Cranial nerves Olfactory nerve - PowerPoint Presentation

1. Cranial nerves

2. Olfactory nerveComponent: sensory Function: smellExamination:Ask whether the patient tastes and smells his food normally.N.B as the food passes through the buccal cavity, its volatile part is exhaled in to the nasal cavity where it’s smelled, and because olfaction is more acute than tast in determining the flavour of food, a patient having a common cold complains loss of tastTest each nostril separately, ask the pt to sniff several common non irritant odorants (coffe, orange, lemon) and differentiate between them.Electro-olfactory grama recording of electrical potential changesd etected by an electrode placed on the surface of the olfactory mucosa as the mucosa is subjected to an odorous stimulus.

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5. Abnormalities of smell sensationAnosmia: loss of sens of smellHyposmia: diminished sense of smell dysosmia: distorted sense of smellOptic nerveComponent: sensory Function: visionExamination:A- visual acuityThis is the degree of perception of the details and contour of objects by the eyeDetermined by finding the minimum separable

6. Snellen’s and landolt’s chartDepend on reading letters drawn in black on a well illuminated backgroundThe chart is placed at the level of the pt eyes at a distance of 20 feet or 6 meter Each eye is tested separatelyThe chart consists of 7 rows of lettersThe spaces between the broken ends of the letters at each row corresponds to a visual angle of one minuteat acertain distance from the eyeThe upper most letters can be read by the normal eye at 60 meter distanceFollowed by (36,24, 18,12,9,6)

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9. B-Visual fieldIs the maximal area of space that can be seen by the eyewhen a person fixes his gaze on one point Confrontation testPerimeterThe process of charting the monocular field of vision The peripheral field of each eye extends upto about 100o on the temporal side; about 65o downwards (it is limited by the cheek); 55–60o on the nasal side (limited by the nose); and about 50o upwards where it is limited by the brow.C- fundus examination OphthalmoscopeThe optic disc and retinal blood vessels are examinedLesion Visual field loss

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13. Oculomotor nerveComponent:Somatic motor to external ocular muscles ( sup rectus, inferior rectus, medial rectus and inf oblique)Eye led muscle elevator pupilary muscleParasympathetic toConstrictor pupilary muscleCiliary muscle : accomodation of the eye to near visionExamination Eye appearanceEye pupilShape, size and presence of any irregularitiesReaction to light (direct response, consensual response)

14. Oculomotor nerve accomodation- Eye movements and conjugate movements

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16. Pupillary light reflexWhen one eye is exposed to light, miosis occurs in that eye (direct reflex ) and in the other eye (consensual reflex)Afferent: optic nerveEffrent: 3rd cranial nerveFunction: protect the retina of the stimulated eye from excess lightTesting this reflex is important clinically in:Diagnosis of certain nervous diseasesLocalization of the site of lesion in the visual pathwayDetermination of the depth of anasthesiaAccomodation reflex (near response)On looking at near object nearer than 6 meterConvergence of both eyesBilateral miosisIncreasing the power of the lensAfferent: optic nerveEfferent: oculomotor nerve

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20. Trochlear nerveComponent: motorFunction : supply superior oblique muscleExamination : depression of medially deviated eyeLesionDiplopia especially when looking downDifficulty in looking downward and inward Eye drifts upward relative to the normal eye

21. Abducent nerveComponent: motorFunction: supply the lateral rectus muscleExamination: Eye movement laterallyLesion:

22. Trigeminal nerveComponent: sensory and motorTrigeminal nerve divided in three branchesOphthalmic branch( upper part of the face, forehead, ant part of the scalp, cornea, conjunctiva and the nasal mucosa).Maxillary branchMiddle part of the face, hard palate, upper teeth and gumsMandibular branchLower part of the face, lower teeth and gums, ant two thirds of the tongueMotor fibers to the muscles of musticationFunction A- sensory Transmits sensations ( pain, temprature, touch) from the face, scalp, teeth, lips, eye ball, noseGeneral sensory from the ant 2/3 of the tongueProprioceptive sensations from muscles of mustications

23. Trigeminal nerveB- Motor To muscles of musticationExamination of the trigeminal nerveSensory function testTest pain, temprature and touch sensation over the distribution of the trigeminal nerveMotor function testAsk the patient to bite firmly and the prominence of the masseter and temporalis muscles is observes and palpatedReflex function testCorneal reflexAfferent : trigeminal nerveReflex: touching the cornea of one eye by a piece of cotton causes contraction of the orbicularis oculi on both sides resulting in bilateral blinkingEfferent: facial nerveThis reflex is protective to the corneaThis test : important to check the integrity of the trigeminal nerveJaw reflexAsk the pt to relax the jaw, place finger on the chin and tap with hummer

24. Trigeminal nerveAfferent and efferent : mandibular branch of the trigeminal nerveReflex lost in case of trigeminal nerve lesion

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27. OSPE-I Aim: To test the 5th cranial nerve in the subject provided. Procedural steps: Page 282 Checklist: 1. Makes the subject sit on a stool and explains the procedure. (Y/N) 2. Asks the subject to look at a distance, and touches his/her conjunctiva with a wisp of cotton, and notes the response. (Y/N) 3. Tests the sensations of touch and pain with a wisp of cotton and a pin on identical points on the two sides of the face. (Y/N) 4. Asks the subject to clench his/her teeth. Watches and feels the masseter and temporalis muscles contracting. (Y/N) 5. Asks the subject to open his/her mouth and move the mandible from side to side Then tests the mandibular reflex. (Y/N)

28. Facial nerveCorticobulbar tractFacial nerve nucleus in the ponsIs divided in to 2 partsUpper part receive signals from the corticobulbar tracts of both sidesLower part receive signals from the opposite tract only

29. Facial nerveComponent: Sensory: taste sensation from the ant 2/3 of the tongue proprioceptive sensation from face and scalpSomatic motor functionMuscles of facial expressions (orbicularis oculi, buccinator, orbicularis oris and frontalis muscle)Swallowing muscle (stylohyoid and post belly of digastric)Stapeduis muscl of the middle ear (attenuation reflex)parasympatheticSecretory to submandibular, sublingual salivary glands and lacrimal glandsExamination Sensory functionTest the taste sensation in the ant 2/3 of the tongueAsk the pt to protrude his tongue and apply salt or sugar to the ant 2/3

30. Facial nerveMotor functionTest for orbicularis oculi muscleAsk the pt to close his eyes while the examiner attempts to open them- Test for buccinatorAsk the pt to blow the cheeks while the examiner presses cheeksTest for orbicularis orisAsk the pt to whistle or show his teethTest for frontalisAk the pt to look upwards to wrinkles

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32. Facial nerve lesionsUpper motor neuron lesionUnilateral lesionContralateral Paresis of the muscles of the lower halfe of the faceDropping of the angle of the mouth on the affected sideDeviation of the angle of the mouth toward the healthy side on smilingBilateral lesionBilateral Paralysis of the lower and upper muscles

33. Facial nerve lesionsLower motor neuron lesionIpsilateral paralysis and wasting of the facial muscles of the upper and lower halfes of the face(the pt unable to close his eyes- loses the wrinkles of the forhead and deviation of the mouth toward the healthy side)Unilateral loss of taste sensation in the ant 2/3 of the tongue

34. OSPE-II Aim: To test the 7th cranial nerve in the subject provided. Procedural steps; Page 283 Checklist: 1. Explains the procedure to the subject. Looks for facial symmetry, furrows on the forehead, and the width of the palpebral fissure. (Y/N) 2. Asks the subject to look up and wrinkle his/her forehead, and then to shut his/her eyes as tightly as possible against the examiner’s resistance. (Y/N) 3. Asks the subject to show his/her upper teeth and to smile. (Y/N) 4. Asks the subject to inflate his/her mouth with air and to blow out his/her cheeks. Then taps his/her cheeks, on either side with his/her finger, to see if air escapes from the angle of the mouth.(Y/N) 5. Asks the subject to depress his/her lower lip. (Y/N)

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36. Accessory nerveComponent:motor toSternomastoid muscle : head rotationTrapezius muscle: shoulder elevationExamination Ask the pt to move his head against resistanceAsking the pt to elevate his shoulder against resistance

37. OSPE-III Aim: To test the 11th cranial nerve of the subject provided. Procedural steps: page 285 Checklist: 1. Asks the subject to sit comfortably and explains the procedure. (Y/N) 2. Stands behind the subject and places his/her hands on his/her shoulders. Then asks him/her to shrug his/her shoulders against his/her resistance. (Y/N) 3. Places his/her hand on the right side of the subjects face and asks him/her to rotate his/ her head to the opposite side. Watches the left sternomastoid. (Y/N) 4. Repeats the procedure on the left side and asks him/her to rotae his/her head to the left, and watches the right sternomastoid muscle. (Y/N) 5. Places his/her hand on the subject’s forehead and asks him/her to bend his/her head forwards against resistance. (Y/N)

38. Hypoglossal nerveComponent: motor toMuscles of the throat and tongueFunction control tongue movementControl intrinsic and extrinsic muscles of the tongueEating, sucking and chewing reflexesExaminationLesion

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40. OSPE-IV Aim: To test the 12th cranial nerve in the subject provides. Procedural steps: page 285 Checklist: 1. Explains the procedure to the subject (Y/N) 2. Asks the subject to push out his/her tongue as far as possible, Then inspects its position, evidence of wasting and fasciculation. (Y/N) 3. Asks the subject to move his/her tongue from side to side over the lips and against the walls of the cheeks. (Y/N)Places his/her finger over the subject’s cheek and asks him/her to push against it. Repeats on the opposite side. (Y/N). 5. Asks the subject to touch the tongue to the palate, and then to depress it into the floor of the mouth. (Y/N)

41. Glossopharyngeal nerveComponent: sensory and parasympatheticFunction: Sensory: - special sensory: taste sensation from the post 1/3 of the tongue - somatic sensory: proprioception for swallowing from throat muscles(soft palate and palatal arch) and middle earGeneral sensation from the post 1/3 of the tongue and mucous membrane of the pharynx - visceral sensory: blood pressure receptors from carotid sinusMotor:- swallowing as it supplies pharyngeal muscles (staylopharyngeus and upper pharyngeal constrictor fibers)Parasympathetic: - secretory to parotid glandExamination test the sensation of taste over the posterior third of the tongue.

42. Glossopharyngeal nerveExamination of the gag reflexEach side of the pharynx is touched lightly with a wooden spatula. The response is constriction of the pharynx. Afferent: 9th nerveEfferent: 10th nerve Centre : medullaA soft touch is applied on the soft palate; the response is elevation of the soft palate. The reflex arc is the same as in the gag reflex Lesion Loss of general and taste sensation from the post 1/3 of the tongueAbsence of gag reflex and difficulty in swallowingDecreased secretion of salivaOrthostatic hypotension

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44. Vagus nerveComponent: sensory, motor and parasympatheticFunctionA- sensory: heart, lung, digestive tract and vasosensory areasSomatic sensory supply external auditory meatus and part of the ear. visceral sensory supply pharynx, larynx, trachea, and thoracic and abdominal viscera. Chemoreceptors in the aortic bodiesTaste over the epiglottisB- somatic motorsoft palate, pharynx, and intrinsic muscles of the larynx C- parasympatheticsupply the heart (inhibitory), bronchial muscle and glands, glands and the smooth muscle of most of the gastrointesinal tract, and suprarenal gland. Examination

45. Vagus nerveThe pharyngeal and palate reflexes are tested as described for 9th nerve. Using a tongue depressor, the subject is asked to open his mouth wide and say “ah”. The response is constriction of posterior pharyngeal wall , and movement of the uvula backwards in the midline. But in vagal paralysis, the uvula is deflected to the normal side. The subject is asked for history of regurgitation of food through the nose, which is due to total paralysis of vagus; a nasal voice may also be noted. Laryngoscopy is done to note the position and movement of the true vocal cords.

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48. Vestibulocochlear nerveComponent: sensoryFunction: A- cochlear nervesupplies the cochlea and subserves hearingB- vestibular nervesupplies the semicircular canals (SCC; for dynamic equilibrium) and (otolith organ, utricle and saccule; for static equilibrium) and subserves equilibrium, balance, and sensation of bodily displacement.ExaminationHearing tests Watch testWhispere testRinne testNormally air conduction is better than bone conductionIn conductive deafness bone conduction is better than air conductionIn perceptive deafness both bone and air conduction are impaired

49. Vestibulocochlear nerveWeber’s testThe base of a vibrating tuning fork is placed in the middle of the foreheadNormally: vibration are heared equally at both earsIn conductive deafness: vibration is louder in the affected ear than in the healthy earIn nerve deafness: the vibration will not be heared in the affected ear and will be louder in the healthy ear Schwabach’s testThis comparison of bone conduction in the pt with that in a normal subject In conductive deafness : the pt will hear the vibration for longer time than normalIn nerve deafness the pt hear the vibration for much shorter time than normalCochlear nerve lesion tinnitus (ringing, buzzing, hissing, singing, or roaring noises in the ear) deafness; hearing scotomas (selective deafness to certain pitches and noises) sensory aphasia in supranuclear lesions

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51. OSPE Task: To demonstrate Rinne test on the subject provided. Procedural steps: see page 216. Checklist 1. Explains the test procedure and gives suitable instructions. (Y/N) 2. Selects either 216 Hz or 250 Hz tuning fork and strikes one of the prongs on the heel of her hand. (Y/N) 3. Closes the external auditory meatus of the subject’s other ear with her finger. (Y/N) 4. Places the base of the tuning fork on the subject’s mastoid process; when he raises his finger to indicate that the sound can no longer be heard. (Y/N) 5. Quickly transfers the vibrating tuning fork close to the subject’s ear. Notes if he can hear the sound once again. Notes down whether air or bone conduction is better. (Y/N)

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54. Vestibular nerveExamination A- Horizontal vestibulo-ocular reflexCompensate for head movement to stabilize visual image on the retinaHorizontal rotation of the head → slow compensatory eye movement equal in velocity but opposite in direction to head rotation HVOR pathwayHead rotation to the left depolarize hair cells in the left horizontal semicircular canal→ excite neurons in the left vestibular nucleus→ excite motor neurons to the rt lat rectus and left med rectus

55. Vestibular nerveB- Caloric test the external auditory meatus is irrigated with 250 ml of water at 30°C (7° below body temperature) for 40 seconds OR 44°CThis hot or cold water can stimulate the semicircular canal that is adjusted to lie in the vertical planeFor stimulating the horizontal canal The subject’s head is tilted back 60° and for both the vertical canals the head must be in the upright position THIS LEADS TO The endolymph moves due to convection currents, thus stimulating the receptors in the crista ampullarisRESPONSE Nystagmus with slow compensatory movement and fast (catch up) movements.

56. Vestibular nerveIf the water is warm (44 °C or above) endolymph in the ipsilateral horizontal canal rises, causing an increased rate of firing in the vestibular afferent nerve. This situation mimics a head turn to the ipsilateral side. Both eyes will turn toward the contralateral ear, with horizontal nystagmus (quick horizontal eye movements) to the ipsilateral ear.If the water is cold, relative to body temperature (30 °C or below), the endolymph falls within the semicircular canal, decreasing the rate of vestibular afferent firing. The eyes then turn toward the ipsilateral ear, with horizontal nystagmus to the contralateral ear.Direction of fast eye movementCOWS (cold opposite , warm same)

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58. C- Mechanical stimulation test (barany chair test)the subject is seated in a special chair which can be rotated at a definite speed, with the subject’s head tilted to specified positions to stimulate a particular pair of semicircular canals. The effects of acceleration and deceleration, i.e. nystagmus, vomiting, past pointing, and tendency to fall, can then be observedD- electrical stimulation test Using galvanic current (2-5) milli-amperes 2 electrodes one on the mastoid process and other on the back of the neckThis will stimulate directly crista of 3 SCCs E- past pointing test of barany

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