TURN IT UP TO 11: LP IN THE DIAGNOSIS OF SAH Matt Greer February - PowerPoint PPT Presentation

TURN IT UP TO 11: LP IN THE DIAGNOSIS OF SAH Matt Greer February 10 th , 2015

IN CASE YOU MISSED THE REFERENCE

HEADACHES IN THE ED • Account for approximately 2% of ED visits • 1% of these are due to SAH • Approximately 14% get imaging • Only 5% of these show pathology

SUBARACHNOID HEMORRHAGE • Incidence: 6-10 per 100,000 in general population • 10% die prior to arrival • Mean age 40-60 • 1.6 X more likely in women • Risk factors: Smoking, females, binge EtOH, previous hx, family hx, connective tissue d/o

PRESENTATION • 33% have headache as only symptom • 8% have classic “thunderclap” headache • 50% are neurologically intact • Thunderclap h/a and normal neuro exam • 12% chance it’s SAH

IMPORTANT • Type of pain / location of pain has no predictability • Resolution of pain with or without treatment has no predictability

CAUSES (NON-TRAUMATIC) • 80% are aneurysmal (these are the ones we are most interested in) • Perimensencephalic (most common non-aneurysmal) • These generally do very well without intervention • AVM, dural AV fistula, cavernous angioma, vasculitis, amyloid angiopathy, cerebral venous sinus thrombosis… there are more

DIAGNOSIS • Current recommendations from AHA and ACEP • Unenhanced CT, followed by lumbar puncture if initial CT is negative for SAH • But CTs are getting better… do we still need the LP? • This debate has been ongoing in the literature since at least 1995

CHARACTERISTICS OF MOST STUDIES

INCLUSION CRITERIA • >15 years of age • Headache or syncope with associated headache • Non-traumatic (within last 7 days) • Acute h/a (peak intensity within 1 hour of onset) • GCS 15

EXCLUSION CRITERIA • > 14 days since onset of headache • 3 or more headaches of similar character in last 6 months • Focal neurologic deficit • Papilledema • Hx of SAH or aneurysm • Ventricular shunt • Intracranial neoplasm

+ SAH IN STUDIES • Subarachoid blood on CT • Xanthochromia in CSF • > 5 X 10^6 RBCs in 4 th tube with aneurysm on CTA or catheter angiography

CT AND LP APPROACH • We know a few things: • CT sensitivity decreases with time from onset • ? Best < 6 hrs from onset • LP sensitivity increases with time • Best >12 hrs after onset • Some suggest even better a few days later…

IS THIS APPROACH GOOD ENOUGH? • Perry et al. 2008 • Prospective cohort over 3 years • 592 patients with sudden onset h/a who had CT, then LP if CT negative • 61 diagnosed with SAH • Sensitivity of 100% (94-100) • Specificity 67% (63-71)

WHY ARE WE TALKING ABOUT THIS THEN? • There were limitations to the study • Lost to follow up of 19% (although checked for further visits/deaths in their region) • Traumatic taps were considered SAH if > 5 X 10^6 RBCs on last tube AND positive CTA • LPs have risks/morbidity associated • Post LP headaches • Infections, epidural hematomas, pain, etc • LPs can be difficult to interpret • No well agreed upon way to determine traumatic tap

CT FOR SAH • Perry et al 2011 – Prospective cohort study • 3132 patients, 240 with SAH • Sensitivity all comers = 92.9% (89.0 – 95.5) • < 6 hours (953 patients) = 100% • > 6 hours – 17 of 119 SAH were missed! = sens 85.7% • New generation CT scanner (3 rd generation??) • Qualified radiologist (neuro or one who reads head CTs routinely)

CT FOR SAH • Backes et al. 2012 • Prospective cohort of 250 patients (consecutive) • Sensitivity was 98.5% if CT < 6 hours • But was 100% if pt presented with h/a (1 was missed as was a cervical AVM with acute neck pain) • > 6 hours – 92% sensitivity • CT read by neuroradiologists only, xanthochromia by spectrophotometry

LUMBAR PUNCTURE • These can be technically difficult • Can be difficult to interpret • What is a positive result? • Can be painful for patients • Often causes a more intense headache! • Risk of infection, bleeding, need for blood patch, etc.

CSF ANALYSIS • Most sensitive for SAH > 12 hours, < 2 weeks from onset of h/a • Xanthochromia is considered a positive result • But how is xanthochromia determined?

XANTHOCHROMIA • When RBCs are lysed, they release oxyhemoglobin • This is then broken down by macrophages ! bilirubin • Visual xanthochromia can be caused by either of the above • If just oxyhgb – could be from traumatic tap • If just bilirubin – can be caused by elevated serum bilirubin • If both – likely SAH • Can also be caused by drugs like rifampin

XANTHOCHROMIA • Arora et al. 2010 – retrospective chart review of patients with imaging confirmed SAH • 47% had positive xanthochromia, 53% negative by visual inspection • Chu et al. 2014 – systematic review of spectrophotometry vs visual analysis for xanthocchromia in SAH • Spec – 87% sensitive, 86% specific • Visual – 83% sensitive, 96% specific • Lots of problems with review, heterogeneity, defining the outcome, etc.

WHAT ABOUT TRAUMATIC TAPS? • Decreasing RBC count from 1 st to 4 th tube… HOW MUCH OF DECREASE? • Heasley et al. 2005 – Looked at 25% reduction in RBCs • Small numbers, not a great study • 2 of 8 patients with 25% reduction were found to have an aneurysm on CTA

HOW ABOUT JUST DOING A CTA? • 2-5% of people have aneurysm in population • CTA does not tell you if the aneurysm is leaking • How do you (neurosurgery) decide which to treat? • Asymptomatic aneurysms have a low bleed rate (~6% annually)

WHAT DO WE DO?!?!?!?!?!?

CONCLUSIONS • No great answers yet, though imaging appears to be where this is headed • Evidence suggests CT within 6 hours is good enough, as long as: • Qualified radiologist • Modern scanner (ours is a 64 slice, we also have a 16) • Normal neuro exam • Acute headache (not isolated neck pain) • The rest need some combination of LP/CTA if initial CT negative

OTTAWA SAH RULE • Investigate if 1 or more of: • Age 40 or older • Neck pain/stiffness • Witnessed LOC • Onset during exertion • Thunderclap headache (instantly peaking pain) • Limited neck flexion on exam (chin to chest, or lift head > 8cm off bed)

OTTAWA SAH RULE • Sensitivity of 100% (97.2% - 100%) • Specificity of 15.3% (13.8 – 16.9) • One external validation study showed sensitivity of 100% (62.9 – 100) and specificity of 7.6% (5.4 – 10.6) • This was a medical record review of 454 applicable charts (only 9% of headaches could be included) • This rule is probably not quite ready for prime time yet…

REFERENCES • Bellolio MF, Hess EP, Gilani WI, VanDyck TJ, Ostby SA, Schwarz JA, Lohse CM, Robinstein AA. External validation of Ottawa subarachnoid hemorrhage clinical decision rule in patients with acute headache. Am J Emerg Med. 2014. • Perry JJ, Stiell IG, Sivlotti MLA, Bullard MJ, Hohl CM, Sutherland J, Emond M, Worster A, Lee JS, Mackey D, Pauls M, Lesiuk H, Symington, C, Wells GA. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA. 2013;310(12):1248-1255. • Perry JJ, Spacek A, Forbes M, Wells GA, Mortensen M, Symington C, Fortin N, Stiell IG. Is the combination of negative computed tomography results and negative lumbar puncture result sufficient to rule out subarachnoid hemorrhage? Ann Emerg Med . 2008;51:707-713. • McCormack, RF, Hutson A. 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? Academic Emerg Med. 2010;17:444-451. • Perry JJ, Stiell IG, Sivilotti MLA, Bullard MJ, Emond M, Symington C, Sutherland J, Worster A, Hohl C, Lee JS, Eisenhauer MA, Mortensen M, Mackey D, Pauls M, Lesiuk H, Wells GA. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study. BMJ . 2011;343. • Byyny RL, Mower WR, Shum N, Gabayan GZ, Fang S, Baraff LJ. Sensitivity of noncontrast cranial computed tomography for the emergency department diagnosis of subarachnoid hemorrhage. Ann Emerg Med. 2008;51:697-703. • Backes D, Rinkel GJE, Kemperman H, Linn FHH, Vergouwen MDI. Time-dependent test characteristics of head computed tomography in patients suspected of nontraumatic subarachnoid hemorrhage. Stroke. 2012;43:2115-2119. • Arora S, Swadron SP, Dissanayake V . Evaluating the sensitivity of visual xanthochromia in patients with subarachnoid hemorrhage. The Journal of Emergency Medicine. 2010;39:13-16. • Chu K, Hann A Greenslade J, Willliams J, Brown A. Spectrophotometry or visual inspection to most reliably detect xanthochromia in subarachnoid hemorrhage: Systematic review. Ann Emerg Med . 2014;64:256-264.