2.3. Questionnaire development

Three authors (AGB, AK, AT) reviewed the relevant literature on the management of CMs to identify potential controversies. A lead author (KNF) resolved any disagreements among the authors. None of the developers participated in answering the questionnaire. The authors identified several controversial topics, including i) potential treatment modifiers, ii) adjuvant pharmacotherapy, iii) additional diagnostic modalities required for surgical planning, iv) optimal treatment modality, v) treatment of the associated hemosiderin rim, vi) optimal treatment of the coexisting DVAs, vii) follow-up timetable, and viii) role of stereotactic radiosurgery. Furthermore, the developed management questions were stratified by patient age [children and young adults (<35 years), middle-aged patients (36–65 years), and elderly (>65 years)], clinical presentation (asymptomatic, after the first hemorrhage, and after the second hemorrhage), and lesional anatomic location (eloquent cortex, basal ganglia, brainstem and spinal cord). We considered in our consensus as eloquent cortical areas, the primary motor, somatosensory, visual, and auditory cortex, as well as the Broca's and the Wernicke's areas (Radiopaedia; Kahn et al., 2017). In total, the questionnaire included 17 semi-closed questions (supplementary material). For 13 questions, the respondent could give a short alternative answer, whereas for the remaining four questions, the respondent had the option of formulating a longer response/proposal. Among them, four questions allowed respondents to provide more than one possible answer.