A 35 year old man presents with low back pain which radiates down his right leg to the level of the knee. Is this sciatica?
Low back pain is one of the most common chief complaints that we see in the Emergency Department. In addition to the examination of the back and distal neurovascular function, we also need to test for evidence of a radiculopathy (compression or inflammation of a nerve root typically from a herniated disk). Because most disk herniations occur at the L4-L5 and L5-S1 level, you should test for irritation of the L4-S1 nerve roots. This is the sciatic nerve.
The straight leg raise (SLR) maneuver tests for such irritation. By passively elevating the patient's extended right leg, this maneuver stretches the sciatic nerve. If compressed or inflamed, this maneuver will reproduce pain in the sciatic nerve distribution. Note that isolated back pain with this maneuver does NOT mean a positive SLR test.
In a 2010 Cochrane review, the SLR test yielded a high sensitivity (92%) and low specificity (28%). This means that a negative SLR almost rules out a sciatic radiculopathy and disk herniation at the L4-L5 and L5-S1 level.
What about all those patients who have back pain and a little hamstring muscle vs sciatic nerve irritation with the SLR maneuver? Is there a more specific test?
Crossed Straight Leg Raise maneuver
For a patient with back pain radiating down their right leg, also perform the crossed SLR maneuver. If elevating their LEFT leg passively reproduces pain down his/her affected RIGHT leg, this is highly predictive of a sciatic radiculopathy and disk herniation. The crossed SLR maneuver essentially stretches the left L4-L5-S1 nerve root and thus tugs on the right L4-L5-S1 nerve root.
The 2010 Cochrane review shows that the crossed SLR has a low sensitivity (28%) but really high specificity (90%) for disk herniation.
Reference
van der Windt DA, Simons E, Riphagen II, Ammendolia C, Verhagen AP, Laslett M, Devillé W, Deyo RA, Bouter LM, de Vet HC, & Aertgeerts B. Physical examination for lumbar radiculopathy due to disc herniation in patients with low-back pain. Cochrane database of systematic reviews (Online). 2010 Feb 17;(2):CD007431. PMID: 20166095
Does having a positive straight leg or crossed straight leg change your managment? If they don't have cauda equina symptoms or any other neuro symptoms by history, won't you just give NSAIDs +/- muscle relaxers?
ReplyDeleteWow, of all the years that I've been giving a low back pain talk, I've never been asked this. Great question -- I'm a big proponent that if a test doesn't change acute or long term management, it shouldn't be done.
ReplyDeleteThe question then is: Does it matter whether you differentiate "low back pain/strain" from "disc herniation with sciatica"?
You are totally correct -- you still recommend NSAIDs +/- muscle relaxants +/- opioids. Especially with studies showing the questionable benefit of surgery for disc herniation, conservative management is key.
Personally, I like to differentiate for 2 reasons:
1. Patients like to have a diagnosis and often ask -- "Is this sciatica?"
2. A herniated disk is a common cause for cauda equina syndrome (CES) when it bulges more centrally. So I give them EXTRA clear precautions about CES.
I think it makes a difference:
ReplyDeletecrossed-SLT points to a larger, usually more central herniation. Such patients need to watched more closely and informed about a cauda equina symptom complex.
Hey Peter: Excellent point. I hadn't thought of it from that perspective.
ReplyDelete@Peter:What is the evidence to your statement that a positive crossed-SLT points to a larger and more central herniation? The whole topic of LBP diagnosis and treatment is littered with logical opinions that ultimately turn out to be wrong when critically studied.
ReplyDelete