0:32 This is Dr. Adel Bontok, Professor of Anatomy and Neuroscience. Today I will talk about the facial nerve. Reminding you of the main points about any cranial nerve. You should know the origin from the brain, the deep origin, how it exits from the brain, and then exit from the skull and then a brief course outside the cranial cavity branches and the distribution and the effect of a lesion so
1:17 start by the deep origin of the facial nerve the facial nerve has four nuclei motor nucleus present in the pons and it supplies muscles of facial expression. Parasympathetic nucleus, which is the superior salivary nucleus. This superior salivary nucleus supplies two groups of glands, submandibular and sublingual salivary glands through the cordotimbani branch of the facial nerve, and the lacrimal and nasal and palatine glands
2:03 through the greater superficial petrosal nerve. So the parasympathetic nucleus is the superior salivary nucleus. It supplies submandibular and sublingual salivary glands through the chorda tympani branch. It supplies lacrimal nasal and palatine glands through the greater superficial petrosal nerve. The facial nerve contains two types of sensory fibers. Test fibers they enter solitary nucleus or nucleus solitarius and sensory fibers from the auricle and they end in the spinal trigeminal nucleus. So the four nuclei of the facial nerve, motor nucleus in the pons for
2:51 the muscles of facial expression, parasympathetic nucleus in the pons, superior salivatory nucleus, supplies submandibular and sublingual salivary glands through the corda temporal, and also supplies lacrimal, nasal and palatine glands through the greater superficial betrothal nerve. It also contains two sensory nuclei, the deep origin, nucleus solitarius in the medulla, it is for taste sensation from the anterior to the sears of the tongue, and also spinal trageuminal nucleus for pain and temperature sensation from the auricle and it's also present in the medulla. Again, the four nuclei of the facial nerve,
3:41 motor nucleus in the pons. The axons of this motor nucleus form a loop around the abducing nucleus forming together the facial colliculus. Therefore, the facial colliculus is formed of abducent nucleus and facial nerve fibers, therefore lesion of the facial colliculus causes paralysis of the abducent nerve and facial nerve. So this is the motor nucleus in the pons for the muscles of facial expression. Then parasympathetic nucleus, superior salivatory nucleus. This parasympathetic nucleus innervates all the glands of the head and neck except the parotid gland. and the two sensory
4:30 nuclei, nucleus solitarius or solitary nucleus for taste sensation from the anterior to the third of the tongue and the spinal trigeminal nucleus for sensation from the auricle. Actually, the facial nerve is formed of two roots, motor root from the motor nucleus, okay, and the sensory root called the nervous intermedius. This sensory root carries sensory fibers and also parasympathetic fibers. So the parasympathetic fibers run in the sensory root or in nervous intermediates. Then we'll talk about exit from the brain and exit from the cranial cavity. This
5:19 is the facial nerve. It exits in the cerebellopontine angle. This is the cerebellopontine angle. and regarding exit from the cranial cavity through this foramen internal auditory meatus. Then we'll talk about the course of the facial nerve. We'll start where it exit from the brain, cerebellum-bontine angle. Then it enters the internal auditory meatus. Then it passes in the facial canal. Then it exits from the stylomastoid foramen. Then it enters the parotid gland,
6:09 where it terminates into five terminal branches. Again, the course of the facial nerve starts by the cerebellopontine angle. It enters the internal auditory mitis with the vestibulocochlear nerve and the lebroncyon artery. enters the facial canal which is related to the medial wall and the posterior wall of the middle ear it exits from the stylomastoid foramen it enters the parotid gland and inside the parotid gland it divides into five terminal branches while in the facial canal
6:59 it has a ganglion called geniculate ganglion, sensory ganglion. So the sensory ganglion of the facial nerve is called geniculate ganglion and it is present in the facial canal. Then we'll talk about the branches of the facial nerve, but before talking about the branches of the facial nerve, let us just remind you of the course. Cerebellum bontine angle, internal auditory metas, facial canal, stytomastoid foramen, then parotid gland, and then divides into the five terminal branches. Geniculate ganglion is present in the facial canal. It is a sensory ganglion.
7:47 So regarding the branches of the facial nerve, we have branches in the facial canal, branches at the stytomastoid foramen, and the branches in the parotid gland. In the facial canal, it gives the three branches. The first branch is this one, greater superficial petrosal nerve. Yes. This greater superficial petrosal nerve joins the deep petrosal nerve, and the deep petrosal nerve is of sympathetic fibers from the plexus around the internal carotid artery and the two form nerve of the regoid canal or vidian
8:33 nerve. The greater superficial petrosal nerve carries the parasympathetic fibers to the lacrimal gland, nasal glands and the palatine glands. This greater superficial petrosal nerve synapses in the sphenopalotene ganglion. Again, the first branch is the greater superficial petrosan nerve. It carries parasympathetic fibers. These parasympathetic fibers synapse in the sphenopalotene ganglion and are distributed to lachromal gland, nasal glands, and the palatine glands. The greater superficial petrosan nerve joins the deep petrosan nerve to form
9:21 vidian nerve or nerve of trigoid canal. Second branch is nerve to stebedius muscle. It enters the middle ear through the posterior roll of the middle ear, nerve to stebedius. The third branch is the chorda tympani. This is the chorda tympani. It joins the linvo nerve and this chorda tympani contains test fibers to the anterior to the sides of the tongue, and the parasympathetic fibers which synapse in the submandibular ganglion, and then the postganglionic fibers are distributed to the submandibular and the sublingual salivary glands.
10:08 There are four branches in the facial canal, two parasympathetic branches, greater petrosal nerve, and the corda tympani. H1 synapses in a ganglion. The greater superficial betrothal nerve synapses in the sphenopalotain ganglion. The chorda tympani synapses in the submandibular ganglion. The greater superficial betrothal nerve supplies three groups of glands, lacrimal, nasal, and apalotain glands. The chorda tympani supplies two types of glands, submandibular and sublingual salivary glands. Therefore, the facial nerve supplies all the glands of the head
10:57 and neck except the parotid gland which is supplied by the glossopharyngeal nerve. Then branches at the stylomastoid foramen. Two branches. Posterior auricular nerve to the occipital belly of the occipitofrontalis and auricular muscles and the nerve to posterior belly of the gastric to the digastric muscle, to the posterior belly of the digastric and stylohyoid muscle. Then branches in the parotid gland, terminal branches in the parotid gland, five terminal branches temporal zygomatic buccal mandibular and cervical branches to the muscles of facial expression, like frontalis,
11:44 orbicularis oculi, vaccinator, orbicularis uris, zygomaticus major, zygomaticus minor, and all muscles of facial exeperation. Again, branches of the facial nerve. In the facial canal, three branches, greater superficial gutrosal nerve, nervo stebedius, and chorda tympani. Greater superficial gutrosal nerve carries parasympathetic fibers to the sphenoplatin ganglion to be distributed to lacrymal gland, nasal glands and palatine glands. Nervus stebedius supplies the stebedius muscle and corda tympanii carries test fibers to the anterior to thirds of the tongue and the parasympathetic fibers synapse in submandibular ganglion to be distributed to the
12:33 submandibular and the sublingual salivary glands. As a stylomastoid foramen, it gives the posterior auricular nerve and the nerve to posterior belly of the gastric. and five terminal branches in the parotid gland, temporal, zygomatic, buccal, mandibular, and cervical. So when we talk about the parasympathetic innervation of the submandibular and the sublingual salivary glands, we start by the deep origin, by the nucleus, and the nucleus is superior salivary nucleus. Fibers enter the facial nerve, Then enter the chorda tympani. This is the chorda tympani. Then join the lingual
13:21 nerve. Synapse in the submandibular ganglion. And the postganglionic fibers supply the submandibular and the sublingual salivary glands. Again, parasympathetic fibers to submandibular and the sublingual salivary glands start by superior salivary nucleus. Then facial nerve, chorda tympani, lingual nerve. submandibular ganglion and then submandibular and sublingual salivary glands. Regarding the lacrymal gland, parasympathetic fibers to the lacrymal gland. How the parasympathetic fibers reach the lacrymal gland? It is too far from the nucleus. The nucleus, superior salivary nucleus,
14:08 the fibers enter the facial nerve. then greater superficial patrosal nerve. It joins the deep patrosal nerve to form a vidian nerve or nerve of the regoid canal. The parasympathetic fibers synapse in the sphenopalatine ganglion. The postganglionic fibers enter the maxillary nerve. Then the zygomatic branch and zygomatic temporal nerve And through a communication with the lacrimal nerve, the parasympathetic fibers reach the lacrimal gland. Again, the parasympathetic fibers to the lacrimal gland start by the superior salivary nucleus in the pons.
14:59 Fibers enter the facial nerve. Then through the greater superficial petrosal nerve, which joins the deep trussal nerve to form the vidian nerve or nerve of the trigoid canal. The parasympathetic fibers synapse in the sphenopalatine ganglion or trigopalatine ganglion. The postganglionic fibers enter the maxillary nerve through the ganglionic branches. Then from the maxillary nerve to the zygomatic nerve and from the zygomatic nerve to the zygomatic temporal nerve, and through communication with the lacrimal nerve, the fibers reach the lacrimal gland.
15:49 After exit from the stylomastoid foramen, the facial nerve enters the parotid gland. So at the stylomastoid foramen, it gives you two branches. Posteriorricular branch. posterior auricular branch to the occipital belly of occipitofrontalis and posterior auricular muscle and the nerve to posterior belly of the digastric to the posterior belly of the digastric and stylohyoid muscle. Inside the parotid gland, it gives the five terminal branches. Temporal branch to the frontalis and this is the zygomatic branch, orbicularis oris Buccal branch to the vaccinator, mandibular branch to other muscles of facial
16:40 expression, and cervical branch to the pelatesma. So the five terminal branches temporal zygomatic buccal mandibular and cervical to all muscles of facial expression, which include frontalis, orbicularis oculi, orbicularis aureus,
17:49 Let's talk about lesions of the facial nerve. We have two types of lesions, lower motor neuron lesion and upper motor neuron lesion. Lower motor neuron lesion is a lesion in the facial nerve or in the nucleus itself. Upper motor neuron lesion is a lesion in the corticobulbar tract. In lower motor neuron lesion due to paralysis of the facial nerve or the nucleus, there is complete paralysis of the same side of the face. In the upper motor neuron lesion due to affection of the corticobulbar fibers,
18:35 remember that the facial nucleus is divided into two parts. The upper part of the facial nucleus receives bilateral corticobulbar fibers, the lower part of the facial nucleus receives the fibers only from the opposite corticobulbar fibers. Therefore, lesion in the corticobulbar tract will lead to paralysis of the lower part of the opposite facial nucleus, causing the paralysis of the lower half of the contralateral side of the face. So an upper motor neuron lesion, complete paralysis of the same side of the face. An upper motor neuron lesion, paralysis of the lower half of the opposite side of the face, the orbicularis oculi is
19:21 intact in upper motor neuron lesion. In lower motor neuron lesion, orbicularis oculi is affected. Again, of course, this one is the lower motor neuron lesion. It is due to affection of the facial nerve itself, paralysis of the facial nerve. or facial nucleus and this is upper motor neuron okay and lower motor neuron lesion complete paralysis of the same side of the face here upper motor neuron lesion is due to affection of the corticobulbar fibers which lead to paralysis of the lower part of the opposite facial nucleus causing paralysis in the lower half
20:10 of the opposite side of the face therefore In lower motor neuron lesion, paralysis of the same side of the face. In upper motor neuron lesion, paralysis of the lower half of the opposite side of the face. The difference is the intact orbicularis oculi and frontalis muscles in upper motor neuron lesion. Lower motor neuron lesion of the facial nerve is due to affection of the facial nerve at inside. It may be at the facial colliculus. It may be at the cerebellum on time angle. It may be in the facial canal. It may be at the stylomastoid foramen. Compression of the facial nerve at the
20:56 stylomastoid foramen is called the Bell's palsy or Bell's paralysis. In Bell's palsy, due to paralysis at the stylomastoid foramen, Paralysis of the frontalis muscle causes inability to elevate the eyebrow. Paralysis of the orbicularis oculi inability to close the eye. Paralysis of the buccinator accumulation of food in the vestibule of the mouth. Paralysis of the orbicularis ores inability to whistle. Paralysis of the levators of the angle of the mouth causes drooping of the angle
21:44 of the mouth on the same side of paralysis. So again, signs of lower motor neuron lesion of facial nerve. Paralysis of frontalis, inability to elevate the eyebrow. Paralysis of the orbicularis oculi, inability to close the eye. The eye remains open. ok paralysis of the vaccinator accumulation of food in the vestibule of the mouse paralysis of the orbicularis oris inability to whistle paralysis of the levators of the angle of the mouse causes dropping of the angle of the mouse on the same side of paralysis so how do you know the side of
22:30 paralysis ok from the eye inability to close the eye and the number two from the angle of the mouse is the angle of the mouse is dropped on the side of paralysis so in this photo look at the angle this one so this is right side facial nerve paralysis look at this one right side facial nerve paralysis this one left side facial nerve paralysis and left side facial nerve paralysis the eye is open the eye is open the angle is dropped on the side of paralysis so this is lower motor neuron lesion an upper motor neuron lesion okay look at this this one
23:17 this one the patient is unable to close the eye and the angle of the mouse is dropped here so this is lower motor neuron lesion. So, in lower motor neuron lesion, paralysis of the same side of the chest and inability to close the eye. In this photo, the patient closes the two eyes. So, the orbicularis oculi of the two muscles are intact. Look at this angle, it's dropped on this side. So, this is upper motor neuron lesion, paralysis of the lower وشكرا لكم وشكرا لكم وشكرا لكم وشكرا
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