A widened palpebral fissure has been regarded as one of the hallmarks of peripheral facial nerve palsy.1Contrary to this textbook description, however, peripheral facial nerve palsy often causes narrowing of the palpebral fissure on the affected side.2 This narrowing probably results from drooping of the upper eyelid because of weakness of the frontal muscle, but the anatomical basis has not been clear. We report here a bedside test which is very helpful in differentiating two types of palpebral narrowing—that is, one caused by weakness of the frontal muscle and the other by weakness of the levator palpebrae superioris.

Ptosis—palpebral narrowing—in the present communication was defined as drooping of the upper eyelid to cover one third or more of the cornea, according to the criteria described by Caplan.3Its severity was classified into three grades: (1) mild ptosis if the upper eyelid covered more than one third of the cornea, (2) moderate ptosis if it covered more than one half of the cornea, and (3) severe ptosis if the palpebral fissure was nearly closed.

The subjects were six patients with peripheral facial nerve palsy with palpebral narrowing but with no abnormality of the pupils and eye movements (five men, one woman; age range, 33 to 72 years; mean age 60.3 years) and five patients with oculomotor nerve palsy having ptosis but without facial palsy (two men, three women; range 45 to 64 years; mean age 59.5 years). In all subjects peripheral facial nerve palsy or oculomotor nerve palsy developed acutely or suddenly. The palpebral narrowing …