Long-term evaluation of cognition after glioma surgery in eloquent areas

Preservation of cognition is an important outcome measure in eloquent area glioma surgery. Glioma patients may have pre-operative deficits in one or more cognitive domains which could deteriorate post-operatively. It is assumed that these impairments recover within 3 months; some studies however, still detected cognitive decline. Longer follow-up is necessary to elucidate the conclusive effects of surgery. 45 patients with gliomas (low- and high-grade, but without contrast enhancement at diagnosis) in eloquent areas were assessed pre-operatively, 3 months and 1 year post-operatively with a neuropsychological test-protocol. Patients' performance was compared to normal population and between test-moments. Univariate analyses were performed between cognitive change and tumor-characteristics (localization, grade, volume, extent of resection [EOR]) and treatment-related factors (radio-/chemotherapy). Pre- and post-operatively, impairments were found in all cognitive domains; language, memory, attention and executive functions (p < 0.05). Post-operatively, permanent improvement was observed on a memory test (verbal recall: t = -1.931, p = 0.034), whereas deterioration was found on a language test (category fluency: t = 2.517, p = 0.030). Between 3 months and 1 year, patients improved on 2 language tests (naming: t = -2.781, p = 0.026 and letter fluency: t = -1.975, p = 0.047). There was no influence of tumor- or treatment-related factors on cognitive change. The findings underline the importance of cognitive testing at longer term post-operatively, as cognitive recovery took longer than 3 months, especially within the language domain. However, this longitudinal follow-up study showed that glioma surgery is possible without major long-term damage of cognitive functions. Tumor characteristics and EOR are no additional risk factors for cognitive outcome.