Electroretinogram by Donnell J Creel

Figure Reference: Med.Utah.edu (linked, pl click)

In general, intraopertive neurophysiological monitoring teams do not conduct ERG or EOG in the Operating room set up, it is rather cumbersome and difficult to get a reliable readings combined with the difficulty of placing the recording electrode and risks that are associated with the procedure.  However, Donnell in its Chapter on"The electroretinogram" presents the latest developments that record the status of retinal function using skin electrodes and he also sheds light on the recent advancement in ERG the multifocal retiongram. Whether you are going to conduct this test or not, if you are interested in all the evoked potentials and the basics, this is an excellent reading material. Enjoy.

 The Electroretinogram: Clinical Applications by Donnell J. Creel

Electrophysiological testing of patients with retinal disease began in clinical departments in the late nineteen forties. Under the influence of the Swedish pioneers, Holmgren (1865) and Granit (1933), the electroretinogram was being dissected into component parts and early intraretinal electrode studies were beginning to tell which cells or cell layers gave rise to the various components. A detailed discussion of the electroretinogram, or ERG as it is commonly abbreviated, is found in the accompanying chapter by Ido Perlman. A little after the introduction of the ERG as a test of the state of the patient’s retina, another diagnostic test called the electrooculogram (EOG) was introduced to the clinic (Arden et al., 1962). The EOG had advantages over the ERG in that electrodes did not touch the surface of the eye. The changes in the standing potential across the eyeball were recorded by skin electrodes during simple eye movements and after exposure to periods of light and dark. Over the years ERG recording techniques have become progressively more sophisticated in the clinical setting. With the advent of perimetry, optical coherence tomography (OCT) and pattern ERG techniques, more precise mapping of dysfunctional areas of the retina is now possible. The most recent advance in ERG technology is the multifocal electroretinogram (mfERG). The mfERG provides a detailed assessment of the health of the central retina.

Intraoperative Neurophysiological Monitoring, by Leon K Liem

eMedicine
Liem's article on "Intraoperative Neurophysiological
monitoring", a good place for starters to know the basics of
neuromonitoring.  Author: Leon K Liem, MD, Assistant Clinical Professor, Division of Neurological Surgery, University of Hawaii, John Burns School of Medicine

Contributor Information and Disclosures

Updated: Feb 11, 2010

Introduction

This article provides an overview of the various neurophysiological monitoring techniques used intraoperatively.
Intraoperative neurophysiological monitoring has been utilized in attempts to minimize neurological morbidity from operative manipulations. The goal of such monitoring is to identify changes in brain, spinal cord, and peripheral nerve function prior to irreversible damage. Intraoperative monitoring also has been effective in localizing anatomical structures, including peripheral nerves and sensorimotor cortex, which helps guide the surgeon during dissection.
Evoked potential monitoring includes somatosensory evoked potentials (SSEP), brainstem auditory evoked potentials (BAEP), motor evoked potentials (MEP), and visual evoked potentials (VEP). Electromyography (EMG) also is used extensively during operative cases. Scalp electroencephalography (EEG) provides data for analysis in SSEP, BAEP, and VEP. Scalp EEG also can be used to monitor cerebral function during carotid or other vascular surgery. In addition, EEG recorded directly from the pial surface, or electrocorticography (ECoG), is used to help determine resection margins for epilepsy surgery, and to monitor for seizures during electrical stimulation of the brain carried out while mapping cortical function. http://emedicine.medscape.com/article/1137763-overview

Neuron News:-

Neuron news is a WebRing site that publishes some cool topics in neuroscience, in this Nov 2008 news note, they talk about EcoG and developments in this neurotechnology?. I do not find anything new in this news as EcoG is already recorded in clinical set up, but the one thing that is interesting in this news is the type of electrode development, something that can sit on the surface of the brain without perturbations of membranes or causing any penetration that would be deleterious, anyways, there are lots of stuff to browse through including a lot on consiousness at neuronews.

Wave P300 (ERP) & Temporal Lobe Epilepsey

In this latest issue of the journal of Human Brain Mapping, the authors suggest that wave P300 an endogenous event related evoked potential seems to be altered in pateints with temporal lobe epilepsy, a change in the latency and amplitude of P300 was observed in 10 patients suffering from TLE (same number of normal recording was conduted for comparison). 

Hum Brain Mapp. 2008 Nov 25. [Epub ahead of print] 

Attention impairment in temporal lobe epilepsy: A neurophysiological approach via analysis of the P300 wave.

Bocquillon P, Dujardin K, Betrouni N, Phalempin V, Houdayer E, Bourriez JL, Derambure P, Szurhaj W.
Department of Clinical Neurophysiology, Lille University Medical Center, Lille, France.
Purpose:

Attention is often impaired in temporal lobe epilepsy (TLE). The P300 wave (an endogenous, event-related potential) is a correlate of attention which is usually recorded during an "oddball paradigm," where the subject is instructed to detect an infrequent target stimulus presented amongst frequent, standard stimuli.

Modifications of the P300 wave's latency and amplitude in TLE have been suggested, but it is still not known whether the source regions also differ. Our hypothesis was that temporal lobe dysfunction would modify the P3 source regions in TLE patients. Methods: A comparative, high density, 128-channel electroencephalographic analysis of the characteristics of P300 (P3b latency and amplitude) was performed in 10 TLE patients and 10 healthy controls during auditory and visual oddball paradigms. The P3b sources were localized on individual 3D MR images using the LORETA method and intergroup statistical comparisons were performed using SPM2(R) software. Results: Our main results (in both individual analyses and intergroup comparisons) revealed a reduction in temporal (and more particularly mesiotemporal) sources and, to a lesser extent, frontal sources in TLE patients, compared with controls. Discussion: This reduction may reflect direct, local cortical dysfunction caused by the epileptic focus or more complex interference between epileptic networks and normal attentional pathways. Hum Brain Mapp, 2009. (c) 2008 Wiley-Liss, Inc.

PMID: 19034898 [PubMed - as supplied by publisher]