Overview
The
trigeminal nerve is the fifth cranial nerve. It emerges directly from the
surface of the pons, and supplies sensation to the face and motor supply to the
muscles of mastication. Sensation to the face is essential for things like the
corneal reflex. In addition, the muscles of chewing are also integral to daily
life.
Gross Anatomy
The
trigeminal nerve is also known as cranial nerve 5. The word trigeminal comes
from the word ‘tri’ meaning three, and the word ‘Gemini’ meaning twins. There
are three trigeminal nuclei. The mesencephalic nucleus of the trigeminal nerve
contains first order neurons that detect proprioception from the jaw,
temperomandibular joints, teeth and intraocular muscles. The principal nucleus
of the trigeminal nerve lies in the dorsolateral pontine tegmentum, and detects
tactile sensation. The spinal nucleus detects pain and temperature, and
stretches from the pons to the first three dorsal horn segments of the cervical
spinal cord.
It emerges
directly from the pons, and passes to a region known as Meckel’s cave (an
arachnoid pouch filled with cerebrospinal fluid and located near the apex of
the petrous portion of the temporal bone). Here it divides into three branches.
These are
the ophthalmic (V1), maxillary (V2), and the mandibular (V3). They are
responsible for providing sensation to the face. The mandibular division also
innervates the muscles of mastication i.e. the temporalis, medial and lateral
pterygoids, and the masseter. The divisions all exit the skull through
different foramina. V1 passes through the superior orbital fissure, V2 passes
through the foramen rotunda, and V3 passes through the foramen ovale. Both the
ophthalmic and maxillary divisions supply the nasal cartilage via their
terminal branches. The superior alveolar nerve is a branch of the maxillary
division and supplies the teeth of the maxilla. The lingual nerve (provides
sensation to the tongue and) and the inferior alveolar nerve (supplies the
teeth of the mandible) are branches of the mandibular division.
Clinical Anatomy
Trigeminal neuralgia- This
is a sudden and sharp stabbing pain in the distribution of the trigeminal
nerve, that lasts for a few seconds to a few minutes. Pain is typically brought
on by light touching of the face e.g. shaving, brushing teeth and washing. It
has been described as the worse pain imaginable by patients who suffer from it.
There are several theories about the cause of the disease, including
compression of the nerve by surrounding arteries (mist commonly the superior
cerebellar artery), and focal demyelination.
Quick Anatomy
Key Facts
Developmental precursor- Metencephalon (secondary brain vesicle)
Muscles-
Masseter, medial pterygoid, lateral pterygoid, temporalis
Dermatome-
The face, via the Ophthalmic, maxillary and mandibular divisions.
Aide-Memoire
Tri implies three (the nerve has three divisions)
Recall the nerve supplies sensation to the face, and the V3
division innervates the muscles of mastication
Summary
The
trigeminal nerve is the fifth cranial nerve. It supplies sensation to the face
and motor supply to the muscles of mastication.
References
1.
Frank H.Netter MD: Atlas of Human Anatomy, 5th Edition, Elsevier Saunders, Chapter 1 Head
and Neck
2.
Chummy S.Sinnatamby: Last’s Anatomy Regional and
Applied, 12th Edition, Churchill
Livingstone Elsevier
3.
Richard L. Drake, A. Wayne Vogl, Adam. W.M. Mitchell: Gray’s Anatomy for Students, 2nd Edition, Churchill Livingstone Elsevier
4.
Elliiot L.Manchell: Gray's
Clinical Neuroanatomy:
The Anatomic Basis for Clinical Neuroscience
5.
The Definitive Neurological Surgery Board
Review
By
Shawn
P. Moore, 2005
6.
Human Neuroanatomy
By
James R. Augustine, 2008