Back Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Back. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Back Indian Medical PG Question 1: In a diving accident that severed the spinal cord below the sixth cervical vertebra, which of the following muscles would be affected?
- A. Deltoid
- B. Infraspinatus
- C. Levator Scapulae
- D. Latissimus Dorsi (Correct Answer)
Back Explanation: ***Latissimus Dorsi***
- The **latissimus dorsi muscle** is primarily innervated by the **thoracodorsal nerve**, which arises from the **C6, C7, and C8** nerve roots (with C7 and C8 being the predominant contributors) [1].
- A spinal cord injury below the sixth cervical vertebra would affect the C7 and C8 segments, thereby disrupting the nerve supply to the latissimus dorsi, leading to weakness or paralysis.
- This muscle is responsible for adduction, extension, and internal rotation of the shoulder.
*Deltoid*
- The **deltoid muscle** is innervated by the **axillary nerve**, which arises predominantly from the **C5 and C6** nerve roots.
- Since the injury is below the C6 vertebra, the upper cervical segments (C5 and C6) would remain intact above the level of injury.
- Therefore, deltoid function would be preserved.
*Infraspinatus*
- The **infraspinatus muscle** is innervated by the **suprascapular nerve**, which arises from the **C5 and C6** nerve roots.
- Similar to the deltoid, its innervation originates above the level of the spinal cord injury and would be spared.
*Levator Scapulae*
- The **levator scapulae muscle** receives innervation from the **C3, C4, and C5** spinal nerves, as well as contributions from the dorsal scapular nerve (predominantly C5).
- All of these nerve roots originate well above the level of injury, so this muscle would not be affected.
Back Indian Medical PG Question 2: In anterior spinal artery syndrome which of the following is spared
- A. Lateral spinothalamic tract
- B. Posterior columns (Correct Answer)
- C. Anterior spinothalamic tract
- D. Corticospinal tract
Back Explanation: ***Posterior columns***
- The **anterior spinal artery** supplies the anterior two-thirds of the spinal cord, leaving the **posterior columns** (dorsal columns) and often the dorsal horns with intact blood supply from the **posterior spinal arteries** [1].
- This sparing results in preserved **fine touch**, **vibration**, and **proprioception** (dorsal column function), which are the defining clinical features distinguishing it from other spinal cord syndromes [1].
*Lateral spinothalamic tract*
- This tract, responsible for **pain** and **temperature** sensation, is located within the territory supplied by the **anterior spinal artery** [3].
- Damage to this tract leads to bilateral loss of pain and temperature sensation below the level of the lesion [3].
*Anterior spinothalamic tract*
- The **anterior spinothalamic tract** mediates crude touch and pressure and is located anteriorly, within the vascular distribution of the **anterior spinal artery**.
- Injury to this tract contributes to the overall sensory deficit observed in anterior spinal artery syndrome.
*Corticospinal tract*
- The **corticospinal tracts** (also known as the pyramidal tracts), responsible for **voluntary motor control**, are situated in the anterior and lateral funiculi of the spinal cord [2].
- These tracts are supplied by the **anterior spinal artery**, leading to **bilateral motor paralysis** below the lesion in anterior spinal artery syndrome.
Back Indian Medical PG Question 3: Which artery is the major supply of the medial surface of the cerebral hemisphere?
- A. Anterior cerebral artery (Correct Answer)
- B. Posterior cerebral artery
- C. Middle cerebral artery
- D. Posterior inferior cerebellar artery
Back Explanation: ***Anterior cerebral artery***
- The **anterior cerebral artery (ACA)** is a primary branch of the internal carotid artery and is responsible for supplying blood to the **medial surface** of the frontal and parietal lobes of the cerebral hemispheres [1].
- It also supplies the **corpus callosum**, the superior aspect of the frontal and parietal lobes, and parts of the basal ganglia [1].
*Posterior cerebral artery*
- The **posterior cerebral artery (PCA)** primarily supplies the **occipital lobe** and the inferior part of the **temporal lobe** [1].
- It also provides blood to parts of the midbrain and the **thalamus** [1].
*Middle cerebral artery*
- The **middle cerebral artery (MCA)** is the largest cerebral artery and supplies most of the **lateral surface** of the cerebral hemispheres [1].
- It is crucial for the blood supply to the **motor and sensory cortices** for the face and upper limb, as well as language areas (Broca's and Wernicke's).
*Posterior inferior cerebellar artery*
- The **posterior inferior cerebellar artery (PICA)** is a branch of the **vertebral artery** and exclusively supplies the **cerebellum** and the lateral medulla.
- It is not involved in the blood supply to the cerebral hemispheres.
Back Indian Medical PG Question 4: Which of the following types of nerve fibers are primarily responsible for transmitting slow, dull, and chronic pain sensations?
- A. A-alpha fibers
- B. A-beta fibers
- C. A-delta fibers
- D. C fibers (Correct Answer)
Back Explanation: ***C fibers***
- These are **unmyelinated**, small-diameter nerve fibers that conduct impulses slowly (0.5-2 m/s).
- They are primarily responsible for transmitting **slow, dull, burning, or aching pain** (second pain or chronic pain), as well as temperature sensations and itch.
- Their slow conduction velocity results in the delayed, poorly localized pain sensation that persists after initial injury.
*A-alpha fibers*
- These are the **largest and fastest-conducting** myelinated nerve fibers (70-120 m/s).
- They are primarily involved in transmitting **proprioception** (sense of body position) and **motor information** to skeletal muscles.
- They do **not transmit pain** signals.
*A-beta fibers*
- These are **large, myelinated** fibers with a fast conduction velocity (30-70 m/s).
- They primarily transmit **touch and pressure sensations**, and can modulate pain perception through the gate control theory.
- They are **not nociceptors** and do not directly transmit pain.
*A-delta fibers*
- These are **small, myelinated** nerve fibers that conduct impulses at 12-30 m/s.
- They transmit **fast, sharp, well-localized pain** (first pain or acute pain) and cold sensations.
- While they do transmit pain, they are responsible for the **initial sharp pain**, not the slow, dull, chronic pain that defines C fiber function.
Back Indian Medical PG Question 5: A 22-year-old man develops the insidious onset of low back pain improved with exercise and worsened by rest. There is no history of diarrhea, conjunctivitis, urethritis, rash, or nail changes. On examination, the patient has loss of mobility with respect to lumbar flexion and extension. He has a kyphotic posture. Which test or group of tests would be most supportive of your suspected diagnosis?
- A. An elevated sedimentation rate, a mild anemia on CBC, positive HLA-B27 in blood and sclerosis of the sacroiliac joints on plain films of the back. (Correct Answer)
- B. Lumbosacral x-rays showing vertebral joint space narrowing and osteophyte formation at various levels.
- C. A positive rheumatoid factor, anti-CCP, and an elevated C-reactive protein level.
- D. MRI of the lumbosacral spine showing spinal compression fractures associated with bony destruction.
Back Explanation: **An elevated sedimentation rate, a mild anemia on CBC, positive HLA-B27 in blood and sclerosis of the sacroiliac joints on plain films of the back.**
- This constellation of findings is highly characteristic of **ankylosing spondylitis (AS)**, a seronegative spondyloarthropathy [1]. The patient's symptoms (insidious low back pain improving with exercise, worsened by rest, loss of lumbar mobility, kyphotic posture) are classic for AS [1].
- **HLA-B27** positivity is strongly associated with AS, and **sacroiliitis** (sclerosis of the sacroiliac joints) seen on imaging is a hallmark diagnostic feature [1]. **Elevated ESR** and **mild anemia** are common non-specific inflammatory markers seen in active AS.
*Lumbosacral x-rays showing vertebral joint space narrowing and osteophyte formation at various levels.*
- These findings are more indicative of **degenerative disc disease** or **osteoarthritis of the spine**, which typically worsens with activity and improves with rest, unlike the patient's symptoms [2].
- While common in older individuals, they do not explain the progressive inflammatory symptoms and characteristic posture of ankylosing spondylitis.
*A positive rheumatoid factor, anti-CCP, and an elevated C-reactive protein level.*
- **Positive rheumatoid factor (RF)** and **anti-CCP antibodies** are characteristic of **rheumatoid arthritis (RA)**, which primarily affects peripheral joints and is less commonly associated with the axial skeleton in this specific pattern.
- Although **elevated CRP** indicates inflammation, RF and anti-CCP are not typically found in ankylosing spondylitis, hence why it's categorized as a **seronegative spondyloarthropathy** [1].
*MRI of the lumbosacral spine showing spinal compression fractures associated with bony destruction.*
- **Spinal compression fractures with bony destruction** suggest conditions like metastatic cancer, severe osteoporosis, or severe infection (e.g., osteomyelitis), none of which align with the patient's insidious onset of inflammatory back pain and chronic progressive symptoms.
- These findings are acute and destructive, unlike the chronic inflammatory and structural changes seen in ankylosing spondylitis.
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