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6. Spine MCQs

Practice Set 364 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 7261

Topic: Cervical Spine

A 60-year-old woman with long-standing rheumatoid arthritis presents with new-onset myelopathy. Flexion-extension cervical radiographs reveal an atlantodental interval (ADI) of 10 mm. Which ligament's failure is primarily responsible for this radiographic finding?

. Apical ligament
. Alar ligament
. Transverse ligament
. Posterior longitudinal ligament
. Ligamentum flavum

Correct Answer & Explanation

. Transverse ligament

Explanation

Atlantoaxial subluxation in rheumatoid arthritis is primarily due to the destruction and laxity of the transverse ligament. This is caused by the invasive synovial pannus at the atlanto-odontoid joint.

Question 7262

Topic: 6. Spine

A 5-year-old boy with Spondyloepiphyseal Dysplasia Congenita (SEDC) is scheduled for bilateral femoral osteotomies to correct severe coxa vara. During the preoperative evaluation, which of the following screening tests is most critical to perform before proceeding with general anesthesia?

. Echocardiogram
. Flexion-extension cervical spine radiographs
. Renal ultrasound
. Pulmonary function tests
. MRI of the lumbar spine

Correct Answer & Explanation

. Flexion-extension cervical spine radiographs

Explanation

Correct Answer: Flexion-extension cervical spine radiographsPatients with SEDC frequently have odontoid hypoplasia, which can lead to severe atlantoaxial instability. This instability poses a significant risk of spinal cord injury during neck extension, particularly during endotracheal intubation. Therefore, flexion-extension cervical spine radiographs are mandatory prior to any surgical procedure requiring general anesthesia in these patients.

Question 7263

Topic: 6. Spine

A neonate is diagnosed with diastrophic dysplasia. The orthopedic surgeon notes a spinal deformity during the initial assessment. Which of the following spinal deformities associated with this condition is most likely to resolve spontaneously?

. Cervical kyphosis
. Thoracic scoliosis
. Lumbar hyperlordosis
. Atlantoaxial instability
. Basilar invagination

Correct Answer & Explanation

. Cervical kyphosis

Explanation

Correct Answer: Cervical kyphosisCervical kyphosis is a common finding in infants with diastrophic dysplasia. Unlike cervical kyphosis in other conditions (such as Larsen syndrome or neurofibromatosis), the cervical kyphosis in diastrophic dysplasia often resolves spontaneously with growth. However, these patients are at high risk for developing severe, progressive scoliosis later in childhood, which requires close monitoring.

Question 7264

Topic: 6. Spine

A 7-year-old child presents with short-trunk dwarfism, normal intelligence, and corneal clouding. The parents report that the child has been experiencing increasing weakness in the hands and frequent falls. Radiographs of the spine show severe platyspondyly and central anterior vertebral beaking. A deficiency in which of the following enzymes is most likely responsible for this presentation?

. Iduronate-2-sulfatase
. Alpha-L-iduronidase
. Galactosamine-6-sulfatase
. Arylsulfatase B
. Fibroblast growth factor receptor 3

Correct Answer & Explanation

. Galactosamine-6-sulfatase

Explanation

Correct Answer: Galactosamine-6-sulfataseThe clinical presentation of short-trunk dwarfism, normal intelligence, corneal clouding, and central anterior vertebral beaking is classic for Morquio syndrome (Mucopolysaccharidosis Type IV). Morquio A is caused by a deficiency in N-acetylgalactosamine-6-sulfatase. These patients are at extremely high risk for atlantoaxial instability due to odontoid hypoplasia and ligamentous laxity, which explains the myelopathic symptoms (hand weakness, falls).

Question 7265

Topic: 6. Spine

A 35-year-old male with achondroplasia presents with bilateral leg pain, numbness, and weakness that worsens with walking and improves when he bends forward or sits down. What is the primary anatomical cause of his symptoms?

. Hypertrophy of the ligamentum flavum
. Decreased interpedicular distance
. Degenerative spondylolisthesis
. Severe lumbar scoliosis
. Herniated nucleus pulposus

Correct Answer & Explanation

. Decreased interpedicular distance

Explanation

Correct Answer: Decreased interpedicular distanceThe patient is presenting with neurogenic claudication due to lumbar spinal stenosis, which is very common in adults with achondroplasia. The primary anatomical basis for this stenosis is the abnormal endochondral ossification that leads to short, thickened pedicles and a progressively decreased interpedicular distance from the upper to the lower lumbar spine. While disc herniations or ligamentum flavum hypertrophy can exacerbate the condition, the fundamental cause is the congenitally narrow bony canal.

Question 7266

Topic: 6. Spine
A 14-year-old patient with Osteogenesis Imperfecta Type IV presents with new-onset headaches, lower cranial nerve deficits (difficulty swallowing), and hyperreflexia in all four extremities. What is the most likely spinal complication causing these symptoms?
. Atlantoaxial rotatory subluxation
. Basilar invagination
. Thoracolumbar kyphosis
. Lumbar spondylolysis
. Syringomyelia

Correct Answer & Explanation

. Basilar invagination

Explanation

Basilar invagination (or basilar impression) is a severe complication of Osteogenesis Imperfecta, particularly in Types III and IV. 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 compression of the brainstem and lower cranial nerves, presenting with headaches, dysphagia, and upper motor neuron signs.

Question 7267

Topic: 6. Spine

A 6-month-old infant with achondroplasia is evaluated for delayed motor milestones. The parents report episodes where the infant stops breathing during sleep. Examination reveals hyperreflexia and sustained clonus. What is the most appropriate management?

. Observation and repeat examination in 3 months
. Continuous positive airway pressure (CPAP) at night
. Suboccipital craniectomy and C1 laminectomy
. Posterior spinal fusion of the cervical spine
. Halo gravity traction

Correct Answer & Explanation

. Suboccipital craniectomy and C1 laminectomy

Explanation

Correct Answer: Suboccipital craniectomy and C1 laminectomyThe infant is exhibiting signs of severe foramen magnum stenosis, a life-threatening complication in achondroplasia. Symptoms include central sleep apnea, hyperreflexia, clonus, and delayed motor milestones. Symptomatic foramen magnum stenosis requires urgent surgical decompression (suboccipital craniectomy and C1 laminectomy) to relieve brainstem compression and prevent sudden infant death.

Question 7268

Topic: 6. Spine

A neonate presents with short-limbed dwarfism, bilateral rigid clubfeet, 'hitchhiker' thumbs, and cystic swelling of the pinnae. Radiographs of the spine are obtained. Which of the following spinal abnormalities is most classically associated with this syndrome at this age?

. Decreased interpedicular distance in the lumbar spine
. Cervical kyphosis
. Anterior central vertebral beaking
. Coronal clefts in the vertebral bodies
. Normal spinal alignment

Correct Answer & Explanation

. Cervical kyphosis

Explanation

Correct Answer: Cervical kyphosisThe clinical presentation (short limbs, clubfeet, hitchhiker thumbs, cauliflower ears) is pathognomonic for diastrophic dysplasia (SLC26A2 mutation). In the neonatal period and infancy, cervical kyphosis is a classic spinal finding in these patients. Interestingly, unlike cervical kyphosis in many other syndromes, it often resolves spontaneously. Decreased interpedicular distance is seen in achondroplasia, anterior beaking in Morquio syndrome, and coronal clefts in Kniest dysplasia or chondrodysplasia punctata.

Question 7269

Topic: 6. Spine

A 45-year-old male with achondroplasia presents with a 1-year history of progressive neurogenic claudication and bilateral lower extremity weakness. Which of the following anatomic abnormalities is the primary underlying cause of his spinal stenosis?

. Hypertrophy of the ligamentum flavum and facet joints
. Decreased interpedicular distance and shortened pedicles
. High-grade degenerative spondylolisthesis at L4-L5
. Ossification of the posterior longitudinal ligament (OPLL)

Correct Answer & Explanation

. Decreased interpedicular distance and shortened pedicles

Explanation

Correct Answer: Decreased interpedicular distance and shortened pediclesAchondroplasia is a defect in endochondral ossification caused by a mutation in the FGFR3 gene. The spine is severely affected, characterized by shortened pedicles and a progressive decrease in the interpedicular distance from the upper lumbar spine to the lower lumbar spine (the opposite of normal anatomy). This congenital narrowing predisposes patients to severe spinal stenosis in adulthood, which is often exacerbated by mild disc bulging or ligamentous hypertrophy.

Question 7270

Topic: 6. Spine

A 6-year-old boy with Morquio syndrome (mucopolysaccharidosis type IV) is being evaluated prior to general anesthesia for an umbilical hernia repair. Which of the following spinal abnormalities is most critical to rule out before proceeding with intubation?

. Progressive thoracolumbar kyphosis
. Atlantoaxial instability due to odontoid hypoplasia
. Cervical stenosis secondary to pedicle shortening
. Basilar invagination

Correct Answer & Explanation

. Atlantoaxial instability due to odontoid hypoplasia

Explanation

Correct Answer: Atlantoaxial instability due to odontoid hypoplasiaMorquio syndrome (MPS IV) is characterized by a deficiency in galactosamine-6-sulfatase. A hallmark of this condition is severe odontoid hypoplasia and ligamentous laxity, leading to atlantoaxial instability. This can result in life-threatening spinal cord compression, especially during neck extension for endotracheal intubation. Flexion-extension cervical spine radiographs are mandatory prior to any surgical procedure requiring anesthesia in these patients.

Question 7271

Topic: 6. Spine

A 3-year-old child with diastrophic dysplasia presents for routine orthopedic follow-up. Radiographs of the cervical spine reveal a kyphotic deformity. Which of the following is a characteristic feature of cervical kyphosis in this condition?

. It is universally rigid and requires immediate surgical stabilization
. It frequently resolves spontaneously during growth if it is flexible
. It is primarily caused by severe odontoid hypoplasia
. It is typically associated with anterior vertebral body fusion

Correct Answer & Explanation

. It frequently resolves spontaneously during growth if it is flexible

Explanation

Correct Answer: It frequently resolves spontaneously during growth if it is flexibleCervical kyphosis is a well-known complication of diastrophic dysplasia. It typically presents in two forms: a flexible form that often resolves spontaneously as the child grows, and a rigid form that can be progressive and potentially fatal due to spinal cord compression. Observation is appropriate for the flexible type, while the rigid, progressive type requires surgical intervention. Spina bifida occulta of the cervical spine is also a common associated finding.

Question 7272

Topic: 6. Spine

A 5-year-old child with a known mutation in the COL2A1 gene presents with short-trunk dwarfism, coxa vara, and a waddling gait. Radiographs of the spine are most likely to demonstrate which of the following?

. Decreased interpedicular distance in the lumbar spine
. Odontoid hypoplasia and atlantoaxial instability
. Bullet-shaped vertebrae at the thoracolumbar junction
. Severe rigid thoracic lordosis

Correct Answer & Explanation

. Odontoid hypoplasia and atlantoaxial instability

Explanation

Correct Answer: Odontoid hypoplasia and atlantoaxial instabilityThe clinical presentation and COL2A1 mutation are characteristic of Spondyloepiphyseal Dysplasia Congenita (SEDC). SEDC is a type II collagenopathy. Spinal manifestations prominently include delayed ossification of the odontoid process (odontoid hypoplasia) and subsequent atlantoaxial instability. Decreased interpedicular distance is seen in achondroplasia, and bullet-shaped vertebrae are typical of mucopolysaccharidoses.

Question 7273

Topic: Thoracolumbar Spine & Deformity

A 4-year-old girl presents with coarse facial features, corneal clouding, and a thoracolumbar kyphosis. Radiographs reveal anteroinferior beaking of the lumbar vertebrae. Which of the following enzyme deficiencies is most likely responsible for her condition?

. Galactosamine-6-sulfatase
. Alpha-L-iduronidase
. Arylsulfatase B
. Iduronate-2-sulfatase

Correct Answer & Explanation

. Alpha-L-iduronidase

Explanation

Correct Answer: Alpha-L-iduronidaseThe clinical picture of coarse facial features, corneal clouding, and anteroinferior vertebral beaking is classic for Hurler syndrome (Mucopolysaccharidosis type I). Hurler syndrome is caused by a deficiency in alpha-L-iduronidase. In contrast, Morquio syndrome (MPS IV) is caused by a deficiency in galactosamine-6-sulfatase and typically presents with central anterior vertebral beaking. Hunter syndrome (MPS II) is caused by iduronate-2-sulfatase deficiency and lacks corneal clouding.

Question 7274

Topic: 6. Spine

A 7-year-old boy with pseudoachondroplasia (COMP gene mutation) is evaluated for spinal deformities. Which of the following statements regarding spinal involvement in this condition is most accurate?

. Severe spinal stenosis is a hallmark of the disease in adulthood
. Odontoid hypoplasia with atlantoaxial instability is the most common cervical anomaly
. Vertebral abnormalities such as anterior beaking are often present in childhood but tend to resolve by adulthood
. Progressive rigid scoliosis requiring surgical fusion occurs in over 80% of patients

Correct Answer & Explanation

. Vertebral abnormalities such as anterior beaking are often present in childhood but tend to resolve by adulthood

Explanation

Correct Answer: Vertebral abnormalities such as anterior beaking are often present in childhood but tend to resolve by adulthoodPseudoachondroplasia is caused by mutations in the Cartilage Oligomeric Matrix Protein (COMP) gene. Unlike true achondroplasia, patients have normal facial features and normal intelligence. While spinal abnormalities such as platyspondyly and anterior vertebral beaking are common in childhood, they typically resolve or significantly improve by adulthood. Severe spinal stenosis and atlantoaxial instability are not characteristic features of pseudoachondroplasia.

Question 7275

Topic: 6. Spine

A 2-year-old child with achondroplasia presents with a history of central sleep apnea, snoring, and delayed motor milestones. Physical examination reveals hyperreflexia in the lower extremities. What is the most likely anatomic cause of these findings?

. Atlantoaxial rotatory subluxation
. Foramen magnum stenosis
. Thoracolumbar kyphosis
. Lumbar spinal stenosis

Correct Answer & Explanation

. Foramen magnum stenosis

Explanation

Correct Answer: Foramen magnum stenosisForamen magnum stenosis is a critical and potentially life-threatening complication in infants and young children with achondroplasia. It occurs due to abnormal endochondral ossification of the skull base. Compression of the cervicomedullary junction can lead to central sleep apnea, hyperreflexia, hypotonia, delayed motor milestones, and even sudden death. Urgent neurosurgical evaluation for cervicomedullary decompression is indicated.

Question 7276

Topic: 6. Spine

A 12-year-old patient with absent clavicles, delayed closure of cranial sutures, and supernumerary teeth undergoes spinal imaging. Which of the following spinal anomalies is most frequently associated with this patient's genetic condition?

. Spina bifida occulta and delayed vertebral ossification
. Severe congenital scoliosis due to hemivertebrae
. Atlantoaxial instability secondary to os odontoideum
. Progressive thoracolumbar kyphosis with apical vertebral wedging

Correct Answer & Explanation

. Spina bifida occulta and delayed vertebral ossification

Explanation

Correct Answer: Spina bifida occulta and delayed vertebral ossificationThe patient's clinical presentation is classic for cleidocranial dysplasia, an autosomal dominant condition caused by a mutation in the RUNX2 (CBFA1) gene. It affects intramembranous ossification. Spinal manifestations commonly include delayed ossification of the vertebral bodies and neural arches, frequently resulting in spina bifida occulta, particularly in the cervical and upper thoracic spine. Syringomyelia may also occasionally be seen.

Question 7277

Topic: 6. Spine

A 45-year-old male with achondroplasia presents with progressive neurogenic claudication and bilateral lower extremity weakness. Which of the following anatomic abnormalities is the primary pathophysiologic cause of his spinal stenosis?

. Hypertrophy of the ligamentum flavum and facet arthropathy
. Decreased interpedicular distance and shortened pedicles
. Severe degenerative spondylolisthesis at multiple levels
. Ossification of the posterior longitudinal ligament

Correct Answer & Explanation

. Decreased interpedicular distance and shortened pedicles

Explanation

Correct Answer: Decreased interpedicular distance and shortened pediclesAchondroplasia is a defect in endochondral ossification caused by a mutation in the FGFR3 gene. In the spine, this manifests as prematurely fused neurocentral synchondroses, leading to shortened pedicles and a decreased interpedicular distance (which normally widens from L1 to L5 but narrows in achondroplasia). This creates a congenitally narrow, trefoil-shaped spinal canal. While degenerative changes like ligamentum flavum hypertrophy can exacerbate the condition later in life, the primary underlying cause of the severe stenosis is the congenital bony anatomy.

Question 7278

Topic: 6. Spine

A 6-year-old child with a known diagnosis of spondyloepiphyseal dysplasia congenita (SEDC) is being evaluated prior to general anesthesia for an elective hernia repair. Which of the following radiographic evaluations is most critical for this patient before intubation?

. Standing full-length scoliosis radiographs
. Flexion-extension radiographs of the cervical spine
. Magnetic resonance imaging of the lumbar spine
. Computed tomography scan of the thoracic spine

Correct Answer & Explanation

. Flexion-extension radiographs of the cervical spine

Explanation

Correct Answer: Flexion-extension radiographs of the cervical spineSpondyloepiphyseal dysplasia congenita (SEDC) is a type II collagenopathy. Patients with SEDC frequently have odontoid hypoplasia or os odontoideum, which leads to atlantoaxial instability (AAI). Because general anesthesia and intubation require neck manipulation, it is critical to rule out AAI preoperatively using flexion-extension cervical spine radiographs to prevent catastrophic neurologic injury. If instability is present, fiberoptic intubation and careful positioning are required, and surgical stabilization may be indicated.

Question 7279

Topic: 6. Spine

Which of the following skeletal dysplasias is characterized by a defect in the sulfate transporter (SLC26A2 gene) and frequently presents with severe cervical kyphosis that may spontaneously resolve during early childhood?

. Achondroplasia
. Spondyloepiphyseal dysplasia congenita
. Diastrophic dysplasia
. Pseudoachondroplasia

Correct Answer & Explanation

. Diastrophic dysplasia

Explanation

Correct Answer: Diastrophic dysplasiaDiastrophic dysplasia is an autosomal recessive condition caused by a mutation in the SLC26A2 gene, which encodes a sulfate transporter. Clinical features include 'hitchhiker' thumbs, cauliflower ears, cleft palate, and severe clubfeet. In the spine, cervical kyphosis is common and can be severe. Uniquely, the cervical kyphosis in diastrophic dysplasia often resolves spontaneously as the child grows, provided there is no apical vertebral hypoplasia or neurologic deficit. Observation is the initial treatment of choice unless progression or myelopathy occurs.

Question 7280

Topic: 6. Spine

A 7-year-old boy with Morquio syndrome (Mucopolysaccharidosis type IV) presents with decreasing walking endurance, clumsiness, and hyperreflexia in his lower extremities. What is the most likely underlying spinal pathology responsible for these findings?

. Thoracolumbar kyphosis secondary to anterior vertebral body wedging
. Atlantoaxial instability due to odontoid hypoplasia and ligamentous laxity
. Lumbar spinal stenosis due to congenitally shortened pedicles
. High-grade isthmic spondylolisthesis at L5-S1

Correct Answer & Explanation

. Atlantoaxial instability due to odontoid hypoplasia and ligamentous laxity

Explanation

Correct Answer: Atlantoaxial instability due to odontoid hypoplasia and ligamentous laxityMorquio syndrome (MPS IV) is caused by a deficiency in N-acetylgalactosamine-6-sulfatase (Type A) or beta-galactosidase (Type B). It is characterized by severe ligamentous laxity and odontoid hypoplasia. This combination frequently leads to life-threatening atlantoaxial instability (AAI) and subsequent cervical myelopathy, presenting as decreased endurance, clumsiness, and upper motor neuron signs (hyperreflexia). Prophylactic posterior cervical fusion is often required to prevent irreversible neurologic damage.

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