Event-related potentials and deep grey matter atrophy in multiple sclerosis: Exploring the possible associations with cognition

BACKGROUND

Event-related potentials (ERPs) have been proposed as a neurophysiological biomarker to capture cognitive dysfunction in multiple sclerosis (MS). Few studies have evaluated the relationships between ERPs and brain atrophy as known marker of structural brain damage related to cognitive impairment (CI).

OBJECTIVES

To explore the relationships of brain atrophy, including of the cortex and deep grey matter, with ERP abnormalities and cognitive function, as defined using the Brief Repeatable Battery of Neuropsychological Tests (BRBN).

RESULTS

Seventy-eight patients with relapsing-remitting MS were enroled, of which 38 (48.7%) had CI. Independent t-test comparisons of the ERP parameters found a significant difference in P300 wave latency, with a latency of 343.7 ± 32.6 ms in the CI group vs. 320.3 ± 16.5 ms in the cognitively preserved (CP) group (p = 0.001). Significant differences in the MRI measurements, including the cortex (p = 0.02) and deep grey matter structures [thalamus (p = 0.001), amygdala (p = 0.030), and nucleus accumbens (p = 0.004)) were observed, with lower measurements in the CI group. Regression models were also performed to explore the impact of brain volumes on ERP parameters. This showed a relationship between P300 latency and the lower amygdala (p = 0.02) and hippocampus (p = 0.03) volumes, while the amplitude of the P300 was significantly associated with a lower cortex volume (p = 0.01).

CONCLUSION

Cortex volume emerged as the most significant predictor of the P300 amplitude. The amygdala and hippocampal volumes were found to influence P300 latency, highlighting the role of deep grey matter atrophy in ERPs for the first time. The combination of structural MRI and neurophysiological techniques, sensitive to diverse aspects of MS pathology, could improve the understanding of CI in MS and its neurodegenerative and inflammatory substrate.

Bipolar disorders and deep grey matter in multiple sclerosis: A preliminary quantitative MRI study

BACKGROUND

Bipolar disorder (BD) is frequently observed in patients affected by multiple sclerosis (MS), presenting a lifetime estimate of around 8%. However, uncertainty exists on the brain damage associated with this psychiatric comorbidity. This study aimed to investigate the effect of brain atrophy, particularly that of the subcortical grey matter (scGM) structures that notoriously regulate the affective functioning, on the co-occurrence of BD in patients with MS.

METHODS

A group of patients with MS affected by BD and a control group of patients with MS without any mood/psychiatric disorder, as defined using standardised diagnostic tools (Advanced Neuropsychiatric Tools and Assessment Schedule), were recruited. The patients underwent brain MRI, and the volumes of the whole brain (WB), white matter (WM), and grey matter (GM) were estimated using SIENAX. Thus, the scGM volumes of the putamen, caudate, thalamus, hippocampus, amygdala, nucleus accumbens, and pallidus were estimated using the FIRST tool.

RESULTS

The sample included 61 patients with MS, amongst whom 15 (24.6%) had BD. No differences in the WB, WM, and cortical GM volumes were observed between the patients with MS with and without BD. Conversely, the multiple regression analysis revealed a significant association of BD with lower volumes of the putamen (p = 0.032), nucleus accumbens (p = 0.029), and pallidus (p = 0.061; with a trend towards significance), independently from the demographic and MS clinical features.

CONCLUSIONS

Our preliminary results indicated that the nucleus accumbens and putamen are smaller in MS patients with BD. Further investigations in larger cohorts of MS patients with affective disorders are necessary to confirm these data and understand the structural brain damage underlying this psychiatric comorbidity.

The impact of deep grey matter volume on cognition in multiple sclerosis

BACKGROUND

Cognitive dysfunctions are very frequent in people living with multiple sclerosis (MS). Several studies have previously indicated grey matter (GM) atrophy as useful predictor of patients' cognitive impairment. However, considerable uncertainty exists about the possible impact of deep grey matter volumes on cognition. This study aimed to evaluate the relationship of the subcortical (sc) GM volumes with the presence and severity of global and selective cognitive impairment in MS.

METHODS

A group of MS patients with relapsing remitting course were enrolled. Patients underwent a neuropsychological evaluation by using the Brief Repeatable Battery of Neuropsychological Tests (BRBN) and the Delis-Kaplan Executive Function System Sorting Test (D-KEFST); z scores were estimated and items with z score below 2 standard deviation were considered failed. Thus, brain MRIs images were acquired and measurements of whole brain (WB), white matter (WM), and cortical grey matter (GM) were obtained by SIENAX. After FIRST tool segmentation, volumes of subcortical GM structures were also estimated.

RESULTS

The sample included 50 MS patients, of which 16/50 (32%) subjects were cognitively impaired. Multiple regression analyses found a significant association of severity of cognitive impairment, defined as number of failed neuropsychological tests, with lower volumes of cortex (p=0.003), thalamus (p=0.009), caudate (p=0.011), putamen (p=0.020), pallidus (p=0.012) and hippocampus (p=0.045), independently from other MS features. In addition, an association between accumbens volume and D-KEFS ST FSC and D-KEFS ST FSD z scores was observed (p<0.03).

CONCLUSIONS

Our results indicated that volumes of several scGM structures, and in particular of thalamus, contribute to determine cognitive dysfunctions in MS, mainly influencing the executive functioning. Further investigations in larger MS cohorts with cognitive impairment are necessary to better understand the structural brain damage underlying this "invisible disability".

Cognition in multiple sclerosis: Between cognitive reserve and brain volume

BACKGROUND

Several correlations between cognitive impairment (CI), radiologic markers and cognitive reserve (CR) have been documented in MS.

OBIECTIVE

To evaluate correlation between CI and brain volume (BV) considering CR as possibile mitigating factor.

METHODS

195 relapsing MS patients underwent a neuropsychological assessment using BICAMS. BV was estimated using SIENAX to obtain normalized volume of brain (NBV), white matter (NWV), gray matter (NGV) and cortical gray matter (CGV). CR was estimated using a previously validated tool.

RESULTS

Pearson test showed a correlation between the symbol digit modality test (SDMT) score and NBV (r=0.38; p<0.000) NGV(r=0.31; p<0.000), CGV (r=0.35; p<0.000) and CRI score(r=0.42; p<0.000). Linear regression (dependent variable:SDMT) showed a relationship with CR scores (p=0.000) and NGV(p<0.000). A difference was detected between cognitive impaired and preserved patients regarding mean of NBV(p=0.002), NGV(p=0.007), CGV(p=0.002) and CR Scores (p=0.007). Anova showed a association between the presence of CI (dependent variable) and the interaction term CRIQ × CGV (p=0.004) whit adjustment for age and disability evaluated by EDSS.

CONCLUSIONS

Our study shows a correlation between cognition and BV, in particular gray matter volume. Cognitive reserve is also confirmed as an important element playing a role in the complex interaction to determine the cognitive functions in MS.

'Timed up and go' and brain atrophy: a preliminary MRI study to assess functional mobility performance in multiple sclerosis

Motor and cognitive disabilities are related to brain atrophy in multiple sclerosis (MS). 'Timed up and go' (TUG) has been recently tested in MS as functional mobility test, as it is able to evaluate ambulation/coordination-related tasks, as well as cognitive function related to mobility. The objective of this study is to evaluate the relationship between brain volumes and TUG performances. Inclusion criteria were a diagnosis of MS and the ability to walk at least 20 m. TUG was performed using a wearable inertial sensor. Times and velocities of TUG sub-phases were calculated by processing trunk acceleration data. Patients underwent to a brain MRI, and volumes of whole brain, white matter (WM), grey matter (GM), and cortical GM (C) were estimated with SIENAX. Sixty patients were enrolled. Mean age was 41.5 ± 11.6 years and mean EDSS 2.3 ± 1.2. Total TUG duration was correlated to lower WM (ρ = 0.358, p = 0.005) and GM (ρ = 0.309, p = 0.017) volumes. A stronger association with lower GM volume was observed for intermediate (ρ = 0.427, p = 0.001) and final turning (ρ = 0.390, p = 0.002). TUG is a useful tool in a clinical setting as it can not only evaluate patients' disability in terms of impaired functional mobility, but also estimate pathological features, such as grey atrophy.