Cranial Nerves Flashcards
CN I
Olfactory N; Special Sensory; cribiform plate of ethmoid bone; Tract and bulb originate from telencephalon; olfactory receptor neurons originate from nasal mucosa and course through cribiform foramina and synapse with olfactory bulb; can regenerate some; odor molecules bind to olfactory receptor neurons (chemoreception)–> AP propagated to olfactory bulb–> olfactory tract –> brain
Dental professions at risk for exposure to potential olfactory toxin (methyl methacrylate) causing damage to olfactory receptor neurons;
CN II
Optic N; Special Sensory; optic canal; light hits deep layers of retina (fovea centralis)–> medial fibers decussate while lateral fibers remain ipsilateral—> 90% LGN in thalamus
optic radiation to occipital lobe [inferior and superior loop]
pupillary light reflex; 10% to superior colliculus–> synapse with pretectal nuclei (interneuron) at level of superior colliculus–> synapse with Edinger Westphal nucleus in midbrain (CN III)–> constrict pupil
Bitemporal Hemianopia- lateral vision affected, tunnel vision (oftens optic chiasm, affecting nerve fibers that decussate) caused by pituitary adenoma, ICA aneurysm, swelling of ACA
CNIII
Oculomotor N; Motor; superior orbital fissure; midbrain; oculomotor nuclei (originates at level of superior colliculus) controls LPS and extraocular muscles; Edinger Westphal- supplies PS via ciliary ganglion; controls sphincter pupillae and ciliary muscles ; Superior branch (smallest, passes medially over optic N, supplies SR and LPS) Inferior branch (3 parts; first passes under CN II--> supplies MR; 2nd straight into IR; 3rd runs between IR and Lateralis--> inferior oblique-->branch to ciliary ganglion--> sphincter pupillae and ciliary muscles)
Pupillary light reflex; superior orbital fissure (S. Opthalmic V, CN V1 (frontal, nasocillary, lacrimal), CN IV, VI; goes in cavernous sinus ( cavernous sinus thrombosis)
Third N Palsy caused by aneurysm in A supplying brain or inadequate blood flow due to diabetes, high bp, other disorders affecting bp,; affected eye turns outward while other looks ahead; eyelid droops, pupil may be dilated and not constricted in response to light [ post. communicating A]
CN IV
Trochlear N; Motor; superior orbital fissure; midbrain; smallest nerve (axons) largest intracranial length; only CN that exits from dorsal ; nuclei are contralateral to target muscle but nerve itself is ipsilateral; general somatic efferent innervation to the contralateral SO muscle (ends up ipsilateral)- look down and out; goes in subarachnoid space–> pierces dura–> cavernous sinus–> SOF
CN V-1
Opthalmic N; sensory; superior orbital fissure; pons
Nasociliary nerve supplies mucous membrane of the nose as well as the tip of the nose.
Lacrimal nerve provides sensory innervation to the lacrimal gland, inside of eyelids, skin covering the eye (conjunctiva), and lateral portion of upper eyelid.
Frontal Nerve is the largest branch of V1 and provides sensation to the skin of the forehead, mucosa of the frontal sinus, and the majority of the skin on the upper eyelid. Divides into the Supratrochlear and Supraorbital nerves.
TN (Trigeminal Neuralgia): Affects all areas the trigeminal nerve branches innervate–lips, eyes, nose, scalp, forehead, upper jaw, and lower jaw
Contact with a normal blood vessel (aging, multiple sclerosis, or similar disorder that diminishes the myelin sheath)
extreme, sporadic, and shock-like facial pain
Women more than men
Rarely affects people under 50
CN V-2
Maxillary N; sensory; foramen Rotundum; pons;
In the cranium: Middle meningeal nerve in the meninges
From the pterygopalatine fossa: Zygomatic nerve, Nasopalatine nerve, Posterior superior alveolar nerve-PSA
Greater and lesser palatine nerves, Pharyngeal nerve
In the infraorbital canal: Middle superior alveolar nerve-MSA,
Anterior superior alveolar nerve-ASA, Infraorbital nerve
On the face: Inferior palpebral nerve, Superior labial nerve
transmission of sensory fibers to the maxillary teeth, gingiva and palate, upper lip, the skin between the palpebral fissure (middle of the eye) and the mouth, the nasal cavity, the mucous membranes and sinuses, lower eyelid & its conjunctiva
CN V-3
Mandibular N; sensory/ motor; Foramen Ovale; pons; Auriculotemporal nerve (lesser petrosal), Long Buccal Nerve, Masseteric branch, Pterygoid branches, Deep Temporal branch, Lingual Nerve (Chorda tympani), Inferior Alveolar, Nerve to mylohyoid, Mandibular foramen, Inferior dental nerves, Exits mental foramen, Mental nerve
Provides general sensory
Mucosa
Anterior ⅔ of the tongue
Floor of mouth
Chorda tympani - branch of Facial Nerve (CN VII)
Runs with the lingual nerve branch of V3 to provide taste to anterior ⅔ of tongue.
Innervates submandibular, sublingual, and submental glands.
Lesser Petrosal- CN IX- parotid gland
Innervates muscles of mastication, Anterior digastric, mylohyoid, Tensor tympani, and Tensor veli palatini
Inferior Alveolar N Damage: At risk from many surgeries and procedures in dentistry
implants, root canals, third molar extractions (75%), root canal therapy chemicals, and local anesthesia; Sensory paralysis: lower lip on affected side, mental region, gingivae; possible persistent pain and/or pain from occlusion
Paraesthesia: tingling or pricking
Impairment in speech, chewing, sleep, work/socializing, psychological well being
Dysesthesia: pain, burning, tingling (sometimes with no touch at all)
If this develops, it will usually become a chronic problem
CN VI
Abducens N; motor; Superior Orbital fissure; somatic motor efferent N; nucleus in pons; axon exits brainstem at junction of pons/medulla–> subarachnoid space–> cavernous sinus (first that shows symptoms due to thrombosis) –> SOF; innervates ipsilateral LR (abduction of eye);
Abducens N palsy- injury to nerve causes diplopia (double vision) due to MR working without opposition; patients correct this by turning head sideways so both eyes looking sideways
CN VII
Facial N; Motor/Sensory; Internal Acoustic Meatus–> facial canal; pons; muscles of facial expression, posterior digastric, stylohyoid and stapedius muscles; taste anterior 2/3 ; submandibular, sublingual, nasal, palatine, lacrimal, and pharyngeal glands ; gives rise to Greater Petrosal, Nerve to Stapedius and Chorda Tympani
Facial canal–> stylomatoid foramen; gives rise to posterior Auricular (muscles near ear, posterior digastric, stylohyoid) and parotid plexus ( Temporal [innervates frontalis, orbicularis oclui, and corrugator supercilii] , Zygomatic [orbicularis oris] , Buccal [orbicularis oris, buccinator, zygomaticus] , Marginal Mandibular [mentalis] , Cervical [platysma] )
Bell’s Palsy- linked with Herpes cold sore virus, not permanent; sudden weakness or paralysis on one side of face (droop), excessive tearing or dry eye, loss of ability to taste, pain in or behind ear, numbness in affected side of face, increased sensitivity to sound; can be caused by inferior alveolar N block (numbing of parotid gland)
CN VIII
Vestibulocochlear N; Special sensory; Internal Acoustic Meatus; pons; conveys impulses from inner ear; carries info related to position/ movement and auditory info
Meniere’s disease- idiopathic endolympatic hydrops caused by abnormal fluid volume in inner ear due to excess production or inadequate absorption; symptoms (vertigo-spinning; hearing loss; tinnitus- roar/buzz/ring in ear, sensation of fullness in affected ear ; lasts 20 min to 4 hours
CN IX
Glossopharyngeal N; Motor/ Sensory; Jugular Foramen; medulla; goes to superior (somatosensory) or inferior (viscerosensory) ganglion; afferent portion of gag reflex;
Tympanic N- branches off inferior ganglion and enters tympanic cavity via tympanic canaliculus (tympanic plexus is genetic somatosensory innervation to tympanic cavity, eustachian tube and mastoid air cells, Lesser petrosal N–> lesser petrosal canal and synapses with otic ganglion–> innervates parotid, buccal and inferior labial glands by hitchhiking with auriculotemporal N of V3)
carotid branch- general viscerosensory of carotid sinus (baroreceptors) and carotid body (chemoreceptors)
pharyngeal branch- general somatosensory fibers from naso and oropharynx form a plexus with motor fibers from CN X [Gag reflex]
muscular branch- branchiomotor fibers innervate stylopharyngeus (elevates pharynx and larynx)
Tonsilar branch- general somatosensory from palatine tonsils and mucosa of oropharynx
Lingual branch- general somatosensory and special viscerosensory (taste) from posterior 1/3
Glossopharyngeal neuralgia ( cause- blood vessel found compressing N causes pain on one side of throat, faint after swallowing, last several days or weeks)
CN X
Vagus N; Motor/ Sensory; Jugular foramen; medulla; laryngeal muscles, pharyngeal muscles (except stylopharyngeus), palatoglossus, levator veli palatini , uvular, visceral motor (thoracoabdominal organs- heart, trachea, bronchial tree, GI tract to midgut , accessory GI glands (liver, gallbladder, pancreas) special sensory (pressure receptors on aortic arch and chemoreceptors on aortic body), external ear/acoustic meatus, part of oro/most of laryngopharynx mucosa, posterior dura
Gag reflex- motor via nucleus ambiguous- pharyngeal and palatal muscles contract
Auricular branch- general somatosensory fibers from external ear (auricle, external acoustic meatus, parts of lateral side of tympanic membrane) branches inside skull
Pharyngeal branch- principal motor nerve of pharyngeal muscles except stylopharyngeus; passes across ICA and fans out with fibers from glossopharngeal, Sympathetic, external laryngeal to form pharyngeal plexus
carotid branch- carotid body of ICA sometimes?
superior laryngeal branch- combines with sympathetic branch from Superior cervical ganglion and divides into internal (general sensory from mucosa of laryngopharyx, larynx and root of tongue so above vocal cords) and external laryngeal (PS motor innervation to cricothyroid)
recurrent laryngeal- right side behind subclavian A left side behind superior to aortic arch and ascends between trachea and esophagus; motor innervation to laryngeal muscles and viscerosensory to laryngeal mucosa below vocal cords (unilateral lesion causes hoarseness)
parasympathetic and general viscerosensory fibers from the cardiac, pulmonary, esophageal, celiac, renal, hepatic, and gastric plexuses.
CN XI
Spinal Accessory N; motor; comes off below level of skull –> foramen magnum–> Jugular foramen–> medulla; neuronal cell bodies arise from “lateral horn”; innervates trapezius and SCM (in investing fascia)
Accessory N Disorder or Spinal Accessory N Palsy- diminished or absent function of SCM or upper part of trapezius
Spasmodic Torticollis- involuntary movements of the head resulting from muscle spasm in head/neck
CN XII
Hypoglossal N; motor; hypoglossal canal; medulla; descends anteriorly through carotid triangle; innervates intrinsic (Superior longitudinal, inferior longitudinal, transverse, vertical) and extrinsic (Genioglossus, hyoglossus, styloglossus) muscle of tongue except palatoglossus (CN X)
Chordae Tympani
CN VII; petrotympanic fissure; synapse with submandibular ganglion;Runs with the lingual nerve branch of V3; taste of anterior 2/3, submandibular gland, sublingual glands, submental glands.
