Neurosurgery for psychiatric disorders in the modern era: protocol for a systematic review and meta-analysis of surgical characteristics and patient outcomes

Background: Neurosurgery for mental disorder (NMD), colloquially known as ‘psychosurgery’, a branch of neurosurgery defined by the World Health Organization (WHO) as the selective surgical removal or destruction of neural pathways to influence behaviour, has evolved significantly since its inception in the 1930s. NMD has a profound yet controversial history, from Antonio Egaz Moniz, founder and pioneer of the prefrontal leucotomy and cerebral angiography. Globally, the acceptance and applications of NMD vary significantly: in some regions, it is a well-established part of the therapeutic arsenal, while in others it remains controversial or underutilized. Yet, research on modern applications of NMD remains limited, indicated in a range of psychiatric disorders in cases where conservative or pharmacological treatments have been deemed intractable. These comprise treatment-resistant depression, anxiety, anorexia nervosa, obsessive-compulsive disorder, bipolar disorder, schizophrenia, and Tourette's syndrome. Historically, NMD stipulated lobotomies where corticectomy was practiced. Now, deep brain and vagus nerve stimulation, gamma knife radiosurgery, stereotactic radiosurgery, and focused ultrasound have revolutionised NMD. Hence, this systematic review aims to comprehensively evaluate the current psychosurgery landscape from 2000 onwards, comparing patient demographics, functional outcomes, complication and mortality rates between different types of psychosurgeries. Methods: A systematic review and meta-analysis will be performed between 2000 to 2024, adhering to the PRISMA-P guidelines alongside the Cochrane Handbook of Systematic Reviews of Interventions. Search databases used were PubMed/MEDLINE, EMBASE, GlobalHealth, APA PsycInfo, and Scopus. Search terms, alongside Boolean operators, were employed, examining mental health conditions eligible for NMD and procedures indicated. We will also review the reference sections of each eligible article. Inclusion criteria for this review include studies written in the medium of the English language involving neurosurgery for psychiatric disorders between 2000 to 2024. Studies were only considered eligible to be included if they had complete individual patient data. Two independent reviewers will screen the abstracts and titles. A third, impartial reviewer will settle any disputes. Discussion: The evidence basis pertaining to this review will cohere to the thorough evaluation of NMD across contrasting patient demographics, functional outcomes, postoperative sequalae, comorbidity and mortality rates in modern-day neurosurgical practice. Systemic Review Registration: PROSPERO 2024 CRD42024610729. Future amendments to the protocol will be updated on the PROSPERO record.