Visual Evoked Potential in Preterm Infants

OBJECTIVE: The maturation in the central nervous system and the myelination of visual pathway were shown to be reflected by the visual evoked potential (VEP) response recordings. The purpose of this study was to establish normal value of flash visual evoked potentials in preterm infants, especially left to right difference. METHOD: Forty-one preterm infants from 31 to 40 weeks of corrected age had been made VEP records using Cadwell Excel EMG/EP system. Some in whom weekly VEP records had been made at least 3 times were included in longitudinal study and others in occasionally VEP records were included in cross-sectional study. Infants with neurological problems or anomalies, perinatal infectious and other severe systemic disease were excluded. RESULTS: 1) In the VEP study, we were able to establish the reference ranges for N300 peak latency at various corrected ages. 2) The latency of N300 peak latency was not significantly correlated with birth weight, sex, head circumference. 3) The latency of N300 peak decrease linearly, the age increased and also the decrement of N300 peak latency was accelerated at 37 weeks of gestational ages. CONCLUSION: Although VEPs from preterm infants have several peaks, N300 latency is the most prominent and the most reproducible. It has been considered the most important component of the preterm VEPs.

An Isolated Musculocutaneous Nerve Palsy

The musculocutaneous nerve has a short course and is deeply placed before piercing the coracobrachialis muscle at the point where it is relatively fixed by branches along its course between biceps brachii and brachialis muscles. Therefore, an isolated palsy of the musculocutaneous nerve is extremely rare and usually caused by stab, cut or bullet injuries. An isolated musculocutaneous nerve palsy, sparing the coracobrachialis muscle, can occur after heavy exercise of the arm musculature and has a good prognosis. We report a patient with an isolated musculocutaneous nerve palsy caused by motorcycle accident.

Comparison between the Electric and Magnetic Stimulations for a Repetitive Nerve Stimulation Test

The low rate repetitive nerve stimulation test(RST) using the electric stimulation has been known the best procedure among the electroliagnostic evaluations for the neuromuscular transmission. However, the electric stimulation often causes a considerable discomfort and pain during the procedure. On the contrary, the magnetic stimulation is much easier and less painful in activating to activate the deep seated nerves. The purpose of this study was to compare the effect of repetitive magnetic and electric stimulation for the induction of compound muscle action potentials(CMAP) of abductor digiti quinti and deltoid muscles in 25 healthy subjects. The results were showed there were no significant differences in the amplitudes of CMAP of axillary and ulnar nerves between the magnetic and electric stimulations. And there were no significant differences in the decremental ratio of CMAP between the magnetic and electric stimulations. The magnetic stimulations were less painful for the subjects than electric stimulations in both proximal and distal muscles. In conclusion, the magnetic stimulation proved to be a useful method for repetitive nerve stimulations in the diagnosis of neuromuscular disease.

Brainstem Auditory Evoked Potential and Visual Evoked Potential of High Risk Infants

OBJECTIVE: Maturation of the acoustic and visual pathways in brainstem can be reflected by the brainstem auditory evoked potential(BAEP) and visual evoked potential(VEP) response studies. The purpose of this study was to evaluate the high-risk infants by the BAEP and VEP studies as a screening test for Their brainstem maturities. METHOD: The BAEP and VEP studies were used as a screening test in 142 high-risk infants with 31 to 42 weeks of conceptional age. Further follow-up data were obtained within 1 year in the same infants who showed the abnormal findings in BAEP and VEP at an initial screening test. RESULTS: On an initial BAEP and VEP study, the proportion of the abnormal findings was significantly higher among infants with below 36weeks(53.8%, 28.2%) of conceptional age than above 36 weeks(27.2%, 3.9%). At the follow-up study, 3 of 21 infants with no responses in BAEP and 1 of 6 infants with no responses in VEP on an initial test showed the persistent abnormal findings. However, normal configurations of BAEP and VEP were observed in infants with prolonged latencies or with distorted waveforms of BAEP and VEP at the first examination. CONCLUSIONS: These results suggest that the BAEP and VEP studies on the useful screening tests in infants above 36weeks of conceptional age. Because of the risk of persistent abnormal results, infants with no responses on an initial screening test need a follow-up study.