Join the debate between Bill Knight and Fernanda Bellolio as they go head-to-head, discussing diagnosing subarachnoid haemorrhage in neuro critical care headache. Should you rely on CT and lumbar puncture or, CT followed by CT angiogram. Why should you care? Acute headache accounts for 4% of all visits to the emergency departments. These patients will often describe the “Worst headache of life” – a phrase which can ring the alarm bells in the clincian’s mind. 88% of these will be from benign causes including migraine, tension and cluster. However 10% will have a subarachnoid haemorrhage, of which the vast majority are caused by an aneurysm. These are frequently missed - up to 51% of the time in all settings and 6% of the time in the emergency department. It is in face one of the largest sources of US litigation claims and settlements. So – what is the best way to diagnosis subarachnoid haemorrhage? Bill asserts that the lumbar puncture (LP) following the CT is the way to go. He stresses that the “miss rate” needs to be 0% for subarachnoid haemorrhage. He argues that with the combination of CT and LP the sensitivity for subarachnoid haemorrhage is 100% Fernanda on the other hand is a big proponent of using the combination of CT followed by CT angiogram (CTA). She discusses the very low incidence of subarachnoid haemorrhade and takes this into account when calculating the pre- and post-test probability for her patients. She argues that if the pre-test probability is higher for a patient, then a CTA can be utilised. Bill Knight and Fernanda Bellolio present a compelling case for both sides when identifying the best way to diagnose subarachnoid haemorrhage in neuro critical care headache.

1. CT-LP
vs.
CT-CTA
William A. Knight IV, MD M. Fernanda Bellolio, MD
26 Jun 2017

2. Disclosures

3. 4%

4. Migraine
Tension
Cluster

5. 10% - SAH
• Aneurysm – 80%
• AVM
• Vasculitis
• Cavernous angiomas
• Neoplasm
• Mycotic aneurysms
• Blood dyscrasias
• ICH
• Trauma
• Perimesencephalic hemorrhage
1-2%
• Idiopathic Intracranial HTN
• Meningitis
• Carotid or vertebral dissection
• CVST
• RCVS
• PRES
Worst Headache of Life

7. SAH Misdiagnosis
• Frequency of misdiagnosis = 12-51%
• ED miss rate ~ 6%
• 37% of missed diagnoses re-present to a different hospital
• One of largest sources of US ED litigation claims and settlements

8. Preface
Focus on Subarachnoid Hemorrhage
But…what about all the other “can’t miss” diagnoses
Acceptable miss rate
0%
CT-LP sensitivity
100%
Do you want to diagnose the SAH or the aneurysm?

10. I think we can agree…

11. What about onset within 6 hours?
• Neurologically normal
• CT performed within 6 hours on headache onset
• Read as normal by attending-level radiologist
• Miss rate? 1:600 -1000 patients
• Discuss with patient…

12. Lumbar puncture
• Standard of Care
• Why?
• Shown to detect small amounts of blood or xanthrochromia
• First test able to do so

13. 100% sensitive
3 year follow-up

14. “Standard of Care”
2008

15. Most desired ED procedures
• Intubation
• Chest tube
• ED Thoracotomy
• Central line
• Lateral Canthotomy
• Joint reduction
• Laceration repair
• Abscess drainage
• Pelvic exam
• Paronychia drainage
• Butt pus
• Bartholin’s gland drainage
• Lumbar Puncture

16. LP complications
• Patient discomfort
• Local tissue irritation/infection
• Reflex muscle spasm
• Postdural puncture headache
• Nerve injury
• Epidural hematoma
• Meningitis
• False positive results…

17. LP Limitations
• Unruptured aneurysms
• Arterial dissection
• Cerebral venous sinus thrombosis
• Pituitary apoplexy
• Time consuming
• Technically challenging
• Obese or uncooperative

18. Added benefits
•Differentiate other diagnoses
• Meningitis
• Idiopathic intracranial hypertension
• Cerebral sinus venous thrombosis
• Spontaneous intracranial hypotension

20. • 13.3% incidence in the ED
• 400 RBCs as the cutoff
• 8.9% incidence in the ED
• 1000 RBCs as the cutoff
• May need to repeat at different lumbar interspace
• 2/3 of SAH have elevated opening pressure…
Traumatic tap?

21. What’s the problem here?

22. CT Angiogram
• Identify down to 3mm aneurysms
• Require contrast to fill the aneurysm
• Only rule out vascular causes of headache
• Can reach 99% negative predictive value

23. UCMC Aneurysm workup
• CT positive for SAH
• CT Angiogram
If negative
• Digital Subtraction Angiogram
If negative
• MRA
If negative
• Repeat DSA in 6 weeks

24. CT Angiogram
Non-contrast head CT – 1.7 mSv
CTA head – 1.9 mSv
CTA neck – 2.8 mSv
Contrast induced nephropathy

25. $$$
CTAs are expensive
Resource intensive
Time to interpretation
Reconstructions?

27. True. True. Unrelated.

28. • What do I do with headaches that present acutely?
• CSF most sensitive after 12 hours from headache ictus
Fair question…

29. Timing Matters
Non-contrast CT
• 0-6 hours – 99+%?
• 0-24 hours – 93-98%
• After 3 days – 85%
• After 1 week – 50%
CSF
• 0-2 hours - may be negative
• 0-12 hours - ???
• 12+ hours – most sensitive
• 100% have xanthrochromia
• 70% at 3 weeks
• 40% at 4 weeks
• WBC:RBC – 1:1000
• Within 24 hours

30. • What if body habitus makes the LP….
difficult or impossible?
• Or, I have 30 people in the lobby and a low pre-test probability…
• Or the patient refuses, or wants out AMA?
• INR 2.6?
• Is CT/CTA good enough then?
Wait…

31. • What if body habitus makes the LP….
difficult or impossible?
• Or, I have 30 people in the lobby and a low pre-test probability…
• Or the patient refuses, or wants out AMA?
• INR 2.6?
• Is CT/CTA good enough then?
Wait…

32. One final question…
• 1 SAH : 700-1000 LPs
• How does your documentation look?

33. Closing Remarks?

35. Overall
• Many studies show CT is highly specific:
• Unlikely to reveal a false positive
• Highly sensitive (~ 92-98%)
• Miss rate of 2-8% is unacceptable
• Diagnoses missed by non-contrast CT:
• Small SAH, Idiopathic Intracranial HTN, Meningitis, Carotid or Vertebral Dissection, CVST
• If you suspect it, get the CT
• If +: Great (for your diagnosis, not the patient)
• If -: Now what?