Is the Combination of Negative Computed Tomography Result and Negative Lumbar Puncture Result Sufficient to Rule Out Subarachnoid Hemorrhage?

Shifts in Diagnostic Testing for Headache in the Emergency Department, 2015 to 2021

Importance

Subarachnoid hemorrhage is typically diagnosed by noncontrast head computed tomography (CT); lumbar puncture is recommended if computed tomography is nondiagnostic, although CT cerebral angiography has been promoted as an alternative to lumbar puncture in this diagnostic pathway. The outcomes of this debate in practice have not been studied.

Objective

To determine whether CT cerebral angiography use has increased in lieu of lumbar puncture among emergency department (ED) patients with headache, with an increase in unruptured intracranial aneurysm detection.

Design, Setting, and Participants

This retrospective cohort study took place in 21 community EDs of an integrated health care system in Northern California between 2015 and 2021. Participants were adult (aged >17 years) health plan members with a chief concern of headache. Exclusions were prior diagnoses of subarachnoid hemorrhage, unruptured intracranial aneurysm, cerebral arteriovenous malformation, or cerebrospinal fluid shunt. Data were analyzed from October to November 2023.

Exposures

CT cerebral angiography and/or lumbar puncture during the ED encounter.

Main Outcomes and Measures

Primary and secondary outcomes were 14-day and 90-day unruptured intracranial aneurysm detection, respectively. Safety outcomes were missed diagnoses of subarachnoid hemorrhage or bacterial meningitis. The annual incidence of unruptured intracranial aneurysm detection was normalized to the incidence of subarachnoid hemorrhage (UIA:SAH ratio). Average annualized percentage changes were quantified using joinpoint regression analysis.

Results

Among 198 109 included ED encounters, the mean (SD) age was 47.5 (18.4) years; 140 001 patients (70.7%) were female; 29 035 (14.7%) were Black or African American, 59 896 (30.2%) were Hispanic or Latino, and 75 602 (38.2%) were White. Per year, CT cerebral angiography use increased (18.8%; 95% CI, 17.7% to 20.3%) and lumbar punctures decreased (-11.1%; 95% CI, -12.0% to -10.4%), with a corresponding increase in the 14-day UIA:SAH ratio (3.5%; 95% CI, 0.9% to 7.4%). Overall, computed tomography cerebral angiography use increased 6-fold relative to lumbar puncture, with a 33% increase in the detection of UIA. Results were similar at 90 days and robust to sensitivity analyses. Subarachnoid hemorrhage (1004 cases) and bacterial meningitis (118 cases) were misdiagnosed in 5% and 18% of cases, respectively, with no annual trends (P = .34; z1003 = .95 and P = .74; z117 = -.34, respectively).

Conclusions and Relevance

In this cohort study of ED patients with headache, increases in CT cerebral angiography use were associated with fewer lumbar punctures and higher detection of unruptured intracranial aneurysms, with no significant change in missed diagnoses of subarachnoid hemorrhage or bacterial meningitis. While this shift in diagnostic strategy appeared safe in the short-term, the long-term consequences remain unclear.

Modern Imaging of Aneurysmal Subarachnoid Hemorrhage

In this review, we discuss the imaging of aneurysmal subarachnoid hemorrhage (SAH). We discuss emergency brain imaging, aneurysm detection techniques, and the management of CTA-negative SAH. We also review the concepts of cerebral vasospasm and delayed cerebral ischemia that occurs after aneurysm rupture and their impact on patient outcomes. These pathologies are distinct, and the use of multimodal imaging modalities is essential for prompt diagnosis and management to minimize morbidity from these conditions. Lastly, new advances in artificial intelligence and advanced imaging modalities such as PET and MR imaging scans have been shown to improve the detection of aneurysms and potentially predict outcomes early in the course of SAH.

Management of patients presenting to the emergency department with sudden onset severe headache: systematic review of diagnostic accuracy studies

Objective

Advances in imaging technologies have precipitated uncertainty and inconsistency in the management of neurologically intact patients presenting to the Emergency Department (ED) with non-traumatic sudden onset severe headache with a clinical suspicion of subarachnoid haemorrhage (SAH). The objective of this systematic review was to evaluate diagnostic strategies in these patients.

Methods

Studies assessing any decision rule or diagnostic test for evaluating neurologically intact adults with a severe headache, reaching maximum intensity within 1 hour, were eligible. Eighteen databases (including MEDLINE and Embase) were searched. Quality was assessed using QUADAS-2. Where appropriate, hierarchical bivariate meta-analysis was used to synthesise diagnostic accuracy results.

Results

Thirty-seven studies were included. Eight studies assessing the Ottawa SAH clinical decision rule were pooled; sensitivity 99.5% (95% CI 90.8 to 100), specificity 24% (95% CI 15.5 to 34.4). Four studies assessing CT within 6 hours of headache onset were pooled; sensitivity 98.7% (95% CI 96.5 to 100), specificity 100% (95% CI 99.7 to 100). The sensitivity of CT beyond 6 hours was considerably lower (≤90%; 2 studies). Three studies assessing lumbar puncture (LP; spectrophotometric analysis) following negative CT were pooled; sensitivity 100% (95% CI 100 to 100), specificity 95% (95% CI 86.0 to 98.5).

Conclusion

The Ottawa SAH Rule rules out further investigation in only a small proportion of patients. CT undertaken within 6 hours (with expertise of a neuroradiologist or radiologist who routinely interprets brain images) is highly accurate and likely to be sufficient to rule out SAH; CT beyond 6 hours is much less sensitive. The CT–LP pathway is highly sensitive for detecting SAH and some alternative diagnoses, although LP results in some false positive results.

Evaluating xanthochromia in the diagnosis of subarachnoid haemorrhage in Scotland in the Era of modern computed tomography

AIM

Cerebrospinal fluid (CSF) analysis for xanthochromia is routinely used to exclude subarachnoid haemorrhage (SAH). In this study, we evaluated the sensitivity and specificity of xanthochromia (by NEQAS-spectrophotometry) in routine clinical practice in three acute hospitals, in patients with suspected SAH. We explored whether including CSF red cell count (RCC) with xanthochromia improved diagnostic accuracy.

METHODS

In this retrospective analysis, all xanthochromia results were assessed over three consecutive years. Clinical information and Registry data were analysed to find all patients diagnosed with SAH. We correlated xanthochromia data with clinical and radiological findings.

RESULTS

There were 1761 xanthochromia performed. Of these, 26 (1.5%) were positive, 1624 (92%) negative and 72 (4.1%) were inconclusive. Of the 26 tests that were positive, 9 (35%) had confirmed SAH, 17 (65%) were falsely positive, with no false negative tests in our series. Xanthochromia identified 6% of all SAH diagnosed in the study. Incorporating RCC <1000 with xanthochromia, reducing false positive tests by 38% and inconclusive test by 85%.

CONCLUSION

The positive yield of xanthochromia is low but identified 6% of SAH. NEQAS-spectrophotometry is an excellent diagnostic method with 100% sensitivity, 99% specificity. Incorporating RCC markedly reduces false positive and inconclusive tests reducing need for further imaging.

Diagnosis and Management of Headaches in the Emergency Department (ED) in Adults and Children

Background

Headache accounts for a significant number of cases presenting to the Emergency Department (ED) and has a high societal cost, contributed by recurrent ED and clinic visits, and unnecessary diagnostic tests.

Objective

This review article covers the important clinical tools needed to evaluate headaches in both adults and children in the ED.

Methods

Medline/PubMed was searched using the keywords "Emergency department", "headache", "adult", "pediatric", "clinical assessment", "diagnosis" and "treatment", in the title or abstract. The search covers the period from 1 January 1990 to 31 December 2019.

Results

The articles selected were based on their relevancy to the objective of this review article. Additional relevant publications were identified from article references lists.

Conclusion

The emergency physician plays a key role in differentiating between primary and secondary headaches. Within the limited ED resources, appropriate diagnostic testing should be used to identify the life-threatening headaches. This will ensure patients are given the appropriate evidence-based pharmacological therapy and holistic management.

Is a Lumbar Puncture Required to Rule Out Atraumatic Subarachnoid Hemorrhage in Emergency Department Patients With Headache and Normal Brain Computed Tomography More Than Six Hours After Symptom Onset?

BACKGROUND

Atraumatic subarachnoid hemorrhage (SAH) is a deadly condition that most commonly presents as acute, severe headache. Controversy exists concerning evaluation of SAH based on the time from onset of symptoms, specifically if the headache occurred > 6 h prior to patient presentation.

CLINICAL QUESTION

Do patients undergoing evaluation for atraumatic SAH who have a negative computed tomography (CT) scan of the head obtained more than 6 h after symptom onset require a subsequent lumbar puncture to rule out the diagnosis?

EVIDENCE REVIEW

Studies retrieved included a retrospective cohort study, two prospective cohort studies, and a case-control study. These studies provide estimates of the diagnostic accuracy of head CT imaging obtained > 6 h from symptom onset and diagnostic test characteristics of subsequent lumbar puncture.

CONCLUSION

The probability of SAH above which emergency clinicians should perform a lumbar puncture is 1.0%. This threshold is essentially the same as the estimated probability of SAH in patients with a negative head CT obtained more than 6 h from symptom onset. Emergency physicians might reasonably decide to either perform or forego this procedure. Consequently, we contend that the decision whether to perform lumbar puncture in these instances is an excellent candidate for shared decision-making.

Headache in the Emergency Department: Avoiding Misdiagnosis of Dangerous Secondary Causes, An Update

In the initial assessment of the headache patient, the emergency physician must consider several dangerous secondary causes of headache. A thorough history and physical examination, along with consideration of a comprehensive differential diagnosis may alert the emergency physician to the diagnosis of a secondary headache particularly when the history is accompanied by any of the following clinical features: sudden/severe onset, focal neurologic deficits, altered mental status, advanced age, active or recent pregnancy, coagulopathy, malignancy, fever, visual deficits, and/or loss of consciousness.

Excluding subarachnoid haemorrhage within 24 hours: to LP or not to LP?

BACKGROUND AND PURPOSE

Subarachnoid haemorrhage (SAH) is a potentially life-threatening cause of acute headache. Current conventional practice in the United Kingdom (UK) is for head computed tomography (CT) followed by cerebrospinal fluid (CSF) xanthochromia analysis if the head CT is normal. However, with increasing radiological accuracy, head CT alone may be sufficient to exclude SAH without requiring CSF xanthochromia for confirmation. This study aims to determine whether CSF xanthochromia is still required to confirm exclusion of SAH after normal head CT within a tertiary referral centre.

METHODS

Data was obtained from Nottingham University Hospitals (NUH) NHS Trust databases on 999 patients presenting with symptoms suspicious of SAH from 2012 to 2015. All patients had CSF xanthochromia analysis when head CT was normal or inconclusive for suspected SAH.

RESULTS

A total of 179 patients were diagnosed with SAH (17.9%). 176 patients were diagnosed radiologically and 3 patients required further investigations. The 3 of the 802 patients who underwent lumbar puncture (LP) and were identified as having had SAH presented more than 24 hours after ictus. When stratified according to the time of presentation, a normal CT head was observed in those who presented within 24 hours from ictus (sensitivity of 100% [95% CI 92.5-100] and negative predictive value of 100% [97.2-100]).

CONCLUSION

Within a tertiary referral centre for SAH, a normal head CT has a very high negative predictive value to exclude SAH when carried out within 24 hours from ictus provided a 3rd generation CT scanner is utilised, and the scan is reported by a neuroradiologist. CSF xanthochromia analysis in this cohort may still be indicated in those presenting with a high clinical suspicion of SAH and in hospital settings where neuroradiologists or 3rd generation CT scanners are not easily accessible.

Godwin SA, Cherkas DS, Panagos PD, Shih RD, Byyny R, Wolf SJ. Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department With Acute Headache

This clinical policy from the American College of Emergency Physicians addressed key issues in the evaluation and management of adult patients presenting to the emergency department with acute headache. A writing subcommittee conducted a systematic review of the literature to derive evidence-based recommendations to answer the following clinical questions: (1) In the adult emergency department patient presenting with acute headache, are there risk-stratification strategies that reliably identify the need for emergent neuroimaging? (2) In the adult emergency department patient treated for acute primary headache, are nonopioids preferred to opioid medications? (3) In the adult emergency department patient presenting with acute headache, does a normal noncontrast head computed tomography scan performed within 6 hours of headache onset preclude the need for further diagnostic workup for subarachnoid hemorrhage? (4) In the adult emergency department patient who is still considered to be at risk for subarachnoid hemorrhage after a negative noncontrast head computed tomography, is computed tomography angiography of the head as effective as lumbar puncture to safely rule out subarachnoid hemorrhage? Evidence was graded and recommendations were made based on the strength of the available data.

Prospective Implementation of the Ottawa Subarachnoid Hemorrhage Rule and 6-Hour Computed Tomography Rule

Background and Purpose- The Ottawa subarachnoid hemorrhage (SAH) rule identifies patients with headache requiring no testing for SAH, while the 6-hour computed tomography (CT) rule guides when to forgo a lumbar puncture. Our objectives were to: (1) estimate the clinical impact of the Ottawa SAH rule and the 6-hour-CT rule on testing rates (ie, CT, lumbar puncture, CT angiography); (2) validate the 6-hour-CT rule for SAH when applied prospectively in a new cohort of patients. Methods- We conducted a multicenter prospective before/after implementation study from 2011 to 2016 with 6 months follow-up at 6 tertiary-care Canadian Academic Emergency Departments. Consecutive alert, neurologically intact adults with headache were included. For intervention period, physicians were given a 1-hour lecture, pocket cards, posters were installed, and physicians indicated Ottawa SAH rule criteria when ordering CTs. SAH was defined by blood on CT, xanthochromia in cerebrospinal fluid, or >1×10⁶/L red blood cells in cerebrospinal fluid with aneurysm. Results- We enrolled 3672 patients, 1743 before and 1929 after implementation, including 188 with SAH. Proportions undergoing CT was unchanged (88.0% versus 87.5%; P=0.643). Lumbar puncture use decreased (38.9% versus 25.9%; P<0.0001). Additional testing following CT (ie, lumbar puncture or CT angiography) decreased (51.3% versus 42.2%; P<0.0001). Admissions declined (9.8% versus 7.4%; P=0.011). Mean emergency department stay was unchanged (6.3±4.0 versus 6.4±4.2 hours; P=0.685). The Ottawa SAH rule was 100% (95% CI, 98.1%-100%) sensitive, and the 6-hour-CT rule was 95.5% (95% CI, 89.8-98.5) sensitive for SAH. The 6-hour-CT rule missed 5 SAHs: 1 radiology misread, 2 incidental aneurysms, 1 nonaneurysmal cause, and 1 profoundly anemic patient. Conclusions- The Ottawa SAH rule and the 6-hour-CT rule are highly sensitive and can be used routinely when SAH is considered in patients with headache. Implementing both rules was associated with a meaningful decrease in testing and admissions to hospital.

Validation of the Ottawa Subarachnoid Hemorrhage Rule in patients with acute headache

BACKGROUND

We previously derived the Ottawa Subarachnoid Hemorrhage Rule to identify subarachnoid hemorrhage (SAH) in patients with acute headache. Our objective was to validate the rule in a new cohort of consecutive patients who visited an emergency department.

METHODS

We conducted a multicentre prospective cohort study at 6 university-affiliated tertiary-care hospital emergency departments in Canada from January 2010 to January 2014. We included alert, neurologically intact adult patients with a headache peaking within 1 hour of onset. Treating physicians in the emergency department explicitly scored the rule before investigations were started. We defined subarachnoid hemorrhage as detection of any of the following: subarachnoid blood visible upon computed tomography of the head (from the final report by the local radiologist); xanthochromia in the cerebrospinal fluid (by visual inspection); or the presence of erythrocytes (> 1 × 10⁶/L) in the final tube of cerebrospinal fluid, with an aneurysm or arteriovenous malformation visible upon cerebral angiography. We calculated sensitivity and specificity of the Ottawa SAH Rule for detecting or ruling out subarachnoid hemorrhage.

RESULTS

Treating physicians enrolled 1153 of 1743 (66.2%) potentially eligible patients, including 67 with subarachnoid hemorrhage. The Ottawa SAH Rule had 100% sensitivity (95% confidence interval [CI] 94.6%-100%) with a specificity of 13.6% (95% CI 13.1%-15.8%), whereas neuroimaging rates remained similar (about 87%).

INTERPRETATION

We found that the Ottawa SAH Rule was sensitive for identifying subarachnoid hemorrhage in otherwise alert and neurologically intact patients. We believe that the Ottawa SAH Rule can be used to rule out this serious diagnosis, thereby decreasing the number of cases missed while constraining rates of neuroimaging.

Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a neurological emergency with high risk of neurological decline and death. Although the presentation of a thunderclap headache or the worst headache of a patient's life easily triggers the evaluation for SAH, subtle presentations are still missed. The gold standard for diagnostic evaluation of SAH remains noncontrast head computed tomography (CT) followed by lumbar puncture if the CT is negative for SAH. Management of patients with SAH follows standard resuscitation of critically ill patients with the emphasis on reducing risks of rebleeding and avoiding secondary brain injuries.

Determination of a Testing Threshold for Lumbar Puncture in the Diagnosis of Subarachnoid Hemorrhage after a Negative Head Computed Tomography: A Decision Analysis

OBJECTIVE

The objective was to determine the testing threshold for lumbar puncture (LP) in the evaluation of aneurysmal subarachnoid hemorrhage (SAH) after a negative head computed tomography (CT). As a secondary aim we sought to identify clinical variables that have the greatest impact on this threshold.

METHODS

A decision analytic model was developed to estimate the testing threshold for patients with normal neurologic findings, being evaluated for SAH, after a negative CT of the head. The testing threshold was calculated as the pretest probability of disease where the two strategies (LP or no LP) are balanced in terms of quality-adjusted life-years. Two-way and probabilistic sensitivity analyses (PSAs) were performed.

RESULTS

For the base-case scenario the testing threshold for performing an LP after negative head CT was 4.3%. Results for the two-way sensitivity analyses demonstrated that the test threshold ranged from 1.9% to 15.6%, dominated by the uncertainty in the probability of death from initial missed SAH. In the PSA the mean testing threshold was 4.3% (95% confidence interval = 1.4% to 9.3%). Other significant variables in the model included probability of aneurysmal versus nonaneurysmal SAH after negative head CT, probability of long-term morbidity from initial missed SAH, and probability of renal failure from contrast-induced nephropathy.

CONCLUSIONS

Our decision analysis results suggest a testing threshold for LP after negative CT to be approximately 4.3%, with a range of 1.4% to 9.3% on robust PSA. In light of these data, and considering the low probability of aneurysmal SAH after a negative CT, classical teaching and current guidelines addressing testing for SAH should be revisited.

Subarachnoid haemorrhage guidelines and clinical practice: a cross-sectional study of emergency department consultants' and neurospecialists' views and risk tolerances

OBJECTIVES

To establish if emergency medicine and neuroscience specialist consultants have different risk tolerances for investigation of suspected spontaneous subarachnoid haemorrhage (SAH), and to establish if their risk-benefit appraisals concur with current guidelines.

SETTING

4 major neuroscience centres in London.

PARTICIPANTS

58 consultants in emergency medicine and neuroscience specialities (neurology, neurosurgery and neuroradiology) participated in an anonymous survey.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measure was the highest stated acceptable risk of missing SAH in the neurologically intact patient presenting with sudden onset headache. Secondary outcome measures included agreement with guideline recommendations, risk/benefit appraisal and required performance of diagnostic tests, including lumbar puncture.

RESULTS

Emergency department clinicians accepted almost 3 times the risk of a missed SAH diagnosis compared with the neuroscience specialists (2.8% vs 1.1%; p=0.02), were more likely to accept a higher risk of missed diagnosis for the benefit of a non-invasive test (p=0.04) and were more likely to disagree with current published guidelines stipulating the need for LP in all CT-negative cases (p=0.001).

CONCLUSIONS

Divergence from recognised procedures for SAH investigation is often criticised and attributed to a lack of knowledge of guidelines. This study indicates that divergence from guidelines may be explained by alternative risk-benefit appraisals made by doctors with their patients. Guideline recommendations may gain wider acceptance if they accommodate the requirements of the doctors and patients using them. Further study of clinical risk tolerance may help explain patterns of diagnostic test use and other variations in healthcare delivery.

New clinical decision rule to exclude subarachnoid haemorrhage for acute headache: a prospective multicentre observational study

OBJECTIVE

To ensure good outcomes in the management of subarachnoid haemorrhage (SAH), accurate prediction is crucial for initial assessment of patients presenting with acute headache. We conducted this study to develop a new clinical decision rule using only objectively measurable predictors to exclude SAH, offering higher specificity than the previous Ottawa SAH Rule while maintaining comparable sensitivity.

DESIGN

Multicentre prospective cohort study.

SETTING

Tertiary-care emergency departments of five general hospitals in Japan from April 2011 to March 2014.

PARTICIPANTS

Eligible patients comprised 1781 patients aged >15 years with acute headache, excluding trauma or toxic causes and patients who presented in an unconscious state.

MAIN OUTCOME MEASURES

Definitive diagnosis of SAH was based on confirmation of SAH on head CT or lumbar puncture findings of non-traumatic red blood cells or xanthochromia.

RESULTS

A total of 1561 patients were enrolled in this study, of whom 277 showed SAH. Using these enrolled patients, we reached a rule with mainly categorical predictors used in previous reports, called the 'Ottawa-like rule', offering 100% sensitivity when using any of age ≥40 years, neck pain or stiffness, altered level of consciousness or onset during exertion. Using the 1317 patients from whom blood samples were obtained, a new rule using any of systolic blood pressure >150 mm Hg, diastolic blood pressure >90 mm Hg, blood sugar >115 mg/dL or serum potassium <3.9 mEq/L offered 100% sensitivity (95% CI 98.6% to 100%) and 14.5% specificity (12.5% to 16.9%), while the Ottawa-like rule showed the same sensitivity with a lower specificity of 8.8% (7.2% to 10.7%).

CONCLUSIONS

While maintaining equal sensitivity, our new rule seemed to offer higher specificity than the previous rules proposed by the Ottawa group. Despite the need for blood sampling, this method can reduce unnecessary head CT in patients with acute headache.

TRIAL REGISTRATION NUMBER

UMIN 00004871.

Headache in the Emergency Department: Avoiding Misdiagnosis of Dangerous Secondary Causes

There are a number of dangerous secondary causes of headaches that are life, limb, brain, or vision threatening that emergency physicians must consider in patients presenting with acute headache. Careful history and physical examination targeted at these important secondary causes of headache will help to avoid misdiagnosis in these patients. Patients with acute thunderclap headache have a differential diagnosis beyond subarachnoid hemorrhage. Considering the "context" of headache "PLUS" some other symptom or sign is one strategy to help focus the differential diagnosis.

Looking at "thunderclap headache" differently? Circa 2016

The term “thunderclap headache” (TCH) was first coined in 1986 by Day and Raskin to describe headache that was the presenting feature of an underlying unruptured cerebral aneurysm. The term is now well established to describe the abrupt onset headache seen with many other conditions and is also now included in The International Classification of Headache Disorders 3^rd edition beta version rubric 4.4. An essential to label an acute headache as “TCH” and differentiate it from other “sudden onset, severe headaches” is the arbitrary time frame of 1 min from onset to peak intensity for “TCH.” What happens in practice, however, is that even those “sudden onset, severe headaches” that do not strictly fulfill the definition criteria are also labeled as “TCH” and investigated with the same speed and in the same sequence and managed based on the underlying cause. This article begins by questioning the validity and usefulness of this “one minute” arbitrary time frame to define “TCH,” particularly since this time frame is very difficult to assess in practice and is usually done on a presumptive subjective basis. The article concludes with suggestions for modification of the current investigation protocol for this emergency headache scenario. This proposal for “a change in practice methodology” is essentially based on (1) the fact that in the last two decades, we now have evidence for many more entities other than just subarachnoid hemorrhage that can present as “TCH” or “sudden onset, severe headache” and (2) the evidence from literature which shows that advances in imaging technology using higher magnet strength, better contrast, and newer acquisition sequences will result in a better diagnostic yield. It is therefore time now, in our opinion, to discard current theoretical time frames, use self-explanatory terminologies with practical implications, and move from “lumbar puncture (LP) first” to “LP last!”

False-negative Interpretations of Cranial Computed Tomography in Aneurysmal Subarachnoid Hemorrhage

OBJECTIVES

Prior studies examining the sensitivity of cranial computed tomography (CT) for the detection of subarachnoid hemorrhage (SAH) have used the final radiology report as the reference standard. However, optimal sensitivity may have been underestimated due to misinterpretation of reportedly normal cranial CTs. This study aims to estimate the incidence of missed CT evidence of SAH among a cohort of patients with aneurysmal SAH (aSAH).

METHODS

We performed a retrospective chart review of emergency department (ED) encounters within an integrated health delivery system between January 2007 and June 2013 to identify patients diagnosed with aSAH. All initial noncontrast CTs from aSAH cases diagnosed by lumbar puncture (LP) and angiography following a reportedly normal noncontrast cranial CT (CT-negative aSAH) were then reviewed in a blinded, independent fashion by two board-certified neuroradiologists to assess for missed evidence of SAH. Reviewers rated the CT studies as having definite evidence of SAH, probable evidence of SAH, or no evidence of SAH. Control patients who underwent a negative evaluation for aSAH based on cranial CT and LP results were also included at random in the imaging review cohort.

RESULTS

A total of 452 cases of aSAH were identified; 18 (4%) were cases of CT-negative aSAH. Of these, seven (39%) underwent cranial CT within 6 hours of headache onset, and two (11%) had their initial CTs formally interpreted by board-certified neuroradiologists. Blinded independent CT review revealed concordant agreement for either definite or probable evidence of SAH in nine of 18 (50%) cases overall and in five of the seven (71%) CTs performed within 6 hours of headache onset. Inter-rater agreement was 83% for definite SAH and 72% for either probable or definite SAH.

CONCLUSIONS

CT evidence of SAH was frequently present but unrecognized according to the final radiology report in cases of presumed CT-negative aSAH. This finding may help explain some of the discordance between prior studies examining the sensitivity of cranial CT for SAH.

Can the combination of a negative computed tomography result and a negative lumbar puncture safely exclude the diagnosis of subarachnoid hemorrhage in patients with thunderclap headache?

CLINICAL QUESTION

How many patients who had a negative computed tomography and lumbar puncture result on initial evaluation were diagnosed with subarachnoid hemorrhage in the subsequent 6 months to 3 years?

ARTICLE CHOSEN

Perry J, Spacek A, Forbes M, et al. Is the combination of negative computed tomography result and negative lumbar puncture result sufficient to rule out subarachnoid hemorrhage? Ann Emerg Med 2008;51:707-13.

OBJECTIVE

To determine the sensitivity of both a negative computed tomography and a negative lumbar puncture in ruling out subarachnoid hemorrhage.

Clinical Guidelines for the Emergency Department Evaluation of Subarachnoid Hemorrhage

BACKGROUND

Subarachnoid hemorrhage (SAH) is frequently caused by the rupture of an intracranial aneurysmal vessel or arteriovenous malformation, leading to a cascade of events that can result in severe disability or death. When evaluating for this diagnosis, emergency physicians have classically performed a noncontrast computed tomography (NCCT) scan, followed by a lumbar puncture (LP). Recently, however, as CT technology has advanced, many studies have questioned the necessity of the LP in the SAH diagnostic algorithm and have instead advocated for noninvasive techniques, such as NCCT alone or NCCT with CT angiogram (CTA).

OBJECTIVE

The primary goal of this literature search was to determine the appropriate emergency department (ED) management of patients with suspected SAH.

METHODS

A MEDLINE literature search from October 2008 to June 2015 was performed using the keywords computed tomography AND subarachnoid hemorrhage AND lumbar puncture, while limiting the search to human studies written in the English language. General review articles and single case reports were omitted. Each of the selected articles then underwent a structured review.

RESULTS

Ninety-one articles were identified, with 31 papers being considered appropriate for analysis. These studies then underwent a rigorous review from which recommendations were developed.

CONCLUSIONS

The literature search supports that NCCT followed by CTA is a reasonable approach in the evaluation of ED patients with possible SAH.

Differentiation between traumatic tap and aneurysmal subarachnoid hemorrhage: prospective cohort study

OBJECTIVES

To describe the findings in cerebrospinal fluid from patients with acute headache that could distinguish subarachnoid hemorrhage from the effects of a traumatic lumbar puncture.

DESIGN

A substudy of a prospective multicenter cohort study.

SETTING

12 Canadian academic emergency departments, from November 2000 to December 2009.

PARTICIPANTS

Alert patients aged over 15 with an acute non-traumatic headache who underwent lumbar puncture to rule out subarachnoid hemorrhage.

MAIN OUTCOME MEASURE

Aneurysmal subarachnoid hemorrhage requiring intervention or resulting in death.

RESULTS

Of the 1739 patients enrolled, 641 (36.9%) had abnormal results on cerebrospinal fluid analysis with >1 × 10(6)/L red blood cells in the final tube of cerebrospinal fluid and/or xanthochromia in one or more tubes. There were 15 (0.9%) patients with aneurysmal subarachnoid hemorrhage based on abnormal results of a lumbar puncture. The presence of fewer than 2000 × 10(6)/L red blood cells in addition to no xanthochromia excluded the diagnosis of aneurysmal subarachnoid hemorrhage, with a sensitivity of 100% (95% confidence interval 74.7% to 100%) and specificity of 91.2% (88.6% to 93.3%).

CONCLUSION

No xanthochromia and red blood cell count <2000 × 10(6)/L reasonably excludes the diagnosis of aneurysmal subarachnoid hemorrhage. Most patients with acute headache who meet this cut off will need no further investigations and aneurysmal subarachnoid hemorrhage can be excluded as a cause of their headache.

Aneurysmal subarachnoid haemorrhage from a neuroimaging perspective

Neuroimaging is a key element in the management of patients suffering from subarachnoid haemorrhage (SAH). In this article, we review the current literature to provide a summary of the existing neuroimaging methods available in clinical practice. Noncontrast computed tomography is highly sensitive in detecting subarachnoid blood, especially within 6 hours of haemorrhage. However, lumbar puncture should follow a negative noncontrast computed tomography scan in patients with symptoms suspicious of SAH. Computed tomography angiography is slowly replacing digital subtraction angiography as the first-line technique for the diagnosis and treatment planning of cerebral aneurysms, but digital subtraction angiography is still required in patients with diffuse SAH and negative initial computed tomography angiography. Delayed cerebral ischaemia is a common and serious complication after SAH. The modern concept of delayed cerebral ischaemia monitoring is shifting from modalities that measure vessel diameter to techniques focusing on brain perfusion. Lastly, evolving modalities applied to assess cerebral physiological, functional and cognitive sequelae after SAH, such as functional magnetic resonance imaging or positron emission tomography, are discussed. These new techniques may have the advantage over structural modalities due to their ability to assess brain physiology and function in real time. However, their use remains mainly experimental and the literature supporting their practice is still scarce.

An updated definition of stroke for the 21st century: a statement for healthcare professionals from the American Heart Association/American Stroke Association

Despite the global impact and advances in understanding the pathophysiology of cerebrovascular diseases, the term "stroke" is not consistently defined in clinical practice, in clinical research, or in assessments of the public health. The classic definition is mainly clinical and does not account for advances in science and technology. The Stroke Council of the American Heart Association/American Stroke Association convened a writing group to develop an expert consensus document for an updated definition of stroke for the 21st century. Central nervous system infarction is defined as brain, spinal cord, or retinal cell death attributable to ischemia, based on neuropathological, neuroimaging, and/or clinical evidence of permanent injury. Central nervous system infarction occurs over a clinical spectrum: Ischemic stroke specifically refers to central nervous system infarction accompanied by overt symptoms, while silent infarction by definition causes no known symptoms. Stroke also broadly includes intracerebral hemorrhage and subarachnoid hemorrhage. The updated definition of stroke incorporates clinical and tissue criteria and can be incorporated into practice, research, and assessments of the public health.

Interpreting red blood cells in lumbar puncture: distinguishing true subarachnoid hemorrhage from traumatic tap

OBJECTIVES

The study purpose was to determine the optimal use of lumbar puncture (LP) red blood cell (RBC) counts to identify subarachnoid hemorrhage (SAH) when some blood remains in the final tube.

METHODS

A case series was performed at a tertiary emergency department (ED). Records of 4,496 consecutive adult patients billed for LPs between 2001 and 2009 were reviewed. Inclusion criteria were headache (HA), final tube RBCs ≥ 5, and neurovascular imaging within 2 weeks of the visit. Demographics, relevant history and physical examination components, LP results, and neuroimaging findings were recorded for 280 patients. True-positive (TP) and true-negative (TN) SAH were strictly defined. Primary outcomes were the areas under the receiver operating characteristic curves (AUC) for final tube RBC count, differential RBC count between the final and initial tubes, and absolute differential RBC count between the final and initial tubes divided by the mean RBC count of the two tubes (also called the percent change in RBC count).

RESULTS

There were 26 TP and 196 TN results; 58 patients were neither. The TP group consisted of 19 patients with visible or possible SAH on imaging (17 on noncontrast head computed tomography [CT; 12 definite and five possible] and two on magnetic resonance imaging), six with xanthochromia and a vascular lesion (aneurysm or arteriovenous malformation [AVM] > 2 mm), and one with xanthochromia and polymerase chain reaction (PCR)-positive meningitis. As a test for SAH, final tube RBC AUC was 0.85 (95% confidence interval [CI] = 0.80 to 0.91). Interval likelihood ratios (LRs) for final tube RBC count were LR 0 (95% CI = 0 to 0.3) for RBCs < 100, LR 1.6 (95% CI = 1.1 to 2.3) for 100 < RBCs < 10,000, and LR 6.3 (95% CI = 4.8 to 23.4) for RBCs > 10,000. Differential RBC count was not associated with SAH, with AUC 0.45 (95% CI = 0.31 to 0.60). However, the percent change in RBC count between the final and initial tubes had an AUC 0.84 (95% CI = 0.78 to 0.90), and the optimal test threshold for SAH was 0.63, with positive LR 3.6 (95% CI = 2.7 to 4.7) and negative LR 0.10 (95% CI = 0.03 to 0.4) for percent change <63% and >63%, respectively. This test added additional independent information to the final tube RBC count based on improved logistic regression model fit and discriminatory ability as measured by the LR test and c statistic, respectively.

CONCLUSIONS

Final LP tube RBC count and the percent change in RBC count, but not the simple differential count between the final and initial tubes, were associated with SAH. In this sample, there were no patients with SAH who had RBCs < 100 in the final tube, and RBCs > 10,000 increased the odds of SAH by a factor of 6.

Emergency diagnosis of subarachnoid hemorrhage: an evidence-based debate

BACKGROUND

The diagnosis of subarachnoid hemorrhage is of paramount concern in patients presenting to the Emergency Department (ED) with acute headache. Computed tomography followed by lumbar puncture is a time-honored practice, but recent technologic advances in magnetic resonance imaging with magnetic resonance angiography and computed tomography with computed tomography angiography can present alternatives for clinicians and patients.

OBJECTIVE

The aim of this article was to compare diagnostic strategies for ED patients in whom subarachnoid hemorrhage is suspected.

METHODS

We analyze and discuss current protocols, in addition to summarizing the advantages and disadvantages of each method.

RESULTS

Through our residency's journal club, we organized an evidence-based debate that pitted proponents of the three subarachnoid hemorrhage diagnostic strategies against one another. Proponents of each strategy described its advantages and disadvantages. Briefly, computed tomography/lumbar puncture is time honored and effective, but is limited by complications and indeterminate lumbar puncture results. Magnetic resonance imaging with magnetic resonance angiography might be more effective in late presentations and can visualize aneurysms, yet has limited availability. Computed tomography with computed tomography angiography offers rapid diagnosis and is considered the most sensitive for diagnosing aneurysms, but has the highest radiation exposure.

CONCLUSIONS

Each of the three strategies used to diagnose subarachnoid hemorrhage has advantages and disadvantages with which clinicians should be familiar. Patient factors (e.g., age, body habitus, and risk factors), presentation factors (e.g., time from headache onset and severity of presentation), and institutional factors (availability of magnetic resonance imaging with magnetic resonance angiography) can influence the choice of protocol.

Clinical management guidelines for subarachnoid haemorrhage. Diagnosis and treatment

OBJECTIVE

To update the Spanish Society of Neurology's guidelines for subarachnoid haemorrhage diagnosis and treatment.

MATERIAL AND METHODS

A review and analysis of the existing literature. Recommendations are given based on the level of evidence for each study reviewed.

RESULTS

The most common cause of spontaneous subarachnoid haemorrhage (SAH) is cerebral aneurysm rupture. Its estimated incidence in Spain is 9/100 000 inhabitants/year with a relative frequency of approximately 5% of all strokes. Hypertension and smoking are the main risk factors. Stroke patients require treatment in a specialised centre. Admission to a stroke unit should be considered for SAH patients whose initial clinical condition is good (Grades I or II on the Hunt and Hess scale). We recommend early exclusion of aneurysms from the circulation. The diagnostic study of choice for SAH is brain CT (computed tomography) without contrast. If the test is negative and SAH is still suspected, a lumbar puncture should then be performed. The diagnostic tests recommended in order to determine the source of the haemorrhage are MRI (magnetic resonance imaging) and angiography. Doppler ultrasonography studies are very useful for diagnosing and monitoring vasospasm. Nimodipine is recommended for preventing delayed cerebral ischaemia. Blood pressure treatment and neurovascular intervention may be considered in treating refractory vasospasm.

CONCLUSIONS

SAH is a severe and complex disease which must be managed in specialised centres by professionals with ample experience in relevant diagnostic and therapeutic processes.

Cost-effectiveness of diagnostic strategies for evaluation of suspected subarachnoid hemorrhage in the emergency department

OBJECTIVES

Diagnosing subarachnoid hemorrhage (SAH) in emergency department (ED) patients is challenging. Potential diagnostic strategies include computed tomography (CT) only, CT followed by lumbar puncture (CT/LP), CT followed by magnetic resonance imaging and angiography (CT/MRA), and CT followed by CT angiography (CT/CTA). The objective was to determine the relative cost-effectiveness of diagnostic strategies for SAH.

METHODS

 The authors created a decision model to evaluate the cost-effectiveness of SAH diagnostic strategies in ED patients with suspected SAH. Clinical probabilities were obtained from published data; sensitivity analyses were conducted across plausible ranges.

RESULTS

  In the base-case scenario, CT-only had a cost of $10,339 and effectiveness of 20.25 quality-adjusted life-years (QALYs), and CT/LP had a cost of $15,120 and effectiveness of 20.366 QALYs. Among the alternative strategies, CT/CTA had a cost of $12,840 and effectiveness of 20.24 QALYs, and CT/MRA had a cost of $16,207 and effectiveness of 20.27 QALYs. In sensitivity analyses, probability of severe disability from SAH, sensitivity of noncontrast CT, and specificity of LP and MRA were key drivers of the model, and CT-only and CT/LP were preferable.

CONCLUSIONS

In the base-case scenario, CT-only was preferable to the CT/CTA and CT/MRA strategies. When considering sensitivity analyses and the current medicolegal environment, there are no overwhelming differences between the cost-effectiveness of CT/LP and the alternative strategies to suggest that clinicians should abandon the standard CT/LP approach.

Nontraumatic subarachnoid hemorrhage in the setting of negative cranial computed tomography results: external validation of a clinical and imaging prediction rule

STUDY OBJECTIVE

Clinical variables can reliably exclude a diagnosis of nontraumatic subarachnoid hemorrhage in patients with negative cranial computed tomography (CT) results. We externally validated 2 decision rules with 100% reported sensitivity for a diagnosis of subarachnoid hemorrhage, among patients undergoing lumbar puncture after a negative cranial CT result: (1) clinical rule: presence of any combination of age 40 years and older, neck pain or stiffness, loss of consciousness, or headache onset during exertion; and (2) imaging rule: cranial CT performed within 6 hours of headache onset.

METHODS

This was a matched case-control study of patients presenting to 21 emergency departments between 2000 and 2011. Patients with a diagnosis of subarachnoid hemorrhage as determined by lumbar puncture after a negative cranial CT result were screened for inclusion. A matched control cohort was selected among patients with a diagnosis of headache after negative cranial CT and lumbar puncture results.

RESULTS

Fifty-five cases of subarachnoid hemorrhage meeting inclusion criteria were identified, 34 (62%) of which were attributed to cerebral aneurysms. External validation of the clinical rule demonstrated a sensitivity of 97.1% (95% confidence interval [CI] 88.6% to 99.7%), a specificity of 22.7% (95% CI 16.6% to 29.8%), and a negative likelihood ratio of 0.13 (95% CI 0.03 to 0.61) for a diagnosis of subarachnoid hemorrhage. External validation of the imaging rule revealed that 11 of 55 subarachnoid hemorrhage cases (20%) had negative cranial CT results for tests performed within 6 hours of headache onset.

CONCLUSION

The clinical rule demonstrated useful Bayesian test characteristics when retrospectively validated against this patient cohort. The imaging rule, however, failed to identify 20% of subarachnoid hemorrhage patients with a negative cranial CT result.

Sensitivity of newer-generation computed tomography scanners for subarachnoid hemorrhage: a Bayesian analysis

BACKGROUND

Subarachnoid hemorrhage (SAH) is a life-threatening condition considered in patients presenting to the emergency department (ED) with acute and severe-onset headache. Currently, the practice pattern for suspected SAH is to perform a non-contrasted computed tomography (CT) scan of the head, followed by lumbar puncture (LP) if the CT is negative. Newer-generation 16-slice CT scanners have been shown in one study to be very sensitive for SAH.

OBJECTIVE

We sought to validate these findings at our institution by retrospectively analyzing the sensitivity of our 16-slice or better CT scanner and performing a bayesian analysis with the results.

METHODS

We utilized ED electronic medical records and the Department of Neurosurgery research database to search for patients admitted from the ED with a diagnosis of SAH from January 1, 2005 to December 31, 2008. We found a total of 134 patients admitted with SAH during this time frame.

RESULTS

Average age was 53.8 years; 62% were female. Presenting complaint was headache in 57%, paresthesia or weakness in 7%, unresponsive in 10%, confusion or altered mental status in 5%, and "other" in 10%. Sensitivity of 16-slice or better CT scanner in our study was 131/134, or 97.8% (95% confidence interval 93.1-99.4%). No patient with a negative CT had a lesion requiring intervention.

CONCLUSION

Our study confirms the high sensitivity of 16-slice or better CT scanners for SAH. This calls into question the need for LP after negative head CT when 16-slice CT or better is used.

Retrospective audit of the investigation of patients with suspected acute subarachnoid haemorrhage

INTRODUCTION

Recommended investigational care (RIC) of emergency department (ED) patients with suspected subarachnoid haemorrhage comprises lumbar puncture (LP) to detect xanthochromia if the preceding CT scan is negative.

METHODS

Retrospective audit of the investigational care of 100 consecutive ED patients presenting with possible subarachnoid haemorrhage.

RESULTS

Of the 100 patients, 91 had negative CT, and 36 (39.6%) of these patients had an LP performed to detect xanthochromia (i.e. RIC). Fifty-five of 91 (60.4%) patients did not receive RIC. Of the 55 patients who did not receive RIC, 25 (45.5%) had a documented senior clinical decision not to perform an LP; 15 (27.3%) had no documented reason; five (9.1%) refused consent; two (3.6%) had an LP but no xanthochromia requested, one patient did not have an LP because of technical issues, six patients underwent CT angiography (CTA), and one patient underwent magnetic resonance angiography (MRA), in the absence of a LP, following a negative CT. Two patients underwent CTA following a negative xanthochromia result. Patients admitted to the emergency extended care unit had 6.85 times the odds of receiving RIC (95% CI 2.20-21.4).

CONCLUSIONS

Fifty-five (55) of 91 (60%) ED patients did not receive RIC. Fifteen of the 55 did not have any documented justification for not performing an LP with xanthochromia testing. Admission to an emergency extended care unit was a predictor of receiving RIC. Inappropriate use of CTA and MRA was identified. These findings have important implications for patient safety. Multifaceted strategies are required to close this evidence-practice gap.