cranial nerves and their examination ppt

cranial nerves and examination

1. Cranial Nerves Examination

2. General characteristics The 12 pairs of cranial nerves are part of the peripheral nervous system As a rule, cranial nerves do not cross in the brain. Cranial nerves maybe sensory, motor both somatic or parasympathetic, or have mixed function

3. Olfactory Optic Auditory Trochlear Abducent Accessory Hypoglossal Trigeminal Facial Glossophatyngeal Vagus Occulomtor

4. Cranial Nerve 1: Olfactory ORIGIN : Cerebral hemisphere INNERVATION : Nasal mucous membrane

5. Function Carries the sensation of smell from nasal mucosa to olfactory bulb There is no motor component

6. Purpose of test To determine any impairment of smell ( unilateral/ bilateral) Whether impairment is due to any local nasal disease or neural lesion

7. Methods of testing Small bottles containing essences of very familiar odour are required Coffee Lemon Chocolate Asafetida etc

8. Procedure Ask whether he/she can smell or identify odour

9. Interpretation of result Parosmia : Each odour is similar but distorted and unpleasant Anosmia : Cant smell anything Impairment will also lead to decreased taste

10. Common causes of anosmia: Mucous blockage of the nose:  preventing odours from reaching the olfactory nerve receptors. Head trauma:  can result in shearing of the olfactory nerve fibres leading to anosmia. Genetics:  some individuals have congenital anosmia. Parkinson’s disease:  anosmia is an early feature of Parkinson’s disease. COVID-19 : transient anosmia is a common feature of  COVID-19 .

11. Cranial nerve II: Optic

12. Function Carries the visual impulses from the retina to the optic chiasma and in the optic tract to the lateral geniculate body The impulse acts as an afferent pathway for the pupillary light reflex

13. Purpose of test Visual acuity Colour vision Visual field Near Field Far field Colour matching Confrontation test

14. Method of testing Visual acuity: Snellen’s chart ( Far vision) Chart is placed at 20 feet or 6meter and patient is asked to read it The formula is d/D where d is 6 m and D is distance from which he can read it clearly Normal is 6/6 or 20/20

15. Jaegers chart (Near Vision) Paragraphs are prnted in successive coarser type with 0 is finest and 7 is biggesr Patient is asked to read through the hole.

16. Colour vision Checked by asking to match different colours Day or night blindeness can be assessed

17. Visual field Purpose To chart periphery of visual field To detect position, size and shape of the blind spot

18. Confrontation test

19. Common Causes Total unilateral loss of vision : Optic nerve lesion Homonymous hemianopia (loss of half of visual field in one eye): lesion between optic tact to occipital cortex Bitemporal hemianopia : lesion of optic chiasma

20. Specific Dysfunctions Blurred vision or complete blindness Ipsilateral vision loss - Optic atrophy, retinal/optic nerve lesions, trauma Cortical blindness : Lesion of occipital cortex B/l, pupil reflexes intact Papilledema : Optic nerve tumour, venous obstruction, chronic increased ICP Optic atrophy - Optic neuritis, increased ICP Scotomas (Abnormal blind spots on visual fields) – optic neuritis or atriophy

21. Cranial Nerves III, IV, VI: Occulomotor , Trochlear, Abducent

22. Cranial Nerve III: Occulomotor nerve ORIGIN: Midbrain INNERVATION: EOM’s; eyelid; ciliary; and sphincter of iris. FUNCTION : Eye movement inward (medially), upward, downward, and outward; pupil Constriction, shape and equality; elevates upper eyelid; accommodation reflex. DYSFUNCTION: Unable to look up, down, or medial ( dysconjugate gaze); ptosis, pupil dilatation -bilateral or ipsilateral, and loss of accommodation reflex.

23. Cranial Nerve IV: Trochlear Nerve ORIGIN : Midbrain INNERVATION : Superior oblique muscle FUNCTION : Down and inward movement of the eye DYSFUNCTION: Loss of downward, Inner movement of eye, dysconjugate gaze.

24. Cranial nerve III: Abducens Nerve ORIGIN: Pons INNERVATION : Lateral rectus muscle. FUNCTION: Outward,lateral movement of eye. DYSFUNCTION: Loss of lateral eye movement, disconjugate gaze

25. Function Controls the external ocular muscles and elevators of the lids Also regulate the pupillary muscles

26. Purpose of the test Inspect pupils to rule out a local disease, peripheral lesion or a nuclear involvement Examine eye movement and determine if defects is muscular origin or neural involvement To detect nystagmus

27. Method of testing Observation Presence and absence of ptosis and squint Whether unilateral or bilateral Constant or variable Size, shape, equality and regularity of the pupils

28. Reaction to light Reduce illumination of room and vision should focus on a far object A bright beam of light is shone from the side of one eye Repeat on the other side (the pupil should constrict briskly) Shield one eye and perform test on the other and see for consensual reaction

29. Reaction to convergence and accommodation for near vision Fix vision on a distant object and instruct to look in a near object Place finger tip in front of the bridge of the nose (22cm) Then return to the far object Observe pupillary reaction in both

30. Examination of ocular movement Observe lagging of one or both eye Observe nystagmus

31. Analysis of diplopia Shield one eye with a transparent red shield Object is moved from left to right, up and down Ask if- Pt. sees 1 or 2 objects Objects lie one above the other or side by side

32. Rules governing analysis of diplopia Separation of image is greatest in the direction in which weak muscle has its purest action False image is displaced farthest in the direction in which the weak muscle should move the eye

33. Analyzing nystagmus Watch the patients eye while talking Ask it look at a definite point and move the point from left to right and up to down Hold each position for 5 sec and assess nystagmus direction, rate, amplitude)

34. Common causes of paralysis Pontine lesions Neoplasms Vascular accidents Demyelinating disease Meningeal inflammation Tumour of base of skull Increased intra cranial pressure Head injury [Total paralysis of III. IV and VI nerve indicate a lesion in cavernous sinus (carotid aneurism)]

35. Cranial Nerve V: Trigeminal

36. Trigeminal nerve ORIGIN: Pons. The sensory nucleus extends from thepons to the midbrain, and also to the medulla and spinalcord .  INNERVATION: Three branches of CN V: Ophthalmic, maxillary, & mandibular. Motor innervation to masseter & temporal muscles. Sensory innervation to skin & mucous membranes in head; teeth, tongue, external auditory canal, and cornea .

37. Trigeminal nerve FUNCTION: Sensation of pain, touch, hot, & cold; motor  movement of masseter &temporal muscles. DYSFUNCTION: Loss of sensation - if affecting all three branches, indicative of peripheral injury. Brainstem or upper cervical cord injury may result in loss of sensation to one or more branches of the trigeminal nerve. Paresthesia and/or severe pain indicative of nerve compression or irritation(Trigeminal neuralgia) Loss of corneal reflex.

38. Tic douloureux or  trigeminal neuralgia Paroxysmal attacks of severe, short, sharp, stabbing pain affecting one or more branch of the nerve. Caused by inflammation of  nerve

39. Purpose of the test To determine any sensory impairment To determine unilateral or bilateral motor weakness and determine UMN from LMN

40. Method of examination Superifical sensory touch from mainly 6 areas (light touch and pain) Forehead and upper part of the side of nose (ophthalmic) Malar and upper lip region (maxillary) Chin and anterior part of tongue (mandibular)

41. Interpretation Total loss of sensation: lesion of ganglion or sensory root Total sensory loss over 1 division: partial lesion of ganglion root Touch only lost: pontine lesion affecting sensory nucleus Pain and temp lost: dissociate anesthesia ( syringobulia )

42. Motor examination: Muscle power of masticatory muscle namely the masseter and temporalis Inability to raise, depress, protrude, retract and deviate the mandible

43. Jaw Jerk Ask the patient to relax jaw. Place finger on the chin and tap it with hammer. C losing of mouth is the response Brisk is normal Exaggerated is pathological

44. Corneal reflex Using a cotton piece, the cornea is teased Normal response is a bilateral blink Afferent- ophthalmic division of V! nerve Efferent- Facial nerve

45. Interpretation If you tap the patient’s sclera and neither eye blinks >> ipsilateral CN V lesion. This lesion localization is confirmed if the patient blinks with both eyes when the opposite eye is stimulated. However, if when the opposite eye is stimulated, the patient’s eyes still fail to blink, the abnormality either localizes to the B/l CN V or B/L CN VII If you tap the patient’s sclera and one eye blinks but the other does not >> CN VII that fails to blink.This same eye should fail to blink when you tap the patient’s other eye.

46. Cranial nerve VII: Facial Nerve

47. Function Supplies the muscles of facial expression including platysma and stapedius Secretomotor fibers to the lacrimal gland and the salivary gland Carries sensation of taste from anterior 2/3rd of tongue and general sensation from external acoustic meatus

48. Purpose of the test To detect any unilateral or bilateral weakness of facial muscles (UMN or LMN) Detect impairment of taste

49. Method of testing Observation Symmetry and asymmetry of face Nasolabial fold and wrinkle on forehead Ask the patient to close the eyes, raise the eyebrows, blow out the cheek, whistle, etc

50. Examination of taste The four primary taste (sweet, salt, sour, bitter) can be carried out by using sugar, salt, vinegar and quinine. The side of the tongue is moistened by the test substance. Ask the patient to indicate taste by pointing.

51. Secretomotor function The flow of tears of two side can be compared by giving ammonia to inhale which will result in tearing of eye The flow of saliva can be tested by keeping a spicy substance in the tongue and the tip is raised to observe the sub mamdibular salivary flow.

52. Reflexes Corneal reflex Nasopalpebral reflex: tap on the nasopalpebral ridge will produce closure of both eyes. In bells palsy there is failure to close on the affected side

53. Cranial Nerve VIII: Vestibulocochlear

54. Function Carries the impulses of sound from the hair cells of organ of corti to cochlear nucleus in pons Control balance through vestibular nerve

55. Purpose of the test To determine any deafness is bilateral or unilateral Whether deafness is due disease of middle ear or cochlear nerve To determine the disturbance of vestibular functions

56. Test of hearing Observe if the patient turns one ear towards you Evaluate hearing using a ticking watch, rub fingers together, whisper.

57. Rinne’s test Strike a tuning fork gently, hold it near one external meatus and ask the patient if he can hear it Place it on the mastoid, ask if he can still hear it and instruct him to say “NOW” when sound ceases, and keep it on the external meatus again (normally the notes is still audible)

58. Interpretation In conductive deafness- not be able to hear the tuning fork when it is moved next to the external auditory meatus In sensineural deafness- equally reduced

59. Weber’s test The fork is place on the vertex Ask the patient if he can hear the sound all over the head, in both ears or in one ear In sensineural deafness, the sound appear to be heard on the normal ear In conductive deafness, sound is louder in the abnormal ear.

60. Common causes of deafness Disease of external and middle ear and eustachian tube Prolonged exposure to loud noise Old age Meningitis Demyelinating disease

61. Test of vestibular function Observe equilibrium as patient walks or stands Observe abnormal eye movts Ask for- Dizziness Falling Nausea and vomiting

62. Cranial Nerve IX: Glossopharyngeal

63. Function Visceral sensory: subconscious sensation from carotid body and sinus General Sensory: posterior 1/3 of tongue, tonsil, skin of external ear, tympanic membrane and pharynx Visceral Motor: parasympathetic stimulation of parotid gland, and control blood vessels Branchial Motor: Supplies stylopharyngeus muscle Special Sensory: carries taste from posterior 1/3 tongue

64. A unilateral lesion: loss of the ipsilateral gag reflex loss of carotid body and sinus reflex loss of taste in the posterior region of the tongue.

65. Cranial Nerve X: Vagus

66. Function General Sensory: posterior meninges, concha, skin at back of ear, external tympanic membrane, pharynx and larynx Visceral Motor: parasympathetic stimulation to smooth muscle and glands of pharynx, larynx; thorax and abdominal viscera and cardiac muscle Visceral sensory: from larynx, trachea, esophagus , and thoracis and abdominal viscera, stretch receptors and chemoreceptors Motor: superior, middle, inferior constrictors; levator palati , salpingopharyngeus

67. Purpose of the test To test the elevation of palate and contraction of pharynx To examine the movts of vocal cords

68. Method of testing Notice the pitch and quality of voice, cough Ask the patient to open his mouth wide, after a few movts ask to say “AH” while breathing out and “UGH” while in The palate should move symmetrically upwards and backwards, the uvula in midline and two sides of pharynx contract symmetrically Unilateral vagus nerve lesions result in hoarseness, dysphagia and dyspnea Bilateral vagal nerve injuries result in airway obstruction and asphyxia

69. Common causes of lesion Poliomyelitis Syringobulbia Posterior fossa tumor Advanced parkinsonism Myasthenia gravis Enlarged cervical glands Surgical operation of the neck

70. Cranial Nerve XI: Accessory

71. Function Supplies sternocleidomastoid and trapezius muscles

72. Purpose of the test To detect wasting and weakness, unilateral or bilateral of the muscles

73. Method of testing

74. Common causes of paralysis MND Poliomyeltis Polyneuropathy Trauma in neck or base of skull Tumour at jugular foramen Syringomyelia

75. Cranial nerve XII: Hypoglossal

76. Function Controls movts of the tongue, hyoid bone and larynx during and after deglutition Supplies 3 of 4 extrinsic muscles of tongue and all intrinsic muscles of tongue

77. Purpose of the test To inspect the surface of the tongue To detect wasting, weakness and involuntary movts To examine voluntary muscle control

78. Method of testing Ask the patient to protrude the tongue and observe for Reduction in size of affected side Excessive ridging and wrinkling Restricted protrusion Deviation towards one side

79. Common lesions Syringomyelia Poliomyelitis MND Profound hemiplegia ALS

80. References Cranial Nerve Assessment: A Concise Guide to Clinical Examination by OMPRAKASH DAMODARAN ELIAS RIZK, JULIAN RODRIGUEZ, AND GABRIEL LEE Rothwell P. Examination of the cranial nerves. BMJ. 2000 Mar 4;320(7235):655A. PMID: 10698908; PMCID: PMC1117678.

81. Thank you!