Prevalence and profile of cognitive impairment in adult glioma: a sensitivity analysis

Cognitive impairment has been reported in 27-83 % of adults with World Health Organization (WHO) grade I-III glioma. However, the few studies in this field used different methods for cognitive assessment. The objective of the present study was to establish the prevalence of cognitive impairment in patients with WHO grade I-III primary brain tumors and determine the effect sizes of a comprehensive battery of tests. This study used a comprehensive neuropsychological battery to examine 27 patients. To control for false positives, prevalence was estimated from the overall neuropsychological score. Size effects were determined using Cohen's d. Cognitive impairment was observed in 51.9 % (95 % CI 33-70.7 %) of the patients; the impairment affected action speed (38.5 %), cognitive (33 %) and behavioral (21.7 %) executive functions, oral expression (29.6 %), episodic memory (29.6 %) and visuoconstructive abilities (19.2 %). The largest effect sizes (d ≥ 1.645) were observed for the Digit Symbol Substitution test, global hypoactivity, free recall, Stroop time, the Boston Naming test (BNT), the Trail Making test B (TMTB), verbal fluency and the Rey-Osterrieth Complex Figure Test. Four of these scores (global hypoactivity, the Digit Symbol Substitution test, the TMTB perseveration, and the BNT) were combined to make a shortened battery (AUC 0.872; 95 % CI 0.795-0.949). The overall neuropsychological score was the sole factor associated with the functional outcome. Our results suggest that about half of survivors with a grade I-III primary brain tumor suffer from cognitive impairment. Tests with a large effect size should be included in future large-scale studies.