Cranial nerves

Brief review about Cranial Review.

1. GOOD MORNING

2. CONTENTS co 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 Nervous system - Controls the functions of the body. Composed basically of specialized cells, whose function is to receive sensory stimuli and to transmit them to effector organs, whether muscular or glandular.

4. ORGANIZATION

5. RELATED TERMINOLOGIES Neuron : Structural and functional unit of nervous system.

6. Nucleus : Discrete group of nerve cell bodies in the central nervous system. Ganglion : Group of nerve cell bodies located outside central nervous system.

7. Tract : Bundles of nerve fibres found in the central nervous system. Nerve : Bundles of nerve fibres found in the peripheral nervous system. Plexus : A network of intersecting nerves.

8. Visceral Nerves : They are the nerves which supply the different viscera, the organs within the body cavity. Somatic nerves : They supply somatic structures (skin and muscles).

9. Afferent nerve : Sensory or receptor neurons - carry nerve impulses from receptors or sense organs toward the central nervous system. Efferent nerve : Motor or effector  neurons – carry nerve impulses away from the central nervous system to effectors such as muscles or glands.

10. General : Refers to stimuli conducted throughout the entire body, common to both cranial and spinal nerves. e.g. touch, pressure, vibration, pain and proprioception . Special : Afferent impulses are encoded by highly specific sense organs and transmitted to the brain in certain cranial nerves. e.g. Olfaction, vision, taste, hearing and vestibular function.

11. CRANIAL NERVES I.Olfactory nerve II.Optic nerve III.Oculomotor nerve IV.Trochlear nerve V.Trigeminal nerve VI.Abducens nerve VII.Facial nerve VIII.Auditory nerve IX.Glossopharyngeal nerve X.Vagus nerve XI.Accessory nerve XII.Hypoglossal nerve Trochlear

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

13. TRIGEMINAL NERVE

14. TRIGEMINAL NERVE V cranial nerve. Largest. Mixed.

15. NUCLEAR CONNECTIONS Sensory nuclei : Mesencephalic . Primary sensory. Spinal. Motor nucleus.

16. FUNCTIONAL COMPONENTS General somatic afferent : Exteroceptive Proprioceptive Special visceral efferent : Muscles of first branchial arch.

17. COURSE PONS SENSORY ROOT MOTOR ROOT TRIGEMINAL GANGLION Ophthalmic branch (V 1 ) Maxillary branch (V 2 ) Mandibular branch (V 3 )

18. Sensory root Motor root V1 V2 V3

19. BRANCHES Ophthalmic Maxillary Mandibular

20. OPHTHALMIC NERVE (V 1 ) 1 st Branch Sensory Smallest

21. Lacrimal nerve Smallest branch Communicating branch : Zygomatico -temporal Provides sensory branches : Lacrimal gland Conjunctiva Supplies lateral part of upper eyelid

22. Largest branch Frontal nerve Medial branch, supraorbital nerve Supratrochlear nerve Frontal nerve Ophthalmic nerve Lateral branch, supraorbital nerve

23. Nasociliary nerve Enters orbit through Superior orbital fissure Branches Long ciliary nerves Infratrochlear nerve Short ciliary nerves Posterior ethmoidal nerve Anterior ethmoidal nerve Nasociliary nerves

24. Anterior ethmoidal nerve : continuation of Nasociliary nerve Branches : Medial internal nasal Lateral internal nasal Lateral internal nasal emerges as External nasal nerve. Supplies skin over tip and ala of the nose.

25. MAXILLARY NERVE (V 2 ) Pre- trematic branch of trigeminal nerve Sensory

26. Middle cranial fossa - Middle meningeal Pterygo -palatine fossa 1. Zygomatic zygomaticotemporal (a) zygomaticofacial (b) 2. Pterygo -palatine orbital nasal - nasopalatine ( i ) palatine - greater palatine(ii) - lesser palatine (iii) pharyngeal 3. Posterior superior alveolar 1 2 3 a b i ii iii

27. Infraorbital canal a. Middle superior alveolar b. Anterior superior alveolar Face a. Inferior palbebral b. External nasal c. Superior labial MSA ASA

28. MANDIBULAR NERVE(V 3 ) Largest branch Post- trematic nerve of 1 st branchial arch Mixed

29. Undivided nerve -Nervous Spinosus -N. to medial pterygoid Anterior division -N. to lateral pterygoid -N. to masseter -N. to temporal muscle - Buccal n.

30. Posterior division - Auriculotemporal Auricular Superficial temporal Articular Communicating branches - Facial nerve - Otic ganglion - Lingual - Inferior alveolar Mylohyoid Incisive Mental Mylohyoid br. Inferior alveloar n. Lingual n. Mental n. Incisive n. Mandibular n. Auriculo temporal n.

31. CLINICAL TESTING Motor system : Masseter and temporal muscles Pterygoids . Sensory system : Pain, temperature and light touch in ophthalmic, maxillary and mandibular division. Reflexes : Corneal reflex Jaw reflex V 1 V 2 V 3

32. 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

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

34. Treatment : Carbamazepine

35. Frey’s syndrome Damage to auriculotemporal nerve & subsequent reinnervation of sweat glands. Clinical features : Fl ushing & sweating on the involved side of the face Treatment : Botulinum toxin injections Resection of nerve

36. GOOD MORNING !!!

37. CRANIAL NERVES PART II

38. 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.

39. FACIAL NERVE

40. FACIAL NERVE VII Cranial nerve Mixed Sensory component: Nervus intermedius of Wrisberg Nerve of 2 nd branchial arch

41. NUCLEAR CONNECTIONS Motor nucleus Superior salivatory nucleus Lacrimatory nucleus Nucleus of tractus solitarius

42. co 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. CENTRAL CONNECTIONS

43. FUNCTIONAL COMPONENTS Special visceral efferent * muscles of 2 nd branchial arch General visceral efferent * secretomotor Special visceral afferent * taste sensation from anterior 2/3rd of tongue and palate General somatic afferent * part of skin of the ear

44. COURSE The course of the nerve can be explained as : Intracranial course Extracranial course

45. INTRACRANIAL

46. EXTRACRANIAL Superficial to styloid process Pierces surface of parotid gland Runs forward Temporo -facial and Cervico -facial trunks Divides into 5 branches – ‘ pes anserinus ’

47. F acial canal Greater petrosal n. N. to stapedius Chorda tympani n. Below s tylomastoid foramen Posterior Auricular N. to Post. Belly of diagastric N. to Stylohyoid Face Temporal Zygomatic Buccal Marginal mandibular Cervical

48. CLINICAL TESTING Motor function : Ask the patient to raise eyebrows, wrinkle, close eyes tightly, show teeth, blow out cheek, whistle. Sensory function : Sweet, salty, sour, bitter taste. Secretory function : Lacrimation - Schirmer’s test - Nasolacrimal reflex Salivation Reflexes : Corneal reflex Stapedial reflex

49. APPLIED ANATOMY Supranuclear paralysis Nuclear paralysis Infranuclear paralysis

50. Nuclear Supranuclear

51. Infranuclear paralysis : according to site of involvement : Below stylo - mastoid foramen Facial canal Genu Internal acoustic meatus 3 4 2 1

52. BELL’S PALSY Idiopathic unilateral lower motor neuron paralysis of sudden onset. Sir Charles Bell Etiology : Inflammation or compression Symptoms

53. TREATMENT No standard course of treatment – symptomatic treatment Steroids - prednisolone 1mg/kg body wt for 10-14 days with a gradual tapering Anti-viral drug Analgesics Eye protection

54. GLOSSOPHARYNGEAL NERVE

55. GLOSSOPHARYNGEAL NERVE IX cranial nerve Mixed Post- trematic branch of 3 rd branchial arch Ganglia

56. NUCLEAR CONNECTIONS Nucleus ambiguus Inferior salivatory nucleus Spinal nucleus of trigeminal nerve Nucleus of tractus solitarius

57. FUNCTIONAL COMPONENTS Special visceral efferent : stylopharyngeus muscle. General visceral efferent : from inferior salivatory nucleus to otic ganglion, the postganglionic fibers supply parotid gland General visceral afferent : pharynx, posterior part of the tongue, carotid sinus, carotid body Special visceral afferent : posterior 1/3 rd of tongue, circumvalate papillae General somatic afferent : posterior 1/3 rd of tongue, tonsils, soft palate, oral part of pharynx

58. SVE GVE AFFERENT

59. COURSE 3-4 rootlets Medulla oblongata Root trunk Presents 2 ganglia Jugular foramen

60. Internal jugular vein and Internal carotid artery Internal and External carotid arteries Side of the pharynx Submandibular region Tonsillar Lingual

61. BRANCHES Tympanic Carotid Pharyngeal Muscular Tonsillar Lingual

62. CLINICAL TESTING Gag reflex Taste sensation

63. 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

64. VAGUS NERVE

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

66. NUCLEAR CONNECTIONS Nucleus ambiguus Dorsal nucleus of the vagus Nucleus of tractus solitarius Nucleus of the spinal nerve

67. FUNCTIONAL COMPONENTS Special visceral efferent : muscles of palate, pharynx & larynx General visceral efferent : thoracic & abdominal viscera. General visceral afferent : sensations from pharynx, larynx, trachea, oesophagus and abdominal & thoracic viscera Special visceral afferent : sensation of taste from the posterior most part of the tongue & epiglottis General somatic afferent : skin of the external ear

68. COURSE Medulla oblongata Jugular foramen Carotid Sheath Root of the neck Right/Left Vagus

69. COURSE Coeliac plexus Pulmonary plexus Oesophageal plexus Hepatic Gastric

70. 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

71. CLINICAL TESTING General sensation and Taste sensation Palatal reflex Gag reflex

72. APPLIED ANATOMY Paralysis of vagus nerve Irritation of recurrent laryngeal nerve Irritation of auricular branch in external ear Low grade stimulation of the auricular branch

73. HYPOGLOSSAL NERVE

74. HYPOGLOSSAL NERVE XII cranial nerve Motor Supplies all muscles of the tongue, except palatoglossus muscle

75. NUCLEAR CONNECTIONS Hypoglossal nucleus: elongated nucleus Functional components: General somatic efferent

76. COURSE 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 Carotid triangle

77. COURSE Digastric triangle Rests on hyoglossus muscle Deep to mylohyiod muscle Pierces genioglossus Substance of the tongue

78. BRANCHES Meningeal branch Descending branch Nerve to thyrohyoid and geniohyoid muscles Muscular branches

79. CLINICAL TESTING Patient asked to put out his tongue Check for : - deviation - abnormal movement - strength - wasting, tremor, fibrillation

80. APPLIED ANATOMY UPPER MOTOR NEURON LESION LOWER MOTOR NEURON LESION

81. CONCLUSION A clinicians’ thorough understanding of the anatomy of the cranial nerves and its clinical applications is essential for treatment planning as well as avoiding any untoward complications while treating the patients.

82. REFERENCES 1. Human anatomy BD Chaurasia . Vol 3, 4 th edition 2. Grays anatomy 39 th edition 3. Clinical neuroanatomy , Richard S. Snell 6 th edition 4. Essentials of Human Anatomy-Head & neck, A K Dutta 3 rd edition 5. A Regional Atlas of the human body, Clemente 6. Shafer’s text book of oral pathology 5 th edition 7. Handbook Of Local Anaesthesia, Malamed 5 th edition 8. Medicine for dental students, Allagapan 1 st edition 9. Burkets Oral medicine-10 th edition

83. XII COURSE 10- 15 rootlets emerge through medulla oblongata Runs laterally Joins to form 2 bundles Each pierce dura mater separately Lower part of the canal –unite to form a single nerve trunk Leaves skull through hypoglossal canal Passes vertically downward between internal jugular vein and internal carotid artey Appears in carotid triangle Passes forward to appear in the diagastric triangle Rests on hyoglossus muscle,deep to deep part of submandibualr gland,submandibular ganglion and lingual nerve Passes deep to mylohyiod muscle,pierces genioglossus Reaches substance of the tongue

84. Right vagus

85. Left vagus