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NBME 20 Answers

nbme20/Block 2/Question#31

A 25-year-old man comes to the physician 8 hours ...

Rupture of an intervertebral disc

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not sure if you all have seen the uworld chart Ddx for back pain but i found it really helpful. ill summarize it here: condition (key feature): degernative osteoarthritis (positional relieved with rest), radiculopathy - disc herniation(radiates to the leg aka lasegue sign), spinal stenossi(pain with standing), spondylorpathy(relieved with exercise, and ddominant at rest), spinal metastasis(constant pain, worse at night, not relieved by positional changes), vertebral osteomyelitis(focal tenderness, acute back pain, and fever), aortic dissection (severe restrosternal pain, radiating to the back)

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submitted by usmle11a(23),

ok here is how i broke it down: a) wrong because most cases would have some risk factor "old female ..." b) "deltoid" c) under pressure it can burst and frankly it is mentioned in FA as a very common cause. D) i think it would need something like a posterior dislocation of hip. e) would probsbly not cause neruo S $S

Since the pain is radicular, a disc herniation is most likely.

charcot_bouchard  Why it cant be a lumbar vertebra fracture +  
whoissaad  @charcot The patient is young and doesn't have any risk factors for weak bones. Also, disc herniation is a common problem in the young. The disc gets fibrosed and stiff in the elderly so they have less chance for disc herniation. So basically age was the key to answering this question. +1  

does some mind explaining why this isn't a tear in the sciatic nerve?

sugaplum  It is a very thick nerve, so I think it is hard to tear without physically cutting it. Also if it tore you would have tibial and common fibular nerve symptoms as well. You would see sensory numbness and tingling along the dermatome also the mechanism of injury is focused on spine so a disc rupture is more likely +  

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submitted by step1soon(17),

Sciatica is a debilitating condition in which the patient experiences pain and/or paresthesias in the distribution of the sciatic nerve or an associated lumbosacral nerve root. Often, a common mistake is referring to any low back pain or radicular leg pain as sciatica. Sciatica is specific to the pain that is a direct result of sciatic nerve or sciatic nerve root pathology. The sciatic nerve is made up of the L4 through S2 nerve roots which coalesce at the pelvis to form the sciatic nerve. At up to 2 cm in diameter, the sciatic nerve is easily the largest nerve in the body. Sciatica pain often is worsened with flexion of the lumbar spine, twisting, bending, or coughing. The sciatic nerve provides direct motor function to the hamstrings, lower extremity adductors, and indirect motor function to the calf muscles, anterior lower leg muscles, and some intrinsic foot muscles. Also, indirectly through its terminal branches, the sciatic nerve provides sensation to the posterior and lateral lower leg as well as the plantar foot.

Any condition that may structurally impact or compress the sciatic nerve may cause sciatica symptoms. The most common cause of sciatica is a herniated or bulging lumbar intervertebral disc. In the elderly population, lumbar spinal stenosis may cause these symptoms as well. Spondylolisthesis or a relative misalignment of one vertebra relative to another may also result in sciatic symptoms. Additionally, lumbar or pelvic muscular spasm and/or inflammation may impinge a lumbar or sacral nerve root causing sciatic symptoms. A spinal or paraspinal mass including malignancy, epidural hematoma, or epidural abscess may also cause a mass-like effect and sciatica symptoms.