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Lower Motor Facial Asymmetry

Lower motor facial asymmetry occurs with a lesion at the: (1) pons [Figure 180.1 C]; (2) facial nerve [Figure 180.1 D]; (3) facial nerve branches [Figure 180.1 D]; or (4) depressor angularis oris muscle [Figure 180.1 F].

 

Figure 180.1.— Anatomical localizations of injuries in the facial motor system. T: thalamus; AC: internal auditory canal; FC: facial canal; SMO: styloidmastoid orifice; BB: buccal branch; MB: mandibular branch; TB: temporal branch; OOM: orbicularis oculi muscle; RM: risorius muscle; DAOM: depressor angularis oris muscle; BM: buccinator muscle; MM: mentoris muscle. Light blue line indicates components of the facial nerve that have ipsilateral (hence bilateral) cortical innervation; dark blue line indicates components of the facial nerve that have contralateral innervation. A: cerebral lesion above the thalamus; B: cerebral lesion below the thalamus and above the pons; C: pontine lesion; D: facial nerve; E: mandibular branch lesion; F: depressor angularis oris muscle.

 
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mandibular branch lesion mentoris muscle mandibular branch buccinator muscle absence of the depressor angularis oris facial nerve lesion buccal branch deprressor angularis oris muscle risorius muscle temporal branch stylomastoid orifice facial canal orbicularis oris muscle internal auditory canal pontine lesion cerebral lesion below the thalamus or midbrain lesion thalamus cerebral lesion above the thalamus Haymaker, 1969 Click on figure for animated labels. Pause pointer on different areas of the figure for labels. Figure must be centered.