Back Practice Questions

Q: Which of the following muscles causes flexion of the lumbar spine?

Psoas major. **Explanation:** The **Psoas major** is a long, fusiform muscle located in the lateral aspect of the lumbar region. Its origin spans from the transverse processes and bodies of T12 to L5 vertebrae. While its primary action is flexion of the hip (thigh), when the femur is fixed, bilateral contraction of the psoas major pulls the lumbar vertebrae anteriorly and inferiorly, resulting in **flexion of the lumbar spine** (or assisting in rising from a supine position). **Analysis of Options:** * **A. Erector spinae:** This is a group of muscles (iliocostalis, longissimus, spinalis) that acts as the primary **extensor** of the vertebral column. They help maintain an erect posture and control forward flexion via eccentric contraction. * **B & C. External and Internal Obliques:** While these abdominal muscles are involved in trunk flexion, their primary role in the context of the spine is **rotation and lateral flexion**. When acting bilaterally, they flex the trunk primarily at the thoracic-lumbar junction and compress abdominal viscera, but the Psoas major is the specific deep muscle associated with direct lumbar vertebral flexion. **High-Yield Clinical Pearls for NEET-PG:** * **Psoas Sign:** Pain on passive extension of the hip is a classic sign of **Appendicitis**, as the inflamed appendix may lie over the right psoas muscle. * **Psoas Abscess:** Infections (like Pott’s disease/Tuberculosis of the spine) can track down the psoas fascia and present as a swelling in the groin (below the inguinal ligament). * **Innervation:** Psoas major is supplied by the anterior rami of **L1, L2, and L3** nerves.

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).

Q: The subarachnoid space ends at which vertebral level?

S2. **Explanation:** The spinal cord is enveloped by three meningeal layers: the dura mater, arachnoid mater, and pia mater. The **subarachnoid space**, which contains cerebrospinal fluid (CSF), is the area between the arachnoid and pia mater [1]. While the spinal cord (conus medullaris) ends at the level of **L1-L2** in adults, the dural sac and the underlying subarachnoid space continue further down to the level of the **second sacral vertebra (S2)**. At this point, the dura and arachnoid mater fuse and terminate, blending with the filum terminale to form the coccygeal ligament. **Analysis of Options:** * **D12:** This is the level where the spinal cord begins its terminal taper; it is too superior for the termination of the subarachnoid space. * **L2:** This is the level where the **spinal cord (conus medullaris) ends** in adults. The subarachnoid space continues below this level to form the lumbar cistern. * **L5:** While the subarachnoid space passes through this level, it does not terminate here. * **S2 (Correct):** This is the anatomical landmark where the dural sac and subarachnoid space end. **Clinical Pearls & High-Yield Facts:** * **Lumbar Puncture (LP):** Performed between **L3-L4 or L4-L5** to ensure the needle enters the subarachnoid space (lumbar cistern) while avoiding injury to the spinal cord. * **Pediatric Anatomy:** In newborns, the spinal cord ends lower, at the **L3** level, but the subarachnoid space still ends at **S2**. * **Filum Terminale:** The *Filum Terminale Internum* (pia mater) ends at S2, while the *Filum Terminale Externum* (dura mater) attaches to the back of the coccyx.

Q: A 34-year-old pregnant woman experiencing considerable pain during labor is to undergo a caudal epidural block within the sacral canal. What are the most important bony landmarks used for the administration of this anesthesia?

Sacral cornua. The **caudal epidural block** involves the injection of anesthetic medication into the **sacral canal** via the **sacral hiatus**. The sacral hiatus is a U-shaped opening at the distal end of the sacrum, formed by the failure of the 5th sacral vertebral laminae to fuse in the midline. The **sacral cornua** (sacral horns) are the most important bony landmarks for identifying this site. They represent the inferior articular processes of the S5 vertebra and are located on either side of the sacral hiatus. By palpating these two bony prominences, a clinician can accurately locate the hiatus to insert the needle into the epidural space. **Analysis of Incorrect Options:** * **Ischial tuberosities:** These are the "sitting bones" of the pelvis. While used as landmarks for pudendal nerve blocks (transvaginal approach), they are too inferior and lateral to guide a sacral canal injection. * **Ischial spines:** These serve as the landmark for a **pudendal nerve block** [1]. The needle is directed toward the spine to anesthetize the nerve as it crosses the sacrospinous ligament [2]. * **Posterior superior iliac spines (PSIS):** These are used to identify the level of the S2 vertebra (the "dimples of Venus"). While they help orient the clinician to the sacral region, they do not mark the entry point for caudal anesthesia. **High-Yield Facts for NEET-PG:** * **Contents of Sacral Canal:** Filum terminale externum, spinal nerves (S1-S5 and Co1), and the coccygeal nerve. * **Dural Sac Termination:** In adults, the dural sac ends at the level of **S2**. This is clinically vital because a needle inserted too far superiorly into the sacral canal could cause an accidental subarachnoid injection. * **Caudal Block Use:** Commonly used in pediatrics and for obstetric procedures (labor pain) to anesthetize the pelvic floor and perineum [3].

Q: In children, the spinal cord typically terminates at the lower border of which vertebral level?

L3. ### Explanation The spinal cord terminates at different levels depending on the age of the individual due to the differential growth rates of the vertebral column and the spinal cord (a phenomenon known as the **"ascent of the cord"**). **1. Why L3 is Correct:** In **neonates and infants**, the spinal cord ends at the level of the **L3 vertebra**. During early fetal development, the spinal cord occupies the entire length of the vertebral canal. However, as the vertebral column grows much faster than the neural tissue, the distal end of the cord (conus medullaris) appears to "move up." By birth, it typically reaches the lower border of L3. **2. Analysis of Incorrect Options:** * **A & B (L1/L2):** These are the termination levels in **adults** [1]. In most adults, the spinal cord ends at the lower border of **L1** or the L1-L2 intervertebral disc [1]. Choosing these for a child would be incorrect and clinically dangerous during procedures. * **D (L4):** This level is too low for a term infant. While the cord is at the sacral level in early fetal life (8 weeks), it has already ascended past L4 by the time of birth. **3. Clinical Pearls & High-Yield Facts:** * **Lumbar Puncture (LP) Safety:** To avoid needle injury to the spinal cord, an LP is performed at the **L3-L4 or L4-L5** space in adults, but must be performed lower (usually **L4-L5 or L5-S1**) in infants. * **Subarachnoid Space:** While the cord ends at L1 (adult) or L3 (child), the subarachnoid space (dural sac) ends at **S2** in both [1]. * **Filum Terminale:** The fibrous extension of the pia mater that anchors the cord to the coccyx is called the filum terminale [1]. * **Tethered Cord Syndrome:** A clinical condition where the conus medullaris is abnormally low, often associated with spina bifida.

Q: A 38-year-old woman with a long history of shoulder pain is admitted to a hospital for surgery. Which of the following muscles becomes ischemic soon after ligation of the superficial or ascending branch of the transverse cervical artery?

Trapezius. **Explanation:** The **transverse cervical artery** (a branch of the thyrocervical trunk) typically divides at the anterior border of the trapezius into a **superficial branch** (also called the ascending branch) and a **deep branch** (also called the dorsal scapular artery). 1. **Why Trapezius is correct:** The superficial branch of the transverse cervical artery is the primary vascular supply to the **trapezius muscle**. It travels on the deep surface of the muscle alongside the accessory nerve (CN XI). Therefore, ligation of this branch leads to ischemia of the trapezius. 2. **Why other options are incorrect:** * **Latissimus dorsi:** This muscle is primarily supplied by the **thoracodorsal artery** (a continuation of the subscapular artery) [1]. * **Multifidus:** These are deep intrinsic back muscles supplied by the posterior rami of spinal nerves and the **segmental posterior intercostal arteries**. * **Rhomboid major:** This muscle (along with the levator scapulae) is primarily supplied by the **deep branch** of the transverse cervical artery (dorsal scapular artery). While the superficial branch supplies the trapezius, the deep branch runs deep to the rhomboids. **High-Yield Clinical Pearls for NEET-PG:** * **Vascular Variation:** In about 30% of individuals, the dorsal scapular artery arises directly from the subclavian artery rather than as a deep branch of the transverse cervical artery. * **Nerve Association:** The superficial branch of the transverse cervical artery is the companion vessel to the **Spinal Accessory Nerve (CN XI)**. * **Surgical Significance:** During radical neck dissection, preserving these vessels is crucial to maintain the viability of the trapezius muscle if it is being used for reconstructive flaps.

Q: What is the normal curvature of the lumbar spine?

Lordosis. The vertebral column exhibits distinct curvatures that provide balance and shock absorption. These are categorized into **primary** (present at birth) and **secondary** (develop postnatally) curvatures. ### **Explanation of the Correct Answer** **B. Lordosis:** The normal curvature of the lumbar spine is **Lordosis**, which is a secondary, compensatory curvature characterized by an **anterior convexity** (posterior concavity). It develops when an infant begins to walk and assume an upright posture. The cervical spine also exhibits lordosis, which develops earlier when the infant begins to lift their head. ### **Analysis of Incorrect Options** * **A. Kyphosis:** This is a curvature with a **posterior convexity**. Normal (physiological) kyphosis is seen in the **thoracic and sacral** regions. These are primary curvatures, meaning they are present during fetal life. * **C. Scoliosis:** This refers to an **abnormal lateral curvature** of the spine, often associated with rotation of the vertebrae. It is never a normal physiological finding. * **D. Gibus (Gibbus Deformity):** This is a form of structural kyphosis where a single vertebra collapses (often due to **Tuberculosis of the spine/Pott’s disease**), leading to a sharp, angular deformity of the back. ### **High-Yield Clinical Pearls for NEET-PG** * **Primary Curvatures:** Thoracic and Sacral (Mnemonic: **T**he **S**ame as fetus). * **Secondary Curvatures:** Cervical (develops at ~3-4 months) and Lumbar (develops at ~12-18 months). * **Hyperlordosis:** Often seen in late pregnancy or marked obesity as the center of gravity shifts. * **Ligamentum Flavum:** Connects the laminae of adjacent vertebrae and helps maintain the upright posture.

Q: The nucleus pulposus is a component of which anatomical structure?

Intervertebral disc. **Explanation:** The **intervertebral disc (IVD)** is a fibrocartilaginous joint (symphysis) located between adjacent vertebral bodies. It consists of two primary components: 1. **Nucleus Pulposus (Correct):** The inner, gelatinous core derived from the embryonic **notochord**. It is rich in water, proteoglycans, and collagen fibers, acting as a shock absorber to distribute hydraulic pressure. 2. **Anulus Fibrosus:** The outer, peripheral part consisting of concentric lamellae of fibrocartilage that contains the nucleus pulposus. **Analysis of Incorrect Options:** * **B. Medial Meniscus:** This is a C-shaped fibrocartilage structure within the knee joint. While it also acts as a shock absorber, it does not contain a nucleus pulposus. * **C. Brain:** While the brain contains "nuclei" (clusters of neurons), the *nucleus pulposus* is strictly a musculoskeletal component. * **D. Vestibulocochlear region:** This refers to the inner ear. While the term "nucleus" exists in the brainstem for the vestibulocochlear nerve (CN VIII), it is unrelated to the pulposus structure. **Clinical Pearls for NEET-PG:** * **Herniation:** A "slipped disc" typically involves the nucleus pulposus protruding through a tear in the anulus fibrosus, most commonly in a **posterolateral** direction (due to the thinness of the posterior longitudinal ligament) [1]. * **Level:** Disc herniation usually affects the nerve root numbered one below the disc level (e.g., L4-L5 disc herniation affects the L5 nerve root) [1]. * **Water Content:** The nucleus pulposus dehydrates with age, leading to a loss of height and increased risk of injury [1].

Question 1

Which of the following muscles causes flexion of the lumbar spine?

Accepted Answer

Psoas major

Answer

Erector spinae

Answer

External obliques muscle

Answer

Internal oblique muscle

Question 2

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

Question 3

The subarachnoid space ends at which vertebral level?

Accepted Answer

S2

Answer

D12

Answer

L2

Answer

L5

Question 4

A 34-year-old pregnant woman experiencing considerable pain during labor is to undergo a caudal epidural block within the sacral canal. What are the most important bony landmarks used for the administration of this anesthesia?

Accepted Answer

Sacral cornua

Answer

Ischial tuberosities

Answer

Ischial spines

Answer

Posterior superior iliac spines

Question 5

In children, the spinal cord typically terminates at the lower border of which vertebral level?

Accepted Answer

L3

Answer

L1

Answer

L2

Answer

L4

Question 6

A 38-year-old woman with a long history of shoulder pain is admitted to a hospital for surgery. Which of the following muscles becomes ischemic soon after ligation of the superficial or ascending branch of the transverse cervical artery?

Accepted Answer

Trapezius

Answer

Latissimus dorsi

Answer

Multifidus

Answer

Rhomboid major

Question 7

Which of the following is a dorsal ramus of a spinal nerve?

Accepted Answer

Greater occipital nerve

Answer

Supraclavicular nerve

Answer

Transverse cervical nerve

Answer

Great auricular nerve

Question 8

Which of the following is NOT a characteristic of a typical cervical vertebra?

Accepted Answer

Has a large vertebral body

Answer

Has a triangular vertebral canal

Answer

Has foramen transversarium

Answer

Superior articular facet is directed backwards and upwards

Question 9

What is the normal curvature of the lumbar spine?

Accepted Answer

Lordosis

Answer

Kyphosis

Answer

Scoliosis

Answer

Gibus

Question 10

The nucleus pulposus is a component of which anatomical structure?

Accepted Answer

Intervertebral disc

Answer

Medial meniscus

Answer

Brain

Answer

Vestibulocochlear region

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