Faculty of Dental Medicine and Surgery Sem 4 Cranial Nerves Dr. Abbas Garib Alla
Cranial Nerves I through XII
FUNCTIPONAL CLSSIFICATION OF THE CN parasympathetic nerves 1973 PHARYNGEAL ARCHES nerves 1975 Small Ships Make Money, But My Brother Says Big Boats Make More 3
FUNCTIONAL COMPONENTS 4 (GENERAL)+3(SPECIAL) THE GENERAL 2-SOMATIC(BODY WALL) GSA= General sensation i.e transmit exteroceptive and proprioceptive impulses from the body wall GSE= Motor to striated muscle of non-pharyngeal origin 2-AUTONOMIC(VISCERA)para-sympathetic GVA= General sensation from the viscera+b.v+glands transmit interoceptive impulses to the visceral sensory nuclei GVE= motor to the visceral musclesand relayed in parasympathetic ganglions. The postganglionic fibers supply cardiac muscles,smooth muscles and glands 3/24/2019 4
special SSA=Vision+Hearing& equilibrium SVA=Taste +Smell SVE=striated muscles of pharyngeal origin[1975] 3/24/2019 5
1973 Sensory GVA GSA (pain, touch, thermal etc) SSA (TV) SVA (food) motor GVE SVE(1975) GSE Small Ships Make Money, But My Brother Says Big Boats Make More So4 Lr6 O3
MOTOR: 2 Orders. UMN-cortico- nuclear(motor nucleus) bilateral LMN- motor nucleas to the muscle
SENSORY 3 Orders: Area---P.F------Sensory Ganglion-1 st Sensory Nucleus-2 nd cross tothalamus-3 rd --sensory cortex
Olfactory Nerve I Sense of smell SVA Pathway: fibers-bulb-tact stria to cortex bypass thalamus Damage causes impaired sense of smell (anosmia
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Anosmia: diminished sense of smell Transient (non-neural): upper respiratory tract infection Fracture of cribriform plate Frontal lobe tumor
Optic Nerve II Provides vision SSA Damage causes blindness in visual field
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Oculomotor Nerve III Somatic (GSE) and Autonomic motor function (GVE) Somatic:-Eye movement (Superior, inferior, medial rectus muscles and inferior oblique muscle), opening of eyelid (levator palpebrae superioris), Ophalmoplesia drooping eyelid (ptosis) diplopia Parasympathetic:- constriction of pupil (circular muscle), focusing (ciliary muscle and accomodation) dilated pupil and difficulty in focusing
Functional component GVE Nucleus Function Area Edinger Westphal nucleus Constriction pupil Accommodation (focus) circular muscle puplae iris Ciliary muscle iris GSE Somatic nucleus Eye ball movements Eye ball O3
External strabismus( lateral squint)
Trochlear Nerve IV GSE Eye movement (superior oblique muscle) Damage causes double vision and inability to rotate eye inferolaterally
Abducens Nerve VI (GSE) Provides eye movement (lateral rectus m.) Damage results in inability to rotate eye laterally and at rest eye rotates medially
Internal strabismus ( Medial squint)
Trigeminal Nerve V GSA SVE Ophthalmic branch sensations from nasal cavity, skin of forehead, upper eyelid, eyebrow, nose Maxillary branch sensations from lower eyelid, upper lips and gums, teeth of the maxilla, cheek, nose, palate, pharynx Mandibular branch sensations from teeth of the mandible, lower gums and lips,, tongue. Motor function of temporalis and masseter muscles, palate. Damage produces loss of sensation and impaired chewing
Clinical testing: facial sensation corresponding to areas innervated by V1, V2, &V3, masticatory strength, jaw jerk reflex, corneal reflex Trigeminal neuralgia (tic doloureux) Ophthalmic herpes zoster ( shingles )
Facial Nerve VII Somatic Motor - facial expressions SVE, SVA, GVE, GSA, GVA Autonomic Motor - salivary and lacrimal glands, mucous membranes of nasal and palatine mucosa Special Sensory - taste on anterior 2/3 s of tongue Damage facialparalysis Bell's palsy and disturbed sense of taste (no sweet and salty)
Branches of Facial Nerve Clinical test: Test anterior 2/3 s of tongue with substances such as sugar, salt, vinegar, and quinine; test response of tear glands to ammonia fumes; test motor functions by asking subject to close eyes, smile, whistle, frown, raise eyebrows, etc.
Complicated! Motor: muscles of facial expression & some others Parasympathetic: stimulation of lacrimal, submandibular, sublingual glands, nasal/palatal mucosa Special sense: taste to anterior 2/3 of tongue and palate Somatic sense: small part of ear area
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Complicated! Motor: muscles of facial expression & some others Parasympathetic: stimulation of lacrimal, submandibular, sublingual glands, nasal/palatal mucosa Special sense: taste to anterior 2/3 of tongue and palate Somatic sense: small part of ear area
Clinical Features of Facial N. paralysis 1. Facial asymmetry. 2. Eyebrow droop. 3. Loss of forehead and nasolabial folds. 4. Drooping of corner of the mouth. 5. Uncontrolled tearing. 6. Inability to close eyes. 7. Lips cannot be held tightly together. 8. Facial muscle atrophy (late).
Vestibulocochlear Nerve VIII Special Sensory SSA Provides hearing (cochlear branch) and sense of balance (vestibular branch) Damage produces cochlear deafness, Tinitus Vestibular dizziness, nausea, loss of balance and nystagmus
Glossopharyngeal Nerve IX Somatic motor Swallowing and voice production via pharyngeal muscle SVE, SVA, GVE, GSA, GVA Autonomic motor - salivation, gagging, control of BP and respiration Sensations from posterior 1/3 of tongue including taste Sensations from baroreceptors and chemoreceptors
Complicaions Damage results in loss of bitter and sour taste and impaired swallowing, blood pressure anomalies (with CN X). motor to stylopharyngeus, parasympathetic outflow to parotid gland, sensation from carotid body & sinus, taste from posterior 1/3 of tongue, somatic sensation from posterior 1/3 of tongue and pharynx Tested by gag reflex
Vagus Nerve X SVE, SVA, GVE, GSA, GVA Sensations from skin at back of ear, external acoustic meatus, part of tympanic membrane, larynx, trachea, espophagus, thoracic and abdominal viscera Motor to bararoceptors and chemoreceptors Special sensory taste from epiglottis and pharynx Somatic motor Swallowing and voice production via pharyngeal muscles Autonomic motor smooth muscle of abdominal viscera, visceral glands secretions, relaxation of airways, and normal or decreased heart rate. are cut
Complications Damage causes hoarseness or loss of voice, impaired swallowing, GI dysfunction, blood pressure anomalies (with CN IX), fatal if both motor to most all muscles of pharynx & palate; parasympathetic outflow to and visceral sensation from cervical, thoracic, & abdominal viscera; somatic sensation from small areas Tested by symmetry of palatal elevation; recurrent laryngeal branch commonly injured with effects on glottis
Accessory Nerve XI Cranial SVE (X) Spinal GSE Swallowing, head, neck and shoulder movement via trapezius and sternocleidomastoid and pharyngeal muscles Damage causes impaired head, neck, shoulder movement Stiffneck
Hypoglossal Nerve XII GSE GSE Tongue movements for speech, food manipulation and swallowing If both are damaged can t protrude tongue
Complications Lower Motor Neuron Lesion (LMNL) Peripheral to brain stem Ipsilateral atrophy & deviation Upper Motor Neuron Lesion (UMNL) Supranuclear (e.g., cortex) Contralateral atrophy & deviation
Cranial Nerve Disorders Trigeminal neuralgia (tic douloureux) recurring episodes of intense stabbing pain in trigeminal nerve area (near mouth or nose) pain triggered by touch, drinking, washing face treatment may require cutting nerve Bell s palsy disorder of facial nerve causes paralysis of facial muscles on one side may appear abruptly with full recovery within 3-5 weeks