Category: Neurology

The Slow Death of the Lumbar Puncture

As modern CT scanners become more sensitive, the ability of scanners to discriminate smaller and small abnormalities – such as spontaneous aneurysmal subarachnoid hemorrhage – continues to increase.  This BMJ paper makes another case for forgoing lumbar puncture in patients with a negative CT scan.

Specifically, they say that all the SAH in their cohort was picked up by a 3rd generation scanner as long as the scan was performed within six hours of headache onset.  Unfortunately, this is another one of those studies that uses follow-up as a proxy for the gold standard evaluation – only half of their enrolled cohort underwent lumbar puncture.  They followed up their patients for six months, but survival at six months doesn’t rule out pathology, it only rules out death from that specific pathology, and only if an autopsy was performed.

But, CT scan is starting to get close to the point where the false negatives of CT are equivalent to the false positives of the lumbar puncture – and I would imagine the costs and harms to the patient begin to approach equivalence.  It definitely changes the equation for your patients when you come back with a negative CT scan and your patient wants to know what the chances are they really need this lumbar puncture.

“Sensitivity of Computer Tomography Performed Within Six Hours of Headache For Diagnosis of Subarachnoid Haemorrhage: Prospective Cohort Study”
www.ncbi.nlm.nih.gov/pubmed/21768192

Time To Let ABCD2 Die

The problem – the most difficult clinical situations are the ones where we need a handy decision tool – and the hardest to come up with an effective one.  Syncope rules, PE prediction rules, ACS prediction rules, and now TIA evaluation.

The most important number to come out of this paper is probably 1.8% – the number of patients with a TIA who went on to have a stroke in the next seven days.  That’s 38 out of their 2056 patients enrolled.  The next number is 2.7%, which is the 56 patients who had another TIA within 7 days.  So somehow a rule has to magically pick out that tiny proportion of patients who are going to have bad outcomes without excessively testing the remaining supermajority.

Nearly everyone had a CT of the head, nearly everyone had an EKG, very few (15% with an ABCD2 score ≤ 5 and 22.% with a score > 5) had consultation with a neurologist, and even fewer were admitted.  The specificity for stroke within 7 days with a score >2 – the AHA definition of “high risk” – is only 12.5%.  Not only that, but there was significant disagreement between enrolling physicians and the study center regarding the correct ABCD2 score for a patient.

So, in the end, ABCD2 is difficult to apply and only minimally useful.  You’re going to miss half the strokes at 7 days if you apply it in a situation where the specificity is >50% – so, sure, a sky-high score tells you they’re in trouble, but that still doesn’t help you discharge the majority of your TIAs safely for outpatient follow-up.

“Prospective validation of the ABCD2 score for patients in the emergency department with transient ischemic attack.”
www.ncbi.nlm.nih.gov/pubmed/21646462

Sensitivity of CT Angiography for Aneurysms

Not exactly the article I was expecting when I pulled it, but mildly interesting nonetheless.  The real applicability of this article is towards those folks who say the LP for SAH is outdated, and we should just proceed with CTA to identify the culprit aneurysm.

As opponents say, many aneurysms identified by CTA are asymptomatic and unrelated to the acute headache in the Emergency Department, and, without the LP, you don’t know their clinical relevance.  This study lets them also say that CTA doesn’t even necessarily perform well enough at this task to warrant use – it will miss 5% of aneurysms and overcall 3.8%.

However, it must be said, this meta-analysis uses data from a number of old studies that have older CT scanners that were very poor at detecting <4mm aneurysms.  Once you get to 16 and 64 row CT, your sensitivity is closer to 98-99% – and then you have to fall back to the asymptomatic/clinical relevance argument.

“Diagnosing cerebral aneurysms by computed tomographic angiography: meta-analysis”
http://www.ncbi.nlm.nih.gov/pubmed/21391230

Neurothrombectomy Devices – Still Not The Answer

Catheter-based endovascular treatment of acute ischemic stroke has been around for several years – this is a nice, concise review of the published literature regarding their use.

The abstract sounds a little more favorably skewed than the actual content of the article – their discussion is appropriately skeptical regarding the efficacy and applicability of this particular treatment modality.  It is certainly true that restoring flow to affected regions in stroke is advantageous, and the theory behind the use of these devices is to mechanically ensure open vessels in situations where systemic thrombolysis may not be efficacious and the disability is likely to be profound.

The problem is, there really isn’t any “evidence” in this article.  The published literature on this topic is primarily retrospective cohort/case-reports by industry-affiliated inventors of these devices and, even despite this bias, that literature tends to report unacceptable levels of procedural complications while trying desperately to show benefit.

Regardless, as the authors mention, there are many studies of MERCI and Penumbra ongoing – slowly chasing that inexorable statistical probability of finally performing enough studies that, by chance, one of them will be favorable enough upon which to base widespread marketing efforts.

“Neurothrombectomy devices for the treatment of acute ischemic stroke: state of the evidence”
http://www.ncbi.nlm.nih.gov/pubmed/21242342

Significant Populations Have No Timely Access to Stroke, Pediatric Trauma Care

These are a couple studies from a family of publications that use population data, GIS mapping tools, and travel times by air and ground to estimate what percentage of the population has access to a certain healthcare resource.  In these two papers, the resources in question are Primary Stroke Centers and Pediatric Trauma Centers.  They estimate that 71% of the pediatric population is within 60 minutes of a pediatric trauma center by ground or air – which is appropriate, because trauma systems are set up to use aeromedical transport.  However – and, depending on what direction the TPA pendulum swings – only 55.4% of the population has access to a stroke center within 60 minutes – by ground, which is typical.  They say this could be increased to 79% within 60 minutes if aeromedical resources were involved, but I think we should wait to establish a greater treatment effect for acute stroke treatment before we go nuts with air travel.

I like maps; I worked with one of the authors (Dr. Branas) on previous iterations of descriptive articles similar to these.  The problem with these articles is the statistic they describe – timeliness of care – may or may not have significant effects on patient outcomes.  And, in theory, the solutions – moving trauma center designations, establishing new stroke centers, increasing aeromedical use, etc., have significant costs and unintended consequences.

http://www.ncbi.nlm.nih.gov/pubmed/20937948
http://www.ncbi.nlm.nih.gov/pubmed/19487606

Olanzapine Versus Droperidol

This is a fun study because it’s always nice to have new things to try for common problems.  Keeps life interesting.

I started out residency taught to use metoclopromide+diphenhydramine for treatment of refractory headache in the Emergency Department.  And then I discovered droperidol.  Yes, there are studies out there that say prochlorperazine is equivalent to droperidol in efficacy, but prochlorperazine gives people the same akathisia that metoclopromide does.  Droperidol kills people dead, if you believe the black box – though I don’t.  The QT-prolongation is essentially no different than ondansetron, the supposedly-safe alternative we now use for nausea.

In any event, now you can add olanzapine to your mix.  You can legitimately critique the study because the p-value for pain improvement between olanzapine and droperidol was actually 0.30 in favor of droperidol  – so without more power and/or a second confirmatory study, you can say it really might not be as effective.  But, the good thing is, nearly everything has some legitimate effectiveness – and the more different classes of medication you have available to knock down that headache, the better.

http://www.ncbi.nlm.nih.gov/pubmed/19244630