Table 17-13 Pupils in Comatose Patients

Bilaterally Large Reactive Pupils

May be due to cocaine, amphetamine, LSD, or other sympathetic nervous system agnoists.

Bilaterally Fixed and Dilated

May be due to severe anoxia and its sympathomimetic effects, as seen after cardiac arrest. May also result from atropine-like agents, phenothiazines, or tricyclic antidepressants.

Bilaterally Small Pupils

(1-2.5 mm) Suggest damage to the sympathetic pathways in the hypothalamus, or metabolic encephalopathy, a diffuse failure of cerebral function that has many causes, including drugs. Light reactions are usually normal.

Pinpoint Pupils

(<1 mm) suggest a hemorrhage in the pons, or the effects of morphine, heroin, or other narcotics. The light reactions may be seen with a magnifying glass.

Midposition Fixed Pupils or Slightly Dilated Pupils

Pupils that are in this position (4-6 mm) and are fixed to light suggest structural damage in the midbrain

One Large Pupil, Fixed and Dilated

Warns of herniation of the temporal lobe, causing compression of the oculomotor nerve and midbrain. Commonly seen in diabetic patients with infarction of CN III