Chiari malformation presenting with subarachnoid hemorrhage: a case report

Chiari malformations (CM) are often diagnosed in childhood and younger adults, with an incidence of only 0.77% in adult populations. Patients with CM may develop syringomyelia and increased intracranial pressure (ICP) due to cerebrospinal fluid (CSF) obstruction and altered fluid dynamics at the cervicomedullary junction. We describe the case of a 65-year-old female presenting with an angionegative subarachnoid hemorrhage (SAH) with concomitant new diagnosis of CM type I with syringomyelia. After ruling out any aneurysm or vascular malformations, she underwent a suboccipital craniectomy for a Chiari decompression with a C1 laminectomy. There were no complications with the surgery and her symptoms improved. This case report highlights the unusual presentation of a CM.

Contribution of Deep Cerebral Venous Anomaly to the Emergence of Nonaneurysmal Subarachnoid Hemorrhage as Opposed to Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

The exact reason of nonaneurysmal subarachnoid hemorrhage (SAH) is an enigma. The aim of this study is to identify if type III deep cerebral venous drainage is exclusively prevalent in patients with nonaneurysmal SAH and to enumerate the predictors of poorer outcome in these patients.

METHODS

All patients of age >18 years, presented at our centre with spontaneous SAH on noncontrast computed tomography head and were divided into 2 groups, aneurysmal and nonaneurysmal SAH after 4-vessel DSA. Based on the deep venous drainage pattern on both sides, basal venous drainage was found and classified into 3 types: type I, type II, and type III. The 3 groups were pitted against one another. Regression analysis were performed to predict the occurrence of nonaneurysmal-SAH with different types of basal vein.

RESULTS

There were 100 nonaneurysmal SAH cases and 103 aneurysmal SAH cases. The mean age of presentation was 47.8 ± 13.55 years with slight male predominance (52%). The patients with type III venous drainage have 2 times more risk of developing nonaneurysmal SAH (95% confidence interval = 1.21-4.31) as compared to those with aneurysmal SAH. On multivariate analysis, type III basal venous drainage, worse Hunt and Hess grade at presentation, extensive bleeding were predictors of an adverse outcome.

CONCLUSIONS

The presence of type III venous distribution is associated with a 2-fold increase in the probability of having nonaneurysmal SAH, as well as a 3-fold increase in the risk of developing poorer neurological sequelae.

Clinical Outcomes of Diffuse Angiogram-Negative Subarachnoid Hemorrhage Versus Aneurysmal Subarachnoid Hemorrhage: A Propensity Score-Matched Analysis

BACKGROUND

The outcome of diffuse angiogram-negative subarachnoid hemorrhage (dan-SAH) compared with aneurysmal SAH (aSAH) remains unclear. This study aimed to compare outcomes using propensity score matching.

METHODS AND RESULTS

Sixty-five patients with dan-SAH and 857 patients with aSAH admitted between January 2018 and December 2022 were retrospectively reviewed. Propensity score matching resulted in matching 65 patients with dan-SAH to 260 patients with aSAH, and clinical outcomes were compared between the groups. Compared with patients with dan-SAH, patients with aSAH were more likely to experience rehemorrhage (8.8% versus 0%, P=0.027), death (11.2% versus 1.5%; odds ratios [OR] 8.04 [95% CI, 1.07-60.12]; P=0.042), or delayed cerebral ischemia (12.3% versus 3.1%; OR, 4.42 [95% CI, 1.03-18.95]; P=0.045). Multivariate analysis revealed that Hunt-Hess grade 4 to 5 (OR, 3.13 [95% CI, 2.11-4.64]; P<0.001), presence of intraventricular hemorrhage (OR, 3.58 [95% CI, 1.72-7.46]; P=0.001), and smoking (OR, 2.44 [95% CI, 1.12-5.28]; P=0.024) were independently associated with the incidence of unfavorable outcomes (modified Rankin scale score >2 at 3 months), whereas dan-SAH was not (OR, 0.66 [95% CI, 0.25-1.73]; P=0.40).

CONCLUSIONS

Compared with patients with dan-SAH, patients with aSAH had higher rehemorrhage rates and in-hospital mortality, as well as a higher incidence of delayed cerebral ischemia. Unfavorable outcomes were associated with admission Hunt-Hess grade, the presence of intravenetricular hemorrhage, and smoking history, but there was no relation with the  pathogenesis of the hemorrhage (dan-SAH versus aSAH).

The accuracy of non-contrast brain CT scan in predicting the presence of a vascular etiology in patients with primary intracranial hemorrhage

Spontaneous intraparenchymal cerebral hemorrhages (SIPH) account for 10-15% of acute strokes. Sorting these patients according to the risk of harboring an underlying vascular etiology may help selecting the patients who would mostly benefit from Multidetector CT Angiography (MDCTA). The aim of this study was to evaluate the accuracy of Non-Contrast brain CT (NCCT) in predicting possible vascular etiologies in patients with SIPH. In this retrospective study, we evaluated the NCCT of 334 patients who presented with SIPH from March 2017 to March 2021 and we looked for vascular etiologies in the CTA which was performed for these patients. We used NCCT criteria to predict the presence of any vascular etiologies in SIPH patients and proposed a scoring system based on these criteria which might predict the risk of vascular ICH (VICH score). Out of 334 evaluated patients, 9.3% had an underlying vascular etiology. Independent predictors of the vascular etiology included: age < 46 years, no history of hypertension and coagulation disorders, lobar hemorrhages, and presence of significant perilesional edema. We used these criteria and NCCT classification to create a practical scoring system to predict the risk of vascular ICH (VICH). In our study, VICH score ≥ 4 had 51.6% sensitivity and 96.4% specificity for predicting a positive MDCTA as the maximum optimal cut-off point. The VICH score seemed to be successful in predicting vascular etiologies in this retrospective cohort of 334 patients. This scoring system can be used to select patients if there are limited resources to perform CT angiography.

A New Insight in Nonaneurysmal Subarachnoid Hemorrhage: the Potential Role of the Internal Jugular Veins

BACKGROUND

 Causes of the nonaneurysmal subarachnoid hemorrhage (na-SAH) are still debated. Many studies confirmed the possible involvement of the intracranial venous system, in particular variants of the basal vein of Rosenthal.

STUDY OBJECT

 The aim of this study is to investigate the role of extracranial venous system, in particular the jugular drainage, in the na-SAH pathophysiology.

MATERIALS AND METHODS

 This is a multicenter retrospective study including patients suffering from na-SAH who were radiologically screened to exclude vascular malformations. The course of the internal jugular veins was evaluated to reveal any stenosis (caliber reduction >80%). Particular attention was paid at the passage between the styloid process and the arch of C1 to detect possible compression. As a control group, we enrolled patients who underwent CT angiograms and/or cerebral DSAs in the past 2 years.

RESULTS

 We included 194 patients. The na-SAH group consisted of 94 patients, whereas the control group consisted of 100 patients. Fifty patients of the control group underwent a CT angiography for an ischemic cerebrovascular disease or trauma and 50 patients for an SAH due to a ruptured aneurysm. A significant jugular stenosis was found in 49 (52.1%) patients in the na-SAH group and in 18 (18%) patients in the control group. At univariate and multivariate analysis, the difference was statistically significant (p < 0.0001).

CONCLUSIONS

 This is the first study investigating the correlation between jugular stenosis and the occurrence of na-SAH. The impaired venous outflow due to reduced venous caliber could result in an engorgement of the upstream intracranial veins with transient hypertensive phases facilitating ruptures. Further larger prospective studies are necessary to confirm these data.

Dural Venous Sinus Variations in Idiopathic Subarachnoid Hemorrhage: A New Indicator of the Venous Origin with Diagnostic Usefulness?

OBJECTIVE

Venous hypertension associated with a primitive basal vein of Rosenthal (BVR) has been noted as the most likely cause of idiopathic subarachnoid hemorrhage (iSAH). Other types of venous drainage variations have been scarcely studied but may further explain the cases not associated with a BVR anomaly. Our aim was to investigate if dural venous sinus (DVS) anomalies are related with iSAH.

METHODS

A total of 76 patients diagnosed with iSAH were identified from a prospectively maintained database and their angiographic findings compared with 76 patients diagnosed with aneurysmal subarachnoid hemorrhage.

RESULTS

On top of the BVR variations, our data showed a higher prevalence of transverse sinus hypoplasia (47.4% vs. 28.9%; P = 0.019), superior petrosal sinus hypoplasia (32.9% vs. 13.2%; P = 0.003), and clival plexus hyperplasia (65.8% vs. 43.4%; P = 0.005) in patients with iSAH. Analyzing by total number of angiograms, the iSAH group showed also a higher prevalence of inferior petrosal sinus hyperplasia (36.2% vs. 25%; P = 0.003). Of the patients with iSAH without a primitive BVR, 84% harbored ≥1 perimesencephalic DVS variation and the overall number of venous drainage variations was significantly higher in patients with iSAH.

CONCLUSIONS

In addition to the well-documented BVR anomalies, there seems to be a significant relationship of other DVS variations in patients with iSAH. Transverse sinus hypoplasia, superior petrosal sinus hypoplasia, inferior petrosal sinus hyperplasia, and clival plexus hyperplasia were significantly more frequent in patients with iSAH. The presence of ≥3 of those variations would increase the suspicion of a nonaneurysmatic subarachnoid hemorrhage and could help avoid a second angiogram.

Deep venous drainage variant rate and degree may be higher in patients with perimesencephalic than in non-perimesencephalic angiogram-negative subarachnoid hemorrhage

OBJECTIVES

The basal vein of Rosenthal (BVR) variant is a potential origin of bleeding in angiogram-negative subarachnoid hemorrhage (AN-SAH). We compared the rate and degree of BVR variants in patients with perimesencephalic AN-SAH (PAN-SAH) and non-perimesencephalic AN-SAH (NPAN-SAH).

METHODS

We retrospectively reviewed the records of AN-SAH patients admitted to our hospital between 2013 and 2018. The associations between variables (baseline characteristics, clinical and radiological data, and outcome) with bleeding patterns and degree of BVR variants were analyzed. Additionally, potential predictors of positive findings on repeated digital-subtracted angiogram (DSA), rebleeding, delayed cerebral infarction (DCI), and poor outcome were further studied.

RESULTS

A total of 273 patients with AN-SAH were included. The incidence rate and degree of BVR variants were significantly higher in PAN-SAH patients compared with those in NPAN-SAH patients (p < 0.001). Patients with normal bilateral BVRs are more likely to have a severe prognosis and diffused blood distribution (p < 0.05). We found an increased rate of positive findings on repeated DSA, DCI, rebleeding, and poor outcome at 3 months and 1 year after discharge (all p < 0.05) in patients with bilateral normal BVRs. Bilateral normal BVRs were considered a risk factor (predictor) of positive findings on repeated DSA, rebleeding, and poor outcome (all p < 0.05).

CONCLUSIONS

PAN-SAH patients have a higher rate and degree of BVR variants compared with patients with NPAN-SAH. Those AN-SAH patients with bilateral normal BVRs are more likely to be of arterial origin and are at risk of suffering from rebleeding and a poor outcome.

KEY POINTS

• Patients with PAN-SAH have a higher rate and degree of BVR variants compared with patients with NPAN-SAH, which suggested that AN-SAH patients with normal BVRs are more likely to originate from arterial bleeding. • AN-SAH patients with normal BVRs are more likely to have positive findings on repeated DSA examinations, as well as an increased incidence of rebleeding and poor outcome, which may assist and guide neurologists in selecting treatment.

Neural Vascular Mechanism for the Cerebral Blood Flow Autoregulation after Hemorrhagic Stroke

During the initial stages of hemorrhagic stroke, including intracerebral hemorrhage and subarachnoid hemorrhage, the reflex mechanisms are activated to protect cerebral perfusion, but secondary dysfunction of cerebral flow autoregulation will eventually reduce global cerebral blood flow and the delivery of metabolic substrates, leading to generalized cerebral ischemia, hypoxia, and ultimately, neuronal cell death. Cerebral blood flow is controlled by various regulatory mechanisms, including prevailing arterial pressure, intracranial pressure, arterial blood gases, neural activity, and metabolic demand. Evoked by the concept of vascular neural network, the unveiled neural vascular mechanism gains more and more attentions. Astrocyte, neuron, pericyte, endothelium, and so forth are formed as a communicate network to regulate with each other as well as the cerebral blood flow. However, the signaling molecules responsible for this communication between these new players and blood vessels are yet to be definitively confirmed. Recent evidence suggested the pivotal role of transcriptional mechanism, including but not limited to miRNA, lncRNA, exosome, and so forth, for the cerebral blood flow autoregulation. In the present review, we sought to summarize the hemodynamic changes and underline neural vascular mechanism for cerebral blood flow autoregulation in stroke-prone state and after hemorrhagic stroke and hopefully provide more systematic and innovative research interests for the pathophysiology and therapeutic strategies of hemorrhagic stroke.

Management of Spontaneous Subarachnoid Hemorrhage Patients with Negative Initial Digital Subtraction Angiogram Findings: Conservative or Aggressive?

Background. The ideal management of SAH patients with negative initial DSA findings remains unresolved. Objective. (i) To present risk factors, clinical courses, and outcomes in different types of SAH patients with negative DSA findings; (ii) to explore the differences of basal vein between aSAH patients and NASAH patients; and (iii) to evaluate the value of repeated DSA for these patients. Methods. All SAH patients with negative initial DSA findings between 2013 and 2015 in our hospital were enrolled and were further categorized as perimesencephalic SAH (PMN-SAH) or nonperimesencephalic SAH (nPMN-SAH). Risk factors, clinical courses, outcomes, and the basal vein drainage patterns were compared. Results. A total of 137 patients were enrolled in the present study. The PMN-SAH group had better GOS and mRS values at 1-year follow-up. Moreover, the nPMN-SAH group had a higher rate of complications. The basal vein drainage pattern showed significant difference when comparing each of the NASAH subtypes with aSAH groups. There was a significant higher rate of a responsible aneurysm in nPMN-SAH group upon repeated DSA. Conclusions. SAH patients with negative initial DSA findings had benign clinical courses and outcomes. Repeated DSA studies are strongly advised for patients with the nPMN-SAH pattern.

Relationship between venous drainage subtypes and sub-arachnoid hemorrhage subtypes: a meta-analysis

BACKGROUND

To investigate whether associations exist between venous drainage subtypes (types I, II, and III) and the risk of subarachnoid hemorrhage subtypes.

METHODS

Published case-control and case series from 2010 to 2014 which met all the inclusion criteria for the meta-analysis were selected and subjected to rigorous statistical analysis.

RESULTS

A total of 11 studies with an overall patient population (case and controls) of 891 were involved in the study. Types I and II venous drainage had odds against peri-mesencephalic subarachnoid hemorrhage. The odds were in favor of type III venous drainage and peri-mesencephalic sub-arachnoid hemorrhage and idiopathic sub-arachnoid hemorrhage (ISAH).

CONCLUSIONS

Type I deep venous drainage may not be associated with the risks of peri-mesencephalic subarachnoid hemorrhage and ISAH, however, types II and III may be associated with high risk of peri-mesencephalic subarachnoid hemorrhage and ISAH, respectively.

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.

Should Patients Be Counseled About Possible Recurrence of Perimesencephalic Subarachnoid Hemorrhage?

BACKGROUND

Isolated perimesencephalic subarachnoid hemorrhage (pSAH) is a distinct subtype of subarachnoid hemorrhage (SAH) seen in 5% of patients with SAH, with a relatively benign natural course and good outcome compared with diffuse, aneurysmal SAH. Traditionally, the prognosis of pSAH is believed to be excellent compared with aneurysmal SAH, with no risk of recurrent hemorrhage after long-term follow-up. We describe a case of pSAH in which the patient had a recurrent perimesencephalic bleed 8 years after the initial episode. There are 5 previous reports of recurrent pSAH in existing literature.

CASE REPORT

A patient in sixth decade of life with no history of trauma presented in 2006 with acute-onset, severe headache, and "off-balance" gait. The patient was diagnosed with pSAH on the basis of computed tomography angiography and digital subtraction angiography. The patient was discharged, and follow-up computed tomography angiography over the next 2 years revealed no underlying vascular anomaly. The patient presented in 2014 with sudden onset of headache, similar to the previous episode with no new neurologic signs. Patient had repeated imaging over the succeeding 2 years, which were all negative for new blood or source of subarachnoid bleed.

REVIEW AND DISCUSSION

There are only a couple of case reports of recurrent pSAH, some of which were defined questionably. We review the reported cases and discuss the imaging results and outcome. Considering the rarity, low risks of complications, as well as the good outcome even after recurrence, we do not recommend routinely counseling patients about possibility of recurrence of pSAH.

Angiographic assessment of variants of basal vein of Rosenthal in idiopathic subarachnoid hemorrhage

Previous studies have reported the possible contribution of a primitive variant of the basal vein of Rosenthal (BVR) in the cause of idiopathic subarachnoid hemorrhage (ISAH). The purpose of this study was to assess the drainage patterns of the BVR among ISAH patients. The venous phase at cerebral angiography was retrospectively analyzed in 19 patients with ISAH and then compared with patients with unruptured aneurysms as controls. A relationship was found between ISAH and the presence of a primitive variant. However, the venous configuration effect on bleeding is still unknown.

Familial perimesencephalic subarachnoid hemorrhage: two case reports

Introduction

Non-aneurysmal spontaneous subarachnoid hemorrhage is characterized by an accumulation of a limited amount of subarachnoid hemorrhage, predominantly around the midbrain, and a lack of blood in the brain parenchyma or ventricular system. It represents 5% of all spontaneous subarachnoid hemorrhage cases. In spite of extensive investigation, understanding of the mechanisms leading to perimesencephalic non-aneurysmal subarachnoid hemorrhage remains incompletely defined. A growing body of evidence has supported a familial predisposition for non-aneurysmal spontaneous subarachnoid hemorrhage.

Case presentation

A 39-year-old Caucasian man presented with sudden onset headache associated with diplopia. His computed tomography scan revealed perimesencephalic subarachnoid hemorrhage. A cerebral angiogram showed no apparent source of bleeding. He was treated conservatively and discharged after 1 week without any neurological deficits. The older brother of the first case, a 44-year-old Caucasian man, presented 1.5 years later with acute onset of headache and his computed tomography scan also showed perimesencephalic non-aneurysmal subarachnoid hemorrhage. He was discharged home with normal neurological examination 1 week later. Follow-up angiograms did not reveal any source of bleeding in either patient.

Conclusions

We report the cases of two siblings with perimesencephalic non-aneurysmal subarachnoid hemorrhage, which may further suggest a familial predisposition of non-aneurysmal spontaneous subarachnoid hemorrhage and may also point out the possible higher risk of perimesencephalic non-aneurysmal subarachnoid hemorrhage in the first-degree relatives of patients with perimesencephalic non-aneurysmal subarachnoid hemorrhage.

The relationship between perimesencephalic subarachnoid hemorrhage and deep venous system drainage pattern and calibrations

BACKGROUND AND PURPOSE

The purpose of this study is to investigate the relationship between Rosenthal basal vein (BVR) type and diameter and perimesencephalic nonaneurysmal subarachnoid hemorrhage (P-SAH).

MATERIALS AND METHODS

Aneurysmal subarachnoid hemorrhage (A-SAH), P-SAH, and control groups were evaluated, and BVRs were classified by type. BVR diameters in patients were measured.

RESULTS

There was a statistically significant difference of BVR drainage types between groups (P=.002). BVR diameters of patients with normal drainage pattern in P-SAH group were significantly smaller than those in both other groups (P<.001).

CONCLUSION

There is a relationship between P-SAH and BVR primitive drainage type. P-SAH risk increases in parallel with decreasing caliber of BVR in patients with normal drainage pattern.

Anatomical variants of the basal vein of Rosenthal: prevalence in idiopathic subarachnoid hemorrhage

BACKGROUND

Spontaneous, non traumatic subarachnoid hemorrhage (SAH) is a significant clinical problem that occurs most commonly as a result of aneurysm rupture. In approximately 15 % of cases, nor aneurysm or other vascular malformation can be identified by cerebral angiography as origin of the hemorrhage, and these are commonly defined as idiopathic SAH (ISAH). Because of the negative angiography, limited extension of the bleeding with prevalent prepontine pattern and the benign prognosis, the venous causes has been preferred rather than the arterial ones. In the literature recent studies have suggested a possible contribution by primitive variants of Basal vein of Rosenthal (BVR) in its the pathogenesis of ISAH, commonly grouped according Watanabe classification (type A, B and C). In this paper we evaluated the prevalence of anatomical variants of BVR in ISAH.

METHODS

Venous drainage at angiography was retrospectively analyzed in 40 patients with ISAH and in 40 with unruptured aneurysms as controls.

RESULTS AND CONCLUSIONS

Previous studies displayed a significant prevalence of BVR type C variants in ISAH. Conversely in our study we recognized variant B as prevalent, in which the BVR bifurcates to drain anteriorly into the uncal vein and posteriorly into the Galenic system. Similarly to variant C (in which the BVR drains via perimesencephalic "bridging" veins into cavernous, sphenoparietal, petrosal sinus or directly into transverse sinus) also variant B might be subjected to those stress mechanisms and intrinsic system 'fragility' and for reasons yet to determine, sets off a consequent hemorrhage with clinical and radiological features typical of ISAH.

Cerebral arterial fenestrations: a common phenomenon in unexplained subarachnoid haemorrhage

BACKGROUND

Fenestrations of intracranial arteries are variants resulting from incomplete fusion of vessels during development with unknown clinical significance. They are best visualised with 3D rotational angiography (3DRA).

OBJECTIVE

In a prospective consecutive series of patients with suspected aneurysms, 3DRA was performed to identify not only the potential bleeding source but also to assess the frequency and location of any fenestrations of intracranial arteries.

METHODS

In 287 consecutive patients with possible intracranial aneurysms (accidental discovery or previous history of SAH), 3DRAs were prospectively performed, and the location of subarachnoid haemorrhage was assessed by CT.

RESULTS

Of 174 patients presenting with SAH, 153 had saccular aneurysms, and in 21 cases (12.1 %), no source of bleeding was found. In 20 of these 21 patients with "unexplained SAH" (95.2 %) an arterial fenestration was detected in the neighbourhood of the clot. The incidence of fenestration in the 153 aneurysmal SAH patients was 22.9 %, and it was 23.3 % in 266 patients with intracranial aneurysms (113 accidental and 153 ruptured).

CONCLUSIONS

Arterial fenestration was detected in 22.9 % of ruptured cerebral aneurysms, in contrast with 95.2 % in patients with unexplained SAH, the difference being statisctically significant (p < 0.01). Fenestration is a developmental defect, a structural wall weakness possibly making the vessel prone to rupture. Its incidence of nearly 100 % may suggest a connection with idiopathic SAH. The presented data indicate that arterial fenestrations are generally overlooked, and they can be considered as one of the candidates for the source of idiopathic SAH.

Nonaneurysmal subarachnoid hemorrhage: an update

Nonaneurysmal subarachnoid hemorrhage (NA-SAH) constitutes a heterogeneous group of patients, both perimesencephalic (PMN-SAH) and non-perimesencephalic (nPMN-SAH). Despite many reports and case series, the etiology of NA-SAH remains uncertain. The differences in clinical course and outcome between PMN-SAH and nPMN-SAH are evident and have to be taken into consideration at the time of admission, as aggressive diagnostic evaluation and management are required for latter patient. In terms of diagnostic evaluation, the most important determination is to differentiate PMN-SAH from nPMN-SAH and aneurysmal SAH. PMN-SAH can be distinguished on CT in the majority of patients, but should be confirmed by a negative cerebral angiography. In addition, Convexal NA-SAH is another important subtype of NA-SAH associated with diverse etiologies and symptoms, although prognosis is generally favorable.