Brainstem auditory and visual evoked potentials in children with protein-energy malnutrition

Influence of malnutrition on the development of the central nervous system of malnourished children

Introduction: Protein-caloric malnutrition is a public health concern in certain areas of the Brazil. It can affect growth, the auditory nervous system development and, consequently, the cognition. This study compared the Brainstem Auditory Evoked Potential (BAEP) between malnourished and eutrophic children.Methods: A total of 111 children, aged 0-60 months, were examined: 57 were malnourished, according to the World Health Organization criteria, and 54 were normo-nourished. All the subjects underwent otorhinolaryngological evaluations and had acoustic immittance and transient evoked otoacoustic emissions within the normal range. The BAEP responses to click and tone burst stimuli were recorded at intensities of 80, 60, 40, and 30 dBNA.Results: We observed that latencies of I, III, and V waves and interpeaks III-V at 80 dBNA with click stimuli were significantly higher in all malnourished children when compared to those in the eutrophic children, as was the I-V interval in the 0- to 24-month group. The V-wave latencies at those intensities were also significantly higher in malnourished children.Conclusions: Malnourished children presented changes in BAEP characterized by delayed wave latency and interpeak intervals when compared to eutrophic children, suggesting alterations in both peripheral and central auditory pathways development and maturation.

Assessment of neurodisability and malnutrition in children in Africa

Neurodevelopmental delay, neurodisability, and malnutrition interact to contribute a significant burden of disease in global settings. Assessments which are well integrated with plans of management or advice are most likely to improve outcomes. Assessment tools used in clinical research and programming to evaluate outcomes include developmental and cognitive tools that vary in complexity, sensitivity, and validity as well as the target age of assessment. Few tools have been used to measure socioemotional outcomes and fewer to assess the disabled child with malnutrition. There is a paucity of tools used clinically which actually provide families and professionals with advice to improve outcomes. Brain imaging, electroencephalography, audiology, and visual assessment can also be used to assess the effect of malnutrition on brain structure and function. The interaction of neurodisability and malnutrition is powerful, and both need to be considered when assessing children. Without an integrated approach to assessment and management, we will not support children and families to reach their best potential outcomes.

Physiological slowing and upregulation of inhibition in cortex are correlated with behavioral deficits in protein malnourished rats

Protein malnutrition during early development has been correlated with cognitive and learning disabilities in children, but the neuronal deficits caused by long-term protein deficiency are not well understood. We exposed rats from gestation up to adulthood to a protein-deficient (PD) diet, to emulate chronic protein malnutrition in humans. The offspring exhibited significantly impaired performance on the 'Gap-crossing' (GC) task after reaching maturity, a behavior that has been shown to depend on normal functioning of the somatosensory cortex. The physiological state of the somatosensory cortex was examined to determine neuronal correlates of the deficits in behavior. Extracellular multi-unit recording from layer 4 (L4) neurons that receive direct thalamocortical inputs and layers 2/3 (L2/3) neurons that are dominated by intracortical connections in the whisker-barrel cortex of PD rats exhibited significantly low spontaneous activity and depressed responses to whisker stimulation. L4 neurons were more severely affected than L2/3 neurons. The response onset was significantly delayed in L4 cells. The peak response latency of L4 and L2/3 neurons was delayed significantly. In L2/3 and L4 of the barrel cortex there was a substantial increase in GAD65 (112% over controls) and much smaller increase in NMDAR1 (12-20%), suggesting enhanced inhibition in the PD cortex. These results show that chronic protein deficiency negatively affects both thalamo-cortical and cortico-cortical transmission during somatosensory information processing. The findings support the interpretation that sustained protein deficiency interferes with features of cortical sensory processing that are likely to underlie the cognitive impairments reported in humans who have suffered from prolonged protein deficiency.

Abnormal flash visual evoked potentials in malnourished infants: an evaluation using principal component analysis

OBJECTIVE

To characterize the morphology of flash visual evoked potentials (fVEPs) obtained from infants hospitalized with severe, chronic malnutrition (marasmus).

METHODS

A covariance-based principal component analysis with Promax factor rotation was applied to fVEPs obtained from malnourished infants and age-matched control subjects.

RESULTS

The analysis suggests the presence of a late positive complex in the fVEP, with at least one of its components being significantly diminished in marasmic infants. The N3 component was also diminished in marasmic infants. Following remediation, the marasmic group no longer differed with respect to these components. However, an abnormally large late, positive deflection was evident at discharge.

CONCLUSIONS

The fVEP morphology of infants hospitalized with severe malnutrition was found to be significantly different from age-matched controls. Moreover, although there was evidence of recovery following remediation, fVEPs continued to show abnormality at discharge, suggesting the possibility that nutritional rehabilitation did not fully eliminate the physiological deficit.

SIGNIFICANCE

Malnourishment during early infancy results in altered neurophysiological functioning, possibly in cortical areas responsible for higher order visual processing.

Auditory brainstem potentials in children with protein energy malnutrition

OBJECTIVE

In this study, auditory brainstem potentials (ABPs) were studied in children with protein energy malnutrition (PEM) to determine the effects of PEM on the developing brain in children.

METHODS

A total of 31 children, aged 3-36 months with moderate/severe PEM and 25 healthy children, aged 3-48 months were included in the study. Nutritional status of the children was assessed by the Gomez classification. Recordings of ABPs were performed by using Nihon Kohden Neuropack 2 device.

RESULTS

Of 31 children, 22 (71%) had severe malnutrition, 9 (29%) had moderate malnutrition. Additionally, 8 (26%) and 9 (29%) children had iron deficiency anemia and hypoalbuminemi, respectively. There were significant differences in the mean latencies of the waves I-V on the right and left ears and in the mean interpeak latencies (IPLs) of the waves III-V and I-V on the right ear between the study and control groups (P<0.05). The mean IPLs of I-V on the left side were found to be longer in the moderate PEM group than those of severe PEM group (P<0.05). There was not any difference between the groups of PEM with low serum albumin and PEM with normal serum albumin. While the mean IPLs of I-III on the right side were found longer in the cases of PEM without iron deficiency anemia, the mean latency of wave I on the left side, and the mean IPLs of III-V on the right side were longer in the children with PEM plus iron deficiency anemia (P<0.05).

CONCLUSIONS

Our findings showed that children with moderate/severe PEM had ABPs abnormalities in different degrees, which reflect defects in myelination of auditory brainstem pathways in children with moderate/severe PEM. However, we found contradictory results between abnormalities in ABPs and degree of malnutrition and iron deficiency anemia. We think that more extensive studies should be performed to determine whether or not there was a relationship between these parameters.

[The role of nutritional factors on the structure and function of the brain: an update on dietary requirements]

The brain is an organ elaborated and functioning from substances present in the diet. Dietary regulation of blood glucose level (via ingestion of food with a low glycemic index ensuring a low insulin level) improves the quality and duration of intellectual performance, if only because at rest the adult brain consumes 50 p. 100 of dietary carbohydrates, 80 p. 100 of them for energy purposes. The nature of the amino acid composition of dietary proteins contributes to good cerebral function; tryptophan plays a special role. Many indispensable amino acids present in dietary proteins help to elaborate neurotransmitters and neuromodulators. Omega-3 fatty acids provided the first coherent experimental demonstration of the effect of dietary nutrients on the structure and function of the brain. First it was shown that the differentiation and functioning of cultured brain cells requires omega-3 fatty acids. It was then demonstrated that alpha-linolenic acid (ALA) deficiency alters the course of brain development, perturbs the composition and physicochemical properties of brain cell membranes, neurones, oligodendrocytes, and astrocytes (ALA). This leads to physicochemical modifications, induces biochemical and physiological perturbations, and results in neurosensory and behavioral upset. Consequently, the nature of polyunsaturated fatty acids (in particular omega-3) present in formula milks for infants (premature and term) conditions the visual and cerebral abilities, including intellectual abilities. Moreover, dietary omega-3 fatty acids are certainly involved in the prevention of some aspects of cardiovascular disease (including at the level of cerebral vascularization), and in some neuropsychiatric disorders, particularly depression, as well as in dementia, notably Alzheimer's disease. Their deficiency can prevent the satisfactory renewal of membranes and thus accelerate cerebral aging. Iron is necessary to ensure oxygenation, to produce energy in the cerebral parenchyma, and for the synthesis of neurotransmitters. The iodine provided by the thyroid hormone ensures the energy metabolism of the cerebral cells. The absence of iodine during pregnancy induces severe cerebral dysfunction, leading to cretinism. Manganese, copper, and zinc participate in enzymatic mechanisms that protect against free radicals, toxic derivatives of oxygen. The use of glucose by nervous tissue implies the presence of vitamin B1. Vitamin B9 preserves memory during aging, and with vitamin B12 delays the onset of signs of dementia, provided it is administered in a precise clinical window, at the onset of the first symptoms. Vitamins B6 and B12, among others, are directly involved in the synthesis of neurotransmitters. Nerve endings contain the highest concentrations of vitamin C in the human body. Among various vitamin E components, only alpha-tocopherol is involved in nervous membranes. The objective of this update is to give an overview of the effects of dietary nutrients on the structure and certain functions of the brain.

Mild carbon monoxide exposure and auditory function in the developing rat

We have examined the influence of chronic mild exposure to carbon monoxide (CO) on cognitive (learning) and auditory function in the developing rat. We have demonstrated that the auditory pathway is compromised at exposures less than 50 ppm, whereas learning was not influenced at 100 ppm. Artificially reared rat pups were exposed to CO during the brain growth spurt and onset of myelination. Spatial learning was assessed using the Morris Water Maze and three tests of auditory function: (1) auditory brainstem conduction times; (2) the amplitude of the eighth nerve's action potential; and (3) otoacoustic emissions carried out on rat pups (age 22- 24 days). The pups were gastrostomy-reared on a rat milk substitute and chronically exposed to CO at discrete concentrations in the range of 12-100 ppm from 6 days of age to post-weaning at 21-23 days of age. We found no difference in auditory brainstem conduction times at all CO concentrations in comparison to non-exposed controls. There was a difference in otoacoustic emissions for test and controls at CO concentrations of 50 ppm but not at lower concentrations. There was a consistent attenuation of the amplitude of the eighth nerve's action potential, even at the lowest CO exposure examined. The attenuation of the amplitude of the action potential of the eighth nerve at 50 ppm carbon monoxide exposure did not completely recover by 73 days of age. We conclude that prolonged mild exposure to carbon monoxide during development causes measurable functional changes at the level of the eighth cranial nerve.