Ophthalmic Branch of the Trigeminal Nerve
The Trigeminal Nerve is the fifth of the Twelve Cranial Nerves, which is divided into three main branches: the ophthalmic nerve, the maxillary nerve and the mandibular nerve. Its first division is the ophthalmic branch, which consists of afferent sensory fibers. The word afferent means toward the centre, as in from a peripheral area of a limb to the central nervous system. The word efferent is the opposite of afferent, meaning away from the centre and toward the periphery; when the stimulus is carried back to the brain from a peripheral area.
The pathway for afferent sensory fibers of the ophthalmic nerve from the proprioceptors until the trigeminal nuclei (after the merger into one main cranial nerve) is the following (from the initiation in the periphery to the termination in the brain):
- The ophthalmic branches innervate the ophthalmic area (see image) which starts at the tip of the nose and continues bilaterally up the nose separating the bridge from the nostrils and turns laterally at the medial corner of the eye and continues subohthalmically.
- At the temporal region the border travels cranially and covers the forehead, the anterior scalp and finishes half way down the parietal bone.
- The ophthalmic area consists of the following nerves: the anterior ethmoidal nerve which gives external and internal nasal branches; the supratrochlear and infratrochlear nerves; the supraorbital nerve; the long and short ciliary nerves, which contain postganglionic fibers from the ciliary ganglion; the frontal nerve and the lacrimal nerve.
- Both the preganglionic fibers from the ciliary ganglion and fibers from the peripheral branches merge into the ophthalmic branch.
- The ophthalmic branch gives off a recurrent tentorial branch which supplies the tentorium cerebelli and supratentorial falx cerebri.
- The ophthalmic nerve then synapses on the trigeminal ganglion, otherwise known as the gasseri ganglion or semilunar gasseri.
- The fibers then continue to the pontine nucleus and then the spinal nucleus and spinal tract.