CSF spectrophotometry in the diagnosis and exclusion of spontaneous subarachnoid haemorrhage

Subarachnoid haemorrhage or traumatic lumbar puncture. Differentiation by cerebrospinal fluid parameters in a multivariable approach

Lumbar puncture (LP) is recommended in patients with thunderclap headache and negative computed tomography to rule out spontaneous subarachnoid haemorrhage (SAH). Blood contamination of cerebrospinal fluid (CSF) due to traumatic LP poses a diagnostic dilemma. Therefore, routine CSF parameters were investigated to distinguish between SAH and a traumatic LP. CSF red blood cell (RBC), white blood cell (WBC) count, total protein, CSF colour and supernatant were used for group comparisons of patients with SAH and 'symptomatic controls'. Due to variable time intervals between bleeding onset and LP in SAH patients in contrast to patients with traumatic LP, where blood contamination of CSF occurs at the time of LP, CSF variables were adjusted for decay in time to allow comparability. Logistic regression analysis identified bloody CSF [odds ratio (OR) 32.6], xanthochromic supernatant [OR 15.5] and WBCadjusted [OR 4.5 (per increase of 100/µl)] as predictors of SAH, while age, sex and CSF total proteinadjusted were no predictors. Optimal cut-point of RBCadjusted (determined at day 1 after bleeding) was > 3667/µl to identify SAH patients with a 97% sensitivity and 94% specificity. Combination of low RBC and clear CSF supernatant was found in none of SAH patients. Combined CSF RBC count and CSF supernatant reliably distinguished traumatic LP from SAH.

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.

Recapitulating the Bayesian framework for neurosurgical outpatient care and a cost-benefit analysis of telemedicine for socioeconomically disadvantaged patients in the Philippines during the pandemic

OBJECTIVE

In the Philippines during recent months, a neurosurgical center that caters primarily to socioeconomically disadvantaged patients has encountered unprecedented changes in practice patterns brought about by the COVID-19 pandemic. In particular, the usual task of outpatient care has shifted to the telemedicine format, bringing along all of its attendant advantages and gargantuan challenges. The authors sought to determine the responsiveness of this telemedicine setup to the needs of their disadvantaged patients and explored the application of Bayesian inference to enhance the use of teleconsultation in daily clinical decision-making.

METHODS

The authors used the following methods to assess the telemedicine setup used in a low-resource setting during the pandemic: 1) a cross-sectional survey of patients who participated in a medical consultation via telemedicine during the 16-week period from March 16, 2020, to July 15, 2020; 2) a cost-benefit analysis of the use of telemedicine by patients; and 3) a case illustration of a Bayesian approach application unique to the teleconsultation scenario.

RESULTS

Of the 272 patient beneficiaries of telemedicine in a 16-week period, 57 responded to the survey. The survey responses regarding neurosurgical outpatient care through telemedicine yielded high ratings of utility for the patients and their caregivers. According to 64% of respondents, the affordability of the telemedicine setup also prevented them from borrowing money from others, among other adverse life events prevented. There were realized financial gains on the part of the patients in terms of cost savings and protection from further impoverishment. The benefit-cost ratio was 3.51 for the patients, signifying that the benefits outweighed the costs. An actual teleconsultation case vignette was reported that is meant to be instructive and contributory to the preparedness of the neurosurgeon on the provider end of the service delivery.

CONCLUSIONS

Telemedicine holds promise as a viable and safe method for health service delivery during the pandemic. In the setting of a health system that is continually challenged by shortages of resources, this study shows that an effective telemedicine setup can come with high benefit-cost ratios and quality of care, along with the assurance of patient satisfaction. The potential for high-quality care can be enhanced by the inclusion of the Bayesian framework to the basic toolkit of remote clinical assessment. When confronted with choices in terms of differential diagnosis and tests, the rigor of a simple application of the Bayesian framework can minimize costs arising from uncertainties.

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.

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.

Other primary headaches-thunderclap-, cough-, exertional-, and sexual headache

This article reviews the disorders of thunderclap, cough, exertional and sexual headache. These are a group of paroxysmal and precipitated headaches, which often occur in bouts with prolonged remissions. Indometacin seems to be the most effective preventative. Each can occur in primary and secondary form. Thunderclap headache is the most frequently reported headache syndrome associated with a secondary pathology. Discussed are the complexities of whether all patients with thunderclap headache should have further investigation if timely computerised tomography is normal and, the relevance of abnormal imaging in these disorders, differentiating what is deemed to be secondary and managing the pain.

Analysis of blood degradation products and ferritin in the cerebrospinal fluid of dogs with acute thoracolumbar intervertebral disk extrusion, a prospective pilot study

Background

Hemorrhage in the spinal canal leads to further damage of the spinal cord influencing outcome in dogs with intervertebral disk (IVD) extrusion. The aim of the study was to evaluate blood degradation products and ferritin in the cerebrospinal fluid (CSF) of dogs with thoracolumbar IVD extrusion, and their association to clinical parameters and MRI findings.

Results

In the CSF of dogs with IVD extrusion, both net oxyhemoglobin absorption (NOA) and net bilirubin absorption (NBA) were significantly higher compared to the control groups of dogs with steroid responsive meningitis arteritis (SRMA) and idiopathic epilepsy (IE) (P < 0.001), but NOA compared to the idiopathic epilepsy group contaminated artificially with blood (IEc) was not (P = 0.890). Ferritin concentration was significantly higher in dogs with IVD extrusion compared to dogs with IE (P = 0.034), but not to dogs with SRMA (P = 0.526). There was no association between NOA, NBA or ferritin concentration and severity or duration of clinical signs. In dogs with a higher ferritin concentration the outcome was better (P = 0.018). In dogs with evidence of hemorrhage on MRI, NOA and NBA were significantly higher (P = 0.016, P = 0.009), but not ferritin (P = 0.0628).

Conclusion and clinical importance

Quantification of blood degradation products and ferritin in the CSF of dogs to assess subarachnoidal hemorrhage is feasible; however, larger case numbers are needed to evaluate the relevance of NBA and ferritin as prognostic indicators.

Vascular diseases and bleedings

Diseases of the central nervous system that are caused by an underlying vascular pathology typically result in either hemorrhage or ischemia. Most prominent entities include spontaneous subarachnoid hemorrhage, spontaneous intracerebral hemorrhage, and ischemic stroke. For anatomic reasons, cerebrospinal fluid (CSF) qualifies as body fluid for the exploration of biomarkers in these disorders. Even though in subarachnoid hemorrhage a few CSF parameters have been established for routine diagnostic purposes, there is still an unmet need and broad interest in the identification of molecules that would allow further insight into disease mechanisms and supplement patients' medical care. This chapter provides an overview on what is presently known about CSF biomarkers in spontaneous subarachnoid hemorrhage, spontaneous intracerebral hemorrhage, and ischemic stroke. We recapitulate current evidence on established diagnostic tests, discuss the role of various CSF molecules in the pathophysiology of these diseases, and illuminate their potential use in future clinical practice. Furthermore, we address methodologic aspects as well as shortcomings of research in this field.

Thunderclap Headache

PURPOSE OF REVIEW

A thunderclap headache is a very severe headache that reaches its maximum intensity within 1 minute. Patients with thunderclap headache must be evaluated emergently and comprehensively to rule out underlying disorders that can be associated with high mortality and morbidity, determine the cause for the thunderclap headache, and initiate targeted therapy. This review presents an up-to-date summary on the clinical presentation, diagnostic evaluation, and causes of thunderclap headache.

RECENT FINDINGS

Numerous etiologies for thunderclap headaches have been identified, with the most common causes being subarachnoid hemorrhage and reversible cerebral vasoconstriction syndrome. Other relatively common causes include cervical artery dissection, cerebral venous sinus thrombosis, and spontaneous intracranial hypotension. Although "primary" thunderclap headache is typically accepted to exist, it may be that such cases represent missed diagnoses of underlying causes. The urgent evaluation of the patient with thunderclap headache includes brain CT, followed by lumbar puncture if the brain CT is nondiagnostic. If a diagnosis is not reached following brain CT and lumbar puncture, brain MRI and imaging of the brain and cervical vasculature are indicated.

SUMMARY

Patients with thunderclap headache require an emergent and comprehensive evaluation to identify the underlying cause and to initiate appropriate therapy.

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.

Controversies in the Diagnosis of Subarachnoid Hemorrhage

BACKGROUND

Headache is a common chief complaint in emergency departments, accounting for 2% of visits, and subarachnoid hemorrhage (SAH) is a life-threating cause of headache. This deadly disease is most commonly due to aneurysmal rupture. Various approaches exist for diagnosis, with recent studies evaluating these approaches. A great deal of controversy exists about the optimal diagnosis strategy for SAH.

OBJECTIVE

This article in the Best Clinical Practice Series seeks to educate emergency physicians on the recent literature in the diagnosis of SAH and provide an evidence-based approach.

DISCUSSION

Various diagnostic strategies exist, including use of noncontrast head computed tomography (CT) alone, CT/lumbar puncture (LP) in combination, CT/CT angiography, and magnetic resonance imaging/magnetic resonance angiography. The use of clinical decision rules has also been espoused, and several contemporary studies have evaluated cerebrospinal fluid results of red blood cell count and xanthochromia in the diagnosis of SAH. Recent literature supports that a negative head CT done within 6 h of headache onset places the patient at a < 1% risk for SAH. With the complex literature, a shared decision-making model should be followed with options, risks, and benefits discussed with the patient.

CONCLUSIONS

Literature support exists for all of the diagnostic strategies. The American College of Emergency Physicians Clinical Policy supports CT and LP for definitive diagnosis. Risk stratification and a shared decision-making model with the patient should be followed, and a negative head CT within 6 h of headache onset places patient at a risk of < 1% for having SAH.

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.

Pseudosubarachnoid hemorrhage in a 42-year-old male with meningitis

Pseudosubarachnoid hemorrhage is the appearance of subarachnoid hemorrhage on CT imaging with no source of blood found on further evaluation, including lumbar puncture and autopsy. The mechanism leading to this finding is poorly understood, and clinicians should consider this finding in the right clinical setting, such as cryptococcal meningitis. We present a case of an immunocompromised patient found to have a pseudosubarachnoid hemorrhage.

Recognizing the signs and symptoms of aneurysmal subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating neurologic condition with a high mortality and long term neurological morbidity in 50% of survivors. In addition, SAH commonly affects young patients causing substantial loss of productive life years and resulting in significant long term healthcare costs. Early recognition of the signs and symptoms of SAH is absolutely critical to earlier intervention, and delays in diagnosis can have devastating consequences. To avoid such delays in SAH diagnosis, the medical provider should recognize its signs and symptoms. Neuroimgaging, cerebrospinal fluid examination and angiography (invasive or non-invasive) facilitate early diagnosis of SAH. The purpose of this review is not to provide an exhaustive critique of the available literature, rather, it is to provide an overview that will better enable a provider to recognize and initiate the workup of patients with SAH.

Benefit of cerebrospinal fluid spectrophotometry in the assessment of CT scan negative suspected subarachnoid haemorrhage: a diagnostic accuracy study

This study aimed to determine if performing cerebrospinal fluid spectrophotometry in addition to visual inspection detects more ruptured cerebral aneurysms than performing cerebrospinal fluid visual inspection alone in patients with a normal head CT scan but suspected of suffering an aneurysmal subarachnoid haemorrhage (SAH). We performed a single-centre retrospective study of patients presenting to the emergency department of a tertiary hospital who underwent both head CT scan and lumbar puncture to exclude SAH. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of an approach utilising both spectrophotometry and visual inspection (combined approach) was compared to visual inspection alone. A total of 409 patients (mean age 37.8 years, 56.2% female) were recruited and six (1.5%) had a cerebral aneurysm on angiography. The sensitivity of visual inspection was 50% (95% confidence interval [CI]: 12.4-82.6%), specificity was 99% (95% CI: 97.5-99.7%), PPV was 42.9% (95% CI: 10.4-81.3%) and NPV was 99.2% (95% CI: 97.8-99.8%). The combined approach had a sensitivity of 100% (95% CI: 54.1-100%), specificity of 79.7% (95% CI: 75.4-83.5%), PPV of 6.8% (95% CI: 2.6-14.3%) and a NPV of 100% (95% CI: 98.8-100%). The sensitivity of the combined approach was not significantly different to that of visual inspection alone (p=0.25). Visual inspection had a significantly higher specificity than the combined approach (p<0.01). The combined approach detected more cases of aneurysmal SAH than visual inspection alone, however the difference in sensitivity was not statistically significant. Visual xanthochromia should prompt angiography because of a superior specificity and PPV. Due to its reduced sensitivity, caution should be applied when using only visual inspection of the supernatant.

CSF xanthochromia: correlation with brain imaging and its usefulness as an out-of-hours test

BACKGROUND

Subarachnoid haemorrhage (SAH) is a spontaneous bleed into the subarachnoid space which is investigated by CT head and cerebrospinal fluid (CSF) xanthochromia. The aim of this study was to compare CSF xanthochromia with brain imaging and evaluate the need for out of hours (OOH) testing for CSF xanthochromia.

METHOD

Discharge summaries and brain imaging of patients with positive xanthochromia screen were reviewed over 12 months retrospectively. Timings of CSF xanthochromia and hospital discharge of 30 consecutive patients with negative xanthochromia screen were also examined.

RESULTS

From 289 xanthochromia requests, 23 were positive but only 2 patients had an actual bleed. In 30 consecutive negative xanthochromia results, all brain imaging results suggested no bleed. Eight of these requests were performed OOH, and as a result, 1 patient was discharged early.

CONCLUSIONS

CSF xanthochromia has a poor positive predictive value (8.7%) but has a good negative predictive value (100%) for SAH. Analysis of CSF xanthochromia OOH, in patients with negative CT head, did not speed up the discharge process from the hospital.

Diagnostic Yield of Cerebral Angiography in Patients With Computed Tomography-Negative, Lumbar Puncture-Positive Subarachnoid Hemorrhage

BACKGROUND:

Cerebral angiography is generally recommended in patients with subarachnoid hemorrhage (SAH) by positive lumbar puncture (LP) but negative findings on computed tomography (CT). Existing data on the yield of angiography in these patients are very limited.

OBJECTIVE:

To retrospectively assess the diagnostic yield of cerebral angiography in patients with CT−/LP+ SAH and to determine the clinical and laboratory predictors of a vascular abnormality on angiography.

METHODS:

A total of 35 patients with CT−/LP+ SAH underwent cerebral angiography at our institution between 2008 and 2011. Patient clinical characteristics and LP findings were entered into a multivariate logistic regression analysis to identify predictors of vascular abnormalities.

RESULTS:

Twenty-five patients (71.4%) were female and 10 (28.6%) were male, with a mean age of 53 years. Twenty-six patients (74.3%) had cerebrospinal fluid xanthochromia. Sixteen patients (45.7%) were found to have an aneurysm on cerebral angiography. The median CSF red blood cell count of both the first (7790/mm3 vs 4700/mm3), and last collection tubes (6800/mm3 vs 3219/mm3) were higher in patients with cerebral aneurysms vs those without aneurysms (P = .3). On multivariate analysis, there were no clinical or laboratory parameters that predicted the presence of aneurysm on cerebral angiography.

CONCLUSION:

The diagnostic yield of cerebral angiography is high (45.7%) in patients with CT−/LP+ SAH. Higher red blood cell counts were noted in patients with cerebral aneurysms but no clinical or laboratory parameter can reliably predict the presence of a vascular anomaly. Thus, it is reasonable to perform cerebral angiography in all patients with CT−/LP+ SAH.

Intracranial hemorrhage

Intracranial hemorrhage refers to any bleeding within the intracranial vault, including the brain parenchyma and surrounding meningeal spaces. This article focuses on the acute diagnosis and management of primary nontraumatic intracerebral hemorrhage and subarachnoid hemorrhage in the emergency department.

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.

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.

Spectrophotometry for cerebrospinal fluid pigment analysis

The use of spectrophotometry for the analysis of the cerebrospinal fluid (CSF) is reviewed. The clinically relevant CSF pigments--oxyhemoglobin and bilirubin--are introduced and discussed with regard to clinical differential diagnosis and potentially confounding variables (the four T's: traumatic tap, timing, total protein, and total bilirubin). The practical laboratory aspects of spectrophotometry and automated techniques are presented in the context of analytical and clinical specificity and sensitivity. The perceptual limitations of human color vision are highlighted and the use of visual assessment of the CSF is discouraged in light of recent evidence from a national audit in the United Kingdom. Finally, future perspectives including the need for longitudinal CSF profiling and routine spectrophotometric calibration are outlined.

Anévrysmes intracrâniens révélés par une ischémie cérébrale

PURPOSE

To report four cases of patient with an acute ischemic event as a presenting symptom of a berry aneurysm.

PATIENTS AND METHODS

One male and three female (aged range 38 to 65 years) patients were admitted for acute stroke. The neuroradiologic finding disclosed aneurysm thrombosis, inferior to twenty five millimetres in three cases. Lumbar puncture was done in one case and showed subarachnoid haemorrage.

DISCUSSION

We will discuss the hypothesis leading to the mechanism of aneurysm thrombosis. Two theories will be presented: "hemodynamic" and "parietal" modifications. We will propose a management protocol for these patients with atypical presentation of intracranial aneurysms given the potential risk of rupture.

CONCLUSION

The natural history of intracranial aneurysms is still not fully understood. Nevertheless, aneurym thrombosis may occur and lead to ischemic stroke.