EBQ:Differentiation between traumatic tap and aneurysmal subarachnoid hemorrhage
- Can cerebrospinal fluid from patients with acute headache after traumatic lumbar puncture be distinguished from subarachnoid hemorrhage?
- No xanthochromia and red blood cell count < 2000 × 106/L can reasonably excludes the diagnosis of aneurysmal subarachnoid hemorrhage.
- In ruling out traumatic subarachnoid hemorrhage, the traumatic tap which causes blood to mix with cerebrospinal fluid can complicate the diagnosis of subarachnoid hemorrhage in up to 30% of LPs.
This study was a predefined subsidy of the Canadian subarachnoid hemorrhage (SAH) rule and provides data to classify the likelihood of a subarachnoid hemorrhage based on LP results. Using a threshold of 2000x106/L in the final CSF tube provides for a sensitivity of 100% (CI 74.7-100%) and specificity of 91.2% (88.6-93.3%). For xanthochromia however the sensitivity was only 46.6% (CI 22-72.6%) for diagnosing subarachnoid. Combining the RBC threshold with xanthochromia the sensitivity for subarachnoid hemorrhage is 100%
- Planned substudy from the prospective multi center cohort study, designed to derive and validate the Ottawa SAH (subarachnoid hemorrhage) rule
- Conducted between November 2000 - December 2009
- Multicenter at 12 canadian academic EDs
- Mean Age: 43yo
- Sex: 40% Men/60% Women
- Age >15
- Alert patients (GCS =15)
- ED patents with acute non-traumatic headache undergoing LP to rule out subarachnoid hemorrhage
- Within 14 days of headache onset
- Recurrent headaches (3 or more with similar character/intensity over 6 month or greater period
- Transfered from other hospital with confirmed subarachnoid
- Presence of focal neurologic deficits or papilledema
- History of
- Subarachnoid hemorrhage
- VP shunt
- Brain neoplasm
- Computed tomography and/or lumbar puncture was performed at the discretion of the treating physician
- Some LPs were performed before CT scans
- Patients discharged without having both computed tomography imaging and a normal result on lumbar puncture were assessed by telephone interview one month and six months after assessment in the emergency department as well as a review of medical records to identify any recorded subarachnoid hemorrhage.
- Patients without telephone follow-up or subsequent hospital encounters at the enrolling sites were further checked against the coroner’s records to identify any deaths compatible with subarachnoid hemorrhage
Subarachnoid hemorrhage definition:
- Blood in the subarachnoid space on CT brain
- Xanthochromia on examination of CSF
- Red blood cells in the final tube of CSF fluid and aneurysm shown with cerebral angiography requiring any neurovascular intervention or resulting in death.
Normal LP = 1098 Abnormal LP = 641 (36.9%)
- No aneurysmal subarachnoid = 626
- Aneurysmal subarachnoid 15
- Xanthochromia = 7
- No Xanthochromia = 8
There were 15 (0.9%) patients with aneurysmal subarachnoid hemorrhage based on abnormal results of a lumbar puncture.
The presence of less than 2000 × 106/L red blood cells in addition to no xanthochromia excluded the diagnosis of aneurysmal subarachnoid hemorrhage
- Sensitivity of 100% (95% confidence interval 74.7% to 100%)
- Specificity of 91.2% (88.6% to 93.3%).
Characteristics or patients in Canadian SAH Rule Study
All patients in the SAH Rule derivation and validation cohort
- Neck Pain or stiffness: 33.7%
- Median time of headache onset to peak: 60 seconds
- CT performed: 81.7%
- Mean time from headache onset to LP: 18 hours
- Median RBC count in last tube: 0
- Aneurysmal subarachnoid hemorrhage: 3.5%
Characteristics of patients with abnormal LP
- Aneurysmal subarachnoid hemorrhage: 46.6%
- No Subarachnoid: 2.6%
Median RBC count in last tube (x106)
- Aneurysmal subarachnoid: 28741
- No subarachnoid: 20
- Aneurysmal subarachnoid hemorrhage: 15%
- No subarachnoid: 64.5%
Criticisms & Further Discussion
- Although this study is useful for defining the number of RBCs concerning for a SAH it does not help guide the workup for patients with a negative CT and positive lumbar puncture. There was also a great percentage of patients who underwent CT angiography for a small percentage of SAH.
- A study by Gorchynski found that RBC counts ≤ 500 x106/L in the 4th CSF tube had a 100% negative predictive value for subarachnoid hemorrhage
- Caution should be used for assessing abscess of SAH based on the percentage drop in RBC count since the presence of SAH was demonstrated in patients with a 25% reduction of RBCs between the 1st and 4th tubes
Funded by the Canadian Institutes of Health Research (grants: 67107, 153742), the Ontario Ministry of Health and Long Term Care, and the physicians of Ontario through the Physician’s Services Incorporated Foundation
- Gorchynski J, Oman J, Newton T. Interpretation of traumatic lumbar punctures in the setting of possible subarachnoid hemorrhage: who can be safely discharged? Cal J Emerg Med 2007;8:3–7.
- Perry JJ et al. Should spectrophotometry be used to identify xanthochromia in the cerebrospinal fluid of alert patients suspected of having subarachnoid hemorrhage? Stroke 2006;37:2467–72.
- Perry JJ. et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA. 2013 Sep 25;310(12):1248-55.
- Gorchynski J. et al. Interpretation of traumatic lumbar punctures in the setting of possible subarachnoid hemorrhage: who can be safely discharged? Cal J Emerg Med 2007;8:3–7.
- Heasley DC et al. Clearing of red blood cells in lumbar puncture does not rule out ruptured aneurysm in patients with suspected subarachnoid hemorrhage but negative head CT findings. Am J Neuroradiol 2005;26:820–4.