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   / @nabilebraheim  

Imaging in low back pain. If the patient is young, you don’t have to get X-rays in the first six to eight weeks, unless the patient has a history of significant trauma and you are suspecting a fracture, or the patient has a history of cancer, or has constitutional symptoms that indicate infection, or the patient is taking steroids for a long time and you suspect a compression fracture. If the patient has bladder and bowel symptoms and you suspect cauda equina, then you start with X-rays of the spine first. AP and lateral views of the lumbosacral spine should be the first study used to evaluate the lumbar spine. A lot of people come to the office with MRI without plain films. When do you get an X-ray? You get an X-ray if the patient has low back pain for six to eight weeks and is not getting better with conservative treatment. If the patient has red flags for infection, malignancy, or trauma, then you need to get X-rays early. Don’t wait six to eight weeks. Age is also a red flag. A 50-year-old patient should get an X-ray, unlike a 20-year-old where you may wait. If X-rays are negative, then you consider MRI. Get an MRI if you suspect malignancy or infection, in patients with neurological deficit, or in those with persistent back pain not improving after about three months of conservative treatment. MRI is also indicated for radiculopathy (leg pain, sciatica) not improving with conservative treatment, especially if symptoms are worsening. The problem with MRI is the high rate of false positives. These are not unique to the spine but can also be seen in the shoulder, hips, and ankle. In asymptomatic people, 25–37% will have abnormal discs. Sensitivity is very high, with few false negatives. But false positives are common: 35% of patients younger than 40, and 90% of patients older than 60, will show disc problems even if asymptomatic. This reduces specificity. MRI is also difficult in recurrent disc herniation. Gadolinium helps differentiate: recurrent disc herniation is cold and less vascular, while fibrosis lights up and is vascular. Surgery may help if it’s a true recurrent disc herniation, but not for fibrosis. After trauma, it’s difficult to know if the MRI finding is new or old. Always correlate imaging with history and exam. If a patient has sciatica, positive straight leg raise, neurological findings (weak big toe, decreased sensation on dorsum of foot = L5, lateral foot = S1), and the MRI matches the exam, there is 95% chance the patient will improve with surgery. Sciatica + positive SLR + positive MRI → 86% surgical success. Positive SLR only → 66%. MRI findings alone that do not match the clinical picture have no value. Common disc herniation levels: L4–L5 and L5–S1 (95%). Posterolateral (paracentral) herniation affects the traversing nerve root (L4–L5 → L5 root, L5–S1 → S1 root). Foraminal herniation (5–10%) affects the exiting nerve root (L5–S1 → L5 root). Stat MRI is needed in cases of neurological deficit or suspected cauda equina. Admit suspected cauda equina cases—do not send home. Stat MRI is also indicated in ankylosing spondylitis patients with minor trauma, to rule out unstable fracture. If MRI is contraindicated (pacemaker), do CT myelogram. If UMN signs are present with back pain, get cervical MRI. Bone scan may be used in rare cases of infection or tumor to show multiple lesions
.Quizzes
1. When should a young patient with low back pain get an X-ray?
A) Always within first week
B) Only if trauma, cancer, infection, or steroids are suspected
C) After three months of pain
D) Never indicated
Correct Answer: B
Explanation: Young patients usually don’t need X-rays unless red flags like trauma, cancer, infection, or chronic steroid use are present.
2. Which initial views are used for spine X-rays?
A) Oblique and flexion
B) AP and lateral
C) Lateral and oblique
D) Flexion and extension
Correct Answer: B
Explanation: The standard initial study is AP and lateral lumbosacral spine X-rays
3. MRI is indicated in which of the following?
A) Early routine screening
B) Suspected malignancy, infection, or neurological deficit
C) First line before X-rays
D) Always after one week of pain
Correct Answer: B
Explanation: MRI is indicated when red flags are present or symptoms persist despite conservative care.
4. Posterolateral disc herniation at L5–S1 compresses which root?
A) L4
B) L5
C) S1
D) S2
Correct Answer: C
Explanation: Posterolateral herniation compresses the traversing nerve root (L5–S1 → S1 root).
5. When is an emergency MRI required?
A) Chronic mild pain
B) After 6 months
C) Suspected cauda equina or acute neurological deficit
D) Routine radiculopathy
Correct Answer: C
Explanation: Stat MRI is critical in suspected cauda equina or acute neuro deficit cases.
6. Which imaging to use if MRI contraindicated (pacemaker)?
Explanation: CT myelogram is the alternative when MRI cannot be done.