MSFinals-2717

MSFinals-2717

A 56-year-old male with chronic back pain presents with new onset bilateral leg pain which radiates bilaterally down the back of his thighs and legs. He denies any strenuous activity over the past few days and has not been performing any activities outside his daily routine during which he works as a librarian. He reports to have noticed some mild perianal reduced sensation in the past few days. He has no other past medical history of note and only takes ibuprofen as a regular analgesic for his back pain.

Observations show:
Blood pressure: 149/86 mmHg
Pulse: 92bpm
Temperature: 36.9ºC
Respiratory rate: 20/min
Oxygen saturations: 99% in room air

On examination, he is noted to have hyporeflexia in both ankles and some reduced dorsiflexion in his right foot – neurological examination is unremarkable. Per-rectum examination shows no loss of anal tone.

What is the most likely diagnosis?