The incidence and influence of abnormal styloid conditions on the etiology of craniomandibular functional disorders.

This study aimed to examine the incidence and influence of craniomandibular functional disorders caused by abnormal styloid-stylohyoid chains. Seven hundred sixty-five patients with temporomandibular joint (TMJ) disorders were divided into two groups (with and without radiographically visible abnormal styloid conditions). In the group with abnormal stylohyoid conditions, the etiology of TMJ disorders was further subdivided into poly-, oligo- and monoetiological factors, and, after this classification, evaluated regarding a clear, possible or unlikely involvement of abnormal stylohyoid conditions in TMJ disorders. One hundred thirty-six out of 765 patients presented abnormal styloid-stylohyoid chains. One hundred five of the patients (77.2%) demonstrated polyetiological causes of TMJ symptoms with an unlikely involvement of the abnormal styloid-stylohyoid chain. Twenty-nine of the patients (21.3%) showed oligoetiological causes with possible involvement of the abnormal styloid-stylohyoid chain. In two patients (1.5%), the abnormal styloid conditions showed up as the only definite cause of TMJ symptoms (monoetiological). Detailed knowledge of variations and possible effects of suprahyoid structures is important for an accurate diagnosis of TMJ disorders. All in all, the incidence of a stylohyoid involvement in TMJ disorders is very low. However, after an initial subdivision into abnormal and normal stylohyoid conditions, the incidence of pathological stylohyoid chains gains significant importance in the etiology of TMJ disorders.