What is the role of CSF spectrophotometry in the diagnosis of subarachnoid haemorrhage?

Subarachnoid hemorrhage in ten questions

Traumatic subarachnoid hemorrhage (SAH) has an annual incidence of 9 per 100 000 people. It is a rare but serious event, with an estimated mortality rate of 40% within the first 48hours. In 85% of cases, it is due to rupture of an intracranial aneurysm. In the early phase, during the first 24hours, cerebral CT, combined with intracranial CT angiography is recommended to make a positive diagnosis of SAH, to identify the cause and to investigate for an intracranial aneurysm. Cerebral MRI may be proposed if the patient's clinical condition allows it. FLAIR imaging is more sensitive than CT to demonstrate a subarachnoid hemorrhage and offers greater degrees of sensitivity for the diagnosis of restricted subarachnoid hemorrhage in cortical sulcus. A lumbar puncture should be performed if these investigations are normal while clinical suspicion is high.

The UKNEQAS scheme for cerebrospinal fluid haem pigments: a paradigm for service improvement

We describe the programme of an established External Quality Assurance (EQA) provider and a Specialist Advisory Group (SAG) to develop a successful EQA scheme for cerebrospinal fluid (CSF) haem pigments as an example of a professionally led, unfunded initiative with the real potential to benefit patients.

Within three years, we had assured sample stability, stoichiometry, and published best practice guidelines, enabling both analytical results and interpretation to be assessed and reported with an educative summary of the desired responses. Misclassification scoring of analysis and interpretation was introduced. Following audit, guidelines were modified and republished. The outcomes were as follows: Participant numbers increased from 63 at inception to 150 10 years later; The percentage of participants using visual inspection, a poor practice indicator, decreased from 27% to less than 1%; In all, 94–100% of participants consistently detected minor increases in bilirubin over the last four years of the scheme; More than 93% of participants were able to interpret analytical results linked to straightforward clinical scenarios; Misclassification scoring demonstrated that more complex scenarios repeatedly posed problems and is the next challenge to address. Scheme success is attributed to the experience of the operator and the formation of a voluntary expert advisory group, with both concerned to advance science and patient safety and thus contribute unpaid time and effort in order to succeed. In times of fiscal constraint, such resource may not be so readily available, yet is a vital part of continuous quality improvement for the benefit of patients.

[Cerebrospinal fluid-based diagnostics of CT-negative subarachnoid haemorrhage]

The diagnostic investigation of CT-negative subarachnoid haemorrhage (SAH) is a particular challenge in clinical neurology. Cerebrospinal fluid (CSF) analysis via lumbar puncture is the method of choice. The diagnosis of SAH in CSF is based on a bloody or xanthochromic discoloration of the CSF as well as on findings in non-automated CSF cytology including the detection of erythrophages and siderophages. The automated determination of CSF ferritin concentrations or spectrophotometric detection of xanthochromia may contribute to the diagnosis but are only useful with regard to the overall clinical picture. Generally, the knowledge of the time flow of CSF changes associated with SAH is essential for a correct interpretation of CSF findings.

Primary thunderclap headache

Thunderclap headache is an uncommon type of headache, but recognition and diagnosis are important because of the possibility of a serious underlying brain disorder. In this chapter, primary thunderclap headache in relation to other primary headache disorders and secondary, symptomatic headache disorders are discussed. Most importantly, subarachnoid hemorrhage should be excluded. The first investigation is a computed tomography (CT) scan, and, if the CT scan is negative, investigation of the cerebrospinal fluid. Other symptomatic vascular causes are intracranial hemorrhage, cerebral venous sinus thrombosis, cervical artery dissection, or a reversible vasoconstriction syndrome. These and other serious underlying intracranial disorders should be detected by magnetic resonance imaging or the appropriate investigations. The remaining patients with thunderclap headache most likely represent a primary headache disorder, including migraine, primary cough headache, primary exertional headache, or primary headache associated with sexual activity. Within the group of primary headache disorders, primary thunderclap headache represents a distinct clinical entity; it is characterized by a sudden severe headache lasting from 1h up to 10 days and not attributed to another disorder. The pathogenesis of primary thunderclap headache is still not known, but the sympathetic nervous system may play an important role.

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.

Is Cerebrospinal Fluid Spectrophotometry Useful in CT Scan-Negative Suspected Subarachnoid Haemorrage?

Missed cerebral aneurysms in CT-negative patients can have serious implications. We set out to determine the usefulness of cerebrospinal fluid (CSF) spectrophotometry and the individual significance of CSF oxyhaemoglobin, bilirubin and methaemoglobin in 463 CT scan-negative patients with suspected subarachnoid haemorrhage (SAH) and normal neurological examination. CSF spectrophotometry resulted in the diagnosis of an intracranial aneurysm in 2% (9/463) of patients with CT-negative suspected SAH. No aneurysms were found in patients in whom spectrophotometry was negative for haem pigments. Less than 1% of patients with oxyhaemoglobin alone had aneurysms diagnosed, whilst 21% of patients with bilirubin had an aneurysm. CSF spectrophotometry is an important investigation in patients with CT-negative suspected SAH, particularly where clinical suspicion is strong. Patients positive for bilirubin are likely to provide a high yield of aneurysmal bleed and should undergo angiography. Patients with oxyhaemoglobin alone in whom SAH is strongly suspected may benefit from angiography. Based on a small number of patients, we recommend that patients with methaemoglobin should also be investigated. Patients with negative spectrophotometry are unlikely to benefit from further investigation.

Distinguishing traumatic lumbar puncture from true subarachnoid hemorrhage

The lumbar puncture (LP) is a relatively simple diagnostic test. However, significant diagnostic ambiguity can arise when trauma from the needle causes bleeding into the subarachnoid space, especially when trying to make the diagnosis of subarachnoid hemorrhage (SAH). The purpose of this article is to assist emergency physicians in distinguishing traumatic LPs from SAH. To correctly interpret the findings of a traumatic tap, a few concepts must be understood. Timing of the LP in relation to the onset of the SAH affects the results of the cerebrospinal fluid (CFS) analysis; the typical findings will change with time. With a few caveats, xanthochromia, the yellow discoloration of the CSF resulting from hemoglobin catabolism, is often critical in making a diagnosis of SAH. A few of the most essential methods for distinguishing traumatic LP from true SAH include: the "three tube test," opening pressure, and inspection for visual xanthochromia.

How valuable is a lumbar puncture in the management of patients with suspected subarachnoid haemorrhage?

OBJECTIVE

The aim of the study was to determine the range of cerebrospinal fluid findings associated with emergency department disposition and treatment of patients with headache suspicious of subarachnoid haemorrhage but a negative or equivocal computed tomography head scan, in particular the role of xanthochromic index.

METHODS

A retrospective review of medical records of 196 adult patients who underwent cerebrospinal fluid examination for red cell count and xanthochromia for suspected subarachnoid haemorrhage but had a normal or equivocal computed tomography scan.

RESULTS

Included in the study were 196 patients. Only one patient out of 189 with a negative computed tomography scan was found to have a subarachnoid haemorrhage caused by a ruptured aneurysm (0.5%; 95% confidence intervals 0-2.9%). Three other patients were diagnosed with benign subarachnoid haemorrhage. Ninety-one patients were stratified into the lowest possible risk group for subarachnoid haemorrhage and discharged home from the emergency department. All patients with equivocal computed tomography head scans and a positive xanthochromic index were admitted for cerebral angiography. In many cases, cerebrospinal fluid findings did not appear to influence clinical decision-making.

CONCLUSIONS

In the study institution, cerebrospinal fluid results appeared to have a variable influence on clinical decision-making for patients with suspected subarachnoid haemorrhage and a non-diagnostic computed tomography head scan. Of particular concern is the lack of validation of the tests used in this investigative approach, the frequency of patients having a lumbar puncture where the results did not influence their management, the inconsistency in the laboratory's technique for performing tests on cerebrospinal fluid and the very low yield of detecting patients with subarachnoid haemorrhage and a potentially treatable causative lesion.

Diagnostic testing for headache

A careful and complete headache history supplemented by a neurologic and general physical examination, as appropriate, enables the astute physician to diagnose most headaches correctly without diagnostic testing. When indications are present (see Box 1), some headache patients with a normal physical examination require testing even though the yield may be low. Failure to test may result in misdiagnosis of potentially serious and life-threatening causes of headaches, such as brain tumors, chronic meningitis, SAH, and temporal arteritis.

Subarachnoid haemorrhage: diagnosis, causes and management

The incidence of subarachnoid haemorrhage (SAH) is stable, at around six cases per 100 000 patient years. Any apparent decrease is attributable to a higher rate of CT scanning, by which other haemorrhagic conditions are excluded. Most patients are <60 years of age. Risk factors are the same as for stroke in general; genetic factors operate in only a minority. Case fatality is approximately 50% overall (including pre-hospital deaths) and one-third of survivors remain dependent. Sudden, explosive headache is a cardinal but non-specific feature in the diagnosis of SAH: in general practice, the cause is innocuous in nine out of 10 patients in whom this is the only symptom. CT scanning is mandatory in all, to be followed by (delayed) lumbar puncture if CT is negative. The cause of SAH is a ruptured aneurysm in 85% of cases, non-aneurysmal perimesencephalic haemorrhage (with excellent prognosis) in 10%, and a variety of rare conditions in 5%. Catheter angiography for detecting aneurysms is gradually being replaced by CT angiography. A poor clinical condition on admission may be caused by a remediable complication of the initial bleed or a recurrent haemorrhage in the form of intracranial haematoma, acute hydrocephalus or global brain ischaemia. Occlusion of the aneurysm effectively prevents rebleeding, but there is a dearth of controlled trials assessing the relative benefits of early operation (within 3 days) versus late operation (day 10-12), or that of endovascular treatment versus any operation. Antifibrinolytic drugs reduce the risk of rebleeding, but do not improve overall outcome. Measures of proven value in decreasing the risk of delayed cerebral ischaemia are a liberal supply of fluids, avoidance of antihypertensive drugs and administration of nimodipine. Once ischaemia has occurred, treatment regimens such as a combination of induced hypertension and hypervolaemia, or transluminal angioplasty, are plausible, but of unproven benefit.