Background and objectives: To compare the demographic, clinical, radiographic, scintigraphic and histologic differences between the two main types of mandibular condylar hyperplasia (MCH) and to suggest the method of therapeutic management based upon such findings.

Methods: This was a retrospective study 28 patients who presented with either vertical or horizontal forms of MCH and underwent surgical treatment. Every patient had a complete preoperative clinical and radiologic examination as well as a single photon emission computed tomography (SPECT) scan. A histologic analysis of each resected condyle was performed. These various parameters where then compared in the two patient groups.

Results: The mean age at time of the diagnosis was 25.8 years (range 12-50 years) and there were 22 females and 6 males. Nineteen patients had the vertical form of MCH and 9 had the horizontal form. Scintigraphic analysis showed moderate to extensive radionucleotide uptake in cases with rapid growth. Four cases had negative SPECT scan uptake and all were vertical forms. The horizontal forms had a rate of 89% of moderate to extensive uptake, that was higher than the vertical ones (63%). The histologic analysis showed both a global thickening of the cartilage cap and of the prechondroblastic cells layer and there was no difference between the two groups.

Conclusions: MCH is a pathologic condition affecting mainly young females and whose origin remains unknown. SPECT scans as an indicator of the rapidity of the disease progress seem are essential in assessing the condylar hyperplasia and to guide the therapeutic approach.

Key words: condylar hyperplasia; condylectomy; facial asymmetry