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6. Spine MCQs

Practice Set 273 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 5441

Topic: 6. Spine

A 6-year-old boy with Morquio syndrome (Mucopolysaccharidosis Type IV) is scheduled for lower extremity deformity correction surgery. What critical pre-operative assessment must be performed prior to intubation?

. Echocardiogram to rule out cor pulmonale
. Cervical spine flexion-extension radiographs
. Pulmonary function tests
. Renal ultrasound
. DEXA scan

Correct Answer & Explanation

. Cervical spine flexion-extension radiographs

Explanation

Patients with Morquio syndrome frequently have odontoid hypoplasia and ligamentous laxity, leading to severe atlantoaxial instability. Cervical spine flexion-extension radiographs or an MRI are critical pre-operatively to prevent catastrophic spinal cord injury during positioning and intubation.

Question 5442

Topic: 6. Spine
A 10-year-old girl with severe Osteogenesis Imperfecta (Sillence Type III) develops progressive hyperreflexia, sleep apnea, and difficulty swallowing. Which of the following complications is most likely responsible for her new symptoms?
. Syringomyelia
. Basilar invagination
. Atlantoaxial rotatory subluxation
. Cervical kyphosis
. Spinal epidural hematoma

Correct Answer & Explanation

. Basilar invagination

Explanation

Basilar invagination is a severe, potentially lethal complication in patients with OI Types III and IV due to softening of the skull base. It leads to upward migration of the odontoid into the foramen magnum, causing brainstem compression, cranial nerve palsies, and hyperreflexia.

Question 5443

Topic: 6. Spine

A 2-year-old boy with a known FGFR3 mutation presents with newly developed central sleep apnea, hyperreflexia, and clonus in the lower extremities. What is the most crucial next step in management?

. Cervical spine flexion/extension radiographs
. MRI of the craniovertebral junction
. Observation with continuous CPAP at night
. Immediate application of a halo vest
. Genetic testing for a secondary mutation

Correct Answer & Explanation

. MRI of the craniovertebral junction

Explanation

Achondroplasia (FGFR3 mutation) can cause foramen magnum stenosis, leading to cervicomedullary compression manifesting as central sleep apnea and myelopathy. An MRI of the craniovertebral junction is urgently required to assess the degree of stenosis, which may necessitate suboccipital decompression.

Question 5444

Topic: 6. Spine

A 7-year-old child with short trunk dwarfism, corneal clouding, and normal intelligence is found to have a deficiency in N-acetylgalactosamine-6-sulfatase. Which orthopedic complication is most life-threatening in this patient?

. Thoracolumbar kyphosis
. Atlantoaxial instability
. Severe genu valgum
. Bilateral hip dislocation
. Coxa vara

Correct Answer & Explanation

. Atlantoaxial instability

Explanation

Morquio syndrome (MPS type IV) is an autosomal recessive lysosomal storage disease caused by GALNS deficiency. Odontoid hypoplasia is a classic hallmark, leading to severe atlantoaxial instability and the potential for life-threatening cervical myelopathy.

Question 5445

Topic: 6. Spine

A 7-year-old boy with a known history of Morquio syndrome (Mucopolysaccharidosis Type IV) presents for routine evaluation. His parents report he has had progressive lower extremity weakness, clumsy gait, and decreased endurance. What is the most likely structural cause of his neurologic decline?

. Progressive thoracolumbar kyphosis
. Odontoid hypoplasia leading to atlantoaxial instability
. Tethered spinal cord
. Syrinx formation in the cervical spine
. Premature closure of the cranial sutures

Correct Answer & Explanation

. Odontoid hypoplasia leading to atlantoaxial instability

Explanation

Morquio syndrome (MPS IV) is highly associated with odontoid hypoplasia and ligamentous laxity, which leads to atlantoaxial instability. This can cause progressive cervical myelopathy and requires close radiographic monitoring and potential prophylactic fusion.

Question 5446

Topic: 6. Spine

A 6-year-old child with Morquio syndrome (Mucopolysaccharidosis Type IV) presents with progressive bilateral hand weakness, hyperreflexia in the lower extremities, and an unsteady gait. Which of the following structural abnormalities is the most likely cause of these neurologic findings?

. Odontoid hypoplasia with atlantoaxial instability
. Progressive thoracolumbar kyphosis
. Tethered cord syndrome
. Foramen magnum stenosis
. Subaxial cervical spine stenosis

Correct Answer & Explanation

. Odontoid hypoplasia with atlantoaxial instability

Explanation

Morquio syndrome is characterized by severe skeletal dysplasia with normal intelligence. Odontoid hypoplasia leading to atlantoaxial instability is a hallmark of the disease and a primary cause of cervical myelopathy, requiring early screening and possible fusion.

Question 5447

Topic: 6. Spine

An 18-month-old irritable infant, exclusively fed boiled cow's milk since birth, presents with gingival bleeding, lower extremity pseudoparalysis, and a prominent "white line of Frankel" on radiographs. The deficient nutrient is an essential cofactor for which of the following biochemical processes?

. Gamma-carboxylation of glutamic acid residues
. Hydroxylation of proline and lysine residues in collagen
. Cross-linking of elastin via lysyl oxidase
. Cleavage of procollagen C-terminal and N-terminal propeptides
. Conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D

Correct Answer & Explanation

. Hydroxylation of proline and lysine residues in collagen

Explanation

Scurvy is caused by Vitamin C deficiency. Vitamin C is a critical cofactor for prolyl and lysyl hydroxylases; without it, collagen cannot form stable triple helices, leading to fragile capillaries (bleeding) and metaphyseal bone lesions.

Question 5448

Topic: 6. Spine

A 10-year-old girl with a known history of neurofibromatosis type 1 develops a rapidly progressive spinal deformity. Radiographs demonstrate a short-segment, sharp angular curve with vertebral scalloping and severe rib penciling.

What is the most appropriate definitive management for this deformity?

. Observation until the curve reaches 50 degrees
. Rigid bracing with a TLSO until skeletal maturity
. Anterior and posterior spinal fusion
. Posterior spinal fusion alone
. Growing rod construct implantation

Correct Answer & Explanation

. Anterior and posterior spinal fusion

Explanation

Dystrophic scoliosis in NF1 is characterized by a short, sharp curve, rib penciling, and severe progression. Due to the exceptionally high risk of curve progression and pseudarthrosis, a combined anterior and posterior spinal fusion is typically required.

Question 5449

Topic: Thoracolumbar Spine & Deformity

A 10-year-old girl with known Neurofibromatosis type 1 presents with a sharp, angular, short-segment thoracic scoliosis.

Which of the following features is highly indicative of a dystrophic curve that carries a high risk of rapid progression?

. Penciling of the ribs
. Apical vertebral wedging of 5 degrees
. Pedicle hypertrophy
. Cobb angle less than 20 degrees
. Right-sided curve apex

Correct Answer & Explanation

. Penciling of the ribs

Explanation

Dystrophic scoliosis in NF1 is characterized by penciling of the ribs, severe apical vertebral wedging, dural ectasia, and enlarged neural foramina. These specific curves progress rapidly and typically require early surgical stabilization.

Question 5450

Topic: 6. Spine

A 14-year-old boy with confirmed Neurofibromatosis Type 1 presents with severe neck pain and torticollis.

What is the most critical cervical spine pathology to screen for in this patient population?

. Cervical kyphosis with dural ectasia
. Atlantoaxial rotatory subluxation
. Ossification of the posterior longitudinal ligament (OPLL)
. Congenital fusion of cervical vertebrae (Klippel-Feil)
. Odontoid hypoplasia

Correct Answer & Explanation

. Cervical kyphosis with dural ectasia

Explanation

Patients with NF1 are prone to severe, progressive cervical kyphosis, which is often associated with dural ectasia and severe vertebral body wedging. This can lead to rapid neurologic deterioration and requires careful screening and potential early surgical stabilization.

Question 5451

Topic: 6. Spine

A 12-year-old girl with known Neurofibromatosis type 1 presents with a rapidly progressive spinal deformity.

Radiographs show a short-segmented, sharp angular curve with vertebral scalloping and rib penciling. What is the most appropriate management?

. Observation until skeletal maturity
. Rigid TLSO bracing
. Anterior spinal fusion alone
. Posterior spinal fusion alone
. Combined anterior and posterior spinal fusion

Correct Answer & Explanation

. Combined anterior and posterior spinal fusion

Explanation

Dystrophic scoliosis in NF1 has a high risk of progression and pseudarthrosis. Bracing is ineffective, and robust combined anterior and posterior spinal fusion is often required to achieve stability and prevent curve progression.

Question 5452

Topic: 6. Spine

A 14-year-old girl with a known genetic disorder presents for evaluation of progressive back pain and clinical deformity.

Given her underlying diagnosis of Neurofibromatosis Type 1, what is the most typical characteristic of the dystrophic spinal deformity frequently seen in these patients?

. Long sweeping, C-shaped thoracolumbar curve without vertebral body changes
. Short, sharp angular scoliotic curve with vertebral wedging and scalloping
. Symmetrical anterior wedging of 3 or more consecutive thoracic vertebrae
. Purely lordotic deformity of the cervical spine
. Spondylolisthesis isolated to the L5-S1 junction

Correct Answer & Explanation

. Short, sharp angular scoliotic curve with vertebral wedging and scalloping

Explanation

Dystrophic scoliosis in Neurofibromatosis Type 1 classically presents as a short, sharply angulated curve typically involving 4-6 vertebrae. It is highly associated with structural anomalies such as dural ectasia, severely thinned pedicles, and posterior vertebral body scalloping.

Question 5453

Topic: 6. Spine

A 4-year-old child with Spondyloepiphyseal Dysplasia Congenita (SEDC) is scheduled for a femoral osteotomy. What is the most critical preoperative assessment required for this patient regarding the spine?

. A. Lumbar MRI to assess for spinal stenosis
. B. Lateral flexion-extension cervical radiographs
. C. Standing full-length scoliosis films
. D. CT scan of the thoracolumbar gibbus
. E. Bone mineral density scan

Correct Answer & Explanation

. B. Lateral flexion-extension cervical radiographs

Explanation

Correct Answer: BPatients with SEDC frequently have odontoid hypoplasia and ligamentous laxity, leading to atlantoaxial instability. Preoperative cervical spine clearance with flexion-extension views is mandatory before any surgical procedure requiring intubation to prevent catastrophic spinal cord injury.

Question 5454

Topic: 6. Spine

In patients with Achondroplasia, which of the following radiographic findings is characteristic of the lumbar spine on an AP view?

. A. Increasing interpedicular distance from L1 to L5
. B. Scalloping of the posterior vertebral bodies
. C. Decreasing interpedicular distance from L1 to L5
. D. Presence of hemivertebrae at the thoracolumbar junction
. E. Widening of the neural foramina

Correct Answer & Explanation

. C. Decreasing interpedicular distance from L1 to L5

Explanation

Correct Answer: CA hallmark of Achondroplasia is the narrowing of the interpedicular distance as one moves caudally in the lumbar spine. In a normal spine, this distance increases. This narrowing, combined with short pedicles, contributes to significant spinal stenosis.

Question 5455

Topic: 6. Spine

A 6-year-old boy with Morquio Syndrome (MPS IV) presents with progressive difficulty walking and hyperreflexia. What is the primary biochemical defect responsible for this condition?

. A. Deficiency of Iduronate-2-sulfatase
. B. Deficiency of N-acetylgalactosamine-6-sulfatase (GALNS)
. C. Mutation in the FGFR3 gene
. D. Mutation in the COL2A1 gene
. E. Deficiency of Alpha-L-iduronidase

Correct Answer & Explanation

. B. Deficiency of N-acetylgalactosamine-6-sulfatase (GALNS)

Explanation

Correct Answer: BMorquio Syndrome (MPS IV) is caused by a deficiency in GALNS, leading to the accumulation of keratan sulfate. This results in odontoid hypoplasia and ligamentous laxity, often causing cervical myelopathy.

Question 5456

Topic: 6. Spine

Regarding the surgical management of spinal stenosis in Achondroplasia, which statement is most accurate?

. A. Simple laminotomy is usually sufficient
. B. Decompression should be limited to one level to prevent instability
. C. Extended laminectomy including the pedicles and foraminotomy is often required
. D. Prophylactic decompression is recommended at age 5
. E. Posterior fusion is always contraindicated

Correct Answer & Explanation

. C. Extended laminectomy including the pedicles and foraminotomy is often required

Explanation

Correct Answer: CDue to the global nature of the stenosis (short pedicles, thickened laminae, and narrow canal), wide decompression (laminectomy and often partial facetectomy/pediculectomy) over multiple levels is typically necessary to achieve adequate neural relief.

Question 5457

Topic: 6. Spine

A 5-year-old boy presents with short-trunk dwarfism, a barrel-shaped chest, and severe coxa vara. Radiographs reveal platyspondyly and delayed ossification of the femoral heads. Genetic testing confirms a mutation in the COL2A1 gene. What is the most critical cervical spine abnormality associated with this condition?

. Os odontoideum
. Odontoid hypoplasia with atlantoaxial instability
. C1-C2 fusion (Klippel-Feil)
. Basilar invagination
. Subaxial subluxation

Correct Answer & Explanation

. Odontoid hypoplasia with atlantoaxial instability

Explanation

Correct Answer: BThe patient has Spondyloepiphyseal Dysplasia (SED) congenita, which is caused by a mutation in the COL2A1 gene (Type II collagen). A hallmark of this condition is odontoid hypoplasia, which leads to atlantoaxial instability. This is a critical finding as it poses a significant risk for cervical myelopathy and requires close monitoring or prophylactic stabilization.

Question 5458

Topic: Cervical Spine

In patients with Morquio Syndrome (Mucopolysaccharidosis IV), which specific substance is found in excess in the urine due to a deficiency of N-acetylgalactosamine-6-sulfatase?

. Heparan sulfate
. Dermatan sulfate
. Keratan sulfate
. Chondroitin sulfate
. Hyaluronic acid

Correct Answer & Explanation

. Keratan sulfate

Explanation

Correct Answer: CMorquio Syndrome (MPS IV) is characterized by the accumulation of Keratan sulfate. Unlike other mucopolysaccharidoses, Morquio syndrome is notable for significant skeletal involvement (platyspondyly, odontoid hypoplasia) and ligamentous laxity, but typically presents with normal intelligence.

Question 5459

Topic: 6. Spine

A 12-year-old male with Achondroplasia presents with progressive neurogenic claudication and lower extremity weakness. Which radiographic finding is most characteristic of the lumbar spine in this patient?

. Increasing interpedicular distance from L1 to L5
. Decreasing interpedicular distance from L1 to L5
. Scalloping of the anterior vertebral bodies
. Widening of the spinal canal in the sagittal plane
. Long, thin pedicles

Correct Answer & Explanation

. Decreasing interpedicular distance from L1 to L5

Explanation

Correct Answer: BIn Achondroplasia, the interpedicular distance decreases as one moves caudally (from L1 to L5), which is the opposite of normal anatomy. Combined with short, thick pedicles and thickened laminae, this leads to significant congenital spinal stenosis, often requiring multi-level decompression.

Question 5460

Topic: 6. Spine

A neonate is born with 'cauliflower ears,' a 'hitchhiker thumb,' and severe clubfeet. Radiographs show a progressive cervical kyphosis. Which gene mutation is responsible for this skeletal dysplasia?

. FGFR3
. COL2A1
. COMP
. SLC26A2
. TRPV4

Correct Answer & Explanation

. SLC26A2

Explanation

Correct Answer: DThe clinical triad of cauliflower ears, hitchhiker thumb, and clubfeet is diagnostic of Diastrophic Dysplasia. This condition is caused by a mutation in the SLC26A2 gene, which encodes a sulfate transporter protein. Cervical kyphosis is a common and potentially dangerous spinal manifestation in these patients.

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