The anterior ethmoidal nerve is a nerve which provides sensory branches to the nasal cavity. The nerve is the continuation of the nasociliary nerve after it enters the anterior ethmoidal foramen into the anterior ethmoidal air cells. The nasociliary nerve arises from the Ophthalmic division of the Trigeminal nerve (CN V) within the orbit. The anterior ethmoidal nerve arises only after the nasociliary has given off its four branches - 1) Ramus communicans to ciliary ganglion, 2) Long ciliary nerves, 3) infratrochlear nerve, 4) Posterior ethmoidal nerve.