CN 1 – The Forgotten Cranial Nerve

When reviewing reports of people involved in motor vehicle collisions, I frequently notice that evaluations from other treating physicians state “Cranial Nerves 2 thru 12 tested and to be found within normal limits”.

I could replace the word “frequently” with “almost always”.

When I read this comment in injury reports, it makes me wonder one of two things — 1) were the cranial nerves truly tested; and 2) why was cranial nerve 1 NOT tested?

Cranial Nerve 1

Smell is a function of the 1st (olfactory) cranial nerve and should be evaluated after trauma to the head and neck, including a whiplash type injury.

How To Test CN 1

The patient is asked to identify odors (eg, soap, coffee, cloves) presented to each nostril while the other nostril is occluded. This is called the Smell Identification Test.

Alcohol, ammonia, and other irritants, which test the nociceptive receptors of the 5th (trigeminal) cranial nerve, are used only when malingering is suspected.

Impairment Rating

If Cranial Nerve 1 remains impaired after a steady course of treatment, and it is believed that the loss of smell is permanent, an impairment rating of up to 3% can be rendered according to the AMA Guides. This can help increase the settlement value of the patients case.