Cranial nerves

cranial nerves and dentistry

1. CRANIAL NERVES PART 1

2. CONTENTS Introduction. Organization of Nervous System. Related Terminologies. Cranial Nerves. Detailed study of V. Trigeminal nerve VII. Facial nerve IX. Glossopharyngeal nerve X. Vagus nerve XII. Hypoglossal nerve References.

3. INTRODUCTION The nervous system is the most important organization which controls and integrates the different bodily functions and likewise maintains a stability of the internal environment despite extreme changes in the external environment. This system is absolutely necessary for the reception , storage and release of different sensory and motor informations for regulating or initiating a particular behaviour of the individual. It is a very complicated system; structures and organs are specialised for different specific purposes.

4. NERVOUS SYSTEM CENTRAL NERVOUS SYSTEM PERIPHERAL NERVOUS SYSTEM BRAIN SPINAL CORD SOMATIC AUTONOMOUS CRANIAL NERVES 12 PAIRS SYMPATHETIC PARASYMPATHETIC SPINAL NERVES 31 PAIRS ORGANIZATION OF THE NERVOUS SYSTEM

5. RELATED TERMINOLOGIES NEURON: It is the structural and functional unit of the nervous system and consists of a nerve cell body with all its processes.

6. NUCLEUS: A mass of grey matter, composed of nerve cells, in any part of the brain or spinal cord. GANGLION: It is a group of nerve cell bodies situated outside the brain and spinal cord. Cranial nerve nuclei as projected on to the dorsal aspect of the brain stem.

7. TRACT: A bundle or group of nerve fibers in the brain or spinal cord. NERVE: A bundle of neuronal processes outside the central nervous system. PLEXUS: A network or interjoining of nerves .

8. VISCERAL NERVES: N erves which supply (or bring information from) the different viscera, the organs within the body cavity. These nerves are better known as autonomic nerves. SOMATIC NERVES: They supply somatic structures (skin and muscles).

9. AFFERENT NERVE: These fibres bring information from the periphery to the CNS. (or ) from one part of the CNS to another part. (e. g. from the spinal cord to the brain). All afferent nerves are sensory. EFFERENT NERVE: Carry commands to the organ supplied. (or) they carry command from one part of the CNS to another part (e.g. from brain to spinal cord). All efferent nerves are motor.

10. GENERAL: Refers to stimuli conducted throughout the entire body, common to both cranial and spinal nerves.Eg : touch, pressure, vibration, pain , thermal sensation and proprioception . SPECIAL: Afferent information is encoded by highly specialized sense organs and transmitted to the brain in certain cranial nerves (I, II, VII, VIII, IX) Ex; olfaction, vision, taste, hearing and vestibular function.

11. Cranial nerves I.Olfactory nerve II.Optic nerve III.Occlumotor nerve IV.Trochlear nerve V.Trigeminal nerve VI.Abducens nerve VII.Facial nerve VIII.Vestibulocochlear nerve IX.Glossopharyngeal nerve X.Vagus nerve XI.Accessory nerve XII.Hypoglossal nerve

12. Classification Sensory cranial nerves I. Olfactory II. Optic VII. Vestibulocochlear Motor cranial nerves III. Occluomotor IV. Trochlear VI. Abducent XI. Accessory XII. Hypoglossal Mixed cranial nerves V. Trigeminal VII. Facial IX. Glossopharyngeal X. Vagus

13. TRIGEMINAL NERVE

14. TRIGEMINAL NERVE It is the fifth (V) cranial nerve The largest cranial nerve It is a mixed nerve, contains both sensory & motor fibres . It is attached to the ventral surface of the pons , near its upper border, by a large sensory and a small motor , root---the latter being placed medial and anterior to the former.

15. Sensory and motor root of the trigeminal nerve The two roots then enter the middle cranial fossa .

16. Superior view of the middle cranial fossa showing some of its contents

17. Sensory root of trigeminal nerve The fibres of this root arise from the semilunar ( gasserian ) ganglion. They enter the brain stem through the side of pons . Semilunar ganglion: neural crest Unipolar neurons Crescent shaped Meckel’s cavity Peripheral & central processes

18. Peripheral branches V 1 ophthalmic V 2 maxillary V 3 mandibular divisions Central branches (sensory roots) ascending descending branches

19. Motor root of trigeminal nerve consists of fibres that arise in the motor nucleus located in upper pons Pons – medial side of semilunar ganglion – foramen ovale – to join mandibular division immediately below the base of the skull. Motor supply to the muscles of mastication– masticator nerve.

20. Nuclei of the trigeminal nerve Sensory nuclei Mesencephalic Primary sensory Spinal Motor nucleus

21. Mesencephalic nucleus Consists of afferent fibres that accompany the fibres of the motor root. Entering the pons from the peripheral distribution of the of the mandibular division of the trigeminal nerve,these fibres ascend to the mesencephalic nucleus of the trigeminal nerve. This nucleus serves as an afferent station that receives proprioceptive impulses from the temporomandibular joint,the periodontal membrane,the maxillary and mandibular teeth, and the hard palate. The mesencephalic nucleus also receives afferent impulses from stretch receptors in the muscles of mastication.

22. Primary sensory nucleus Lies in the upper part of the pons . Lateral to the motor nucleus. Mainly concerned in mediation of poprioceptive impulses touch and preassure (from the region to which the trigeminal nerve is distributed).

23. Spinal ( bulbospinal ) nucleus: Caudal to the sensory nucleus. Forms ventral trigeminothalamic tract. Convey pain & temp from the entire Trigeminal area.

24. Motor nucleus Lies in the upper part of the pons in the dorsal part. It is situated mesial to the main sensory nucleus

25. Functional components General somatic affarent : transmit exteroceptive impulses of touch pain and thermal senses from the skin of the face and forehead, mucous membranes of nasal cavities, oral cavity, nasal sinuses, and floor of the mouth; the teeth; the anterior two thirds of the tongue; and extensive portions of the cranial dura .

26. Proprioceptive impulses (deep preassure and kinesthesis ) are conveyed from the teeth, periodontium , hard palate and temporomandibular joint receptors. The nerve also conveys afferent fibers from stretch receptors in the muscles of mastication.

27. Special viceral efferent: fibers innervate the muscles of mastication, the tensor tympani and the tenor veli palatini muscles, anterior belly of digastric .

28. Divisions of the trigeminal nerve Opthalmic V1 Maxillary V2 Mandibular V3

29. Opthalmic division V 1 First division of the trigeminal nerve Smallest of the three branches Its fibres are sensory,or afferent, from the scalp, the skin of the forehead, the upper eyelid lining the frontal sinus, the conjunctiva of the eyeball, the lacrimal gland, and the skin of the lateral angle of the eye. It also transmits sensory impulses from the sclera of the eye ball & the lining of the ethmoid cells. Leaves ant. medial part of ganglion – cavernous sinus – superior orbital fissure – orbit In the middle cranial fossa nervus tentori – dura communication br. Occlumotor Trochlear Abducent

30. Branches Lacrimal Frontal Nasocilliary

31. Lacrimal nerve Smallest of the three branches It passes in to the orbit at the lateral angle of the superior orbital fissure. Then courses in an anterolateral direction to reach the lacrimal gland. Structures supplied Lacrimal gland Sensory from the skin of upper eyelid & Lateral part of Eyebrow region. Sensory from the conjunctiva of the lateral part of upper eyelid

32. Frontal nerve Largest of three branches. Direct continuation of the ophthalmic division. It enters the orbit by way of the superior orbital fissure. At about the middle of the orbit the frontal nerve divides in to two branches: supraorbital and supratrochlear nerves. Supraorbital nerve Supratrochlear nerve Largest branch of frontal n. Smallest branch of frontal n. Leave the orbit through supra orbital foramen Passes toward the medial angle of the orbit Sensory from the medial part of the upper eyelid , the skin of the forehead and scalp to the vertex of the skull Sensory from the medial part of the upper eyelid and the lower medial part of the forehead Sensory from the lining of the frontal sinus Sensory from the conjuctivae of the upper eyelid

33. FRONTAL NERVE Medial branch, supraorbital nerve Supratrochlear nerve Frontal nerve Ophthalmic nerve Lateral branch, supraorbital nerve

34. Nasocilliary nerve It enters the orbit through the superior orbital fissure. In nasal cavity: Supply mucous membrane lining the cavity. Terminal branches on the face: Sensory to skin of medial part of both eyelids, lacrimal sac, lacrimal caruncle . Also skin over the side of the bridge of the nose.

35. NASOCILLIARY NERVE Enters orbit through Superior orbital fissure Branches Infratrochlear nerve Short ciliary nerves Posterior ethmoidal nerve Anterior ethmoidal nerve Nasociliary nerves

36. In the orbit Long root of ciliary ganglion Long ciliary nerves Posterior ethmoid nerve sensory no relay eyeball short ciliary nerves Two to three branches Iris & cornea Post ganglionic fibres From sup. Cervical ganglion. Posterior ethmoid canal Muc mem . Of post.ethmoid al cells Sphenoid sinus

37. 4. Anterior ethmoid nerve Nasociliary – continues anteriorly in medial of orbit Supplies mucous membrane of anterior ethmoid cells & frontal sinus. In the upper part of nasal cavity it divides in to two sets of anterior nasal branches External nasal branches Skin over the tip and ala of the nose Internal nasal branches Divide in the upper anterior part of the nasal cavity Medial/ septal Sensory to muc mem of that region Lateral Muc mem of ant ends– sup & middle Nasal conchae Ant lat nasal wall

38. Applied anatomy Ciliary ganglion It is topographically related to this nerve but functionally to oculomotor . Autonomic ganglia In case of injury to opthalmic nerve, there is loss of “ corneal blink reflex”

39. Maxillary nerve V 2 The maxillary nerve is entirely sensory in function.

40. Branches Branches given off in the middle cranial fossa Branches in the pterygopalatine fossa Branches in the infraorbital groove and canal Terminal branches on the face

41. Branches of the maxillary division Middle cranial fossa Middle meningeal nerve Pterygo -palatine fossa 1. Zygomatic nerve zygomaticotemporal zygomaticofacial 2. Pterygo -palatine nerves orbital nasal a. posterior superior lateral nasal branches b. nasopalatine palatine greater palatine middle palatine posterior palatine pharyngeal 3. Posterior superior alveolar GREATER PALATINE POSTERIOR PALATINE NASOPALATINE

42. Infraorbital canal Middle superior alveolar Anterior superior alveolar Face Inferior palbebral External nasal Superior labial 1 PSA branches 2 Infra orbital n. 3 Maxillary nerve 4 Foramen rotundum 5 Greater palatine 6 Nasopalatine

43. Applied anatomy Sphenopalatine ganglion It is topographically related to this nerve but functionally to facial nerve . It is the largest peripheral parasympathetic ganglion Autonomic ganglia In case of injury to opthalmic nerve, there is loss of “ sneeze reflex”

44. Mandibular division V 3 Largest of the three divisions of the Vth nerve. Formed by union of large sensory & small motor bundle of fibers. Sensory fibers arise from semilunar ganglion. Motor fibers derived from motor cells located in the medulla oblongata.

45. Course of the mandibular nerve

46. Branches Main trunk Anterior trunk Posterior trunk

47. Branches from main trunk a) nervous spinosus : arises outside the skull – passes into middle cranial fossa to supply dura & mastoid cells b) nerve to internal Pterygoid muscle: motor Internal pterygoid tensor veli palatini tensor tympani

48. Branches from the anterior trunk Anterior trunk supplies (sensory & motor) skin & mucous membrane of the cheek, buccal gingivae &lower molars.It passes downward & forward where it divides: 1.Branch to external pterygoid muscle 2.Branch to masseter muscle 3.Branches to temporal muscles a. Anterior deep temporal nerve b. Posterior deep temporal nerve 4.Buccal (long buccal ) nerve

49. Branches from the posterior trunk mainly sensory with some motor components 1.Auriculotemporal 2.Lingual 3.Inferior alveolar

50. Auriculotemporal nerve Arises by a medial & lateral root. The roots embrace the middle meningeal artery & unite just below the foramen spinosum Deep to Lateral pterygoid – between sphenomandibular ligament & neck of condyle . Crosses zyg arch upwards and divides Branches: Parotid: sensory, secretory , vasomotor . Articular : post TMJ Auricular: skin of helix & tragus Meatal : skin lining meatus & tympanic membrane Terminal: scalp over temporal region

51. Communications of auricotemporal nerve: Two roots of the nerve ,each root receives communicating fibers from the otic ganglion. These fibers are postganglionic parasympathetic secretory fibers that have come from the glossopharyngeal nerve by way of lesser superficial petrosal nerve. They control the secretion of the parotid gland. Communicating branches of postganglionic sympathetic fibres – vasomotor to parotid. Communicating branches to facial – purely sensory.

52. Lingual nerve Medial to Lateral Pterygoid muscle – descends – lies between medial pterygoid & ramus of mandible in pterygo mand space. - Contributes sensory fibers to the mucous membrane of the floor of mouth & gingiva on lingual surface of mandible. Also to bicuspids & 1 st molars.

53. Communications of the lingual nerve: As the lingual nerve passes medial to the lateral pterygoid muscle it is joined by corda tympani nerve, which conveys secretory fibres from the facial nerve. These parasympathetic fibers control the submandibular & sublingual salivary glands.

54. Inferior alveolar nerve largest of the branches of the post div of mandibular nerve. Medial to ramus , in the pterygomandibular space, it enters the mand . Foramen It is distributed throughout the body of mandible In the canal – apical fibres to dental pulp, also to periodontal membrane. At the mental foramen – mental nerve, incisive nerve

55. At mental foramen, div into 2 branches Mental nerve : leaves the mental foramen, supplies skin of the chin, lower lip & mm of lower lip. sensory Incisive nerve: fine incisive plexus to supply cuspids & incisors Before entering mandibular foramen, gives off mylohyoid branch Dwn & frwd in mylohyoid groove. Motor fibres : mylohyoid , ant belly of digastric . Sensory:mandibular incisors

56. Autonomic ganglia associated with mandibular branch Submandibular ganglion: peripheral parasympathetic ganglion. Topographically related to lingual nerve, but functionally related to corda tympani branch of facial. Otic ganglion: peripheral parasympathetic ganglion. Topographically intimately related to mandibular nerve, but functionally to glossopharyngeal nerve.

57. Applied anatomy Trigeminal neuralgia/Tic Douloureux characterised by extremely severe lancinating pain that occurs in paroxysms, limited to one or more branches of Trigeminal n. Etiology: Idiopathic Vascular compression Progressive degeneration Intra-cranial tumor Peripheral nerve injury

58. Clinical features: - Older adults, Female predilection - Right side affected more - Intense shooting stabbing pain - Electric shock-like - Unilateral - Maxillary > Mandibular > Ophthalmic - Trigger zone

59. Treatment of trigemial neuralgia Carbamazepine – 100mg thrice daily, titrated over 1-5 weeks till remission. 1.Peripheral nerve- a. cryosurgery b. peripheral neurotomy 2.Gasserian ganglion- a.Thermocoagulation b. Glycerol injection 3.Brain stem- Microvascular decompression of nerve root

60. Frey’s syndrome: damage to auriculotemporal nerve & subsequent reinnervation of sweat glands. C/F: Flushing & sweating on the invovled side of the face Treatment: severing the nerve Sensory distribution of trigeminal nerve explains why headache is a common symptom in invovlement of - the nose (common cold, boils ) - the PNS ( sinusitis ) -teeth & gums ( infections & inflamns ) -eyes ( refractive errors, glaucoma ) - meninges (meningitis )

61. Posterior superior alveolar nerve block Complications- Hematoma This is produced by inserting the needle far too posteriorly in to the pterygoid plexus of veins 1 maxillary nerve 2 posterior superior alveolar branches

62. GOOD MORNING !!!

63. CRANIAL NERVES PART 2

64. CONTENTS Introduction. Organization of Nervous System. Related Terminologies. Cranial Nerves. Detailed study of V. Trigeminal nerve VII. Facial nerve IX. Glossopharyngeal nerve X. Vagus nerve XII. Hypoglossal nerve References.

65. Facial nerve

66. FACIAL NERVE It is the seventh cranial nerve (VII) It is the nerve of the second branchial arch It is both motor and sensory

67. Nuclei of the facial nerve Motor nucleus Superior salivatory nucleus Lacrimatory nucleus Nucleus of tractus solitarius

68. Central connections Motor nucleus Upper part of face : Cortico -nuclear fibres from motor cortex of both sides. Lower part of face : Cortico -nuclear fibres from opposite cerebral hemisphere .

69. Functional components S pecial visceral efferent muscles of 2 nd branchial arch G eneral visceral efferent secretomotor S pecial visceral afferent taste sensation from anterior 2/3rd of tongue and palate G eneral somatic afferent part of skin of the ear

70. Course The course of the facial nerve can be divided in to Intracranial Extracranial

71. Intracranial course

72. Structures in the left internal accoustic meatus

73. Extracranial course Superficial to styloid process Pierces surface of parotid gland Runs forward Temporo -facial and Cervico -facial trunks Divides into 5 branches

74. Branches In the facial canal Greater petrosal nerve Nerve to stapedius Chorda tympani At the stylomastoid foramen Posterior Auricular Digastric (posterior belly) Stylohyoid Terminal branches within the parotid gland Temporal Zygomatic Buccal Marginal mandibular Cervical Communicating branches with adjacent cranial and spinal nerves

75. Applied anatomy Supra nuclear paralysis Infranuclear paralysis

76. Infranuclear paralysis Lesion 1outside the stylomastoid foramen Lesion 2 in the facial canal and involving the corda tympani nerve Lesion 3 higher in the facial canal and involving the stapedius muscle Lesion 4 involving the geniculate ganglion Lesion 5 in the internal auditory meatus Lesion 6 at the emergence of facial nerve from pons

77. Bell’s Palsy Definition: Bell’s palsy is defined as an idiopathic paresis or paralysis of the facial nerve of sudden onset(unilateral lower motor neuron paralysis of sudden onset, not related to any other disease elsewhere in the body). Etiology Symptoms

78. Treatment Physiotherapy Steroids - prednisolone 1mg/kg body wt for 10-14 days with a gradual tapering Proper care of the eye Antivirals Chronic sequeale Hyperkinesia Hypokinesia

79. Glossopharyngeal nerve

80. GLOSSOPHARYNGEAL NERVE IX Cranial nerve Mixed Nerve of third branchial arch Ganglia

81. Nuclei of the Glossopharyngeal nerve Nucleus ambiguus Inferior salivatory nucleus Nucleus of tractus solitarius

82. Functional components

83. SVE GVE AFFERENT

84. Course - Intracranial

85. Course - Extracranial Lingual Branches Tonsillar Branches

86. Branches Tympanic Carotid Pharyngeal Muscular Tonsillar Lingual

87. Applied Anatomy Glossopharyngeal neuralgia Rare Paroxysmal pain Trigger zone May be associated with vagal symptoms Etiology : Tumours and vascular abnormalities Treatment : Carbamazepine Surgical section of nerve Percutaneous radiofrequency thermocoagulation Microvascular decompression

88. VAGUS NERVE

89. VAGUS NERVE X cranial nerve Extensive (vague) course 3 parts- Cervical Thoracic Abdominal Cervical part presents 2 ganglia Inferior Superior

90. Nuclei of the vagus nerve Neucleus ambiguus Dorsal nucleus of vagus Nucleus of solitary tract Spinal nucleus of trigeminal nerve

91. Functional components

92. Course

93. Branches JUGULAR FORAMEN Meningeal Auricular NECK Pharyngeal branches Superior laryngeal Branches to carotid body Cardiac branches Right recurrent laryngeal THORAX Cardiac Left recurrent laryngeal Pulmonary Oesophageal ABDOMEN Gastric Coelic Hepatic

94. Applied Anatomy Clinical testing Paralysis of the vagus nerve Irritation of the auricular branch of the vagus Stimulation of the auricular branch Irritation of the recurrent laryngeal nerve Communication with facial nerve

95. Hypoglossal Nerve

96. Hypoglossal Nerve XII cranial nerve Motor Supplies all muscles of the tongue, except palatoglossus muscle

97. Nuclei & Functional components Hypoglossal nucleus: elongated nucleus Functional components: General somatic efferent

98. 10- 15 rootlets through medulla oblongata Two bundles Pierce dura mater Lower part of the canal – single nerve trunk Hypoglossal canal Between internal jugular vein and internal carotid artery It decends between internal jugular vein & internal carotid artery in f ront of the vagus deep to the parotid gland ,the styloid process, post. belly of diagastric,stylohyoid , and posterior auricular & occipital arteries Course

99. At the lower border of post. Belly of diagastric it curves forwards, hooks round the lower sternomastoid branch Of occipital artery crosses IC & EC arteries & the loop of the lingual artery & enters submandibular region Rests on hyoglossus muscle Deep to mylohyiod muscle Pierces genioglossus Substance of the tongue

100. Branches Meningeal Descending Thyrohyoid Muscular

101. Applied Anatomy Clinical testing---by asking the patient to protrude his tongue. Lesion produces paralysis of the tongue of that side. Inranuclear lesion – gradual atrophy of paralyzed half of the tongue. Supranuclear lesion – paralysis without wasting.

102. A clinicians complete knowledge of the anatomy of the cranial nerves and its applied aspect is necessary for providing treatment and preventing complications in routine clinical practice. Conclusion

103. References Human anatomy BD Chaurasia . Vol 3, 3 rd edition. Grays anatomy 39 th edition. Handbook Of Local Anaesthesia, Malamed 5 th edition . Burkets Oral medicine-10 th edition. Lee Mc Gregor’s synopsis of surgical anatomy 12 th edition. Monheim’s local anesthesia & pain control in dental practice.7 th edition. Human physiology Chatterjee 10 th edition. Correlative neuroanatomy and functional neurology Chusid 16 th edition. Stedmans medical dictionary 21 st edition. Textbook of OMFS Neelima Malik 1 st edition. Textbook of human neuroanatomy Inderbir Sing 6 th edition. Cranial nerves functional anatomy Stanley Monkhouse . Electronic media.