Notes

Neurologic Exam Highlight

Division 1 (the ophthalmic division):
- Covers the forehead
- Lies supero-anterior to the corner of the eye
Division 2 (the maxillary division) lies anterior to:
- The corner of the forehead
- The corner of the mouth
Division 3 (the mandibular division) lies anterior to:
- The tragus (the anterior aspect of the ear).
- The mentum (the chin).

Division 3 covers neither the outer ear or the angle of the mandible.
- They will be normal in isolated peripheral trigeminal nerve injury.
The coverage of the trigeminal nerve extends posteriorly past the superior pole of the head, and thus sensory deficit continues posterior to the superior pole of the head in CN 5 injury.
The coverage of the outer ear is complex: it involves the great auricular nerve (supplied by C2, C3) and cranial nerves 7, 9, and 10.
The angle of the mandible is covered by the great auricular nerve.

Trigeminal neuralgia causes frequent paroxysms of pain in one or more trigeminal nerve distribution that are worse with activity (like talking or eating), and characteristically have periods of remission and relapse. For the pathology of trigeminal neuralgia, like hemifacial spasm, think demyelination either from compression or more rarely, multiple sclerosis. Compressive causes include blood vessel compression, which is why microvascular decompression of the nerve is an important treatment.
Shingles often presents in a trigeminal nerve distribution because herpes zoster can lie dormant in the trigeminal ganglion. Pain and vesicle outbreak occur in the peripheral distributions. Antivirals are key to protecting the eye against herpes zoster ophthalmicus (zoster along the 1st division).