Natural history of symptomatic cavernous malformations and results of surgery

Cavernous malformations are well known to somehow become more active after the first bleeding or initial seizure event. However, the real natural history of symptomatic cavernous malformations remains unclear, and the lack of information has obscured the treatment results. An investigation of the natural history of symptomatic cavernous malformations (s-CM) and the results of surgery was performed by distributing a questionnaire to large neurosurgical institutes across Japan. Data on 49 cases treated conservatively and 29 cases of surgery were collected. The distribution of patient age, sex and lesion location were comparable, however, the size of the lesion was larger in surgery group. Progression free survival, as determined using the Kaplan-Meier method, showed a marked difference in hemorrhage rate, which was greatly superior in the surgery cases. The annual rate of hemorrhage, as calculated from birth until the first event, was almost equal (1.7 and 1.8% in the conservative and surgical groups, respectively). However, rebleedings occurred in many of the conservatively treated cases, among whom the annual rate of hemorrhage was 10.2%/year after the first event and 19.7% after the second event. The high annual hemorrhage rate tends to persist at least for 5 years after the first event. In the surgical group, the rate was only 2.7%/year after the first event and after the surgery. Nevertheless, the neurological outcomes at the time of the last follow-up were quite similar in both groups, chiefly because of the complications that occurred as a result of surgical manipulations to the brainstem and basal ganglia. Cavernous malformations apparently become active after the first and second events have occurred. It is important to keep in mind that annual hemorrhage rates of 10%/year/case after the first event, and 20%/year/case after the second event are important part of the natural history of s-CM. Thus, the treatment results can be compared with these established rates of hemorrhage.