The present study, entitled "SHAM Study," is a prospective observational translational study aimed at investigating the molecular mechanisms underlying brain arteriovenous malformations (AVMs). In particular, the study seeks to explore the role of the Sonic Hedgehog (Shh) signaling pathway, which has recently been hypothesized as a potential key player in pathological angiogenesis and in the maintenance of the malformative nidus.

The study will be conducted through the analysis of brain tissues obtained exclusively as residual material from neurosurgical procedures performed for clinical indications. Under no circumstances will additional procedures be carried out or modifications made to the patients' therapeutic pathway for research purposes. Samples will include tissues from adult patients undergoing AVM resection and, as controls, non-pathological brain tissues derived from surgeries performed for other indications, such as drug-resistant epilepsy.

The methodological approach involves the isolation of endothelial cells from collected samples and their characterization using multi-omics techniques, including transcriptomic analysis, microRNA profiling, and quantitative proteomics. The resulting data will be integrated through advanced bioinformatics analyses in order to identify specific molecular patterns, altered pathways, and potential biomarkers. Particular attention will be given to the evaluation of Shh pathway activation and its interactions with other signaling systems involved in AVM pathogenesis.

The collected biological material may also be used, subject to specific informed consent, for preclinical studies conducted on animal models, with the aim of further investigating the identified pathogenetic mechanisms and assessing their functional relevance. Such activities will be carried out in compliance with current regulations on animal experimentation and subject to approval by the relevant authorities.

The primary objective of the study is to identify significant differences in gene expression between endothelial cells derived from AVMs and control brain tissue. Secondary objectives include the identification of integrated molecular profiles (RNA, microRNA, and proteins), the correlation of these profiles with patients' clinical and radiological characteristics, and the identification of potential therapeutic targets.

The study is designed so as not to entail additional risks for participants, as it is based exclusively on the use of biological material that would otherwise be discarded. All subjects will be enrolled only after providing written informed consent. Data will be processed in pseudonymized form in compliance with current regulations on personal data protection.

The total expected duration is 36 months, and the study is part of a targeted research project aimed at generating new knowledge with potential translational impact, laying the groundwork for the future development of targeted therapeutic strategies.

Study duration and number of patients:

The overall duration of the study will be 36 months. Enrollment will begin immediately after ethical approval and will be completed by month 24.

A total of 30-45 adult patients are expected to be enrolled, including 20-30 undergoing resection of brain arteriovenous malformations and 10-15 patients undergoing neurosurgical procedures for drug-resistant epilepsy, from whom non-pathological cortical tissue will be obtained.

Inclusion Criteria:

• Adult patients aged 18 years or older undergoing neurosurgical resection who provide written informed consent for research use of residual tissue.

Exclusion Criteria:

• Tissue with extensive necrosis or contamination, lack of valid consent, or known infectious agents that preclude safe handling.

Adults ≥18 years undergoing neurosurgical intervention with resection of AVM or non-pathological cortical tissue (controls).