FUNCTIONAL MASTICATORY EVALUATION IN HEMIFACIAL MICROSOMIA

The features of hemifacial microsomia with unilateral condylar hypopla sia in a 9-year-old female patient were analysed in a multidisciplinar y fashion. Cephalometric roentgenograms revealed malformation of the m andible, with the right condylar process being smaller than the left. In addition, the right maxillary alveolar process was underdeveloped. Closed view radiography with oblique lateral transcranial projection ( by modified Schuller's method) of the temporomandibular joint revealed an anterior dislocation of the condyle on the unaffected side. Comput ed tomography (CT) of the masticatory muscles demonstrated that the me dial pterygoid muscle on the affected side, unlike the other muscles, was larger than that on the unaffected side. The surface electromyogra phic activities of the temporal and masseter muscles and reduction of the maximum bite force on the affected side during clenching correspon ded with the CT findings. The hypertrophy of the medial pterygoid musc le on the affected side was considered likely to be a compensatory adj ustment to keep the mandible centred. A three-dimensional study of the movement of the mandible revealed that the condyle on the affected si de moved vertically and that the rotational centre was located antero- inferior to the condylar process during maximum jaw opening and closin g movements. These findings suggested lack of articular guidance. More over, the unaffected condylar process showed considerable backward mov ement during retrusion and ipsilateral excursion of the mandible. The mandibular head on the unaffected side showed obvious protraction duri ng all jaw movements, which might have induced the overgrowth of the c ondylar head on the unaffected side in this growing child.