Statistical analysis
IBM SPSS (Statistical Package of Social Science) Version 25 was used to analyze the data. Categorical variables such as sex were expressed as numbers and percentages. Quantitative variables such as age, years of education, PALT, BVRT, P300 latency, and amplitude were expressed as the median and interquartile range (IQR). Chi-squared test was used for comparison between Nitroglycerine and Phentolamine groups in sex, whereas Mann-Whitney test was used for comparison between Nitroglycerine and Phentolamine groups in age, years of education, PALT, BVRT, P300 latency, and amplitude. Wilcoxon test was used to compare pre and post-operative PALT, BVRT, P300 latency, and amplitude in each of Nitroglycerine and Phentolamine groups. A mixed ANOVA test was used to compare pre and post-operative PALT, BVRT, P300 latency, and amplitude in Nitroglycerine versus Phentolamine groups. P-value ≤ 0.05 was considered statistically significant. All tests were two-tailed.