Intracranial tumors often impair cerebral autoregulation, especially in the regions adjacent to the tumors. This impairment can affect the brain’s ability to regulate blood flow in response to increased metabolic demand or stimuli, a capacity known as cerebrovascular reserve. Previous studies have shown that this reserve is often compromised in patients with supratentorial tumors. While some research has explored the immediate effects of tumor decompression on cerebrovascular reserve, there is limited data on long-term outcomes and the potential link between impaired reserve and postoperative neurological deficits. This study investigates the relationship between preoperative cerebrovascular reserve and postoperative neurological deficits in patients undergoing elective supratentorial brain tumor surgeries. The study hypothesizes that patients with impaired preoperative cerebrovascular reserve are more likely to develop new or worsening postoperative neurological deficits. The aim is to assess preoperative cerebrovascular reserve and correlate it with the incidence of postoperative neurological deficits. Additionally, the study will examine the relationship between preoperative autonomic dysfunction and postoperative outcomes, as well as changes in cerebrovascular reserve three months after surgery. This prospective observational study will be conducted at the National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, involving adult patients aged 50 to 80 years undergoing elective supratentorial tumor surgeries. The cerebrovascular reserve will be assessed by calculating the Breath Holding Index (BHI) using Transcranial Doppler (TCD). Autonomic function will be assessed from measuring the patient’s heart rate variability in the pre-operative period. The results from this study will provide valuable insights into the impact of impaired cerebrovascular reserve on postoperative neurological outcomes and the potential role of autonomic dysfunction in these patients.