Low-grade glioma (LGG) patients may suffer from mild aphasia that cannot be detected with standard tests. The Diagnostic Instrument for Mild Aphasia (DIMA) is the first standardized test battery to assess mild language disorders. We investigate pre- and postoperative language abilities of LGG and high-grade glioma (HGG) patients with the DIMA.

The DIMA consists of phonology (word, compound, non-word, sentence repetition), semantics (odd-picture-out), and syntax (sentence completion) subtests. The Boston Naming Test, Verbal Fluency, and Token Test were also administered. Patients were assessed before awake surgery (T1, N=98), three-months (T2, N=69), and one-year (T3, N=30) postoperatively. DIMA performance was compared to healthy controls (N=214). Group differences were statistically examined.

DIMA: At T1, patients deviated on sentence repetition and completion. HGG patients performed worse than LGG on word, non-word, and sentence repetition. At T2, compound repetition and odd-picture-out also became impaired with a decline on all repetition tasks. At T3, sentence completion remained impaired with a deterioration compared to T1. Standard tests: At T1, patients deviated on BNT and Verbal Fluency. HGG patients performed worse on BNT and TT. Patients with left-hemispheric tumors performed worse on BNT and Letter Fluency. At T2, TT also became impaired and patients declined on Verbal Fluency. At T3, only BNT and Category Fluency were impaired, with no significant postoperative declines.

The DIMA is the first test battery to detect peri-operative impairments in glioma patients at different linguistic levels. It appeared more sensitive to detect surgical effects than standard tests: all phonological DIMA subtests captured short-term decline and sentence completion detected long-term decline. Hemispheric tumor localization only affected standard test performance, tumor grade impacted performance on DIMA repetition, BNT and TT.