Perimesencephalic Subarachnoid Hemorrhage Pattern Research Articles

Aneurysmal Versus “Benign” Perimesencephalic Subarachnoid Hemorrhage

Background The rate of underlying ruptured aneurysms, complications, and their relevance to outcomes in “benign” perimesencephalic subarachnoid hemorrhage are not well known and underreported. Methods Retrospective analysis of patients with perimesencephalic subarachnoid hemorrhage from a large tertiary care center (2007–2022). Results Eighty‐one patients were included with mean age of 55.5 ± 10.3 years. An underlying ruptured aneurysm was diagnosed in 5 patients (6.2%); 3 (60%) had negative computed tomography angiography and they were detected only in digital subtraction angiography (2 on initial digital subtraction angiography and 1 on follow‐up digital subtraction angiography). The most common complication was vasospasm in 25/81 patients (31%), and the majority 21/25 (84%) were asymptomatic. Symptomatic vasospasm occurred at a significantly higher rate among patients with underlying aneurysm (40% versus 2.6%; P = 0.01). Hydrocephalus occurred in 10% of patients, all within 1 day, but at a higher rate in the aneurysmal group (40% versus 8%; P = 0.07). A total of 88% of patients had modified Rankin scale score 0–2 at discharge, but at a significantly higher rate in nonaneurysmal patients (91% versus 40%; P = 0.01). An underlying aneurysm, hydrocephalus, and symptomatic vasospasm were associated with poor functional status (odds ratio [OR] = 14.7 [2.1–104]; P = 0.007, OR = 22.6 [4.2–123.5]; P <0.001, OR = 8.6 [1.06–69.88]; P = 0.04), respectively. Conclusion “Benign” perimesencephalic subarachnoid hemorrhage pattern was associated with a ruptured aneurysm in 6.2% of patients, and 3.7% were detected only on cerebral angiogram. Underlying aneurysm, symptomatic vasospasm, and hydrocephalus were associated with lower rates of good clinical outcome. All hydrocephalus cases were symptomatic and occurred very early. Asymptomatic vasospasm alone was not associated with poor outcomes. Our findings suggest that patients with nonaneurysmal perimesencephalic subarachnoid hemorrhage without hydrocephalus can safely be managed with less strict monitoring and a shorter hospital stay.

Persistent primitive hypoglossal artery presenting with perimesencephalic nonaneurysmal subarachnoid hemorrhage: A case report and review of literature

BackgroundPersistent primitive hypoglossal artery (PPHA) is a rare remnant of the congenital carotid-basilar artery anastomosis, sometimes associated with subarachnoid hemorrhage (SAH), and aneurysms are the more common cause. However, the association of PPHA with perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSAH) is extremely rare. This report is the first to describe the occurrence of PNSAH concerning PPHA. Case descriptionA 53-year-old man suffered from subarachnoid hemorrhage with a sudden severe headache. An emergency brain computed tomography (CT) disclosed a perimesencephalic pattern of SAH. CT angiography (CTA) revealed a right PPHA entering the posterior fossa through the right enlarged hypoglossal canal. No source of the hemorrhage was identified in the imaging examinations, even with the performance of a 4-vessel angiography. ConclusionWe present a case of PPHA associated with PNSAH and review the literature. The main cause for the PPHA related to SAH is an aneurysm. The four vessels angiography helped rule out an aneurysm that is associated with a poorer prognosis and requires immediate active management. It is, therefore, essential for physicians to be aware of the increased incidence of aneurysms in PPHA to make the correct diagnosis.

Abstract 3456: Incidence of Vasospasm and Outcomes in Angiography-negative Perimesencephalic Subarachnoid Hemorrhage with and without Ventricular Extension

Background: Angiography negative perimesencephalic subarachnoid hemorrhage (SAH) is considered a relatively benign entity compared to aneurysmal SAH. However, some patients with angiography negative perimesencephalic subarachnoid hemorrhage with extension of hemorrhage beyond the perimesencephalic area are at increased risk for vasospasm. Here we present a series of 21 patients with angiography negative perimesencephalic pattern of SAH both with and without ventricular extension and describe their incidence of vasospasm and clinical outcomes. Methods: Retrospective chart review was performed among patients who underwent invasive angiography from 8/2007-6/2010. Inclusion criteria were presenting clinical symptoms typical of SAH, computed tomography (CT) evidence of perimesencephalic SAH with or without ventricular extension, no recent trauma or stroke, and cerebral angiography negative for aneurysm or arteriovenous malformation. 21 patients, 8 men and 13 women, with a mean age of 55.1 years met these criteria. The presenting CTs were examined and a modified Fisher Grade assigned. The patients’ clinical course was reviewed for incidence and treatment of vasospasm. The patients’ discharge summaries were evaluated and each patient given a modified Rankin Scale score. Results: The modified Fisher Scale score derived from the presenting CT was 1 for 29% (n=6), 2 for 5% (n=1), 3 for 19% (n=4), and 4 for 47% (n=10) of the patients. Amongst the 52% (n=11) of patients with intraventricular hemorrhage as defined by a modified Fisher Scale score of 2 or 4, 24% (n=5) developed angiographical evidence of vasospasm. 10% (n=2) of the patients required intra-arterial verapamil. 90% (n=9) of patients without intraventricular extension had good outcomes at discharge as defined by modified Rankin Scale score less than or equal to 2, while only 36% (n=4) of patients with angiography negative SAH with intraventricular extension had good outcomes. Conclusions: Although angiography negative perimesencephalic SAH is considered to have less associated morbidity and mortality than aneurysmal perimesencephalic SAH, patients with extension of hemorrhage into the ventricles are at increased risk for vasospasm and poor functional outcomes.

Endoscopic third ventriculostomy for hydrocephalus after perimesencephalic subarachnoid hemorrhage: initial experience in three patients

To review the outcome after endoscopic third ventriculostomy (ETV) for symptomatic, persistent hydrocephalus in three patients with perimesencephalic angiographically negative subarachnoid hemorrhage (PNH) who were dependent on an external ventricular drain (EVD). All patients initially presented with severe headache, nuchal rigidity, confusion and lethargy (Hunt-Hess Grade II or III), and persistent, EVD-dependent hydrocephalus. Cranial CT images in each revealed acute hydrocephalus and perimesencephalic hemorrhage pattern with a heavy clot burden (Fisher grade 3). A 3D-CT angiogram on admission and two four-vessel cerebral angiograms failed to demonstrate a bleeding source. All three patients failed trial EVD clamping, with clinical deterioration and elevated intracranial pressure (ICP). ETV was performed with a 0-degree endoscope in a 4.6-mm irrigating sheath using an endoscopic-coring/"cookie-cut" technique. An EVD was left in place for postoperative ICP monitoring but was clamped. ETV was accomplished in all patients. In one case, a tiny basilar tip aneurysm was seen during the endoscopic procedure. Intraoperatively, the prepontine cistern revealed dense, degraded blood products. Postprocedure ICP measurements were reduced to normal range. Clinical improvement, normal ICP readings, and/or radiographic evidence of resolution of hydrocephalus allowed uneventful removal of the EVD within 36-48 h post-ETV in all patients. All remained headache-free, with a normal neurological examination, during a follow-up period of 10, 11, and 12months, respectively. To our knowledge, this is the first report of ETV for PNH with hydrocephalus and the first report of a basilar tip microaneurysm seen intraoperatively during ETV. ETV is a viable treatment option for refractory hydrocephalus secondary to a perimesencephalic pattern of subarachnoid hemorrhage (SAH). Its early application can avoid placement of a ventriculoperitoneal shunt, curtail the extended use of an EVD, and reduce the associated infection risks. Despite thorough angiographic investigation for an aneurysmal cause of SAH, a "microaneurysm" of the basilar artery was found at ETV. No complication or rebleeding was encountered.

PERIMESENCEPHALIC NONANEURYSMAL SUBARACHNOID HEMORRHAGE CAUSED BY JUGULAR VENOUS OCCLUSION

The cause of perimesencephalic nonaneurysmal subarachnoid hemorrhage remains unknown. We describe a patient in whom jugular venous occlusion preceded the occurrence of perimesencephalic nonaneurysmal subarachnoid hemorrhage. This finding supports the theory that the source of the hemorrhage is venous in origin. A 25-year-old man presented with sudden onset of headache after his head was held in a headlock during a playful fight 48 hours before the ictus. His computed tomographic (CT) scan on admission demonstrated a perimesencephalic pattern of subarachnoid hemorrhage. CT angiography excluded the presence of an underlying aneurysm or vascular malformation but showed bilateral jugular venous obstruction with hematoma surrounding the right internal jugular vein. Magnetic resonance imaging and a 4-vessel cerebral angiogram confirmed the CT angiographic findings. The patient was observed as an inpatient and had no complication of his hemorrhage. Follow-up at 5 months with CT angiography showed resolution of his neck hematoma and reopening of his internal jugular veins. The presence of acute jugular venous occlusion as a cause of perimesencephalic nonaneurysmal subarachnoid hemorrhage supports a venous origin of hemorrhage.

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

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. 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. 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. 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.

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

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. 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. 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.

Intracranial Aneurysms

This article reviews the current knowledge of the pathogenesis, clinical features, diagnostic evaluation, and treatment of intracranial aneurysms. The vast majority are acquired lesions, likely as a result of hemodynamic stress on the relatively unsupported bifurcations of the intracranial arteries. Cigarette smoking is an emerging important risk factor for their development. The natural history of unruptured aneurysms is controversial and may be subject to revision. A benign perimesencephalic pattern of subarachnoid hemorrhage has been recognized that usually is not due to a ruptured aneurysm. Current treatment includes surgical clipping and endovascular treatment with Guglielmi detachable coils, which produces comparable results in some instances. Epidemiologic studies suggest that the outcome of patients with aneurysmal subarachnoid hemorrhage remains poor, with a 30-day death rate of 45%, although the outcome of patients who reach the hospital alive may have improved in recent years.

Perimesencephalic hemorrhage and CT angiography: A decision analysis.

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. 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. 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. 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.

Ruptured vertebrobasilar aneurysms: frequency of the nonaneurysmal perimesencephalic pattern of hemorrhage on CT scans.

To determine the frequency of the computed tomographic (CT) pattern of nonaneurysmal perimesencephalic subarachnoid hemorrhage in the setting of ruptured posterior fossa aneurysms. Four neuroradiologists independently and retrospectively reviewed cranial CT scans of 169 patients with ruptured vertebrobasilar aneurysms (44 cases of posteroinferior cerebellar artery aneurysm, 20 cases of superior cerebellar artery aneurysm, and 105 cases of basilar-tip aneurysm). The mean frequency of nonaneurysmal perimesencephalic pattern of subarachnoid hemorrhage in ruptured vertebrobasilar aneurysms was 7.1% (48 of 676 readings) among the four readers. The mean frequency of aneurysms with the pattern of hemorrhage for each location was as follows: basilar tip, 9.8% (41 of 420 readings); superior cerebellar artery, 5.0% (four of 80 readings); and posteroinferior cerebellar artery, 0%. In 75% (six of eight) of the cases in which the CT pattern of hemorrhage was deemed compatible by all readers with nonaneurysmal hemorrhage, the clinical presentation was mild. Because ruptured posterior fossa aneurysms manifest with the nonaneurysmal pattern of hemorrhage in approximately 10% of cases, a high degree of suspicion should be maintained even if the pattern of subarachnoid hemorrhage suggests a nonaneurysmal origin and clinical symptoms are mild.

Perimesencephalic subarachnoid hemorrhage. Additional perspectives from four cases.

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. 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. 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.