There was a lack of natural history of incidental brainstem cavernous malformations (CMs), hemorrhage of which would lead to severe neuropathies. The study aimed to evaluate the prospective hemorrhage rate and neurological outcome of the disease. This prospective cohort included patients with incidental brainstem CMs referred to our institute from 2009 to 2015. The diagnosis was confirmed based on the patients' complain, physical examination, and radiographic evidence. Clinical data were collected, scheduled follow-up was performed, and the independent risk factors were identified by multivariate analysis. This cohort included 48 patients (22 female, 45.8%). The median follow-up duration was 60.7 months, and 13 prospective hemorrhages occurred within 244.0 patient-years yielding an annual hemorrhage rate of 5.3%. The hemorrhage-free survival at 1 and 5 years was 91.6% and 80.6%. Age ≥ 55 years (hazard ratio (HR) = 8.59, p = 0.003), lesion size (per 1-mm increase) (HR = 3.55, p = 0.041), developmental venous anomaly (HR = 10.28, p = 0.017), and perilesional edema (HR = 4.90, p = 0.043) were independent risk factors for hemorrhage. Seven patients (14.6%) received surgical resection, and the other 41 patients remained under observation. Neurological function was improved in 22 patients (45.8%), unchanged in 19 (39.6%), and worsened in 7 (14.6%). Prospective hemorrhage (odds ratio = 14.95, p = 0.037) was the only independent risk factor for worsened outcomes. The natural history of incidental brainstem CMs seemed to be acceptable with improved/unchanged outcomes in most patients (85.4%). These results improved our understanding of the disease, and the future study of a large cohort was required to verify our findings.

中文翻译：

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在前瞻性观察队列中偶然诊断出的脑干海绵状畸形的自然史。

缺乏偶然的脑干海绵状畸形（CMs）的自然病史，其出血会导致严重的神经病。该研究旨在评估该疾病的预期出血率和神经系统预后。该前瞻性队列包括2009年至2015年转诊至我院的脑干CM偶发患者。根据患者的主诉，体格检查和X线影像学检查证实了诊断。收集临床数据，进行计划的随访，并通过多因素分析确定独立的危险因素。该队列包括48位患者（22位女性，占45.8％）。中位随访时间为60.7个月，在244.0患者年内发生了13例前瞻性出血，年出血率为5.3％。1年和5年无出血生存率分别为91.6％和80.6％。年龄≥55岁（危险比（HR）= 8.59，p = 0.003），病变大小（每增加1毫米）（HR = 3.55，p = 0.041），发育静脉异常（HR = 10.28，p = 0.017），和病灶周围水肿（HR = 4.90，p = 0.043）是出血的独立危险因素。7例（14.6％）接受了手术切除，其余41例仍在观察中。神经功能改善22例（45.8％），未改善19例（39.6％），恶化7例（14.6％）。预期出血（优势比= 14.95，p = 0.037）是导致预后恶化的唯一独立危险因素。大多数患者（85.4％）的偶然脑干CM自然病史似乎可以接受，但预后改善/未改变。这些结果增进了我们对疾病的了解，