Cranial Nerve Nuclei and coloumns😍

• Ipsilateral Bulbar Palsy
• Injury to Nucleus Ambiguus (LMN Lesion)
• Features
• (tongue spared)
• Dysphagia
• Dysarthria
• Nasal speech
• Loss of GAG reflex
• High risk of aspiration
• Wasting & fasciculations of palate/pharynx

a. Motor Nucleus of Trigeminal Nuclei (Pons)

• Supplies muscles of mastication

• SVE fibers (from 1st pharyngeal arch)

b. Sensory Nuclei

• Pars caudalis = main pain nucleus of trigeminal system.

• Reflex intact even in trigeminal neuralgia
• d/t intact Mesencephalic nucleus

• Muscle responsible for jaw jerk reflex
• Masseter (afferent & efferent via trigeminal)

Trigeminothalamic Pathway

• 5th Nuclei Ganglion

• Trigeminal Lemniscus (1st Order Neuron)

• Thalamus (VPM Nucleus)
• Relays signals to the Sensory Cortex [3, 1, 2].

• MTSL → Manage 3rd stage Labor

Relations of otic ganglion

• Topographical relation with V₃

• Mandelu Otta

• No synapse occurs here

Relations	Muscle
Anterior	Medial Pterygoid
Posterior	MMA
Lateral	V3 Nerve/ Mandibular N
Medial	TVP
Roof	Foramen ovale

Topographic nerve

• Trigeminal nerve (V)

• All ganglia are topographically connected to trigeminal nerve

• Carries postganglionic fibres in parasympathetic pathway

Roots of Otic Ganglion

• Parasympathetic (secretomotor root)
• From glossopharyngeal nerve (CN IX) via lesser petrosal nerve
• Relay in otic ganglion
• Postganglionic fibers travel with auriculotemporal nerve (branch of V3)
• Auriculotemporal nerve (V3) pass through without relay
• Supply parotid gland

• Sympathetic root
• From plexus around middle meningeal artery
• postganglionic fibers from superior cervical ganglion
• Pass through ganglion without synapse
• Vasomotor to parotid gland

• Mixed nerve

• Derived from 1st pharyngeal arch

• Largest and thickest branch of trigeminal nerve

• Root value: C₅, C₆, C₇, C₈, T₁

• Passes through foramen ovale (both sensory & motor components).

• All muscles supplied by V3 except
• Medial Pterygoid → Main trunk of 5th CN

• Mneumonic:
• Mandi (Mandibular) aytttulla oru auntie (Anterior ) always chew (mastication) → Was post (Posterior ) and sensitive (Sensory)
• She had a good aura (Auriculotemporal nerve) and good tongue (Lingual nerve) , but no lower teeth (Inferior alveolar nerve)

Divisions of Mandibular Nerve

• After passing through otic ganglion:
• Anterior division
• Posterior division

NOTE

Inferior Alveolar artery

• Runs with the inferior alveolar nerve to supply the lower teeth.

• Gives off:
• Mental Artery: Exits through the mental foramen to supply the chin.
• Mylohyoid branch: Supplies the mylohyoid muscle.

• Mnemonic: Use lower teeth () when Myran (Mylohyoid A) becomes mental (Mental A)

Structures Piercing Buccinator

1. Stenson's Duct / Parotid duct

2. Buccal br. Of Mandibular (V3) NV

3. Mucus glands of buccopharyngeal Fascia

NOTE

• Facial N supplies but does not pierce

Trismus (Lockjaw)

• Silent trismus → Medial pterygoid

• Trismus while yawning/opening mouth → Lateral pterygoid

Frey’s Syndrome:

• Gustatory sweating.

• Parasympathetic fibers of Parotid gland (ATN)
• communicates with GAN (most common)

• Stimulus to ATN → sweating in parotid region

• Investigation: Starch iodine test.
• Sprinkle starch and Paint iodine

• ATN fuses with:
• Ettan (Atn) likes gan
• GAN > Buccal nerve > Lesser occipital nerve

• Mx:
• First line: Botox and anti-perspirants
• TOC: Tympanic neurectomy.

• Prevention: 
• SCM flap/digastric muscle flap to cover parotid bed.

Facial Synkinesis

• Facial nerve anomalous regeneration

• Examples
• Crocodile tears (Bogorad syndrome):
• Facial N Injury before geniculate ganglion.
• Fibers anastomose with chorda tympani.
• Lacrimation when patient eats.
• Mouth retraction on eye closure
• orbicularis oculi aberrantly innervate orbicularis oris

• NOTE: Medial pterygoid plate : Doesn't give origin to pterygoid muscles.

• Protrusion
• Lateral > medial pterygoid
• Most apt answer is both
• Mnemonic: Teri (Both pterygoids) parayan jaw Protrude ()

• Opening the jaw/ depression of the mandible
• Lateral pterygoid muscle
• Remaining 3 muscles: Elevation of mandible
• Masseter > Temporalis & Medial pterygoid

• Side movement
• Alternate action of Lateral & Medial Pterygoids

• 7th cranial nerve.

Basic Features

• Mixed nerve
• Sensory root (nerve of Wrisberg).
• Motor root.
• Secretomotor root.

• Derived from the 2nd pharyngeal arch

• Exits from pons.

Nuclei

• Located in the pons

• Facial motor nucleus
• deep to the floor of the fourth ventricle

• Supranuclear palsy:
• UMN
• Lesion above pons.
• Forehead spared
• Innervation from bilateral cerebral cortex.

• Infranuclear palsy:
• LMN
• Lesion below pons.

Components and Functions

Course and Exit

• Loops around abducent nucleus forming internal genu
• → elevation in floor of 4th ventricle = Facial colliculus

• Exits brainstem at pontomedullary junction

• Enters internal acoustic meatus

• Longest interosseous course

• Exits skull via stylomastoid foramen

Course has 3 parts:

• Intracranial.

• Intratemporal.

• Extracranial.

Intracranial route:

• Exits nucleus.

• Turns around 6th nerve nucleus → Facial Colliculus

• Enters internal auditory canal.

Intratemporal route:

• Longest portion.

• Runs in bony canal (Fallopian canal).
• Absent in 50% of population.

• Most common dehiscence site:
• horizontal part.

Segments:

Meatal Segment (8–10mm):

• In internal acoustic meatus.

• Falciform crest:
• vertical Y-shaped crest.

• Bills bar:
• crest of bone.

Labyrinthine segment:

• Travels above vestibule.

• Anterior: Cochlea.

• Posterior: Semicircular canals.

• Shortest and narrowest segment.

• Most prone to ischemia and edema [Bell’s Palsy]

Tympanic segment:

• 1st genu/Geniculate ganglion:
• Landmark: Cochleariform process.

• Runs horizontally on medial wall.
• Above oval window
• below LSC

• 2nd genu:
• Landmark: Pyramid

Mastoid segment:

• Vertical segment.

• In mastoid bone.

• Exits from stylomastoid foramen.

• Iatrogenic facial palsy during mastoidectomy

Extracranial route:

• Enters parotid gland.

• Gives five terminal branches.

Branches

Terminal Branches in Parotid Gland

• Facial nerve divides into 5 branches in Patey's plane:
• Temporal
• Zygomatic
• Buccal
• Pierces buccinator muscle
• Marginal mandibular
• Cervical

• Supplies muscles of facial expression
• except LPS

Identification of Facial Nerve Trunk

• Cartilaginous Pointer
• It is a sharp triangular cartilage of the pinna.
• Facial nerve lies 1 cm deep, slightly anterior and inferior to this pointer.
• Acts as a landmark — it “points” to the nerve.

• Posterior Belly of Digastric Muscle
• Upper border (anterior border) is used for tracing.
• When traced posteriorly to its attachment at digastric groove,
→ Facial nerve lies between posterior belly and styloid process.

• Retrograde Dissection
• Identification method by tracing from distal branch backward.

Topodiagnosis

• Identifying lesions via clinical tests.

• Suprageniculate lesion:
• Affects lacrimation, stapedial reflex, taste, motor fibers.

• Infrageniculate lesion:
• Affects stapedial reflex, taste, motor fibers.

Clinical Points

• Testing:
• Ask patient to smile → observe angle of mouth deviation

• Rule of 17:
• CN VII lesion causes contralateral deviation of face
• Right CN VII lesion → deviation to left

• UMNL:
• Contralateral lower face paralysis

• LMNL:
• Ipsilateral complete hemifacial paralysis

• Facial colliculus lesion:
• LMNL + ipsilateral paralysis

Facial Palsy causes summary

• Most common cause:
• Idiopathic > Traumatic

• Iatrogenic facial palsy:
• Occurs during mastoidectomy
• Mastoid segment affected

Causes of B/L facial Nerve (diplegia):