What are the anatomical facial landmarks for the distribution of the Trigeminal Nerve (TN)?

Anatomical Facial Landmarks for Trigeminal Nerve Distribution

Three Main Divisions with Distinct Facial Territories

The trigeminal nerve distributes across the face through three major branches—ophthalmic (V1), maxillary (V2), and mandibular (V3)—each with specific anatomical landmarks that define their sensory territories. 1, 2

V1 (Ophthalmic Division) - Upper Face Territory

• Exits through the supraorbital foramen and provides sensory innervation to the upper facial region 2
• Covers the forehead, upper eyelid, eyebrow, and anterior scalp 3
• Innervates the frontal and ethmoid sinuses 3
• Supplies sensation to cornea, iris, ciliary body, lacrimal gland, and conjunctiva 3
• Extends to the dorsum of the nose (upper nasal bridge area) 3
• Provides sensory input to intracranial structures including tentorium cerebelli and portions of the dura mater 3

V2 (Maxillary Division) - Midface Territory

• Originates from the infraorbital foramen as its primary exit point 2
• Innervates the midface including the cheek region (malar area) 2
• Covers the lower eyelid and lateral nose 1
• Supplies the upper lip and upper teeth 4
• Extends to the maxillary sinus and portions of the nasal cavity 3
• Cheek sensory deficits specifically indicate V2 involvement and should prompt investigation of the infraorbital foramen, pterygopalatine fossa, and cavernous sinus 2

V3 (Mandibular Division) - Lower Face Territory

• Innervates the mandibular and temporal regions 2
• Covers the lower lip, chin, and lower teeth 4
• Extends to the anterior two-thirds of the tongue (sensory, not taste) 1
• Supplies the temporomandibular joint region 5
• Provides motor innervation to the muscles of mastication (masseter, temporalis, pterygoids) 1, 6
• The meningeal branch re-enters the cranium through foramen spinosum to supply middle cranial fossa dura 6

Clinical Anatomical Considerations

Orbital/Periorbital Distribution Patterns

• Plexiform neurofibromas commonly track along trigeminal nerve distribution, particularly affecting V1 and V2 territories 1
• Lesions extending across V1 and V2 distributions typically involve both eyelid and periorbital regions, potentially causing ptosis and amblyopia 1
• Isolated upper eyelid involvement (V1 territory) typically assumes an "S" shape configuration and rarely progresses to deeper structures 1

Imaging Correlation Points

• MRI is the preferred modality for investigating the full trigeminal nerve course from brainstem to peripheral branches 1, 2
• CT remains essential for evaluating bony foramina (supraorbital, infraorbital, foramen ovale, foramen spinosum) and skull base anatomy 1
• Multiple imaging planes are essential due to the complex three-dimensional branching patterns of the nerve 1

Common Pitfalls to Avoid

• Do not assume isolated facial symptoms represent only peripheral nerve pathology—the entire course from brainstem nuclei to peripheral branches must be considered 1, 7
• Tragus sensory changes require consideration of both V3 mandibular nerve and cervical nerve involvement depending on precise distribution 2
• Neurovascular compression imaging findings have 83-100% congruence with surgical findings, but both false-positives and false-negatives occur, so MRI is supportive rather than diagnostic 1