Gdx

Cisternal portion

Posterior cerebral artery IVcranial nerve Vcraniainerve VIII cranial nerve (cochlear)

Posterior communicating artery Posterior cerebral artery Posterior communicating artery Superior cerebellar artery

V cranial nerve at the trigeminal porus (piercing the dura of the petrous apex)

Antero-inferior cerebellar artery

III cranial nerve

Entry of the V cranial nerve into Meckel's cave

III crania! nerve VI crania! nerve Posterior communicating artery

VI cranial nerve (ophthalmic division) V2 cranial nerve (maxillary division)

VI cranial V cranial Posterior cerebral nerve nerve artery

III cranial nerve Posterior cerebral artery V cranial nerve

Optic tract

Posterior communicating artery

V cranial nerve Gasserian ganglion

III cranial nerve

VI cranial nerve

V3 cranial nerve [mandibular division) through the foramen ovale

VI cranial nerve

III cranial nerve

Posterior communicating artery

V3 cranial nerve (mandibular division)

Posterior communicating artery

Superior orbital fissure

Superior orbital fissure

Ophthalmic Abducent Trochlear Oculomotor nerve (VI) nerve nerve nerve

Ophthalmic Abducent Trochlear Oculomotor nerve (VI) nerve nerve nerve

Spinai tract of trigeminal nerve

- Spina! nucleus oftrlgeminal nerve

Sensory nucleus of trigeminal nerve

- Sensory root of trigeminal nerve

Mesencephalic nucleus of trigeminal nerve Mesencephalic tract of trigeminal nerve

Spinal nucleus of trigeminal nerve

Motor nucleus of trigeminal nerve

Spinal nucleus of trigeminal nerve

Motor nucleus of trigeminal nerve

Trigeminal Nucleus

Ophthalmic nerve (VI), branch of trigeminal nerve Maxillary nerve (V2), branch of trigeminal nerve ^^ Mandibular nerve (V3), branch of trigeminal nerve f^) Branches from cervical plexus

Dorsal rami of cervical spinal nerves ^^ Auricular branches of vagus nerve

Internal carotid artery

Dura] pass through the trigeminal porus at the petrous apex, toward Meckel's cave

Plexiform appearance of the gasserian ganglion

Basilar artery

Cisternal portion of the trigeminal nerve

Internal carotid artery

Plexiform appearance of the gasserian ganglion

Basilar artery

Cisternal portion of the trigeminal nerve

Dura] pass through the trigeminal porus at the petrous apex, toward Meckel's cave

What Nerves Pass Through Meckel Cave

Trigeminal nerve,cisternal portion

Ophthalmic Nerve Meningeal Branch

Gasserian ganglion

Gasserian ganglion

Carotid siphon

Carotid siphon

Maxillary nerve (V2J - | Pterygopalatine ganglion

Maxillary nerve (V2J - | Pterygopalatine ganglion

Mandibular nerve (V3)

Mandibular nerve (V3)

Gasserian ganglion Ophthalmic nerve Maxillary nerve Mandibular nerve

- Mandibular nerve (foramen ovale)

■ Middle meningeal artery (foramen spinosum)--

- Carotid artery, petrous segment (foramen lacerum) -

154 4 Cranial Nervesand Related Systems

Superior orbital fissure

Superior orbital fissure

Ophthalmic nerve

Maxillary sinus Pterygopalatine fossa Foramen rotundum (maxillary nerve) Petro-clival suture

Maxillary sinus Pterygopalatine fossa Foramen rotundum (maxillary nerve) Petro-clival suture

Internal acoustic meatus

Trigeminal groove

Internal acoustic meatus

Sphenoid sinus

Carotid canal

Foramen ovale [mandibular nerve)

--- Foramen spinosum (middle meningeal artery)

Petrous apex

Sphenoid sinus

Carotid canal

Foramen ovale [mandibular nerve)

Petrous apex

Facial (VII Cranial Nerve), Cochlear (VIII Cranial Nerve, pars Cochlearis), Vestibular (VIII Cranial Nerve, pars Vestibularis) Nerves, Related Systems and Petrous Bone

I. Facial Nerve (VII Cranial Nerve) and Its System

The motor nucleus of the facial nerve is placed in the tegmen of the pons, dorsally to the nucleus olivaris superior and ven-tromedially to the nucleus spinalis of the trigeminal nerve. The special visceral efferent (SVE) fibers emerging from the dorsal side of the nucleus are dorsomedially projected on the tegmen of the fourth ventricle. These fibers go up longitudinally, medially to the nucleus of the abducent nerve, and dor-sally to the medial longitudinal fasciculus; near the rostral pole of the abducent's nucleus, they curve ventrolaterally and emerge from the brainstem into the bulbopontine sulcus, in correspondence with the supraolivary fossa, and medially to the nervus intermedius. They innervate the facial mimetic muscles, the posterior belly of digastric muscle, the stylohy-oideus, styloglossus, platysma, buccinator, stapedius muscles, and some muscles of the velum palati.

This nucleus exhibits connections with the sensory nuclei of the V, VIII (cochlear), IX and X cc.nn.

The general somatic afferent (GSA) fibers carry cutaneous sensory impulses from the external auditory meatus and the region behind the ear; centrally, these fibers enter the dorsal portion of the spinal tract of the trigeminal nerve.

The preganglionic parasympathetic general visceral efferent (GVE) radicular component of the nervus intermedius, or Wrisberg's nerve, originates from two nuclei, the lacrimo-muconasal nucleus and the superior salivatory nucleus, located in the pons, rostrally to the inferior salivatory nucleus, and emerges from the bulbopontine sulcus, between the motor root of the facial nerve and the vestibular nerve.

The bundle of fibers originating from the lacrimo-mu-conasal nucleus emerges in the bulbopontine sulcus with the motor root of the facial nerve, and innervates the lacrimal gland, the nasal and buccal mucosa. The small radicular component originating from the superior salivatory nucleus spreads to the submandibular and sublingual glands.

These two nuclei are connected with the gustatory nucleus (VII, IX, and X cc.nn.) and the main sensory nucleus of the trigeminal nerve.

The special visceral afferent fibers (SVA) of the nervus intermedius reach the rostral portion of the nucleus of the trac-tus solitarius (gustatory nucleus), and carry the gustatory sensitivity of the front two-thirds of the tongue, whereas the general somatic afferent (GSA) fibers belong to the dorsal part of the spinal tract of the trigeminal nerve and carry cutaneous sensory impulses from the external auditory meatus and the region behind the ear.

The nerve crosses the ponto-cerebellar angle's cistern together with the VIII cranial nerve, enters the internal acoustic canal and penetrates its bottom. This is separated by a horizontal bony lamina (crista falciformis) into two compartments. The superior one is divided in two by a vertical fibrous wall. The complex facial-Wrisberg's intermediate nerve penetrates the upper-anterior compartment, and reaches the geniculate fovea in the petrous bone, where the geniculate ganglion is located. Here, fibers of the intermediate nerve separate and course anteriorly into the greater petrosal superficial nerve, toward the pterygopalatine ganglion and the lacrimal gland. The remaining fibers of the facial nerve curve backward and remain horizontal, then go downward reaching the foramen stylomastoideum, where they exit to join the parotid gland. Two main branches originate during this course: nervi stapedium and chorda tympani.

II. Cochlear Nerve, Vestibular Nerve (VIII Cranial Nerves) and Their Systems

II. 1. Acoustic System

Acoustic stimuli are generated by the tympanic membrane and are transmitted to the manubrium of the malleus, then to the incus and the stapes. The stapes base articulates with the oval window, which transmits the acoustic wave to the perilympha of the cochlea. The cochlea is a spiral structure composed of two and a half turns around a central bony structure, the modiolus. Each cochlear turn is divided by an osseous spiral lamina and a membranous one (basilar membrane), which contains the endolymphatic receptor system. Fibers originate from the basilar membrane, reach the spiral (Corti's) ganglion and cross the cribriform infero-anterior part of the internal wall of the internal acoustic canal (iac). Here, they form the cochlear nerve that joins the superior and inferior vestibular nerves and the posterior ampullary nerve, forming the VIII cranial nerve, and traveling together with the facial one through the ponto-cerebellar cistern. The cochlear component of the vestibulocochlear nerve reaches the ventral and dorsal cochlear nuclei on the lateral side of the inferior cerebellar peduncle in the bulbopontine area, entering the brainstem at the supraolivary fossa level and branching off. These nuclei present a tonotopic localization which is also maintained in the following tracts of the pathway: the fibers coming from the apical turn of the cochlea, where low-pitched tones are located, reach the nucleus cochlearis ventralis and the ventral part of the dorsal nucleus; the fibers coming from the basal turn of the cochlea, where high-pitched tones are located, terminate in the dorsal portion of the dorsal nucleus.

The cochlear nuclei form the central cochlear pathway that is made up of acoustic striae of ventral type (originated from the ventral nucleus), of dorsal type (originated from the dorsal nucleus) and of intermediate type (originated from the dorsal portion of the ventral nucleus). These provide fibers to the reticular formation and the nucleus olivaris superior of the corpus trapezoideum, of the lateral lemniscus and to the superior quadrigeminal body. They go on to cross the median raphe and, like the lateral lemniscus, reach the medial geniculate bodies and the telencephalic cortex (gyrus temporalis superior).

The motor nucleus of the V, VI and VII cc.nn. exhibits connections with these nuclei that are inserted along the central acoustic pathway.

II. 2. Vestibular System

The vestibular stimuli come from fibers collected together in three main branches: inferior and superior vestibular nerves and posterior ampullary nerve. The superior vestibular nerve receives fibers coming from utricle, and superior and lateral semicircular canals; the inferior vestibular nerve is formed by fibers from the saccule; fibers of the posterior semicircular canal are collected in the posterior ampullary nerve. The superior vestibular nerve crosses the posterior wall of the iac in the postero-superior space, while the postero-inferior is occupied by inferior vestibular and posterior ampullary nerves. After crossing the iac's posterior wall, the three nerves form Scarpa's ganglion. From this point on, the vestibular nerve joins the acoustic and fuses with it. Vestibular nuclei are located on the tegmen of the fourth ventricle, rostrally to the hypoglossal nucleus, and extend well beyond the nucleus of the abduceni nerve. They are reached by the fibers of the vestibular nerve which enter the brainstem in correspondence with the retroolivary fossa, at the bulbopon-tine sulcus level. Once they have entered the vestibular complex, they branch off and spread in various ways to the nuclei of the same and opposite side, and to the interstitial nucleus of the vestibular nerve which is located between the vestibular fibers near the point where the nerve enters the brainstem, and then move towards the cerebellar cortex (nodule, uvula and flocculus of the same side). They carry the stimuli of gravity and acceleration.

The nuclei are placed in two longitudinal columns: the lateral column includes the descending (Deiters' nucleus), lateral and superior vestibular nuclei; the medial column is made up of the medial vestibular nucleus.

The descending vestibular nucleus is located in the bulb medially to the accessory cuneate nucleus. It then spreads rostrally inside the inferior cerebellar peduncle as far as the site where the vestibular nerve enters the brainstem. Distinctive projections from the macula utriculi and the macula sac-cuii (dorsolateral portion of the descending vestibular nucleus) reach this point.

The vestibular nuclei present connections with the cortex (ascending frontal gyrus), the bone marrow (vestibular-spinal and spinal-vestibular tracts), the cerebellum (vestibulocerebellar and cerebellovestibular tracts), the reticular formation, the nuclei of the III, IV, VI, and XI cc.nn. through the medial longitudinal fasciculus, and with the motor nucleus of the V c.n.

Vestibular nuclei

Cochlear nuclei

Facial nerve

[internal genu)

Facial nucleus

Salivatory nucleus

Facial nerve

[internal genu)

Facial nucleus

Salivatory nucleus

Cochlear nerve Vestibular nerve — Facial nerve

Vestibulocochlear nerve

Cochlear nerve Vestibular nerve — Facial nerve

Vestibulocochlear nerve

0 motor fibers

# gland secretory fibers

# taste

# sensory fibers internal acoustic canal

Secretory Nerve Fibers

nervus intermedin facial nervei cochlear nerve vestibular nerve geniculate ganglion greater petrosal nerve nerve to stapedius

•muscle stylomastoid foramen posterior auricular"

nerve chorda ¡tympan i facial branches n. to posterior belly of* digastric and stylohyoid muscles

first segment (horizontal) of facial nerve C second segment (horizontal) of facial nerve gp third segment (vertical) of facial nerve ns second knee (geniculum) of facial nerve ct geniculate ganglion st petrous pyramid pontocerebellar angle cistern greater petrosal nerve n. to stapedius muscle chorda tympani stylomastoid foramen

Greater Petrosal Nerve
Facial and Intermediate (Wrisberg) Nerves

Interna! carotid artery

Petrous apex Greater superficial petrosal nerve Geniculate ganglion

Facial nerve (Vil), petrous segment

Clivus

Basilar artery

C.n.VIUntracanallcular segment

C.n. VII. cisternal segment

An tero-inferior cerebellar artery

Interna! carotid artery

Petrous apex Greater superficial petrosal nerve Geniculate ganglion

Facial nerve (Vil), petrous segment

Clivus

Basilar artery

C.n.VIUntracanallcular segment

C.n. VII. cisternal segment

An tero-inferior cerebellar artery

Facia! and intermediate nerves Cochlear nerve Inferior vestibular nerve Superior vestibular nerve Vertical fibrous wall Crista falciformis

Scarpa's gangliom

Membranous Labyrinth

Superior semicircular canal

Modiolus

Saccule

Utricle

Inferior vestibular nerve

Anteroinferior cerebellar artery

Basal cochlear turn

Posterior semicircular canal

Basal cochlear turn

Vestibular aqueduct

Superior semicircular canal

Modiolus

Saccule

Utricle

Inferior vestibular nerve

Anteroinferior cerebellar artery

Basal cochlear turn

Posterior semicircular canal

Basal cochlear turn

Vestibular aqueduct

Caudal pons

Facial nerve

Superior vestibular nerve

I . Upper cochlear turn

ISi Middle cochlear turn

Cochlear nerve I Pons

I- Medulla

Hypothyroid Brain Model

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