Background To describe epidemiological features of 565 Chinese patients with odontogenic keratocysts (OKC), to investigate possible prognostic factors related to recurrence, and to analyse features of recurrent OKC (rOKC). Material and Methods A retrospective chart review of 565 cases of OKC treated between 2003 and 2015 was undertaken. The probability of recurrence related to prognostic factors including large size, cortical perforation combined with involved teeth in the lumen of the cyst, inflammation, sites of the involved lesion, sex, and daughter cyst variables were analysed. The subsequent relapse of each OKC was compared. Results Patients ranged in age from 7 to 81 years (mean age, 28.4 years) and, of those affected, 66.9% were male and 33.1% were female. Mandibular OKC occurred in 63.01% and 36.99% occurred in the maxilla, 80.53% of patients had non-rOKC, 10.44% rOKC, and 9.03% had multiple OKC lesions. Enucleation with preservation of the involved teeth in the cystic lesion combined with cortical perforation was statistically associated with high recurrence rate, as were daughter cysts, and multilocular lesions. The number of recurrences and the average time (in years) to relapse decreased from the first relapse of OKC to the third relapse, and the difference was significant ( P <.05). Conclusions Preservation of the involved teeth combined with cortical perforation appeared to be a potential prognostic factor associated with high recurrence. The follow-up evaluation period for rOKC with ≥ 2 previous treatments should be shorter than for first-time rOKC. The decreasing average duration (years postoperatively) to relapse was related to the number of rOKCs, timing of relapse, and rOKC type. Key words: Keratocystic odontogenic tumor, risk of recurrence, involved teeth and cortical perforation, relapse, epidemiological features.

Study design: This is a retrospective hospital-based study. Objectives: The study aimed at a better understanding of the etiology, clinical presentation and treatment outcome of nontraumatic myelopathies in Ethiopian patients. Setting: Etiologies of nontraumatic myelopathies have not been evaluated extensively in most sub-Saharan African countries. The available studies in this region were conducted before the widespread clinical use of modern neuroimaging modalities. This study was conducted in Addis Abba, Ethiopia. Methods: We retrospectively analyzed medical files of patients with a diagnosis of myelopathy (age ⩾ 13 years) admitted or followed up at Tikur Anbesa Hospital between 1 January 2010 and 30 June 2013. Results: Records of 105 patients were analyzed. The male to female ratio was 1.7. The mean age was 38.5 years. Weakness, sensory symptoms (including sensory level), back pain and sphincter dysfunction were the dominant features. Etiologies were dominated by spinal tuberculosis (23.8%) followed by spinal cord neoplastic lesions (primary (10.5%) and secondary neoplasms 8.6%). Other important etiological causes were transverse myelitis (16.2%), degenerative cervical spondylotic myelopathy (15.2%), amyotrophic lateral sclerosis (4.8%) and neuromyelitis optica/multiple sclerosis (3.8%). The mortality rate was 9.5%. Among the patients who died, 40% had chest infection as a complication and 70% presented with complete weakness. Conclusion: Infections remain a major cause of spinal cord disease, and tuberculosis constitutes public health target for reducing the incidence of myelopathies. Early detection and treatment of complications may reduce the high rate of mortality and morbidity observed.