Brainstem and Cranial Nerves PDF

Brainstem and Cranial Nerve Dr. Fairus Ahmad Dept of Anatomy Faculty of Medicine, UKM Specific objectives At the end of the lecture, the student should be able to:  Describe the different parts of the brainstem.  State the twelve pairs of cranial nerve.  Classify the cranial nerve according to t...

Brainstem and Cranial Nerve Dr. Fairus Ahmad Dept of Anatomy Faculty of Medicine, UKM Specific objectives At the end of the lecture, the student should be able to:  Describe the different parts of the brainstem.  State the twelve pairs of cranial nerve.  Classify the cranial nerve according to their organization.  Apply the clinical significance of the cranial nerves lesion. Objective 1 Describe the different parts of the brainstem. Intro - Major brain subdivision Prosencephalon Mesencephalon Rhombencephalon Forebrain Midbrain Hindbrain Diencephalon Telencephalon Metencephalon Myelencephalon Thalamus & Cerebrum Pons & cerebellum Medulla oblongata hypothalamus Brainstem connecting part between forebrain and spinal cord occupies the posterior cranial fossa 3 Parts (below upwards) - Medulla oblongata - Pons - Midbrain  Parts of Brainstem Midbrain Midbrain Pons Pons Medulla Oblongata f. Netter f. Netter Anterior view of brainstem Posterior view of brainstem  Brainstem Main function Cerebral - Contains cranial nerve nuclei (CN Midbrain aqueduct III - XII) - Contains vital centers (for Pons Fourth respiration & cardiac activities) ventricle - Conduit for ascending & Medulla descending tracts oblongata Arterial supply to brainstem Basilar artery Pontine a. Labyrinthine a. AICA Superior cerebellar a. Posterior cerebral a. (PCA) Vertebral artery Anterior & posterior spinal a. PICA  Sup. cerebellar artery Post. cerebral artery Basilar artery Pontine arteries Ant. inf. cerebellar artery Ant. spinal artery Post. inf. cerebellar artery Vertebral artery Brain area Arteries Medulla oblongata Vertebral a., anterior spinal a., PICA Pons Basilar a., pontine a., superior cerebellar a., AICA Midbrain PCA, superior cerebellar a., basilar a. Medulla oblongata Midbrain Fourth Pons ventricle Medulla oblongata Extend from just above the origin of C1 nerve – pons - 3 cm length, 2 cm wide External features: anterior view Anterolateral sulcus Pyramid Olive - Underlying corticospinal fibres - Tapers inferiorly (most fibres decussated) - Underlying inferior olivary nucleus Posterolateral sulcus Decussation of pyramids Anterior median fissure External features: anterior view Glossopharyngeal CN IX Hypoglossal CN XII Vagus CN X C1 nerve, anterior root Accessory CN XI External features: lateral view Inf. cerebellar peduncle Glossopharyngeal CN IX Pyramid Olive Hypoglossal CN XII Vagus CN X Anterolateral sulcus Accessory CN XI C1 nerve, anterior root Posterolateral sulcus External features: posterior view Opened part: Sulcus limitans Median sulcus Closed part: Striae medullaris Gracile & cuneate tubercles Hypoglossal trigone Nuclei gracilis & cuneatus Vagal trigone Posterior median fissure Ascending dorsal column - Fasciculus gracilis - Fasciculus cuneatus Arterial supply of medulla oblongata Ant. spinal artery Posterior inferior cerebellar artery Vertebral artery Pons Midbrain Fourth Pons ventricle Medulla oblongata Bridge: connecting both cerebellar hemispheres - 2.5 cm long External features: anterior view Trigeminal CN V 1 large sensory root & 1 small motor root Basilar groove Lodges basilar artery Abducens CN VI Middle cerebellar peduncle Facial CN VII Vestibulocochlear CN VIII External features: lateral view Trigeminal CN V Middle cerebellar peduncle Abducens CN VI Vestibulocochlear CN VIII Facial CN VII External features: posterior view Sup. cerebellar peduncle Mid. cerebellar peduncle Medial eminence Facial colliculus CN VII nerve root winds Sulcus limitans around CN VI nucleus Median sulcus Area vestibuli Underlying vestibular nuclei Arterial supply of pons Superior cerebellar artery Basilar artery Pontine arteries Anterior inferior cerebellar artery Midbrain Cerebral Midbrain aqueduct Pons Medulla oblongata Connects pons & cerebellum to the forebrain Ascends through opening of tentorium cerebelli External features: anterior view Crus cerebri Interpeduncular fossa Posterior perforated substance Oculomotor CN III Innervate extraocular muscles (except lateral rectus & superior oblique) External features: posterior view Superior brachium Superior colliculi Superior colliculi  lateral geniculate body Centre for visual reflexes & optic tract Inferior colliculi Lower auditory centres Inferior brachium Inferior colliculi  medial geniculate body Trochlear CN IV Extraocular muscle (superior rectus) Arterial supply of midbrain Sup. cerebellar artery Post. cerebral artery Basilar artery Objective 2 State the twelve pairs of cranial nerve. Cranial nerves - Definition Cranial nerves - nerves that emerge directly from the brain & brainstem Spinal nerves - nerves that emerge from segments of the spinal cord Cranial nerves - Features Each cranial nerve is paired and is present on both sides. There are twelve cranial nerves pairs Each are assigned Roman numerals I–XII The numbering of the cranial nerves is based on the order in which they emerge from the brain, front to back Cranial nerves 12 pairs peripheral nerves of the brain and brainstem Inferior view of the brain Inferior view of brain  Olfactory nerve (I) (II) (III) (IV) (V) (VI) (VII) (VIII) (IX) (X) (XI) (XII) Sensory Motor Mixed PS Comp Objective 3 Classify the cranial nerve according to their organisation. Organisation Mixed (both Cranial nerves Entirely sensory Entirely motor sensory & with (special senses ) motor) parasympathetic outflow III, IV, VI, XI, I, II, and VIII and XII V, VII, IX, and X III, VII, IX, and X  Olfactory nerve (I) (II) (III) (IV) (V) (VI) (VII) (VIII) (IX) (X) (XI) (XII) Sensory Motor Mixed PS Comp Cranial Nerves Objective 4 Apply the clinical significance of the cranial nerves lesion. Organisation Mixed (both Cranial nerves Entirely sensory Entirely motor sensory & with (special senses ) motor) parasympathetic outflow III, IV, VI, XI, I, II, and VIII and XII V, VII, IX, and X III, VII, IX, and X Lesions of olfactory nerve (CNI) Loss of sense of smell (anosmia) Causes  fracture of anterior cranial fossa CSF rhinorrhea  cerebral tumour of frontal lobe  N Lesions of T 1. circumferential blindness optic nerve - optic neuritis 2. total blindness -complete (CNII) section of optic nerve 3. nasal hemianopia - section of optic chiasma at lateral side 4. bitemporal hemianopia - sagital section of chiasma ( pituitary tumour ) 5,6,7. Contralateral homonymous hemianopia - section of OT, OR, VC on one side N - nasal eye field T- temporal eye field Lesions of vestibulocochlear nerve (CNVIII)  Disturbance of cochlear nerve function - Deafness and tinnitus  Disturbance of vestibular nerve function - Vertigo and nystagmus Organisation Mixed (both Cranial nerves Entirely sensory Entirely motor sensory & with (special senses ) motor) parasympathetic outflow III, IV, VI, XI, I, II, and VIII and XII V, VII, IX, and X III, VII, IX, and X Lesions of oculomotor nerve (CNIII) drooping of the eyelid (ptosis) pupils - fixed & dilated pupils ( unresponsive to light , accomodation ) diplopia fully abducted eye eye looks downward Lesions of trochlear nerve (CNIV)  double vision while looking straight downward  eye looks medially and downward Lesions of abducens nerve (CNVI) lesion of the nucleus in the pons compression of the nerve by aneurysm of ICA or cavernous sinus thrombosis  inability to move the eye laterally  convergent strabismus (unopposed action of MR) Lesions of accessory nerve (CNXI) Cranial accessory Spinal accessory Origin Medulla oblongata C1-C5 segments Functions Phonation, deglutation Movement of head and Shrugging of shoulder Lesion Dysarthria, dysphagia Weakness in turning the head to opposite side and drooping of the shoulder Lesions of hypoglossal nerve (CNXII)  Lesion in LMN lesion  tongue deviate towards the paralyzed side when protruded Organisation Mixed (both Cranial nerves Entirely sensory Entirely motor sensory & with (special senses ) motor) parasympathetic outflow III, IV, VI, XI, I, II, and VIII and XII V, VII, IX, and X III, VII, IX, and X Lesions of trigeminal nerve (CNV) loss of general sensation from face, mucous membrane of oral and nasal cavities loss of corneal reflex (afferent limb – CNV) flaccid paralysis of muscles of mastication deviation of jaw to the weak side (unopposed action of opposite lateral pterygoid muscle) partial deafness to low-pitched sound (paralysis of tensor tympani) Lesions of facial nerve (CNVII) UMN lesion of facial nerve Facial nucleus Facial nerve Lesions of facial nerve (CNVII) LMN lesion of facial nerve Facial nucleus Facial nerve Lesions of glossopharyngeal nerve (CNIX) isolated lesions are rare results in loss of sensation in post 1/3rd of tongue including taste unilateral loss of gag reflex  Afferent run with IX nerve  Efferent run with IX and X nerves difficulty in swallowing Lesions of vagus nerve (CNX) Cranial nerves lesion THANK YOU Acknowlegement: AP Dr. Teoh Seong Lin AP Dr. Elvy Suhana Mohd Ramli