Prevalence of Herniation and Intracranial Shift on Cranial Tomography in Patients With Subarachnoid Hemorrhage and a Normal Neurologic Examination

Objectives: Patients frequently present to the emergency department (ED) with headache. Those with sudden severe headache are often evaluated for spontaneous subarachnoid hemorrhage (SAH) with noncontrast cranial computed tomography (CT) followed by lumbar puncture (LP). The authors postulated that in patients without neurologic symptoms or signs, physicians could forgo noncontrast cranial CT and proceed directly to LP. The authors sought to define the safety of this option by having senior neuroradiologists rereview all cranial CTs in a group of such patients for evidence of brain herniation or midline shift. Methods: This was a retrospective study that included all patients with a normal neurologic examination and nontraumatic SAH diagnosed by CT presenting to a tertiary care medical center from August 1, 2001, to December 31, 2004. Two neuroradiologists, blinded to clinical information and outcomes, rereviewed the initial ED head CT for evidence of herniation or midline shift. Results: Of the 172 patients who presented to the ED with spontaneous SAH diagnoses by cranial CT, 78 had normal neurologic examinations. Of these, 73 had initial ED CTs available for review. Four of the 73 (5%; 95% confidence interval [CI] = 2% to 13%) had evidence of brain herniation or midline shift, including three (4%; 95% CI = 1% to 12%) with herniation. In only one of these patients was herniation or shift noted on the initial radiology report. Conclusions: Awake and alert patients with a normal neurologic examination and SAH may have brain herniation and/or midline shift. Therefore, cranial CT should be obtained before LP in all patients with suspected SAH. ACADEMIC EMERGENCY MEDICINE 2010; 17:423–428 © 2010 by the Society for Academic Emergency Medicine     

Can Computed Tomography Angiography of the Brain Replace Lumbar Puncture in the Evaluation of Acute‐onset Headache After a Negative Noncontrast Cranial Computed Tomography Scan?

Objectives: The primary goal of evaluation for acute‐onset headache is to exclude aneurysmal subarachnoid hemorrhage (SAH). Noncontrast cranial computed tomography (CT), followed by lumbar puncture (LP) if the CT is negative, is the current standard of care. Computed tomography angiography (CTA) of the brain has become more available and more sensitive for the detection of cerebral aneurysms. This study addresses the role of CT/CTA versus CT/LP in the diagnostic workup of acute‐onset headache. Methods: This article reviews the recent literature for the prevalence of SAH in emergency department (ED) headache patients, the sensitivity of CT for diagnosing acute SAH, and the sensitivity and specificity of CTA for cerebral aneurysms. An equivalence study comparing CT/LP and CT/CTA would require 3,000 + subjects. As an alternative, the authors constructed a mathematical probability model to determine the posttest probability of excluding aneurysmal or arterial venous malformation (AVM) SAH with a CT/CTA strategy. Results: SAH prevalence in ED headache patients was conservatively estimated at 15%. Representative studies reported CT sensitivity for SAH to be 91% (95% confidence interval [CI] = 82% to 97%) and sensitivity of CTA for aneurysm to be 97.9% (95% CI = 88.9% to 99.9%). Based on these data, the posttest probability of excluding aneurysmal SAH after a negative CT/CTA was 99.43% (95% CI = 98.86% to 99.81%). Conclusions: CT followed by CTA can exclude SAH with a greater than 99% posttest probability. In ED patients complaining of acute‐onset headache without significant SAH risk factors, CT/CTA may offer a less invasive and more specific diagnostic paradigm. If one chooses to offer LP after CT/CTA, informed consent for LP should put the pretest risk of a missed aneurysmal SAH at less than 1%. ACADEMIC EMERGENCY MEDICINE 2010; 17:444–451 © 2010 by the Society for Academic Emergency Medicine     

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.     

Sensitivity of New-generation Computed Tomography in Subarachnoid Hemorrhage

Objective: To determine the sensitivity of the initial new-generation CT (NGCT) scan interpretation for detection of acute nontraumatic subarachnoid hemorrhage (SAH) and to decide whether lumbar puncture (LP) should follow a "normal" NGCT scan.
Methods: A retrospective chart review was performed of patients admitted between March 1988 and July 1994 with proven SAH. Exclusion criteria were age <2 years, diagnosis other than acute SAH, history of head trauma within 24 hours before symptom onset, NGCT scan not done before diagnosis, and records not available. Patients were placed into two groups: symptom duration <24 hours (group 1) and >24 hours (group 2) prior to CT scan. The resolution of each NGCT scanner was recorded. An NGCT sceinner was defined as a third-generation scanner or more recent.
Results: Of 349 SAH patients, 181 met inclusion criteria. The sensitivity of NGCT scans for SAH was 93.1% for the group 1 patients ( n = 144) and 83.8% for the group 2 patients ( n = 37). The overall sensitivity was 91.2%. All the patients who had SAH not detected by NGCT scans were diagnosed by LP. There was no significant relationship between NGCT scanner resolution and sensitivity for SAH.
Conclusion: Initial interpretation of NGCT scans to detect SAH does not approach 100% sensitivity. A "normal" NGCT scan does not reliably exclude the need for LP in patients who have symptoms suggestive of SAH.     

The detection of nontraumatic subarachnoid hemorrhage: still a diagnostic challenge

Nontraumatic subarachnoid hemorrhage is one of the most elusive diagnoses in emergency medicine; it is a potentially lethal disease that is often considered and rarely found. The current practice as determined by the American College of Emergency Physicians 1996 Clinical Policy on Headache is a noncontrast head computed tomography (CT) followed by diagnostic lumbar puncture (LP) to exclude subarachnoid hemorrhage. Whereas the guideline does not consider pretest probability of subarachnoid hemorrhage in determining which patients require LP after negative head CT, patients' acceptance of LP, technical aspects of performing a LP in patients with nonideal anatomy, and risks associated with LP must all be considered when choosing to proceed with invasive testing. This article outlines the use of current testing modalities including CT, magnetic resonance imaging, angiography and LP to provide an up-to-date understanding of diagnostic testing for subarachnoid hemorrhage.     

Lumbar Puncture First: An Alternative Model for the Investigation of Lone Acute Sudden Headache

Subarachnoid hemorrhage (SAH) is a diagnosis often considered in patients presenting to the ED with acute sudden headaches, but with normal physical examinations. Standard of care today is for these patients to be investigated by noncontrast CT scan followed by lumbar puncture (LP) for negative CTs. However, given that most investigated patients have benign headaches, most of the CT and LP results are normal. The authors studied, by means of a theoretical analysis, the impact of an alternative diagnostic model, in which LP would be the first (and, in most cases, only) diagnostic test for patients suspected of SAH who met lone acute sudden headache (LASH) criteria. Given reasonable assumptions, for every 100 patients investigated, the "LP-first" model would result in 79 to 83 fewer CT scans and only seven to 11 additional LPs, as compared with traditional strategies. Among ED headache patients meeting LASH criteria, the authors believe use of this model could result in more efficient use of resources, minimal additional morbidity, and equal diagnostic accuracy for SAH.     

Diagnosis of subarachnoid hemorrhage in the emergency department

To decide which patients with headache ought to be evaluated for SAH, physicians should focus on specific elements of the patient history, such as onset, severity, and quality of the headache and associated symptoms. These questions should be asked and the responses documented for every patient with a headache. The physical examination should be compulsive with regard to vital signs, HEENT. and neurologic signs. Then, the physician should form an explicit differential diagnosis and have reasons for diagnosing migraine, tension, or sinus headache and other benign causes. If there is no clear-cut alternative hypothesis, the patient should be evaluated by CT and LP (if the CT is negative, equivocal, or technically inadequate). Physicians should understand the limitations of this diagnostic algorithm. In addition, the CSF should be carefully analyzed, including measuring the opening pressure. In patients whose CT scans and CSF analyses are normal, further testing is rarely indicated.     

The Ottawa subarachnoid hemorrhage clinical decision rule for classifying emergency department headache patients

BackgroundSubarachnoid hemorrhage (SAH) is a serious cause of headaches. The Ottawa subarachnoid hemorrhage (OSAH) rule helps identify SAH in patients with acute nontraumatic headache with high sensitivity, but provides limited information for identifying other intracranial pathology (ICP).ObjectivesTo assess the performance of the OSAH rule in emergency department (ED) headache patients and evaluate its impact on the diagnosis of intracranial hemorrhage (ICH) and other ICP.MethodWe conducted a retrospective cohort study from January 2016 to March 2017. Patients with acute headache with onset within 14 days of the ED visit, were included. We excluded patients with head trauma that occurred in the previous 7 days, new onset of abnormal neurologic findings, or consciousness disturbance. According to the OSAH rule, patients with any included predictors required further investigation.ResultsOf 913 patients were included, 15 of them were diagnosed with SAH. The OSAH rule had 100% (95% CI, 78.2%–100%) sensitivity and 37.0% (95% CI, 33.8–40.2%) specificity for identifying SAH. Twenty-two cases were identified as SAH or ICH with 100% sensitivity (95% CI, 84.6%–100%) and 37.3% (95% CI, 34.1%–40.5%) specificity. As for non-hemorrhagic ICP, both the sensitivity and negative predictive values (NPV) decreased to 75.0% (95% CI, 53.3%–90.2%) and 98.2% (95% CI, 96.1%–99.3%), respectively.ConclusionsThe OSAH rule had 100% sensitivity and NPV for diagnosing SAH and ICH with acute headache. The sensitivity and specificity were lower for non-hemorrhagic ICP. The OSAH rule may be an effective tool to exclude acute ICH and SAH in our setting.     

Computed Tomographic Angiography for the Evaluation of Aneurysmal Subarachnoid Hemorrhage

Objectives: Computed tomography (CT) followed by lumbar puncture (LP) is currently the criterion standard for diagnosing subarachnoid hemorrhage (SAH) in the emergency department (ED); however, this is based on studies involving a limited number of patients. The authors sought to assess the ability of CT angiography (CTA), a new diagnostic modality, in conjunction with CT/LP to detect SAH. Methods: Consecutive patients presenting to the ED with symptoms concerning for SAH were approached. All patients had an intravenous catheter placed and underwent a noncontrast head CT followed by CTA. Patients whose CT did not reveal evidence of SAH or other pathology underwent LP in the ED. CTAs were read within 24 hours by a neuroradiologist blinded to the patient's history. Results: A total of 131 patients were approached, 116 were enrolled, and 106 completed the study. In six of 116 patients (5.1%), aneurysm was found on CTA with normal CT and positive findings on LP; three had a positive CTA with normal CT and LP findings (one of which had a negative cerebral angiogram), and there was one false‐positive CTA. Follow‐up of all 131 patients showed no previously undiagnosed intracranial pathology. In this patient population, 4.3% (5/116) were ultimately found to have an SAH and/or aneurysm. Conclusions: In this pilot study, CTA was found to be useful in the detection of cerebral aneurysms and may be useful in the diagnosis of aneurysmal SAH. A larger multicenter study would be useful to confirm these results.     

Risk tolerance for the exclusion of potentially life-threatening diseases in the ED

Objective

Given the same pretest probability (10%) for subarachnoid hemorrhage (SAH), pulmonary embolism (PE), and acute coronary syndrome (ACS), we determined if differences exist in the risk tolerance for disease exclusion according to published guidelines given a negative test result.

Methods

Published guidelines that make practice recommendations on the evaluation of ACS, PE, and SAH were sought using the National Guideline Clearinghouse in low-risk settings. Second-order Monte Carlo simulation was performed to determine point estimates and confidence intervals (CIs) for posttest probabilities assuming a pretest probability of 10%.

Results

Guidelines recommend that patients with low-risk suspected ACS should undergo stress testing. For SAH, computed tomography (CT) followed by lumbar puncture (LP) is recommended without mention of pretest probability; and D-dimer testing is recommended to exclude PE in low-risk patients. Test sensitivity for thallium-201 single photon emission computed tomography (SPECT) was 89%, exercise echocardiogram was 85%, D-dimer testing was 95%, and CT/LP for SAH was 100% (as a gold standard) and CT only was 97.5%. Given a negative test result, for PE, posttest probability was 0.5% (95% CI 0.1%-0.9%); for SPECT, 1.1% (SD 0.5%-1.6%); and for exercise echocardiogram, 1.5% (95% CI 0.5%-2.5%) compared with a posttest probability of 0% for CT followed by LP for SAH. Using a CT-only approach gives a posttest probability of 0.2% (95% CI 0.2%-0.4%).

Conclusions

Guidelines for suspected PE and ACS allow small but nonzero calculated risk end points in low-risk settings, whereas SAH guidelines afford no misses. Because many gold standard tests are more invasive and can have adverse effects, guideline authors should consider adopting a standard acceptable miss rate as an end point for workups with low clinical suspicion to avoid the overuse of invasive testing.     

Subarachnoid hemorrhage diagnosis by computed tomography and lumbar puncture: Are fifth generation CT scanners better at identifying subarachnoid hemorrhage?

This study sought to determine the sensitivity and specificity of modern computed tomography (CT) scans for the diagnosis of subarachnoid hemorrhage (SAH). No studies have been done recently with fifth generation CT scanners to look at the diagnosis of SAH. A retrospective chart review was done of Emergency Department (ED), laboratory, and hospital records at Pitt County Memorial Hospital in Greenville, North Carolina over 1 year from January 1, 2002 to December 31, 2002. Patients presented with headache and had a CT scan of the head with a fifth generation multi-detector CT scanner followed by a lumbar puncture (LP) to rule out SAH. There were 177 patients who presented to the ED with headache and went on to have a CT scan and an LP to rule out SAH. No patients who had a negative CT were found to have a subarachoid hemorrhage. It is concluded that fifth generation CT scanners are probably more sensitive than earlier scanners at detecting SAH.     

Physician utilization of a portable computed tomography scanner in the intensive care unit

OBJECTIVE: To determine the utilization of a portable computed tomography (CT) scanner for critically ill adult patients in an intensive care unit (ICU). DESIGN: Survey study and retrospective review. SUBJECTS: Critical care attending staff and fellows and neurosurgery residents. SETTING: A university hospital and Level I trauma center with a multitrauma ICU, a neurotrauma ICU, and a neurosurgical ICU. INTERVENTIONS: We surveyed all physicians who ordered portable CT scans from December 1996 through June 1998. Ordering physicians included critical care attending staff and fellows (anesthesiology, surgery, internal medicine) and neurosurgery residents. Physicians who no longer worked at the institution were contacted by mail or fax. Radiology records were reviewed to determine the actual number and type of scans performed. MEASUREMENTS AND MAIN RESULTS: The survey response was 100%. Most physicians reported ordering portable head CT scans (97%), followed by chest CT (88%), abdominal CT (78%), and pelvic CT (34%) scans. Analysis of the actual number of scans performed correlated with these reports (511 head, 115 chest, 88 abdomen, and 87 pelvis). The indication for portable CT scans (as opposed to a "fixed" or "stationary" scans) cited most often was patient severity of illness (77%). Patients on extracorporeal support (93%), those with cardiovascular instability (70%), followed by those with respiratory instability (57%) and neurologic instability (40%) were deemed too ill to transport. If the portable CT scanner was unavailable, however, most physicians (67%) ordered a fixed helical CT scan and the patient was transported to the radiology suite, regardless of medical condition. CONCLUSIONS: Access to a portable CT scanner impacts the physician ordering patterns for ICU patients. We found that 100% of surveyed physicians used the portable CT scanner for critically ill patients when the patient was unstable. If the diagnostic study was deemed medically necessary, and the portable scanner was unavailable, most surveyed physicians ordered a "fixed" helical scan and the patient was transported by an experienced transport team for the study. The portable CT offered an alternative and potentially safer means of obtaining diagnostic studies.     

The diagnostic and prognostic value of the optic nerve sheath diameter on CT for diagnosis spontaneous subarachnoid hemorrhage

Introduction

The aim of this study was to investigate the relationship between the optic nerve sheath diameter (ONSD) measured on non-contrast head computed tomography (CT) and the diagnosis and prognosis of spontaneous subarachnoid hemorrhage (SAH) on emergency department (ED) patients.

Documentation of cerebrospinal fluid opening pressure and other important aspects of lumbar puncture in acute headache

Background: Measuring cerebrospinal fluid (CSF) opening pressure by lumbar puncture (LP) is an essential tool in the investigation of patients with acute headache. Aim: To assess documentation of opening CSF pressure in those with acute headache undergoing LP. General documentation of the procedure and CSF investigations was also assessed. Methods: Retrospective review of medical records of patients admitted to a teaching hospital Acute Medical Admissions Unit over a three‐month period with a presenting complaint of headache. Results: A total of 106 patients presented with headache of whom 48 patients had at least one LP attempted. Only 41 patients (85%, 95% CI 72–94) had their LP documented. Of 47 patients that had a successful LP, 22 (47%) had a recorded opening pressure. Eighteen (32%) of all patients had their position recorded, with seven (15%) patients having had position and opening pressure documented. Twenty patients (43%) had the appropriate results documented. Twelve patients (31%) had paired serum glucose measured. Conclusions: Documentation of a LP for headache in the acute setting was generally poor. CSF opening pressure measurement was frequently omitted and no appropriate action taken if high. Paired serum glucose was rarely measured. Acute physicians may benefit from a proposed protocol and documentation sticker.     

Findings of Chronic Sinusitis on Brain Computed Tomography Are Not Associated with Acute Headaches

Background

Headache is a common complaint in emergency department (ED) patients. Nearly 15% of ED headache patients will have brain computed tomography (CT) done. One frequent finding on these scans is “chronic sinusitis.” Assuming that “chronic sinusitis” is the cause of the patient's headache is a potential source of mis-diagnosis.

Study Objective

We hypothesized that CT findings of chronic sinusitis occur with equal frequency in patients with atraumatic headache as in control patients with minor head injury.

Methods

This is a retrospective, single-center medical record review of consecutive discharged patients who received noncontrast head CT scans in an urban ED for either minor closed head injury or atraumatic headache. Each patient's head CT radiologic report was reviewed for findings of sinusitis and classified as chronic sinusitis, indeterminate for sinusitis, air-fluid levels, or no findings of sinusitis.

Results

We enrolled 500 patients (234 in the atraumatic headache group, 266 in the minor head injury group). The two groups were similar except that more women were enrolled in the atraumatic headache group. CT findings of chronic sinusitis in the atraumatic headache group (22.2%) and the minor head injury group (17.7%; difference 4.5%; 95% confidence interval of −2.5–11.6%).

Conclusion

Prevalence of CT findings of sinusitis in ED patients with atraumatic headaches and mild head injury are similar. This strongly suggests that CT findings of chronic sinusitis in patients with atraumatic headache may be incidental, and are rarely the cause of a patient's acute headache.     

The role of lumbar puncture in the diagnosis of subarachnoid hemorrhage when computed tomography is unavailable

Subarachnoid hemorrhage (SAH) is an important but uncommon condition in the differential diagnosis of acute headache. Most authorities recommend that patients with suspected SAH undergo noncontrast computed tomography (CT) as a first diagnostic intervention. If the results of the CT scan are negative, a lumbar puncture should be performed. Many nonurban Canadian hospitals do not have CT scanners and must either transfer patients or consider performing lumbar puncture prior to CT. In selected patients, performing lumbar puncture first may be an option, but timing of the procedure and the interpretation of results is important.     

Subarachnoid Hemorrhage Diagnosis: Lumbar Puncture Is Still Needed When the Computed Tomography Scan Is Normal

Objectives: To determine the sensitivity of third-generation CT scanners for diagnosed nontraumatic subarachnoid hemorrhage (SAH) and to assess the impact of symptom duration on sensitivity.
Methods: A retrospective chart review was performed in a university-affiliated tertiary care hospital with an annual ED volume of >100,000 patients. The target population was all patients who presented to the ED from January 1991 to September 1994 with symptoms suggestive of SAH and who had a final diagnosis of nontraumatic SAH based on either a positive CT scan or positive spinal fluid analysis. Patients referred from outside facilities were included if they had a CT done at the study site. All CT scans were done using third-generation scanners. Official CT scan reports were used to categorize scans as positive or negative.
Results: There were 140 patients identified with SAH, with a mean age of 56 years (range 10–88). The sensitivity of CT in the diagnosis of nontraumatic SAH when performed at or before 12 hours of symptom duration was 100% (80/80), and 81.7% (49/60) after 12 hours of symptom duration (95% CI 95–100% and 69.5–90.4%, respectively; p < 0.0001). Eleven of the 140 patients had a negative CT and positive spinal fluid analysis, yielding an overall sensitivity of 92.1% (129/140).
Conclusion: The sensitivity of third-generation CT scans for SAH decreases with time from the onset of symptoms. In this sample population, CT was able to detect all patients scanned ^12 hours after symptom onset. Although the study demonstrated good sensitivity of CT scan reports for SAH when the scan was performed after S12 hours of symptom onset, additional real-time experience is needed to better define the potential risk of a missed SAH should this population not receive the customary lumbar puncture examination in the setting of a negative CT scan.     

Prospective analysis of the effect of physician experience with the FAST examination in reducing the use of CT scans

Objective: The objective of this study was to examine the effect of ultrasound experience level on emergency physicians’ Focused Assessment with Sonography for Trauma (FAST) exam accuracy and emergency physicians’ confidence in using FAST findings to assist in managing patients with blunt trauma. Methods: This prospective, consecutive enrolment study evaluated adult trauma team activation blunt trauma patients. Based on the number of post‐training FAST exams carried out, 11 attending emergency physicians were grouped into A (<25 exams, n = 4), B (26–50 exams, n = 4) or C (>50 exams, n = 3). The FAST exam was carried out prior to other diagnostic studies. The emergency physicians were asked to prospectively judge their perception of the need for surgery, abdominal CT or no further tests. All study patients ultimately underwent CT, diagnostic peritoneal lavage or laparotomy. Among each physician group, the number of subsequent CT scans deemed necessary by the emergency physician after a ‘normal’ FAST was calculated and compared. Results: Accuracy was greatest in group C. Sixty‐nine of 80 patients in group A had a normal FAST exam; emergency physicians deemed CT necessary in 68/69 cases (99%; confidence interval [CI] 92–100%). Eighty‐two of 98 patients in group C had a normal FAST exam; emergency physicians deemed CT necessary in 19/82 cases (23%; CI 15–34%). Physicians in groups B and C were less likely to order CT after a normal FAST than group A (P < 0.001). Conclusions: FAST accuracy was greatest among more experienced emergency physicians. A normal FAST exam assisted more experienced emergency physicians with the perceived need to order significantly fewer CT scans than less experienced emergency physicians.