An assay is described that enables the simultaneous measurement of bilateral facial movements within zones relevant to facial nerve function. The assay allows the accurate quantitation of movement of the eyebrows, radix, lower eyelids, philtrum, mentum, and oral commissures relative to these points on the resting face. Global or region-specific facial nerve dysfunction is detectable using this assay, as shown in examples of patients having single branch facial nerve palsy and bilateral facial palsy (Möbius syndrome variant). Because facial movement is tested by region, with the remainder of the face relaxed, synkinesis can be detected when present. The assay has potential to be used as an adjunct to the presently used ordinal scales of facial nerve function, by allowing actual quantitation of region-specific facial movement. This feature may prove helpful in vector planning for reanimation procedures and may allow the tracking of functional responses after such procedures, thereby providing a measurement of their efficacy.