Back Practice Questions

Q: A 32-year-old male elite athlete felt severe pain radiating to the posterior aspect of his right thigh and leg during an intense training session involving heavy weights. MRI revealed a ruptured L4/L5 intervertebral disk. Which nerve is most probably affected?

L5. ### Explanation **1. Why L5 is the Correct Answer:** In the lumbar spine, the nerve roots exit the vertebral canal **below** their corresponding vertebrae through the intervertebral foramina. However, due to the oblique course of the cauda equina, a **posterolateral (paracentral) disc herniation**—the most common type—typically spares the nerve root exiting at that level and instead compresses the **traversing nerve root** (the one exiting at the level below) [1]. In this case, at the **L4/L5 level**, the L4 nerve root has already exited above the disc. The **L5 nerve root** is the one currently traversing the L4/L5 disc space to reach its exit point below the L5 vertebra [1]. Therefore, an L4/L5 herniation most commonly affects the **L5 nerve root**. This presents clinically as pain radiating down the posterior/lateral thigh and leg (sciatica) [1]. **2. Why Other Options are Incorrect:** * **L4 (Option B):** The L4 nerve root exits the L4/L5 foramen *above* the disc level. It would only be affected by a rare "far lateral" or "foraminal" disc herniation, not a standard posterolateral rupture. * **L2 & L3 (Options C & A):** These nerve roots exit at much higher levels (L2/L3 and L3/L4 respectively) and are anatomically distant from an L4/L5 disc rupture. **3. NEET-PG High-Yield Pearls:** * **Rule of Thumb:** A posterolateral disc herniation affects the **lower** of the two vertebrae involved (e.g., L5/S1 affects S1). * **L5 Nerve Root Compression:** Look for weakness in **big toe dorsiflexion** (Extensor Hallucis Longus) and sensory loss on the dorsal aspect of the foot [1]. * **S1 Nerve Root Compression:** Look for loss of the **Ankle Jerk reflex** and weakness in plantar flexion. * **Most Common Site:** L4/L5 and L5/S1 are the most frequent sites of lumbar disc herniation [1].

Q: Which muscle, anatomically considered a back muscle, is functionally related to the thorax?

Latissimus dorsi. **Explanation:** The **Latissimus dorsi** is anatomically classified as a superficial extrinsic back muscle because of its location and origin. However, it is functionally related to the thorax (and upper limb) due to its insertion into the floor of the bicipital groove of the humerus. It acts as a powerful adductor, extensor, and internal rotator of the arm. Crucially, it is often referred to as the **"Climbing Muscle"** and the **"Coughing Muscle"**; during forceful expiration (like coughing or sneezing), it compresses the posterior aspect of the thorax, assisting in the expulsion of air. [1] **Analysis of Options:** * **Rhomboid (Major/Minor):** These are extrinsic back muscles that primarily function to retract and rotate the scapula, relating them functionally to the **scapulothoracic joint**, not the thoracic cage itself. * **Trapezius:** A superficial back muscle that acts on the pectoral girdle (scapula and clavicle) to rotate, elevate, and depress the shoulder. * **Levator costae:** While these muscles are located in the back and act on the ribs (elevating them), they are anatomically classified as **deep/intrinsic muscles of the thorax** (or posterior thoracic wall), not primarily as "back muscles" in the context of this functional distinction. **High-Yield Pearls for NEET-PG:** * **Nerve Supply:** Thoracodorsal nerve (C6, C7, C8). [1] * **Clinical Significance:** The Latissimus dorsi forms the posterior boundary of the **Triangle of Petit** (Lumbar triangle) and the posterior fold of the axilla. [1] * **Surgical Use:** It is commonly used as a pedicled flap in reconstructive breast surgery.

Q: A 42-year-old woman with metastatic breast cancer is known to have tumors in the intervertebral foramina between the fourth and fifth cervical vertebrae and between the fourth and fifth thoracic vertebrae. Which of the following spinal nerves may be damaged?

Fifth cervical and fourth thoracic nerves. ### Explanation The core concept tested here is the **relationship between spinal nerves and their corresponding vertebrae**, which differs between the cervical and thoracic regions. **1. Why Option D is Correct:** * **Cervical Region:** There are 8 cervical spinal nerves but only 7 cervical vertebrae. In this region, spinal nerves **C1 through C7 exit ABOVE** their numerically corresponding vertebrae. Therefore, the nerve passing through the intervertebral foramen between C4 and C5 is the **C5 nerve** [1]. * **Thoracic/Lumbar Region:** Starting from T1 downwards, the pattern shifts because the C8 nerve exits between C7 and T1. Consequently, all thoracic, lumbar, and sacral nerves **exit BELOW** their corresponding vertebrae. Therefore, the nerve passing through the intervertebral foramen between T4 and T5 is the **T4 nerve** [1]. **2. Analysis of Incorrect Options:** * **Option A & C:** Incorrect because the nerve between C4-C5 is C5, not C4. * **Option B:** Incorrect because the nerve between T4-T5 is T4, not T5. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **The "C8" Rule:** The C8 nerve is the "transition" nerve; it exits below C7 and above T1. This is why there are 8 cervical nerves despite only 7 cervical vertebrae. * **Disc Prolapse Rule:** * In the **cervical spine**, a posterolateral disc prolapse typically compresses the nerve root exiting at that level (e.g., C5-C6 disc affects C6 nerve) [1]. * In the **lumbar spine**, a posterolateral disc prolapse usually compresses the *traversing* nerve root (the one exiting one level below). For example, an L4-L5 disc herniation typically affects the L5 nerve root. * **Numbering:** Remember: C-nerves = Above; T/L/S-nerves = Below.

Q: Which ligament is the primary limitation to extension of the vertebral column?

Anterior longitudinal ligament. The **Anterior Longitudinal Ligament (ALL)** is a strong, fibrous band that runs along the anterior surface of the vertebral bodies and intervertebral discs from the atlas to the sacrum [1]. Its primary biomechanical function is to stabilize the vertebral column and **limit extension** (hyperextension) [1]. It is the only ligament of the vertebral column that limits extension; all other major ligaments limit various degrees of flexion. **Analysis of Options:** * **Posterior Longitudinal Ligament (PLL):** Located on the posterior aspect of the vertebral bodies (inside the vertebral canal), it resists **flexion** and helps prevent posterior disc herniation. * **Supraspinous Ligament:** Connects the tips of the spinous processes from C7 to the sacrum. It is the first ligament to undergo strain during **flexion**. * **Ligamentum Flavum:** Connects the laminae of adjacent vertebrae. It is rich in elastic fibers, helping to maintain the upright posture and resisting **flexion** while protecting the spinal cord. **Clinical Pearls for NEET-PG:** * **Whiplash Injury:** In sudden hyperextension of the neck (e.g., rear-end motor vehicle accidents), the ALL is the structure most commonly severely stretched or torn. * **Forestier’s Disease (DISH):** Diffuse Idiopathic Skeletal Hyperostosis involves the calcification and ossification of the ALL, leading to a "melted candle wax" appearance on X-ray. * **Strength:** The ALL is significantly stronger than the PLL, which explains why most disc herniations occur posterolaterally where support is weaker.

Q: Which of the following is NOT a flexor of the lumbar spine?

Erector spinae. The movement of the lumbar spine is determined by the anatomical position of the muscles relative to the axis of the vertebral column. **1. Why Erector Spinae is the correct answer:** The **Erector spinae** (comprising the Iliocostalis, Longissimus, and Spinalis) is located **posterior** to the vertebral column. Its primary physiological action is **extension** of the spine when acting bilaterally and lateral flexion when acting unilaterally. Since it functions as an antagonist to flexion, it is not a flexor of the lumbar spine. **2. Analysis of incorrect options (Flexors):** The primary flexors of the lumbar spine are the muscles of the anterior and lateral abdominal wall. When these muscles contract bilaterally, they pull the ribcage toward the pelvis, decreasing the angle of the lumbar spine: * **Rectus abdominis:** The most powerful flexor of the lumbar spine. * **External and Internal obliques:** In addition to rotation and lateral flexion, their bilateral contraction significantly aids in trunk flexion. * **Psoas Major (not listed):** Also acts as a flexor of the lumbar spine (though its primary action is at the hip). **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Antigravity Muscles:** The Erector spinae are the chief "antigravity" muscles of the back, maintaining erect posture. * **Innervation:** All muscles of the Erector spinae group are innervated by the **posterior rami** of spinal nerves, whereas the abdominal flexors are innervated by the **anterior rami**. * **Multifidus:** This is the most important muscle for stabilizing the lumbar segments. * **Valsalva Maneuver:** The abdominal flexors (Obliques and Rectus) are also essential for increasing intra-abdominal pressure during defecation, micturition, and parturition.

Q: Which vertebra has the most prominent spinous process?

Cervical vertebra 7 (C7). **Explanation:** The correct answer is **Cervical vertebra 7 (C7)**. This vertebra is anatomically unique and is known as the **Vertebra Prominens**. 1. **Why C7 is correct:** The C7 vertebra is characterized by a long, thick, and nearly horizontal spinous process that is **not bifid** (unlike C2–C6). This process is so prominent that it creates a visible and palpable surface landmark at the base of the neck, especially when the neck is flexed. This makes it a crucial clinical landmark for counting vertebrae during physical examinations. 2. **Why the other options are incorrect:** * **C6:** While C6 is the last "typical" cervical vertebra, its spinous process is shorter than C7 and is usually bifid. It is known as the level of the **Carotid Tubercle (Chassaignac's tubercle)** on the transverse process, not for its spinous process. * **L1 and T12:** These vertebrae have thick, sturdy spinous processes designed for muscle attachment and weight-bearing, but they are buried deep under the thick paraspinal musculature (erector spinae) of the lower back, making them far less "prominent" to surface palpation compared to C7. **High-Yield Clinical Pearls for NEET-PG:** * **Surface Anatomy:** When palpating the spine, the two most prominent bumps at the base of the neck are usually **C7 and T1**. C7 is identified by the fact that its spine remains stationary or moves slightly during neck rotation, whereas T1 remains fixed. * **C7 Foramen Transversarium:** Unlike other cervical vertebrae, the foramen transversarium of C7 transmits only **accessory vertebral veins**, not the vertebral artery. * **Nerve Root:** The **C8 nerve root** exits the spinal canal through the intervertebral foramen between C7 and T1.

Q: Identify the nerve that supplies the marked structure.

Dorsal scapular nerve. ***Dorsal scapular nerve*** - The **dorsal scapular nerve** (C5) exclusively supplies the **rhomboid major**, **rhomboid minor**, and **levator scapulae** muscles. - These muscles are responsible for **scapular retraction** and **elevation**, which matches the anatomical location of the marked structure. *Dorsal rami of CI* - The **dorsal rami of C1** supply the **suboccipital muscles** including rectus capitis posterior major and minor. - These nerves innervate muscles involved in **head extension** and **rotation**, not scapular muscles. *Suprascapular nerve* - The **suprascapular nerve** (C5-C6) supplies the **supraspinatus** and **infraspinatus** muscles of the rotator cuff. - These muscles are located in the **supraspinous** and **infraspinous fossae** of the scapula, not the medial border region. *Subscapular nerve* - The **subscapular nerves** (upper and lower) supply the **subscapularis** and **teres major** muscles. - The **subscapularis** lies in the **subscapular fossa** on the anterior surface of the scapula, while **teres major** is located laterally.

Q: A 26-year-old woman experiences severe back pain from an automobile accident. CT scan shows that the L5 vertebral foramen is completely obliterated by the collapsed L5 laminae and pedicles. In this injury, which of the following structures is crushed?

Cauda equina. ### Explanation **Correct Option: A. Cauda equina** The spinal cord typically terminates at the level of the **L1-L2 intervertebral disc** in adults (the conus medullaris) [1]. Below this level, the vertebral canal contains the **cauda equina**, a bundle of spinal nerve roots (L2 through Co1) descending to reach their respective exit foramina [1], [2]. Since the injury occurred at the **L5 level**, the spinal cord is no longer present; instead, the vertebral foramen houses the cauda equina. A collapse of the L5 laminae and pedicles would directly crush these nerve roots [2]. **Why the other options are incorrect:** * **B. Vertebral artery:** This artery ascends through the **foramina transversaria** of the cervical vertebrae (C1–C6). It is not found in the lumbar region. * **C. Filum terminale:** While the filum terminale (an extension of the pia mater) does pass through the L5 level, it is a thin, thread-like structure [1]. The question asks for the primary structure filling the obliterated foramen; the cauda equina is the massive, dominant neural component at this level. * **D. Denticulate ligament:** These are lateral extensions of the pia mater that anchor the spinal cord to the dura. They end at the level of the **conus medullaris (L1)** and are not present in the lower lumbar canal. **High-Yield Facts for NEET-PG:** * **Spinal Cord Termination:** Adults (L1-L2), Infants (L3) [1]. * **Subarachnoid Space (Lumbar Cistern):** Ends at the level of **S2**. This is why lumbar punctures are safely performed between L3-L4 or L4-L5. * **Cauda Equina Syndrome:** A surgical emergency characterized by saddle anesthesia, bladder/bowel dysfunction, and lower limb weakness due to compression of these roots. * **Lumbar Puncture Landmark:** The supracristal line (Tuffier's line) connecting the highest points of the iliac crests crosses the **L4 spinous process**.

Q: A 25-year-old soldier suffers a gunshot wound on the posterior lower back and is unable to move his legs. A neurologic examination and magnetic resonance imaging (MRI) scan reveal injury of the cauda equina. Which of the following is most likely damaged?

Ventral roots of the sacral spinal nerves. **Explanation:** The **cauda equina** ("horse's tail") is a bundle of spinal nerve roots consisting of the **dorsal and ventral roots** of the lumbar, sacral, and coccygeal nerves (L2 through Co1). These roots descend within the subarachnoid space (lumbar cistern) below the level of the conus medullaris (which ends at L1-L2 in adults) before exiting through their respective intervertebral foramina. 1. **Why Option D is Correct:** Since the cauda equina is composed specifically of the descending dorsal and ventral roots of the lower spinal nerves, damage to this area directly involves the **ventral roots of the sacral spinal nerves**. Injury here leads to "Cauda Equina Syndrome," characterized by lower motor neuron signs, saddle anesthesia, and bladder/bowel dysfunction. 2. **Why Other Options are Incorrect:** * **Options A & B:** The **Dorsal and Ventral primary rami** are formed *after* the spinal nerve exits the intervertebral foramen. The cauda equina is located within the vertebral canal, proximal to the formation of the rami. * **Option C:** The **Thoracic spinal nerves** exit the vertebral column above the level of the cauda equina. The cauda equina only contains roots from L2 downwards. **High-Yield Clinical Pearls for NEET-PG:** * **Conus Medullaris vs. Cauda Equina:** Conus medullaris ends at **L1-L2** in adults and **L3** in infants. * **Lumbar Puncture:** Safely performed at the **L3-L4 or L4-L5** interspace because the cauda equina nerve roots float in CSF and "push away" from the needle, avoiding cord injury. * **Clinical Presentation:** Cauda Equina Syndrome is a surgical emergency. Look for **asymmetric** leg weakness, **areflexia** (LMN lesion), and **saddle anesthesia** (S3-S5 dermatomes).

Question 1

A 32-year-old male elite athlete felt severe pain radiating to the posterior aspect of his right thigh and leg during an intense training session involving heavy weights. MRI revealed a ruptured L4/L5 intervertebral disk. Which nerve is most probably affected?

Accepted Answer

L5

Answer

L3

Answer

L4

Answer

L2

Question 2

Which muscle, anatomically considered a back muscle, is functionally related to the thorax?

Accepted Answer

Latissimus dorsi

Answer

Rhomboid

Answer

Trapezius

Answer

Levator costae

Question 3

A 42-year-old woman with metastatic breast cancer is known to have tumors in the intervertebral foramina between the fourth and fifth cervical vertebrae and between the fourth and fifth thoracic vertebrae. Which of the following spinal nerves may be damaged?

Accepted Answer

Fifth cervical and fourth thoracic nerves

Answer

Fourth cervical and fourth thoracic nerves

Answer

Fifth cervical and fifth thoracic nerves

Answer

Fourth cervical and fifth thoracic nerves

Question 4

Which ligament is the primary limitation to extension of the vertebral column?

Accepted Answer

Anterior longitudinal ligament

Answer

Posterior longitudinal ligament

Answer

Supraspinous ligament

Answer

Ligamentum flavum

Question 5

Which of the following is NOT a flexor of the lumbar spine?

Accepted Answer

Erector spinae

Answer

External oblique muscle

Answer

Internal oblique muscle

Answer

Rectus abdominis

Question 6

Which vertebra has the most prominent spinous process?

Accepted Answer

Cervical vertebra 7 (C7)

Answer

Cervical vertebra 6 (C6)

Answer

Lumbar vertebra 1 (L1)

Answer

Thoracic vertebra 12 (T12)

Question 7

Identify the nerve that supplies the marked structure.

Accepted Answer

Dorsal scapular nerve

Answer

Dorsal rami of CI

Answer

Suprascapular nerve

Answer

Subscapular nerve

Question 8

All are true about the thoracolumbar fascia, except:

Accepted Answer

The fascia lies posterior to the posterior abdominal wall muscles.

Answer

It is attached to the spinous processes of the lumbar vertebrae.

Answer

It is attached to the transverse processes of the lumbar vertebrae.

Answer

It gives attachment to the transverse abdominis and internal oblique muscles.

Question 9

A 26-year-old woman experiences severe back pain from an automobile accident. CT scan shows that the L5 vertebral foramen is completely obliterated by the collapsed L5 laminae and pedicles. In this injury, which of the following structures is crushed?

Accepted Answer

Cauda equina

Answer

Vertebral artery

Answer

Filum terminale

Answer

Denticulate ligament

Question 10

A 25-year-old soldier suffers a gunshot wound on the posterior lower back and is unable to move his legs. A neurologic examination and magnetic resonance imaging (MRI) scan reveal injury of the cauda equina. Which of the following is most likely damaged?

Accepted Answer

Ventral roots of the sacral spinal nerves

Answer

Dorsal primary rami

Answer

Ventral primary rami

Answer

Dorsal roots of the thoracic spinal nerves

Back — MCQs

Back — MCQs

On this page

Practice by Chapter

Want unlimited practice?