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6. Spine MCQs

Practice Set 351 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 7001

Topic: 6. Spine

A 35-year-old male with achondroplasia presents with neurogenic claudication. Radiographs show severe lumbar spinal stenosis. What anatomical feature primarily accounts for the spinal stenosis in this condition?

. Ligamentum flavum hypertrophy
. Congenital absence of the pars interarticularis
. Abnormally short pedicles with decreased interpedicular distance
. Severe facet joint arthropathy
. Vertebral body wedging

Correct Answer & Explanation

. Abnormally short pedicles with decreased interpedicular distance

Explanation

Spinal stenosis in achondroplasia is primarily due to congenitally short pedicles and a characteristic narrowing of the interpedicular distance from L1 to L5. This decreases both the anteroposterior and transverse diameters of the spinal canal.

Question 7002

Topic: 6. Spine

A 45-year-old patient with achondroplasia undergoes a lumbar laminectomy for severe spinal stenosis. What crucial anatomical consideration must be addressed during decompression to ensure success while preventing iatrogenic instability?

. Routine excision of the pars interarticularis is required
. Pedicle subtraction osteotomy is mandatory at all decompressed levels
. Wide laminectomy must extend laterally to the medial facet to decompress the recess, while preserving the pars
. Stand-alone anterior interbody fusion should always accompany the laminectomy
. Only the ligamentum flavum should be resected to avoid destabilizing the short pedicles

Correct Answer & Explanation

. Wide laminectomy must extend laterally to the medial facet to decompress the recess, while preserving the pars

Explanation

Due to the short pedicles and narrow interpedicular distance, the lateral recesses are particularly stenotic in achondroplasia. A wide laminectomy extending to the medial facets is required for adequate decompression, taking care to preserve the pars interarticularis to avoid instability.

Question 7003

Topic: 6. Spine

Reviewing an anteroposterior (AP) radiograph of the lumbar spine in a patient with achondroplasia, what is the expected change in interpedicular distance from L1 to L5?

. It progressively increases
. It remains constant
. It progressively decreases
. It increases at L3 and then rapidly decreases
. It decreases at L2 then increases towards L5

Correct Answer & Explanation

. It progressively decreases

Explanation

In achondroplasia, the interpedicular distance progressively decreases from L1 to L5. This is the opposite of a normal spine, where the distance widens caudally, and is a major contributor to lumbar spinal stenosis.

Question 7004

Topic: 6. Spine

A 9-month-old infant with achondroplasia presents with central sleep apnea, hypotonia, and brisk lower extremity reflexes. What is the most appropriate next step in management?

. Polysomnography and continuous positive airway pressure (CPAP)
. Cervical spine bracing
. MRI of the craniovertebral junction
. Reassurance as this is normal for age
. Immediate lumbar puncture

Correct Answer & Explanation

. MRI of the craniovertebral junction

Explanation

These symptoms suggest cervical myelopathy due to foramen magnum stenosis, a potentially lethal complication in infants with achondroplasia. An MRI of the craniovertebral junction is indicated to evaluate for brainstem compression.

Question 7005

Topic: 6. Spine

A 45-year-old male with achondroplasia presents with bilateral leg pain and weakness after walking 50 meters, which is relieved by sitting. Which anatomic abnormality is the primary driver of this patient's pathology?

. Ligamentum flavum hypertrophy
. Congenitally short pedicles
. Facet joint arthropathy
. Isthmic spondylolisthesis
. Thoracolumbar kyphosis

Correct Answer & Explanation

. Congenitally short pedicles

Explanation

Neurogenic claudication in adult achondroplastic patients is primarily caused by severe spinal stenosis. This is anatomically driven by congenitally short, thickened pedicles and decreased interpedicular distances.

Question 7006

Topic: 6. Spine

When reviewing the AP lumbar spine radiograph of a patient with achondroplasia, what classic finding differentiates their anatomy from an individual with normal stature?

. Progressive widening of the interpedicular distance from L1 to L5
. Progressive narrowing of the interpedicular distance from L1 to L5
. Absence of the pedicles at L4 and L5
. Congenital fusion of the pedicles from L1 to L3
. Coronal clefts within the vertebral bodies

Correct Answer & Explanation

. Progressive narrowing of the interpedicular distance from L1 to L5

Explanation

In a normal spine, the interpedicular distance progressively widens from L1 to L5. In achondroplasia, the interpedicular distance classically narrows from L1 to L5, predisposing the patient to spinal stenosis.

Question 7007

Topic: 6. Spine

A 6-year-old with achondroplasia is found to have a rigid, progressive thoracolumbar kyphosis measuring 50 degrees. Lateral spine radiographs are most likely to show which associated finding at the apical vertebra?

. Posterior hemivertebra
. Anterior wedging and a bullet-shaped appearance
. Spondylolisthesis at L5-S1
. Coronal cleft
. Block vertebrae

Correct Answer & Explanation

. Anterior wedging and a bullet-shaped appearance

Explanation

If infantile thoracolumbar kyphosis persists and becomes fixed, the apical vertebrae (typically L1 or L2) fail to develop normally anteriorly. This results in anterior wedging and a classic 'bullet-shaped' vertebra.

Question 7008

Topic: 6. Spine

A 6-month-old infant with achondroplasia presents with hypotonia, central sleep apnea, and poor head control. Which of the following is the most critical next step in management?

. Observation, as hypotonia is physiologic at this age in achondroplasia
. Cervical spine MRI to evaluate for foramen magnum stenosis
. Immediate posterior spinal fusion of the cervical spine
. Thoracolumbar bracing to prevent progressive kyphosis
. Polysomnography as a definitive standalone diagnostic tool

Correct Answer & Explanation

. Cervical spine MRI to evaluate for foramen magnum stenosis

Explanation

Infants with achondroplasia are at high risk for foramen magnum stenosis, which can present with central sleep apnea, hyperreflexia, or marked hypotonia. An MRI of the cervicomedullary junction is essential to evaluate for cord compression that may require urgent neurosurgical decompression.

Question 7009

Topic: 6. Spine

Which of the following is the hallmark radiographic finding in the lumbar spine of a patient with achondroplasia?

. Increased interpedicular distance from L1 to L5
. Decreased or unchanged interpedicular distance from L1 to L5
. Vertebral body scalloping exclusively on the anterior aspect
. Bullet-shaped vertebrae predominantly at the cervical level
. Absent pedicles throughout the lumbar spine

Correct Answer & Explanation

. Decreased or unchanged interpedicular distance from L1 to L5

Explanation

The classic radiographic feature of achondroplasia in the lumbar spine is the narrowing (or failure to normally widen) of the interpedicular distance from L1 to L5. Combined with short pedicles, this dramatically decreases the spinal canal volume and leads to symptomatic spinal stenosis later in life.

Question 7010

Topic: 6. Spine

A 45-year-old male with achondroplasia presents with severe, progressive neurogenic claudication and lower extremity weakness. MRI confirms severe multi-level lumbar spinal stenosis. What is the most appropriate surgical approach?

. Laminectomy with strict preservation of the facets and pedicles
. Wide laminectomy with partial or complete facetectomy and instrumented fusion
. Anterior lumbar interbody fusion (ALIF) alone
. Stand-alone interspinous process spacer placement
. Spinal cord stimulator placement

Correct Answer & Explanation

. Wide laminectomy with partial or complete facetectomy and instrumented fusion

Explanation

Spinal stenosis in achondroplasia is caused by short, thickened pedicles and severely decreased interpedicular distance. Effective decompression requires wide laminectomies often extending into the lateral recesses, which necessitates facetectomies and concomitant instrumented fusion to prevent iatrogenic instability.

Question 7011

Topic: 6. Spine

A 6-month-old infant with achondroplasia presents with a history of central sleep apnea, hypotonia, and brisk deep tendon reflexes. What is the most appropriate next step in management?

. Observation as it spontaneously resolves by age 2
. Bracing with a cervicothoracic orthosis
. MRI of the craniocervical junction
. Continuous positive airway pressure (CPAP) at night
. Posterior spinal fusion of the cervical spine

Correct Answer & Explanation

. MRI of the craniocervical junction

Explanation

Foramen magnum stenosis is a potentially fatal complication in infants with achondroplasia, presenting with central sleep apnea and myelopathy. An MRI is required to evaluate for cervicomedullary compression, which may necessitate urgent suboccipital decompression.

Question 7012

Topic: 6. Spine

A 45-year-old male with achondroplasia presents with progressive neurogenic claudication and lower extremity weakness. MRI reveals severe lumbar spinal stenosis from L1 to L4. What is the most appropriate surgical intervention?

. Multilevel wide laminectomies preserving the lateral pars and facets
. Multilevel laminectomy with extensive facetectomy requiring fusion
. Anterior lumbar interbody fusion (ALIF) alone
. Corticosteroid epidural injections
. Interspinous process spacer placement

Correct Answer & Explanation

. Multilevel wide laminectomies preserving the lateral pars and facets

Explanation

Spinal stenosis in achondroplasia is caused by short pedicles and narrowing interpedicular distances. Multilevel wide laminectomy is the treatment of choice, taking care to preserve the pars and facets to avoid iatrogenic instability.

Question 7013

Topic: 6. Spine

Review the AP radiograph of the lumbar spine in a patient with suspected skeletal dysplasia.

What is the characteristic finding of the lumbar pedicles in achondroplasia?

. Interpedicular distance increases from L1 to L5
. Interpedicular distance decreases from L1 to L5
. Pedicles are abnormally long
. Pedicles are absent (winking owl sign)
. Interpedicular distance remains constant but pedicles are sclerotic

Correct Answer & Explanation

. Interpedicular distance decreases from L1 to L5

Explanation

In a normal spine, the interpedicular distance increases from L1 to L5. In achondroplasia, the classic radiographic finding is a progressive narrowing of the interpedicular distance from L1 to L5, contributing to spinal stenosis.

Question 7014

Topic: 6. Spine

A 30-year-old pregnant woman with achondroplasia requires a Cesarean section. Which of the following is the most significant anesthetic consideration for her neuraxial anesthesia?

. Increased risk of bleeding due to coagulopathy
. Decreased epidural space volume requiring dose reduction
. High risk of autonomic dysreflexia
. Contraindication to spinal anesthesia due to low conus medullaris
. Inability to position the patient optimally

Correct Answer & Explanation

. Decreased epidural space volume requiring dose reduction

Explanation

Patients with achondroplasia have severe spinal canal stenosis and a reduced epidural space volume. Regional anesthetic doses must be significantly reduced to avoid unexpectedly high spinal blockade and associated respiratory compromise.

Question 7015

Topic: 6. Spine

A 45-year-old male presents with a "foot drop" and numbness over the dorsum of his foot. To differentiate between a compressive common peroneal neuropathy at the fibular head and an L5 radiculopathy from an L4-L5 disc herniation, weakness in which of the following muscles would most specifically point to an L5 radiculopathy?

. Tibialis anterior
. Extensor hallucis longus
. Peroneus longus
. Tibialis posterior
. Extensor digitorum brevis

Correct Answer & Explanation

. Tibialis posterior

Explanation

Correct Answer: Tibialis posteriorBoth the common peroneal nerve and the L5 nerve root innervate the tibialis anterior, extensor hallucis longus (EHL), extensor digitorum brevis (EDB), and peroneus longus. However, the tibialis posterior is innervated by the tibial nerve, which receives its primary motor contributions from the L4 and L5 nerve roots. Therefore, weakness in foot inversion (tibialis posterior function) in the setting of a foot drop indicates a lesion proximal to the sciatic bifurcation, specifically an L5 radiculopathy, rather than an isolated common peroneal nerve palsy.

Question 7016

Topic: 6. Spine

A 72-year-old male complains of bilateral calf and thigh pain that occurs after walking two blocks. The pain is relieved when he sits down or leans forward on a shopping cart. He denies pain when riding a stationary bicycle. His pedal pulses are 2+ bilaterally. Which of the following pathophysiologic mechanisms is the primary cause of his symptoms?

. Atherosclerotic narrowing of the superficial femoral artery.
. Hypertrophy of the ligamentum flavum and facet arthropathy.
. Herniation of the nucleus pulposus compressing the exiting nerve root.
. Spondylolysis of the L5 pars interarticularis.
. Demyelination of the peripheral nerves due to chronic hyperglycemia.

Correct Answer & Explanation

. Hypertrophy of the ligamentum flavum and facet arthropathy.

Explanation

Correct Answer: BThe patient's symptoms are classic for neurogenic claudication secondary to lumbar spinal stenosis. The relief of symptoms with lumbar flexion (e.g., leaning on a shopping cart, riding a bicycle) occurs because flexion increases the cross-sectional area of the spinal canal, relieving pressure on the neural elements. The primary degenerative changes causing central canal stenosis are facet joint hypertrophy, ligamentum flavum hypertrophy, and bulging of the intervertebral disc. Vascular claudication would cause pain with any exertion (including cycling) and is relieved by rest alone, not postural changes.

Question 7017

Topic: 6. Spine

A 65-year-old male presents with bilateral hand clumsiness, frequent falls, and a broad-based gait. Physical examination reveals a positive Hoffmann sign and hyperreflexia. MRI shows severe cervical spinal stenosis at C4-C5 and C5-C6 with cord signal change. Which of the following physical exam findings is most specific for upper motor neuron dysfunction in this condition?

. Decreased grip strength
. Positive Tinel sign at the wrist
. Atrophy of the intrinsic hand muscles
. Inverted brachioradialis reflex
. Diminished light touch sensation in the C6 dermatome

Correct Answer & Explanation

. Inverted brachioradialis reflex

Explanation

An inverted brachioradialis reflex (finger flexion upon tapping the brachioradialis tendon) is a classic upper motor neuron sign seen in cervical spondylotic myelopathy. Atrophy and decreased grip strength are lower motor neuron findings.

Question 7018

Topic: 6. Spine

A 45-year-old male complains of right leg pain radiating down the lateral aspect of his calf to the dorsum of his foot. On examination, he has profound weakness in extensor hallucis longus (EHL) and decreased sensation over the first dorsal web space. A paracentral disc herniation at which lumbar level is most likely responsible for these findings?

. L2-L3
. L3-L4
. L4-L5
. L5-S1
. S1-S2

Correct Answer & Explanation

. L4-L5

Explanation

Weakness of the EHL and numbness in the first dorsal webspace indicate an L5 radiculopathy. A paracentral disc herniation at L4-L5 impinges on the traversing L5 nerve root.

Question 7019

Topic: 6. Spine

A 65-year-old male complains of deteriorating hand dexterity and difficulty maintaining his balance. Examination reveals a positive Hoffmann's sign, hyperreflexia, and a wide-based gait. Cervical MRI demonstrates severe spinal canal stenosis at C4-C5. Which of the following physical exam findings is most likely to also be present in this patient?

. Hyporeflexia in the lower extremities
. Positive Lhermitte's sign
. Negative Babinski reflex
. Fasciculations in the upper extremities
. Absent cremasteric reflex

Correct Answer & Explanation

. Positive Lhermitte's sign

Explanation

The patient has cervical spondylotic myelopathy, presenting with upper motor neuron signs. A positive Lhermitte's sign (an electric shock-like sensation traveling down the spine with neck flexion) is common, alongside hyperreflexia and a positive Babinski sign.

Question 7020

Topic: 6. Spine

A 60-year-old male presents with progressive hand clumsiness and gait instability. On examination, tapping the distal brachioradialis tendon results in diminished elbow flexion but elicits spontaneous flexion of the ipsilateral fingers. This physical exam finding localizes the compressive cervical pathology to which of the following spinal levels?

. C3-C4
. C5-C6
. C7-T1
. T1-T2
. L4-L5

Correct Answer & Explanation

. C5-C6

Explanation

The inverted supinator (brachioradialis) reflex is characterized by an absent brachioradialis reflex with simultaneous hyperactive finger flexion. This indicates a lower motor neuron lesion at the C5-C6 level and an upper motor neuron lesion below that level, effectively localizing the compression to C5-C6.

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