Spine Flashcards
Back pain is a common, self-limited condition in many people. Discitis, cancer and cauda equine 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 are found in the spine. Next, name some questions a physician might ask to help detect the 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.
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)
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.
A so-called herniated disc may compress a nerve root and cause radicular complaints/findings. What are the classic motor and sensory findings of involvement of L4? What are the classic sensory and motor findings of involvement of L5? What are the classic findings of involvement of S1? Why, given that an MRI can localize the disc herniation, if present, should/must a student know the motor and sensory findings of each nerve root level? Suggest a medical rationale for not obtaining an MRI in a patient with low back pain and no neurological features. Forget about the cost of the MRI itself: why might a physician considering only the best medical interests of his or her patient choose to omit an MRI?
An L4 disc herniation often presents with quadriceps weakness (if any), medial knee and shin sensory loss and pain distributed down the anterior thigh.
An L5 disc herniation classically presents with weakness in extension of the big toe (EHL), sensory loss in the big toe, and pain distributed down the back of the thigh and lateral calf.
An S1 disc herniation classically presents with weakness of the gastocnemius causing impaired ankle plantar flexion, sensory loss of the lateral foot and pain distributed down the back of the calf. The motor findings are more reliable than the sensory.
We need to be able to match the likely “positive” findings on MRI with the findings on exam.
A Penn med grad, Scott Boden among others has shown that many asymptomatic people have positive MRIs hence the radiologist will not say that all findings are necessarily pathological; rather he or she will say “clinical correlation suggested”. By knowing what each lesion might cause you can make that correlation.
Thus, there is a strong medical rationale for not obtaining an MRI in a patient with low back pain and no neurological features: MRIs of healthy patients can lead to false positives and incorrect diagnoses that cause unnecessary stress, psychosocial difficulties and even psychiatric morbidity AND MOST ESPECIALLY OVERTREATMENT.
As noted above, many asymptomatic people have positive MRIs. Accordingly, the purpose of the MRI is not to screen (for it will fail on that account by picking up too much) but rather to plan the next step in treatment.
MRI ABOVE: Does this person have pain? If so, does it match?
MRI is needed primarily as surgical (or injection) planning investigation, a “gateway test”, one might say, to many perhaps unnecessary (one also might say) procedures.
If all patients with back pain were to get an MRI there is a great chance that more (unnecessary) back surgery will be done.
The interested student is encouraged to consult the medical literature on the following points: first, the success rates of surgical treatment of back pain; the variability of the rates of back surgery by region of the country (suggesting non-scientific indications, one might say); and the cost of such surgical treatment. The answers are “low”, “high” and “high” in case you could not guess…
(In the scheme of things, MRI is almost free; that is, the dollar cost of the test itself is a trivial to the cost of the treatment it could invoke. Don’t be fooled by the list price–what is charged–but concentrate on what is actually paid.)
What is neurogenic claudication (contrasted with vascular claudication)?
Basics: nerves don’t like pressure. Sit like this too long and bad things happen to your common peroneal nerve.
Next: the word “Claudication” (Latin: limp) refers to painful cramping and/or weakness. (The name “Claude” means “lame one”; “Clawed” means “scratched one”)
It is important to differentiate neurogenic from vascular claudication. The term “neurogenic” refers to the fact that the problem originates from a problem involving the nerves, but the common theme is ischemia: in classic claudication, the muscles are ischemic; in neurogenic, it is the nerves.
Neurogenic claudication is caused by spinal stenosis (itself caused by bone overgrowth, disc protrusion, facet arthritis, or soft tissue proliferation)
As shown, with spinal stenosis the central canal space is much reduced (putting pressure on the nerves)
Neurogenic claudication can cause bilateral or unilateral lateral calf, buttock, or thigh discomfort, pain, and/or weakness. In some patients, it is precipitated by walking or prolonged standing. The pain is typically relieved by flexion of the waist. The cause is believed to be ischemia of the lumbosacral nerve roots secondary to compression from structures such as hypertrophied facets, ligamentum flavum, bone spurs, scar tissue, and bulging or herniated discs.
Vascular claudication is due to a circulatory problem. Bad arterial flow leads to ischemia of the calf muscles. Angiography is definitive and measuring the ABI (the Ankle: Brachial Index), ie the ratio of the leg and arm blood pressures) is a good screening measure.
Neurogenic claudication can be differentiated from vascular claudication, by the following features:
Neurogenic pain is more proximal, Neurogenic pain not always uniformly present Neurogenic pain can be present at rest Neurogenic pain is not dose dependent (ie blocks walked) and may be relieved by postural changes (leaning forward to make more space in the spine---eg bike riding is fine whereas walking is painful). Basically: vascular claudication causes 'dose dependent calf pain'---walk more, hurt more; stop, feel better. All the time, every time.
What is idiopathic scoliosis and what is its relationship to back pain?
Scoliosis is a lateral curvature of the spine that is usually accompanied by rotation. Idiopathic scoliosis does not have a clear causal agent –” Idiopathic” = “we don’t know why you have it”.
Labeling a condition idiopathic is a process of exclusion, ie excluding all of the known causes . Adolescents with idiopathic scoliosis (“adolescent type”) may present in several ways. In some patients, scoliosis is incidentally found on physical examination. Others have complaints related to the deformity that is caused, such as asymmetry of the shoulders, flank creases, hips, scapulae, or breasts. Still others present because an abnormality was noted during a scoliosis screening at school.
Most patients with adolescent idiopathic scoliosis have little, if any, functional limitation or pain. In practice, the presence of scoliosis not be consider an adequate explanation for acute or severe back pain—at least in the sense that if somebody presents with idiopathic scoliosis and pain, the clinician must not simply attribute the pain to the idiopathic scoliosis.
one not that rare cause of pain that is worth knowing (at least that it exists) is Spondylolysis: a stress fracture in one of the pars in the vertebrae.
Less common causes include tumor, infection, and in patients with sickle cell disease, sickle crisis.
