Himmel, W, Steinhart, B, Helman, A. Low Back Pain Emergencies. Emergency Medicine Cases. September, 2012. https://emergencymedicinecases.com/episode-26-low-back-pain-emergencies/. Accessed 6-9-2021.
All that follows is from the above podcast and show notes:
In this episode we go through seven cases that display the breadth of presentations of limb or life threatening causes of low back pain emergencies with my huge mentors, Dr. Walter Himmel and Dr. Brian Steinhart. We cover everything from spinal epidural abscess to cauda equina syndrome to retroperitoneal bleeds, elucidating the key historical, physical exam, lab, imaging and treatment pearls for all of these diagnoses. We then go on to review the best management for the most common cause of back pain presentation, lumbosacral strain and debate the various medication options.
Dr. Steinhart & Dr. Himmel answer such questions as: Which patients with low back pain require an MRI in the ED? How useful is an ESR or CRP in diagnosing Spinal Epidural Abscess and Cord Compression secondary to spinal metastases? What is the role of dexamethasone in treating spinal cord compression? What are the physical examination maneuvers and bedside tests that are the most useful for diagnosing cauda equina syndrome and spinal cord compression?
APPROACH TO LOW BACK PAIN EMERGENCIES
Main categories of patients with acute back pain:
- nonspecific lumbosacral pain/strain
- radicular pain or sciatica
- emergent pathologies.
The 5 emergent pathologies are:
- infection such as osteomyelitis, or spinal epidural abscess,
- fracture (trauma or pathologic),
- disk herniation & cord compression,
- cancer in spine causing cord compression,
- vascular – leaking/ruptured AAA, retroperitoneal bleed, and spinal epidural hematoma.
Red flags for Low Back Pain Emergencies
- Age 60,
- Symptoms or history of cancer,
- Immunodeficiency (including diabetes, IVDU), previous spinal interventions, or recent infections,
- Pain not resovled by analgesia,
- History of trauma or coagulopathy,
- Cauda equina/cord compression symptoms (bowel, bladder or erectile dysfunction, saddle paresthesia, progressive bilateral leg weakness)
Pearls: *Constant, unrelenting, severe pain, especially if it is worse lying down is a red flag for infection or cancer.* Discogenic pain is worse with flexion, and pain from spondylolysis is worse with extension
Update 2018: While positive responses to “red flag’ questions for low back pain (e.g. bowel or bladder incontinence, history of cancer, trauma, fever, IV drug use etc) prompt further investigation, negative responses are not sufficient to rule out serious pathology. Though conclusions were based on a large retrospective review, the authors present data recommending caution when using “red flag” questions as screening tools. Abstract
- Upwards of 90% of low back pain presentations in the ED are due to benign causes. However there are several important life/limb- threatening diagnoses we must consider in the low back pain patient, and most of these diagnoses are easy to miss. Furthermore, lumbosacral sprain is often associated with significant morbidity, and ED docs should provide specific education and evidence based treatments.
Physical exam for Low Back Pain Emergencies
Physical Exam Maneuvers:
- Percuss the spinous processes for tenderness, a red flag for infection and fracture,
- Test for saddle anesthesia (sensation changes may be subtle and subjective),
- DRE looking for tone/sensation
- Look for fever, or signs of infection,
- Check carefully for bilateral, or multi-level neurologic findings in lower extremities, and assess for gait disturbances.
Straight leg raise (SLR):
- Non-specific test, only positive pain is produced distal to the knee between 30–70°.
- Pain with contralateral SLR is more specific for siatica.
Slump test: Helps discriminate radicular pain from hamstring pain. With thoracic and cervical flexion, and knee in extension, dorsiflex the foot and flex the neck to determine if pain is produced, with release of cervical flexion to see if symptoms improve (image below).
Insert fig1 when server not busy.
Abdomen exam and ED ultrasound: look for AAA and bladder distention post-void.
Cognitive Forcing Strategy to Remember Serious Back Pain Pathologies:
Considering renal colic?…think about AAA!
Considering pyelonephritis?….think about spinal infection!
SPINAL EPIDURAL ABSCESS
Suspect epidural abscess in a patient with:
- back pain or neurologic deficits and fever,or
- back pain in an immune-compromised patient, or
- patient with a recent spinal procedure and either of the above
Risk Factors: Diabetes, IVDU, indwelling catheters, spinal interventions, infections elsewhere (especially skin), immune suppression (i.e. HIV), and “repeat ED visits.”
The classic triad of fever, back pain, and neurologic deficit is present in only 15% of patients, depending on stage of disease. Spinal epidural abscess is often missed on first ED visit. Fever is present in only 50% of patients, and neuro deficits start very subtly.
CRP and ESR may help, depending on the clinical suspicion for epidural abscess. If suspicion is low after the history and physical, low ESR and CRP levels support not doing an MRI, and discharging the patient home with close follow up. If there is a high index of suspicion, an MRI is indicated regardless of CRP and ESR.
Remember the normal ESR cutoff is: (age+10)/2.
In one study of epidural abscesses, 98% had ESR >20, and most were much higher (>60).
Is there any role for CT scan? CT cannot rule out epidural abscess because it does not show the epidural space, spinal cord, or spinal nerves adequately. CT can lead to the diagnosis of osteomyelitis and premature closure, missing coexistent abscess (and the urgent indication for surgery).
Remember if the suspicion is epidural abscess, the entire spine must be imaged by MRI. Spinal cord obstruction and paralysis can happen very quickly from epidural abscess, so there needs to be definitive imaging and surgical decompression as quickly as possible.
Start antibiotics while awaiting definitive diagnosis: include appropriate coverage for MSSA and MRSA, and cover gram negatives.
CAUDA EQUINA SYNDROME
Definition of Cauda Equina Syndrome:
- urinary retention or rectal dysfunction or sexual dysfunction (or all of the above)
- saddle or anal anesthesia and/or hypoesthesia (1).
- Urinary retention is non-specific for cauda equina syndrome, but sensitive.
- A post void residual >100mL should raise the suspicion for cauda equina syndrome
When are steroids indicated?
- Evidence supports dexamethasone for metastasis to spine causing cauda equina.
- There is no indication for IV steroids for patients with cord compression by other causes
SPINAL METASTASIS – A LOW BACK PAIN EMERGENCY
- Known cancer + new back pain = spinal metastases until proven otherwise!
- Time is Limbs: Spinal metastases are one of the most common causes of cord compression. Pre-treatment neuro status predicts outcome for this emergency.
- X-ray to look for compression #, soft tissue changes, blastic/lytic lesions, pedicle erosion (see image below)
- Consider testing ESR and CRP, and calcium profile if signs are consistent with hypercalcemia (e.g. polyurea)
- Give dexamethasone as soon as mets are suspected (at least 10mg IV) if the patient has neurologic symptoms. Consider bisphosphonate* and calcitonin if patient is hypercalcemic, or if you suspect compression # or bony metastasis.
- Get an urgent MRI if there are symptoms of cord compression. If there are hard neurologic findings, MRI is needed within 24 hours. If the x-ray findings are consistent with mets, but there are no neuro findings, an MRI should be done within 7 days.
*Bisphosphonates may decrease bone resorption in patients with metastatic disease to the bone, and relieve pain better than placebo.
VASCULAR EMERGENCIES ARE LOW BACK PAIN EMERGENCIES