Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
High Yield Cranial Nerve Anatomy ● this only covers info on previous exams ● CN I, XI, and XII not tested ● typically 5 questions per exam CRANIAL NERVE TERMS: Efferent ● General efferent fibers (GVE or visceral efferent or autonomic efferent): provide motor innervation to smooth muscle, cardiac muscle, and glands.. May be either sympathetic or parasympathetic. ○ oculomotor nerve (CN III), facial nerve (CN VII), glossopharyngeal nerve (CN IX) and vagus nerve (CN X). ● Special visceral efferent (SVE) : provide motor innervations to the muscles of the pharyngeal arches in humans and branchial arches in fish. Also called "branchiomotor",or "branchial efferent". ○ trigeminal nerve (V), facial nerve (VII), glossopharyngeal nerve (IX), vagus nerve (X) and the accessory nerve (XI). ● General somatic efferent (GSE): motor innervation to skeletal muscle. AFFERENT: ● general visceral afferent fibers (GVA): conduct sensory impulses (usually pain or reflex sensations) from the viscera, glands, and blood vessels to the central nervous system. ○ Facial nerve (VII), the glossopharyngeal nerve (IX) and the vagus nerve (X). ● Special somatic afferent (SSA): carry information from the special senses of vision, hearing and balance. ○ optic nerve (II) and the vestibulocochlear nerve (VIII). ● Special visceral afferent (SVA) : carry the special senses of smell (olfaction) and taste (gustation). ○ olfactory (I), facial nerve (VII), glossopharyngeal nerve (IX) and the vagus nerve (X). Optic nerve CN II Special somatic afferent transmits visual information from the retina to the brain fibers carrying information from the temporal visual field which cross in the optic chiasm briefly bend up into the contralateral optic nerve a lesion of the optic nerve close to the chiasm interrupts all the fibers from the ipsilateral eye and crossing fibers from the contralateral eye the optic nerve is NOT in the cavernous sinus (came up more than once) the optic foramen,transmits the optic nerve and ophthalmic artery (with accompanying sympathetic nerve fibers) into the orbital cavity. Oculomotor CNIII Somatic motor (general somatic efferent) supplies: levator palpebrae superioris muscle of the upper eyelid. Superior rectus, inferior oblique and inferior rectus Visceral motor (general visceral efferent) Parasympathetic innervation of the constrictor pupillae and ciliary muscles to change the shape of the lens for accommodation. *Loss of the ciliary ganglion will produce loss of the direct pupillary reflex and pupillary dilation The oculomotor nerves pass between the proximal portions of the posterior cerebral and superior cerebellar arteries Trochlear nerve CN IV Innervates the the superior oblique Paralysis results in extorsion of the ipsilateral eye, diplopia Head tilt away from the affected side to compensate Exits brainstem dorsally Trigeminal CNV The trigeminal nerve is composed of three large branches. ● ophthalmic (V1, sensory) ● maxillary (V2, sensory) ● mandibular (V3, motor and sensory) ● Innervation of the dura within the cranial vault is provided by the ophthalmic branch (V1) Trigeminal V3 branch of the trigeminal nerve supplies the muscles of mastication: - temporalis, masseter, medial and lateral pterygoids, mylohyoid, anterior belly of the digastric, tensor veli palatini, tensor tympani Abducens CN VI ● The abducens nerve emerges from the ventral surface of the brainstem between the pons and medulla, most medial ● Supplies the lateral rectus ● In the cavernous sinus it runs alongside the internal carotid artery. It then enters the orbit through the superior orbital fissure and innervates the lateral rectus muscle of the eye. Facial CN VII Branchial motor (special visceral efferent) frontalis, corrugator, obicularis occuli, nasalis, buccinator, obicularis oris, mentalis, platysma Visceral motor (general visceral efferent) Parasympathetic innervation of the lacrimal, submandibular, and sublingual glands, as well as mucous membranes of nasopharynx, hard and soft palate. Special sensory (special visceral afferent) Taste sensation from the anterior 2/3 of tongue; hard and soft palates. General sensory (general somatic afferent) General sensation from the skin of the concha of the auricle and from a small area behind the ear. nervus intermedius Branchial motor fibers (facial expression) constitute the largest portion of the facial nerve. The remaining three components, are bound in a distinct fascial sheath from the branchial motor fibers. Collectively these three components are referred to as the nervus intermedius. *An injury to the nervus intermedius would spare facial muscles Visceral motor (general visceral efferent) Parasympathetic lacrimal, submandibular, and sublingual glands, mucous membranes of nasopharynx, hard and soft palate. Special sensory (special visceral afferent) Taste anterior 2/3 of tongue; hard and soft palates. General sensory (general somatic afferent) General sensation from the skin Facial nerve Exits the skull at the stylomastoid foramen Gives off 3 branches before exiting the stylomastoid foramen greater superficial petrosal (lacrimation) nerve to the stapedius chorda tympani (taste, glands) A lesion distal to the greater petrosal (or geniculate ganglion) but proximal to the stapedius muscle would cause weakness in the muscles of facial expression, alter sublingual and submandibular function, and cause loss of taste to the anterior ⅔ of tongue, cause hyperacusis, SPARES lacrimation Geniculate Ganglion ● Contains special visceral afferent cell bodies (taste) and sensory fibers to the external auditory canal and tympanic membrane ● The motor and the parasympathetic portions of CN 7 pass through the GG without synapsing ● Zoster can reactivate in sensory ganglia. Causes facial paralysis, +/hearing loss/vertigo (spread to CN8). Rash seen on external acoustic meatus and lateral tongue (Ramsay Hunt syndrome type 2/herpes zoster oticus) sphenopalatine/pterygopalatine ganglion ● The pterygopalatine ganglion (Meckel's ganglion, nasal ganglion or sphenopalatine ganglion) is a parasympathetic ganglion found in the pterygopalatine fossa. ● It is one of four parasympathetic ganglia of the head and neck, the others being the submandibular ganglion, otic ganglion, and ciliary ganglion. Sensory root: derived from two sphenopalatine branches of the maxillary nerve their fibers, for the most part, pass directly into the palatine nerves; a few, however, enter the ganglion, constituting its sensory root. Parasympathetic root: derived from the nervus intermedius through the greater petrosal nerve. he preganglionic parasympathetic fibers from the greater petrosal branch of the facial nerve synapse with neurons whose postganglionic axons, vasodilator, and secretory fibers are distributed with the deep branches of the trigeminal nerve to the mucous membrane of the nose, soft palate, tonsils, uvula, roof of the mouth, upper lip and gums, and upper part of the pharynx. also sends postganglionic parasympathetic fibers to the lacrimal nerve (a branch of the Ophthalmic nerve, also part of the trigeminal nerve) via the zygomatic nerve, a branch of the maxillary nerve(from the trigeminal nerve), which then arrives at the lacrimal gland. The nasal glands are innervated with secretomotor from the greater petrosal nerve. The palatine glands are innervated by the nasopalatine,greater palatine nerve and lesser palatine nerves. The pharyngeal nerve innervates pharyngeal glands. These are all branches of maxillary nerve. Sympathetic root: sympathetic efferent (postganglionic) fibers from the superior cervical ganglion. These fibers, from the superior cervical ganglion, travel through the carotid plexus, and then through the deep petrosal nerve. sphenopalatine ganglion ● the preganglionic parasympathetic fibers from the greater petrosal branch of the facial nerve synapse with neurons whose postganglionic axons, vasodilator, and secretory fibers are distributed with the deep branches of the trigeminal nerve to the mucous membrane of the nose, soft palate, tonsils, uvula, roof of the mouth, upper lip and gums, and upper part of the pharynx. ● It also sends postganglionic parasympathetic fibers to the lacrimal nerve which then arrives at the lacrimal gland. vestibulocochlear nerve CN VIII 2 functions: ● ● Innervation to the cochlea for hearing ○ cochlear nerve relays with the first order sensory cells in the spiral ganglion, which is in the base of the spiral lamina. ○ terminates at the dorsal and ventral cochlear nuclei Innervation to the vestibule for acceleration sense ○ The vestibular ganglion (scarpa) gives Enters the brainstem at the cerebellopontine angle cochlear nuclei ● Cochlear nuclei are the most distal structures along the auditory pathway that when lesioned would still result in a unilateral sensorineural hearing loss ● Lesions to auditory pathways beyond the cochlear nuclei would cause some degree of bilateral deficit Glossopharyngeal CN IX Branchial motor (special visceral efferent) – supplies the stylopharyngeus muscle. General visceral efferent – derived from the Inf. salivatory nucleus, provides parasympathetic innervation of the parotid gland via the otic ganglion General visceral afferent– carries visceral sensory information from the carotid sinus and carotid body. Special visceral afferent – provides taste sensation from the posterior one-third of the tongue, including circumvallate papillae. General somatic afferent– provides general sensory information from inner surface of the tympanic membrane, upper pharynx, and the posterior one-third Exits at the jugular foramen Vagus CN X The vagus nerve is the tenth cranial nerve and provides the bulk of the parasympathetic input to the gastrointestinal system and to the heart. It is a mixed sensory/motor/parasympathetic nerve. Motor (efferent) fibers project from: nucleus ambiguus - branchial motor fibers > pharynx, larynx dorsal motor vagal nucleus - parasympathetic motor fibres (visceral efferent) > heart, lungs, GI tract Sensory (afferent) fibers project to: nucleus solitarius - visceral sensory (taste) spinal trigeminal nucleus - general sensory (cutaneous) Vagus CN X Components Function Central connection Cell bodies Peripheral distribution Special visceral efferent Swallowing, phonation Nucleus ambiguus Nucleus ambiguus Pharyngeal branches, superior and inferior laryngeal nerves General visceral efferent Involuntary muscle and gland control Dorsal motor nucleus X Dorsal motor nucleus X Cardiac, pulmonary, esophageal, gastric, celiac plexuses, and muscles, and glands of the digestive tract General visceral afferent Visceral sensibility Nucleus tractus solitarius Inferior ganglion X Cervical, thoracic, abdominal fibers, and carotid and aortic bodies Special visceral afferent Taste Nucleus tractus solitarius Inferior ganglion X Branches to epiglottis and taste buds General somatic afferent Cutaneous sensibility spinal trigeminal nucleus Superior ganglion X Auricular branch to external ear, meatus, and tympanic membrane Baroreceptor reflex helps regulate blood pressure by detecting changes via baroreceptors mostly in the carotid sinus and aortic arch baroreceptors are activated by an increased blood pressure, decreasing the activity of the sympathetic branch of the autonomic nervous system, leading to a relative decrease in blood pressure. Likewise, low blood pressure activates baroreceptors less and causes an increase in sympathetic tone via "disinhibition" information from the carotid sinus travels via the glossopharyngeal nerve, that from the aortic arch is carried by the vagus all baroreceptor afferents synapse in the nucleus tractus solitarius which then projects to the ventrolateral medulla hypoglossal CN XII carries axons of general somatic efferent (GSE) providing motor control of the extrinsic muscles of the tongue; genioglossus, hyoglossus, styloglossus, and the intrinsic muscles of the tongue does not supply the palatoglossus (vagus) Cavernous sinus The cavernous sinus transmits multiple cranial nerves to the superior orbital fissure and foramen ovale. These are: In the lateral wall from superior to inferior: oculomotor nerve trochlear nerve trigeminal nerve- ophthalmic (V1) and maxillary (V2) divisions. abducens is in the carotid sheath RANDOM FACTS foramens facial = stylomastoid foramen vagus, glossopharyngeal, accessory = jugular all of the cranial nerves categorized as general somatic efferent (III, IV, VI, XII) exit the brainstem medially Eye Movements Brainstem high yield questions only, from last 8 years of RITE exams Wallenberg Syndrome dorsolateral medullary syndrome ischemia in the distribution of the posterior inferior cerebellar artery (PICA). involves: vestibular nucleus (nystagmus/vertigo) inferior cerebellar peduncle (ipsilateral ataxia) spinal trigeminal nucleus (facial numbness), spinothalamic tract (pain/temp contralateral body), descending ocular sympathetic pathways (Horners?), nucleus ambiguus (dysphagia, hoarseness, gag). Ipsilateral limb ataxia in this case is due to involvement of the left inferior cerebellar peduncle. Ocular lateropulsion in a Wallenberg syndrome is likely due to a lesion of the olivocerebellar climbing fibers that gives rise to functional disinhibition of cerebellar cortex and to increased inhibition of the deep cerebellar nuclei. Pontine stroke Pt presents with: right arm and leg weakness with fine touch deficits, left facial paresis, diplopia on left lateral gaze Left (medial) pontine infarct occlusion of paramedian branch of basilar artery The patient has a crossed paresis, with right arm and leg weakness - corticospinal tract left facial paresis - left facial nucleus? Diplopia, with left lateral gaze - left abducens nucleus Sensory deficits of fine touch on the right arm, trunk, and leg - left medial lemniscus Weber syndrome Weber syndrome is a midbrain stroke syndrome (cerebral peduncle) involves the fascicles of the oculomotor nerve resulting in an ipsilateral CN III palsy contralateral hemiparesis. Decerebrate posturing A lesion below the level of the red nucleus (rostral midbrain) but above the level of the vestibulospinal and reticulospinal nuclei will result in decerebrate posture(upper extremity in pronation and extension and the lower extremity in extension). The reason for this is that the red nucleus (and rubrospinal tract) output reinforces antigravity flexion of the upper extremity. When its output is eliminated then the unregulated reticulospinal and vestibulospinal tracts reinforce extension tone of both upper and lower extremities Parinaud syndrome (dorsal midbrain syndrome) The clinical features are: upgaze paresis nystagmus on attempted convergence eyelid retraction pseudo-Argyll-Robertson pupils: large pupils with sluggish reaction to light A lesion producing these findings occurs in the midbrain tectal region. It often occurs by extra-axial compression on the quadrigeminal plate (particularly the superior colliculi). Pineal region masses as well as obstructive hydrocephalus may also cause the syndrome. Video: http://www.kaltura.com/index.php/extwidget/preview/partner_id/797802/uiconf_id/27472092/entry_id/0_94uxo64 p/embed/auto? Millard-Gubler syndrome, ventral pontine syndrome A unilateral lesion of the ventrocaudal pons Symptoms include: 1. Contralateral hemiplegia (sparing the face) due to pyramidal tract involvement 2. Ipsilateral lateral rectus palsy with diplopia that is accentuated when the patient looks toward the lesion, due to cranial nerve VI involvement. 3. Ipsilateral peripheral facial paresis, due to cranial nerve VII involvement. Palatal myoclonus The patient with multiple sclerosis and "rhythmic clicking" in her ears has palatal myoclonus. A lesion of the pathway connecting the red nucleus, central tegmental tract, inferior olivary nucleus, and dentate nucleus results in palatal myoclonus. Guillain-Mollaret triangle One and a half syndrome Ipsilateral eye has no horizontal movements and the contralateral eye is only able to abduct. The clinical findings are a combination of a left intranuclear ophthalmoplegia (which prevents the left eye from adducting on rightward gaze with end-gaze nystagmus of the abducting right eye) and a left abducens nuclear palsy (which produces an ipsilateral gaze palsy preventing the patient from looking left). The only horizontal eye movement still possible, then, is abduction of the right eye on rightward gaze. This lesion must involve the left medial longitudinal fasciculus and left abducens nucleus. MLF lesion right MLF lesion - can abduct the left eye on attempted gaze to the left but the right eye cannot be adducted - nystagmus in the left (abducting eye) ocular tilt reaction - skew deviation ipsilateral ocular torsion ipsilateral head tilt (torticollis) caused by a peripheral or brainstem lesion affecting otolithic pathways nucleus ambiguus -source of branchial outflow to laryngeal muscles - contains motor neurons that supply striated muscles of the palate, pharynx, and larynx - disruption of this nucleus will impair phonation