A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 54-year-old woman with a past medical history of mental retardation, hypertension, and diabetes presents to the emergency department with a change in her behavior. Her caretakers state that the patient’s gait suddenly became ataxic, and she became less responsive than her normal non-verbal baseline. Her temperature is 98.5°F (36.9°C), blood pressure is 125/68 mmHg, pulse is 90/min, respirations are 15/min, and oxygen saturation is 99% on room air. Physical exam is notable for an unremarkable HEENT exam with normal facial features and no signs of airway compromise. Neurological exam is remarkable for new onset spasticity. The patient has 3+ reflexes and a positive Babinski sign. Musculoskeletal exam is only notable for symmetric swelling and deformities of the patient’s hands bilaterally. Additionally, there is a "clunk" when posterior force is applied to the head while anterior force is applied to the cervical spine. Which of the following is the most likely risk factor that predisposed this patient to this condition?
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A
Cerebral palsyIncorrect. Cerebral palsy can cause spasticity but does not cause the erosive atlantoaxial ligamentous disease that produces this clunk.
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B
Diabetes mellitusIncorrect. Diabetes does not cause atlantoaxial subluxation.
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C
Down syndromeIncorrect. Down syndrome is also a major cause of atlantoaxial instability, but the hand deformities here are characteristic of RA.
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D
Rheumatoid arthritisCorrect. Rheumatoid arthritis causes erosive synovitis at C1-C2 with transverse ligament incompetence, producing atlantoaxial subluxation and cervical myelopathy.
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E
OsteoarthritisIncorrect. Osteoarthritis causes DIP and PIP joint changes (Heberden and Bouchard nodes) without cervical ligamentous incompetence; rheumatoid arthritis erodes the C1-C2 transverse ligament, producing atlantoaxial subluxation.
↑ Tap an answer to reveal the reasoning
Answer: D. This patient has "mental retardation" and bilateral symmetric MCP/hand deformities suggestive of long-standing rheumatoid arthritis (RA). She develops acute spasticity, hyperreflexia, positive Babinski sign (upper motor neuron signs), and a palpable "clunk" with anterior-posterior force at the cervical spine (the Sharp-Purser test). These findings are classic for atlantoaxial subluxation/instability with cervical myelopathy.
The principal risk factor among the choices is rheumatoid arthritis. RA produces erosive synovitis of the atlanto-axial (C1-C2) joint, eroding the transverse ligament that holds the dens of C2 against the anterior arch of C1. With ligamentous incompetence, C1 can slip anteriorly on C2 (atlantoaxial subluxation), compressing the cervical spinal cord. Even minor trauma or neck flexion (e.g., during intubation) can precipitate catastrophic cord injury. Preoperative cervical flexion-extension radiographs are routine in RA patients before elective surgery.
Down syndrome is also a major cause of atlantoaxial instability (laxity of the transverse ligament from congenital connective tissue abnormalities), but this patient's described hand deformities (symmetric swelling and joint deformities of the MCPs) point to RA rather than Down syndrome. Cerebral palsy can cause cervical spine spasticity but not the typical clunk/instability. Diabetes does not predispose to atlantoaxial instability.
**Why each option:**
**A.** Cerebral palsy can cause spasticity but does not cause the erosive atlantoaxial ligamentous disease that produces this clunk.
**B.** Diabetes does not cause atlantoaxial subluxation.
**C.** Down syndrome is also a major cause of atlantoaxial instability, but the hand deformities here are characteristic of RA.
**D.** Correct. Rheumatoid arthritis causes erosive synovitis at C1-C2 with transverse ligament incompetence, producing atlantoaxial subluxation and cervical myelopathy.