CN5 - Trigeminal Nerve

Trigeminal Neuralgia

Cranial nerves (CN) are nerves in the brain that are necessary for motor or sensory control in the body.

Cranial nerve 5 (CN5) , is the trigeminal nerve. The function of the trigeminal nerve includes; sensation of different parts of the face, and some movements of the head, jaw and nasal cavity. Cranial nerve 7, the facial nerve is responsible for the remainder movement of the face.

CN5 is a nerve that divides into three smaller nerves for different areas of the face and scalp, but those three nerves then branch into different areas of the head and face.

1. Neurofibromatosis Type 2 and Cranial Nerves

The most common nerve for schwannomas tumor growth to develop for individuals with Neurofibromatosis Type 2 (NF2) is the Vestibulocochlear Nerve, Cranial Nerve 8 (CN8). CN8 splits into two nerves; the Vestibular Nerve for the function of balance and the Cochlear Nerve for hearing. Most commonly the tumors grow on the branch for balance, but damaging the branch for hearing in the process, but is the reason for the name Vestibular Schwannoma (VS). The growth of these tumors often also results in damage to Cranial Nerve 7 (CN7), the Facial Nerve.

While the most common location of NF2 tumor growth is CN8, it is not the only location Schwannoma may develop in the brain. Schwannoma also commonly grow along CN10, the Vagus Nerve, and CN5, the Trigeminal Nerve. Schwannoma may also grow on other cranial nerves as well.

2. Trigeminal Neuralgia

Trigeminal Schwannomas (TS) is the name of the tumor when a Schwannomas grows on the Trigeminal Nerve. TS growth can result in Trigeminal Neuralgia, damage to Cranial Nerve 5, (CN5, CNV, or CN V), the Trigeminal Nerve. The damaged area of the nerve can be; inside the skull itself, along with the face, or both. Depending on how badly damaged and the exact location of the damage will determine what parts of the head, forehead, cheek or jaw including teeth might experience some level of pain, numbness or have no feeling at all.

3. Common Misunderstanding

Trigeminal Neuralgia, damage to CN5, is often confused with Facial Nerve, damage to Cranial Nerve 7, but the Facial Nerve only controls movement, not feeling in the face which is the function of Cranial Nerve 5, the Trigeminal Nerve.

Other common causes of facial pain include:

• Abscessed tooth (a condition in which inflammation and pus surround a tooth)
• Sinus Infection
• Sinusitis (inflammation of the sinuses)
• Injury to the face
• TMJ disorders (TMJ stands for temporomandibular joint, or the jaw joint)

4. Three Nerve Branches

Cranial Nerve 5 (CN5 also known as CN V), the Trigeminal Nerve includes the following three (3) branches:

1. CN V1 - Ophthalmic Nerve
2. CN V2 - Maxillary Nerve
3. CN V3 - Mandibular Nerve

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Ophthalmic Nerve (V1):

CN5 - V1 controls the muscles of the eyelids, eyebrow, forehead, and nose.

This branch affects the glands for tear production and mucous membrane of the nasal cavity.

• Supraorbital Nerve - Function for;
  1) Conjunctiva of the eye, moist membrane that protects the eye between the eyelid and the Sclera (white part of the eye), 2) Frontal Sinus, and 3) Skin from Forehead to Middle of the Scalp
• Supratrochlear Nerve
• Lacrimal Nerve
• Infratrochlear Nerve
• External Nasal Nerve

Maxillary Nerve (V2):

CN5 - V2 controls sensation from the maxillary, nasal cavity, sinuses and taste.

• Zygomaticotemporal Nerve
• Infraorbital Nerve
• Zygomaticofacial Nerve

Mandibular Nerve (V3):

CN5 - V3 controls face sensations and muscles for biting, chewing, and swallowing.

• Auriculotemporal Nerve
• Mental Nerve
• Buccal Nerve

5. Symptoms

Tooth Pain:

When dentists are not aware that a patient might have a condition that can cause nerve damage, TN (Trigeminal Neuralgia) symptoms can and often misdiagnosed and results in unnecessary Wisdom Teeth removals and Root Canals due to pain that causes tooth pain but is not a result of damaged teeth.

Other Symptoms

As the nerve damage gets worse, the pain worsens until even the strongest painkillers can make a person fall asleep before the pain stops. The longer an individual waits to have this treated, i.e. removing the problematic tumor, there is an increased risk of not being able to reverse the damage.

If the problem is a form of Trigeminal Neuralgia, you might also experience other facial pain that might last different durations in time with different durations breaks between episodes of pain, that feels like a stabbing electric shock, burning, pressing, crushing, exploding or shooting pain. Pain might not affect all three CN5 nerve branches and can be either one or both sides of the face.

This pain and damage could be the result of different issues, but for individuals with NF2, it is the most likely to be the result of a tumor growing on another nerve close to the brainstem just pushing on CN5, or a tumor growing somewhere on the CN5.

6. Treatment

Management:

Several pain medications that can be taken and other treatments are possible once properly diagnosed and exact reason for development of this issue is determined, different potential options might be available.

sodium channel blockers

Surgical Assessment:

Knowing exactly what part of the nerve is damaged would be needed for surgical assessment. This is possible with a vMRI, which is a MRI scan the looks specifically at nerves. Unfortunately if a tumor is the cause of the damage, even a vMRI would not say if the tumor is pushing on the nerve and a Meningioma or growing on it and a Schwannoma.

7. Facial Movement Issues

Damage to any part of this nerve should not result in facial movement issues. Facial movement is the result of CN7, the Facial Nerve.

8. Other Possible NF2 Reasons for Dental Issues

• radiation treatment - brain/head ^{[American Cancer Society]}
• anti-epileptic drugs ^{[Epilepsy Action, Well Being]}

9. Sources

1. AA Marinescu, A Mohan, G Popescu, AV Ciurea. The University of Medicine and Pharmacy, Romania. "Rare Neurosurgical Disease: Trigeminal Schwannoma - Literature Review" (2017) Source:http://journalofsurgicalsciences.com/download/no14/9.pdf
2. Olsen, J., and C. Sealey. "A brain tumour presenting as toothache and trigeminal neuralgia: a case report." New Zealand Dental Journal. Vol. 113 Issue 2, p10-12. (June, 2017)
   Source: http://web.b.ebscohost.com/abstract?direct=true&profile=...
3. Walker, H. K., Hall, W. D., & Hurst, J. W. "The History, Physical, and Laboratory Examinations" Clinical Methods, 3rd edition. (1990)
   Source: http://www.ncbi.nlm.nih.gov/books/NBK201/?amp=&partid=222
4. WebMD. "Facial Pain and Trigeminal Neuralgia." (Reviewed Date: August 2017)
   Source: http://www.webmd.com/pain-management/guide/trigeminal-neuralgia
5. "How Radiation Therapy Can Affect Different Parts of the Body." American Cancer Society.
   Source: https://www.cancer.org/treatment/treatments-and-side-effects/treatment-types/radiation/effects-on-different-parts-of-body.html
6. "Report: "Anti-epileptic medication has dental health implications." (2003) Epilepsy Action.
   Source: https://www.epilepsy.org.uk/news/report-anti-epileptic-medication-has-dental-health-implication
7. "Open Wide." Well Being.
   Source: https://www.epilepsysociety.org.uk/sites/default/files/DentalissuesJanuary2012.pdf