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6. Spine MCQs

Practice Set 358 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 7141

Topic: Cervical Spine

A 5-year-old child presents with short-trunk dwarfism, significant genu valgum, and normal intelligence. Radiographs reveal platyspondyly and hypoplasia of the odontoid process. Urine testing shows elevated keratan sulfate. Which enzyme is most likely deficient?

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

Correct Answer & Explanation

. Galactosamine-6-sulfatase

Explanation

Morquio syndrome (Mucopolysaccharidosis Type IV) is caused by a deficiency in galactosamine-6-sulfatase (Type IVA) or beta-galactosidase (Type IVB). Odontoid hypoplasia is a critical finding that necessitates early cervical spine evaluation for instability.

Question 7142

Topic: Cervical Spine

A 6-year-old boy presents with a disproportionately short trunk, severe coxa vara, and an abnormal waddling gait. Cervical spine radiographs reveal odontoid hypoplasia. Genetic testing would most likely reveal a mutation affecting which of the following?

. Type I collagen
. Type II collagen
. Cartilage Oligomeric Matrix Protein
. Fibroblast Growth Factor Receptor 3
. Sulfate transporter

Correct Answer & Explanation

. Type II collagen

Explanation

Spondyloepiphyseal dysplasia congenita (SEDC) is caused by mutations in the COL2A1 gene, which encodes type II collagen. Affected patients frequently suffer from atlantoaxial instability secondary to odontoid hypoplasia.

Question 7143

Topic: 6. Spine

A 14-year-old boy with Osteogenesis Imperfecta Type IV presents with new-onset hyperreflexia, lower extremity weakness, and sleep apnea.

What is the most critical and life-threatening complication responsible for these symptoms?

. Atlantoaxial rotatory subluxation
. Basilar invagination
. Syringomyelia
. Cervical spine osteomyelitis
. Severe thoracic kyphoscoliosis compressing the spinal cord

Correct Answer & Explanation

. Basilar invagination

Explanation

Basilar invagination is a recognized and potentially fatal complication in severe forms of OI due to softening of the skull base. It leads to brainstem and upper cervical cord compression, presenting with myelopathy and sleep apnea.

Question 7144

Topic: Cervical Spine

A 7-year-old girl with short stature, corneal clouding, and normal intelligence presents for evaluation. Radiographs show severe platyspondyly and hypoplasia of the odontoid. She is found to be deficient in which of the following enzymes?

. Alpha-L-iduronidase
. Iduronate sulfatase
. Galactose-6-sulfatase
. Arylsulfatase B
. Cathepsin K

Correct Answer & Explanation

. Galactose-6-sulfatase

Explanation

Morquio syndrome (MPS IV) is caused by a deficiency in galactose-6-sulfatase (Type A). Unlike Hurler or Hunter syndromes, patients with Morquio syndrome typically maintain normal intelligence but suffer from severe skeletal issues like cervical instability.

Question 7145

Topic: 6. Spine

A 9-year-old boy presents with hip pain and a waddling gait. Radiographs show small, fragmented, and irregular epiphyses of the proximal femora, but his spine radiographs are entirely normal. He is found to have a mutation in the MATN3 gene. Which of the following clinical findings is classic for this condition?

. Blue sclerae
. Double-layered patella
. Cauliflower ears
. Frontal bossing
. Cleft palate

Correct Answer & Explanation

. Double-layered patella

Explanation

Multiple Epiphyseal Dysplasia (MED) can be caused by mutations in COMP, MATN3, or Type IX collagen genes. A double-layered (or multipartite) patella is a hallmark radiographic and clinical feature of this dysplasia.

Question 7146

Topic: 6. Spine

A 45-year-old patient with end-stage renal disease presents with diffuse bone pain. Radiographs demonstrate osteopenia and alternating sclerotic and lucent bands in the vertebral bodies ("rugger-jersey" spine). Which of the following sets of laboratory values is most typical for this condition?

. Low PTH, high calcium, low phosphorus
. High PTH, low calcium, high phosphorus
. Low PTH, low calcium, low phosphorus
. High PTH, high calcium, low phosphorus
. Normal PTH, normal calcium, normal phosphorus

Correct Answer & Explanation

. High PTH, low calcium, high phosphorus

Explanation

Renal osteodystrophy is driven by secondary hyperparathyroidism. Failing kidneys cannot excrete phosphorus or produce 1,25-dihydroxyvitamin D properly, resulting in hyperphosphatemia, hypocalcemia, and consequently, highly elevated PTH levels.

Question 7147

Topic: 6. Spine

A 45-year-old patient with end-stage renal disease complains of generalized bone pain. Laboratory results reveal elevated serum phosphorus, decreased serum calcium, and markedly elevated parathyroid hormone. Which of the following radiographic findings is most characteristic of this condition in the spine?

. Picture frame vertebral bodies
. Rugger jersey spine
. Bone-within-a-bone appearance
. Bamboo spine
. Platyspondyly with anterior beaking

Correct Answer & Explanation

. Rugger jersey spine

Explanation

Renal osteodystrophy typically produces a 'rugger jersey' spine due to sclerotic bands at the superior and inferior endplates of the vertebral bodies. This is a manifestation of secondary hyperparathyroidism.

Question 7148

Topic: 6. Spine

An 8-month-old infant with achondroplasia presents with witnessed episodes of apnea, cyanosis, and hyperreflexia. What is the most appropriate next step in evaluation?

. Cervical spine flexion/extension radiographs
. MRI of the cervicomedullary junction
. Polysomnography alone
. Lumbar spine MRI
. Electroencephalogram

Correct Answer & Explanation

. MRI of the cervicomedullary junction

Explanation

Infants with achondroplasia are at high risk for foramen magnum stenosis, which can cause cervicomedullary compression leading to central apnea, hyperreflexia, and sudden death. MRI of the cervicomedullary junction is diagnostic.

Question 7149

Topic: 6. Spine

A 6-year-old girl with normal intelligence presents with short stature, corneal clouding, and knock knees. Urine analysis reveals excessive excretion of keratan sulfate. She is at highest risk for which of the following orthopedic emergencies?

. Femoral neck fracture
. Atlantoaxial subluxation with spinal cord compression
. Acute slipped capital femoral epiphysis
. Pathologic fracture of the humerus
. Cauda equina syndrome from lumbar stenosis

Correct Answer & Explanation

. Atlantoaxial subluxation with spinal cord compression

Explanation

This patient has Morquio syndrome (MPS type IV), marked by keratan sulfate in the urine and normal intelligence. Odontoid hypoplasia is a hallmark, putting patients at extreme risk for atlantoaxial subluxation and myelopathy.

Question 7150

Topic: 6. Spine

A 4-month-old infant with achondroplasia is brought to the clinic by her parents due to observed episodes of breath-holding and central apnea during sleep. On examination, the infant exhibits hyperreflexia in both lower extremities. What is the most appropriate next step in management?

. Obtain an urgent cervical spine MRI
. Initiate growth hormone therapy
. Refer for multi-level limb lengthening
. Reassure the parents and order an overnight polysomnogram alone
. Schedule a lumbar laminectomy

Correct Answer & Explanation

. Obtain an urgent cervical spine MRI

Explanation

Infants with achondroplasia are at high risk for foramen magnum stenosis, which can cause severe cervicomedullary compression. Symptoms such as central apnea, hyperreflexia, or quadriparesis warrant an urgent cervical spine MRI to evaluate the need for surgical decompression.

Question 7151

Topic: 6. Spine

A 6-year-old child presents for an orthopaedic evaluation. He has short-trunk dwarfism, a cleft palate, and severe myopia. Radiographs reveal coxa vara and flattened vertebral bodies. Prior to the patient undergoing general anesthesia for an unrelated procedure, which of the following imaging studies is mandatory?

. AP and lateral pelvis radiographs
. Flexion-extension cervical spine radiographs
. Lumbar spine MRI
. High-resolution chest CT
. Transthoracic echocardiogram

Correct Answer & Explanation

. Flexion-extension cervical spine radiographs

Explanation

The patient's clinical presentation is classic for Spondyloepiphyseal Dysplasia (SED) congenita (COL2A1 mutation). These patients frequently have odontoid hypoplasia and atlantoaxial instability, making flexion-extension cervical spine radiographs mandatory prior to general anesthesia to prevent catastrophic neurological injury during intubation.

Question 7152

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 underlying cause of his spinal stenosis?

. Hypertrophy of the ligamentum flavum
. Decreased interpedicular distance
. Degenerative spondylolisthesis at L4-L5
. Enlarged and overriding facet joints
. Tethered spinal cord

Correct Answer & Explanation

. Decreased interpedicular distance

Explanation

Correct Answer: Decreased interpedicular distanceAchondroplasia is the most common rhizomelic dwarfism, caused by a mutation in the FGFR3 gene. The primary cause of lumbar spinal stenosis in these patients is a congenital narrowing of the spinal canal due to short, thickened pedicles and a progressively decreased interpedicular distance from the upper to the lower lumbar spine (the opposite of normal anatomy). While disc herniations or ligamentum flavum hypertrophy can exacerbate the stenosis later in life, the fundamental anatomic defect is the decreased interpedicular distance.

Question 7153

Topic: 6. Spine

A 6-year-old child with a known mutation in the COL2A1 gene presents with a waddling gait, barrel chest, and disproportionate short-trunk dwarfism. Radiographs reveal delayed ossification of the pubic bones and coxa vara. Which of the following spinal pathologies is most critical to screen for in this patient prior to any surgical intervention requiring general anesthesia?

. Thoracolumbar kyphosis
. Lumbar spinal stenosis
. Atlantoaxial instability
. Basilar invagination
. Tethered cord syndrome

Correct Answer & Explanation

. Atlantoaxial instability

Explanation

Correct Answer: Atlantoaxial instabilityThe clinical presentation and COL2A1 mutation are classic for Spondyloepiphyseal Dysplasia Congenita (SEDC). Patients with SEDC frequently have odontoid hypoplasia, which leads to atlantoaxial instability. It is critical to screen these patients with flexion-extension cervical spine radiographs prior to any surgery requiring intubation to prevent catastrophic spinal cord injury during neck manipulation.

Question 7154

Topic: 6. Spine

A 7-year-old boy presents with short-trunk dwarfism, corneal clouding, and normal intelligence. Lateral spine radiographs demonstrate platyspondyly with central anterior beaking of the vertebral bodies. Deficiency of which of the following enzymes is most likely responsible for this condition?

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

Correct Answer & Explanation

. Galactosamine-6-sulfatase

Explanation

Correct Answer: Galactosamine-6-sulfataseThe patient's presentation of short-trunk dwarfism, normal intelligence, corneal clouding, and central anterior beaking of the vertebrae is characteristic of Morquio syndrome (Mucopolysaccharidosis Type IV). MPS IV Type A is caused by a deficiency in N-acetylgalactosamine-6-sulfatase. Hurler syndrome (MPS I) presents with intellectual disability and anteroinferior beaking (deficiency of Alpha-L-iduronidase).

Question 7155

Topic: 6. Spine

An infant is diagnosed with diastrophic dysplasia. The parents are counseled regarding the skeletal manifestations, including a 'hitchhiker' thumb and cauliflower ears. Evaluation of the cervical spine reveals a localized cervical kyphosis. What is the most appropriate initial management for this cervical deformity?

. Immediate posterior cervical fusion
. Halo-gravity traction followed by anterior-posterior fusion
. Observation, as the majority resolve spontaneously
. Cervical bracing with a Minerva cast
. Suboccipital decompression

Correct Answer & Explanation

. Observation, as the majority resolve spontaneously

Explanation

Correct Answer: Observation, as the majority resolve spontaneouslyCervical kyphosis is a well-known complication of diastrophic dysplasia, often associated with spina bifida occulta of the cervical vertebrae. Unlike many other conditions where cervical kyphosis is relentlessly progressive, the cervical kyphosis in diastrophic dysplasia often resolves spontaneously with growth. Therefore, observation is the initial management of choice. Surgery is reserved for severe, progressive cases or those with neurologic compromise.

Question 7156

Topic: 6. Spine

A 4-year-old girl presents with coarse facial features, hepatosplenomegaly, and developmental delay. Lateral radiographs of the thoracolumbar spine reveal vertebral bodies with a distinct beaking pattern. Which of the following radiographic findings is most characteristic of her likely diagnosis compared to Morquio syndrome?

. Central anterior beaking of the vertebral bodies
. Anteroinferior beaking of the vertebral bodies
. Coronal clefts in the vertebral bodies
. Picture-frame appearance of the vertebrae
. Rugger-jersey spine

Correct Answer & Explanation

. Anteroinferior beaking of the vertebral bodies

Explanation

Correct Answer: Anteroinferior beaking of the vertebral bodiesThe clinical picture of coarse facial features, hepatosplenomegaly, and developmental delay points to Hurler syndrome (Mucopolysaccharidosis Type I). A classic radiographic distinguishing feature between Hurler and Morquio syndromes is the location of the vertebral body beaking. Hurler syndrome typically features anteroinferior beaking, whereas Morquio syndrome features central anterior beaking.

Question 7157

Topic: 6. Spine
A 15-year-old patient with Osteogenesis Imperfecta Type III presents with new-onset lower extremity hyperreflexia, a positive Babinski sign, and severe occipital headaches. Which of the following is the most likely cause of these symptoms?
. Atlantoaxial rotatory subluxation
. Basilar invagination
. Syringomyelia
. Lumbar spondylolisthesis
. Thoracic disc herniation

Correct Answer & Explanation

. Basilar invagination

Explanation

Patients with severe forms of Osteogenesis Imperfecta (such as Type III) have profound bone fragility and softening. The skull base can soften, leading to basilar invagination (upward migration of the odontoid process into the foramen magnum). This causes direct brainstem and upper cervical cord compression, presenting with upper motor neuron signs (hyperreflexia, Babinski), lower cranial nerve palsies, and occipital headaches.

Question 7158

Topic: 6. Spine

A 5-year-old child presents with short-limb dwarfism, a waddling gait, and normal facial features. Genetic testing reveals a mutation in the Cartilage Oligomeric Matrix Protein (COMP) gene. Which of the following spinal abnormalities is a significant risk in this patient and requires radiographic screening?

. Severe lumbar spinal stenosis due to short pedicles
. Foramen magnum stenosis
. Atlantoaxial instability due to odontoid hypoplasia
. Basilar invagination
. Congenital absence of the sacrum

Correct Answer & Explanation

. Atlantoaxial instability due to odontoid hypoplasia

Explanation

Correct Answer: Atlantoaxial instability due to odontoid hypoplasiaThe patient has pseudoachondroplasia, characterized by a COMP gene mutation, short-limb dwarfism, and notably normal facial features (unlike achondroplasia). A critical spinal manifestation of pseudoachondroplasia is odontoid hypoplasia, which places the patient at high risk for atlantoaxial instability. Cervical spine screening with flexion-extension radiographs is essential. They do not typically suffer from the severe lumbar spinal stenosis or foramen magnum stenosis seen in true achondroplasia.

Question 7159

Topic: 6. Spine

A 45-year-old male with achondroplasia presents with progressive neurogenic claudication and bilateral lower extremity weakness. Which of the following anatomical abnormalities is the primary underlying cause of lumbar spinal stenosis in this patient population?

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

Correct Answer & Explanation

. Decreased interpedicular distance and shortened pedicles

Explanation

Correct Answer: Decreased interpedicular distance and shortened pediclesIn achondroplasia, a mutation in the FGFR3 gene leads to abnormal endochondral ossification. In the spine, this manifests as premature fusion of the neurocentral synchondroses, resulting in shortened pedicles and a decreased interpedicular distance (which normally widens from L1 to L5 but narrows in achondroplasia). This constitutes a severe congenital spinal stenosis, making these patients highly susceptible to symptomatic compression later in life, even with mild degenerative changes.

Question 7160

Topic: 6. Spine

A 7-year-old child with Morquio syndrome (Mucopolysaccharidosis Type IV) is scheduled for bilateral lower extremity osteotomies. Preoperative cervical spine radiographs reveal severe odontoid hypoplasia. What is the most critical perioperative consideration for this patient?

. High risk of malignant hyperthermia requiring non-triggering anesthetics
. Need for prophylactic halo vest placement prior to any surgical intervention
. High risk of spinal cord injury during intubation due to atlantoaxial instability
. Requirement for intraoperative somatosensory evoked potentials (SSEPs) only
. Risk of massive hemorrhage due to inherent platelet dysfunction

Correct Answer & Explanation

. High risk of spinal cord injury during intubation due to atlantoaxial instability

Explanation

Correct Answer: High risk of spinal cord injury during intubation due to atlantoaxial instabilityPatients with Morquio syndrome (MPS IV) frequently have odontoid hypoplasia and ligamentous laxity, leading to severe atlantoaxial instability. Neck extension during endotracheal intubation can cause fatal spinal cord compression. Careful preoperative assessment (flexion-extension radiographs, MRI) and specialized intubation techniques (e.g., awake fiberoptic intubation with the neck in a neutral position) are mandatory.

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