Saturday, March 13, 2021

Trigeminal Neuralgia Case File

Posted By: Medical Group - 3/13/2021 Post Author : Medical Group Post Date : Saturday, March 13, 2021 Post Time : 3/13/2021
Trigeminal Neuralgia Case File
Eugene C. Toy, MD, Lawrence M. Ross, MD, PhD, Han Zhang, MD, Cristo Papasakelariou, MD, FACOG

CASE 41
A 35-year-old woman complains of excruciatingly painful spasms in the right
cheek and chin. These pain episodes last for a few seconds and are intense. She
was diagnosed with multiple sclerosis 2 years previously. She is not taking medications
currently, although she previously received intravenous corticosteroid therapy.
Her physician says that her problem is related to the nerve that innervates the
skin of the cheek area.

 What is the most likely diagnosis?
 What is the anatomical explanation for this condition?


ANSWER TO CASE 41:

Trigeminal Neuralgia
Summary: A 35-year-old woman who has multiple sclerosis complains of excruciating
spasms of pain that affect her right cheek and chin and last for a few seconds.

• Most likely diagnosis: Trigeminal neuralgia.

• Anatomical explanation for this condition: Pain follows the distribution of CN V, which innervates the eyes, cheeks, and chin.


CLINICAL CORRELATION
Trigeminal neuralgia (tic douloureux) is among the most excruciating types of pain seen by clinicians and is so intense that it will cause the patient to wince. This young woman complains of several seconds of intense spasmodic pain of the right cheek and chin. Her history of multiple sclerosis is important because trigeminal neuralgia is relatively common in this group of patients. The character of the pain excludes some of the other common etiologies of head or facial pain such as migraine headache (usually throbbing unilateral pain with orbital involvement) or tension headache (bandlike constricting pain from the temples to the occiput bilaterally). She has no history of herpes simplex virus, which can also affect CN V. CN V has three branches of sensory distribution. Treatment includes carbamazepine or baclofen and, in severe cases, trigeminal nerve ablation.


APPROACH TO:
Trigeminal Nerve

OBJECTIVES
1. Be able to relate the dermatomes of the face to the branches of the trigeminal nerve (CN V)
2. Be able to list the functions of the trigeminal nerve

DEFINITIONS
MULTIPLE SCLEROSIS: Disease in which plaques in the nervous system arise because of the proliferation of fibrous connective tissue or glial cells. Sclerosis in general refers to hardening of the tissue, as in atherosclerosis, or hardening of the arteries.

BACLOFEN: Muscle relaxing drug that acts through type b γ-aminobutyric acid (GABAb) receptors.

CARBAMAZEPINE: Centrally acting anticonvulsive drug of unknown action.


DISCUSSION
The trigeminal nerve exits the brain from the lateral surface of the pons. The sensory fibers arise as a large root. Motor fibers to the muscles of mastication usually arise as a separate smaller root. The nerve courses on the lateral surface of the sphenoid bone deep to the cavernous sinus. The cell bodies of the sensory nerves form the trigeminal ganglion along the medial wall of the middle cranial fossa. Three large nerves emerge from the ganglion: the ophthalmic, maxillary, and mandibular divisions of the trigeminal nerve (Figure 41-1).

Branches of these nerves supply general sensation to the face and anterior scalp. The posterior scalp is supplied by cervical spinal nerves. The ophthalmic nerve supplies the dermatome that courses superiorly to the horizontal midline of the orbit. It also supplies the midline region of the nose. The maxillary nerve supplies the region over the maxilla, inferior to the orbit, including the lateral surface of the nose and the upper lip. A small band extends superiorly over the zygomatic arch and temporalis muscle. The mandibular division supplies a band of skin running superiorly over the temporalis muscle. The major branches of the ophthalmic nerve that supply skin are the supraorbital and supratrochlear nerves, which supply skin of the forehead and anterior scalp. The nasociliary nerve supplies skin over the medial nose through the external nasal branch of the anterior ethmoidal nerve.

trigeminal nerve anatomy
Figure 41-1. The trigeminal nerve. (Reproduced, with permission, from Waxman SG. Clinical Neuroanatomy, 25th ed. New York: McGraw-Hill, 2003:112.)

The maxillary nerve innervates the skin primarily through the infraorbital nerve. More laterally, the zygomaticofacial and zygomaticotemporal nerves also contribute. The branches of the mandibular nerve that innervate the skin are the auriculotemporal superiorly and the mental nerve (a branch of the inferior alveolar) inferiorly. The buccal nerve supplies skin over the cheek. This nerve also innervates buccal mucosa in the oral cavity. Although its branches pass through the buccinator, they do not provide motor innervation. The buccinator is supplied by the buccal branch of the facial nerve (CN VII).


COMPREHENSION QUESTIONS

41.1 A 56-year-old man had a stroke. Among other symptoms, a marked deficit in bite strength was observed on the affected side, indicating weakness in the muscles of mastication. Which of the following muscles is also innervated by the same nerve?
    A. Orbicularis oculi
    B. Platysma
    C. Anterior belly of digastric
    D. Stylohyoid
    E. Superior belly of omohyoid

41.2 A 45-year-old diabetic woman has developed shingles involving the right cornea. Through which nerve did the varicella virus most likely travel to the cornea?
    A. CN II
    B. CN III
    C. CN V
    D. CN VII

41.3–41.6 Match the following divisions (A–C) to the branches 41.3–41.6.
    A. CN V1
    B. CN V2
    C. CN V3
41.3 Auriculotemporal nerve
41.4 Lacrimal nerve
41.5 Supraorbital nerve
41.6 Infraorbital nerve


ANSWERS
41.1 C. The anterior belly of digastric is innervated by CN V3, as are the muscles of mastication. The platysma and orbicularis oculi muscles are supplied by CN VII.

41.2 C. The trigeminal nerve supplies sensory innervation to the cornea. Herpes simplex infections or varicella virus infections involving the face may travel through CN V to the cornea and endanger vision.

41.3 C. CN V3 supplies the auriculotemporal, buccal, and mental nerves.

41.4 A. CN V1 supplies the lacrimal, supraorbital, and supra- and infratrochlear nerves.

41.5 A. CN V1 supplies the lacrimal, supraorbital, and supra- and infratrochlear nerves.

41.6 B. CN V2 supplies the infraorbital and zygomaticotemporal nerves.


ANATOMY PEARL
 The trigeminal nerve (CN V) exits the brain from the lateral surface of the pons.
 The trigeminal nerve comprises three divisions: ophthalmic, maxillary, and mandibular.
 Branches of these nerves supply general sensation to the face and anterior scalp. The posterior scalp is supplied by cervical spinal nerves.

References

Gilroy AM, MacPherson BR, Ross LM. Atlas of Anatomy, 2nd ed. New York, NY: Thieme Medical Publishers; 2012:494−495, 502−503, 514−515, 530−533. 

Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy, 7th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:849−853, 1065−1067, 1081. 

Netter FH. Atlas of Human Anatomy, 6th ed. Philadelphia, PA: Saunders; 2014: plates 2, 12, 52, 122−123.

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