Surgical management of acute subdural haematomas: current practice patterns in the United Kingdom and the Republic of Ireland.

INTRODUCTION: Uncertainty remains as to the role of decompressive craniectomy (DC) for primary evacuation of acute subdural haematomas (ASDH). In 2011, a collaborative group was formed in the UK with the aim of answering the following question: "What is the clinical- and cost-effectiveness of decompressive craniectomy, in comparison with craniotomy for adult patients undergoing primary evacuation of an ASDH?" The proposed RESCUE-ASDH trial (Randomised Evaluation of Surgery with Craniectomy for patients Undergoing Evacuation of Acute Subdural Haematoma) is a multicentre, pragmatic, parallel group randomised trial of DC versus craniotomy for adult head-injured patients with an ASDH. In this study, we used an online questionnaire to assess the current practice patterns in the management of ASDH in the UK and the Republic of Ireland, and to gauge neurosurgical opinion regarding the proposed RESCUE-ASDH trial. MATERIALS AND METHODS: A questionnaire survey of full members of the Society of British Neurological Surgeons and members of the British Neurosurgical Trainees Association was undertaken between the beginning of May and the end of July 2012. RESULTS: The online questionnaire was answered by 95 neurosurgeons representing 31 of the 32 neurosurgical units managing adult head-injured patients in the UK and the Republic of Ireland. Forty-five percent of the respondents use primary DC in at least 25% of patients with ASDH. In addition, of the 22 neurosurgical units with at least two Consultant respondents, only three units (14%) showed intradepartmental agreement regarding the proportion of their patients receiving a primary DC for ASDH. CONCLUSION: The survey results demonstrate that there is significant uncertainty as to the optimal surgical technique for primary evacuation of ASDH. The fact that the majority of the respondents are willing to become collaborators in the planned RESCUE-ASDH trial highlights the relevance of this important subject to the neurosurgical community in the UK and Ireland.

Increased expression of fatty acid binding protein 4 and leptin in resident macrophages characterises atherosclerotic plaque rupture.

OBJECTIVE: Resident macrophages play an important role in atheromatous plaque rupture. The macrophage gene expression signature associated with plaque rupture is incompletely defined due to the complex cellular heterogeneity in the plaque. We aimed to characterise differential gene expression in resident plaque macrophages from ruptured and stable human atheromatous lesions. METHODS AND RESULTS: We performed genome-wide expression analyses of isolated macrophage-rich regions of stable and ruptured human atherosclerotic plaques. Plaques present in carotid endarterectomy specimens were designated as stable or ruptured using clinical, radiological and histopathological criteria. Macrophage-rich regions were excised from 5 ruptured and 6 stable plaques by laser micro-dissection. Transcriptional profiling was performed using Affymetrix microarrays. The profiles were characteristic of activated macrophages. At a false discovery rate of 10%, 914 genes were differentially expressed between stable and ruptured plaques. The findings were confirmed in fourteen further stable and ruptured samples for a subset of eleven genes with the highest expression differences (p < 0.05). Pathway analysis revealed that components of the PPAR/Adipocytokine signaling pathway were the most significantly upregulated in ruptured compared to stable plaques (p = 5.4 × 10(-7)). Two key components of the pathway, fatty-acid binding-protein 4 (FABP4) and leptin, showed nine-fold (p = 0.0086) and five-fold (p = 0.0012) greater expression respectively in macrophages from ruptured plaques. CONCLUSIONS: We found differences in gene expression signatures between macrophages isolated from stable and ruptured human atheromatous plaques. Our findings indicate the involvement of FABP4 and leptin in the progression of atherosclerosis and plaque rupture, and suggest that down-regulation of PPAR/adipocytokine signaling within plaques may have therapeutic potential.

Temporal trends in head injury outcomes from 2003 to 2009 in England and Wales.

BACKGROUND: Case fatality rates after blunt head injury (HI) did not improve in England and Wales between 1994 and 2003. The United Kingdom National Institute of Clinical Excellence subsequently published HI management guidelines, including the recommendation that patients with severe head injuries (SHIs) should be treated in specialist neuroscience units (NSU). The aim of this study was to investigate trends in case fatality and location of care since the introduction of national HI clinical guidelines. METHODS: We conducted a retrospective cohort study using prospectively recorded data from the Trauma and Audit Research Network (TARN) database for patients presenting with blunt trauma between 2003 and 2009. Temporal trends in log odds of death adjusted for case mix were examined for patients with and without HI. Location of care for patients with SHI was also studied by examining trends in the proportion of patients treated in non-NSUs. RESULTS: Since 2003, there was an average 12% reduction in adjusted log odds of death per annum in patients with HI (n=15,173), with a similar but smaller trend in non-HI trauma mortality (n=48,681). During the study period, the proportion of patients with HI treated entirely in non-NSUs decreased from 31% to 19%, (p <0.01). INTERPRETATION: The reduction in odds of death following HI since 2003 is consistent with improved management following the introduction of national HI guidelines and increased treatment of SHI in NSUs.

Modulating effect of apolipoprotein E polymorphisms on secondary brain insult and outcome after childhood brain trauma.

OBJECTIVE: The aim of this study was to determine the relationship between apolipoprotein E (APO E) alleles, the amount of cerebral perfusion pressure (CPP) insult and outcome in children after brain trauma. MATERIALS AND METHODS: In a prospective two-centre case-control study, the APO E genotypes of 65 critically ill children admitted after brain trauma were correlated with age-related CPP insult quantification, conscious state at the time of discharge from intensive care and global outcome at 6 months post-injury. One hundred sixty healthy age- and sex-matched children were genotyped as controls. RESULTS: The CPP insult level among the e4 carriers with poor outcome was significantly less than the non-e4 carriers (p=0.03). Homozygotic e3 patients with good recovery did so despite having suffered nearly 26 times more CPP insult than those who were not e3 homzygous (p=0.02). CONCLUSION: Different APO E alleles may potentially affect cerebral ischaemic tolerance differently in children after brain trauma.

The effect of the results of the STICH trial on the management of spontaneous supratentorial intracerebral haemorrhage in Newcastle.

Recently, the Surgical Trial in IntraCerebral Haemorrhage (STICH) was unable to show an overall benefit from 'early surgery' compared with a policy of 'initial conservative treatment'. Here, we evaluated the impact of the STICH results on the management of spontaneous supratentorial intracerebral haemorrhage (ICH) in the Newcastle upon Tyne Hospitals. The STICH results were released to the Neurosurgery Department at Newcastle General Hospital in November 2003; using ICD-10 data, we analysed ICH admissions before (2002) and after (2004, 2006, 2007) this. We assessed numbers of Neurosurgery and Stroke Unit admissions, numbers of clot evacuation procedures, and 30-day mortality rate (Neurosurgery vs. Stroke Unit admissions). Subarachnoid haemorrhage (SAH) admissions data were also collected to corroborate our findings. There were 478 spontaneous supratentorial ICH admissions in total; 156 in 2002, 120 in 2004, 106 in 2006 and 96 in 2007. SAH admissions remained remarkably constant over this period. Neurosurgery admissions decreased significantly across the four time periods, from 71% of total ICH admissions (n = 156) in 2002 to 55% (n = 96) in 2007, and Stroke Unit admissions increased significantly from 8% (n = 156) in 2002 to 30% (n = 96) in 2007 (chi(2) = 20.968, p < 0.001, df = 3). Clot evacuation procedures also decreased significantly from 32% (n = 111) of Neurosurgery admissions in 2002 to 17% (n = 53) in 2007 (chi(2) = 11.919, p = 0.008, df = 3). 30-day mortality increased in Neurosurgery from 14% of Neurosurgery admissions (n = 111) in 2002 to 26% (n = 53) in 2007, and decreased in the Stroke Unit, from 42% of Stroke Unit admissions (n = 12) in 2002 to 17% (n = 29) in 2007. The STICH results have significantly impacted ICH management in Newcastle, with a trend towards fewer Neurosurgery admissions and clot evacuations, and increased Stroke Unit admissions. The role of surgery for ICH remains controversial, and randomization continues in STICH II for patients with superficial lobar ICH.

Lumbar subcutaneous shunt: a novel technique for therapeutic decision making in normal pressure hydrocephalus (NPH) and benign intracranial hypertension (BIH).

Selecting patients who will benefit from a permanent CSF diversion procedure in benign intracranial hypertension (BIH) or communicating hydrocephalus due to normal pressure hydrocephalus (NPH) has inherent problems. The percutaneous introduction of a lumbar subcutaneous shunt (LSS) under local anaesthesia facilitates both a prolonged CSF drainage under aseptic conditions and also elicits an adequate clinical response. We describe the technique of a lumbar subcutaneous shunt and our experience with its use in patients with BIH and NPH. Postprocedure changes in the patients' clinical status were noted. Patients with a transient clinical improvement underwent a subsequent definitive CSF diversion; those with a sustained clinical improvement or no change in symptoms had no further procedure.

The measurement of brain tissue stiffness in-vivo.

BACKGROUND: There is considerable interest in surgical decompression as a management strategy (RescueICP) for intractable intracranial hypertension. After such an operation measurements of intracranial pressure (ICP) and thus cerebral perfusion pressure (CPP) become less meaningful. Measurements of the biomechanical properties of the brain may be one measure capable of detecting changing status of such patients. However these properties of the brain are neither documented or well understood. We have developed an indentation probe capable of making measurements of human brain stiffness. METHOD: The device consists of an indenting tip of depth 2 mm and diameter 12 mm surrounded by an annular body of 20 mm diameter. Measurements are made by two load cells, connected through interface electronics to a laptop computer. FINDINGS: Laboratory measurements show the probe to provide accurate and repeatable measurements over a range of zero to 10N. Inter-operator variability from six healthcare professionals had a coefficient of variance of 8.75%. Measurements obtained during surgery from a patient undergoing tumour resection were towards the lower end of the device's measurable range. CONCLUSIONS: We have determined that this indentation device has a linear response and that the inter- and intra-operator variability is low. Although the device is still in an early stage of development, preliminary results during intracranial surgery demonstrate that this device is capable of measuring in-vivo tissue stiffness. Further work is required to derive a quantitative "stiffness index" from the two load curves. In addition a standard operation method is required so that consistent and repeatable measurements are made. The device may be of value in assessing patients after decompressive craniectomy.

The prognostic value of serum S-100B protein in spontaneous subarachnoid haemorrhage.

BACKGROUND: Despite the major progress in neurophysiological monitoring, there are still difficulties in the early identification and quantification of cerebral damage after a stroke. In this prospective study we examined the associations between serum S-100B protein, a serum marker of brain injury, and initial neurological-neuroimaging severity, secondary deterioration, external ventricular drainage (EVD: therapeutic intervention) and outcome in patients with subarachnoid haemorrhage (SAH). METHOD: We recorded all pertinent clinical data of 52 patients with SAH and measured S-100B serum levels on admission and every 24 h for a maximum of 9 consecutive days. Mann-Whitney U-test and Kruskal Wallis analysis were employed to assess the association of S-100B levels with all variables of interest. Log-rank test was used to evaluate survival and Cox's proportional hazard regression analysis to define the significant predictors of survival rate. FINDINGS: Admission S-100B was statistically significantly associated with initial neurological status, neuroimaging severity, and one-year outcome (p = 0.0002, 0.001, and 0.017, Kruskal Wallis analysis). Admission S-100B above 0.3 microg/L predicted unfavourable outcome (p < 0.0001, log rank test) and constituted an independent predictor of short-term survival (p = 0.035 Cox's proportional hazard regression analysis) with a hazard ratio of 2.2 (95% C.I.: 1.06-4.6) indicating a more than doubling of death probability. Secondary neurological deterioration associated with S-100B increase (p < 0.0001) and external ventricular drainage (EVD) with S-100B reduction (p = 0.003, Wilcoxon signed rank test). CONCLUSIONS: Serum S-100B protein seems to be a useful biochemical indicator of neurological - neuroimaging severity, secondary deterioration, EVD (therapeutic intervention), and outcome in patients with SAH.

Decompressive craniectomy in traumatic brain injury: the randomized multicenter RESCUEicp study (www.RESCUEicp.com).

The RESCUEicp (Randomized Evaluation of Surgery with Craniectomy for Uncontrollable Elevation of intracranial pressure) study has been established to determine whether decompressive craniectomy has a role in the management of patients with traumatic brain injury and raised intracranial pressure that does not respond to initial treatment measures. We describe the concept of decompressive craniectomy in traumatic brain injury and the rationale and protocol of the RESCUEicp study.

Intraventricular hemorrhage and hydrocephalus after spontaneous intracerebral hemorrhage: results from the STICH trial.

INTRODUCTION: Intraventricular hemorrhage (IVH), either independent of or as an extension of intracranial bleed, is thought to carry a grave prognosis. Although the effect of IVH on outcome in patients with subarachnoid hemorrhage has been extensively reviewed in the literature, reports of spontaneous intracerebral hemorrhage (ICH) in similar situations have been infrequent. The association of hydrocephalus in such situations and its influence on outcome is also uncertain. PATIENTS AND METHODS: As a sub-analysis of data obtained through the international Surgical Trial in Intracerebral Hemorrhage (STICH), the impact of IVH, with or without the presence of hydrocephalus, on outcome in patients with spontaneous ICH was analyzed. CT scans of randomized patients were examined for IVH and/or hydrocephalus. Other characteristics of hematoma were evaluated to see if they influenced outcome, as defined by the STICH protocol. RESULTS: Favorable outcomes were more frequent when IVH was absent (31.4% vs. 15.1%; p < 0.00001). The presence of hydrocephalus lowered the likelihood of favorable outcome still further to 11.5% (p = 0.031). In patients with IVH, early surgical intervention had a more favorable outcome (17.8%) compared to initial conservative management (12.4%) (p = 0.141). CONCLUSION: The presence of IVH and hydrocephalus are independent predictors of poor outcome in spontaneous ICH. Early surgery is of some benefit in those with IVH.

The significance of crossovers after randomization in the STICH trial.

INTRODUCTION: Of all forms of stroke, spontaneous intracerebral haemorrhage (ICH) causes the highest morbidity and mortality. The Surgical Trial in Intracerebral Haemorrhage (STICH) found no difference in outcomes between patients randomized to surgical or conservative treatment. PATIENTS AND METHODS: Of 530 patients randomized to initial conservative treatment, 140 crossed over to surgery. This study examines the variables associated with crossover. RESULTS: Dominant features of the crossover group were: male, (p = 0.04), right-sided clot (p = 0.03), lobar clot (p = 0.003), clot volume (median 64 mL for crossovers vs. 38 mL for others, p < 0.00001), midline shift (median 6 mm for crossovers vs. 3 mm for others, p < 0.00001), superficial clot (median 1.3 mm for crossovers vs. 11.5 mm for others, p < 0.00001), and randomization within 12 hours of ictus (p < 0.0005). Thalamic location (p = 0.002) was under-represented. Intraventricular haemorrhage, hydrocephalus, and focal deficits were not associated with crossover. Craniotomy was the method of evacuation in 85% of crossover patients. CONCLUSIONS: Crossover to surgery was more likely when ICH had these features: Right side, lobar location, superficial, large volume, big shift, and early randomization. Crossovers formed a worse prognostic group compared to non-crossovers. Surgery did not affect trial results, which were analyzed by intention-to-treat.

Critical thresholds of intracranial pressure and cerebral perfusion pressure related to age in paediatric head injury.

BACKGROUND: The principal strategy for managing head injury is to reduce the frequency and severity of secondary brain insults from intracranial pressure (ICP) and cerebral perfusion pressure (CPP), and hence improve outcome. Precise critical threshold levels have not been determined in head injured children. OBJECTIVE: To create a novel pressure-time index (PTI) measuring both duration and amplitude of insult, and then employ it to determine critical insult thresholds of ICP and CPP in children. METHODS: Prospective, observational, physiologically based study from Edinburgh and Newcastle, using patient monitored blood pressure, ICP, and CPP time series data. The PTI for ICP and CPP for 81 children, using theoretical values derived from physiological norms, was varied systematically to derive critical insult thresholds which delineate Glasgow outcome scale categories. RESULTS: The PTI for CPP had a very high predictive value for outcome (receiver operating characteristic analyses: area under curve = 0.957 and 0.890 for mortality and favourable outcome, respectively) and was more predictive than for ICP. Initial physiological values most accurately predicted favourable outcome. The CPP critical threshold values determined for children aged 2-6, 7-10, and 11-15 years were 48, 54, and 58 mm Hg. respectively. CONCLUSIONS: The PTI is the first substantive paediatric index of total ICP and CPP following head injury. The insult thresholds generated are identical to age related physiological values. Management guidelines for paediatric head injuries should take account of these CPP thresholds to titrate appropriate pressor therapy.

Clinical comparison of tympanic membrane displacement with invasive intracranial pressure measurements.

A non-invasive method of assessing intracranial pressure (ICP) would be of benefit to patients with abnormal cerebral pathology that could give rise to changes in ICP. In particular, it would assist the regular monitoring of hydrocephalus patients. This study evaluated a technique using tympanic membrane displacement (TMD) measurements, which has been reported to provide a reliable, non-invasive measure of ICP. A group of 135 hydrocephalus patients was studied, as well as 13 patients with benign intracranial hypertension and a control group of 77 volunteers. TMD measurements were carried out using the Marchbanks measurement system analyser and compared between the groups. In 36 patients, invasive measurements of ICP carried out at the same time were compared with the TMD values. A highly significant relationship was found between TMD and ICP but intersubject variability was high and the predictive value of the technique low. Taking the normal range of ICP to be 10-15 mmHg, the predictive limits of the regression are an order of magnitude wider than this and therefore Vm cannot be used as a surrogate for ICP. In conclusion, TMD measurements do not provide a reliable non-invasive measure of ICP in patients with shunted hydrocephalus.

Head injuries: a study evaluating the impact of the NICE head injury guidelines.

BACKGROUND: The NICE head injury guidelines recommend a different approach in the management of head injury patients. It suggests that CT head scan should replace skull x ray (SXR) and observation/admission as the first investigation. We wished to determine the impact of NICE on SXR, CT scan, and admission on all patients with head injury presenting to the ED setting and estimate the cost effectiveness of these guidelines, which has not been quantified to date. DESIGN: Study of head injury patients presenting to two EDs before and after implementation of NICE guidelines METHODS: The rate of SXR, CT scan, and admission were determined six months before and one month after NICE implementation in both centres. The before study also looked at predicted rates had NICE been applied. This enabled predicted and actual cost effectiveness to be determined. RESULT: 1130 patients with head injury were studied in four 1 month periods (two in each centre). At the teaching hospital, the CT head scan rate more than doubled (3% to 7%), the SXR declined (37% to 4%), while the admission rate more than halved (9% to 4%). This represented a saving of 3381 pounds sterling per 100 head injury PATIENTS: greater than predicted with no adverse events. At the District General Hospital, the CT head scan rate more than quadrupled (1.4% to 9%), the SXR dropped (19 to 0.57%), while the admission rate declined (7% to 5%). This represented a saving of 290 pounds sterling per 100 head injury patients: less than predicted. CONCLUSION: The implementation of the NICE guidelines led to a two to fivefold increase in the CT head scan rate depending on the cases and baseline departmental practice. However, the reduction in SXR and admission appears to more than offset these costs without compromising patient outcomes.

Regional differences in outcome from subarachnoid haemorrhage.

BACKGROUND: Surgeons are increasingly placed under pressure to accept publication of their results and to abide by recommendations to change practice which others derive. Considerable concern exists about misinterpretation of such data. The issue is well illustrated by this study. METHOD: Data on outcome following treatment for subarachnoid haemorrhage were prospectively collected from 1993-1998 in two centres in the British Isles: Newcastle and Nottingham. FINDINGS: Initial examination of this data suggest a substantial difference in the performance favouring Nottingham over Newcastle. The odds of a poor outcome was 1:1.86 in Newcastle compared with 1:4.26 in Nottingham giving an odds ratio of 2.3 in favour of Nottingham and this difference was highly significant with p<0.00001. On a more detailed examination taking account of confounding variables, this difference disappeared entirely. Newcastle was able to operate a less selective admissions policy than Nottingham because of the deficiency of beds at the latter unit. A summary of these results has been published elsewhere. INTERPRETATION: These results illustrate the dangers of applying statistical tools developed for simpler situations such as industrial process control to complex medical problems. We conclude that comprehensive and accurate data on all factors likely to influence the outcome for a particular treatment should be collected as an absolute prerequisite to any judgments being made on apparent statistical differences between the performances of differing units.

Effect of awake Carotid Endarterectomy under local anaesthesia on peri-operative blood pressure: blood pressure is normalised when carotid stenosis is treated under local anaesthesia.

BACKGROUND: Carotid Endarterectomy can be performed under local, regional or general anaesthesia. One of the most important effects of the type of anaesthetic used is on the systemic blood pressure. Although variations in blood pressure during and following carotid endarterectomy have been studied previously, the effects of awake carotid endarterectomy under local anaesthesia on blood pressure and its comparison with similar procedures under similar types of anaesthesia have not. METHODS: Peri-operative blood pressure measurements were collected from the records of 25 consecutive patients for each of the following five procedures; Carotid Endarterectomy under general anaesthesia (CEAGA), Anterior Cervical Discectomy and Fusion under general anaesthesia (ACDF), Cerebral Angiography under local anaesthesia (ANG), Carotid Endarterectomy patients under local anaesthesia who were symptomatic (CEALAS) and Carotid Endarterectomy patients under local anaesthesia who were asymptomatic (CEALAA). The recordings were then analysed to find out if there were any clinically significant variations in peri-operative blood pressure. FINDINGS: There is a significant and consistent difference when the pre-operative value was compared with the 4 hour and 24 hour post-operative recordings between the local and general anaesthetic groups for carotid endarterectomy. Carotid endarterectomy reduces the systolic and diastolic blood pressures post-operatively when performed under local anaesthesia and only the diastolic pressure was reduced when performed under general anaesthesia. CONCLUSION: The study provides evidence about the effect of carotid endarterectomy on the systemic blood pressure and its variations when performed under different types of anaesthesia. There is significant post-operative reduction in both the systolic and diastolic blood pressure values and the intraoperative fluctuation is minimal when local anaesthesia is used. Further studies are required to find out how this affects the long-term blood pressure and clinical outcome of the patient.

Bispectral index monitoring may not reliably indicate cerebral ischaemia during awake carotid endarterectomy.

BACKGROUND: Intraoperative ischaemia during carotid cross-clamping in patients undergoing carotid endarterectomy (CEA) is a major complication and prompt recognition of insufficient collateral blood supply is crucial. Electroencephalogram (EEG) is believed to be one of the useful forms of monitoring cerebrovascular insufficiency during CEA. The aim of this study was to evaluate the utility of bispectral index (BIS) monitoring, a processed EEG parameter, for the reliable detection of intraoperative cerebral ischaemia during awake CEA. METHODS: We monitored 52 patients continuously with the BIS monitor together with assessment of neurological function (contralateral upper and lower limb strength and the verbal component of the Glasgow Coma Scale for speech) in patients undergoing awake CEA. RESULTS: Overall mean BIS value in all patients was 96 (SD 2.9). In five patients who showed clinical evidence of cortical ischaemia during carotid cross-clamping, there was no change in the original range of BIS values throughout the procedure (96.7 [3.2]). In one patient BIS values decreased to 38 about 5 min after the incision and recovered within the next 10 min. The mean BIS value in the remaining 46 patients who did not develop clinical signs of ischaemia was 95.4 (2.6). Three cases are presented which demonstrate the inability of the BIS monitor to detect cerebral ischaemia. CONCLUSIONS: Lack of correlation of BIS with the signs of cerebral ischaemia during CEA makes it unreliable for detection of cerebrovascular insufficiency. We conclude that awake neurological testing is the preferred method of monitoring in these patients.

Risk-benefit analysis of the treatment of unruptured intracranial aneurysms.

OBJECTIVES: To determine under what circumstances repair of unruptured intracranial aneurysms may be beneficial. METHODS: A life expectancy analysis of patients with unruptured aneurysms with and without repair based on prospective data from the International Study of Unruptured Intracranial Aneurysms (ISUIA). RESULTS: Life years are lost at all ages by repairing anterior circulation aneurysms under 7 mm in diameter in patients with no history of a subarachnoid haemorrhage from another aneurysm (incidental). For all other aneurysms the number of life years saved by repair is dependent on the patient's age at the time when repair is undertaken. Between 2 and 40 years are saved by repairing aneurysms in patients aged 20 years. These benefits fall to 0 when remaining life expectancy falls below 15-35 years, corresponding to the age range of 45-70 years. CONCLUSIONS: Repair of unruptured aneurysms benefits patients harbouring them by improving life expectancy except in certain circumstances. The exceptions are patients with remaining life expectancy less than 15-35 years or aged 45-70 (depending on aneurysm size and location) and patients with aneurysms of the anterior circulation under 7 mm in diameter with no history of a previous subarachnoid haemorrhage. These results are based on the findings of the ISUIA and are dependent on their accuracy.

Predicting the risk of rupture of intracranial aneurysms based on anatomical location.

The location of intracranial aneurysms may be a significant independent risk factor for predicting aneurysm rupture. A recent report found high bleed rates from posterior communicating artery aneurysms which had not previously been noted. On this distinction hangs the decision whether to treat a large number of unruptured aneurysms. In the recent publication by the International Study of Unruptured Intracranial Aneurysms (ISUIA), two bleeds from small incidental posterior communicating artery aneurysms were noted and these aneurysms were reported to have a similar risk to aneurysms of the posterior circulation and as a result were grouped with them. This was a post hoc analysis so the justification for this assertion is tenuous. The hypothesis that posterior communicating aneurysms are of similar risk to posterior circulation aneurysms requires further testing on other data before it can be confidently accepted. A review of the literature was undertaken to define relative risks of rupture for different anatomical locations and to test the above hypothesis. Eleven papers were found to contain sufficient data to calculate rupture rates for anatomical sub groups. Studies contained a total of 30,204 patient years of follow up. Results showed the internal carotid artery to be the commonest site for unruptured aneurysms (38%). Aneurysms located in the posterior circulation had an overall annual bleed rate of 1.8%. This compares with 0.49% for the anterior circulation. The bleed rate from aneurysms of the posterior communicating artery (0.46% per year) was similar to that of the rest of the anterior circulation. The ISUIA post hoc hypothesis fails when tested on these data and the ISUIA data should be re-analysed with posterior communicating artery aneurysms grouped with the anterior circulation where they more traditionally belong.