A 55-year-old man presents with neck pain. One week previously | Neurology collections 2020

A 55-year-old man presents with neck pain.
One week previously he had attended for a sigmoidoscopy and was given intravenous sedation during this
procedure. One day prior to admission his neck and shoulders had become stiff.
On examination, the temperature was 38.0°C, blood pressure was 100/60 mmHg and heart rate 100 bpm.
There were absent biceps jerks and weakness of trapezius, deltoid and triceps bilaterally. The cranial nerves
and lower limbs were normal.
There was a soft systolic murmur, and the chest was clear.
Which examination is likely to confirm the diagnosis?