Flash stimulation evoked potentials in diagnosis of chronic glaucoma

Preterm infants with isolated cerebellar hemorrhage show bilateral cortical alterations at term equivalent age

The cerebellum is connected to numerous regions of the contralateral side of the cerebrum. Motor and cognitive deficits following neonatal cerebellar hemorrhages (CbH) in extremely preterm neonates may be related to remote cortical alterations, following disrupted cerebello-cerebral connectivity as was previously shown within six CbH infants. In this retrospective case series study, we used MRI and advanced surface-based analyses to reconstruct gray matter (GM) changes in cortical thickness and cortical surface area in extremely preterm neonates (median age = 26; range: 24.9-26.7 gestational weeks) with large isolated unilateral CbH (N = 5 patients). Each CbH infant was matched with their own preterm infant cohort (range: 20-36 infants) based on sex and gestational age at birth. On a macro level, our data revealed that the contralateral cerebral hemisphere of CbH neonates did not show less cortical thickness or cortical surface area than their ipsilateral cerebral hemisphere at term. None of the cases differed from their matched cohort groups in average cortical thickness or average cortical surface area in the ipsilateral or contralateral cerebral hemisphere. On a micro (i.e. vertex) level, we established high variability in significant local cortical GM alteration patterns across case-cohort groups, in which the cases showed thicker or bigger volume in some regions, among which the caudal middle frontal gyrus, insula and parahippocampal gyrus, and thinner or less volume in other regions, among which the cuneus, precuneus and supratentorial gyrus. This study highlights that cerebellar injury during postnatal stages may have  widespread bilateral influence on the early maturation of cerebral cortical regions, which implicate complex cerebello-cerebral interactions to be present at term birth.

Gut microbiome and brain functional connectivity in infants-a preliminary study focusing on the amygdala

Recently, there has been a surge of interest in the possibility that microbial communities inhabiting the human gut could affect cognitive development and increase risk for mental illness via the "microbiome-gut-brain axis." Infancy likely represents a critical period for the establishment of these relationships, as it is the most dynamic stage of postnatal brain development and a key period in the maturation of the microbiome. Indeed, recent reports indicate that characteristics of the infant gut microbiome are associated with both temperament and cognitive performance. The neural circuits underlying these relationships have not yet been delineated. To address this gap, resting-state fMRI scans were acquired from 39 1-year-old human infants who had provided fecal samples for identification and relative quantification of bacterial taxa. Measures of alpha diversity were generated and tested for associations with measures of functional connectivity. Primary analyses focused on the amygdala as manipulation of the gut microbiota in animal models alters the structure and neurochemistry of this brain region. Secondary analyses explored functional connectivity of nine canonical resting-state functional networks. Alpha diversity was significantly associated with functional connectivity between the amygdala and thalamus and between the anterior cingulate cortex and anterior insula. These regions play an important role in processing/responding to threat. Alpha diversity was also associated with functional connectivity between the supplementary motor area (SMA, representing the sensorimotor network) and the inferior parietal lobule (IPL). Importantly, SMA-IPL connectivity also related to cognitive outcomes at 2 years of age, suggesting a potential pathway linking gut microbiome diversity and cognitive outcomes during infancy. These results provide exciting new insights into the gut-brain axis during early human development and should stimulate further studies into whether microbiome-associated changes in brain circuitry influence later risk for psychopathology.

The flash stimulated VEP in the diagnosis of glaucoma

The Visual Evoked Potential using pattern stimulation has been used in recent years as an attempt to make an early diagnosis of glaucoma. However because of the macular dominance of responses obtained by this method, only diseases involving the papillomacular bundle reveal abnormality; such conditions do not occur in glaucoma. In this study we report the use of the early component (P1) of the flash stimulated visual evoked potential in the diagnosis of primary open angle glaucoma. It appears to provide an objective, accurate and repeatable screening technique. The size of P1 correlates well with the size of optic disc cupping, and field loss. The relationships between systemic vascular disease, P1 reductions, and glaucoma, lend support to the ischaemic origins of the disease.

The correlation of visual evoked potentials (VEP) and visual field indices (Octopus G1) in glaucoma and ocular hypertension

Flash evoked responses and the visual field indices (VFI) of the Octopus G1 program were recorded from 42 eyes of 21 patients, aged 23-76 years (mean 51 years); 29 eyes had open-angle glaucoma (OAG) and 10 ocular hypertension (OH). Three eyes were normal. The early component of the VEP called P 120 had lower amplitude in glaucomatous eyes compared with normal or hypertensive eyes. Mean sensitivity (MS), mean defect (MD), and short time fluctuation (SF), indicative of diffuse non-specific nerve fiber los, correlated significantly (P less than 0.05). Reliability factor (RF), which is indicative of psychodynamic factors, also correlated significantly (P less than 0.05) in eyes with OAG.

Electrophysiological testing of eyes with opaque media

Electrodiagnostic tests as applied to the eye are now widely used in the investigation of patients with inherited retinal degenerations but their value in patients with opaque media is perhaps less well recognised. The choice of stimulus is all important and a flash VEP and flash ERG probably provide the best combination of tests at present. A comparison with the fellow eye, if it is normal, greatly improves the value of the result. A pitfall of this type of test is its failure to detect amblyopia and a carefully recorded history is important in helping to interpret the traces.