Morbidity and Mortality Rounds

Subarachnoid HemorrhageDiagnostic Challenges in the ED

Neil Collins

47 y.o. maleDay 8 of headachePLC ED

Mr. K.T.

ED VISIT SAH

state of wellness Rehabilitation

Headache

May 1 9 15

History

History

• Features of headache at onset

History

• Features of headache at onset– Sudden– Severe– Ongoing pain

History

• Associated features– No neck pain, photophobia, neuro symptoms

Physical Exam

• BP 138/98, afebrile• Neuro “normal”• Neck supple• GCS 15/15

Lab

• CBC, lytes, Cr., Gluc all normal

Lumbar Puncture

• 2000 hrs– RBC 1045 X106/L– WBC 1.7 X106/L– Xanthochromia negative– Protein 0.60 (0.15 – 0.45)– Glucose normal

NEXT STEPS?

Repeat LP

• 2300 hrs• RBC #1 1308• RBC #4 878

• 2000 hrs• RBC #1 954• RBC #4 1045

NEXT STEPS?

Objectives

• Explore the significance of SAH in the context of headache presentations to the ED

• Understand the principles of the diagnosis of SAH – role of advanced imaging and lumbar puncture

Epidemiology

• 100 per year in Calgary• 50% mortality

Pathophysiology

• Aneurysmal 85%• Perimesencephalic bleeding 10%

(a) Preoperative digital subtraction angiographic (DSA) three-dimensional reformation of wide-necked basilar tip aneurysm.

Tähtinen O I et al. Radiology 2009;253:199-208

©2009 by Radiological Society of North America

Scope of the Problem

• HA comprises 1% of ED visits• Benign HA is 50 times more common than SAH1% of all headaches = SAH

10% of all “thunderclap headaches” = SAH

“Cannot Miss” Headaches• SAH• Cervico-cranial Artery Dissections• Temporal Arteritis• Acute narrow Angle Closure Glaucoma• Hypertensive Emergencies• CO poisoning• Meningitis encephalitis• Dural Sinus Thrombosis• Hemorrhagic Stroke• ?Mass Lesions

Cognitive Errors

• Diagnostic Momentum/Anchoring• Outcome Bias• Feedback Sanction• Overconfidence Bias• Frequency Bias

Diagnosis of SAH

• Physicians Consistently Misdiagnose SAH

• Patients with the greatest likelihood of benefitting from surgery are the ones who most often receive an incorrect diagnosis

Reasons For Misdiagnosis

• Failure to know the spectrum of presentations of SAH

• Failure to understand the limitations of CT• Failure to perform an LP• Failure to interpret CSF results correctly

Reasons For Misdiagnosis

• Failure to know the spectrum of presentations of SAH

• Failure to understand the limitations of CT• Failure to perform an LP• Failure to interpret CSF results correctly

Classic Presentation

• Abrupt onset of severe unique exertional headache/neck pain with meningismus and altered LOC

• Neurologic abnormalities– Third nerve palsy– Seizure– Motor deficit

Other Clinical Presentations

• Less obvious scenarios– Acute confusional state– New seizure– Trauma with subarachnoid blood– Altered LOC and ECG changes

Neurologically Intact Patient With Sentinel Bleed

• 20 – 50 % of patients report a distinct unusually severe headache in the days or weeks preceding the index episode of SAH

Clinical Features

• Sudden Onset (Thunderclap)

Differential Diagnosis of TCH

• SAH• Benign Cough Headache• Intracerebral Hemorrhage• Dissection• Sinus Thrombosis• Reversible vasospasm• Sexual Activity Headache

Prospective study of TCHResults for the SAH cohort

Timing of Onset

Almost instantaneous 50%

2 – 60 seconds 24%

1- 5 minutes 19%

Prospective Study of TCH

• 23 patients (11%) had SAH

• Unable to distinguish on clinical grounds– Activity at onset– Location– Intensity– Hx of migraine– Pain relief with analgesia

Prospective Study of TCHSymptom SAH (%) Non-SAH (%)

Nausea 91 61

Neck Stiffness 61 10

Altered LOC 17 9

Occipital location 57 38

Scintillating Scotomata 0 7

Exploding pain 61 47

Clinical Features Summary

• Most describe abrupt onset• Unique• Severe• Nausea/vomiting, syncope, seizure, diplopia

Reasons For Misdiagnosis

• Failure to know the spectrum of presentations of SAH

• Failure to understand the limitations of CT• Failure to perform an LP• Failure to interpret CSF results correctly

Sensitivity of CT

• Problems with interpretation of the literature– Predominance of retrospective studies– Heterogeneity of post headache “time to CT”– Different CT scanners– Neuroradiologist reads

Sensitivity of CT for SAH inside 12 hours

• Best case is 100%– Perry, J et al (100% sensitivity inside 6 hrs)– Boseger et al (100% sensitivity inside 6 hrs)

Sensitivity of 100%

• Cortnum et al, (Neurosurgery 2010)• Retrospective chart review of patients

referred to a neurosurgical center with confirmed SAH or suspicion of SAH (60% had SAH)

• 99.7% sensitive, only miss was at day 5

Studies with < 100%

• van der Wee N, et al 1995 – 117/119 (98%) in 12 hours– 14/15 (93%) in 24 hours

Studies with <100%

• Byyny et al 2008– Retrospective– Overall sensitivity 93%– Neurologically intact 91%

CT negative, SAH with aneurysmAge Headache GCS Headache

durationCSF supernate

RBC Vascular anomaly

42 SS, LOC 15 <12 h Na 70,000 aneurysm

22 SS 15 <12 h Xantho 370,000 aneurysm

21 SS 15 <12h na pos aneurysm

79 SS 15 24 h Clear 93,500 aneurysm

55 SS 15 3 days Clear 2770 aneurysm

Sensitivity of CT for SAHSensitivity Days after bleed

?93% <1

86 1

76 2

58 5

Near zero 14

Reasons For Misdiagnosis

• Failure to know the spectrum of presentations of SAH

• Failure to understand the limitations of CT• Failure to perform an LP• Failure to interpret CSF results correctly

WHY LP in SAH?

• Unruptured aneurysms of <7mm have a very low risk of bleeding

• 3-5% incidence of aneurysms in general populations

• 10% morbidity/mortality in surgery• Technology creep

“Cannot Miss” Headaches• SAH• Cervico-cranial Artery Dissections• Temporal Arteritis• Acute narrow Angle Closure Glaucoma• Hypertensive Emergencies• CO poisoning• Meningitis encephalitis• Dural Sinus Thrombosis/(benign IC Hypertension)• Hemorrhagic Stroke• ?Mass Lesions

Frequency of LP after negative CT

• 2010 study on those who listed R/O SAH as reason for CT– 59% before educational program– 64% after educational program

Reasons For Misdiagnosis

• Failure to know the spectrum of presentations of SAH

• Failure to understand the limitations of CT• Failure to perform an LP• Failure to interpret CSF results correctly

Positive LP

• Persistently bloody CSF• Xanthochromia

RBC’s

• Immediately present, persist for ?2 weeks• <5 (X 106) is “negative”• SAH with RBC’s in the low 100’s rare

Traumatic Tap

• Can a decline in RBC between tubes 1 and 4 be used to distinguish between SAH and traumatic tap?

• Swadron 2007

• Retrospective look at SAH dx by CT and LP

• 65% of patients with confirmed SAH had a decline in RBC, most by >25%

Traumatic Tap

• D-Dimer• Increased opening pressure• Repeat LP

xanthochromia

• Not reliably present until 12 hours• Persists for ? 2 weeks

Xanthochromia

• Specificity reduced by invitro production– centrifuge delay– Hemolysis from pneumatic tube system

Xanthochromia

• Spectrophotometry vs visual inspection

TCH DiagnosticsVascular imaging pos Vascular imaging neg

CSF Pos Sentinel bleed Low risk

CSF Neg Low Risk N/A

CT Scan

Thunderclap Headache

negative positive

CTA and consult

< 6 hrs > 6 hrs or high pretest probabilityBenign

TCHLP

negativeXanthochromiaPersistent RBC

Consider CTA or NSX Consult if ambiguous LP, > 10 days, or very high risk

Mr KT

• Normal CT head 9 days from headache onset• Persistently bloody (minor) CSF without

xanthochromia

Mr. KT Events

• Two Aneurysms on CTA– 5 X 5 X 8 mm Anterior Communicating Artery– 4 X 4 X 4 left M1 bifurcation

MR KT Events

• FMC admit

Digital Subtraction Angiography

Mr. KT Events

• Discharge May 13 with diagnosis of headache NYD and ?incidental intracranial aneurysms

• May 14, large SAH• May 15 Craniotomy

– ACA culprit– ACA and MCA clipped– Post op course complicated by edema

Major Points

• LP after CT (?within 6 hours)

• Caution with ambiguous LP results

• Caution with delayed presentations