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6. Spine MCQs

Practice Set 365 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 7281

Topic: 6. Spine

Which of the following clinical or radiographic features reliably distinguishes pseudoachondroplasia from achondroplasia?

. Presence of frontal bossing and severe midface hypoplasia
. High risk of atlantoaxial instability requiring cervical spine screening
. Mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene
. Severe lumbar spinal stenosis due to a decreased interpedicular distance

Correct Answer & Explanation

. High risk of atlantoaxial instability requiring cervical spine screening

Explanation

Correct Answer: High risk of atlantoaxial instability requiring cervical spine screeningPseudoachondroplasia is caused by a mutation in the Cartilage Oligomeric Matrix Protein (COMP) gene. Unlike achondroplasia, patients with pseudoachondroplasia have normal facial features and head circumference at birth. In the spine, pseudoachondroplasia is associated with odontoid hypoplasia and a high risk of atlantoaxial instability (AAI), necessitating cervical spine screening. Achondroplasia, conversely, is associated with foramen magnum stenosis but typically does NOT feature AAI.

Question 7282

Topic: 6. Spine

A 4-year-old child with coarse facial features, corneal clouding, and hepatosplenomegaly is diagnosed with a mucopolysaccharidosis. Lateral spine radiographs demonstrate a thoracolumbar kyphosis with characteristic vertebral body morphology. Which of the following radiographic findings is most typical for Hurler syndrome (MPS I)?

. Anteroinferior beaking of the lumbar vertebral bodies
. Central anterior beaking of the lumbar vertebral bodies
. Coronal clefts in the thoracic vertebrae
. Picture-frame appearance of the vertebral bodies

Correct Answer & Explanation

. Anteroinferior beaking of the lumbar vertebral bodies

Explanation

Correct Answer: Anteroinferior beaking of the lumbar vertebral bodiesHurler syndrome (Mucopolysaccharidosis type I) is caused by a deficiency of alpha-L-iduronidase. Spinal manifestations include thoracolumbar kyphosis and characteristic vertebral body changes. The classic radiographic finding in Hurler syndrome is anteroinferior beaking of the vertebral bodies (usually L1 or L2), which are often hypoplastic and retroplaced, leading to kyphosis. In contrast, Morquio syndrome (MPS IV) is classically associated with central anterior beaking of the vertebral bodies. Coronal clefts are seen in Kniest dysplasia, and a picture-frame appearance is characteristic of Paget's disease.

Question 7283

Topic: 6. Spine

In patients with achondroplasia, lumbar spinal stenosis is a common and debilitating complication. Which of the following best describes the primary pathoanatomic cause of this stenosis?

. Hypertrophy of the ligamentum flavum and facet joints
. Decreased interpedicular distance and short pedicles
. Severe degenerative spondylolisthesis
. Congenital absence of the posterior elements
. Progressive thoracolumbar kyphosis

Correct Answer & Explanation

. Decreased interpedicular distance and short pedicles

Explanation

Correct Answer: Decreased interpedicular distance and short pediclesAchondroplasia is characterized by a defect in endochondral ossification due to an FGFR3 mutation. In the spine, this manifests as prematurely fused neurocentral synchondroses, leading to abnormally short pedicles and a narrowed interpedicular distance, particularly in the lower lumbar spine. This congenital narrowing predisposes patients to severe spinal stenosis later in life.

Question 7284

Topic: 6. Spine

A 6-year-old boy with Morquio syndrome (Mucopolysaccharidosis type IV) presents for routine orthopedic evaluation. He has normal intelligence but exhibits a waddling gait and knock knees. Which of the following spinal abnormalities is most critical to screen for in this patient to prevent sudden neurologic deterioration?

. Thoracolumbar kyphosis
. Lumbar spinal stenosis
. Atlantoaxial instability due to odontoid hypoplasia
. Basilar invagination
. Tethered cord syndrome

Correct Answer & Explanation

. Atlantoaxial instability due to odontoid hypoplasia

Explanation

Correct Answer: Atlantoaxial instability due to odontoid hypoplasiaMorquio syndrome (MPS IV) is associated with severe skeletal dysplasia, including platyspondyly with central anterior beaking. The most life-threatening spinal manifestation is atlantoaxial instability secondary to odontoid hypoplasia and ligamentous laxity. This requires careful screening with flexion-extension cervical radiographs and often necessitates prophylactic posterior cervical fusion to prevent catastrophic spinal cord injury.

Question 7285

Topic: 6. Spine

A 2-month-old infant is diagnosed with diastrophic dysplasia. Radiographs reveal a significant cervical kyphosis. What is the typical natural history and recommended initial management for this specific spinal deformity?

. It is universally progressive and requires immediate posterior spinal fusion
. It typically resolves spontaneously with growth; observation is recommended
. It is caused by a tethered cord; neurosurgical release is the first step
. It rapidly progresses to basilar invagination; halo gravity traction is indicated
. It is rigid and requires anterior corpectomy and strut grafting in infancy

Correct Answer & Explanation

. It typically resolves spontaneously with growth; observation is recommended

Explanation

Correct Answer: It typically resolves spontaneously with growth; observation is recommendedCervical kyphosis in diastrophic dysplasia is common in infancy. Unlike many other dysplasias where cervical kyphosis is rigidly progressive, the cervical kyphosis in diastrophic dysplasia often resolves spontaneously as the child grows and gains head control. Initial management is observation. Surgical intervention is reserved for cases that progress or present with neurologic deficits.

Question 7286

Topic: 6. Spine

Spondyloepiphyseal dysplasia congenita (SEDC) is characterized by a disproportionate short-trunk dwarfism. Which of the following genetic mutations and associated spinal deformities are characteristic of this condition?

. FGFR3 mutation; lumbar spinal stenosis
. COMP mutation; severe rigid scoliosis
. COL2A1 mutation; odontoid hypoplasia and atlantoaxial instability
. SLC26A2 mutation; cervical kyphosis
. RUNX2 mutation; basilar invagination

Correct Answer & Explanation

. COL2A1 mutation; odontoid hypoplasia and atlantoaxial instability

Explanation

Correct Answer: COL2A1 mutation; odontoid hypoplasia and atlantoaxial instabilitySEDC is caused by mutations in the COL2A1 gene, which encodes for type II collagen. It primarily affects the spine and epiphyses. Key spinal manifestations include platyspondyly, odontoid hypoplasia leading to atlantoaxial instability, and kyphoscoliosis. FGFR3 is associated with achondroplasia, COMP with pseudoachondroplasia, SLC26A2 with diastrophic dysplasia, and RUNX2 with cleidocranial dysplasia.

Question 7287

Topic: 6. Spine
A 14-year-old patient with severe Osteogenesis Imperfecta (Type III) presents with new-onset occipital headaches, hyperreflexia, and lower cranial nerve deficits. Which of the following spinal pathologies is the most likely cause of these symptoms?
. Atlantoaxial rotatory subluxation
. Basilar invagination
. Thoracic scoliosis curve progression
. Lumbar spondylolysis
. Syringomyelia

Correct Answer & Explanation

. Basilar invagination

Explanation

Basilar invagination (or basilar impression) is a known and potentially lethal complication in severe forms of Osteogenesis Imperfecta (such as Type III). The soft, osteopenic bone of the skull base allows the odontoid process to migrate upward into the foramen magnum, causing brainstem compression, lower cranial nerve palsies, and upper motor neuron signs (hyperreflexia).

Question 7288

Topic: 6. Spine

Pseudoachondroplasia shares some phenotypic similarities with achondroplasia but has distinct clinical and radiographic differences. Which of the following spinal characteristics is typical of pseudoachondroplasia but NOT achondroplasia?

. Decreased interpedicular distance in the lumbar spine
. Severe narrowing of the foramen magnum
. Normal facial features and head circumference
. Anterior beaking of the vertebral bodies in adulthood
. High incidence of atlantoaxial instability

Correct Answer & Explanation

. High incidence of atlantoaxial instability

Explanation

Correct Answer: High incidence of atlantoaxial instabilityPseudoachondroplasia (COMP mutation) presents with normal facial features and head circumference, unlike achondroplasia. In the spine, pseudoachondroplasia is characterized by platyspondyly, anterior tongue-like projections of the vertebrae in childhood, and a high risk of atlantoaxial instability due to odontoid hypoplasia. Achondroplasia typically does NOT have atlantoaxial instability; instead, it features foramen magnum stenosis and lumbar spinal stenosis.

Question 7289

Topic: 6. Spine
In evaluating a child with a suspected mucopolysaccharidosis (MPS), lateral radiographs of the thoracolumbar spine are obtained. The presence of anterior-inferior beaking of the vertebral bodies is most characteristic of which specific MPS type?
. MPS I (Hurler syndrome)
. MPS IV (Morquio syndrome)
. MPS III (Sanfilippo syndrome)
. MPS II (Hunter syndrome)
. MPS IX (Natowicz syndrome)

Correct Answer & Explanation

. MPS I (Hurler syndrome)

Explanation

Vertebral beaking is a classic radiographic sign in Mucopolysaccharidoses. The location of the beak helps differentiate the types. In Hurler syndrome (MPS I), the beaking is typically located at the anterior-inferior aspect of the vertebral body. In contrast, Morquio syndrome (MPS IV) typically presents with central anterior beaking.

Question 7290

Topic: 6. Spine

A 35-year-old male with achondroplasia presents with severe neurogenic claudication refractory to conservative management. MRI confirms severe multilevel lumbar spinal stenosis. When performing a decompressive laminectomy in this patient, which of the following technical considerations is most critical due to the specific pathoanatomy of the condition?

. Routine use of interspinous process distraction devices
. Wide laminectomy extending laterally to the pars interarticularis, often requiring concurrent fusion
. Limited central laminotomy to preserve the hypertrophic facet joints
. Anterior lumbar interbody fusion (ALIF) as the primary decompressive maneuver
. Extensive resection of the pedicles and wide lateral recess decompression due to the short pedicles

Correct Answer & Explanation

. Extensive resection of the pedicles and wide lateral recess decompression due to the short pedicles

Explanation

Correct Answer: Extensive resection of the pedicles and wide lateral recess decompression due to the short pediclesIn achondroplasia, lumbar stenosis is primarily due to short pedicles, thickened laminae, and a decreased interpedicular distance. The nerve roots are severely compressed in the lateral recess and foramina. A standard central laminectomy is insufficient. The decompression must be wide, extending into the lateral recesses, and often requires partial or complete pediculectomies to adequately free the nerve roots. This extensive bone removal may necessitate concurrent fusion if instability is created.

Question 7291

Topic: 6. Spine

A 6-year-old boy with Morquio syndrome (Mucopolysaccharidosis type IV) is being evaluated prior to a general anesthetic procedure for hernia repair. Which of the following spinal abnormalities is most critical to rule out in this patient to prevent catastrophic neurologic injury during intubation?

. Thoracolumbar kyphosis
. Atlantoaxial instability due to odontoid hypoplasia
. Severe lumbar spinal stenosis
. Isthmic spondylolisthesis
. Cervical kyphosis

Correct Answer & Explanation

. Atlantoaxial instability due to odontoid hypoplasia

Explanation

Correct Answer: Atlantoaxial instability due to odontoid hypoplasiaPatients with Morquio syndrome (MPS IV) frequently have severe odontoid hypoplasia and ligamentous laxity, leading to profound atlantoaxial instability. Extension of the neck during endotracheal intubation can cause catastrophic spinal cord compression at the craniocervical junction. Therefore, flexion-extension radiographs of the cervical spine (and potentially an MRI) are mandatory prior to any procedure requiring general anesthesia.

Question 7292

Topic: 6. Spine

A 3-year-old child with diastrophic dysplasia is noted to have a cervical kyphosis on routine radiographic screening. Which of the following statements regarding cervical kyphosis in this specific condition is most accurate?

. It invariably progresses to severe neurologic deficit requiring early fusion.
. It is typically caused by a failure of formation of the C4 vertebral body.
. It often resolves spontaneously, but requires close radiographic monitoring.
. It is best treated with a halo vest until skeletal maturity.
. It is rarely associated with spina bifida occulta of the cervical spine.

Correct Answer & Explanation

. It often resolves spontaneously, but requires close radiographic monitoring.

Explanation

Correct Answer: It often resolves spontaneously, but requires close radiographic monitoring.Cervical kyphosis is a well-known manifestation of diastrophic dysplasia. Unlike cervical kyphosis in many other conditions, the deformity in diastrophic dysplasia often resolves spontaneously as the child grows. However, a subset of patients will experience progression leading to severe deformity and neurologic compromise. Therefore, close radiographic monitoring is essential. Spina bifida occulta of the cervical spine is actually very common in these patients.

Question 7293

Topic: 6. Spine

An adult patient with achondroplasia presents with severe neurogenic claudication. The underlying pathophysiology of spinal stenosis in this patient population is primarily related to which of the following anatomical abnormalities?

. Hypertrophy of the ligamentum flavum and facet joints
. Decreased interpedicular distance from L1 to L5 and short pedicles
. Severe degenerative scoliosis with rotatory subluxation
. Congenital absence of the lumbar pedicles
. Isthmic spondylolisthesis at multiple levels

Correct Answer & Explanation

. Decreased interpedicular distance from L1 to L5 and short pedicles

Explanation

Correct Answer: Decreased interpedicular distance from L1 to L5 and short pediclesSpinal stenosis in achondroplasia is primarily congenital, caused by a failure of normal endochondral ossification. This results in abnormally short, thick pedicles and a characteristic decrease in the interpedicular distance from L1 to L5 (in normal individuals, this distance increases). While degenerative changes like disc herniation or ligamentum flavum hypertrophy can exacerbate the symptoms later in life, the fundamental anatomical defect is the congenitally narrow bony canal.

Question 7294

Topic: Thoracolumbar Spine & Deformity

A patient with severe cervical kyphosis, 'hitchhiker' thumbs, and cauliflower ears is diagnosed with a skeletal dysplasia. The genetic mutation responsible for this condition primarily affects which of the following cellular functions?

. Fibroblast growth factor signaling
. Type II collagen synthesis
. Sulfate transport across the cell membrane
. Osteoclast-mediated bone resorption
. Cartilage oligomeric matrix protein assembly

Correct Answer & Explanation

. Sulfate transport across the cell membrane

Explanation

Correct Answer: Sulfate transport across the cell membraneThe clinical triad of cervical kyphosis, hitchhiker thumbs, and cauliflower ears is pathognomonic for diastrophic dysplasia. This autosomal recessive condition is caused by mutations in the SLC26A2 (DTDST) gene, which encodes a sulfate transporter. Defective sulfate transport leads to undersulfation of proteoglycans in the cartilage matrix, resulting in the characteristic skeletal and cartilaginous abnormalities.

Question 7295

Topic: 6. Spine

A 45-year-old male with achondroplasia presents with neurogenic claudication. The primary anatomic cause of his spinal stenosis is most accurately described by which of the following?

. Hypertrophy of the ligamentum flavum and facet joints
. Decreasing interpedicular distance from L1 to L5
. Anterior slippage of L4 on L5
. Progressive thoracolumbar kyphosis
. Congenital absence of the lumbar pedicles

Correct Answer & Explanation

. Decreasing interpedicular distance from L1 to L5

Explanation

In achondroplasia, premature closure of the neurocentral synchondroses leads to abnormally short pedicles and a characteristic narrowing of the interpedicular distance from L1 to L5. This congenital narrowing predisposes them to symptomatic spinal stenosis later in life.

Question 7296

Topic: 6. Spine

A 6-year-old child with a skeletal dysplasia presents with a thoracolumbar kyphosis. Lateral spine radiographs demonstrate anterior vertebral body beaking that is predominantly located in the central portion of the vertebral body. Which enzyme deficiency is most likely responsible for this condition?

. Alpha-L-iduronidase
. Galactosamine-6-sulfatase
. Fibroblast growth factor receptor 3
. Cartilage oligomeric matrix protein
. Type II collagen

Correct Answer & Explanation

. Galactosamine-6-sulfatase

Explanation

Central anterior vertebral beaking is characteristic of Morquio syndrome (MPS IV), which is caused by a deficiency in galactosamine-6-sulfatase (MPS IVA) or beta-galactosidase (MPS IVB). In contrast, Hurler syndrome (alpha-L-iduronidase deficiency) features inferior anterior vertebral beaking.

Question 7297

Topic: 6. Spine

A 3-year-old child with diastrophic dysplasia is being evaluated for a cervical spine deformity. Lateral radiographs reveal mid-cervical kyphosis. Which of the following anatomic anomalies is most characteristically associated with this specific spinal deformity?

. Odontoid hypoplasia
. Coronal clefts of the vertebral bodies
. Spina bifida occulta at the apex of the kyphosis
. Congenital facet dislocation
. Atlantoaxial rotatory subluxation

Correct Answer & Explanation

. Spina bifida occulta at the apex of the kyphosis

Explanation

Cervical kyphosis in diastrophic dysplasia is classically associated with spina bifida occulta at the apex of the deformity. While upper cervical kyphosis in this condition often resolves spontaneously, lower cervical curves tend to progress and may require surgical stabilization.

Question 7298

Topic: 6. Spine
A 12-year-old patient with severe Osteogenesis Imperfecta (Type III) develops progressive upper extremity weakness, hyperreflexia, and lower cranial nerve deficits. What is the most appropriate imaging modality to evaluate the most likely etiology of these new symptoms?
. Upright AP and lateral scoliosis radiographs
. CT scan of the thoracolumbar spine
. MRI of the craniocervical junction
. Flexion-extension radiographs of the lumbar spine
. Bone scintigraphy

Correct Answer & Explanation

. MRI of the craniocervical junction

Explanation

The patient's symptoms suggest brainstem and cranial nerve compression secondary to basilar invagination, a known severe complication of Osteogenesis Imperfecta. MRI of the craniocervical junction is the gold standard for assessing neural compression and structural anatomy in this region.

Question 7299

Topic: 6. Spine

An infant with achondroplasia is noted to have hypotonia, apnea, and hyperreflexia of the lower extremities. Which of the following is the most appropriate definitive management for this patient's condition?

. Bracing with a thoracolumbosacral orthosis (TLSO)
. Observation and continuous positive airway pressure (CPAP)
. Cervicothoracic spinal fusion
. Foramen magnum decompression
. Posterior C1-C2 fusion

Correct Answer & Explanation

. Foramen magnum decompression

Explanation

Infants with achondroplasia can develop severe foramen magnum stenosis leading to cervicomedullary compression, presenting with central apnea, hypotonia, and myelopathy. Urgent neurosurgical decompression of the foramen magnum is required to prevent sudden death and neurologic deterioration.

Question 7300

Topic: 6. Spine

A 6-year-old boy with a known COMP gene mutation presents for routine follow-up. He has short-limb dwarfism but normal facial features. Which of the following spinal abnormalities is most critical to screen for in this patient?

. Decreased interpedicular distance
. Spondylolisthesis at L5-S1
. Odontoid hypoplasia and C1-C2 instability
. Progressive thoracolumbar kyphosis
. Spina bifida occulta of the cervical spine

Correct Answer & Explanation

. Odontoid hypoplasia and C1-C2 instability

Explanation

A COMP gene mutation causes pseudoachondroplasia, characterized by normal facial features and short-limb dwarfism. Patients are at high risk for odontoid hypoplasia and significant atlantoaxial (C1-C2) instability, which requires strict radiographic screening.

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