In neuromyelitis optica spectrum disorders (NMOSD), cognitive impairment (CI) is nowadays considered as a unique relapse-unrelated manifestation of the disease. As a proof-of-concept, anti-aquaporin4 (AQP4)-IgG seems to inhibit neuronal plasticity and long-term potentiation. Structural and functional MRI (fMRI) studies have disclosed an association with damage of the precuneus (PCUN) and cognitive impairment (CI) in several neurological conditions.
To explore the role of dynamic functional connectivity (dFC) of the PCUN at resting state (RS) to explain cognitive alterations in NMOSD patients.
3.0 T RS fMRI were acquired from 27 AQP4-positive NMOSD patients and 30 age- and sex-matched healthy controls (HC). Patients underwent an extensive neuropsychological evaluation including the assessment of global and domain-specific cognitive impairment index (CII) and Beck Depression Inventory II (BDI-II) scores. DFC of the left (L) and right (R) PCUN was assessed by means of sliding-window seed-voxel correlation analysis. Standard deviation of dFC across windows was used as a measure of dynamicity (the higher the better). Age- and sex-adjusted between-group dFC comparisons and correlations with cognitive scores were assessed using SPM12 and full-factorial models. A p value <0.001 was considered statistically significant.
Compared to HC, NMOSD patients had reduced L-PCUN dFC with caudate nucleus, rectus, olfactory bulb and occipital inferior gyrus and increased dFC between the L-PCUN and the middle temporal gyrus and between the R-PCUN the middle occipital gyrus. Global CII positively correlated with higher L-intra-PCUN dFC, as well as with higher dFC between the L-PCUN and the middle temporal and middle frontal gyrus and between the R-PCUN and the middle cingulate gyrus. Impairment of information processing speed (IPS, 59.2%) and depression (63.0%) were the most common cognitive alterations. The IPS index positively correlated with a higher L-intra-PCUN-dFC, and a higher dFC between the R-PCUN and the middle cingulate gyrus. The BDI-II score positively correlated with a higher dFC between the R-PCUN and the middle frontal gyrus.
The assessment of PCUN dFC supports the role of PCUN in NMOSD cognitive dysfunction. We observed a protective effect of higher dynamic connections with limbic regions for cognitive performance, while those with the frontal lobe were detrimental for depressive symptoms.