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Course

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Intracranial and Intratemporal

Segment Key Structures / Landmarks Main Branches Given Off
0 → 1. Intracranial (Pontomedullary junction → IAC) Exits brainstem at cerebellopontine angle; runs with CN VIII; enters internal acoustic canal (IAC) NA
1→ 2. Intratemporal – Labyrinthine Segment Narrowest segment; runs to geniculate ganglion 1. Greater Petrosal Nerve → pterygopalatine ganglion (PNS → lacrimal gland, nasal mucosa)
2. Chorda tympani (Taste + PNS salivary)
  1. Nerve to Stapedius (hyperacusis if damaged) | | 2 → 3. Intratemporal – Tympanic Segment | Passes above oval window, medial to incus; horizontal course | NA | | 4. Intratemporal – Mastoid Segment | Descends vertically; near stapedius | NA |

Extracranial

Segment Key Structures / Landmarks Branches Given Off
5. Extracranial (Stylomastoid Foramen) Depth: Posterior Belly of Digastric
Height: Traguls
Course: // Tympano-mastoid Suture, along retro-mandibular vein and stylo-mastoid artery 1. Posterior Auricular Nerve (occipital belly, auricular muscles)
2. Nerve to Posterior Belly of Digastric + Stylohyoid
6. Parotid Segment (Within Parotid Gland, between deep & superficial lobes)
Forms pes anserinus; divides into temporofacial & cervicofacial divisions Gives rise to 5 terminal branches: Temporal, Zygomatic, Buccal, Marginal Mandibular, Cervical

If you want, I can also add a “Lesion Pattern Table” (segment injured → specific deficits), which is high-yield for oral exams and EM calls.

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Internal Audiatory Meatus

CN VII

  1. Vestibular nerve
  2. Cochlear nerve

CN VIII

  1. Intermediofacial nerve
  2. Geniculate ganglion
  3. Chorda tympani

Function

Motor

  1. Muscles of facial expression

    Branch Muscles Innervated Motor Function Key Landmark (Close To)
    Temporal Occipitofrontalis, Orbicularis oculi (upper), Corrugator Eyebrow elevation, gentle eye closure Passes superior to zygomatic arch; at risk in brow lift, temporal dissection
    Zygomatic Orbicularis oculi (lower), Zygomaticus muscles Blinking, strong eye closure Runs over zygomatic bone, near lateral canthus; at risk in lower lid/lat canthal surgery
    Buccal Buccinator, Orbicularis oris, Levator labii, Risorius Smiling, blowing, lip movement Courses across masseter, enters buccal fat pad; at risk in parotid surgery and midface lifts
    Marginal Mandibular Depressor anguli oris, Depressor labii inferioris, Mentalis Lower lip depression, frowning Runs 1–2 cm below mandible angle, crosses facial artery/vein; at risk in submandibular, neck incisions
    Cervical Platysma Neck skin tension, assists lower lip Runs superficial in neck, below mandible; at risk in neck dissections, facelift flaps

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  2. Other Somatic Innervations

    Muscles Innervated Motor Function
    Stapedius muscle Dampens stapes vibration to protect inner ear; loss causes hyperacusis
    Posterior belly of digastric Elevates hyoid during swallowing; assists in opening the jaw
    Stylohyoid Elevates and retracts hyoid; helps initiate swallowing

  3. Parasympathetics

Sensory

  1. Somatosensory