6th February 2024

A 67-year-old male with poor nutrition and excessive alcohol intake is admitted to the acute medical unit with sensory disturbance and weakness affecting his hands and feet.

A 67-year-old male with poor nutrition and excessive alcohol intake is admitted to the acute medical unit with sensory disturbance and weakness affecting his hands and feet. Examination reveals Romberg’s positive test. Bilateral loss of fine touch, vibration and proprioception was noted with preserved pain and temperature sensation. Bilateral weakness is accompanied by increased tone and spasticity. Hyperreflexia is noted on knee examination with absent ankle jerk bilaterally. Babinski sign positive.

Which of the following has caused his presentation?