Back Practice Questions

Q: The spinal epidural space is largest at which vertebral level?

3rd lumbar vertebra. **Explanation:** The **spinal epidural space** is a potential space located between the dural sac and the vertebral canal's periosteum. Its dimensions vary significantly along the vertebral column due to the changing relationship between the spinal cord (and its coverings) and the bony canal. **Why D is correct:** The epidural space is widest in the **mid-lumbar region**, specifically at the **L3 level**, where it reaches a depth of approximately **5–6 mm**. This is primarily because the spinal cord ends (conus medullaris) at the L1-L2 level in adults. Below this point, the dural sac contains only the cauda equina, and the lumbar lordosis (anterior curvature) creates a larger posterior gap between the ligamentum flavum and the dura mater. **Analysis of Incorrect Options:** * **A (T12):** In the thoracic region, the epidural space is relatively narrow (approx. 3–5 mm) because the spinal cord occupies a larger proportion of the vertebral canal. * **B & C (L1 & L2):** These levels correspond to the **conus medullaris**. The spinal cord is still present here, filling more of the canal compared to the lower lumbar levels where only the nerve roots (cauda equina) remain. **NEET-PG High-Yield Pearls:** * **Contents of Epidural Space:** Internal vertebral venous plexus (Batson’s plexus), spinal nerve roots, loose areolar tissue, and adipose tissue. * **Clinical Significance:** The width of the space is crucial for **epidural anesthesia**. The L3-L4 or L4-L5 interspaces are preferred for entry because the space is largest and the risk of spinal cord injury is minimal. * **Negative Pressure:** The epidural space has a physiological negative pressure, which is used in the "loss of resistance" or "hanging drop" technique to identify the space during anesthesia. * **Narrowest Point:** The epidural space is narrowest in the cervical region (approx. 1–2 mm).

Q: During intervertebral disc prolapse, which part of the disc prolapses into the spinal canal?

Nucleus Pulposus. ### Explanation **Concept Overview:** The intervertebral disc consists of two primary components: the **Nucleus Pulposus** (a central, gelatinous core derived from the embryonic notochord) and the **Annulus Fibrosus** (a peripheral ring of dense collagenous fibers). In Intervertebral Disc Prolapse (IVDP), the Annulus Fibrosus undergoes degeneration or develops a tear (fissure). This allows the pressurized, semi-fluid **Nucleus Pulposus** to herniate or "prolapse" through the fibers into the spinal canal or intervertebral foramen, leading to nerve root compression. **Analysis of Options:** * **D. Nucleus Pulposus (Correct):** This is the actual material that herniates. It is rich in proteoglycans and water, acting as a shock absorber. When it prolapses, it causes both mechanical compression and chemical irritation of the nerve roots. * **A. Annulus Fibrosis:** This is the outer containment structure. While it may bulge (disc bulge), it is the *failure* of this structure that allows the nucleus to prolapse. * **B & C (Nucleus Fibrosis / Annular Pulposus):** These are anatomically incorrect terms created by mixing the names of the two disc components. They do not exist in human anatomy. **Clinical Pearls for NEET-PG:** * **Most Common Site:** L4-L5 or L5-S1 (Lumbar spine is most affected due to weight-bearing). * **Direction of Prolapse:** Usually **Postero-lateral**, as the Posterior Longitudinal Ligament (PLL) is thinner at the sides, making it the path of least resistance. * **Level of Compression:** A posterolateral prolapse usually compresses the **traversing nerve root** (e.g., an L4-L5 disc prolapse typically affects the L5 nerve root). * **Schmorl’s Nodes:** Prolapse of the nucleus pulposus vertically into the vertebral body.

Q: A 50-year-old man suffering from carcinoma of the prostate showed areas of sclerosis and collapse of T10 and T11 vertebrae. The most probable route of metastasis was through which of the following?

Internal vertebral plexus of veins. **Explanation:** The correct answer is **C. Internal vertebral plexus of veins (Batson’s Plexus).** **Why it is correct:** The spread of prostate cancer to the vertebral column (T10-T11) occurs via the **Batson’s venous plexus**. This is a network of valveless veins that connects the deep pelvic veins (prostatic venous plexus) with the internal vertebral venous plexus. Because these veins are **valveless**, changes in intra-abdominal or intra-thoracic pressure (e.g., coughing or straining) can cause retrograde blood flow. This allows malignant cells from pelvic organs like the prostate to bypass the caval system and reach the vertebral bodies directly, leading to osteoblastic (sclerotic) metastases. **Why other options are incorrect:** * **A. Sacral canal:** This is an anatomical space containing the cauda equina and meninges; it is not a primary vascular or lymphatic route for systemic metastasis. * **B. Lymphatic vessel:** While prostate cancer does spread via lymphatics (initially to internal iliac nodes), the specific pattern of vertebral collapse and multi-level spinal involvement is classically associated with the venous route. * **D. Superior rectal vein:** This vein drains into the portal venous system (inferior mesenteric vein). It is involved in the spread of rectal cancers to the liver, not prostate cancer to the spine. **NEET-PG High-Yield Pearls:** * **Batson’s Plexus:** Connects pelvic organs to the vertebral column and cranial cavity. It explains why prostate cancer often spreads to the spine and brain without lung involvement. * **Prostate Metastasis:** Characteristically **osteoblastic** (sclerotic), leading to increased bone density on X-ray. * **PSA (Prostate-Specific Antigen):** The primary biochemical marker used to monitor recurrence and metastasis.

Q: Which of the following statements is true about the Latissimus dorsi muscle?

Inserted into the bicipital groove of the humerus. The **Latissimus dorsi** (often called the "Climber's muscle") is a large, fan-shaped muscle of the back. Understanding its anatomy is high-yield for NEET-PG, particularly its insertion and neurovascular supply. ### **Explanation of Options:** * **Option B (Correct):** The Latissimus dorsi inserts into the **floor of the bicipital groove (intertubercular sulcus)** of the humerus. A useful mnemonic to remember the structures attaching here is *"A Lady between two Majors"*: the **L**atissimus dorsi (Lady) inserts into the floor, flanked by the Pectoralis **Major** on the lateral lip and the Teres **Major** on the medial lip. * **Option A (Incorrect):** It is supplied by the **Thoracodorsal nerve** (C6, C7, C8), which is a branch of the posterior cord of the brachial plexus [1]. The long thoracic nerve supplies the Serratus anterior. * **Option C (Incorrect):** While it is a large muscle, it is most commonly used in reconstructive surgery as a **pedicled flap for breast reconstruction** (LD flap) or to cover defects in the **axilla and chest wall**, rather than general back defects. * **Option D (Incorrect):** Its primary blood supply is the **Thoracodorsal artery** (a continuation of the subscapular artery) [1]. The lateral thoracic artery primarily supplies the Serratus anterior and the breast. ### **High-Yield Clinical Pearls for NEET-PG:** 1. **Actions:** It is a powerful **extensor, adductor, and medial rotator** of the humerus. It is essential for activities like swimming, rowing, and climbing. 2. **Triangle of Auscultation:** The superior border of the Latissimus dorsi forms the inferior boundary of this triangle (along with the trapezius and medial border of the scapula), where breath sounds are most clearly heard. 3. **Lumbar Triangle (Petit):** Its lateral border forms the posterior boundary of this triangle, which is a potential site for lumbar hernias.

Q: In a hunting accident, a 17-year-old boy was shot with an arrow that penetrated into his suboccipital triangle, injuring the suboccipital nerve between the vertebral artery and the posterior arch of the atlas. Which of the following muscles would be unaffected by such a lesion?

Splenius capitis. ### Explanation The **suboccipital nerve** is the dorsal ramus of the **C1 spinal nerve**. It enters the suboccipital triangle by passing between the vertebral artery (above) and the posterior arch of the atlas (below). It is primarily a motor nerve that supplies all the muscles forming the suboccipital triangle and the overlying semispinalis capitis. **Why Splenius Capitis is the Correct Answer:** The **Splenius capitis** is a member of the superficial layer of deep back muscles. It is located outside the suboccipital triangle and is innervated by the **lateral branches of the dorsal rami of middle cervical spinal nerves (C3–C4)**. Therefore, a lesion to the suboccipital nerve (C1) will not affect its function. **Analysis of Incorrect Options:** * **Rectus capitis posterior major:** Forms the medial boundary of the suboccipital triangle; supplied by the suboccipital nerve. * **Obliquus capitis superior:** Forms the lateral boundary of the suboccipital triangle; supplied by the suboccipital nerve. * **Semispinalis capitis:** While not a boundary of the triangle, it forms the **roof** of the suboccipital triangle and receives its motor supply from the suboccipital nerve (C1) and the greater occipital nerve (C2). **NEET-PG High-Yield Pearls:** 1. **Suboccipital Nerve (C1):** Uniquely, it usually has **no cutaneous distribution** (purely motor). 2. **Greater Occipital Nerve (C2):** The dorsal ramus of C2; it is primarily sensory and supplies the skin of the posterior scalp. 3. **Suboccipital Triangle Boundaries:** * *Superomedial:* Rectus capitis posterior major. * *Superolateral:* Obliquus capitis superior. * *Inferolateral:* Obliquus capitis inferior. 4. **Contents:** Third part of the vertebral artery and the suboccipital nerve (C1).

Question 1

The spinal epidural space is largest at which vertebral level?

Accepted Answer

3rd lumbar vertebra

Answer

12th thoracic vertebra

Answer

1st lumbar vertebra

Answer

2nd lumbar vertebra

Question 2

During intervertebral disc prolapse, which part of the disc prolapses into the spinal canal?

Accepted Answer

Nucleus Pulposus

Answer

Annulus Fibrosis

Answer

Nucleus Fibrosis

Answer

Annular Pulposus

Question 3

A 50-year-old man suffering from carcinoma of the prostate showed areas of sclerosis and collapse of T10 and T11 vertebrae. The most probable route of metastasis was through which of the following?

Accepted Answer

Internal vertebral plexus of veins

Answer

Sacral canal

Answer

Lymphatic vessel

Answer

Superior rectal

Question 4

Which of the following statements is true about the Latissimus dorsi muscle?

Accepted Answer

Inserted into the bicipital groove of the humerus

Answer

Nerve supply from the long thoracic nerve

Answer

Used to fill up back defects

Answer

Blood supply from the lateral thoracic artery

Question 5

In a hunting accident, a 17-year-old boy was shot with an arrow that penetrated into his suboccipital triangle, injuring the suboccipital nerve between the vertebral artery and the posterior arch of the atlas. Which of the following muscles would be unaffected by such a lesion?

Accepted Answer

Splenius capitis

Answer

Rectus capitis posterior major

Answer

Semispinalis capitis

Answer

Obliquus capitis superior

Back — MCQs

Back — MCQs

On this page

Practice by Chapter

Want unlimited practice?