Persistent tympanic foramen: Prevalence, morphometry, and adjacent temporomandibular joint features on cone-beam CT

The persistent tympanic foramen (PTF) is a rare anatomical variation of the temporal bone and is of diagnostic significance due to its proximity to the temporomandibular joint (TMJ). Despite the widespread use of cone-beam computed tomography (CBCT), studies evaluating the prevalence and morphometric characteristics of PTF, as well as the distribution of anatomical variations and degenerative changes in adjacent temporomandibular structures in the TMJ, are limited.

To evaluate the presence, location, and dimensions of the PTF on CBCT images of patients with temporomandibular joint disorders (TMD) and healthy control subjects, to investigate and compare the distribution of anatomical variations in temporomandibular structures and degenerative changes in the TMJ in the presence and absence of PTF.

CBCT images of 230 individuals with TMD and 238 healthy controls were analyzed. For all participants, the presence, location, and diameter (mm) of the PTF, condylar morphology, as well as the presence and type of articular eminence pneumatization (AEP) and glenoid fossa pneumatization (GFP) were assessed and recorded. Additionally, in individuals with TMD, the type of pathology was recorded.

The frequency of PTF in the TMD group (37.8%) was found to be significantly higher than in the control group (23.5%) (< 0.001). In the TMD group, the frequency of PTF was higher in females. The most commonly observed condylar morphology in both individuals with and without PTF was the convex type (41.8%). The frequency of erosion was found to be significantly higher in individuals with PTF compared to those without PTF (p = 0046). PTF influenced the distribution of AEP (p = 0.007); however, no significant relationship was found between the distribution of GFP and the presence of PTF (p = 0.889).

The presence of PTF in approximately one-third of TMD patients and its close proximity to the TMJ are important in particularly invasive prosedures targeting the TMJ, and its presence should be evaluated by surgeons during the treatment planning phase.