<p>Informed consent for elective neurosurgery presents unique challenges and perspectives pertaining to the ethics of neuroscience. Interprofessional presurgical assessments marshal the full complement of twenty-first century clinical neuroscientific technologies to provide patients and healthcare providers with copious and nuanced information about the risks and benefits of various medical and surgical treatment options. In contrast, the ethical analysis and scientific study of presurgical counselling and shared decision-making in elective neurosurgery is relatively under-developed. Here, we summarize the ethical context for epilepsy neurosurgery and spotlight a particular ethical conundrum in the practice of presurgical epilepsy assessment by considering the case of a patient recently seen at our epilepsy surgery center. This patient presented with frequent non-medical cannabis use which initially confounded the interpretation of their neuropsychological profile and thereby disqualified them from resective surgery. Through an iterative assessment-feedback-intervention process, the patient eliminated their use of non-medical cannabis. Subsequent neuropsychological reassessment revealed reduced psychological distress and improved quality of life and yielded an interpretable, favourable profile such that the patient and team then confidently proceeded with a successful right anterior-temporal lobectomy. The insights gleaned via serial assessment data from this single case underscore the importance of considering the confounding effects of non-medical cannabis use in presurgical assessment for epilepsy. Also highlighted are the broader threats to justice and autonomy – as well as the potential harms through action or inaction – when we fail to take appropriate account of sources of false-positive and false-negative inferential error in evaluating elective neurosurgery candidacy.</p>