Posterior cortical atrophy - a prototypical case of dementia beginning with visual symptoms: case report / Atrofia cortical posterior - um caso prototípico de demência iniciando com sintomas visuais: relato de caso

Dementia presenting with prominent higher order visual symptoms may be observed in a range of neurodegenerative conditions and is often challenging to diagnose. We describe a case of progressive dementia presenting with prominent visual cortical symptoms. A 55-year-old, right-handed, woman with early onset of visual impairment not associated with anterior visual pathology, presenting with dyslexia, visual agnosia, Balint's syndrome, and spatial disorientation. Ophthalmologists should consider this condition especially in presenile patients with slowly progressive higher-order visual symptoms. Although described in association with different conditions, it may also occur in Alzheimer disease.

As demências que se apresentam predominantemente com sintomas visuais associativos podem ser observadas em diferentes condições neurodegenerativas, sendo seu diagnóstico muitas vezes desafiador. Descrevemos um caso com demência progressiva que se apresentam com sintomas visuais proeminentes. Mulher de 55 anos, destra, com início precoce de déficits visuais não associados a patologia visual anterior, apresentando dislexia, agnosia visual, síndrome de Balint e desorientação espacial. Os oftalmologistas devem ter em mente essa condição especialmente em pacientes pré-senis com queixas visuais complexas e lentamente progressivas. Apesar de descritas em diferentes condições, pode ocorrer na doença de Alzheimer.

The modified 2VO ischemia protocol causes cognitive impairment similar to that induced by the standard method, but with a better survival rate

Permanent bilateral occlusion of the common carotid arteries (2VO) in the rat has been established as a valid experimental model to investigate the effects of chronic cerebral hypoperfusion on cognitive function and neurodegenerative processes. Our aim was to compare the cognitive and morphological outcomes following the standard 2VO procedure, in which there is concomitant artery ligation, with those of a modified protocol, with a 1-week interval between artery occlusions to avoid an abrupt reduction of cerebral blood flow, as assessed by animal performance in the water maze and damage extension to the hippocampus and striatum. Male Wistar rats (N = 47) aged 3 months were subjected to chronic hypoperfusion by permanent bilateral ligation of the common carotid arteries using either the standard or the modified protocol, with the right carotid being the first to be occluded. Three months after the surgical procedure, rat performance in the water maze was assessed to investigate long-term effects on spatial learning and memory and their brains were processed in order to estimate hippocampal volume and striatal area. Both groups of hypoperfused rats showed deficits in reference (F(8,172) = 7.0951, P < 0.00001) and working spatial memory [2nd (F(2,44) = 7.6884, P < 0.001), 3rd (F(2,44) = 21.481, P < 0.00001) and 4th trials (F(2,44) = 28.620, P < 0.0001)]; however, no evidence of tissue atrophy was found in the brain structures studied. Despite similar behavioral and morphological outcomes, the rats submitted to the modified protocol showed a significant increase in survival rate, during the 3 months of the experiment (P < 0.02).

Densidad neuronal en la corteza visual primaria (área 17), en ratas sometidas a estrés crónico / Density in primary visual cortex (17 visual area) from rats subjected to chronic stress

El estrés puede ser definido como una amenaza a la integridad psicológica o fisiológica de un individuo. Por otro lado, se ha verificado que el estrés tiene efecto sobre la morfología y función de diversas estructuras del Sistema Nervioso Central, relacionadas con el aprendizaje, memoria y respuestas emocionales, tales como el hipocampo, amígdala y corteza prefrontal. Es por lo anterior, que el objetivo del presente trabajo fue realizar un estudio de la anatomía de la corteza visual primaria (área 17), en ratas machos (n=9), de la cepa Sprague-Dawley, de 3 meses de edad (250-350g.), sometidas a estrés crónico por inmovilización. Es así como se observó que el grupo estrés (n=3) presentó una menor densidad neuronal que el grupo control (n=3) y una significativa menor densidad neuronal (p<0,05) que el grupo post estrés (n=3) el cual presentó la más alta densidad neuronal observada. Estableciendo una relación inversa entre densidad neuronal y tamaño de los somas neuronales y sus respectivas conexiones y ramificaciones dendríticas. Lo anterior podría tener incidencia en el procesamiento de la información visual.

Stress can be understood as a threat to psychological or physiological integrity of the individual. Stress has previously shown to alter morphology and function of diverse structures of the Central Nervous System related to learning, memory and emotional response, such as hippocampus, amygdala and prefrontal cortex. In the current work we assessed the effect of chronic stress for immobilization on structure of primary visual cortex (area 17) in male adult Sprague-Dawley rats (n=9), of 3 months of age (250-350g.). Stressed rats (n=3) tended to show lower neuronal densities than control rats (n=3) and were significantly lower (p<0.05) than recovered post-stress rats (n=3), which showed the highest neuronal densities observed. Since an inverse correlation between neuronal density and size of neuronal bodies and their respective dendrite branches, these changes might impact processing of visual information.

Cortical blindness: an unusual sequela of snake bite.

Several ophthalmic effects may follow snake bite; this report describes an instance of cortical blindness that resulted from snake bite.

Methylmercury intoxication and histochemical demonstration of NADPH-diaphorase activity in the striate cortex of adult cats

The effects of methylmercury (MeHg) on histochemical demonstration of the NADPH-diaphorase (NADPH-d) activity in the striate cortex were studied in 4 adult cats. Two animals were used as control. The contaminated animals received 50 ml milk containing 0.42 µg MeHg and 100 g fish containing 0.03 µg MeHg daily for 2 months. The level of MeHg in area 17 of intoxicated animals was 3.2 µg/g wet weight brain tissue. Two cats were perfused 24 h after the last dose (group 1) and the other animals were perfused 6 months later (group 2). After microtomy, sections were processed for NADPHd histochemistry procedures using the malic enzyme method. Dendritic branch counts were performed from camera lucida drawings for control and intoxicated animals (N = 80). Average, standard deviation and Student t-test were calculated for each data group. The concentrations of mercury (Hg) in milk, fish and brain tissue were measured by acid digestion of samples, followed by reduction of total Hg in the digested sample to metallic Hg using stannous chloride followed by atomic fluorescence analysis. Only group 2 revealed a reduction of the neuropil enzyme activity and morphometric analysis showed a reduction in dendritic field area and in the number of distal dendrite branches of the NADPHd neurons in the white matter (P<0.05). These results suggest that NADPHd neurons in the white matter are more vulnerable to the long-term effects of MeHg than NADPHd neurons in the gray matter.

Localization of NADPH diaphorase activity in the human visual cortex

The present report describes the activity of NADPH-diaphorase (NADPHd) in area 17 of autopsied normal human visual cortex. Four human brains from autopsy tissue (4-8 h postmortem) were fixed by immersion in 4 per cent paraformaldehyde in 0.1 M sodium phosphate buffer, pH 7.2-7.4, or in 10 per cent formalin for 24 h. NADPHd histochemistry was done using the malic enzyme indirect method. The neurpile pattern of enzyme activity presented a clear six layer appearance. Cell morphology and the laminar distribution of 73 NADPHd-positive neurons are descrived. All neurons found in area 17 of human cortex were sparsely spiny or smooth cells, located in all cortical layers exept layer 4c. Quantitative analysis of the branching pattern of the dendritic tree was carried out. A symmetrical pattern was observed with no particular dendritic bias except for a few white matter and layer 1 cells. Larger dendritic fields were found in white matter cells when compared to the other corical layers. Comparison of cell densities for gray and white matters showed that 85 per cent of the NADPHd-positive neurons were located in the white matter. NADPH was colocalized with nitric oxide synthase which produces nitric oxide, a short-life neuromediator implicated in synaptic plasticity, neuroprotection, and neurotoxicity. thus, the spatial distribution of the NADPHd cells is important for posterior functional studies of the neuromediators in the brain