Cranial Nerve Innervation of the Forehead and Eyelid
The facial nerve (cranial nerve VII) provides motor innervation to the forehead and eyelid muscles, while the ophthalmic division of the trigeminal nerve (cranial nerve V1) provides sensory innervation to these structures. 1
Motor Innervation: Facial Nerve (CN VII)
Peripheral or lower motor neuron facial nerve lesions cause ipsilateral facial paralysis with forehead involvement, which is the key distinguishing feature from supranuclear (upper motor neuron) lesions where the forehead is typically spared. 1
The facial nerve provides branchial motor innervation to all muscles of facial expression, including the frontalis muscle of the forehead and the orbicularis oculi muscle of the eyelid. 1
The facial nerve innervates the orbicularis oculi muscle on its deep surface, both at the temporal aspect and along the supraorbital rim, but no motor fibers extend into the upper eyelid itself. 2
When the facial nerve is damaged anywhere from its nucleus in the pons through its extracranial course, patients lose the ability to raise the eyebrow, close the eyelid, and wrinkle the forehead on the affected side. 1
Sensory Innervation: Trigeminal Nerve (CN V1)
The ophthalmic division (V1) of the trigeminal nerve provides all sensory innervation to the forehead, eyelids, and surrounding structures. 3, 4
Specific V1 Branches to the Forehead and Eyelid:
Supraorbital nerve (SON): Supplies sensation to the central and lateral forehead, distributed between 2/5 and 9/10 of the eye width lateral to the medial canthus. 5
Supratrochlear nerve (STN): Supplies sensation to the medial forehead and medial upper eyelid, distributed between -1/4 and -1/5 of the eye width medial to the medial canthus. 5
Infratrochlear nerve (ITN): Supplies sensation to the medial canthus and adjacent eyelid regions. 5
Lacrimal nerve (LN): Supplies sensation to the lateral upper eyelid and lacrimal gland, distributed between 3/5 and 13/10 of the eye width lateral to the medial canthus. 5, 6
Frontal nerve (FN): Terminal branches distribute to the eyelid margin between 1/6 and 2/5 of the palpebral fissure width lateral to the medial canthus. 5
Clinical Distinction
The vertically oriented nerves commonly identified in the preseptal upper eyelid are sensory nerves (V1), most commonly originating from the supraorbital nerve, not motor fibers from the facial nerve. 2 No anastomosis exists between the temporal branch of the facial nerve (VII) and the supraorbital nerve (V1). 2