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Good Morning Case – Patient, elderly H/o – Hypertensive, on antihypertensives, fall and unconscious, hyperpyrexia, deep coma, paralysis, pinpoint pupils. Brainstem • Introduction It is that part of neural axis which extends rostrally from cranial end of SC to caudal part of diencephalon. Brainstem: 3 major divisions •Midbrain •Pons •Medulla Ventral View of the Brain – Brain Stem The Brain Stem: General Functions – Produces automatic behaviors necessary for survival – Passageway for all fiber tracts running between the cerebrum and spinal cord – Important cranial nerve nuclei • 10 of the 12 pairs of cranial nerves attach to it • Heavily involved with the innervation of the face and head Learning Objectives • To know and learn about gross anatomy, both external and internal structure of pons • To know about its applied anatomy in brief PONS (Bridge) Pons • Developmentally part of hindbrain • Also called as Metencephalon • 2.5 cm -interconnecting the midbrain with medulla. • It does not, however, interconnect them Development of CNS Functions: • Relay station : cerebral cortex to the cerebellum. • Regulate breathing • Reticular formation - involved in sleep and arousal Gross Anatomy Ventral Pons dorsal view Locus ceruleus Median sulcus Medial eminence Sulcus limitans Facial colliculus Superior fovea Vestibular area FOURTH VENTRICLE Floor -RHOMBOID FOSSA Locus ceruleus Vestibular area Facial colliculus Hypoglossal triangle Median sulcus Sulcus limitans Medial eminence Superior fovea Striae medullaris Inferior fovea Vagal triangle Area postrema Pons - borders Entry and Exit of Cranial Nerves around the Pons: • Trigeminal nerve (5th ) • Abducent nerve (6th ) • The facial nerve (7th): a larger medial motor root smaller sensory root (intermediate nerve) • The vestibulocochlear nerve (8th ): vestibular division cochlear division. Entry and Exit of Cranial Nerves Transverse section of pons Tegmentum Basis pontis Internal structure •White matter Basis pontis Long motor tracts- corticospinal , Corticopontine and corticobulbar fibres Transverse - Pontocerebellar fibres Grey matter Pontine nuclei Internal structure………. Tegmentum Cranial nerve nuclei; sensory tracts Reticular formation MLF (nuclei of extra ocular muscle connections) T.S of pons Cross section at the level of facial colliculus Corticospinal tract PONS Cross section at the level of facial colliculus Medial lemniscus Trigeminal lemniscus Spinal lemniscus (Lateral spinothalamic tract) Lateral lemniscus Dorsal acoustic striae Ventral acoustic striae Auditory pathway Medial – MLF – adjustment of balance Tectospinal – spino visual reflex Rubrospinal – motor coordination of arm Pons ………… Pons ………… Intermediate - 1.Abducent 2.Facial nucleus (motor) ,superior salivatory,NTS -sensory Facial colliculus th th 7 th 7 th7 th th 7th 6 7 th 7 7 th 7 th 7 7thth 7th 7 6th 7th 7th FACIAL COLLICULUS 7thth 5th 7 th 7 th 7th7th7 NEUROBIOTAXIS Corneal reflex Lateral – Vestibular nuclei Inferior cerebral peduncle Cochlear nuclei Spinal nucleus & tract Pons ………… Cross section through upper part Mesencephalic nucleus Trigeminal nerve Jaw jerk reflex Pons ………… Blood supply • Ventral – pontine br • Dorsal - Anterior inferior cerebellar • Superior cerebellar artery • Venous drainage • Superior and inferior petrosal sinus Clinical aspects • Pontine haemorrhage : AICA syndrome • • • • • • Facial nucleus Solitary nucleus Cochlear nucleus Vestibular nucleus Trigeminal – spinal nucleus and tract Spinothalamic tract- contralateral pain, temperature • Reticular formation(sympathetic fibres) Tumor – cerebello-pontine angle •Facial palsy •Ataxia •Tinnitus •Vertigo •Deafness FOURTH VENTRICLE Millard gubler syndrome • Facial Nu – LMN palsy • Abducent Nu – Medial squint • Pyramidal tract – Contralateral hemiplegia Astrocytoma of pons • Usually occurs in childhood
