Periorbital edema: This is a common and expected finding after a frontal craniotomy due to the surgical site's proximity to the orbit and the potential for swelling and fluid accumulation in the soft tissues around the eye.

Hemorrhage or hematoma: Bleeding in the orbit or surrounding tissues can cause swelling and should be considered, especially if there's a history of bleeding disorders or anticoagulant use.
Infection: Post-surgical infections can lead to swelling, redness, and warmth around the eye, and are a concern after any surgical procedure.
Allergic reaction: An allergic reaction to medications, sutures, or other materials used during surgery could cause eye swelling.

Cavernous sinus thrombosis: Although rare, this condition is potentially life-threatening and can cause eye swelling, among other symptoms, due to the formation of a blood clot in the cavernous sinus.
Carotid-cavernous fistula: An abnormal connection between the carotid artery and cavernous sinus can lead to eye swelling, proptosis, and other ocular symptoms, and requires prompt diagnosis and treatment.
Meningitis or cerebral abscess: Infection spreading to the meninges or brain tissue can have severe consequences, including death, and should be considered in the differential diagnosis of post-craniotomy complications.

Graves' orbitopathy: Although not directly related to the surgery, pre-existing Graves' disease could exacerbate or become apparent with the stress of surgery, leading to eye swelling and other orbital symptoms.
Orbital pseudotumor: A rare inflammatory condition of the orbit that can mimic infection or other conditions, causing swelling and other symptoms around the eye.