Thursday, August 4, 2011
Head Shaking Syndrome: Part 1 Trigeminal Nerve
The term "trigeminal" comes from the Latin "trigeminus" meaning "threefold," referring to the three divisions (ophthalmic, maxillary and mandibular) of this nerve.
The trigeminal nerve functions both as the chief nerve of sensation for the face and the motor nerve controlling the muscles of mastication (chewing).
In an effort to understand what my horse is going through I'm both studying HSS and journaling Cowboy's progress and symptoms. Veterinarians have a hard time diagnosing and treating this problem because of its many varieties and possible causes. I think I've narrowed Cowboy's down to photic issues--intense sun and heat trigger, but I want to know as much about it as I can in order to figure out the best way to help him.
My first question was--what is the Trigeminal Nerve and Equine Trigeminal Neuralgia. I have to understand this to know what I'm seeing with Cowboy.
I came across a wonderful site devoted to bitless riding that discussed this nerve and how the use of bits can affect it and possibly cause HSS. Horse and Human Bitless Training and Barefoot Trimming. They wrote this about the three areas the Trigeminal Nerve can affect:
The ophthalmic branch of the trigeminal nerve supplies nerves to parts of the eye [the cornea, ciliary body, lacrimal gland and conjuctiva], to parts of the mucous membrane of the nasal cavity and to the skin of the eyelids, eyebrows, forehead and nose
The maxillary branch of the trigeminal nerve supplies nerves to the lower eyelid, nose, upper lip and side of the face
The mandibular branch of the trigeminal nerve supplies nerves to the mucous membranes of two thirds of the tongue, teeth and gums, skin of the temporal region, lower lip and chin, the muscles used to chew, and to some parts of the ear.
The symptoms I've seen in Cowboy today are: 1. Relief of symptoms when removed from sun, 2. Excessive yawning, 3. Hanging his head to the ground in the sun, 4. Vertical head-bobbing when standing in sun.
What I've noticed before is possible vision impairment--not blindness, but maybe some sort of distortion.
It's interesting that this also occurs in humans. Here are sketches of the human face and the Trigeminal Nerve.
Humans have reported intense pain, suicidal thoughts and double-vision.
There is a possibility that sunshine irritates Cowboy's Trigeminal nerve and causes a stinging all along the inside of his nose. Yawning and chewing might relieve some of the itchiness and discomfort.
Here are the questions I've asked myself.
1. What are the outward signs he has shown?
2. When did they start? Were there any early signs I may have overlooked?
3. How did the symptoms progress?
4. Were teeth, nose and ear issues ruled out?
5. When was he last vaccinated?
6. What things give him relief?
7. What things make him worse?
8. How have I ruled out behavioral issues?
9. What is his pain or discomfort level on a scale of 1 to 5?
10. Is he safe to handle?
I'll explain why these are important questions in Part II.