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6. Spine MCQs

Practice Set 359 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 7161

Topic: 6. Spine

A 6-month-old infant is diagnosed with diastrophic dysplasia. Radiographs demonstrate a significant cervical kyphosis. What is the typical natural history and recommended initial management for this specific spinal deformity?

. It is relentlessly progressive and requires immediate anterior and posterior spinal fusion
. It often resolves spontaneously with growth, but requires close radiographic observation
. It is caused by a tethered spinal cord and requires urgent neurosurgical release
. It inevitably leads to quadriplegia without prophylactic anterior decompression
. It is associated with basilar invagination requiring occipitocervical fusion

Correct Answer & Explanation

. It often resolves spontaneously with growth, but requires close radiographic observation

Explanation

Correct Answer: It often resolves spontaneously with growth, but requires close radiographic observationIn diastrophic dysplasia (caused by a mutation in the SLC26A2 gene), cervical kyphosis is a common finding in infancy. Unlike the severe, progressive scoliosis seen in this condition, the cervical kyphosis resolves spontaneously in the majority of cases as the child grows and gains head control. However, it must be closely monitored, as a subset of patients will experience progression requiring surgical stabilization.

Question 7162

Topic: 6. Spine

A 12-month-old infant with achondroplasia is noted to have a 35-degree thoracolumbar kyphosis. Neurological examination is normal. What is the most appropriate initial management?

. Anterior and posterior spinal fusion
. Posterior spinal fusion alone
. Extension bracing (e.g., TLSO)
. Avoidance of unsupported sitting and observation
. Immediate MRI of the entire spine

Correct Answer & Explanation

. Avoidance of unsupported sitting and observation

Explanation

Correct Answer: Avoidance of unsupported sitting and observationThoracolumbar kyphosis is present in over 90% of infants with achondroplasia. It is primarily postural, exacerbated by hypotonia and a large head size. The initial management is conservative, focusing on avoiding unsupported sitting and carrying the child in a way that supports the spine. With these measures and the development of independent walking, the kyphosis resolves in the vast majority of cases. Bracing or surgery is reserved for persistent, severe, or rigid deformities.

Question 7163

Topic: 6. Spine
A 14-year-old female with Osteogenesis Imperfecta Type IV presents with new-onset occipital headaches, hyperreflexia, and lower cranial nerve deficits. Which of the following is the most likely diagnosis?
. Atlantoaxial rotatory subluxation
. Basilar invagination
. Syringomyelia
. Odontoid fracture
. Thoracolumbar kyphoscoliosis

Correct Answer & Explanation

. Basilar invagination

Explanation

Basilar invagination is a severe complication of Osteogenesis Imperfecta (OI), particularly in Types IV and III. It occurs due to the softening of the skull base, allowing the odontoid process to migrate upward into the foramen magnum. This leads to direct brainstem and lower cranial nerve compression, presenting with occipital headaches, myelopathy (hyperreflexia), and cranial nerve palsies.

Question 7164

Topic: 6. Spine

A 5-year-old child presents with short-limb dwarfism, normal facial features, and normal intelligence. Radiographs show platyspondyly with anterior tongue-like projections of the vertebral bodies. Unlike achondroplasia, which of the following spinal conditions is a major concern in this patient?

. Severe lumbar spinal stenosis
. Atlantoaxial instability due to odontoid hypoplasia
. Progressive basilar invagination
. Foramen magnum stenosis
. Spontaneous cervical epidural hematoma

Correct Answer & Explanation

. Atlantoaxial instability due to odontoid hypoplasia

Explanation

Correct Answer: Atlantoaxial instability due to odontoid hypoplasiaThe clinical picture (short-limb dwarfism, normal facies, normal intelligence) and radiographic findings (anterior tongue-like projections of vertebrae) are classic for pseudoachondroplasia (COMP gene mutation). Unlike achondroplasia, which is characterized by foramen magnum stenosis and lumbar spinal stenosis, pseudoachondroplasia frequently involves odontoid hypoplasia, leading to a high risk of atlantoaxial instability.

Question 7165

Topic: 6. Spine

In patients with Mucopolysaccharidosis (e.g., Hurler or Morquio syndrome), spinal cord compression at the craniocervical junction is a well-documented complication. Which of the following best describes the primary pathophysiological mechanism for this compression?

. Hypertrophy of the posterior longitudinal ligament
. Accumulation of glycosaminoglycans in the periodontoid soft tissues combined with odontoid hypoplasia
. Premature fusion of the neurocentral synchondroses
. Severe fixed cervical kyphosis due to anterior vertebral wedging
. Dural ectasia leading to secondary spinal cord tethering

Correct Answer & Explanation

. Accumulation of glycosaminoglycans in the periodontoid soft tissues combined with odontoid hypoplasia

Explanation

Correct Answer: Accumulation of glycosaminoglycans in the periodontoid soft tissues combined with odontoid hypoplasiaIn mucopolysaccharidoses, the deficiency of specific lysosomal enzymes leads to the accumulation of glycosaminoglycans (GAGs) in various tissues. In the cervical spine, GAG deposition thickens the transverse ligament and periodontoid soft tissues. This soft tissue mass, combined with the bony instability caused by odontoid hypoplasia, leads to severe spinal cord compression at the craniocervical junction.

Question 7166

Topic: 6. Spine

A 7-year-old boy with Morquio syndrome (Mucopolysaccharidosis Type IV) presents with increasing clumsiness, hyperreflexia in the lower extremities, and a positive Babinski sign. Which of the following pathophysiological mechanisms is the primary cause of cervical myelopathy in this specific patient population?

. Short pedicles and decreased interpedicular distance in the cervical spine
. Odontoid hypoplasia combined with thickened periodontoid soft tissue (pannus)
. Premature fusion of the neurocentral synchondrosis
. Severe rigid cervical kyphosis due to failure of vertebral formation
. Foramen magnum stenosis resulting from failure of endochondral ossification

Correct Answer & Explanation

. Odontoid hypoplasia combined with thickened periodontoid soft tissue (pannus)

Explanation

Correct Answer: Odontoid hypoplasia combined with thickened periodontoid soft tissue (pannus)Morquio syndrome (MPS IV) is characterized by the accumulation of keratan sulfate. In the cervical spine, this leads to two major issues: odontoid hypoplasia (causing ligamentous laxity and atlantoaxial instability) and the accumulation of mucopolysaccharides in the periodontoid soft tissues, creating a thickened 'pannus'. This combination leads to severe upper cervical spinal stenosis and myelopathy. Foramen magnum stenosis is characteristic of achondroplasia, not Morquio syndrome.

Question 7167

Topic: 6. Spine

A newborn is diagnosed with diastrophic dysplasia. Clinical examination reveals a 'hitchhiker thumb' and cauliflower ears. Radiographs of the cervical spine demonstrate a cervical kyphosis. Which of the following anatomical anomalies is classically associated with the cervical kyphosis seen in this condition?

. Spina bifida occulta of the cervical vertebrae
. Atlantoaxial rotatory fixation
. Congenital absence of the C2 pedicles
. Basilar invagination
. Klippel-Feil anomaly (failure of segmentation)

Correct Answer & Explanation

. Spina bifida occulta of the cervical vertebrae

Explanation

Correct Answer: Spina bifida occulta of the cervical vertebraeDiastrophic dysplasia is caused by a mutation in the DTDST gene (SLC26A2), which affects sulfate transport. Cervical kyphosis is a common and potentially dangerous manifestation. It is classically associated with spina bifida occulta of the cervical spine. While mild cases may resolve spontaneously, severe or progressive cervical kyphosis in these patients requires close monitoring and potentially posterior spinal fusion to prevent catastrophic neurological injury.

Question 7168

Topic: 6. Spine

A 5-year-old child with Spondyloepiphyseal Dysplasia Congenita (SEDC) is scheduled for bilateral femoral osteotomies to correct severe coxa vara. Prior to clearance for general anesthesia, which of the following is the most critical screening study required?

. MRI of the lumbar spine to rule out tethered cord
. Flexion-extension lateral radiographs of the cervical spine
. CT scan of the chest to assess pulmonary hypoplasia
. DEXA scan to evaluate bone mineral density
. Ultrasound of the kidneys to rule out congenital anomalies

Correct Answer & Explanation

. Flexion-extension lateral radiographs of the cervical spine

Explanation

Correct Answer: Flexion-extension lateral radiographs of the cervical spineSEDC is a Type II collagenopathy (COL2A1 mutation). Patients with SEDC frequently have odontoid hypoplasia, which leads to atlantoaxial instability (AAI). Because intubation for general anesthesia involves manipulation and extension of the neck, unrecognized AAI can lead to catastrophic spinal cord injury. Therefore, flexion-extension lateral radiographs of the cervical spine are mandatory prior to any surgical procedure requiring general anesthesia in these patients.

Question 7169

Topic: 6. Spine

During decompressive laminectomy for severe lumbar spinal stenosis in a 45-year-old adult with achondroplasia, which of the following anatomical features necessitates a wider and more meticulous lateral decompression compared to degenerative stenosis in a non-dysplastic patient?

. Hypertrophy of the uncinate processes
. Markedly decreased interpedicular distance and short pedicles
. Severe central anterior vertebral beaking
. Ossification of the posterior longitudinal ligament
. Congenital absence of the pars interarticularis

Correct Answer & Explanation

. Markedly decreased interpedicular distance and short pedicles

Explanation

Correct Answer: Markedly decreased interpedicular distance and short pediclesAchondroplasia is caused by an FGFR3 mutation affecting endochondral ossification. In the spine, this manifests as short, thickened pedicles and a progressively decreased interpedicular distance from the upper lumbar spine down to the sacrum (the opposite of normal anatomy). This congenital narrowing, combined with degenerative changes (disc bulging, ligamentum flavum hypertrophy), causes severe stenosis. Surgical decompression requires a wide laminectomy that extends laterally to decompress the nerve roots fully, often requiring partial or complete facetectomies due to the narrowed interpedicular distance.

Question 7170

Topic: 6. Spine

A 6-year-old child presents with disproportionate short stature, normal facial features, and normal head circumference. Radiographs reveal platyspondyly with anterior tongue-like projections of the vertebral bodies. Which of the following spinal complications is most critical to screen for in this specific dysplasia?

. Foramen magnum stenosis
. Atlantoaxial instability
. Severe progressive lumbar kyphosis
. Isthmic spondylolisthesis
. Tethered cord syndrome

Correct Answer & Explanation

. Atlantoaxial instability

Explanation

Correct Answer: Atlantoaxial instabilityThe clinical presentation (short stature, normal face/head) and radiographic findings (platyspondyly with anterior tongue-like projections) are classic for Pseudoachondroplasia, which is caused by a mutation in the Cartilage Oligomeric Matrix Protein (COMP) gene. Unlike achondroplasia (which features a large head, frontal bossing, and foramen magnum stenosis), pseudoachondroplasia patients have normal craniofacial features but are at high risk for atlantoaxial instability due to odontoid hypoplasia and ligamentous laxity. Screening for AAI is critical.

Question 7171

Topic: 6. Spine

A 4-year-old child with a skeletal dysplasia undergoes a lateral spine radiograph, which demonstrates platyspondyly with distinct central anterior beaking of the vertebral bodies. Which of the following enzyme deficiencies is most likely responsible for this condition?

. Alpha-L-iduronidase
. N-acetylgalactosamine-6-sulfatase
. Iduronate-2-sulfatase
. Arylsulfatase B
. Glucocerebrosidase

Correct Answer & Explanation

. N-acetylgalactosamine-6-sulfatase

Explanation

Correct Answer: N-acetylgalactosamine-6-sulfataseThe radiographic finding of central anterior beaking of the vertebral bodies is characteristic of Morquio syndrome (Mucopolysaccharidosis Type IV). Morquio Type A is caused by a deficiency in N-acetylgalactosamine-6-sulfatase (GALNS). In contrast, Hurler syndrome (MPS I), caused by Alpha-L-iduronidase deficiency, classically presents with anteroinferior beaking of the vertebral bodies.

Question 7172

Topic: 6. Spine

A 10-month-old infant with achondroplasia is evaluated in the clinic. Which of the following clinical findings is the strongest indication for urgent neurosurgical decompression of the foramen magnum?

. Delayed independent walking
. Thoracolumbar kyphosis of 25 degrees
. Central sleep apnea with lower extremity hyperreflexia
. Frontal bossing with a prominent abdomen
. Decreased interpedicular distance in the lumbar spine

Correct Answer & Explanation

. Central sleep apnea with lower extremity hyperreflexia

Explanation

Correct Answer: Central sleep apnea with lower extremity hyperreflexiaForamen magnum stenosis is a life-threatening complication in infants with achondroplasia, caused by premature fusion of the synchondroses at the skull base. Symptoms of severe cervicomedullary compression include central sleep apnea, profound hypotonia, hyperreflexia, clonus, and sudden death. The presence of central sleep apnea and upper motor neuron signs (hyperreflexia) is an absolute indication for urgent neurosurgical decompression (suboccipital craniectomy and C1 laminectomy).

Question 7173

Topic: 6. Spine

A 35-year-old male with achondroplasia presents with severe neurogenic claudication and bilateral lower extremity weakness. He is planned for surgical decompression. Which of the following anatomical abnormalities is the primary driver of his lumbar spinal stenosis?

. Hypertrophy of the facet joints and ligamentum flavum
. Degenerative spondylolisthesis of L4 on L5
. Decreased interpedicular distance and short pedicles
. Ossification of the posterior longitudinal ligament (OPLL)
. Severe lumbar lordosis causing kissing spines (Baastrup disease)

Correct Answer & Explanation

. Decreased interpedicular distance and short pedicles

Explanation

Correct Answer: CIn achondroplasia, the primary cause of spinal stenosis is a congenital narrowing of the spinal canal due to premature fusion of the neurocentral synchondroses. This results in short pedicles and a progressively decreased interpedicular distance from the upper lumbar spine to the lower lumbar spine (the opposite of the normal anatomical widening). While degenerative changes like ligamentum flavum hypertrophy can exacerbate the condition later in life, the fundamental pathoanatomy is the bony constriction caused by the short pedicles and decreased interpedicular distance.

Question 7174

Topic: 6. Spine

A 7-year-old child with Morquio syndrome (Mucopolysaccharidosis type IV) is scheduled for bilateral femoral osteotomies to correct severe genu valgum. What is the most critical preoperative evaluation required before administering general anesthesia?

. Flexion-extension radiographs of the cervical spine
. Echocardiogram to assess for aortic root dilation
. Pulmonary function tests
. Renal ultrasound to rule out hydronephrosis
. MRI of the lumbar spine to rule out tethered cord

Correct Answer & Explanation

. Flexion-extension radiographs of the cervical spine

Explanation

Correct Answer: AMorquio syndrome (MPS IV) is highly associated with odontoid hypoplasia and ligamentous laxity, leading to severe atlantoaxial (C1-C2) instability. This poses a lethal risk during intubation and positioning for surgery due to the potential for spinal cord compression. Therefore, flexion-extension radiographs of the cervical spine (and often an MRI) are mandatory preoperative requirements to clear the patient for general anesthesia.

Question 7175

Topic: 6. Spine

A 6-month-old infant with diastrophic dysplasia is noted to have a cervical kyphosis on lateral radiographs. Neurological examination is normal. Which of the following cervical spine abnormalities is classically associated with the development of this kyphosis in diastrophic dysplasia?

. Odontoid hypoplasia
. Congenital block vertebrae at C2-C3
. Atlanto-occipital assimilation
. Spina bifida occulta of the cervical vertebrae
. Ossification of the ligamentum flavum

Correct Answer & Explanation

. Spina bifida occulta of the cervical vertebrae

Explanation

Correct Answer: DCervical kyphosis in diastrophic dysplasia is a classic and potentially dangerous manifestation. It is strongly associated with spina bifida occulta of the cervical vertebrae and hypoplasia of the vertebral bodies. While many cases of mild cervical kyphosis in diastrophic dysplasia resolve spontaneously as the child grows and gains head control, severe or progressive cases require close monitoring and potentially posterior cervical fusion to prevent neurological compromise.

Question 7176

Topic: 6. Spine

A 5-year-old boy presents with disproportionate short stature, a barrel chest, and a waddling gait. Radiographs reveal platyspondyly, delayed ossification of the pubic bones, and severe coxa vara. Based on the most likely diagnosis, which of the following spine pathologies must be urgently ruled out?

. Thoracolumbar kyphosis
. Lumbar spinal stenosis
. Spondylolysis
. Tethered cord syndrome
. Atlantoaxial instability

Correct Answer & Explanation

. Atlantoaxial instability

Explanation

Correct Answer: EThe clinical and radiographic presentation (disproportionate short trunk dwarfism, platyspondyly, delayed pubic ossification, and severe coxa vara) is classic for Spondyloepiphyseal Dysplasia Congenita (SEDC). SEDC is a type II collagenopathy. A critical and potentially life-threatening feature of SEDC is odontoid hypoplasia, which leads to atlantoaxial instability. This must be ruled out with cervical spine imaging to prevent catastrophic neurological injury.

Question 7177

Topic: 6. Spine

When evaluating the lateral spine radiographs of a child with a suspected skeletal dysplasia, you note distinct anterior beaking of the vertebral bodies. Which of the following radiographic features best differentiates Morquio syndrome (MPS IV) from Hurler syndrome (MPS I)?

. Morquio syndrome features anteroinferior beaking, while Hurler features central beaking.
. Morquio syndrome features central anterior beaking, while Hurler features anteroinferior beaking.
. Morquio syndrome features posterior scalloping, which is absent in Hurler syndrome.
. Hurler syndrome is associated with severe platyspondyly, while Morquio has normal vertebral height.
. Hurler syndrome features coronal clefts, while Morquio features sagittal clefts.

Correct Answer & Explanation

. Morquio syndrome features central anterior beaking, while Hurler features anteroinferior beaking.

Explanation

Correct Answer: BVertebral beaking is a hallmark of several mucopolysaccharidoses. A classic radiographic distinction is that Morquio syndrome (MPS IV) typically presents with central anterior beaking of the vertebral bodies, whereas Hurler syndrome (MPS I) typically presents with anteroinferior beaking. Both conditions can exhibit platyspondyly and posterior vertebral scalloping.

Question 7178

Topic: 6. Spine

You are performing a multi-level lumbar laminectomy for severe spinal stenosis in a 40-year-old patient with achondroplasia. Due to the unique pathoanatomy of this condition, which of the following intraoperative complications is the surgeon at highest risk of encountering?

. Massive hemorrhage from anomalous vertebral arteries
. Iatrogenic pars interarticularis fracture due to widened interpedicular distance
. Inadvertent sympathectomy
. Dural tear due to epidural venous engorgement and a tightly adherent dura
. Injury to the thoracic duct

Correct Answer & Explanation

. Dural tear due to epidural venous engorgement and a tightly adherent dura

Explanation

Correct Answer: DSurgical decompression in achondroplasia is notoriously difficult. The spinal canal is severely stenotic, the epidural space is virtually non-existent, and the epidural veins are often massively engorged due to altered venous drainage. Furthermore, the dura is frequently tightly adherent to the surrounding bone and ligamentum flavum. This combination makes dural tears the most common and significant intraoperative complication during laminectomy in these patients.

Question 7179

Topic: 6. Spine

A 4-year-old child presents with disproportionate short trunk dwarfism, a flat midface, prominent joints, and a cleft palate. Spine radiographs reveal coronal clefts of the vertebral bodies and severe kyphoscoliosis. Which of the following is the most likely diagnosis?

. Chondrodysplasia punctata
. Kniest dysplasia
. Metatropic dysplasia
. Campomelic dysplasia
. Multiple epiphyseal dysplasia

Correct Answer & Explanation

. Kniest dysplasia

Explanation

Correct Answer: BKniest dysplasia is a type II collagenopathy characterized by short trunk dwarfism, prominent/enlarged joints (due to epiphyseal dysplasia), midface hypoplasia, myopia, and frequently a cleft palate. A classic radiographic hallmark in the spine is the presence of coronal clefts in the vertebral bodies, along with platyspondyly and progressive kyphoscoliosis. Dumbbell-shaped femora are also a classic appendicular finding.

Question 7180

Topic: 6. Spine

A 3-year-old child with diastrophic dysplasia is evaluated for a cervical kyphotic deformity of 35 degrees. The parents are concerned about the need for surgery. Which of the following anatomical features is most characteristically associated with the development of cervical kyphosis in this specific skeletal dysplasia?

. Odontoid hypoplasia leading to atlantoaxial instability
. Spina bifida occulta of the cervical vertebrae
. Anterior central vertebral beaking
. Decreased interpedicular distance in the cervical spine
. Basilar invagination due to bone fragility

Correct Answer & Explanation

. Spina bifida occulta of the cervical vertebrae

Explanation

Correct Answer: Spina bifida occulta of the cervical vertebraeCervical kyphosis is a classic spinal manifestation of diastrophic dysplasia (a sulfate transporter defect, SLC26A2). It is characteristically associated with spina bifida occulta of the cervical spine. In many cases, mild to moderate cervical kyphosis in diastrophic dysplasia resolves spontaneously with growth, but severe or progressive cases require posterior fusion. Odontoid hypoplasia is characteristic of SED and Morquio syndrome. Anterior beaking is seen in Morquio and Hurler syndromes.

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