Low Back Pain

Today we discussed a common presentation but difficult dilemma: chronic low back pain, with new neurological symptoms. When do you know to investigate further? How do you manage complex pain? What are the red flags? What is an anatomical approach to neurological manifestations? We discussed many of these issues today. For the internist, it is often important to be able to differentiate inflammatory from mechanical back pain.

It's worthwhile discussing the differential diagnosis of back pain, which includes:

Mechanical

• MSK injury
• Degenerative discs & facet joints
• Anatomic anomalies (scoliosis, spondylolisthesis)

Neurological

• Disk herniation, with irritation of adjacent nerve roots
• Spinal stenosis

Non Mechanical Spinal

• Malignancy (primary or secondary) with or without cord compression
• Inflammatory: Ankylosing spondylitis (& other seronegative spondyloarthropathies), RA
• Infectious: osteomyelitis, epidural abscess

Visceral radiation (pelvic, kidney, GI tract, aorta)

Remember that there are several key elements to a thorough back examination:

Inspection: anteriorly (looking for alignment), posteriorly (looking for asymmetry, deformity, rashes, etc), and laterally (for kyphosis, lordosis). Also inspect their gait.

Range of motion: Assess flexion, extension, rotation, and lateral bend while standing, looking for limitation & pain. From the seated position, test rotation of the spine at the thoracolumbar region - limitation is an early indicator of inflammatory back pain.

Palpation: of spinous processes and paraspinal muscles for pain or spasm.

Special Tests: compression test (of SI joints) with patient on side, FABER test, Gaenslen's test, Book test with patient supine (pressure over both trochanters.

Other special tests to differentiate between mechanical and inflammatory back pain include the straight leg raise (positive in mechanical), femoral stretch test, the occiput to wall test, the Modified Schober, and the

A full neurological examination should accompany this exam, including a DRE to assess for sphincter tone if cord compression is suspected.

See here for an excellent BMJ review.