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Neurologic Diagnosis
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Evoked potentials retain a diagnostic role, but this has been greatly diminished since the advent of MRI, which has a higher sensitivity in lesion detection. Evoked potentials remain important in assessing patients who cannot be tested clinically, such as those suspected of having psychogenic loss of function, functional jerky movements, and most particularly in intraoperative monitoring.
Cortical-evoked potentials from deep brain stimulation
Published in Hans O Lüders, Deep Brain Stimulation and Epilepsy, 2020
Kenneth B Baker, Erwin B Montgomery
Exogenous-evoked potentials are useful for helping to identify functional connections or pathways within the nervous system and, as an extension of the clinical examination, can provide an objective measure of the integrity of those pathways. The focus of the typical, short-latency clinical-evoked potential examination is to study neural conduction along well-understood sensory pathways in an effort to detect the presence of clinical abnormalities. For the most part, however, such studies in humans are limited to accessible pathways and typically are evoked by stimulation of the extremes of a given subsystem (i.e. sensory receptors, peripheral nerves). Basic science takes advantage of concepts similar to the evoked potential in the form of, for example, peri-event rasters or histograms, which are based on the time-locked effects of some behavior or evoking event on neuronal activity. Using non-human animal models, investigators are able to explore various regions of the brain directly, deriving information pertaining to the nature of the interconnectiv-ity and dynamics between those regions. Unfortunately, our ability to apply such direct techniques, whether based on micro- or macrolevel recordings, specifically for the purpose of exploring functional cortico- subcortical networks is typically quite limited in humans.
Monitoring Disease Activity in Multiple Sclerosis
Published in Richard K. Burt, Alberto M. Marmont, Stem Cell Therapy for Autoimmune Disease, 2019
The use of evoked potentials for monitoring disease activity has been controversial. Many studies supporting their use were performed before the widespread availability of MRI.45,46 Multimodality (visual, brainstem and median somatosensory evoked potentials) were used in a clinical trial of azathioprine. A statistically significant difference in EP stability was evident with one treatment, not evident with placebo or the other treatment arm. A similar pattern was seen in the clinical examination, but did not reach statistical significance.45 Correlation between clinical and evoked potential abnormalities has been poor in other studies.47 Visual evoked potentials, generally easy to perform and well tolerated, may be the most sensitive evoked potential for therapeutic trial.45 Further consideration of EPs for clinical trial may be dependent on the specific question of the clinical trial. For example, visual evoked potentials (VEPs) may be most useful in assessing therapy aimed at treating or stabilizing visual loss. Most large trial do not incorporate evoked potentials because MRI has been considered superior to quantify extent of disease, including “silent disease,” which traditionally was detected by evoked potentials.
Transverse myelitis associated with primary biliary cirrhosis: clinical, laboratory, and neuroradiological features
Published in International Journal of Neuroscience, 2022
Mangsuo Zhao, Mingjie Zhang, Shimei Zhou, Bingxin Shi, Yan Wei, Fangjie Huang, Jing Wang, Jingfeng Huang, Liyan Qiao
On laboratory workup, the results of routine blood tests, urine test, stool analysis, and measurements of liver, renal, and thyroid functions, homocysteine, folic acid, and vitamin B12 levels, and the erythrocyte sedimentation rate (ESR) were all within the normal limits. Anti-nuclear (ANA), anti-double-stranded DNA, anti-extractable nuclear antigen, and anti-neutrophil cytoplasmic antibodies were not found in the serum. The results of routine and biochemical tests of the cerebrospinal fluid (CSF) were normal. Oligoclonal bands (OB) were positive. Anti-AQP4 IgG was not detected in serum or CSF. Serum and CSF were negative for the following antibodies: anti-N-methyl-d-aspartic acid receptor, anti-contactin-associated protein-like 2, anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor 1 and 2, anti-leucine-rich glioma-inactivated 1, anti-gamma-aminobutyric acid B receptor, and anti-dipeptidyl-peptidase-like protein 6 for autoimmune encephalitis. As biomarkers of paraneoplastic syndromes, Hu (anti-neuronal nuclear antibody 1), Yo (Purkinje cell autoantibody, PCA1), Ri (anti-neuronal nuclear antibody 2), Ma2, CV2/CRMP5, and amphiphysin were not detected in serum or CSF. Magnetic resonance imaging (MRI) studies of the brain and spinal cord were performed. Abnormal enhancement of the spinal cord was observed at T8–T9, suggestive of incomplete TM (Figure 1). Brain MRI showed no obvious abnormalities. Visual evoked potential and brainstem auditory evoked potential were within the respective normal ranges. The P40 wave of the somatosensory evoked potential disappeared bilaterally.
Developing therapeutic strategies to promote myelin repair in multiple sclerosis
Published in Expert Review of Neurotherapeutics, 2019
Laura E. Baldassari, Jenny Feng, Benjamin L.L. Clayton, Se-Hong Oh, Ken Sakaie, Paul J. Tesar, Yanming Wang, Jeffrey A. Cohen
Evoked potentials are objective, noninvasive, in vivo electrophysiological measures that assess the function of the CNS sensory and motor pathways. Many of the symptoms in MS result from abnormal nerve impulse generation and axonal conduction resulting from demyelination [73]. Therefore, evoked potentials have been used as outcome measures in several recent remyelination trials. After standardized repetitive stimulus administration, the amplitude and latency of the resultant summated response in the corresponding tract can be quantified. Reduced amplitude reflects a decreased number of functional axons. Axonal demyelination results in both conduction delay (increasing latency) and block (reducing amplitude). Several evoked potential modalities can be measured in MS. VEPs assess functional integrity of the afferent visual pathways from the optic nerve to occipital cortex. Somatosensory evoked potentials (SSEPs) assess functional integrity of the sensory pathways from the upper or lower limbs to parietal cortex. Brainstem auditory evoked potentials assess conduction from the cochlea to temporal cortex. Motor evoked potentials (MEPs) assess motor pathways from motor cortex to target muscles.
Proceedings of the 42nd Annual and First Virtual Upper Midwest Neuro-Ophthalmology Group Meeting, 24 July 2020
Published in Neuro-Ophthalmology, 2020
Salma Yassine, Francisco R. Sanchez Moreno, John J. Chen, Collin McClelland
Ashwini Kini, MD, University of Kentucky, described a 19-year-old male referred to the neuromuscular clinic for evaluation of peripheral neuropathy and the inability to walk since childhood. Neuro-ophthalmic examination revealed diffuse limitations of eye movements consistent with chronic progressive external ophthalmoplegia. Visual acuity was mildly diminished and OCT showed thinning of the RNFL. Visually evoked potentials were delayed further indicating bilateral optic neuropathy. In addition, ERG showed mild cone dysfunction. Genetic testing was positive for a polymerase gamma (POLG) mutation rendering a final diagnosis of a mitochondrial myopathy secondary to Alpers syndrome. Unfortunately, the patient succumbed at age 27 after going into status epilepticus.