9. Zouaoui A, Sahel M, Marro B, Clemenceau S, Dargent N, Bitar A, Faillot T, Capelle L, Marsault C. Three-dimensional computed tomographic angiography in detection of cerebral aneurysms in acute subarachnoid hemorrhage. Neurosurgery. 1997;41:125–130.[Medline] [Order article via Infotrieve]
10. Mayberg MR, Batjer HH, Dacey R, Diringer M, Haley EC, Heros RC, Sternau LL, Torner J, Adams HP Jr, Feinberg W, Thies W. Guidelines for the management of aneurysmal subarachnoid hemorrhage: a statement for healthcare professionals from a special writing group of the Stroke Council, American Heart Association. Stroke. 1994;25:2315–2328.[Medline] [Order article via Infotrieve]
11. Rosenom J, Eskesen V, Schmidt K, Ronde F. The risk of rebleeding from ruptured intracranial aneurysms. J Neurosurg. 1987;67:329–332.[Medline] [Order article via Infotrieve]
12.
Cloft HJ, Joseph GJ, Dion JE. Risk of cerebral
angiography in patients with subarachnoid hemorrhage,
cerebral aneurysm, and arteriovenous malformation: a
meta-analysis. Stroke. 1999;30:317–320.
13.
Cloft HJ, Kallmes DF, Dion JE. A second look at the
second-look angiogram in cases of subarachnoid
hemorrhage. Radiology. 1997;205:323–324.
Response
University of Utrecht, Utrecht, the Netherlands
Key Words: cerebral aneurysm • angiography, digital
subtraction • tomography, x-ray computed
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We thank Dr Cloft for his interest in our article.1 He is concerned about the risk of missing a vertebrobasilar aneurysm with CT angiography in the assessment of patients with perimesencephalic pattern of hemorrhage. Based on our numbers of patients, he maintains that intra-arterial DSA is still warranted in patients with a perimesencephalic pattern of hemorrhage and a normal CT angiogram. We believe that several assumptions are incorrect in his line of reasoning.
First, Dr Cloft feels that sensitivity (ie, the chance of finding an aneurysm by CT angiography given that an aneurysm is present) is the most important test characteristic. We think that the negative predictive value (ie, the chance that no aneurysm is present in patients with a negative CT angiography) is more important for clinicians. In our study we had 16 patients with vertebrobasilar aneurysms and 24 patients with no aneurysm.1
Second, the sensitivity (90%) we found in a previous study,2 which was based on patients with subarachnoid hemorrhage from all aneurysm locations, including aneurysms of the carotid circulation, cannot be directly applied to the subset of patients who are at risk for ruptured vertebrobasilar aneurysms. The 90% sensitivity refers to detection of both symptomatic and asymptomatic additional aneurysms and includes 24% of CT angiography examinations of suboptimal quality. The majority of missed aneurysms are additional aneurysms located on the carotid circulation. The sensitivity for symptomatic aneurysms in this study was 95%. In patients with perimesencephalic pattern of hemorrhage, we want to exclude a symptomatic vertebrobasilar aneurysm on a CT angiography of good quality. CT angiograms of inadequate quality are either repeated or intra-arterial angiography is performed. The actual sensitivity in our present series is 100%; the true sensitivity will of course be less than 100%, but we feel it is realistic to expect that it is higher than 95% (probably around 97%).
Third, the 0.07% risk of intra-arterial angiography found in the recent review cannot directly be applied to patients with perimesencephalic hemorrhage.3 These patients need bilateral vertebral angiography, which probably carries greater risk than carotid or 3-vessel angiography. A subset of patients with bilateral vertebral angiography can not be extracted from the review. Moreover, the 0.07% risk for permanent neurological complication with intra-arterial cerebral angiography is combined for patients with subarachnoid hemorrhage and patients with cerebral aneurysms or arteriovenous malformations but without subarachnoid hemorrhage. The permanent neurological risk for patients with subarachnoid hemorrhage in this analysis is higher (0.3%). The case fatality rate of 80% after a rebleed is based on data from another era.4 In those days, patients with a rebleed were left untreated for 12 days after the rebleed, thereby inducing time for further rebleed. Nowadays, patients who rebleed are treated as soon as possible after the rebleed. The fact that more aneurysms are found on digital subtraction angiography than on CT angiography does not necessarily imply that digital subtraction angiography has a better diagnostic value. In our clinical practice CT angiography is performed immediately after admission and before digital subtraction angiography. This means that the results of CT angiography are at hand when intra-arterial angiography is performed, and therefore the intra-arterial angiography is guided by the results of CT angiography. We have observed several patients in whom the standard projections of intra-arterial angiography did not reveal the aneurysm, and only after additional projections guided by the CT angiography was the aneurysm found on intra-arterial angiography. It is well known that the sensitivity of intra-arterial angiography is not optimal. Combined data of 7 studies regarding patients with subarachnoid hemorrhage and negative intra-arterial angiograms revealed 22 aneurysms in 145 repeat angiograms.5 Even if we follow the calculation done by Dr Cloft but incorporate a sensitivity of at least 95% (which is presumably too low), the chance of missing an aneurysm in patients with a perimesencephalic pattern of hemorrhage is, at the highest, 0.25%.
The chance of having an aneurysm for patients with a perimesencephalic pattern of hemorrhage and a negative CT angiography can be calculated by means of the likelihood ratio. Assuming a 5% risk of an aneurysm in patients with a perimesencephalic pattern of hemorrhage and a sensitivity and specificity of 97% (in our study both were 100%), the likelihood ratio is 0.03 and the chance of an aneurysm after a negative CT angiographic scan of good quality is 0.1% (1 per 1000).
We feel that these chances of having an aneurysm in patients with a perimesencephalic pattern of hemorrhage and a negative CT angiogram are too small to warrant bilateral vertebral angiography.
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References |
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TopIntroductionReferencesIntroduction References |
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1. Velthuis BK, Rinkel GJE, Ramos LMP, Witkamp TD, van Leeuwen MS. Perimesencephalic hemorrhage: exclusion of vertebrobasilar aneurysms with CT angiography. Stroke. 1999;30:1103–1109.
2. Velthuis BK, Rinkel GJE, Ramos LMP, Witkamp TD, Berkelbach van der Sprenkel JW, Vandertop WP, van Leeuwen MS. Subarachnoid hemorrhage: aneurysm detection and preoperative evaluation with CT angiography. Radiology. 1998;208:423–430.
3. Cloft HJ, Joseph GJ, Dion JE. Risk of cerebral angiography in patients with subarachnoid hemorrhage, cerebral aneurysm, and arteriovenous malformation: a meta-analysis. Stroke. 1999;30:317–320.
4. Hijdra A, Vermeulen M, van Gijn J, Crevel II, van. Rerupture of intracranial aneurysms: a clinicoanatomic study. J Neurosurg. 1987;67:29–33.[Medline] [Order article via Infotrieve]
5. Rinkel GJE, Wijdicks EFM. Subarachnoid hemorrhage without detectable aneurysm. In: Yanagihara T, Piepgras DG, eds. Subarachnoid Hemorrhage: Medical and Surgical Management. New York, NY: Marcel Dekker; 1997:139–158.
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