Eye movement
Ocular deviation and reflex movements of the eyes in response to head
movement can be used to assess damage to the pons (a part of the
brainstem that communicates between brain and spinal cord and also
controls many autonomic functions), although these are also affected by
cortical damage. If the head is moved, reflex responses cause the eyes
to move in the opposite direction. In a conscious person, these reflexes
are suppressed. Presence of the reflex indicates cortical damage, but
complete absence in a comatose patient is due to pons damage.9
Absence of the corneal reflex (bilateral blinking in response to gentle
stimulation of the cornea) also indicates pons damage. This refl ex may
be absent when CNS depressant drugs such as opioids, benzodiazepines,
barbiturates and anaesthetics have been administered.