Nerve supply of head and neck

The anatomy of the nerve supply of the head and neck has many significant applications in maxillofacial surgery. Understanding these important anatomic relations- variations enables surgeons to perform the surgical procedures safely. Knowledge of these concepts helps us to recognize the problems and complications as and when they occur and manage them accordingly.

1. GOOD MORNING

2. NERVE SUPPLY OF HEAD AND NECK (Department of Oral & Maxillofacial Surgery) PRESENTED BY: Dr. Samarth Johari (MDS 1 st Year) GUIDED BY: Dr. Gagan khare (Professor) 16-11-2018 (Friday)

3. CONTENTS Introduction Cranial Nerves Nuclei of Cranial Nerves Olfactory Nerve Optic Nerve Occulomotor Nerve Trochlear Nerve Trigeminal Nerve Abducent Nerve Facial Nerve Auditory Nerve Glossopharyngeal Nerve Vagus Nerve Accesssory Nerve Hypoglossal Nerve Conclusion Refernces

4. INTRODUCTION Peripheral nervous system – composed of 12 pairs of cranial nerves & 31 pairs of spinal nerves Emerging from brain stem Emerging from spinal cord

5. Somatic Nerves Defined as those afferent fibers that transmit stimuli from skin, special sense organs, voluntary muscles, tendons, ligaments & joints as well as those efferent fibres that activate voluntary, striated, skeletal musculature Visceral Nerves Defined as those afferent fibers that transmit stimuli from viscera as well as those efferent fibres that activate involuntary, smooth musculature of viscera, cardiac musculature & secretion of glands A nerve is a gross conduit made up of many fibers A fiber is a long process of a neuron of specific function

6. Note : The whole visceral motor outflow is placed in a separate category k/a Autonomic Nervous System because it acts “automatically” Major portion of head & neck is supplied by cranial nerves , a minor portion by upper cervical spinal nerves Fibers emerge from thoracic & upper lumbar segments of spinal cord k/a thoracolumbar outflow Fibers emerge directly from brain stem & from upper sacral segments of spinal cord k/a craniosacral outflow

7. There are 12 pairs of cranial nerves : Olfactory Optic Occulomotor Trochlear Trigeminal Abducent Facial Vestibulocochlear ( S tatoacoustic / Auditory) Glossopharyngeal Vagus Accessory Hypoglossal CRANIAL NERVES

8. Attachment of cranial nerves to the brain : a. Olfactory & Optic to forebrain b. Occulomotor & Trochlear to mid brain c. Trigeminal, Abducent , Facial & Vestibulocohlear to pons d. Glossopharyngeal, Vagus , Accessory, Hypoglossal to medulla oblongata

9. NUCLEI OF CRANIAL NERVES General Somatic Efferent (GSE) Nuclei Supply skeletal muscle of somatic origin Oculomotor Nucleus – Situated in mid brain at level of superior colliculus Its fibers enter occulomotor nerve & supplies extrinsic muscles of eyeball except lateral rectus & superior oblique Trochlear Nucleus – Situated in mid brain at level of inferior colliculus Supplies only superior oblique muscle through trochlear nerve

10. Abducent Nucleus – Situated in lower part of pons Supplies only lateral rectus muscle through abducent nerve Hypoglossal Nucleus – Lies in medulla Supplies 7 out of 8 muscles of tongue through hypoglossal nerve

11. Special Visceral Efferent (SVE)/Branchial Efferent Nuclei- Motor Nucleus of Trigeminal– Situated in upper part of pons Its fibers enter mandibular nerve & supplies muscles of mastication Nucleus of Facial Nerve – Situated in lower part of pons Supplies only muscles innervated by facial nerve Nucleus Ambiguus – Lies in medulla Supplies stylopharyngeus muscle (through glossopharyngeal nerve); muscles of soft palate, larynx & pharynx (through vagus & cranial part of accessory nerve)

12. General Somatic Afferent (GSA) Nuclei All related to trigeminal nerve Main or Superior Sensory Nucleus of Trigeminal Nerve – Lies in upper part of pons Spinal Nucleus of Trigeminal Nerve – Descends from main nucleus into medulla Reaches upper 2 segments of spinal cord Parts are : Pars caudalis – receives impulses of pain, temp. from forehead Pars interpolaris – receives impulses from cheek Pars oraris – receives impulses from around mouth

13. 3. Mesencephalic Nucleus of Trigeminal Nerve – Extends upwards from main sensory nucleus into mid brain Receive following fibers : Exteroceptive sensations (touch, pain, temp.) from skin of face, through trigeminal nerve & from part of skin of auricle through vagus & facial nerve Proprioceptive sensations from muscles of mastication through trigeminal nerve & from ocular, facial & lingual muscles, teeth & TMJ

14. General Visceral Efferent (GVE) Nuclei Give origin to preganglionic neurons that relay in peripheral autonomic ganglion postganglionic fibres arising in ganglion supply smooth muscles or glands Edinger – Westphal Nucleus – Lies in mid brain , close to occulomotor nucleus Supplies sphincter pupillae & ciliaris muscles via ciliary ganglion (through occulomotor nerve) Lacrimatory Nucleus – Lies in lower pons near salivatory nucleus Supplies lacrimal, nasal, palatal & pharyngeal glands via pterygopalatine ganglion (through facial nerve & its branch, greater petrosal nerve)

15. 3. Superior Salivatory Nucleus – Lies in lower part of pons Supplies submandibular, sublingual salivary glands via submandibular ganglion (through facial nerve & its chorda tympani branch) 4. Inferior Salivatory Nucleus – Lies just below superior nucleus in pons Supplies parotid gland via otic ganglion (through glossopharyngeal nerve)

16. 5. Dorsal Nucleus of Vagus – Extends into medulla Gives off fibres that passes through vagus nerve to be distributed to thoracic & abdominal viscera Special Somatic Afferent (SSA) Nucleus : Cochlear Nuclei – These are dorsal & ventral Receives impulses of hearing through cochlear nerve Vestibular Nuclei – Theses are superior, spinal, medial & lateral Receives fibers from semicircular canals, utricle & saccule through vestibular nerve

17. General Visceral Afferent (GVA) & Special Visceral Afferent (SVA) Nucleus : Nucleus of Solitary Tract or Tractus Solitarius – Only nucleus in this category Lies in medulla & extends into both its closed & open parts Lower part receives general visceral sensations : Through glossopharyngeal nerve from tonsil, pharynx, posterior part of tongue, carotid body & carotid sinus Through vagus nerve from pharynx, larynx, trachea, oesophagus & other thoracic & abdominal viscera

18. Upper part receives sensations of taste : From anterior 2/3 rd of tongue & palate except circumvallate papillae through facial nerve in its superior part From posterior 1/3 rd of tongue through glossopharyngeal nerve including circumvallate papillae in its middle part From posteriormost part of tongue & from epiglottis through vagus nerve in its inferior part

19. OLFACTORY NERVE Transmits sense of smell Branches arise from sensory cells of nasal mucosa, enter cranial cavity as olfactory fila through openings of cribriform plate of ethmoid bone Enter olfactory bulb singly Bulb is vestige of olfactory lobe of macrosmatic mammals (those animals with highly developed olfactory sense)

20. OPTIC NERVE Second pair of cranial nerve Nerve of visual sense Arise in ganglion cells of retina Enters cranial cavity through optic foramen

21. OCULOMOTOR NERVE Contains somatic & parasympathetic visceral efferent fibres Somatic fibres responsible for most of the extrinsic muscles of the eye Parasympathetic fibres relay in ciliary ganglion Postganglionic fibres arising from ciliary ganglion, enter eyeball & supply ciliary muscles or muscles of accommodation & sphincter of pupil Enters orbit through superior orbital fissure

22. TROCHLEAR NERVE Carries somatic fibres Supply superior oblique muscle of eyeball Passes through superior orbital fissure

23. TRIGEMINAL NERVE Consists of greater somatic sensory & small somatic motor portion Motor fibres supply masticatory muscles, tensor palate muscle, mylohyoid muscle, ant. belly of digastric & tensor tympani muscle Sensory fibers except proprioceptive fibers arise in semilunar ganglion & supply skin of entire face & mucous membrane of cranial viscera except pharynx & base of tongue Has 3 divisions : 1 st passes through superior orbital fissure, 2 nd through foramen rotundum & 3 rd through foramen ovale

24. Course of motor root & sensory root of trigeminal nerve :

25. Opthalmic Division : 1 st branch of V th cranial nerve Purely sensory & smallest of 3 divisions Supplies eyeball, conjunctiva, lacrimal gland, parts of mucous membrane of nose & paranasal sinuses & skin of forehead, eyelids & nose Divides into 3 main branches just before passing through superior orbital fissure – Nasocilliary Frontal Lacrimal – smallest branch & supplies lateral part of upper eyelid & small adjacent area of skin

26. Supplies ethmoidal & Sphenoidal Sinuses Contains sensory fibers that travel to eyeball via short ciliary nerves Supplies iris & cornea Supplies mucous membrane of anterior part of nasal septum & lateral wall of nasal cavity

27. Largest branch of ophthalmic division of trigeminal nerve Supplies upper eyelid, conjunctiva, lower part of forehead Sensory to upper eyelid & scalp till vertex

28. Maxillary Division : Arise from middle of trigeminal ganglion purely sensory Exits cranium through foramen rotundum (located in greater wing of sphenoid bone) Supplies – Skin – a. Middle portion of face b. Lower eyelid c. Side of nose d. Upper lip Mucous membrane – a. Nasopharynx b. Maxillary sinus c. Soft palate d. Tonsil e. Hard palate Maxillary teeth & periodontal tissues

29. Middle Meningeal Nerve – travels with middle meningeal artery to provide sensory innervation to duramater Zygomatic Nerve Pterygopalatine Nerve Posterior Superior Alveolar Nerve Middle Superior Alveolar Anterior Superior Alveolar Inferior Palpebral External Nasal Superior Labial

30. Zygomaticotemporal – sensory to skin on side of forehead Zygomaticofacial – supplies skin on prominence of cheek Orbital branch – supplies periosteum of orbit Nasal branch – important branch is nasopalatine nerve which supplies ant. part of nasal septum & floor of nose & enters incisive foramen to supply premaxillary region Palatine Branch – branches off into greater palatine & lesser palatine Pharyngeal Branch – mucous membrane of nasal part of pharynx, posterior to auditory tube Branches off in infratemporal fossa Supplies alveoli, periodontal ligaments, pulpal tissues of maxillary 3 rd , 2 nd &1 st molar (except mesiobuccal root of 1 st molar in 28% cases)

31. Supplies mesiobuccal root of maxillary 1 st molar, buccal soft tissue, periodontal ligaments, premolars Branches off 6-10 mm ahead of middle superior alveolar nerve Provides pulpal innervation to central incisors, lateral incisors, canine periodontal ligaments & alveolar bone

32. Supplies skin of lower eyelid Supplies skin on lateral aspect of nose Supplies skin & mucous membrane of upper lip

33. Mandibular Division : Largest branch of trigeminal nerve Mixed nerve with 2 roots – Large sensory – originates at inferior angle of trigeminal ganglion Smaller motor – arise in motor cells located in pons & medulla oblongata 2 roots emerge from cranium separately through foramen ovale Motor lies medial to sensory Unite outside skull to form main trunk of 3 rd division Remains united for 2-3 mm & then divides into small anterior part & large posterior part

34. Mandibular nerve supplies : Sensory root - Skin of temporal region, auricular region, external auditory meatus, cheek, lower lip, chin Mucous membrane of cheek, tongue (anterior 2/3 rd ), mastoid cells Mandibular teeth & PDL Alveolar bone of mandible TMJ Parotid gland Motor root – Masticatory muscles Mylohyoid muscle Anterior belly of digastric Tensor tympani Tensor vili palatini

35. Branches off into- nervus spinosus or meningel branch of V 3 (re-enters cranium through foramen spinosum along with middle meningeal artery t supply duramater & mastoid air cells), nerve to medial pterygoid (motor to medial pterygoid musle & gives small branches motor to tensor veli palatine & tensor tympani) Motor to masticatory muscles & sensory to mucous membrane of cheek & buccal mucous membrane of mandibular molars Branches off into- buccal , deep temporal, masseter, lateral pterygoid nerves Branches off into- auriculotemporal , lingual, inferior alveolar, mylohyoid , mental & incisive nerves

36. ABDUCENT NERVE Sixth pair of cranial nerve Consists of somatic motor fibers Supplies lateral rectus muscle of the eyeball Passes through the superior orbital fissure

37. FACIAL NERVE Consists of 2 nerves – facial nerve proper & intermediate nerve Consists of somatized motor fibers destined for muscles of facial expressions , including occipital, auricular, platysma, posterior belly of digastric & stapedius & stylohyoid muscles Contains proprioceptive sensory fibers (for deep sensitivity of face, taste sensations in anterior 2/3 rd of tongue & on palate) & preganglionic visceral efferent fibers (for lacrimal gland, sublingual; submandibular salivary glands & smaller glands of oral cavity Both the nerves emerge from brain at pontocerebral angle / pontomedullary junction in front of & medial to statoacoustic nerve

38. Nasal glands Palatine glands

39. Branches of facial nerve : Within the facial canal – Greater petrossal Nerve to stapedius Chorda tympani After emrging from stylomastoid foramen – Posterior auricular Nerve to posterior belly of digastric Terminal branches – Temporal (supplies frontal muscles, superior part of orbicularis oculi, corrugator, slender of nose) Zygomatic (supplies inferior part of orbicularis oculi) Buccal (upper buccal – muscles of upper lip & nose; lower buccal – buccinators & risorius muscle) Marginal mandibular (supplies muscles of lower lip & mental muscle) Deep cervical (supplies platysma muscle)

40. AUDITORY NERVE Also known as statoacoustic nerve & vestibulocochlear nerve Combination of vestibular & cochlear nerves arises from cochlea of labyrinth & transmits sensation of hearing Arises from semicircular canals, utriculus & sacculus of labyrinth & transmits sensation of position & movement

41. GLOSSOPHARYNGEAL NERVE Emerges from lateral surface of medulla oblongata & passes in front of vagus nerve through jugular foramen Contains motor fibers Motor supply to stylopharyngeus muscle & participates with vagus in supplying constrictors of pharynx & palatopharyngeus muscle Sensory supply to parts of tonsil, adjacent pharyngeal musosa , entire base of tongue

42. VAGUS NERVE Largest parasympathetic visceral nerve Contains both visceral & somatic fibers Sensory fibers arise from superior/jugular ganglion & inferior/ nodose ganglion & supply skin behind ear & lining of part of external acoustic meatus Motor supply to pharyngeal & laryngeal muscles Special sensory fibers serves sense of taste in region of epiglottis

43. ACCESSORY NERVE Consists of cranial & spinal portion & former is functionally a part of vagus nerve & in periphery, its fibers are indistinguishable from that of vagus Spinal part arises from upper 5 or 6 cervical segments of spinal cord, enters cranium through foramen magnum & join cranial accessory Exits cranium through jugular foramen along with glossopharyngeal & vagus nerve Supplies parts of sternocleidomastoid & trapezius muscles

44. HYPOGLOSSAL NERVE Twelfth cranial nerve Arises from medulla oblongata Leaves the skull through hypoglossal canal Motor supply to all intrinsic & extrinsic muscles of tongue except palatoglossus Has connections with upper cervical nerves

45. Joined by nerve that arises from the loop between 1 st & 2 nd cervical nerves Most of these fibers get detached from hypoglossal nerve as it reaches between internal & external carotid artey & constitutes the superior branch of the ansa cervicalis Joind by branches from 2 nd & 3 rd cervical nerves (inferior branch of ansa cervicalis ) From this loop branches off to supply omohyoid , sternothyroid , sternohyoid muscles Cervical fibers that do not get detached continue in the sheath of hypoglossal nerve & branches off into nerve for thyrohyoid & geniohyoid muscles

46. The anatomy of the nerve supply of the head and neck has many significant applications in maxillofacial surgery. Understanding these important anatomic relations- variations enables surgeons to perform the surgical procedures safely. Knowledge of these concepts helps us to recognize the problems and complications as and when they occur and manage them accordingly. CONCLUSION

47. Oral Anatomy by Sicher and DuBrul Gray’s Anatomy Oral & M axillofacial Surgery by Fonseca Atlas of Operative Maxillofacial Trauma Surgery by Springer Textbook of Human Anatomy by B.D.Chaurasia , Vol.3 Textbook of Human Embryology by Inderbir Singh REFERENCES

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