Anatomy of Trigeminal Nerve

8/2/2019 Anatomy of Trigeminal Nerve

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Anatomy of Trigeminal nerve


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Great sensory cranial nerve of head and face,motor nerve for muscles of mastication.

Four segments: Intra-axial

Cisternal

Interdural

Extracranial.


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Intra-axial segment

Main sensory nucleus in lateral pons. Spinal nucleus from pons to upper cervical cord (C2-C4 level). Mesencephalic nucleus from pons to midbrain.

Motor nucleus lies anteromedial to main sensory nucleus.


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Cisternal segment

Exits ventral pons as a larger sensory and

smaller motor root. Root entry zone (REZ)

Courses anterosuperiorly to the apex of petroustemporal bone through prepontine cistern.

Passes through an opening in dura (porustrigeminus) to enter Meckels cave.


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Interdural segment

Meckels cave CSFfilled space continuous

with prepontine cistern,

located at a depressionin petrous apex.

Nerve trunk expands toform Gasserian ganglion

from which branchesarise.


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Postganglionic

Ophthalmic nerve:

Courses in lateral cavernous sinus wall belowCN4.

Exits skull through superior orbital fissure.

Enters orbit, divides into lacrimal, frontal and

nasociliary nerves. Sensory innervation scalp, forehead, nose, globe.


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Maxillary nerve:

Courses in cavernous sinus lateral wall belowophthalmic nerve.

Exits skull through foramen rotundum. Traverses roof of pterygopalatine fossa.

Continues as infraorbital nerve.

Exits orbit through infraorbital foramen.

Sensory to cheek and upper teeth.


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Branches

Infraorbital nerve

Zygomatic nerve

Nasal Branches Superior alveolar nerves

Palatine Nerves

Pharyngeal nerve


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Mandibular nerve:

Exits directly from Meckel cave, passinginferiorly through foramen ovaIe into masticator

space. Carries both motor and sensory fibers.

Motor root bypasses ganglion, joins mandibularnerve as it exits through foramen ovale.

Divides into masticator (muscles of mastication)and mylohyoid nerves (mylohyoid and anterior

belly of digastric muscles).


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The mandibular nerve gives off the followingbranches:

From the main trunk of the nerve nervus spinosus(meningeal branch) medial pterygoid nerve

From the anterior division masseteric nerve deep temporal nerves buccal nerve lateral pterygoid nerve

From the posterior division auriculotemporal nerve lingual nerve inferior alveolar nerve motor branch to mylohyoid and anterior belly

of digastric muscles


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Imaging

Standardized brain MRI protocol- T1W spin

echo, proton density, T2W fast spin echosequences acquired in axial plane with turboSTIR sequence in coronal plane.

For trigeminal neuralgia- T1W 3D-FISP (fast

inflow with steady state precession). Pitfall: enhancement of ganglia and branches-

normal variant/ abnormal ?


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Axial T2W MR


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Coronal T1 C+ MR

Nonenhancing crescent-shaped trigeminal ganglionand the prominentperineural venous plexussuperior to it.


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Anatomy of Trigeminal Nerve

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