History

• 53 year old male with a history of IVDU and 1.5 months of “stabbing” lower back pain 
• Reports he was riding his bike 2 days ago and was hit by a car that acutely worsened the pain 
• Reports difficulty urinating, lower extremity weakness, straining with BM, fevers, chills, weight loss, and thigh pain

Physical Exam

T 97.1 BP 152/72 HR 80 RR 22 Pox 100% on RA

• Pt is visible uncomfortable lying down on stretcher
• Moving all extremities with pain on passive movement of both legs
• L posterior thigh tenderness with obvious mass on deep palpation
• Tenderness to percussion on L spine.
• CN II-XII intact. Strength is 5/5 UE and LE. Sensation intact-no saddle anesthesia. Rectal tone intact. Patient is able to ambulate.

Differential Diagnosis 

• Vertebral osteomyelitis/epidural abscess
• Lumbar spine fracture given hx of MVC 
• Lumbar strain
• Sciatica

Management 

• CT lumbar and thoracic spine without contrast ordered STAT
• Basic labs, blood cultures, ESR, CRP, IV pain medicine

Results

CT imaging: findings consistent with discitis and osteomyelitis at L4-L5, bilateral psoas abscess, and a suggestion of spinal canal phlegmon or abscess with severe stenosis 

Outcome 

• Neurosurgery consult was called
• Patient was bladder scanned and retaining >400cc, Foley placed
• MRI L spine with and without contrast ordered stat
• Antibiotics held for possible OR
• MRI eventually showed 4.3cm posterior epidural abscess along with multiple bilateral psoas abscesses and osteomyelitis/ discitis of L4-L5.
• OR wound cultures were positive for Staph Aureus

Discussion 

• Spinal epidural abscess is a rare but risk is increased due to IV drug use and spinal procedures 
• Most often occurs due to hematogenous spread
• Back pain is the most common presenting complaint and is often the only symptom 
• MRI is test of choice for diagnosis
• WBC count/ESR/CRP are not reliable enough to exclude infection

Take Home Message

• New back pain in an active IV drug use patient is infectious until proven otherwise
• Don't rely on lower extremity weakness, bowel/bladder incontinence, or saddle anesthesia: these are late findings and denote irreversible damage
• Don't rely on plain films, labs, or even CT scan to exclude osteomyelitis/discitis/epidural abscess in a high risk patient

 Sources:

Tanski M, Ma O. Central Nervous System and Spinal Infections. In: Tintinalli JE, Ma O, Yearly DM, Meckler GD, Stapczynski J, Cline DM, Thomas SH. eds. Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9e.