The hematological and electrophysiological effects of cobalamin. Deficiency secondary to vegetarian diets.
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Adult↗
Biomedical subjects
A Kriss
Publications and source records attributed to A Kriss.
Ophthalmologic assessment of young patients with Alport syndrome.
BACKGROUND: Alport syndrome is an X-linked disease affecting basement membrane collagen. It is characterized by nephritis associated with high-tone sensorineural hearing impairment and ophthalmic signs. Although ocular changes have been described in adults, few data exist regarding the incidence of abnormal ocular features in adolescence and childhood. METHODS: Fifteen male and five female patients with Alport syndrome underwent ophthalmologic, audiologic, and nephrologic assessments. All patients studied had hematuria and a positive family history of Alport syndrome. Thirteen patients had a renal biopsy that showed characteristic electron microscopic changes of the disease. Eleven patients had high-tone sensorineural impairment. Electrophysiologic investigations performed included electroretinography, visual-evoked potentials, and electro-oculography. RESULTS: Two patients had early signs of anterior lenticonus, three had flecks in the retina, and two patients also had posterior subcapsular cataracts. None of the patients had significant electrophysiologic abnormalities. CONCLUSION: These findings indicate that ocular changes are uncommon and subtle in young patients with Alport syndrome, and suggest that the signs increase in frequency and severity with age.
Adolescent↗
Electrophysiological assessment of visual pathway function in infants.
The flash ERG and VEP have conspicuous immature features during the first 4 months following birth. The most marked maturational changes occur in ERG amplitude and VEP latency. Concurrent recording of the skin ERG and VEP provides information which is very useful in helping to arrive at a diagnosis in the young infant with nystagmus who appears to be blind and has a fundus of normal appearance. ERG and VEP features associated with Leber's Amaurosis, congenital cone dysfunction, albinism, optic nerve hypoplasia and unilateral hemisphere dysfunction are described.
Electroretinography↗
Neonatal cataract: aetiology, pathogenesis and management.
We review the epidemiology, aetiology, pathogenetic mechanisms and clinical management of neonatal cataract. Visual development and the effects of visual deprivation in the infant with congenital cataract are discussed and related to the timing of surgery. Surgical techniques and the important operative and post-operative complications are discussed. We review post-operative management and compare the different techniques available for aphakic correction, and describe the VEP changes found in patients with monocular cataract.
Cataract↗
The electroretinogram in infants and young children.
Electroretinography (ERG), especially when combined with visual evoked potential recording, can provide valuable information to the pediatric clinician assessing a young child with nystagmus who appears not to see. ERG changes are described in clinical conditions affecting rod and/or cone function, vitreoretinal disease, maculopathies, and disorders involving the retina and central nervous system. The role of ERG in monitoring treatment, and in excluding retinal disease prior to eye surgery, is also covered.
Child↗
Aspects of albinism.
Genetic, clinical and electrophysiological aspects of albinism are described. Emphasis is placed on electrophysiological features which help to distinguish albinism from other clinical conditions, and on stimulating and recording factors which can affect the clarity of VEP results.
Albinism, Ocular↗
The use of video in assessing and illustrating abnormal eye movements in young children.
Eye movement studies can be useful in neuro-ophthalmological investigations of infants and young children. In our laboratory we use a combination of an electro-oculogram and video to record eye movements. A composite video image is created consisting of an image of the electro-oculographic eye movement trace superimposed on an image of the patient's eyes and face. This permits the qualitative clinical appearance of the case to be illustrated simultaneously with the quantitative eye movement trace.
Electrooculography↗
Abnormalities of the electroretinogram and visual-evoked potential in vitamin E deficient rats.
Flash electroretinograms, retinal oscillatory and cortical visual-evoked potentials were recorded in 10-month vitamin E deficient rats and in age-matched controls. A significant increase in the latency (P less than 0.0001) and decrease in amplitude (P less than 0.0001) of the electroretinogram a- and b-waves were observed in the vitamin E deficient rats compared with controls. The vitamin E deficient rats also showed a significant delay (P less than 0.002) in early oscillatory potentials. No significant group differences were obtained in the P1 latency or P1-N1 amplitude of the visual-evoked potential; however, the N1 peak was significantly delayed (P = 0.01) in the vitamin E deficient rats. This study shows, for the first time, that the electroretinogram and visual-evoked potential to flash stimulation provide a sensitive index for monitoring the visual effects of vitamin E deficiency in the rat.
Animals↗
Effects of pentobarbital and ketamine-xylazine anaesthesia on somatosensory, brainstem auditory and peripheral sensory-motor responses in the rat.
Somatosensory, brainstem auditory evoked and peripheral sensory-motor responses were recorded in rats anaesthetized with either pentobarbital or a ketamine-xylazine combination. This was carried out in order to assess which of these agents degraded responses to a lesser extent and thus would be more suitable for monitoring experimental effects. Neither of the anaesthetic agents affected peripheral sensory or motor conduction, nor were there any interpeak latency changes of the early components of the brainstem auditory response. However, pentobarbital anaesthesia resulted in an increase in latency of the initial positive component of the somatosensory cortical evoked potential and attenuation of the following negative component. During the recovery stages of ketamine-xylazine anaesthesia the longer latency evoked potential components were observed to emerge.
Animals↗
A longitudinal study of somatosensory, brainstem auditory and peripheral sensory-motor conduction during vitamin E deficiency in the rat.
A severe deficiency of vitamin E causes a characteristic neurological syndrome in man and experimental animals. In this study a number of electrophysiological modalities in vitamin E deficient and control rats have been investigated over a period of one year to define the time of onset and severity of the abnormalities associated with vitamin E deficiency in the rat. The mean velocities (n = 10) of the sensory evoked potentials were slower at all time points in the vitamin E deficient rats, with the central conduction velocities being more severely affected than the peripheral. Central conduction velocities, following both tibial and median nerve stimulation, were significantly delayed (P less than 0.005) after 8 months of deficiency. Differences in peripheral conduction following tibial stimulation became significantly delayed (P less than 0.005) after 11 months of deficiency. There were no significant differences in the brainstem auditory evoked potentials or peripheral sensory motor responses between the vitamin E deficient and control rats over the 1 year period. These results in the rat are essentially similar to those previously reported in vitamin E deficient man.
Animals↗
Albinism in childhood: a flash VEP and ERG study.
Flash visual evoked potentials (F. VEPs) and electroretinograms (ERGs) were recorded in a total of 20 young children with albinism (age range 5 months to 11 years, mean 4 years). All recordings were made without sedation. There were 13 oculocutaneous cases (one with Hermansky-Pudlak syndrome) and seven ocular albinos. Monocular flash stimulation commonly elicited an asymmetrical occipital VEP distribution with a well lateralised component at around 80 ms which was of opposite polarity in a comparison of VEPs from each eye. None of the normally pigmented matched controls or obligate female carriers showed this anomalous distribution. The albino electroretinogram, compared with controls, recorded under fully darkened conditions had a significantly larger a wave and significantly shorter latencies for both a and b waves. The accentuated ERG and asymmetrical VEP recorded in infants and young children with albinism permits distinction of these patients from those with congenital cone dysfunction and idiopathic nystagmus, with whom they may be confused by a clinical examination only.
Albinism↗
Childhood albinism. Visual electrophysiological features.
Flash ERGs and VEPs, and VEPs to pattern onset and pattern reversal stimulation were recorded in young albino children and compared to age-matched, normally pigmented, controls. In albinos, the ERG had a significantly larger a-wave, and significantly shorter latencies for both the a-wave and b-wave. VEPs to flash, pattern onset and pattern reversal stimulation all showed an occipital crossed asymmetry when comparing responses from each eye. However, the findings for flash stimulation were more consistent and reliable than those to either form of pattern stimulation.
Albinism, Ocular↗
The effect of experimental 'scotomata' on the ipsilateral and contralateral responses to pattern-reversal in one half-field.
The averaged cortical responses to a reversing checkerboard pattern presented monocularly in either left or right visual half-fields have been recorded from the occipital scalp using a transverse chain of widely spaced electrodes referred to a common mid-frontal electrode. The half-field responses showed a consistent asymmetry, the dominant feature of which was a positive wave (P100) that was widespread on the ipsilateral scalp and maximally recorded from the midline and ipsilateral electrodes. This formed part of the triphasic negative-positive-negative complex, the other two components being an N75 and an N145. On the contralateral scalp it was generally possible to record a triphasic complex of opposite polarity, but this was usually of smaller amplitude and its components (P75, N105, P135) showed greater variation in latency and morphology than the ipsilateral components. With progressive occlusion of the pattern stimulus from the central regions of the visual half-field, the ipsilateral positive wave (P100) was increasingly attenuated, while components of the contralateral complex were relatively unaffected, or, in some cases, enhanced. By contrast, reducing the radius of the stimulated area had relatively little effect on the ipsilateral P100, while the contralaterally recorded response was attenuated. These differential effects on the half-field response components are discussed in relation to the anatomy of the central and paracentral cortical representation of the visual field. The implications for the interpretation of evoked potential recordings in patients with field defects are considered.
Adolescent↗
EEG immediately after unilateral ECT.
EEG was continuously recorded in 15 patients for a period extending from just before to 1/2 hour after unilateral ECT. Fourier analysis was performed on the EEG following 15 right-sided treatments and five left-sided treatments. During the induced seizure, epileptic slow-wave activity had significantly greater power on the treated side. Immediately after the seizure, there was significantly more delta activity and less alpha and beta activity on the treated side. This asymmetry, though becoming less marked, was usually still present at the end of the recording period. Analysis of other variables associated with the treatment showed that there was a significant correlation between the time to eye-opening after ECT and both the duration of the seizure and the amount of anaesthetic administered. The similarity between these induced unilateral seizures and unilateral seizures occurring spontaneously in some epileptics is discussed.
Adolescent↗
Neurological asymmetries immediately after unilateral ECT.
Twenty-nine right handed patients were examined neurologically before and immediately after each of 62 unilateral ECTs to the dominant and non-dominant hemispheres. Most convulsions were followed by signs of transitory neurological dysfunction referable to the treated hemisphere. These signs included deep tendon reflex asymmetry, hemiparesis, tactile and visual inattention, and homonymous hemianopia. After treatment to the right hemisphere some patients had left visuospatial neglect, while all patients who had dominant hemisphere ECT were transiently dysphasic. All neurological abnormalities tested resolved within 20 minutes of treatment.
Aphasia↗
A paradox in the lateralisation of the visual evoked response.
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Adult↗
The pattern-evoked potential in compression of the anterior visual pathways.
Pattern evoked responses have been recorded in 19 patients with compression of the optic nerve, chiasm or tract, verified at operation. These included 4 patients with orbital tumours, 5 with intracranial meningiomas, 2 with craniopharyngiomas and 8 with pituitary tumours. The evoked response was abnormal in all except one of these patients. The pattern of abnormalities in the response, however, differed from that in the earlier series of patients with primary demyelinating disease. The incidence of delayed responses was much lower, and the magnitude of the delays was smaller. Absent responses were particularly characteristic of patients with intracranial meningiomas. Tumours arising in the region of the sella turcica were associated with a high incidence of abnormalities of the waveform of the response, and asymmetry of the field of the occipital evoked potential was especially characteristic of this group. Most, but not all, asymmetric cases were associated with field defects.
Adult↗
Abnormalities of the pattern evoked potential in compression of the anterior visual pathways.
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Adult↗