Back pain is a common, self-limited condition in many people. Discitis, cancer and cauda equina syndrome are causes of back pain which are not innocent and self-limiting. First, by way of background, define "cauda equina syndrome", discitis and the common cancers that are found in the spine. Suggest some questions a physician might ask to help detect these diagnoses.
Cauda Equina Syndrome is a serious neurologic condition in which there is acute loss of function of the lumbar plexus. The "cauda equina" is made up of the nerve roots that branch off of the lower end of the spinal canal beneath the termination of the spinal cord (conus). The cauda equina contain the nerve roots from L1-L5 and S1-S5. The nerve roots branching off the spinal canal beneath the termination of the spinal cord is said to resemble a horse's tail, hence the name, but I am not sure. You decide:
Cauda Equina syndrome occurs when the nerves of the cauda equina are compressed by a herniated disc material, tumor, or bone (trauma). Cauda Equina Syndrome presents with weakness of the muscles innervated by the compressed roots, sphincter weaknesses causing urinary retention, and post-void residual incontinence. There may also be decreased anal tone; sexual dysfunction; saddle anesthesia; bilateral leg pain and weakness; and bilateral absence of ankle reflexes. Pain may, however, be entirely absent. The diagnosis is usually confirmed by an MRI scan or CT scan. Treatment typically involves URGENT surgical decompression.
Discitis is an infection in the intervertebral disc space.
Pathogens can reach the bones of the spine by hematogenous spread from a distant site or focus of infection, direct inoculation from trauma or spinal surgery, or contiguous spread from adjacent soft tissue infection. Staphylococcus Aureus accounts for more than half of cases in developed countries. Symptoms include severe back or neck pain, which often lead to immobility. Fevers have been noted in some patients. The diagnosis is usually confirmed by an MRI scan. Treatment usually includes antibiotics and using a back brace to reduce the mobility of the region.
Primary spinal cancer can happen, but is relatively rare. Metastatic disease is more likely. Spinal metastasis is the third most common site for cancer metastases (behind lung and liver). And note: the patient may not know s/he has a primary tumor!
The most common cancers that spread to the spine are breast, lung, thyroid, kidney and prostate.
( mnemonic: BLT with a Kosher Pickle)
Shown below is a bone scan with breast cancer metastasis in the spine (and elsewhere)
prostate cancer spread to the spine is shown:
The way to approach back pain, conceptually, is to recall that mechanical back pain (pain after too much activity) is usually benign and self limited; by contrast, visceral pain is much more worrisome. So the first questions should include asking about the timing (and inciting factors) of the pain. Also, inquiring about constitutional symptoms—general wellness, weight loss, fevers, sweat etc—and neurological deficits is helpful.
To hone in on the three diagnoses above it may be helpful to concentrate on the risk factors for the conditions. A compromised immune is obviously a risk factor for infection. A risk of primary cancer (eg smoking) is a risk for metastatic disease.