A 70-year-old man is admitted with an acute stroke. Examinatio | Neurology collections 2020

A 70-year-old man is admitted with an acute stroke.
Examination revealed a left Horner's syndrome, loss of corneal reflex on the left together with loss of pinprick
sensation on the left face.
His left gag reflex was also decreased. He had left limb ataxia with right hemi-sensory loss of pain and
temperature sensation.
Which one of the following arterial territories has been affected?