Event-Related Brain Potentials in Patients with Hypothyroidism

The Effects of Six-Month L-Thyroxine Treatment on Cognitive Functions and Event-Related Brain Potentials in Children with Subclinical Hypothyroidism

OBJECTIVE

The aim of this study was to investigate the cognitive status of children with subclinical hypothyroidism (SH) before and after L-thyroxine (L-T4) treatment using event-related potentials (ERPs) and neuropsychological tests.

METHODS

This prospective study was conducted on a series of 20 children with mild SH (free T4 normal and thyroid-stimulating hormone level within 5-10 µIU/L) who underwent clinical and cognitive assessment before L-T4 treatment and 6 months afterwards. The recordings of ERPs were done at the time of diagnosis and after 6 months of euthyroid state. Neuropsychiatric tests for attention, perception, close and remote memory were performed on all patients and on the control group which consisted of 20 healthy children of normal intelligence.

RESULTS

While pretreatment verbal memory (VM) and verbal recall (VR) scores of the SH group were significantly lower than those of the control group (p=0.004 and 0.012, respectively), no significant differences between the post-treatment and control groups were found in these scores after 6 months of L-T4 treatment. Post-treatment VM and VR scores were significantly higher than the pretreatment scores in the SH group (p=0.008 and p=0.0001). There were no significant differences between the pre-and post-treatment values of electrophysiological evaluation in N1, P2, P3 latencies or P3 amplitude (p>0.05), although there was a significant decrease in N2 latency in the post-treatment group (p=0.03).

CONCLUSION

SH affects cognition in children and L-T4 replacement therapy leads to normalization of cognitive functions. Neuropsychological tests can be used as complementary measures in the evaluation of children with SH. Determining the association between ERPs and SH would contribute to the comprehensive evaluation of these children.

Advanced analysis of auditory evoked potentials in hyperthyroid patients: the effect of filtering

The purpose of the study is to evaluate Auditory Evoked Potentials (AEPs) in patients with hyperthyroidism and to compare their frequency components with those of healthy subjects. In this study the AEPs in hyperthyroidism were studied both in time and frequency domains rather than studying just in the time domain by peak scoring. This paper presents a method for filtering auditory oddball standard and target AEPs by using singular spectrum analysis (SSA) and feature extraction in the frequency domain via spectral analysis. AEPs were recorded during an auditory oddball paradigm in 25 newly diagnosed hyperthyroid patients and 15 healthy subjects. The signals are captured in the presence of ongoing background EEG activity so they are often contaminated by artifacts. This paper presents a method for filtering auditory odd-ball standard and target AEPs by using Singular spectrum analysis and feature extraction in frequency domain via spectral analysis. Information about the frequency composition of the signal is then used to compare normal and hyperthyroid states. While there was no significant difference either in the target or standard unfiltered signals between the hyperthyroid patients and the control group (p > 0.05), there was a significant difference in the filtered signals between the two groups (p < 0.01). In conclusion, our results revealed that SSA is an effective filtering method for AEPs. Thus, a much more objective and specific examination method was developed.