Mental incapacity in patients undergoing neuro-oncologic treatment: a cross-sectional study.

Objective: To evaluate the prevalence of mental incapacity to make neuro-oncologic treatment decisions and to identify patients likely to experience difficulty with medical decision-making to enable a more rigorous and focused assessment.

Methods: The preoperative mental capacity to give valid consent to neurosurgery of 100 patients with radiologically suspected intracranial tumors was assessed. Mental capacity was formally assessed using the MacArthur Competence Assessment Tool for Treatment (MACCAT-T) conducted by a dual-qualified physician and lawyer. To assess the relationship between cognition and mental capacity, cognitive function was assessed after the MACCAT-T interview using the Addenbrooke's Cognitive Examination-revised (ACE-R). Decisions about capacity made by the assessor were compared with the informal assessment of capacity of the neurosurgical team.

Results: Of 100 patients, 25 were identified by the assessor as lacking the necessary mental capacity to give valid consent to neurosurgery. Mental incapacity was most common among patients with World Health Organization grade IV tumors (38%) and was more common in men than women (36% of men lacked capacity vs 14% of women). Patients lacking mental capacity were significantly more cognitively impaired than those with capacity (median [interquartile range (IQR)] total ACE-R of 44 [0, 65.5] for incapable patients compared with a median [IQR] total ACE-R score of 88 [82, 95] for patients with capacity). Of 25 patients found to lack capacity by the assessor, 13 (52%) were identified as lacking capacity by the neurosurgical team and were treated under the provisions of the Adults with Incapacity (Scotland) Act 2000. A score of <4/7 in the semantic verbal fluency subset of the ACE-R (naming up to 10 animals in 1 minute) was predictive of incapacity (96% sensitivity, 63% specificity).

Conclusions: Mental incapacity in patients with intracranial tumors is common and is underestimated by clinicians seeking consent for neuro-oncologic treatment. Cognitive impairment is associated with incapacity. We propose a simple, brief cognitive screening test to identify patients who warrant a more rigorous interrogation of their mental capacity as part of the process of seeking consent for neuro-oncologic treatment.