Back — MCQs

Back Indian Medical PG Practice Questions and MCQs

Question 11: Which of the following muscles causes flexion of the lumbar spine?

A. Erector spinae
B. External obliques muscle
C. Internal oblique muscle
D. Psoas major (Correct Answer)

Explanation: **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.

Question 12: 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?

A. Rectus capitis posterior major
B. Semispinalis capitis
C. Splenius capitis (Correct Answer)
D. Obliquus capitis superior

Explanation: ### 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 13: The subarachnoid space ends at which vertebral level?

A. D12
B. L2
C. L5
D. S2 (Correct Answer)

Explanation: **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.

Question 14: 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?

A. Ischial tuberosities
B. Ischial spines
C. Posterior superior iliac spines
D. Sacral cornua (Correct Answer)

Explanation: 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].

Question 15: In children, the spinal cord typically terminates at the lower border of which vertebral level?

A. L1
B. L2
C. L3 (Correct Answer)
D. L4

Explanation: ### 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.

Question 16: 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?

A. Latissimus dorsi
B. Multifidus
C. Trapezius (Correct Answer)
D. Rhomboid major

Explanation: **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.

Question 17: Which of the following is a dorsal ramus of a spinal nerve?

A. Supraclavicular nerve
B. Transverse cervical nerve
C. Great auricular nerve
D. Greater occipital nerve (Correct Answer)

Explanation: The spinal nerves divide into **dorsal (posterior) rami** and **ventral (anterior) rami**. In the cervical region, the ventral rami form the cervical and brachial plexuses, supplying the skin and muscles of the anterior neck and limbs. The dorsal rami supply the deep muscles of the back and the skin of the posterior aspect of the head and trunk. ### **Why the Correct Answer is Right:** * **Greater Occipital Nerve:** This is the **medial branch of the dorsal ramus of the C2 spinal nerve**. It pierces the trapezius muscle to provide sensory innervation to the scalp of the occipital region up to the vertex. It is the largest purely cutaneous dorsal ramus in the body. ### **Why the Other Options are Wrong:** * **Supraclavicular nerve (C3, C4):** This is a branch of the **cervical plexus (ventral rami)**. It supplies the skin over the shoulder and upper chest. * **Transverse cervical nerve (C2, C3):** This is a branch of the **cervical plexus (ventral rami)**. It provides sensation to the anterior and lateral parts of the neck. * **Great auricular nerve (C2, C3):** This is a branch of the **cervical plexus (ventral rami)**. It supplies the skin over the parotid gland, the posterior aspect of the auricle, and the angle of the mandible. ### **High-Yield Clinical Pearls for NEET-PG:** * **Suboccipital Nerve:** The dorsal ramus of **C1** is called the suboccipital nerve. Unlike other dorsal rami, it is **purely motor** and supplies the muscles of the suboccipital triangle. * **Third Occipital Nerve:** The dorsal ramus of **C3** (medial branch) supplies the skin of the lower part of the back of the head. * **Erb’s Point:** The four cutaneous branches of the cervical plexus (Supraclavicular, Transverse cervical, Great auricular, and Lesser occipital) all emerge from the posterior border of the sternocleidomastoid at this point. Note that the **Lesser Occipital nerve** is a ventral ramus (C2), whereas the **Greater Occipital** is a dorsal ramus (C2).

Question 18: Which of the following is NOT a characteristic of a typical cervical vertebra?

A. Has a triangular vertebral canal
B. Has foramen transversarium
C. Superior articular facet is directed backwards and upwards
D. Has a large vertebral body (Correct Answer)

Explanation: ### Explanation The correct answer is **D. Has a large vertebral body**. **1. Why the Correct Answer is Right:** Cervical vertebrae (C3–C6) are designed for mobility rather than weight-bearing. Consequently, they have the **smallest vertebral bodies** of all the true vertebrae. The body is small, broader from side to side than anteroposteriorly, and possesses **uncinate processes** on the superior lateral margins. Large, heavy vertebral bodies are a characteristic feature of **Lumbar vertebrae**, which must support the weight of the entire upper body. **2. Analysis of Incorrect Options:** * **A. Triangular vertebral canal:** This is a **true** characteristic. The cervical vertebral canal is large and triangular to accommodate the cervical enlargement of the spinal cord. * **B. Foramen transversarium:** This is the **pathognomonic feature** of all cervical vertebrae. These foramina in the transverse processes transmit the vertebral artery (except in C7, where it transmits only accessory veins), vertebral veins, and sympathetic plexus. * **C. Superior articular facet direction:** This is **true**. The facets are relatively flat and directed **backwards and upwards** (posterosuperiorly), while inferior facets face forwards and downwards. This orientation allows for a wide range of flexion, extension, and lateral rotation. **3. Clinical Pearls & High-Yield Facts:** * **Bifid Spinous Process:** Typical cervical vertebrae (C2–C6) usually have a short, bifid spinous process. * **C7 (Vertebra Prominens):** It is atypical because it has a long, non-bifid spine and the vertebral artery does *not* pass through its foramen transversarium. * **Chassaignac’s Tubercle:** The anterior tubercle of the C6 transverse process is large and used as a landmark to compress the carotid artery. * **Uncovertebral joints (Joints of Luschka):** Found between the uncinate processes; these are common sites for osteophyte formation, which may compress spinal nerves.

Question 19: What is the normal curvature of the lumbar spine?

A. Kyphosis
B. Lordosis (Correct Answer)
C. Scoliosis
D. Gibus

Explanation: 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.

Question 20: The nucleus pulposus is a component of which anatomical structure?

A. Intervertebral disc (Correct Answer)
B. Medial meniscus
C. Brain
D. Vestibulocochlear region

Explanation: **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].

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