BACKGROUND: Neurologic events have been reported in patients with coronavirus disease 2019 . However, a modelbased evaluation of the spatial distribution of these events is lacking. PURPOSE: Our aim was to quantitatively evaluate whether a network diffusion model can explain the spread of small neurologic events.
Background Neuropathology caused by the coronavirus disease 2019 (COVID-19) has been reported across several studies. The characterisation of the spatial distribution of these pathology remains critical to assess long and short-term neurological sequelae of COVID-19. To this end, Mathematical models can be used to characterise the location and aetiologies underlying COVID-19-related neuropathology. Method We performed a systematic review of the literature to quantify the locations of small neurological events identified with magnetic resonance imaging (MRI) among COVID-19 patients. Neurological events were localised into the Desikan-Killiany grey and white matter atlases. A mathematical network diffusion model was then used to test whether the spatial distribution of neurological events could be explained via a linear spread through the structural connectome of the brain. Findings We identified 35 articles consisting of 123 patients that assessed the spatial distribution of small neurological events among COVID-19 patients. Of these, 91 patients had grey matter changes, 95 patients had white matter changes and 72 patients had confirmed cerebral microbleeds. White matter events were observed within 14 of 42 white matter bundles from the IIT atlas. The highest proportions (26%) of events were observed within the bilateral corticospinal tracts. The splenium and middle of the corpus callosum were affected in 14% and 9% of the cases respectively. Grey matter events were spatially distributed in the 41 brain regions within the Desikan-Killiany atlas. The highest proportions (~10%) of the events were observed in areas including the bilateral superior temporal, precentral, and lateral occipital cortices. Sub-cortical events were most frequently identified in the Pallidum. The application of a mathematical network diffusion model suggested that the spatial pattern of the small neurological events in COVID-19 can be modelled with a linear diffusion of spread from epicentres in the bilateral cerebellum and basal ganglia (Pearsons r=0.41, p<0.001, corrected). Interpretation To our knowledge, this is the first study to systematically characterise the spatial distribution of small neurological events in COVID-19 patients and test whether the spatial distribution of these events can be explained by a linear diffusion spread model. The location of neurological events is consistent with commonly identified neurological symptoms including alterations in conscious state among COVID-19 patients that require brain imaging. Given the prevalence and severity of these manifestations, clinicians should carefully monitor neurological symptoms within COVID-19 patients and their potential long-term sequelae.
Individuals with temporal lobe epilepsy (TLE) often have an impairment of conversational language manifesting as verbosity and attributable to disruption of cognitive-linguistic networks. The micro- and macrolinguistic underpinnings of this disturbance, and the role of epilepsy and cognitive variables, are yet to be explored. We examined the elicited language output of 16 individuals with TLE and 14 healthy controls under separate monologic discourse tasks: a structured and constrained context, elicited by description of the Cookie Theft picture, and an unstructured, unconstrained context, elicited by description of a Typical Day. We hypothesised that language output in the unstructured context would be characterised by verbosity to a greater extent than language elicited in a structured context. Following transcription and coding, detailed multi-level discourse analysis suggested that a constrained context gives rise to microlinguistic disturbances in individuals with TLE, reducing fluency, with more pauses and fillers. Under an unconstrained context, as anticipated, classical aspects of verbosity emerge in those with TLE, manifesting as longer speaking time, a longer duration of pauses, and a higher proportion of repetitive or redundant statements. Macrolinguistic elements such as coherence and informativeness are widely impacted, particularly disturbing language formulation. Correlations suggest that microlinguistic disturbances are closely linked with the immediate impact of seizures on cognitive-linguistic function, while macrolinguistic disturbances are more broadly impacted by disorder severity and word retrieval deficits. These findings suggest that different psycholinguistic impairments emerge as a function of differing linguistic challenges imposed by constrained and unconstrained conversational contexts. We conclude that these patterns reflect a dynamic linguistic system taking shape under specific contextual conditions.
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