How often is a perimesencephalic subarachnoid haemorrhage CT pattern caused by ruptured aneurysms?

Subarachnoid Hemorrhage of Unknown Cause: Distribution and Role of Imaging

Subarachnoid hemorrhage of unknown cause represents approximately 10% to 15% of nontraumatic subarachnoid hemorrhages. The key factors in determining the management strategy for a presumed nonaneurysmal subarachnoid hemorrhage are the distribution, location, and amount of subarachnoid blood. Hemorrhage distribution on computed tomography can be categorized as follows: perimesencephalic, diffuse, sulcal, and primary intraventricular. The extent of the workup required in determining the cause of hemorrhage depends on the distribution of blood. The authors review the potential causes, differential diagnoses, and acute and long-term follow-up strategies in patients with subarachnoid hemorrhage of unknown cause.

Nonaneurysmal Perimesencephalic Hemorrhage Is Associated with Deep Cerebral Venous Drainage Anomalies: A Systematic Literature Review and Meta-Analysis

BACKGROUND AND PURPOSE

Mechanisms underlying bleeding in nonaneurysmal perimesencephalic SAH remain unclear. Previous investigators have suggested a relationship between nonaneurysmal perimesencephalic SAH and primitive venous drainage of the basal vein of Rosenthal. We performed a meta-analysis to evaluate the relation between primitive basal vein of Rosenthal drainage and nonaneurysmal perimesencephalic SAH.

MATERIALS AND METHODS

We performed a comprehensive literature search of all studies examining the prevalence of primitive basal vein of Rosenthal drainage in patients with aneurysmal SAH and nonaneurysmal perimesencephalic SAH. Data collected were primitive basal vein of Rosenthal drainage (direct connection of perimesencephalic veins into the dural sinuses instead of the Galenic system) in at least 1 cerebral hemisphere, normal bilateral basal vein of Rosenthal drainage systems, and the number of overall primitive venous systems in the nonaneurysmal perimesencephalic SAH and aneurysmal SAH groups. Statistical analysis was performed by using a random-effects meta-analysis.

RESULTS

Eight studies with 888 patients (334 with nonaneurysmal perimesencephalic SAH and 554 with aneurysmal SAH) and 1657 individual venous systems were included. Patients with nonaneurysmal perimesencephalic SAH were more likely to have a primitive basal vein of Rosenthal drainage in at least 1 hemisphere (47.7% versus 22.1%; OR, 3.31; 95% CI, 2.15-5.08; P < .01) and were less likely to have bilateral normal basal vein of Rosenthal drainage systems than patients with aneurysmal SAH (18.3% versus 37.4%; OR, 0.27; 95% CI, 0.14-0.52; P < .01). When we considered individual venous systems, there were higher rates of primitive venous systems in patients with nonaneurysmal perimesencephalic SAH than in patients with aneurysmal SAH (34.9% versus 15.3%; OR, 3.90; 95% CI, 2.37-6.43; P < .01).

CONCLUSIONS

Patients with nonaneurysmal perimesencephalic SAH have a higher prevalence of primitive basal vein of Rosenthal drainage in at least 1 hemisphere than patients with aneurysmal SAH. This finding suggests a venous origin of some nonaneurysmal perimesencephalic SAHs. A primitive basal vein of Rosenthal pattern is an imaging finding that has the potential to facilitate the diagnosis of nonaneurysmal perimesencephalic SAH.

Quadrigeminal perimesencephalic subarachnoid hemorrhage

OBJECTIVE

A variant of perimesencephalic subarachnoid hemorrhage (PSAH) has been described characterized by blood centered in the quadrigeminal cistern and limited to the superior vermian and perimesencephalic cisterns. Herein, three cases of quadrigeminal PSAH are presented.

MATERIALS AND METHODS

Medical records of all patients who underwent digital subtraction angiography for evaluation of non-traumatic SAH between July 2002 and April 2012 were reviewed. Patients with anterior circulation aneurysms were excluded. Two blinded reviewers identified admission noncontrast CT scans with pretruncal and quadrigeminal patterns of PSAH.

RESULTS

The total cohort included 106 patients: 53% (56/106) with one or more negative digital subtraction angiograms and 47% (50/106) with posterior circulation or posterior communicating artery aneurysms. Three patients with quadrigeminal PSAH were identified, two with nonaneurysmal SAH and one with a posterior circulation aneurysm. Seventeen patients (16%; 17/106) with pretruncal PSAH were identified, none of whom were found to have an aneurysm. The quadrigeminal pattern comprised 11% (2/19) of cases of pretruncal or quadrigeminal nonaneurysmal PSAH.

CONCLUSION

A small subset of patients with nonaneurysmal PSAH present with blood centered in the quadrigeminal cistern, and the etiology of this pattern may be similar to that of the classic pretruncal variant. However, patients with quadrigeminal PSAH must still undergo thorough vascular imaging, including at least two digital subtraction angiograms, to exclude a ruptured aneurysm.

Evaluation of an anatomic definition of non-aneurysmal perimesencephalic subarachnhoid hemorrhage

Background and purpose

Perimesencephalic subarachnoid hemorrhage (PSAH) is not consistently defined in the existing literature. The purpose of this study was to test the inter-observer variability and specificity for non-aneurysmal subarachnoid hemorrhage (SAH) of an anatomic definition of PSAH.

Methods

Medical records of all patients who underwent catheter angiography for evaluation of non-traumatic SAH between July 2002 and April 2012 were reviewed. Patients with anterior circulation aneurysms were excluded. Three blinded reviewers assessed whether each admission CT scan met the following anatomic criteria for PSAH: (1) center of bleeding located immediately anterior and in contact with the brainstem in the prepontine, interpeduncular, or posterior suprasellar cistern; (2) blood limited to the prepontine, interpeduncular, suprasellar, crural, ambient, and/or quadrigeminal cisterns and/or cisterna magna; (3) no extension of blood into the Sylvian or interhemispheric fissures; (4) intraventricular blood limited to incomplete filling of the fourth ventricle and occipital horns of the lateral ventricles (ie, consistent with reflux); (5) no intraparenchymal blood.

Results

56 patients with non-aneurysmal SAH and 50 patients with posterior circulation or posterior communicating artery aneurysms were identified. Seventeen (16%) of the 106 admission CT scans met the anatomic criteria for PSAH. No aneurysm was identified in this subgroup. Inter-observer agreement was excellent with κ scores of 0.89–0.96 and disagreement in 2.8% (3/106) of cases.

Conclusions

Our anatomic definition of PSAH correlated with a low risk of brain aneurysm and was applied with excellent inter-observer agreement.

Use of Follow-Up Imaging in Isolated Perimesencephalic Subarachnoid Hemorrhage

Background and Purpose—

Multiple studies have shown that negative computed tomographic angiograms (CTAs) are reliable in excluding aneurysms in patients with isolated perimesencephalic subarachnoid hemorrhage (pSAH). We evaluate the use of digital subtraction angiography versus CTA for initial diagnosis and of angiographic follow-ups in patients with pSAH by performing an institutional analysis and a meta-analysis of literature.

Methods—

Retrospective institutional analysis of patients with pSAH was performed from 2008 to 2014. The number and types of follow-up imaging studies were tabulated. Initial and follow-up studies were evaluated by an experienced neuroradiologist for intracranial aneurysm. Meta-analysis of literature was performed to assess the use of initial digital subtraction angiography and of follow-up imaging.

Results—

Our institutional review revealed no additional use of initial digital subtraction angiography or of any angiographic follow-up after initial negative CTA in patients with pSAH on noncontrast CT. Meta-analysis of 40 studies yielded a total of 1031 patients. Only 8 aneurysms were first diagnosed on follow-ups (0.78%). Careful review showed that some of these aneurysms reported on follow-up are of questionable validity. Initial digital subtraction angiography and follow-up imaging after a negative initial CTA showed no statistically significant benefits.

Conclusions—

In patients meeting the strict imaging criteria of pSAH, initial negative CTA is reliable in excluding aneurysms. A critical review of the literature through meta-analysis shows no foundation for multiple follow-up studies in patients with pSAH.

Spontaneous subarachnoid hemorrhage of unknown origin: hospital course and long-term clinical and angiographic follow-up

OBJECT

Hemorrhagic origin is unidentifiable in 10%-20% of patients presenting with spontaneous subarachnoid hemorrhage (SAH). While the patients in such cases do well clinically, there is a lack of long-term angiographic followup. The authors of the present study evaluated the long-term clinical and angiographic follow-up of a patient cohort with SAH of unknown origin that had been enrolled in the Barrow Ruptured Aneurysm Trial (BRAT).

METHODS

The BRAT database was searched for patients with SAH of unknown origin despite having undergone two or more angiographic studies as well as MRI of the brain and cervical spine. Follow-up was available at 6 months and 1 and 3 years after treatment. Analysis included demographic details, clinical outcome (Glasgow Outcome Scale, modified Rankin Scale [mRS]), and repeat vascular imaging.

RESULTS

Subarachnoid hemorrhage of unknown etiology was identified in 57 (11.9%) of the 472 patients enrolled in the BRAT study between March 2003 and January 2007. The mean age for this group was 51 years, and 40 members (70%) of the group were female. Sixteen of 56 patients (28.6%) required placement of an external ventricular drain for hydrocephalus, and 4 of these subsequently required a ventriculoperitoneal shunt. Delayed cerebral ischemia occurred in 4 patients (7%), leading to stroke in one of them. There were no rebleeding events. Eleven patients were lost to followup, and one patient died of unrelated causes. At the 3-year follow-up, 4 (9.1%) of 44 patients had a poor outcome (mRS > 2), and neurovascular imaging, which was available in 33 patients, was negative.

CONCLUSIONS

Hydrocephalus and delayed cerebral ischemia, while infrequent, do occur in SAH of unknown origin. Long-term neurological outcomes are generally good. A thorough evaluation to rule out an etiology of hemorrhage is necessary; however, imaging beyond 6 weeks from ictus has little utility, and rebleeding is unexpected.

Nonaneurysmal perimesencephalic subarachnoid hemorrhage: diagnosis, pathophysiology, clinical characteristics, and long-term outcome

Patients with nonaneurysmal perimesencephalic subarachnoid hemorrhage (NAPSAH) have no discernible source for the bleeding and generally are considered to have a benign condition. Correctly diagnosing these patients is essential because a missed aneurysm can have catastrophic consequences. Those presenting with NAPSAH have a low risk of complications and better outcome than patients presenting with aneurysmal subarachnoid hemorrhage; however, a limited body of literature suggests that not all of these patients are able to return to their premorbid functional status. Clinical screens of cognitive status, such as the mini-mental status examination, suggest good recovery of these patients, although these tests may lack sensitivity for identifying deficits in this patient population. More comprehensive neuropsychologic testing in some studies has identified deficits in a wide range of cognitive domains at long-term follow-up in patients with NAPSAH. Because these patients often do not lose consciousness (and thus do not have substantial transient global ischemia) and they do not undergo a procedure for aneurysm repair, the cognitive sequelae can be explained by the presence of blood in the subarachnoid space. NAPSAH presents an opportunity to understand the effects of subarachnoid blood in a clinical setting.

Angiogram-negative subarachnoid hemorrhage: relationship between bleeding pattern and clinical outcome

BACKGROUND

Angiogram-negative subarachnoid hemorrhage (anSAH) accounts for 15% of spontaneous SAH. Recent studies suggest the outcome and diagnostic yield in anSAH differ based on initial bleeding pattern. We present a single-center experience in managing patients with SAH and negative initial digital-subtracted angiogram (DSA).

METHODS

Records of all patients with anSAH were reviewed. Bleeding pattern was determined from computed tomography (CT) and was categorized as perimesencephalic (PMN), diffuse, cortical, or xanthochromia (blood not detectable by CT). Diagnostic yield, in-hospital complications, and outcome parameters were analyzed.

RESULTS

Of 352 patients admitted with spontaneous SAH from 2003 to 2008, 68 (19.3%) had negative initial DSA. Mean age was 59.5 ± 14, and 33 were female. By CT, 27 (39.7%) patients exhibited PMN SAH, 33 (48.5%) diffuse SAH, 6 (8.8%) cortical SAH, and 2 (2.9%) xanthochromia only. Sixty-one patients had good Hunt and Hess (H/H) grades (I-III) and seven had poor grades (IV-V). Additional diagnostic studies included repeat angiogram (54), brain and C-spine magnetic resonance imaging (20), and repeat CTA (15). A structural bleeding cause was determined in six (8.8%) patients, 4 of which had diffuse SAH and 2 cortical SAH. Among these, two aneurysms (2.9%) were detected and surgically clipped, and both had diffuse SAH. Twenty-nine patients (42.6%) experienced medical complications, with infection (18), cardiovascular problems (12), and vasospasm (10) being the most frequent events. Additional surgeries included 13 ventriculoperitoneal shunts, 4 tracheostomies, and 9 gastric tube placements. Favorable outcome (mRS = 0-2) was recorded in 49 (72.1%) patients and unfavorable (3-6) in 19 (17.49%), with 1 (1.2%) in-hospital death. Multivariable logistic regression revealed older age and diffuse bleeding pattern were significant predictors of unfavorable outcome.

CONCLUSIONS

The overall incidence of true aneurysms in patients with angiogram-negative SAH is low (2.9%). Initial bleeding pattern strongly correlates with diagnostic yield and clinical outcome. Diffuse bleeding pattern is associated with significantly higher diagnostic yield, more in-hospital complications, and worse clinical outcome. Patients with initial imaging characteristics other than diffuse pattern SAH developed few disease related complications, with the majority of in-hospital adverse events treatment related.

Cerebral aneurysm exclusion by CT angiography based on subarachnoid hemorrhage pattern: a retrospective study

Background

To identify patients with spontaneous subarachnoid hemorrhage for whom CT angiography alone can exclude ruptured aneurysms.

Methods

An observational retrospective review was carried out of all consecutive patients with non-traumatic subarachnoid hemorrhage who underwent both CT angiography and catheter angiography to exclude an aneurysm. CT angiography negative cases (no aneurysm) were classified according to their CT hemorrhage pattern as "aneurismal", "perimesencephalic" or as "no-hemorrhage."

Results

Two hundred and forty-one patients were included. A CT angiography aneurysm detection sensitivity and specificity of 96.4% and 96.0% were observed. All 35 cases of perimesencephalic or no-hemorrhage out of 78 CT angiography negatives also had negative angiography findings.

Conclusions

CT angiography is self-reliant to exclude ruptured aneurysms when either a perimesencephalic hemorrhage or no-hemorrhage pattern is identified on the CT within a week of symptom onset.

Inter- and intraobserver agreement in CT characterization of nonaneurysmal perimesencephalic subarachnoid hemorrhage

BACKGROUND AND PURPOSE

The perimesencephalic pattern of SAH as seen on unenhanced CT is associated with significantly better outcomes when compared to an aneurysmal pattern of SAH. The aim of this study was to determine the degree of inter- and intraoberver agreement for characterization of the NAPH as seen on unenhanced CT.

MATERIALS AND METHODS

We retrospectively reviewed the CT scans of 37 patients with spontaneous SAH, all of whom had undergone CT within 24 hours of onset of headache symptoms. All patients had undergone conventional cerebral angiography to confirm or exclude aneurysms or other vascular pathology. All 37 cases were angiographically confirmed nonaneurysmal SAHs. Four readers with neuroradiology subspecialty training independently evaluated CT images to characterize the hemorrhage pattern as compatible with the well-described NAPH. Each reader performed a second reading session blinded to the initial readings. The first and second sets of readings were performed approximately 4 months apart. Inter- and intraobserver agreement for characterization of the NAPH was determined by using the kappa statistic.

RESULTS

Of the 37 angiographically confirmed nonaneurysmal SAHs, there was unanimous agreement as to the hemorrhage pattern in 29 (78%) cases and disagreement in 8 (22%) cases. Overall, intraobserver agreement was good (kappa = 0.80). Interobserver agreement was also good (kappa = 0.79).

CONCLUSIONS

Overall, inter- and intraobserver agreement for the NAPH was good. There was, however, a level of disagreement among observers, thus suggesting that clinicians should be cautious when deciding whether to pursue follow-up imaging.

Onyx embolization of a thoracolumbar perimedullary spinal arteriovenous fistula in an infant presenting with subarachnoid and intraventricular hemorrhage

Identifying a source of spontaneous subarachnoid hemorrhage (SAH) or intraventricular hemorrhage (IVH) in patients with negative results on cranial angiographic imaging can be a diagnostic challenge. The authors present the case of a 14-month-old girl who presented with lethargy and spontaneous SAH and IVH, and later became acutely paraplegic. Except for the SAH and IVH, findings on neuroimages of the brain were normal. Magnetic resonance imaging revealed an intramedullary thoracolumbar spinal cord hemorrhage that was found to be associated with arterialized veins intraoperatively. Catheter-based diagnostic angiography identified a spinal perimedullary macroarteriovenous fistula (macro-AVF) that was completely embolized with Onyx, negating the need for further surgical intervention. The authors believe this to be the first reported case of a thoracolumbar perimedullary macro-AVF presenting with SAH and IVH. In addition, descriptions of Onyx embolization of a spinal AVF in the literature are rare, especially in pediatric patients.

Multislice CT angiography in the selection of patients with ruptured intracranial aneurysms suitable for clipping or coiling

Introduction

We sought to establish whether CT angiography (CTA) can be applied to the planning and performance of clipping or coiling in ruptured intracranial aneurysms without recourse to intraarterial digital subtraction angiography (IA-DSA).

Methods

Over the period April 2003 to January 2006 in all patients presenting with a subarachnoid haemorrhage CTA was performed primarily. If CTA demonstrated an aneurysm, coiling or clipping was undertaken. IA-DSA was limited to patients with negative or inconclusive CTA findings. We compared CTA images with findings at surgery or coiling in patients with positive CTA findings and in patients with negative and inconclusive findings in whom IA-DSA had been performed.

Results

In this study, 224 consecutive patients (mean age 52.7 years, 135 women) were included. In 133 patients (59%) CTA demonstrated an aneurysm, and CTA was followed directly by neurosurgical (n = 55) or endovascular treatment (n = 78). In 31 patients (14%) CTA findings were categorized as inconclusive, and in 60 (27%) CTA findings were negative. One patient received surgical treatment on the basis of false-positive CTA findings. In 17 patients in whom CTA findings were inconclusive, IA-DSA provided further diagnostic information required for correct patient selection for any therapy. Five ruptured aneurysms in patients with a nonperimesencephalic SAH were negative on CTA, and four of these were also false-negative on IA-DSA. On a patient basis the positive predictive value, negative predictive value, sensitivity, specificity and accuracy of CTA for symptomatic aneurysms were 99%, 90%, 96%, 98% and 96%, respectively.

Conclusion

CTA should be used as the first diagnostic modality in the selection of patients for surgical or endovascular treatment of ruptured intracranial aneurysms. If CTA renders inconclusive results, IA-DSA should be performed. With negative CTA results the complementary value of IA-DSA is marginal. IA-DSA is not needed in patients with negative CTA and classic perimesencephalic SAH. Repeat IA-DSA or CTA should still be performed in patients with a nonperimesencephalic SAH.

Subarachnoid haemorrhage

Subarachnoid haemorrhage accounts for only 5% of strokes, but occurs at a fairly young age. Sudden headache is the cardinal feature, but patients might not report the mode of onset. CT brain scanning is normal in most patients with sudden headache, but to exclude subarachnoid haemorrhage or other serious disorders, a carefully planned lumbar puncture is also needed. Aneurysms are the cause of subarachnoid haemorrhage in 85% of cases. The case fatality after aneurysmal haemorrhage is 50%; one in eight patients with subarachnoid haemorrhage dies outside hospital. Rebleeding is the most imminent danger; a first aim is therefore occlusion of the aneurysm. Endovascular obliteration by means of platinum spirals (coiling) is the preferred mode of treatment, but some patients require a direct neurosurgical approach (clipping). Another complication is delayed cerebral ischaemia; the risk is reduced with oral nimodipine and probably by maintaining circulatory volume. Hydrocephalus might cause gradual obtundation in the first few hours or days; it can be treated by lumbar puncture or ventricular drainage, dependent on the site of obstruction.

Brain Computed Tomography Angiographic Scans as the Sole Diagnostic Examination for Excluding Aneurysms in Patients with Perimesencephalic Subarachnoid Hemorrhage

OBJECTIVE

In an era in which new computed tomographic scanners approach 100% sensitivity for finding intracranial aneurysms in patients with a perimesencephalic subarachnoid hemorrhage (SAH) pattern, digital subtraction angiography (DSA) is still considered the gold standard. Our purpose was to investigate whether or not computed tomography angiographic (CTA) scanning can be used as the sole diagnostic tool in this setting, and thus replace DSA.

METHODS

Two hundred fifty patients with atraumatic SAH presented to our institute between November 2001 and November 2005. We performed a retrospective search for those patients who had a negative brain CTA scan for aneurysms. Of these, those with a computed tomographic scan showing perimesencephalic SAH at admission were selected, and only those who had DSA performed were included.

RESULTS

We found 30 patients with negative brain CTA scans that matched the perimesencephalic SAH pattern and had DSA performed. The mean time for performing a brain CTA scan was 3.8 +/- 4.4 days, and for DSA 11 +/- 12 days, after the initiation of symptomatology. The interval between CTA and DSA was 5.9 +/- 15 days. There were two patients in whom CTA was considered negative but still suspicious for having an aneurysm; DSA was negative for both.

CONCLUSION

Brain CTA scanning alone is a good and conclusive diagnostic tool to rule out aneurysms in patients presenting with the classic perimesencephalic SAH pattern and thus can replace DSA and its corresponding risks. The latter can be reserved for those patients in whom CTA is doubtful.

Arterial spasm following perimesencephalic nonaneurysmal subarachnoid hemorrhage in a pediatric patient

Perimesencephalic nonaneurysmal hemorrhage is a benign form of subarachnoid hemorrhages. This entity is well recognized as a distinct type of subarachnoid hemorrhage in adults. However, perimesencephalic nonaneurysmal subarachnoid hemorrhage in pediatric patients is not well recognized. Angiographic changes such as vasospasm are uncommon in patients, especially in pediatric patients suffering from this type of hemorrhage. This case study reports a 12-year-old male who suffered from perimesencephalic nonaneurysmal subarachnoid hemorrhage. Cerebral carotid angiography performed on the tenth day of the posthemorrhagic period revealed severe vasospasm affecting the basilar artery. The patient, treated symptomatically, was discharged after improvement. One year later, magnetic resonance angiography revealed completely normal features.

Venous drainage in perimesencephalic hemorrhage

BACKGROUND AND PURPOSE

In perimesencephalic nonaneurysmal hemorrhage (PMH), subarachnoid blood accumulates around the midbrain. Clinical and radiological characteristics suggest a venous origin of PMH. We compared the venous drainage of the midbrain between patients with PMH and aneurysmal subarachnoid hemorrhage (aSAH) by means of computed tomography angiography (CTA).

METHODS

CTAs of 55 PMH patients and 42 aSAH patients with a posterior circulation aneurysm were reviewed. Venous drainage was classified into: (1) normal continuous: the basal vein of Rosenthal is continuous with the deep middle cerebral vein and drains mainly to the vein of Galen (VG); (2) normal discontinuous: drainage anterior to uncal veins and posterior to VG; and (3) primitive variant: drainage to other veins than VG. Additionally, we compared in PMH patients the side of the primitive variant and side of the bleeding.

RESULTS

A primitive variant was present on one or both hemispheres in 53% of PMH patients with PMH (95% CI, 40% to 65%) and in 19% of aSAH patients (95% CI, 10% to 33%). In all 16 PMH patients with a unilateral primitive drainage, blood was seen on the side of the primitive drainage (100%; 95% CI, 81% to 100%); blood was never found mainly on the side with normal drainage.

CONCLUSIONS

Patients with PMH have a primitive venous drainage directly into dural sinuses instead of via the vein of Galen more often than do controls. Moreover, the side of the perimesencephalic hemorrhage relates to the side of the primitive drainage. These results further support a venous origin of PMH.

Untreated subarachnoid hemorrhage: who, why, and when?

OBJECT

When subarachnoid hemorrhage (SAH) is caused by an aneurysm or other vascular anomaly, surgery or endovascular treatment is generally indicated. Nevertheless, some patients with SAH do not receive such therapy. The objective of this study was to characterize the patients who do not receive treatment.

METHODS

The records of all patients with SAH who were admitted to a tertiary care center during a 9-year period were retrospectively reviewed. Untreated patients were classified into one of three groups based on angiographic results. Demographic, clinical, and neuroimaging findings and outcomes were compared between these three groups and between treated and untreated patients. Definitive treatment of SAH was provided in 477 patients and 166 were untreated. Untreated patients were older, had a worse neurological status on presentation, and a higher mortality rate (43.4% compared with 11.7%). Among these, 76 had normal angiographic results and a low mortality rate (6.6%). Fifty-two patients in whom no cerebral angiogram was obtained (mostly because of their neurological condition) had the highest mortality rate (92.3%). Of 38 patients with abnormal angiographic results 50% died, mostly due to rebleeding. Among elderly patients or those with a severe neurological deficit, outcome was significantly better in the ones who were treated.

CONCLUSIONS

A significant proportion of patients who were admitted with SAH did not receive definitive therapy. Major reasons for this included normal results on angiographic studies and poor clinical grade. Untreated patients with normal angiographic results had a good outcome, whereas those in whom angiography was not performed and those with abnormal angiographic results had a high mortality rate from the consequences of the initial hemorrhage in the first instance or rebleeding in the second. Although among elderly patients and those with a poor clinical grade the mortality rate was lower among those who received treatment, a definitive conclusion favoring treatment in these high-risk groups can only be drawn from a prospective randomized study.

Non-Aneurysmal Perimesencephalic Subarachnoid Haemorrhage with Associated Pontine Haemorrhagic Infarction

Non-aneurysmal perimesencephalic subarachnoid saemorrhage is characterized by an accumulation of blood in the perimesencephalic and prepontine cisterns identified on sectional imaging together with persistently negative cerebral angiography. Magnetic resonance imaging usually contributes no further information on the possible cause of the bleed but may occasionally show further features including associated parenchymal infarcts such as the pontine haemorrhagic infarct seen in the case described here.

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.

Quadrigeminal non-aneurysmal subarachnoid hemorrhage--a true variant of perimesencephalic subarachnoid hemorrhage. Case report

Spontaneous non-aneurysmal subarachnoid hemorrhage (SAH) centered in the quadrigeminal cistern has been proposed as a variant of perimesencephalic non-aneurysmal SAH (PNSH). Some authors contest the existence of this entity, claiming it results either from head trauma or an undiscovered P2-P3 aneurysm, and conclude that all PNSH arise in front of the brainstem in a 'pretruncal' location. We report a patient with a quadrigeminal pattern of subarachnoid blood who was investigated with two digital catheter angiograms, including 3-D angiography, plus a high-resolution computed tomography angiogram. No abnormal findings were present and the patient had an excellent outcome. We propose that the more common pretruncal PNSH and less common quadrigeminal PNSH are two types of perimesencephalic SAH with separate, distinct etiologies, both of which have a more benign clinical course than aneurysmal SAH.

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.

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.

Prognostic value of intraventricular blood in perimesencephalic nonaneurysmal subarachnoid hemorrhage

INTRODUCTION

Perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSH) is a distinct type of subarachnoid hemorrhage with a characteristic bleeding pattern, and an excellent clinical outcome. However, the clinical course of patients presenting with a perimesencephalic nonaneurysmal bleeding pattern and intraventricular blood has not yet been investigated.

MATERIALS AND METHODS

In this retrospective study we describe the cisternal blood distribution and the clinical course of 34 PNSH patients with (10 patients) and without (24 patients) intraventricular blood.

RESULTS/DISCUSSION

Patients without intraventricular blood were in good clinical condition on admission; the in-hospital course was uneventful except for acute hydrocephalus, which was detected in two cases and improved spontaneously in both patients. All patients resumed their previous lifestyles. In contrast, two patients with PNSH and intraventricular blood were drowsy and had focal neurologic deficits on admission. Four patients developed an acute hydrocephalus, and two of these patients needed ventricular shunting. There was evidence for delayed cerebral ischemia in one of these patients. Outcome was excellent in eight cases, and one patient was moderately and one patient was severely disabled at dismissal from the hospital. Rebleeding did not occur in all patients, and repeated four-vessel angiography did not reveal the source of bleeding in any of our patients.

CONCLUSION

Our data indicate that the presence of intraventricular blood may be a good indicator for the development of acute hydrocephalus in PNSH. Moreover, our results suggest that PNSH patients with ventricular blood may have a higher complication rate and a poorer outcome compared with PNSH patients without intraventricular blood.

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.

Perimesencephalic hemorrhage and CT angiography: A decision analysis

BACKGROUND AND PURPOSE

The method of choice for detecting or excluding a vertebrobasilar aneurysm still is a matter of debate in patients with a characteristically perimesencephalic pattern of subarachnoid hemorrhage (SAH) on CT. We used decision analysis to compare possible diagnostic strategies in these patients.

METHODS

A decision analytic model was developed to evaluate the effect of 4 different diagnostic strategies following a perimesencephalic pattern of SAH on CT: 1, no further investigation; 2, digital subtraction angiography (DSA) by catheter; 3, CT angiography as initial modality, not followed by DSA if negative; and 4, CT angiography as initial modality, followed by DSA. We used a 4% prevalence of a vertebrobasilar aneurysm given a perimesencephalic pattern of hemorrhage, a 97% sensitivity and specificity of CT angiography, and a 99.5% sensitivity and 100% specificity of DSA. In a prospectively collected series, the complication rate from DSA in patients with a perimesencephalic pattern of hemorrhage was 2.6%. We calculated the expected utility of each of the 4 diagnostic options and used sensitivity analyses to examine the influence of the plausible ranges of the various estimates used.

RESULTS

The expected utilities were 99.09 for CT angiography only, 98.96 for no further investigation, 98.22 for DSA, and 96.34 for CT angiography plus DSA. The results of the sensitivity analysis indicate that over a wide range of assumptions, CT angiography only is the most beneficial option. Only when the complication rate of catheter angiography is <0.2% is DSA the preferred strategy.

CONCLUSIONS

Our decision analysis shows that in patients with a perimesencephalic pattern of hemorrhage on CT, CT angiography only is the best diagnostic strategy. DSA can be omitted in patients with a perimesencephalic pattern of hemorrhage and a negative CT angiogram.

Perimesencephalic hemorrhage. Exclusion of vertebrobasilar aneurysms with CT angiography

BACKGROUND AND PURPOSE

It is important to recognize a perimesencephalic pattern of hemorrhage in patients with subarachnoid hemorrhage (SAH), because in 95% of these patients the cause is nonaneurysmal and the prognosis is excellent. The purpose of this study was to investigate whether CT angiography can accurately exclude vertebrobasilar aneurysms in patients with perimesencephalic patterns of hemorrhage and therefore replace digital subtraction angiography (DSA) in this setting.

METHODS

In 40 patients with posterior fossa SAH as shown on unenhanced CT, 2 radiologists independently evaluated unenhanced CT for distinguishing between perimesencephalic and nonperimesencephalic pattern of hemorrhage and assessed CT angiography for detection of aneurysms. All patients subsequently underwent DSA or autopsy.

RESULTS

Observers agreed in 38 of 40 patients (95%) in differentiating perimesencephalic and nonperimesencephalic patterns of hemorrhage on unenhanced CT. On the CT angiograms, both observers detected a vertebrobasilar aneurysm in 16 patients and no aneurysm in 24 patients. These findings were confirmed by DSA or autopsy. No patients with a perimesencephalic pattern of hemorrhage were found to have an aneurysm on either CT angiography or DSA.

CONCLUSIONS

Good recognition of a perimesencephalic pattern of hemorrhage is possible on unenhanced CT, and CT angiography accurately excludes and detects vertebrobasilar aneurysms. DSA can be withheld in patients with a perimesencephalic pattern of hemorrhage and negative CT angiography.

Subarachnoid hemorrhage diagnosis: lumbar puncture is still needed when the computed tomography scan is normal

OBJECTIVES

To determine the sensitivity of third-generation CT scanners for diagnosed nontraumatic subarachnoid hemorrhage (SAH) and to assess the impact of symptom duration on sensitivity.

METHODS

A retrospective chart review was performed in a university-affiliated tertiary care hospital with an annual ED volume of > 100,000 patients. The target population was all patients who presented to the ED from January 1991 to September 1994 with symptoms suggestive of SAH and who had a final diagnosis of nontraumatic SAH based on either a positive CT scan or positive spinal fluid analysis. Patients referred from outside facilities were included if they had a CT done at the study site. All CT scans were done using third-generation scanners. Official CT scan reports were used to categorize scans as positive or negative.

RESULTS

There were 140 patients identified with SAH, with a mean age of 56 years (range 10-88). The sensitivity of CT in the diagnosis of nontraumatic SAH when performed at or before 12 hours of symptom duration was 100% (80/80), and 81.7% (49/60) after 12 hours of symptom duration (95% CI 95-100% and 69.5-90.4%, respectively; p < 0.0001). Eleven of the 140 patients had a negative CT and positive spinal fluid analysis, yielding an overall sensitivity of 92.1% (129/140).

CONCLUSION

The sensitivity of third-generation CT scans for SAH decreases with time from the onset of symptoms. In this sample population, CT was able to detect all patients scanned < or = 12 hours after symptom onset. Although the study demonstrated good sensitivity of CT scan reports for SAH when the scan was performed after < or = 12 hours of symptom onset, additional real-time experience is needed to better define the potential risk of a missed SAH should this population not receive the customary lumbar puncture examination in the setting of a negative CT scan.

Perimesencephalic nonaneurysmal subarachnoid hemorrhage: review of the literature

OBJECTIVE

A critical review of the literature on the incidence, presentation, diagnosis, and prognosis of perimesencephalic nonaneurysmal subarachnoid hemorrhage.

METHODS

Review of the relevant literature.

CONCLUSION

The importance of early computed tomography (< 3 d), anatomy of the perimesencephalic and neighboring cisterns, and adequate four-vessel angiography are discussed. Treatment strategies, including the avoidance of repeated angiographic studies and surgical exploration, are presented.

Aneurysmal and microaneurysmal "angiogram-negative" subarachnoid hemorrhage

The source of bleeding remains obscure in most cases of subarachnoid hemorrhage (SAH) with a negative angiogram. From January 1, 1989, to July 1, 1993, 40 patients were admitted to the Massachusetts General Hospital with angiogram-negative SAH; 9 of these patients underwent surgical exploration. In seven of these explorations, an arterial source of the hemorrhage was discovered. These arterial sources included three anterior communicating artery complex lesions, two middle cerebral artery lesions, one internal carotid artery aneurysm arising at the origin of the posterior communicating artery, and one vertebral/posterior inferior cerebellar artery aneurysm. Three of these seven lesions had small aneurysmal sacs, but the other four were microaneurysms too small to accept a surgical clip. No source of hemorrhage could be found during surgery on one patient with a perimesencephalic pattern of blood. Two of the four patients with a microaneurysmal source of hemorrhage had two episodes of SAH. We propose that microaneurysms are the source of a significant percentage of nonperimesencephalic angiogram-negative SAH and suggest that these lesions may represent a forme fruste of saccular aneurysms. These findings lead us to propose a protocol for the management of angiogram-negative SAH based on the distribution of blood as seen on the patient's first computed tomogram.

Acute lacunar stroke in association with angiogram-negative subarachnoid hemorrhage. Mechanistic implications of two cases

BACKGROUND AND PURPOSE

Although there is much speculation regarding the source of bleeding in patients with subarachnoid hemorrhage when no angiographic abnormality is found, little direct evidence has been obtained to document a cause. We report two cases of stroke in the distribution of a perforating or lenticulostriate artery occurring at the time of angiogram-negative subarachnoid hemorrhage.

CASE DESCRIPTIONS

A 68- and a 60-year-old man each presented with acute onset of headache and meningismus. Computed tomography (CT) revealed subarachnoid hemorrhage in a perimesencephalic pattern and in the left sylvian fissure, respectively. In both instances, immediate CT revealed evidence of an early infarction in the distribution of a perforating artery originating at the site of the subarachnoid blood. Both of these strokes were demonstrated to be acute by evolution on serial imaging studies. No source for the subarachnoid blood could be found in either patient in cerebral angiograms repeated at 2 weeks.

CONCLUSIONS

These observations suggest that in some cases of angiogram-negative subarachnoid hemorrhage the source of blood may be a small artery that is obliterated at the time of hemorrhage. This observation provides an explanation for the low rate of rehemorrhage among patients with angiogram-negative subarachnoid hemorrhage.

Perimesencephalic subarachnoid hemorrhage. Additional perspectives from four cases

BACKGROUND

Nonaneurysmal perimesencephalic hemorrhage, a distinct form of subarachnoid hemorrhage, is a recently described variant of intracranial hemorrhage. We describe two patients who presented with unusual features of this type of subarachnoid hemorrhage and also two patients who had a perimesencephalic pattern of hemorrhage due to a ruptured posterior circulation aneurysm.

CASE DESCRIPTIONS

The first patient, a 41-year-old woman with perimesencephalic hemorrhage, underwent an exploratory craniotomy because angiography had suggested an anomaly of the basilar tip. No source of hemorrhage could be identified at the time of surgery. The second patient was a 3-year-old boy who presented with opisthotonos and who was found to have a perimesencephalic hemorrhage. Angiography revealed no source for the hemorrhage. The third patient, a 54-year-old man, had a perimesencephalic pattern of subarachnoid hemorrhage from a vertebrobasilar junction aneurysm associated with a fenestration that was missed on the initial angiographic study. The fourth patient, a 43-year-old man, suffered a perimesencephalic pattern of subarachnoid hemorrhage from a small posterior cerebral artery aneurysm, which had not been recognized on two angiograms.

CONCLUSIONS

These patients elaborate on the clinical spectrum of subarachnoid hemorrhage with a perimesencephalic pattern. First, a negative exploratory craniotomy suggests that the source of nonaneurysmal perimesencephalic hemorrhage may not be arterial. Second, nonaneurysmal perimesencephalic hemorrhage may also occur in children. Finally, the index of suspicion for a posterior circulation aneurysm should remain high in patients who present with a perimesencephalic pattern of subarachnoid hemorrhage, and these aneurysms may rise from unusual locations.