Platybasia as a Skeletal Marker for Congenital Velopharyngeal Insufficiency

Objective: There is an integral relationship between the skull base, the velopharynx and the facial skeleton including the palate. The exact patterns of cranial-base angle in patients suffering from hypernasal speech i.e. velopharyngeal insufficiency (VPI), with or without clefts are still unclear. This study investigates the platybasia phenomenon in patients suffering from VPI, and evaluates the possible high prevalence of platybasia among them. Methods: Patients suffering VPI (n=366) from the Cleft Palate Center, Sapir Medical Center, Kfar Saba, were evaluated by means of chephalometric analysis. Three landmarks identified cranial base angle, were digitized from lateral cephalograms of each patient, and compare with corresponding data of healthy subjects with normal speech (n=126), the control group. The VPI group was further subdivided into 5 subgroups according to palate anomalies. Results: Platybasia, i.e. obtuse cranial-base angle, was identified in 104 subjects (28.4%) of the VPI patients, and only in 3 subjects (2.4%) of the control group. The platybasia phenomenon was found to be significantly higher (p<.001) in the VPI group than in the normal controls. The distribution of platybasia was also investigated in the five subgroups and found to be 16.7% in the cleft palate and lip patients, 20.3% in the cleft palate, 28.8% in the submucous cleft palate patients, 33.7% in the occult submucous cleft palate patients and 40.3% in the non-cleft patients with VPI. Conclusions: Our finding suggests a high prevalence of the platybasia phenomenon among patients suffering VPI. This anatomic feature serves as a phenotypic marker which enables differential diagnosis of patients suffering from congenital VPI. Platybasia may also help in explaining the etiological factor of VPI in non-cleft patients. The slant of the cranial base causes alteration of the nasopharyngeal space and size. The enlarged nasopharyngeal space causes difficulties in achieving complete velopharyngeal closure, resulting in VPI and hypernasality.