Low back ache and disc disease

What are the common causes for low back ache?

• Muscle spasm/ligamentous strain
• Trauma
• Osteoarthritis:
  • Degenerative disc disease
  • Facet joint disruption/degeneration
  • Herniated disc
  • Spinal stenosis
• Osteoporosis: Vertebral compression fracture
• Vertebral metastasis

When will you consider imaging studies to investigate back pain?

Imaging techniques are rarely used as most back pain is due to muscle spasm and ligamentous strain.

Consider imaging work up when there is:

• pain lasting greater than one month.
• very severe pain.
• numbness.
• muscle weakness.
• accidents that might involve the vertebrae.
• fever.
• history of cancer.
• radiating pain to lower extremity.

What are the available imaging procedures for low back ache? What is the utility of each of these procedures?

Possible imaging modalities include:

• Plain radiographs
  • X-rays can rule out tumors, infection and injury.
  • X-rays can also show signs of stenosis and changes due to aging.
• MRI
  • MRI is more accurate and allows visualization of the soft tissue and bone.
  • MRI can detect annular tears, infection and cancer.
  • Limitations
    • MRI misses 6-23% of damaged discs that were found during surgery.
    • About 40% of adults are found to have "bulging discs", however, the majority of these patients do not have back pain.
    • Therefore, back pain and disc problems revealed through imaging techniques are not necessarily always correlative.
• CT
  • CT scans are also used to investigate back pain but MRI is superior.
  • CT is done for focal fractures of vertebral foraminal stenosis.
• Bone scan
  • Bone scans are particularly useful for spinal fracture, cancer and osteoarthritis.
• Myelography
  • A myelogram has been largely replaced by CT and MRI.

You are being presented with following case histories. Which imaging procedure would you order?

Case 1

22 y/o patient complains of one week of back pain. Pain started day after he helped his friend move to a different apartment. Pain does not wake him from sleep, and is alleviated with NSAIDS. Pain is slowly improving, and he is able to go to work without significant discomfort.

Answer: Imaging procedures are not necessary. History is consistant with muscle sprain.

Case 2

A 49 y/o female reports three weeks of lower back pain. The pain is not associated with any specific incident. The pain radiates into her left buttock and posterior thigh. There is mild weakness of left foot dorsiflexion and toe extension. The patient has a few fasciculations is her left calf and dorsal foot. Her other muscles reveal no weakness. Pinprick sensation is decreased over the left dorsal foot. There is no babinski sign. Her pain can be reproduced with passive flexion of the hip.

Answer: This clinical picture is consistent with disc herniation. MRI is the procedure of choice.

Case 3

70 y/o male who has been diagnosed with prostatic cancer, which has metastasized to his lymph nodes. For the last month he has had difficulty rising from his chair. He also complains of sharp, shooting pain in his lower back which increases with coughing or straining.

Answer: We should suspect a vertebral metastasis with evidence for cord compression. An MRI is recommended. Plain x-rays and bone scan can provide evidence for vertebral metastasis but not information about the cord.

Case 4

40 y/o male has 1 day of spastic weakness in his legs, and one episode of incontinence. His deep tendon reflexes are increased – 3+ bilaterally.

Answer: A spinal cord tumor is suspected and an MRI of the spine should be ordered.

Case 5

82 y/o thin female with back pain for several months. Her back pain began after a minor fall that she had several months ago. She stated that she just fell into a sitting position on her couch.

Answer: This history should suggest osteoporosis with vertebral fracture. Plain x-rays and bone densitometry studies will be indicated, followed by MRI.