Gaussian wavelet transform and classifier to reliably estimate latency of multifocal visual evoked potentials (mfVEP)

This paper describes a method to reliably estimate latency of multifocal visual evoked potential (mfVEP) and a classifier to automatically separate reliable mfVEP traces from noisy traces. We also investigated which mfVEP peaks have reproducible latency across recording sessions. The proposed method performs cross-correlation between mfVEP traces and second order Gaussian wavelet kernels and measures the timing of the resulting peaks. These peak times offset by the wavelet kernel’s peak time represents the mfVEP latency. The classifier algorithm performs an exhaustive series of leave-one-out classifications to find the champion mfVEP features which are most frequently selected to infer reliable traces from noisy traces. Monopolar mfVEP recording was performed on 10 subjects using the Accumap1™ system. Pattern-reversal protocol was used with 24 sectors and eccentricity upto 33°. A bipolar channel was recorded at midline with electrodes placed above and below the inion. The largest mfVEP peak and the immediate peak prior had the smallest latency variability across recording sessions, about ±2 ms. The optimal classifier selected three champion features, namely, signal-to-noise ratio, the signal’s peak magnitude response from 5 to 15 Hz and the peak-to-peak amplitude of the trace between 70 and 250 ms. The classifier algorithm can separate reliable and noisy traces with a high success rate, typically 93%.     

VEP鉴定伪盲眼的临床法医学研究

目的:探讨VEP技术在鉴别伪盲、评价伪盲眼实际视力水平方面的应用价值。方法:选取65例眼外伤后单眼盲或单眼低视力的患者为实验对象,将65只伤眼作为实验组,65只健眼作为对照组,分别行VEP检查。在VEP检查时,受检眼依次接受视角为30′、22′、11′、5′、3′的视觉刺激。结果:患眼主观视力与VEP视力不相符者48人,伪盲检出率为73.8%;对照组健眼VEP视力与主观视力符合率可达90.8%。结论:VEP技术能够准确评价受检眼的实际视力水平,并可为鉴别伪盲的法医学应用方面提供可靠依据。     

The challenge of CDG diagnosis

Congenital disorders of glycosylation (CDG) are a rapidly growing family of genetic diseases that currently includes some 130 different types. CDG diagnosis is a challenge, not only because of this large number but also because of the huge clinical heterogeneity even within a number of CDG. In addition, the classical screening test, serum transferrin isoelectrofocusing, is only positive in about 60% of CDG, and can even become negative in some CDG particularly in PMM2-CDG, the most frequent N-glycosylation defect. In order to facilitate CDG diagnosis, we hereby provide some practical tools: (1) a list of clinical features strongly suggestive of a distinctive CDG; (2) a table of clinical, biochemical and laboratory findings reported in CDG, arranged per organ/system; (3) an overview of the affected organs/systems in each CDG; and (4) a diagnostic decision tree in face of a patient with a suspicion of CDG. Most important is to keep in mind a CDG in any unexplained syndrome, in particular when there is neurological involvement.This mini-review enumerates clinical and biochemical hallmarks of these diseases and the biochemical and genetic testing available, and provides an updated list and information on identified CDG. The main aim is to act as a CDG diagnosis simplified guide for healthcare professionals and, additionally, as an awareness and lobbying tool to help in the effectiveness and promptness of CDG diagnosis.     

The hemispheric distribution of the transient rat VEP: a comparison of flash and pattern stimulation

Summary We investigated the hemispheric distribution of the rat visual evoked potential (VEP) to pattern reversal and flash stimuli, presented monocularly at a rate of 1 Hz. Pattern VEP components could be recorded only over an area bounded by the anatomical coordinates of area 17, while some flash VEP components were recordable outside the primary visual area. Monocular pattern stimulation, as expected, evoked dominant contralateral VEPs. Surprisingly, ipsilateral responses could be also recorded with the reference electrode near the nasal bone. These VEPs showed partial polarity inversion compared to the contralateral EPs. To assess the origin of the ipsilateral EPs, we also recorded EPs following surgical deafferentation of the ipsilateral cortex. Our data reveal that ipsilateral VEPs represent volume conducted potentials.