Improving the efficiency of Auditory Brainstem Responses in newborns, using a 60 clicks/s stimulation rate

The Effect of Different Stimulation Rates on Brainstem Auditory-Evoked-Potential Responses

Introduction  Auditory-evoked potentials are influenced by several factors, including polarity, filter, stimulus intensity and stimulation rate. The presentation of higher rates of stimuli per second enables the collection of a greater number of responses in a given period of time, promoting a shorter testing time; however, the collected recordings are subject to changes related to wave morphology. Objectives  To compare the brainstem auditory-evoked-potential responses with click stimulus with the most commonly used stimulation rates in the clinical practice. Methods  The present cross-sectional analytical study was performed with fifteen participants of both genders and normal hearing thresholds. The brainstem auditory-evoked potential was performed at four different stimulation rates (21.1, 26.7, and 27.7 stimuli/s, and a rate determined based on a mathematical calculation using the a measurement of the transmission frequency of the power grid at the time of the examination). Results  We observed that the rate of 21.1 stimuli/s showed the highest amplitudes for waves I, III, and V when compared with the other rates. The rate of 26.7 stimuli/s, when compared with 27.7 stimuli/s, showed a higher amplitude for wave V. The latency if wave V was significantly lower with the rate of 21.1 stimuli/s than with 27.7 stimuli/s. Conclusions  The stimulation rate interferes with wave latencies and amplitudes; its decrease from 27.7 to 21.1 stimuli/s decreases the latency of wave V and increases the amplitues and improves the morphology of waves I, III and V. In addition, we found evidence that suggests an improvement in the visualization of wave III by adjusting the stimulation rate based on a measurement of the local transmission frequency of the power grid.

Early detection and treatment of attention deficits in preterm and at term infants with risk factors for brain damage

Cognitive deficits in infants born preterm and infants at term with risk factors for brain damage are a common outcome. Attention deficits in preterm infants are related to the development of attention-deficit/hyperactivity disorder (ADHD), and therefore, there is a need for earlier evaluations and treatment procedures that are implemented before the presence of signs of ADHD.

METHODS

We studied preterm (74%) and term infants with the Infant Scale of Selective Attention (ISSA, Escala de Evaluación de la Atención Selectiva (EEAS), in Spanish). This scale evaluates both visual- and auditory-orienting attention. Two groups participated, one with attention deficits (n = 26) and another with regular performance (n = 36). An early attention-stimulation program (EASP) was implemented in the infant group with attention deficits from three to eight months of age. All infants underwent magnetic resonance imaging (MRI), and visual and auditory evoked responses were assessed.

RESULTS

All infants had prenatal and perinatal risk factors for brain damage and abnormal MRI findings, and the majority had abnormalities compatible with white matter injury. However, there were four infants with porencephalic cysts; 3 of them were in the treated group. At the beginning of the treatment, ISSA values showed differences between groups. These differences persisted for five months in the visual test and up to the sixth month in the auditory evaluation. Afterward, there were no significant differences, indicating that infants with attention deficits had satisfactorily responded to the treatment.

CONCLUSIONS

The ISSA is helpful for the early evaluation of visual and auditory attention. Infants with attention deficits react well enough after six months of EASP.

Visual evoked potentials are similar in polysomnographically defined quiet and active sleep in healthy newborns

Morphology and late components of evoked potentials change depending on wake-sleep stages in adults. Visual Evoked potentials (VEPs) have been frequently studied in newborns to identify abnormal development of visual pathways; however, large variability has been reported and there is uncertainty as to the effect of sleep stages on VEPs in neonates.

OBJECTIVE

To describe the characteristics of VEPs in one month old, healthy full-term newborns during active sleep (AS) and quiet sleep (QS), defined by simultaneous polysomnography (PSG).

METHODS

VEPs were obtained by monocular LEDs stimulation of each eye during AS and QS, in 20 healthy full-term newborns (gestational age 37-40 weeks) with normal birth weights and normal prenatal Doppler ultrasound indices. Latencies and amplitudes of N2, P2 and N3 components in AS and QS were compared, and their association with absolute power of EEG frequency bands, assessed.

RESULTS

There were no significant differences in VEP morphology, latencies and amplitudes between sleep states. Typical wave forms were obtained in all newborns in AS; however, no VEPs could be identified clearly in 3 newborns in QS; QS VEPs were less reliable than in AS: more averaging was required; correlation was significantly lower between the VEP averages; and a larger number of babies needed more than two averages to obtain replicable responses needed for clinical purposes.

CONCLUSIONS

These results indicate that changes in amplitude and latency of some VEP components observed in NREM and REM sleep in adults are not yet present in one month old newborns probably due to immaturity of cortical and sleep mechanisms. VEPs are more reliable during AS than QS in newborns. Systematic VEP recording during AS, and polysomnographic control to identify this stage, are highly recommended as methods that can increase there liability of neonatal VEPs.