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6. Spine MCQs

Practice Set 139 of 379

This practice set contains high-yield board review questions covering key concepts in 6. Spine. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 2761

Topic: 6. Spine

A 42-year-old patient presents with sudden-onset bilateral and symmetric saddle anesthesia, early bowel and bladder incontinence, and impotence. Lower extremity examination reveals hyperreflexia at the knees but absent Achilles reflexes. Motor weakness is mild and symmetric. Where is the most likely neuroanatomic location of the primary lesion?

. Cervical spinal cord (C5-C6)
. Thoracic spinal cord (T4-T5)
. Conus medullaris (typically T12-L2 level)
. Cauda equina (typically L3-L5 level)
. Lumbosacral plexus

Correct Answer & Explanation

. Conus medullaris (typically T12-L2 level)

Explanation

The presentation of sudden-onset, symmetric saddle anesthesia, prominent and early bowel/bladder/sexual dysfunction, and a mixture of Upper Motor Neuron (hyperreflexive knee jerks) and Lower Motor Neuron (absent ankle jerks) signs is characteristic of Conus Medullaris syndrome. In contrast, Cauda Equina syndrome typically presents with asymmetric radicular pain, progressive asymmetric weakness, pure LMN signs (hyporeflexia), and late-onset sphincter dysfunction.

Question 2762

Topic: Cervical Spine

During a right-sided anterior cervical discectomy and fusion (ACDF) at C6-C7, the patient develops a unilateral vocal cord paralysis. The vulnerability of the right recurrent laryngeal nerve during this approach is anatomically explained by its course looping under which of the following structures?

. Aortic arch
. Right subclavian artery
. Right common carotid artery
. Superior thyroid artery
. Brachiocephalic vein

Correct Answer & Explanation

. Right subclavian artery

Explanation

The recurrent laryngeal nerves (RLN) have asymmetric courses. The left RLN loops under the aortic arch and ascends predictably in the tracheoesophageal groove, making it relatively safe during left-sided approaches. The right RLN loops under the right subclavian artery and has a much more variable, oblique course as it ascends toward the larynx, increasing its risk of iatrogenic injury during lower right-sided cervical spine approaches.

Question 2763

Topic: Cervical Spine

The off-label use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in Anterior Cervical Discectomy and Fusion (ACDF) procedures has been strongly associated with which of the following serious postoperative complications?

. Cerebrospinal fluid leak
. Pseudarthrosis at the operated level
. Significant prevertebral soft tissue swelling leading to dysphagia and airway compromise
. Accelerated adjacent segment disease
. Vertebral artery thrombosis

Correct Answer & Explanation

. Significant prevertebral soft tissue swelling leading to dysphagia and airway compromise

Explanation

The use of rhBMP-2 (Infuse) in the anterior cervical spine is controversial and officially off-label due to a high risk of profound inflammatory responses. This inflammation causes severe prevertebral soft tissue swelling, which can result in life-threatening airway compromise, severe dysphagia, and the need for prolonged intubation or re-intubation.

Question 2764

Topic: 6. Spine

A patient presents with hand weakness and numbness in the ring and small fingers. The examiner is trying to differentiate between a C8 radiculopathy and a severe ulnar neuropathy at the elbow. Weakness in which of the following muscles firmly points to a C8 radiculopathy rather than an ulnar neuropathy?

. Flexor carpi ulnaris
. Abductor digiti minimi
. Flexor pollicis longus
. Dorsal interossei
. Lumbricals to the ring and small fingers

Correct Answer & Explanation

. Flexor pollicis longus

Explanation

Both C8 radiculopathy and ulnar neuropathy can cause weakness in the intrinsic muscles of the hand and sensory changes in the ulnar digits. However, the flexor pollicis longus (FPL) is innervated by the anterior interosseous nerve (a branch of the median nerve), but its nerve fibers originate from the C8 spinal root. Weakness of the FPL (or Extensor Indicis Proprius via the radial nerve, also C8) in the presence of ulnar-sided hand symptoms strongly localizes the lesion to the C8 root rather than the peripheral ulnar nerve.

Question 2765

Topic: 6. Spine

A 55-year-old male presents with severe, burning anterior thigh pain, weakness in right knee extension, and a diminished right patellar reflex. Sensation is decreased over the medial aspect of the lower leg. An MRI of the lumbar spine reveals an extraforaminal (far lateral) disc herniation at the L4-L5 level. Which nerve root is primarily compressed?

. L3
. L4
. L5
. S1
. S2

Correct Answer & Explanation

. L4

Explanation

In the lumbar spine, a classic paracentral disc herniation compresses the descending (traversing) nerve root (e.g., L4-L5 paracentral disc hits the L5 root). However, an extraforaminal or 'far lateral' disc herniation at L4-L5 compresses the exiting nerve root at that level, which is the L4 root. An L4 radiculopathy clinically presents with anterior thigh pain, quadriceps weakness (knee extension), and a diminished patellar reflex.

Question 2766

Topic: 6. Spine

A 48-year-old woman complains of severe neck pain radiating into her medial right forearm and hand. On physical examination, she demonstrates 3/5 strength in the flexor digitorum profundus of her right ring and small fingers, and 3/5 strength in finger abduction. She has diminished sensation over the ulnar border of her right hand and small finger. Her triceps strength and reflex are intact. Which cervical nerve root is most likely compressed?

. C5
. C6
. C7
. C8
. T1

Correct Answer & Explanation

. C8

Explanation

The patient is presenting with a classic C8 radiculopathy. The C8 nerve root supplies the extrinsic finger flexors (flexor digitorum profundus) and intrinsic hand muscles (interossei, lumbricals), and provides sensation to the ulnar border of the hand and the small finger. A T1 radiculopathy would also affect the intrinsic muscles but presents with sensory changes in the medial forearm rather than the hand, and is much less common. C7 radiculopathy primarily affects the triceps, wrist flexors, and finger extensors, with sensory changes in the middle finger.

Question 2767

Topic: 6. Spine

A 45-year-old man presents with acute onset of low back pain radiating down his right leg following heavy lifting. MRI reveals a large paracentral disc herniation at the L4-L5 level on the right side. Which nerve root is most likely compressed, and what clinical finding is expected?

. L4 root; weakness in ankle dorsiflexion and diminished patellar reflex
. L4 root; weakness in great toe extension and normal reflexes
. L5 root; weakness in great toe extension and diminished sensation in the first web space
. L5 root; weakness in ankle plantar flexion and absent Achilles reflex
. S1 root; weakness in ankle plantar flexion and absent Achilles reflex

Correct Answer & Explanation

. L5 root; weakness in great toe extension and diminished sensation in the first web space

Explanation

In the lumbar spine, a typical paracentral disc herniation compresses the traversing nerve root, while a far lateral (foraminal/extraforaminal) disc herniation compresses the exiting nerve root. At the L4-L5 level, the exiting root is L4 and the traversing root is L5. Therefore, a paracentral disc herniation at L4-L5 affects the L5 nerve root. L5 radiculopathy is characterized by weakness in the extensor hallucis longus (great toe extension) and altered sensation over the dorsum of the foot, particularly the first dorsal web space.

Question 2768

Topic: 6. Spine

A 60-year-old man undergoes a C4-C6 posterior laminectomy and instrumented fusion for cervical spondylotic myelopathy. On postoperative day 3, he suddenly develops profound unilateral weakness in shoulder abduction and elbow flexion, without a change in his leg strength or bowel/bladder function. What is the most widely accepted pathophysiologic mechanism for this complication?

. Intraoperative epidural hematoma compressing the spinal cord
. Posterior migration of the spinal cord resulting in tethering of the nerve root
. Anterior spinal artery ischemia
. Direct intraoperative transection of the nerve root during pedicle instrumentation
. Subsidence of an interbody graft

Correct Answer & Explanation

. Posterior migration of the spinal cord resulting in tethering of the nerve root

Explanation

The patient is experiencing a C5 palsy, a well-known complication following cervical decompression surgery (particularly posterior laminectomy/laminoplasty). The C5 nerve root has a short, horizontal course. When the compressive pathology is removed posteriorly, the spinal cord shifts dorsally (posterior drift). This drift can place excessive traction (tethering) on the short C5 nerve root. It frequently presents in a delayed fashion (typically 2-5 days postoperatively) with deltoid and biceps weakness.

Question 2769

Topic: Thoracolumbar Spine & Deformity

A 16-year-old gymnast presents with progressive lower back pain and left leg pain. Imaging demonstrates a Grade II L5-S1 isthmic spondylolisthesis with bilateral pars interarticularis defects. If the patient has isolated left lower extremity radicular symptoms, which nerve root is most likely affected by the primary pathoanatomy of this condition?

. Exiting L4 root
. Traversing L4 root
. Exiting L5 root
. Traversing L5 root
. Traversing S1 root

Correct Answer & Explanation

. Exiting L5 root

Explanation

In isthmic spondylolisthesis at L5-S1, the defect is in the pars interarticularis of L5. The L5 nerve root exits the spinal canal through the L5-S1 neural foramen, passing directly inferior and anterior to the L5 pars. Hypertrophic fibrocartilaginous tissue (the 'Gill nodule') that forms at the site of the pars defect commonly compresses this exiting L5 nerve root in the foramen. This contrasts with degenerative spondylolisthesis (e.g., L4-L5), where central/lateral recess stenosis typically compresses the traversing root (L5).

Question 2770

Topic: 6. Spine

A 42-year-old woman with a history of chronic low back pain presents to the emergency department with acute worsening of back pain, bilateral sciatica, and perineal numbness. Which of the following urologic findings is the earliest and most reliable indicator of cauda equina syndrome?

. Primary stress incontinence
. Spastic bladder with detrusor hyperreflexia
. Urinary retention with overflow incontinence
. A post-void residual volume of less than 50 mL
. Increased urgency and frequency of micturition

Correct Answer & Explanation

. Urinary retention with overflow incontinence

Explanation

Cauda equina syndrome involves compression of the lumbosacral nerve roots below the conus medullaris, affecting the parasympathetic supply to the bladder (S2-S4). This lower motor neuron injury leads to a loss of bladder sensation and a flaccid, areflexic detrusor muscle. The earliest and most reliable urologic sign is urinary retention. As the bladder fills without the ability to voluntarily void, it eventually leads to overflow incontinence. A post-void residual volume typically exceeds 100-200 mL.

Question 2771

Topic: 6. Spine

A 45-year-old female presents with acute onset of severe unilateral shoulder pain, which subsides after one week, leaving profound weakness in shoulder abduction and external rotation. MRI of the cervical spine is unremarkable. EMG shows active denervation in the supraspinatus and infraspinatus. What is the most likely diagnosis?

. C5 radiculopathy
. Parsonage-Turner syndrome
. Quadrilateral space syndrome
. Suprascapular nerve entrapment at the spinoglenoid notch
. Thoracic outlet syndrome

Correct Answer & Explanation

. Parsonage-Turner syndrome

Explanation

Acute, severe neuropathic shoulder pain followed by patchy weakness (often involving the suprascapular or axillary nerves) is the classic presentation of Parsonage-Turner syndrome (idiopathic brachial neuritis).

Question 2772

Topic: 6. Spine

A 35-year-old male sustains a severe traction injury to his right upper extremity. Clinical examination reveals flaccid paralysis of the entire right arm with anesthesia from the shoulder to the hand. Electromyography (EMG) shows denervation of the cervical paraspinal muscles. Sensory nerve action potentials (SNAPs) are tested for the right upper extremity. Which of the following SNAP findings is most consistent with this patient's injury level and prognosis?

. Absent SNAPs with an intact sensory clinical examination
. Absent SNAPs with profound sensory loss
. Normal SNAPs with profound sensory loss
. Normal SNAPs with an intact sensory clinical examination
. Variable SNAPs dependent on the timing of the injury

Correct Answer & Explanation

. Normal SNAPs with an intact sensory clinical examination

Explanation

Normal SNAPs in an anesthetic limb indicate a preganglionic injury (root avulsion). The sensory dorsal root ganglion remains intact and connected to the peripheral nerve, while the central connection to the spinal cord is severed.

Question 2773

Topic: 6. Spine

A 40-year-old female with long-standing rheumatoid arthritis is suddenly unable to flex the interphalangeal joint of her right thumb. Examination reveals a loss of active thumb IP flexion but an intact tenodesis effect when the wrist is passively extended. What is the most likely cause of this deficit?

. Anterior interosseous nerve (AIN) syndrome
. Posterior interosseous nerve (PIN) syndrome
. Rupture of the flexor pollicis longus (FPL) tendon
. Trigger thumb
. C8 radiculopathy

Correct Answer & Explanation

. Anterior interosseous nerve (AIN) syndrome

Explanation

Loss of active thumb IP flexion with an intact tenodesis effect implies that the FPL tendon is intact, pointing to a neurological cause such as Anterior Interosseous Nerve (AIN) syndrome. A ruptured FPL (Mannerfelt lesion) would have an absent tenodesis effect.

Question 2774

Topic: 6. Spine

A 50-year-old rheumatoid patient cannot actively extend her small and ring fingers at the metacarpophalangeal (MCP) joints. She can actively maintain extension if the fingers are passively placed in that position. A drop-finger sign is present. What is the most likely diagnosis?

. Vaughan-Jackson syndrome
. Mannerfelt-Norman syndrome
. Posterior interosseous nerve (PIN) syndrome
. Sagittal band rupture with tendon subluxation
. C7 radiculopathy

Correct Answer & Explanation

. Sagittal band rupture with tendon subluxation

Explanation

The ability to actively maintain extension once passively placed is the hallmark of sagittal band rupture causing volar subluxation of the extensor tendons. In Vaughan-Jackson syndrome (tendon rupture), the patient cannot maintain extension.

Question 2775

Topic: Cervical Spine

A 25-year-old man dives into a shallow pool and sustains a C1 burst fracture (Jefferson fracture). An open-mouth odontoid radiograph demonstrates that the combined lateral overhang of the C1 lateral masses on C2 is 8 mm. What does this finding indicate and what is the recommended management?

. Intact transverse ligament; treat with a rigid cervical collar
. Ruptured transverse ligament; treat with a halo vest or C1-C2 fusion
. Alar ligament rupture; treat with occipitocervical fusion
. Apical ligament rupture; treat with a soft collar
. Concomitant Type II odontoid fracture; treat with an anterior odontoid screw

Correct Answer & Explanation

. Ruptured transverse ligament; treat with a halo vest or C1-C2 fusion

Explanation

According to the Spence rule, a combined lateral overhang of the C1 lateral masses on C2 greater than 6.9 mm indicates a rupture of the transverse ligament. This renders the injury highly unstable, necessitating rigid immobilization with a halo vest or surgical C1-C2 fusion.

Question 2776

Topic: 6. Spine

The Spinal Instability Neoplastic Score (SINS) is utilized to assess the need for surgical stabilization in patients with spinal metastasis. Which of the following is an explicit component of the SINS criteria?

. Primary tumor histology
. Patient's systemic neurologic status
. Presence of posterolateral spinal element involvement
. Sensitivity to local radiotherapy
. Karnofsky performance status

Correct Answer & Explanation

. Presence of posterolateral spinal element involvement

Explanation

The SINS criteria assess spinal instability based on six components: location, pain, bone lesion type (lytic/blastic), radiographic alignment, vertebral body collapse, and posterolateral involvement. Tumor histology and systemic status dictate overall survival but are not part of the mechanical SINS score.

Question 2777

Topic: Thoracolumbar Spine & Deformity

A 12-year-old female gymnast complains of persistent lower back pain. Imaging demonstrates an L5-S1 isthmic spondylolisthesis with 35% slippage (Grade II). She has failed 6 months of physical therapy and bracing. What is the most appropriate surgical intervention?

. L4-S1 posterior spinal fusion with instrumentation
. L5-S1 in situ posterolateral fusion
. Anterior lumbar interbody fusion (ALIF) alone
. L5 laminectomy without fusion
. Lumbar epidural steroid injections

Correct Answer & Explanation

. L5-S1 in situ posterolateral fusion

Explanation

For pediatric patients with symptomatic low-grade (<50%) isthmic spondylolisthesis failing conservative management, an in situ L5-S1 posterolateral fusion is the gold standard. Decompression without fusion is contraindicated in children due to the high risk of further slippage.

Question 2778

Topic: 6. Spine

A 40-year-old man presents to the emergency department with acute urinary retention, saddle anesthesia, and progressive bilateral leg weakness due to a massive L4-L5 disc herniation. To optimize the chance of neurologic recovery, surgical decompression must ideally occur within what timeframe?

. 12 hours
. 24 hours
. 48 hours
. 72 hours
. 1 week

Correct Answer & Explanation

. 48 hours

Explanation

This patient has acute cauda equina syndrome, an absolute surgical emergency. Literature demonstrates that surgical decompression performed within 48 hours of symptom onset yields the best outcomes for bladder and motor function recovery.

Question 2779

Topic: 6. Spine

A 65-year-old man presents with dysphagia and severe cervical stiffness. Radiographs demonstrate flowing ossification along the anterolateral aspect of four contiguous cervical vertebral bodies with preserved disc spaces and normal sacroiliac joints. What is the most likely diagnosis?

. Ankylosing spondylitis
. Rheumatoid arthritis
. Diffuse idiopathic skeletal hyperostosis (DISH)
. Cervical spondylotic myelopathy
. Ossification of the posterior longitudinal ligament (OPLL)

Correct Answer & Explanation

. Diffuse idiopathic skeletal hyperostosis (DISH)

Explanation

DISH is characterized by flowing anterolateral ossification across at least four contiguous vertebrae, preservation of disc height, and absence of sacroiliac joint fusion. The bulky anterior cervical osteophytes can compress the esophagus, leading to dysphagia.

Question 2780

Topic: 6. Spine

A 70-year-old man with advanced Ankylosing Spondylitis suffers a low-energy ground-level fall. He complains of severe neck pain but is neurologically intact. Standard lateral cervical radiographs are obscured by his shoulder anatomy. What is the mandatory next step in his workup?

. Discharge with a rigid cervical collar
. Flexion and extension radiographs
. CT scan of the entire cervical and thoracic spine
. Prescribe NSAIDs and outpatient physical therapy
. Immediate halo vest application

Correct Answer & Explanation

. CT scan of the entire cervical and thoracic spine

Explanation

Patients with Ankylosing Spondylitis have a rigid, osteopenic spine that acts like a long bone, making it highly susceptible to unstable hyperextension fractures even from minor trauma. A CT or MRI of the entire spine is mandatory due to the high risk of occult, highly unstable fractures and epidural hematomas.

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