This study describes a cohort of 23 patients undergoing stereotactic subcaudate tractotomy. Research Diagnostic Criteria indicated that 70% suffered major depressive disorder; the remainder mostly had a bipolar affective disorder. There were serial assessments pre-operatively and at 2 weeks and 6 months post-operatively using the Hamilton Rating Scale for depression, the Present State Examination (PSE), Newcastle Scale, the Beck Depression Inventory, and the Taylor Manifest Anxiety Scale. Neuropsychological assessment included tests thought to be sensitive to frontal lobe dysfunction, as well as tests of general intelligence, attention, memory, language and visuo-spatial function.

Post-operatively, depression rating scale scores decreased significantly but most patients continued to exhibit a number of PSE syndromes. Depression rating scale scores were correlated with 1 year global outcome: there was no significant correlation except for the 6 month assessment when lower Hamilton scores were found to be associated with better global outcome. Correlations between the neuropsychological tests and the Hamilton and Beck depression scales at 2 weeks post-operatively suggested that an improvement in psychiatric condition was associated with greater efficiency on some tests of attention and verbal recall, as well as faster performance on a sorting task. By contrast, the changes at 6 months suggested an association between improvement in psychiatric condition and less efficient performance on certain neuropsychological tests including verbal recognition memory, attention and two tests of frontal lobe dysfunction.