Which cranial nerve mediates sensation of the forehead area?

Sensation of the Forehead Area is Mediated by the Ophthalmic Division (V1) of the Trigeminal Nerve

The sensation of the forehead area is mediated by the ophthalmic division (V1) of the trigeminal nerve (cranial nerve V). 1, 2

Trigeminal Nerve Anatomy and Sensory Distribution

The trigeminal nerve (CN V) is the largest cranial nerve and is divided into three main divisions:

1. Ophthalmic division (V1):

   • Provides sensory innervation to:
     • Forehead and scalp up to the vertex 2
     • Upper eyelid
     • Cornea and conjunctiva
     • Dorsum of the nose
     • Frontal sinuses
     • Tentorium cerebelli and dura mater 2

2. Maxillary division (V2):

   • Provides sensory innervation to:
     • Lower eyelid
     • Upper lip
     • Lateral portions of the nose
     • Part of the oral cavity

3. Mandibular division (V3):

   • Provides sensory innervation to:
     • Lower lip and chin
     • Temporal region
     • Anterior two-thirds of the tongue
     • Lower teeth and gums
   • Also contains motor fibers that innervate the muscles of mastication 1

Anatomical Course of the Ophthalmic Division

The ophthalmic division (V1) follows this anatomical pathway:

• Originates from the trigeminal ganglion (also called the Gasserian or semilunar ganglion) 3
• Exits the cranium through the superior orbital fissure 3
• Enters the orbit to innervate the globe and skin of the forehead area 3
• Branches into:
  • Frontal nerve (further dividing into supratrochlear and supraorbital nerves)
  • Nasociliary nerve
  • Lacrimal nerve

Clinical Significance

Understanding the sensory distribution of the trigeminal nerve is clinically important for:

1. Diagnosing trigeminal neuralgia: Pain in the distribution of one or more branches of the trigeminal nerve 4

2. Localizing lesions: Sensory loss or pain in the forehead specifically points to involvement of the ophthalmic division (V1) 2

3. Differential diagnosis: Conditions affecting the ophthalmic division can cause referred pain to the forehead area 5

4. Imaging considerations: When evaluating forehead sensory abnormalities, MRI is the preferred imaging modality to visualize the entire course of the trigeminal nerve from brainstem to peripheral branches 1, 4

Diagnostic Approach for Forehead Sensory Abnormalities

When evaluating sensory abnormalities in the forehead area:

• Test sensation in all three divisions of the trigeminal nerve to determine if the deficit is isolated to V1
• Compare sensation between the affected and unaffected sides
• Consider MRI with contrast to evaluate the entire course of the trigeminal nerve if pathology is suspected 1

Understanding that the ophthalmic division of the trigeminal nerve mediates forehead sensation is fundamental for accurate neurological examination and diagnosis of conditions affecting this region.