Perimesencephalic hemorrhage. Exclusion of vertebrobasilar aneurysms with CT angiography

Subarachnoid hemorrhage without evident cause on initial angiography studies: diagnostic yield of subsequent angiography and other neuroimaging tests

OBJECT

The aim of this study was to assess the diagnostic yield of imaging tests performed in patients in whom the cause of subarachnoid hemorrhage (SAH) had not been demonstrated on initial angiography.

METHODS

By reviewing medical records of 806 patients with SAH who had been admitted during a 6.5-year period, the authors identified 86 in whom initial transfemoral catheter angiography failed to reveal the cause of SAH. Clinical and radiological data were analyzed to determine the diagnostic yield of subsequent catheter angiography, computerized tomography (CT) angiography, magnetic resonance (MR) angiography, and MR imaging of the brain and spine for various subtypes of SAH (bleeding not visualized on CT studies [CT-negative SAH], perimesencephalic SAH, and nonperimesencephalic SAH). Of 41 patients with nonperimesencephalic SAH, 36, 32, and 21 underwent repeated catheter angiography, CT angiography, and MR angiography, respectively; brain MR imaging was performed in 23 patients (18 with Gd and 15 with susceptibility contrast sequences), and spine MR imaging in 17. Of 36 patients with perimesencephalic SAH, 31, 23, and 17 underwent repeated catheter angiography, CT angiography, and MR angiography, respectively; brain MR imaging was performed in 18 patients (17 with Gd and 11 with susceptibility contrast sequences), and spine MR imaging in 14. Of nine patients with SAH not visualized on CT scanning, three, one, and six underwent repeated catheter angiography, CT angiography, and MR angiography, respectively; brain MR imaging was performed in eight patients (five with Gd and three with susceptibility contrast sequences), and spine MR imaging in seven. The cause of SAH could be determined in only four patients, all with nonperimesencephalic SAH. The only test that yielded a diagnosis was catheter angiography (three aneurysms on the second and one on the third angiography, all surgically secured). Diffusion-weighted MR imaging demonstrated small, deep infarcts in five patients.

CONCLUSIONS

Repeated catheter angiography remains the most sensitive test to determine the cause of SAH that is not demonstrated on initial angiography, particularly in the subtype of nonperimesencephalic SAH. Newer, noninvasive imaging techniques provide little diagnostic yield.

Presentation and management of patients with initial negative 4-vessel cerebral angiography in subarachnoid hemorrhage

The importance of repeat-angiography in patients with acute subarachnoid hemorrhage (SAH) and initial negative angiography has been reviewed in the light of our patient population (19 patients with initial negative angiography/168 patients with SAH). The type of SAH i.e., nontraumatic perimesencephalic SAH versus focal or generalized non perimesencephalic SAH, as well as the amount and distribution of blood on the initial CT examination are important factors in decision making. 3D-Angio-CT, in 3/5 patients, and MR-angiography (MRA) in 1/5 patients were complementary non-invasive methods to diagnose aneurysms on repeated examinations. Repeat-cerebral angiography confirmed the source of hemorrhage in 3 patients.

Comparison between perimesencephalic nonaneurysmal subarachnoid hemorrhage and subarachnoid hemorrhage caused by posterior circulation aneurysms

OBJECT

Some authors have questioned the need to perform cerebral angiography in patients presenting with a benign clinical picture and a perimesencephalic pattern of subarachnoid hemorrhage (SAH) on initial computerized tomography (CT) scans, because the low probability of finding an aneurysm does not justify exposing patients to the risks of angiography. It has been stated, however, that ruptured posterior circulation aneurysms may present with a perimesencephalic SAH pattern in up to 10% of cases. The aim of the present study was twofold: to define the frequency of the perimesencephalic SAH pattern in the setting of ruptured posterior fossa aneurysms, and to determine whether this clinical syndrome and pattern of bleeding could be reliably and definitely distinguished from that of aneurysmal SAH.

METHODS

Twenty-eight patients with ruptured posterior circulation aneurysms and 44 with nonaneurysmal perimesencephalic SAH were selected from a series of 408 consecutive patients with spontaneous SAH admitted to the authors' institution. The admission unenhanced CT scans were evaluated by a neuroradiologist in a blinded fashion and classified as revealing a perimesencephalic SAH or a nonperimesencephalic pattern of bleeding. Of the 28 patients with posterior circulation aneurysms, five whose grade was I according to the World Federation of Neurosurgical Societies scale were classified as having a perimesencephalic SAH pattern on the initial CT scan. The data show that the likelihood of finding an aneurysm on angiographic studies obtained in a patient with a perimesencephalic SAH pattern is 8.9%. Conversely, ruptured aneurysms of the posterior circulation present with an early perimesencephalic SAH pattern in 16.6% of cases.

CONCLUSIONS

This study supports the impression that there is no completely sensitive and specific CT pattern for a nonaneurysmal SAH. In addition, the authors believe that there is no specific clinical syndrome that can differentiate patients who have a perimesencephalic SAH pattern caused by an aneurysm from those without aneurysms. Digital subtraction angiography continues to be the gold standard for the diagnosis of cerebral aneurysms and should be performed even in patients who have the characteristic perimesencephalic SAH pattern on admission CT scans.

Subarachnoid hemorrhage of unknown origin and the basilar artery configuration

It is unclear whether the configuration of the basilar artery (BA) in patients with subarachnoid hemorrhage (SAH) of unknown origin is comparable to that in normal subjects or whether there are differences which may help to identify the origin. We studied the BA configuration in 57 patients with SAH of unknown origin (10%), who were identified in a prospectively collected series of 549 SAH patients consecutively admitted to our service over a 9-year period. There were 30 patients (53%) with non-perimesencephalic SAH and 27 with perimesencephalic SAH (47%). According to a standardized algorithm we determined, on straight anteroposterior digital subtraction angiography (DSA), the width of the proximal BA segment at the origin of the anterior inferior cerebellar artery and the width of the most distal BA segment between the superior cerebellar arteries and the posterior cerebral arteries. Based on these measurements we calculated the distal-proximal BA ratios and compared them to the ratios obtained in a control group of 31 patients who had DSA for reasons other than aneurysmal SAH. The mean ratio in patients with non-perimesencephalic SAH of unknown origin was 1.150 (range: 1.080-1.230). In patients with perimesencephalic SAH of unknown origin it was 1.156 (range: 1.120-1.250). In the control group the mean ratio was 1.163 (range: 1.125-1.200). There are no variations in the configurations of the BA which could possibly explain the cause of this type of SAH or clarify the origin of hemorrhage.

Complementary use of computed tomographic angiography in treatment planning for posterior fossa subarachnoid hemorrhage

OBJECTIVE

The goal of this study was to determine whether the complementary use of computed tomographic angiographic (CTA) assessments would provide additional benefits in the evaluation and treatment of ruptured vertebrobasilar artery aneurysms.

METHODS

In the past 4.5 years, 35 patients with an infratentorial dominant pattern of subarachnoid hemorrhage were complementarily examined with CTA scanning, after undergoing one or more three-dimensional rotational projection digital subtraction angiographic (DSA) studies. The results of these studies were interpreted by the treating neurosurgeon and an interventional radiologist, to examine the usefulness of the findings for the detection of aneurysms and to determine the grade of parent artery vascular filling and the optical definition of the aneurysm. This information provided additional benefits for case management.

RESULTS

Thirty-three aneurysms were detected. For 10 patients, no aneurysm was identified in repeated examinations with the two methods. We detected only 16 of the 25 ruptured aneurysms (64%) on the first DSA scans and, even with repeated examinations, 6 aneurysms were not clearly identified with this technique. CTA scanning revealed the ruptured aneurysms in 25 cases and demonstrated increased vascular filling and improved optical definition of the aneurysms, compared with DSA scanning, in 12 cases (48%). The information obtained from the CTA scans allowed the selection of five patients for endovascular treatment and facilitated the surgical procedures in five cases.

CONCLUSION

Complementary CTA examination of the vertebrobasilar complex provides a higher rate of aneurysm detection and improves the optical definition and anatomic projection of these aneurysms, compared with DSA scanning alone. This facilitates therapeutic decision-making (surgical versus endovascular procedures) and allows neurosurgeons to use more restricted surgical exposures.

[Idiopathic subarachnoid hemorrhage; comparison of different bleeding patterns and long-term outcome]

INTRODUCTION

Idiopathic subarachnoid haemorrhage (ISAH) represents approximately 15-30% of all subarachnoid haemorrhages. On the basis of the diagnostic CT and depending on the location of the subarachnoid bleeding, patients with ISAH may be classified into three groups: a) Patients with normal CT and diagnosis made by lumbar puncture (ISAHNCT); b) patients with a pure perimesencephalic pattern (ISAHPM) and c) patients with a bleeding pattern resembling that of aneurismatic rupture (ISAHA). This classification could permit the establishment of differences in the management and prognosis.

OBJECTIVES

To describe the clinical and radiological characteristics of these three classes of patients and analyse their medium and long term outcome and moreover, compare these with those observed in patients suffering aneurysmal subarachnoid haemorrhage (ASAH).

MATERIAL AND METHODS

A series of 122 patients consecutively admitted to Hospital 12 de Octubre Madrid between 1990 and 2000 with the diagnosis of ISAH were retrospectively reviewed. Patients were considered to have suffered ISAH when the first complete four vessel angiography did not show the presence of any aneurysm or vascular lesion responsible for the bleeding. Patients were classified depending on the pattern of bleeding into ISAHNCT, ISAHPM as described by Van Gijn et al., and ISAHA. The angiography study was repeated when: a) the first study was incomplete or had poor quality, b) vasospasm was present, c) in those patients who had an aneurysmal pattern of bleeding in the initial CT. Different clinical and radiological characteristics were recorded as well as complications that occurred during the hospital stay. Final outcome was evaluated by means of the Glasgow Outcome Score (GOS). With the purpose of comparing these clinical and radiological characteristics and the outcome of patients with ISAH with those suffering aneurysmal subarachnoid haemorrhage (ASAH), 294 patients diagnosed with ASAH during the same study period were also reviewed.

RESULTS

27% of patients admitted to our hospital with the diagnosis of non-traumatic subarachnoid hemorrhaged were diagnosed as ISAH. Of these, 41% presented with a ISAHA pattern, 39% ISAHPM and 20% ISAHNCT. The average age was similar in the different subgroups of SAH, being around 55 years. There was a greater frequency of male patients in the ISAHNCT and ISAHPM groups. In comparison with ASAH, ISAH characterises by patients presenting with less frequency a bad clinical grade and also loss of consciousness at stroke. There are fewer complications in patients with ISAH than ASAH, with a frequency of rebleeding and ischemia much less (5 and 6% respectively). Within the ISAH group, patients with ISAHA pattern of bleeding present more complications. Outcome is excellent for patients with ISAHNCT and ISAHPM, and rather worse for patients with ISAHA (median followup 5.8 years).

CONCLUSIONS

This study confirms that the frequency of ISAH in our environment reaches the higher limit of that shown previously in the literature, replicating the results previously published by our group. Patients with ISAH have a better prognosis and a smaller risk of complications than patients with ASAH, the prognosis of patients with ISAHCTN and ISAHPM being particularly good. Patients with ISAHA present initially with a severe clinical situation, probably related to the bigger amount of bleeding, as well as a higher frequency of systemic complications, cerebral ischemia and hydrocephalus. However, if the absence of vascular lesions is confirmed, the long term prognosis is similar to that of the other subgroups of ISAH.

Prognosis and prognostic factors in nonaneurysmal perimesencephalic hemorrhage: a follow-up study in 29 patients

BACKGROUND

Perimesencephalic nonaneurysmal hemorrhage is a benign form of subarachnoid hemorrhage with a low risk of rebleeding. The authors conducted a retrospective study to investigate the prognosis, possible prognostic factors, and long-term natural history in perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSH).

METHODS

This report contains a retrospective analysis of 29 patients with PNSH who were followed from 1 month to 8 years with an average follow-up period of 5.4 years. We evaluated computed tomography (CT) scan features; clinical grade; loss of consciousness during hemorrhage; ventricular ratio; angiographic spasm; complications such as ischemic complications, early rebleeding, late rebleeding, epilepsy, hydrocephalus, and fixed ischemic deficit; and outcome.

RESULTS

There were 7 men and 22 women, and the ages ranged from 22 to 69 years (mean 49.5 years). In the group with PNSH 93% of the patients were in grade I-II, as compared to 70.8% of patients with non-PNSH according to the Hunt and Hess system. Loss of consciousness during hemorrhage was detected in 9 patients (31%). We observed acute hydrocephalus in 4 patients (13.7%). The first cerebral four-vessel angiograms disclosed vasospasm in 3 patients (10.3%). Patients with PNSH have the best outcome according to the activities of daily living (ADL) grading system when compared with other groups of patients with negative angiogram (aneurysmal pattern and invisible blood).

CONCLUSION

This study provides evidence that patients with PNSH have an uncomplicated course and a particularly favorable outcome.

Diagnosis of perimesencephalic nonaneurysmal subarachnoid hemorrhage with computed tomography

OBJECTIVE

In 4% to 31% of patients with acute subarachnoid hemorrhage (SAH), no underlying cause is identified. Blood is restricted to the perimesencephalic cisterns in about two thirds of these patients. These patients are identified as having perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSAH), a syndrome based on the interpretation of computed tomography (CT) findings on admission, with an excellent prognosis, far better than other patients with SAH with or without an aneurysm. However, the diagnosis is subject to interrater variability, and differentiation between PNSAH and ruptured supratentorial aneurysm by means of CT has not been investigated. Therefore we investigated the validity of prediction of PNSAH with CT scan.

METHODS

A total of 303 consecutive patients, admitted within 72 hours after the initial bleeding with symptoms and signs of spontaneous SAH, which was confirmed by CT or spectrophotometric analysis of the cerebrospinal fluid (CSF) in whom either a selective 4-vessel angiogram (n = 293) or postmortem examination (n = 10) was performed, were studied.

RESULTS

We found an interrater agreement for the diagnosis perimesencephalic nonaneurysmal subarachnoid hemorrhage of 93% and a kappa value of 0.65. Sensitivity was 30% for observer 1 and 46% for observer 2. The positive predictive value was 73% for observer 1 and 76% for observer 2. Among those diagnosed as having PNSAH, we found vertebrobasilar artery aneurysms in 19% (both raters) and internal carotid artery aneurysms in 5% (observer 1) and 8% (observer 2).

CONCLUSION

We conclude that PNSAH can be distinguished on CT in the majority of patients; however, the angiographical management in PNSAH should not differ from other SAHs.

Subarachnoid haemorrhage: diagnosis, causes and management

The incidence of subarachnoid haemorrhage (SAH) is stable, at around six cases per 100 000 patient years. Any apparent decrease is attributable to a higher rate of CT scanning, by which other haemorrhagic conditions are excluded. Most patients are <60 years of age. Risk factors are the same as for stroke in general; genetic factors operate in only a minority. Case fatality is approximately 50% overall (including pre-hospital deaths) and one-third of survivors remain dependent. Sudden, explosive headache is a cardinal but non-specific feature in the diagnosis of SAH: in general practice, the cause is innocuous in nine out of 10 patients in whom this is the only symptom. CT scanning is mandatory in all, to be followed by (delayed) lumbar puncture if CT is negative. The cause of SAH is a ruptured aneurysm in 85% of cases, non-aneurysmal perimesencephalic haemorrhage (with excellent prognosis) in 10%, and a variety of rare conditions in 5%. Catheter angiography for detecting aneurysms is gradually being replaced by CT angiography. A poor clinical condition on admission may be caused by a remediable complication of the initial bleed or a recurrent haemorrhage in the form of intracranial haematoma, acute hydrocephalus or global brain ischaemia. Occlusion of the aneurysm effectively prevents rebleeding, but there is a dearth of controlled trials assessing the relative benefits of early operation (within 3 days) versus late operation (day 10-12), or that of endovascular treatment versus any operation. Antifibrinolytic drugs reduce the risk of rebleeding, but do not improve overall outcome. Measures of proven value in decreasing the risk of delayed cerebral ischaemia are a liberal supply of fluids, avoidance of antihypertensive drugs and administration of nimodipine. Once ischaemia has occurred, treatment regimens such as a combination of induced hypertension and hypervolaemia, or transluminal angioplasty, are plausible, but of unproven benefit.