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Cranial Nerves and Foramina Yatharth Verma Intercalating Medical Student University of ManchesterSkull Base • Location of cranial foramina associated with cranial nerves • Generally divided into 3 fossa: • Anterior cranial fossa • Middle cranial fossa • Posterior cranial fossaForamina Cranial Nerves • I – Olfactory Sensory Some • II – Optic Sensory Say • III – Oculomotor Motor Money • IV – Trochlear Motor Matters • V – Trigeminal Both But Motor My • VI – Abducent • VII – Facial Both Brother • VIII – Vestibulocochlear Sensory Says • IX – Glossopharyngeal Both Big • X – Vagus Both Brains • XI – Spinal accessory Motor Matter • XII - Hypoglossal Motor MoreCN I • Olfactory Nerve • Responsible for sense of smell • Exits through cribriform plate to synapse with olfactory bulb • Olfactory tract divides into lateral and medial stria • Lateral stria – Uncus of temporal lobe (primary olfactory cortex) • Medial stria – medial plane of anterior commissureCN II • Optic Nerve • Responsible for vision • Passes through optic canal • Axons from retinal ganglion cells converge • At chiasm, medial fibres decussate, lateral fibres remain ipsilateral • Fibres synapse via optic tract with lateral geniculate nucleus • From here optic radiation transmits signals to visual cortexCN III • Oculomotor Nerve • Motor and parasympathetic functions • Originates from Oculomotor nucleus in midbrain below PICA and above SCA • Pierces dura to enter cavernous sinus • Exits via superior orbital fissure • Forms superior and inferior branchesCN IV • Trochlear Nerve • Purely motor function • Only cranial nerve to originate from posterior brainstem (dorsal midbrain) • Loops around midbrain and pierces the tentorium cerebelli • Runs through lateral wall of cavernous sinus • Exits through superior orbital fissureCN VI • Abducent Nerve • Purely motor function • Arises at medullopontine sulcus • Travels anteriorly through pontine cistern • Pierces the dura to enter canal of Dorello • Enters and travels through cavernous sinus • Exits through superior orbital fissureCN V • Trigeminal Nerve • Sensory and motor supply • Nerve emerges from pons and travels to Meckel’s cave where the sensory root expands to form trigeminal ganglion • Three main branches emerge from the ganglion: • V 1 Ophthalmic – Superior Orbital Fissure • V 2 Maxillary – Foramen Rotundum • V 3 Mandibular - Foramen OvaleCN VII • Facial Nerve • Sensory, Motor and parasympathetic supply • Emerges as two roots (1 sensory and 1 motor) from lateral surface of brainstem between pons and medulla at CP angle • Enters internal acoustic meatus • Once it enters the facial canal in the petrous temporal bone, the roots combine to form the facial nerve • Facial nerve exits skull through stylomastoid foramenCN VIII • Vestibulocochlear nerve – 2 parts • Sensory supply • Emerges at CP angle • Exits cranial cavity through internal acoustic meatus • Separates into 2 nerves • saccule and semi circularle, canals • Cochlear nerve to spiral organ of CortiCN IX • Glossopharyngeal Nerve • Sensory, Motor and parasympathetic functions • Emerges as several rootlets at the posterior lateral sulcus of the medulla • Passes through posterior cranial fossa • Exits skull through the jugular foramen • Descends down the neck anterolateral to the ICACN X • Vagus Nerve • Sensory, Motor and parasympathetic functions • Arises at lateral aspect of medulla just below the glossopharyngeal between the olive and the inferior cerebellar peduncle • Travels laterally and exits the cranium through the jugular foramen • Passes down the neck between the ICA and the IJV within the carotid sheathCN XI • Accessory Nerve • Motor function only • Has both cranial roots (medulla) and spinal roots (C1-C5) • Cranial rootlets emerge at posterior border of olive on the ventrolateral surface of the medulla • Spinal rootlets emerge from respective spinal levels and travel up through the foramen magnum • Merge to form single nerve and travel laterally through the cerebellomedullary cistern • Exits skull through the jugular foramenCN XII • Hypoglossal Nerve • Purely motor function • Emerges from the anterolateral sulcus of the medulla as several rootlets • Travel laterally in the posterior cranial fossa • Merge into 1 nerve within the hypoglossal canal • Exits via the hypoglossal canal • Contributes to ansa cervicalis • Descends medial to the angle of mandible and turns anteriorly • Passes between mylohyoid and hyoglossus muscle and enters the tongueWhich cranial nerve exits through foramen rotundum? II III V 1 V 2 IVHow many cranial nerves exit through the jugular foramen? 2 3 1 0 4Which of the following nerves provides motor supply? CN I CN II V1 V2 V3Which of the following muscles is not innervated by the facial nerve? Tensor tympani Orbicularis oris Buccinator Stapedius FrontalisA tumour located at the CP angle is likely to compress which cranial nerves? CN II only CN VII and CN VIII CN VII only CN V and CN VI CN X only Thank you for your attention! Any Questions? Email: yatharth.verma@postgrad.manchester.ac.uk