MRI of optic nerve and postchiasmal visual pathways and visual evoked potentials in secondary progressive multiple sclerosis

We studied the relationship between abnormalities shown by MRI and functional disturbances in the visual pathway as assessed by the visual evoked potential (VEP) in 25 patients with established multiple sclerosis (MS); only 4 of whom had a history of acute optic neuritis. Optic nerve MRI was abnormal in 19 (76%) and is thus useful in detecting subclinical disease. Optic nerve total lesion length and area on the STIR sequence was found to correlate significantly with prolongation of the VEP latency. This may reflect a predominantly demyelinating rather than inflammatory origin for the signal change in the optic nerve.     

Visual evoked potentials in multiple sclerosis

A study was carried out of 32 patients suffering from multiple sclerosis the diagnois of which was quite definite according to Mac Alpine's criteria and which had developed over more than two years. Comparison was made with patient suffering from optic neuritis of a different aetiology and with normal subjects. The method of investigation was dynamic electroretinoencephalography : the visual evoked potentials were investigated after stimulation by white and coloured light before and after adapatation to darkness. The specificity of the results was tested by, firstly, electro-retinogram recording for control of the visual system, and secondly, by the recording of auditory evoked potentials for control cerebral function. Abnormalities in visual evoked potentials were found in 77 percent of the cases. In particular, there was delayed latency, that is, a slowing of retino-cortical conduction. The significance of these abnormalities is discussed, by analyzing the electroclinical correlationships according to whether there was obvious or subclinical optic neuritis, and the dissemination, activity or duration of the disease. The incidence of visual evoked potential abnormalities was considerably greater than that in optic neuritis (35 percent). The links between abnormalities in nervous conduction and demyelinisation are emphasized. The role and specificity of electrophysiological investigation in diagnosis of multiple sclerosis are discussed.     

The use of the auditory evoked potential in the diagnosis of multiple sclerosis

Auditory evoked potentials, both early and middle components, were recorded from 227 patients with a variety of conditions including multiple sclerosis, brain stem vascular disease, intracranial tumours and Arnold-Chiari malformation. Abnormalities were found in a substantial proportion of patients with definite multiple sclerosis and a smaller proportion of those in the less definite clinical categories of this condition. There was a high correlation between clinical evidence of brain stem involvement and an abnormal auditory evoked potential in multiple sclerosis. Abnormalities were also found in a few patients presenting with an isolated episode of central nervous system dysfunction involving the brain stem. The auditory evoked potential was abnormal in other patients with known diagnoses including half of those with Arnold-Chiari malformation. Tumours involving the brain stem caused abnormalities of the brain stem evoked potentials in some cases and more frequently distortion of the middle components. The specificity of these auditory evoked potential abnormalities to multiple slcerosis is discussed.     

MRI and brainstem auditory evoked potential evidence of eighth cranial nerve involvement in multiple sclerosis

An MS patient experienced sudden hearing loss. Brainstem auditory evoked potentials, previously normal, showed substantial abnormalities that suggested the impairment of the distal part of the acoustic nerve. MRI detected a small hyperintense lesion along the acoustic nerve; the lesion decreased in size and then disappeared after steroid treatment. This demonstrates that a demyelinating lesion in the distal tract of the eighth cranial nerve may cause an acute hearing loss in MS.     

Pudendal nerve somatosensory evoked potentials in probable multiple sclerosis

One of the most frequent causes of sensorineural hearing loss in childhood is damage to outer hair cells of the cochlea. The presence of otoacoustic emissions, generated by outer hair cells, provides evidence for normal hearing. This finding, however, may give rise to false reassurance, because even severe hearing loss, localized behind the cochlea, can be associated with normal otoacoustic emissions. The coexistence of otoacoustic emissions and hearing loss calls for the prompt exclusion of neurological disease.     

Shifts of visual spatial attention modulate a steady-state visual evoked potential

An uncertain relation between health and angry/hostile behaviour exists in the literature on adolescents. With data from a pilot study, one possible reason for this is explored: health measures such as blood pressure as well as angry/hostile behaviours may change with, or depend upon physical maturity, body size and body fatness. The sample consists of 60 African-, Hispanic-, and Anglo-American adolescents (15 to 16 years of age) drawn from a public school in Houston, TX. Using resting diastolic blood pressure as a model, in a sex stratified analysis, the following conclusions were reached: Physical maturity in girls and body height in boys were related to ethnicity in the sample and were confounders of the blood pressure and anger relationship. In girls secretive anger ('anger-in') and hostility were associated with increased body fat; expressive anger ('anger-out') in boys is associated with increased conicity (central body fat distribution) (p < 0.01). These associations were independent of height and physical maturity. Hostility was not significantly related to diastolic blood pressure in boys after adjusting for height and conicity. 'Anger-in' was significantly and positively related to diastolic blood pressure in girls (p < 0.01). This relationship was strongly mediated by per cent body fat, because the association of 'anger-in' and blood pressure was no longer statistically significant when the model included body fat. The results suggest that measures of physical maturity and more refined measures of body fat and body fat distribution should be considered in studies attempting to link adolescent blood pressure with anger expression.     

The Pulfrich spatial frequency phenomenon: a psychophysical method competitive to visual evoked potentials in the diagnosis of multiple sclerosis

The results of a study in which visual evoked responses (VERs) and a modified Pulfrich method were compared showed that both methods are very effective for the diagnosis of multiple sclerosis. With VERs, 97% of the multiple sclerosis cases were diagnosed correctly, while the corresponding value for the Pulfrich method was 93%. In contrast to VERs, the Pulfrich method allows only measurement of latency differences between the two visual pathways. This method involves measuring the speed required to cause a shift in the apparent depth location of a large, moving, striped pattern observed with a neutral density filter over one eye. A pathological transmission time was inferred when the patients observed a shift in the depth of the moving pattern either without any filter at all or with a filter whose attentuation was no more than 0.2 log units. A further criterion for pathology was a difference of more than 10% between the two eyes in the retinal speed required for a depth displacement using a 1.5 log unit filter. This test requires about 15 minutes, and can be carried out by a technical assistant.     

Investigation of multifocal visual evoked potential in anisometropic and esotropic amblyopes

PURPOSE: To investigate the variation of visual evoked potential (VEP) function at different eccentricities of the visual field in esotropic amblyopes and anisometropic amblyopes. METHODS: Data from 5 esotropic amblyopic eyes, 6 anisometropic amblyopic eyes, and 45 control eyes were analyzed. A VERIS system was used to generate a stimulus matrix containing 61 hexagons on a computer monitor. Each hexagon of the display contained a number of small black and white hexagonal patches that reversed in polarity during stimulation according to a pseudorandom binary m-sequence. The VERIS system extracted the local responses by cross-correlating the input and output signals. The latencies and amplitudes of the responses from the central 8.6 degrees of arc in the visual field were analyzed. RESULTS: In esotropic amblyopia, the multifocal VEP latency is prolonged, and the amplitude is reduced in the central region of the visual field. The mean amplitude is significantly smaller, and the mean latency is significantly longer in the temporal visual field than in the nasal visual field. In anisometropic amblyopia, latencies are markedly prolonged, and the amplitudes of multifocal VEP are attenuated in the central region of the visual field, and these effects are lessened in the periphery. CONCLUSIONS: The results are in agreement with psychophysical studies reporting a greater foveal deficit in amblyopia and a greater visual loss in the temporal field than in the nasal field in esotropic amblyopia.     

Age differences in visual evoked potential estimates on interhemishperic transfer.

Twenty-six younger (ages 18–36 years) and 19 older (ages 60–88 years) healthy right-handed men and women were tested for interhemispheric transfer by using visual evoked potentials lo laterally presented checkerboards. Interhemispheric transfer time (IHTT) was estimated by subtracting latencies for both P100 and N160 peaks of the waveform contralateral to the stimulus from the waveform ipsilateral to the stimulus for homologous sites. The quality of interhemispheric transfer was estimated by comparing peak-to-peak amplitudes for homologous sites. IHTT did not change across age, but there was a suppression of the waveform over the indirectly stimulated hemisphere in the older participants. The significance of this finding for age-related changes in functions mediated by the corpus callosum is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brain-stem trigeminal and auditory evoked potentials in multiple sclerosis: physiological insights

Although suramin has long been used to treat human trypanosomiasis, recent clinical trials have tested its efficacy against the acquired immunodeficiency syndrome (AIDS) and various malignancies. Thromobocytopenia was observed in early trials with suramin in AIDS, but has been uncommon in patients treated for solid tumors. Here we describe 5 patients out of a total of 67 (7%) who developed severe thrombocytopenia while receiving suramin as part of a phase II clinical trial for metastatic prostate carcinoma refractory to hormonal therapy. IgG purified from one patient's plasma caused suramin-dependent platelet aggregation. There was also evidence of crossreactivity between suramin and heparin in this system. An immune mechanism, however, could not be documented in the other cases, suggesting that multiple mechanisms may be responsible for severe thrombocytopenia in this patient population.     

Fast visual evoked potential input into human area V5

Studies of the human visual cortex have demonstrated that an area for motion processing (V5) is located in the lateral occipito-temporal cortex. To study the timing of arrival of signals in V5 we recorded multi-channel visual evoked potentials (VEPs) to checkerboard stimuli. We then applied dipole source analysis which was computed on a grand average of 10 subjects, and on five individual subjects, respectively. We demonstrate an early VEP component with onset before 30 ms and with a peak around 45 ms, located in the vicinity of V5. This early component was independent of a second activity, which started around 50 ms and peaked around 70 ms, and was located within the striate cortex (V1). These results provide further evidence for a very fast input to V5 before activation of V1.     

Correlations of evoked potentials with MR imaging and MR spectroscopy in multiple sclerosis

The current state-of-the-art imaging technique in multiple sclerosis (MS) is magnetic resonance (MR) imaging. With improved imaging technology, MR spectroscopy offers the capacity to identify those chemical changes associated with MS and promises to enhance our ability to understand this disease. Physiologic function in the central nervous system can be measured using evoked potentials. This article analyzes the correlation between these two techniques.     

The metabolic characteristics of patients with multiple sclerosis

A comprehensive clinical and biochemical evaluation has been carried out in patients with multiple sclerosis (MS). Measured in the patients' blood were levels of cholesterol, triglycerides, malonic dialdehyde, and superoxidedysmutase activity. The interrelationship revealed between the above measures provides a deeper insight into the mechanisms of pathometabolism in MS.     

Effect of luminance on visual evoked potential amplitudes in normal and disabled readers

Adsorption of four 5-pyrazolone derivatives and two carboxylic acids from aqueous solutions was studied. Partition coefficients for the analyzed drugs were calculated. Good corelation between log(k1, k2) (Langmuir constants) and log (octanol-water partition coefficient) of the drugs were found. The higher log(k1k2) value the higher solubility of the non-narcotic and analgetic drugs.     

Cortical and subcortical visual evoked potential correlates of reaction time in monkeys.

Investigated the relationships between reaction time (RT) and evoked potentials in 3 monkeys ( Macaca nemestrina ) during the performance of a simultaneous brightness discrimination task. Evoked potentials from the lateral geniculate, medial and inferior pulvinar, midbrain reticular formation, hippocampus, and striate and prestriate cortex were recorded concurrently with RT in response to the discriminative stimuli. An early component of the geniculate response and a late positive wave in striate cortex were found to be related systematically to RT. These components were largest for short RTs and diminished progressively in amplitude as RT lengthened. The statistical significance of these relationships is supported by a detailed analysis of single trials. The increases in amplitude of evoked potentials associated with short RTs are attributed to increased arousal level and are discussed in terms of reticular formation modulation of central excitability levels. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual evoked potential assessment of the effects of glaucoma on visual subsystems

The purpose of this study is to test the hypothesis that glaucoma leads to selective deficits in parallel pathways or channels. Sweep VEPs were obtained to isolated-check stimuli that were modulated sinusoidally in either isoluminant chromatic contrast or in positive and negative luminance contrast. Response functions were obtained from 14 control subjects, 15 patients with open-angle glaucoma, and seven glaucoma suspects. For all three groups of subjects we found characteristic differences between the VEP response functions to isoluminant chromatic contrast stimuli and to luminance contrast stimuli. The isoluminant chromatic stimulus conditions appeared to favor activity of the P-pathway, whereas the luminance contrast stimuli at low depths of modulation favored M-pathway activity. VEP responses for patients with OAG were significantly reduced for chromatic contrast and luminance contrast conditions, whereas VEP responses for glaucoma suspects were significantly reduced only for the 15-Hz positive luminance contrast condition. Our results suggest that both M- and P-pathways are affected by glaucoma.     

Effects of prefrontal cortex lesions on visual evoked potential augmenting/reducing

Visual evoked potentials to 4 stimulus intensities were recorded from Fz, Cz, and Oz, all referred to A2, in 23 neurologically normal subjects and 21 neurosurgical patients with prefrontal lesions. The response amplitude as a function of intensity was evaluated for P1/N1 and N1/P2 components. At the Oz lead, the EP amplitude consistently increased with brighter stimuli more rapidly in the prefrontal group than in the controls. Similar, though less consistent, effects were seen at Fz and Cz. These findings suggest that the phenomenon of augmenting/reducing is at least partially influenced by prefrontal-mediated inhibition of sensory processes.     

Visual evoked potential characteristics and early diagnosis of Pelizaeus-Merzbacher disease

OBJECTIVE: Early diagnosis of Pelizaeus-Merzbacher disease; assessment of disease progression. DESIGN: Pediatric neuro-ophthalmology evaluation of visual function with pattern and luminance visual evoked potentials; behavioral state assessment; electrophysiological diagnostic test; baseline estimates at the age of 11 weeks; 1-year follow-up. SETTING: University hospital electrodiagnostic vision research laboratory. PATIENTS: Case study: X-linked Pelizaeus-Merzbacher disease; leukodystrophy; patient tested at the age of 11 weeks and at the age of 58 weeks for follow-up; five age-matched normal controls. INTERVENTIONS: Physical therapy, medication, evaluation. MAIN OUTCOME: Early diagnosis; diagnostic confirmation; objective monitor of disease progression. RESULTS: Abnormal spatial and temporal vision and abnormal visual pathway maturation; visual evoked potentials of proband with Pelizaeus-Merzbacher disease were grossly abnormal, reflecting myelination disorder. CONCLUSIONS: Visual evoked potential pediatric electrodiagnosis yields reliable measures of visual function and visual system maturation in leukodystrophy.