ID #640 Utilizing resting state EEG to differentially diagnose cerebellar mutism syndrome: the potential of the delta alpha ratio.

Differential diagnosis of cerebellar mutism syndrome (CMS) following posterior fossa tumor surgery is challenging. While scoring scales are available, diagnosis is based on perceptual assessment. Accurate diagnosis is essential to ensure the individual has access to intensive rehabilitation services but also, to aid in elucidating the neural underpinnings of CMS to minimize the occurrence. Increased Delta Alpha Ratio (DAR) collected through resting state EEG, has been associated with reduced cortical arousal [1] and slowed information processing [2]in stroke and brain injury populations.

Purpose

To determine if increased DAR is present in CMS and therefore, could serve as a neurophysiologic marker for differential diagnosis.

Methods

Resting state electroencephalography (EEG) was used to collect spectral power values from the left frontal and right frontal cortical regions across three groups: individuals who had posterior fossa tumor resection and 1) acquired CMS, 2) did not acquire CMS and 3) healthy, age-matched peers. Data from behavioral assessments of ataxia including the SARA and a perceptual speech assessment were also collected.

Results

Data from 11 participants was analyzed; CMS (n = 4, mean age 16.71±5.94 years), Non-CMS (n = 3, mean age 14.30 ± 4.16 years) and Control (n = 4, mean age 17.7 ±6.31 years). Delta alpha ratio (DAR) was calculated for each of the targeted electrodes (Fp1, Fp2, F3, F4, F7 and F8) across groups. Statistically significantly higher DAR values were found in the CMS group at F3 (p < 0.001), F7 (p = 0.009), Fp2 (p < 0.001), F4(p < 0.001) and F8(p < 0.001) and no significant differences between the non-CMS and control groups. While moderate positive correlations were found between DAR and ataxia severity, none reached statistical significance.

Conclusion

The utility of the DAR measure may hold potential for serving as a neurophysiologic marker for the differential diagnosis of CMS by indirectly measuring the integrity of the cerebello-thalamo-cortical pathway and/or reflecting cross-cortical diaschisis.

1. Fanciullacci C, Bertolucci F, Lamola G, Panarese A, Artoni F, Micera S, et al. Delta Power Is Higher and More Symmetrical in Ischemic Stroke Patients with Cortical Involvement. Front Hum Neurosci. 2017 Jul 28;11:385. https://doi.org/10.3389/fnhum.2017.00385

2. Harmony T. The functional significance of delta oscillations in cognitive processing. Front Integr Neurosci. 2013;7. http://journal.frontiersin.org/article/10.3389/fnint.2013.00083/abstract