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6. Spine MCQs

Practice Set 280 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 5581

Topic: 6. Spine

Which of the following radiographic findings is most characteristic of the spine in a patient with achondroplasia?

. Progressive widening of the interpedicular distance from L1 to L5
. Decreased interpedicular distance from L1 to L5
. Anterior beaking of the lumbar vertebral bodies
. Platyspondyly with central endplate defects

Correct Answer & Explanation

. Decreased interpedicular distance from L1 to L5

Explanation

In achondroplasia, the interpedicular distance classically narrows from L1 to L5, unlike the normal widening seen in unaffected individuals. This anatomic anomaly heavily predisposes these patients to severe lumbar spinal stenosis.

Question 5582

Topic: 6. Spine
A child with a known mucopolysaccharidosis presents with progressive myelopathy. Radiographs reveal severe odontoid hypoplasia and atlantoaxial instability. Biochemical testing shows abnormal accumulation of keratan sulfate. Which syndrome does this patient have?
. Hurler syndrome (MPS I)
. Hunter syndrome (MPS II)
. Sanfilippo syndrome (MPS III)
. Morquio syndrome (MPS IV)

Correct Answer & Explanation

. Morquio syndrome (MPS IV)

Explanation

Morquio syndrome (MPS IV) is characterized by the inability to degrade keratan sulfate. A hallmark and highly dangerous orthopedic manifestation of Morquio syndrome is odontoid hypoplasia, which leads to severe atlantoaxial instability and potential cervical myelopathy.

Question 5583

Topic: 6. Spine

A 35-year-old male with achondroplasia presents with neurogenic claudication. He reports leg pain and numbness after walking 50 meters, which is relieved by sitting. Radiographs of the lumbar spine will most likely demonstrate which of the following anatomic abnormalities?

. Decreased interpedicular distance from L1 to L5
. Increased atlantoaxial instability
. Dysplastic spondylolisthesis at L5-S1
. Platyspondyly with anterior beaking
. Ossification of the posterior longitudinal ligament

Correct Answer & Explanation

. Decreased interpedicular distance from L1 to L5

Explanation

Achondroplasia causes a characteristic progressive decrease in the interpedicular distance from L1 to L5, leading to severe lumbar spinal stenosis. This results in classic symptoms of neurogenic claudication.

Question 5584

Topic: 6. Spine

A 6-month-old infant with achondroplasia is noted to have central apnea, brisk deep tendon reflexes, and hypotonia. An MRI of the craniocervical junction is obtained. What is the most critical complication that must be ruled out or treated urgently in this patient?

. Cervical kyphosis
. Atlantoaxial rotatory subluxation
. Foramen magnum stenosis leading to cervicomedullary compression
. Syrinx of the thoracic spinal cord
. Tethered cord syndrome

Correct Answer & Explanation

. Foramen magnum stenosis leading to cervicomedullary compression

Explanation

Infants with achondroplasia are at high risk for foramen magnum stenosis, which can cause cervicomedullary compression. Symptoms include sleep apnea, hyperreflexia, and hypotonia, often requiring urgent surgical decompression.

Question 5585

Topic: 6. Spine

Which of the following radiographic findings is considered pathognomonic for osteomalacia and typically occurs on the compression side of the bone?

. Brown tumors
. Looser zones (pseudofractures)
. Rugger jersey spine
. Bamboo spine
. Erlenmeyer flask deformity

Correct Answer & Explanation

. Looser zones (pseudofractures)

Explanation

Looser zones, or pseudofractures, are wide, transverse radiolucencies traversing part of the bone, frequently on the compression side. They are pathognomonic for osteomalacia.

Question 5586

Topic: 6. Spine

Which of the following cervical spine manifestations is most characteristic of Spondyloepiphyseal Dysplasia Congenita (SEDC) but NOT typical for Achondroplasia?

. Foramen magnum stenosis
. Severe cervical lordosis
. Atlantoaxial instability due to odontoid hypoplasia
. Premature fusion of the cervical facet joints
. Congenital cervical block vertebrae

Correct Answer & Explanation

. Atlantoaxial instability due to odontoid hypoplasia

Explanation

SEDC is a type II collagenopathy characterized by severe epiphyseal dysplasia and odontoid hypoplasia, leading to marked atlantoaxial instability. In contrast, achondroplasia is classically associated with foramen magnum stenosis, not atlantoaxial instability.

Question 5587

Topic: Thoracolumbar Spine & Deformity

A newborn presents with rhizomelic short stature, bilateral clubfeet, "hitchhiker" thumbs, and cystic swelling of the pinnae. Mutations in the SLC26A2 gene are suspected. Which of the following spinal deformities is most characteristic of this condition?

. Atlantoaxial instability
. Progressive cervical kyphosis
. Congenital scoliosis with hemivertebrae
. Thoracolumbar hyperlordosis
. Lumbosacral spondylolisthesis

Correct Answer & Explanation

. Progressive cervical kyphosis

Explanation

The patient has diastrophic dysplasia (SLC26A2 mutation). A hallmark and potentially life-threatening complication of this condition is progressive cervical kyphosis, which can cause neurologic compromise.

Question 5588

Topic: 6. Spine

An adult male with achondroplasia presents with progressive neurogenic claudication and lower extremity weakness. Which of the following distinct anatomic features of the achondroplastic spine most directly causes this pathology?

. Hypertrophy of the ligamentum flavum
. Decreased interpedicular distance from L1 to L5
. Severe rotatory scoliosis
. Congenital absence of the pars interarticularis
. Ossification of the posterior longitudinal ligament

Correct Answer & Explanation

. Decreased interpedicular distance from L1 to L5

Explanation

Achondroplasia features a progressive narrowing of the interpedicular distance from the upper to the lower lumbar spine, combined with short pedicles, leading to severe congenital spinal stenosis.

Question 5589

Topic: 6. Spine

A 16-year-old boy presents with back pain. Radiographs reveal an expansile lesion in the spine as shown.

Which of the following is the most likely location of this tumor?

. Vertebral body
. Posterior elements
. Intervertebral disc
. Anterior longitudinal ligament
. Pedicle exclusively

Correct Answer & Explanation

. Posterior elements

Explanation

Osteoblastomas of the spine classically arise in the posterior elements. They are typically expansile and can cause painful scoliosis, requiring surgical excision for definitive treatment.

Question 5590

Topic: 6. Spine

A 6-year-old girl with severe short stature, genu valgum, and corneal clouding is evaluated. Radiographs reveal universal platyspondyly and hypoplasia of the odontoid. A urine test is positive for keratan sulfate. What is the most critical orthopedic concern prior to any surgical intervention involving general anesthesia?

. Restrictive lung disease
. Atlantoaxial instability
. Aortic root dilation
. Malignant hyperthermia
. Rapidly progressive scoliosis

Correct Answer & Explanation

. Atlantoaxial instability

Explanation

The patient has Morquio syndrome (Mucopolysaccharidosis Type IV), diagnosed by urinary keratan sulfate. Odontoid hypoplasia leads to severe atlantoaxial instability, necessitating meticulous cervical spine evaluation before intubation or general anesthesia.

Question 5591

Topic: 6. Spine

A 5-year-old girl with an established diagnosis of Spondyloepiphyseal Dysplasia congenita (SEDc) presents for a routine orthopedic evaluation. Because of her condition, she is at highest risk for which of the following potentially life-threatening complications?

. Restrictive lung disease from severe progressive scoliosis
. Atlantoaxial instability due to odontoid hypoplasia
. Malignant hyperthermia during general anesthesia
. Aortic root dilation and dissection
. Rapid progression to acute myeloid leukemia

Correct Answer & Explanation

. Atlantoaxial instability due to odontoid hypoplasia

Explanation

SEDc is caused by a COL2A1 mutation and is characterized by a short trunk, coxa vara, myopia, and odontoid hypoplasia. Atlantoaxial instability is a major risk and requires careful screening, particularly before any procedure involving general anesthesia or intubation.

Question 5592

Topic: Cervical Spine

A 6-year-old boy presents with short-trunk dwarfism, corneal clouding, and normal intelligence. Radiographs demonstrate severe platyspondyly and odontoid hypoplasia. Urine tests reveal elevated levels of keratan sulfate. This clinical picture is most consistent with a deficiency in which enzyme?

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

Correct Answer & Explanation

. N-acetylgalactosamine-6-sulfatase

Explanation

The presentation is classic for Morquio syndrome (MPS Type IV), which features normal intelligence, severe skeletal dysplasia, odontoid hypoplasia, and keratan sulfate in the urine. It is caused by a deficiency in N-acetylgalactosamine-6-sulfatase (Type IVA).

Question 5593

Topic: 6. Spine

A 6-year-old boy presents with localized back pain. Radiographs show a completely flattened C5 vertebral body (vertebra plana) with intact adjacent disc spaces. Biopsy of the lesion would most likely show cells positive for which of the following markers?

. Cytokeratin and EMA
. S100 and CD1a
. CD99 and FLI-1
. Vimentin and SMA
. CD45 and CD20

Correct Answer & Explanation

. S100 and CD1a

Explanation

The presentation of vertebra plana in a child is highly characteristic of Eosinophilic Granuloma (Langerhans Cell Histiocytosis). The Langerhans cells are characteristically positive for S100 and CD1a, and contain Birbeck granules on electron microscopy.

Question 5594

Topic: 6. Spine

A 5-year-old child with a known diagnosis of achondroplasia is being evaluated. What is the most common cause of early childhood mortality in patients with this condition?

. Foramen magnum stenosis causing central apnea
. Cervical kyphosis causing myelopathy
. Atlantoaxial instability
. Cor pulmonale from chest wall deformity
. Hydrocephalus

Correct Answer & Explanation

. Foramen magnum stenosis causing central apnea

Explanation

Foramen magnum stenosis leading to cervicomedullary compression and subsequent central apnea is the leading cause of mortality in infants and young children with achondroplasia. Careful neurologic monitoring is mandatory.

Question 5595

Topic: 6. Spine

A 6-year-old child presents with short-trunk dwarfism, corneal clouding, normal intelligence, and marked atlantoaxial instability secondary to odontoid hypoplasia. Which enzyme deficiency is responsible for this condition?

. Fibroblast growth factor receptor 3 (FGFR3)
. Galactosamine-6-sulfatase
. Alpha-L-iduronidase
. Type I collagen
. Cartilage oligomeric matrix protein (COMP)

Correct Answer & Explanation

. Galactosamine-6-sulfatase

Explanation

Morquio syndrome (Mucopolysaccharidosis Type IV) is caused by a deficiency in galactosamine-6-sulfatase (Type A) or beta-galactosidase (Type B). It classically presents with severe skeletal dysplasia, odontoid hypoplasia predisposing to cervical myelopathy, and normal intelligence.

Question 5596

Topic: 6. Spine

A 7-year-old boy presents with a lytic skull lesion and back pain due to a collapsed vertebral body (vertebra plana). Biopsy reveals an abundance of distinct histiocytes with grooved nuclei. Which immunohistochemical markers are classically positive in the lesional cells?

. CD99 and FLI-1
. S-100 and CD1a
. Vimentin and SMA
. Cytokeratin and EMA
. HMB-45 and Melan-A

Correct Answer & Explanation

. S-100 and CD1a

Explanation

The presentation of vertebra plana and lytic skull lesions is classic for Eosinophilic Granuloma (Langerhans cell histiocytosis). The Langerhans cells are immunohistochemically positive for S-100 and CD1a, and show Birbeck granules on electron microscopy.

Question 5597

Topic: 6. Spine

A 15-year-old girl presents with progressive back pain. Radiographs of her spine demonstrate an expansile, predominantly lytic lesion as shown in image A.

If this lesion is confirmed as an osteoblastoma, what is the most common spinal compartment initially involved?

. Vertebral body
. Anterior longitudinal ligament
. Posterior elements
. Intervertebral disc space
. Pedicle extending into the adjacent rib

Correct Answer & Explanation

. Posterior elements

Explanation

Osteoblastomas most frequently arise in the posterior elements of the spine (lamina, spinous process, pedicles). They typically present as expansile lytic lesions with varying degrees of sclerosis and cortical thinning.

Question 5598

Topic: 6. Spine

A 4-year-old boy with achondroplasia presents for a routine orthopedic evaluation. His parents are concerned about his bowing legs and his occasional snoring. Which of the following is the most critical screening evaluation recommended to prevent sudden mortality in this patient population?

. Serial long-leg alignment radiographs
. Flexion-extension radiographs of the cervical spine
. MRI of the craniovertebral junction
. DEXA scan for bone mineral density
. Echocardiogram for aortic root dilation

Correct Answer & Explanation

. MRI of the craniovertebral junction

Explanation

Children with achondroplasia are at high risk for foramen magnum stenosis, which can cause cervicomedullary compression, central sleep apnea, and sudden death. Screening with sleep studies and a careful neurological exam is critical, often prompting MRI evaluation.

Question 5599

Topic: 6. Spine

A 15-year-old girl presents with a painful scoliosis. Radiographs of the spine are obtained as shown.

If this lesion causes a scoliotic deformity, which of the following best describes the typical curve pattern?

. Apex of the curve is directed towards the lesion
. Apex of the curve is directed away from the lesion
. The curve is typically a rigid double major curve
. The curve is always left-sided
. The curve resolves spontaneously without excision

Correct Answer & Explanation

. Apex of the curve is directed away from the lesion

Explanation

Osteoid osteomas and osteoblastomas in the spine typically cause a painful scoliosis with the apex of the curve directed away from the lesion. This creates a concavity on the side of the lesion due to asymmetric muscle spasm.

Question 5600

Topic: 6. Spine

A 4-year-old boy with achondroplasia presents with progressive weakness in his upper and lower extremities and sleep apnea. What is the most likely anatomic cause of these new neurologic findings?

. Thoracolumbar kyphosis
. Lumbar spinal stenosis
. Foramen magnum stenosis
. Atlantoaxial instability
. Cervical syrinx

Correct Answer & Explanation

. Foramen magnum stenosis

Explanation

In infants and young children with achondroplasia, foramen magnum stenosis can cause cervicomedullary compression leading to sleep apnea, hyperreflexia, and tetraparesis. It may require urgent suboccipital decompression.

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