Just below that is the trigeminal nerve, the largest of the cranial nerves, which branches into three main strands — hence the 'tri' — and innervates the face and jaw muscles.
Since the trigeminal and sacral nuclei serve just one side of the face or body, herpes vesicles and ulcers develop on the ipsilateral or same side as the affected nuclei.
In one small study, 93% of migraine patients were also prone to brain freeze, which has led researchers to suspect that the trigeminal nerve also plays a key role in migraines.
The trigeminal nerve normally transmits touch, temperature, and other sensations from the skin to most of the face, part of the scalp, and some of the blood vessels and layers covering the cerebral cortex.