Pons



The pons (sometimes pons Varolii after Costanzo Varolio) is a knob on the brain stem. It is part of the autonomic nervous system, and relays sensory information between the cerebellum and cerebrum. Some theories posit that it has a role in dreaming.

Anatomy of the pons
The "knob-like" process is 2 centimeters long and located on the anterior (front) of the brainstem. It is formed by transverse pontine fibres that travel from one side (left or right) to the other. Most other fibres in the brainstem travel up and down.

The posterior (back) surface of the pons forms part of the wall of the fourth ventricle of the brain.

Most blood to the pons is supplied by pontine arteries. These are small arteries that branch off the basilar artery (of the Circle of Willis). Blood also comes from the anterior inferior, and superior cerebellar arteries.

Cranial nerve nuclei
A number of cranial nerve nuclei are present in the pons. The chief or pontine nucleus of the trigeminal nerve sensory nucleus, as well as the motor nucleus for the trigeminal nerve, are present in the mid-pons.

The abducens, vestibulocochlear, and facial nerve nuclei are present slightly lower down in the pons.

Usage in a diagnostic test
Radiological examination of MRI or CT scans of the pons can provide diagnostic evidence for multiple sclerosis.

Intracranial hemorrhage into the pons sometimes results in extreme miosis ("pin point pupils").