Multimodality evoked potentials in myotonic dystrophy

Multimodality evoked potentials were performed in 18 patients affected by myotonic dystrophy (8 males and 10 females); the aim was to make an electrophysiological evaluation of the central nervous system involvement in this disease. We observed brainstem, somatosensory and visual evoked potential abnormalities respectively in 53%, 62.5% and 71.4% of cases, with no apparent relationship to the severity of the disease. Our abnormal findings provide further confirmation of CNS involvement in myotonic dystrophy and occur in various combinations suggesting an aspecific involvement at different levels, reflecting the multisystemic character of this disease.

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Sommario I potenziali evocati multimodali sono stati effettuati in 18 pazienti (8 maschi e 10 femmine), affetti da distrofia miotonica. Lo scopo era di effettuare una valutazione elettrofisiologica dell'interessamento del sistema nervoso centrale in questa malattia. I potenziali evocati del tronco, somatosensitivi e visivi sono risultati abnormi rispettivamente nel 53%, 62.5% e 71.4% dei casi, senza apparente relazione con la gravità della malattia. I risultati da noi ottenuti forniscono un'ulteriore conferma dell'interessamento del SNC nella distrofia miotonica che è possibile in varie combinazioni, suggerendo un aspecifico interessamento a diversi livelli, che riflette il carattere multisistemico della malattia.

     

Multimodal evoked potentials in progressive external ophthalmoplegia with mitochondrial myopathy

Multimodal evoked potentials were studied in 13 patients affected by progressive external ophthalmoplegia with histologically proven mitochondrial myopathy. Progressive external ophthalmoplegia occurred with craniosomatic spreading in all the patients and with a varying degree of nervous and/or other system involvement in most of them. In all but one of the subjects, at least one evoked potential modality was abnormal; 11 of them demonstrated an abnormal visual evoked potential, but this finding might have been influenced by concurrent retinal dysfunction. Abnormalities in brainstem auditory evoked potentials and/or somatosensory evoked potentials, revealing an impairment of central sensory pathways, were detected in 7 subjects, 5 of whom lacked clinical evidence of central nervous system involvement. Thus, evoked potentials represent an useful tool for the detection of subclinical central nervous system involvement in patients affected by progressive external ophthalmoplegia with mitochondrial myopathy.     

Visually evoked potentials in boys with developmental dyslexia

Pattern reversal visually evoked potentials were examined in a group of 16 boys with developmental dyslexia and 17 controls matched for sex, age and intelligence. Delineation of hypothesis was done with an independent pilot study. Wave form differences between groups could be observed over the left central lead in the pilot and replication study. Only 44% of the dyslexies showed a negative component between 110 and 215 ms after stimulus onset in comparison to more than 80% of the controls. The lack of this component was most prominent in dyslexies whose spelling scores were more than 1.5 standard deviations below their intelligence score.

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Zusammenfassung Durch Musterumkehrreize evozierte Potentiale wurden bei 16 Jungen mit umschriebener Lese-Rechtschreibschwäche und 17 nach Alter, Geschlecht und Intelligenz parallelisierten Kontrollkindern untersucht. Die Ableitung der Hypothesen erfolgte durch eine unabhängige Pilot-studie. Die Gruppen unterschieden sich in der Form des evozierten Potentials über der linken Zentralregion (C3). Während bei über 80% der Kontrollkinder eine negative Komponente zwischen 110 und 215 ms nach Stimulus auftrat, konnte diese Komponente nur bei 44% der umschrieben lese-rechtschreibschwachen Kinder nachgewiesen werden. Vor allem bei den leserechtschreibschwachen Kindern, deren Rechtschreibleistung mehr als 1,5 Standardabweichungen unterhalb ihres IQs lag, fehlte diese Komponente im evozierten Potential.

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Résumé On a examiné les potentiels visuels évoques dans un groupe de 16 garcons présentant une dyslexie développementale et dans un groupe de conrôle de 17 cas appariés selon le sexe, l'âge et l'intelligence. L'élaboration d'hypothèses a été faite sur une étude pilote indépendante. Des différences de formes des ondes entre les groupes ont été observées du côte gauche central dans l'études témoin. 44% des dyslexiques seulement montraient une composante négative entre 110 et 225 ms après le début du stimulus (N1) à comparere avec plus de 80% parmi les groupes contrôles. Le défaut de ces composantes était plus prédominant chez les dyslexiques dont les scores de lecture étaient plus d'1,5 déviation standard en dessous de leur score d'intelligence.

     

Visually evoked cortical potentials in renal failure: transient potentials.

Transient visually evoked cortical potentials (VECPs) were recorded from patients with renal disease. Changes in VECP latencies are described for undialyzed patients, patients receiving dialysis therapy, and patients who received kidney transplants. Characteristics of VECP latencies in these patient groups as well as examples of changes in latency values with respect to time for two individual patients are examined. The basic overall finding is that the VECP latencies increase as a patient's clinical condition deteriorates and normalize as the condition improves.     

Visually evoked potentials and electroretinography in neurologic evaluation.

Electrophysiologic testing of the visual system requires primarily the ERG and the VEP. The flash electroretinogram provides information about the outer retina only. The pattern electroretinogram is derived from both the outer retina and the innermost retinal layers including the ganglion cell layer. The VEP is based on electrical information recorded from the visual cortex in response to stimulation of the retina. Thus, the integrity of the entire visual pathway can be tested. Localizing ability of the VEP is limited. Since the visual cortex is heavily weighted by representation of the central retina, peripheral lesions, including those producing peripheral visual field abnormalities that do not impinge upon central fixation, may produce relatively little disturbance of the VEP. As with most tests, electrophysiologic studies of the visual system must be placed in context of the entire examination, including the patient's history and neurologic and especially neuro-ophthalmologic evaluation. Electrophysiologic testing has three main uses in neurology. Pattern-reversal VEPs may be useful in detecting hidden visual loss in multiple sclerosis; VEPs and ERGs can distinguish function from organic visual loss; and VEPs and ERGs can be useful in the diagnosis of visual loss in nonverbal patients, especially in children.     

Leukoencephalopathies in mitochondrial disorders: clinical and MRI findings

The second most frequently affected organ in mitochondrial disorders (MIDs) is the central nervous system (CNS). One of the most frequent CNS abnormalities on imaging is the affection of the white matter (WMLs) for which the term, leukoencephalopathies in mitochondrial disorders (LEM), is proposed. The morphology of LEM on imaging is quite variable even within the same type of MID and the same family. LEM can be a subtle or prominent feature on imaging and may go along with or without clinical neurologic or neuropsychological manifestations. WMLs are most likely due to the underlying metabolic defect of the respiratory chain or concomitant oxidative stress, resulting in neuronal death and replacement of neurons by glial cells. WMLs in MIDs frequently give rise to misinterpretation, particularly if the mitochondrial defect is not evident in organs other than the CNS or if the presence of WMLs does not induce consideration of a MID as a differential. The diagnosis of a LEM requires the diagnosis of an MID, the detection of WMLs on imaging, and the exclusion of all possible differentials. Because the presence of LEM has an impact on the prognosis of an MID, all MID patients should undergo cerebral imaging even in the absence of clinical CNS manifestations.     

Visual evoked potentials in diabetes mellitus

25 diabetic patients have been studied in order to investigate the possible effects of the disease on the central nervous system by means of pattern shift visual evoked potentials. Patients with diabetic retinopathy, glaucoma and cataract were excluded from the study. Results obtained from a control group of 30 normal subjects were compared to those of the patient group in which sural nerve conduction velocities have also been determined to see whether there is a correlation between peripheral and central involvement of the nervous system. In diabetic patients latency prolongation in the P100 and N140 components were observed. The N90-N140 interpeak latency was also prolonged. In addition, in patients with longstanding diabetes mellitus the incidence of VEP abnormalities was found to be high. Pathologic changes in VEP latencies did not show any correlation with sural nerve conduction abnormalities.     

Visual evoked potentials in acute occipital blindness

Summary Pattern-evoked and flash-evoked responses were recorded from four patients with acute blindness due to occipital ischaemia. No responses could be obtained with pattern stimulation. Flash stimulation, however, yielded well-reproducible potentials in all four cases in spite of practically complete visual loss. In one patient vision recovered completely while the three others showed poor or minimal recovery in restricted visual field areas only. It is concluded that the flash method is not appropriate for differentiation of occipital blindness from psychogenic visual disorders. Furthermore, preserved flashevoked potentials in the acute stage of occipital blindness cannot be taken as a reliable prognostic sign for visual recovery, as has been postulated by others. A possible extrastriate origin of these flash responses is discussed in view of recent theories on a second visual system.Presented in part at the conference of the German Neurological Society in Munich (15–17 October 1981)     

Simultaneously evoked primary and cognitive visual evoked potentials distinguish younger and older patients with Parkinson's disease

Summary While it is known that both primary visual processes and visuocognitive responses are affected in Parkinson's Disease (PD), their relationship is not known. It is known that both of these measures can be affected by age per se. Our aims were to determine if in non-demented PD patients visual cognitive event-related potential (ERP) changes simply reflect abnormal primary visual processing and to determine the effects of age and disease on their relationship. In order to do so, we introduce a new normalizing procedure for visual ERPs. In addition to the latencies and amplitudes of P100, N140, P200, N200 and P300 components, the P300-P100 latency difference (termed central processing time —CPT) were measured. In order to avoid confounding factors of absolute amplitude differences due to say, generally low voltage recordings or poor primary visual responses, P300 responses normalized to P100 responses were also evaluated (P300/P100 amplitude ratio). Visual ERPs were obtained in an oddball paradigm in 20 non-demented patients with PD and 20 normal age-matched subjects. The stimuli were horizontal sinusoidal gratings differing only in spatial frequency (0.5 and 1 cycle/degree). While simple ERP latency criteria did not distinguish non-demented PD patients as a group from controls, when younger PD patients were compared to older PD patients and controls CPT acceleratedly increased in younger PD patients. The amplitudes of both N200 and P300 provided significant distinction between patient and control groups. The surprising result emerging from this study is that an individually normalized P300 amplitude provides significant distinction of younger PD patients from age matched normals.     

脑干三叉神经诱发电位的电生理学特征

目的研究脑干三叉神经诱发电位（BTEP）的波形特征。方法选择全麻开颅手术非三叉神经痛病人20例,采用针形电极刺激其三叉神经周围支,在头顶记录BTEP波形,统计潜伏期、波幅和波间期。结果本组均可记录到W1、W2、W3三个波形,其中W1为高幅三相波,W2、W3为单相负波。在一定范围内,随着刺激强度增大,W1、W2、W3波幅增大而潜伏期不变。结论采用针形电极刺激能获得满意的BTEP波形,为进一步研究三叉神经痛病人在微血管减压术前后BTEP的变化提供依据。     

Visually evoked potentials from occipital and precentral cortex in visually deprived humans.

The visually evoked potential (VEP) was recorded from the scalp overlying precentral and occipital cortex in three monocularly deprived humans. The subjects had defects of the globe from birth that effectively created a condition of diffuse light rearing in one eye. In subject, BER, a 19-year-old with a recently removed congenital cataract, the occipital response evoked from the deprived eye was reduced by 53% compared with the response evoked from the good eye. In subject GUZ, age 20 with a congenital cataract, the occipital response evoked from the deprived eye was actually larger by 20% than was the response evoked from the good eye. For UTZ, age 5 with whitish cellular debri in the anterior vitreous of the eye, the occipital response evoked from the deprived eye was only 4% smaller than the response evoked from his good eye. In all three subjects, the precentral response evoked from the deprived eye was reduced in amplitude compared with the precentral response evoked from the good eye. In terms of relative effect of the deprivation upon the VEP from the two recording sites, the precentral VEP was altered to a greater extent than was the occipital VEP. These findings indicate that diffuse light rearing can affect the pathways projecting to precentral cortex independently of the specific visual pathways.     

Visual evoked potentials in ataxia telangiectasia

Summary Pattern reversal visual evoked potentials (VEPs) elicited in four patients with ataxia telangiectasia revealed normal results in two and absent responses in two. The pathogenesis of the VEP abnormalities is discussed. It is surmised that the VEP changes reflect progressive degeneration of the nerve fibres in the anterior visual pathway, as in Friedreich's ataxia.     

Clinical applications of evoked potentials in neurological disorders

The functional integrity of the main sensorial systems and of the central motor pathways can be evaluated through multimodal evoked potentials and non-invasive transcranial stimulation of the motor cortex. In this review the authors summarize the main clinical indications of the afore said methods specifically in the field of the neurological disorders.     

Visual evoked potentials in cerebral white matter hyperintensity on MRI

OBJECTIVES: To investigate the correlation of the cerebral white matter hyperintensities (WMH) on MRI, and latency and amplitude of visual evoked potentials (VEPs) in elderly subjects. PATIENTS AND METHODS: Pattern VEP (PVEP) and flash VEP (FVEP) were recorded in 25 patients with WMH consisting of 12 patients with frontal dominant WMH (FMH) and 13 patients with occipital dominant WMH (OMH) and 25 patients with basal ganglionic hyperintensities (BGH). RESULTS: In WMHs, there were significantly larger P100 and P2 amplitudes than in BGHs and controls. Regarding the distribution of WMH, OMH showed significantly larger P100 amplitudes than FMH. In OMH in males, there was significantly prolonged P100 latency compared with females, and in females, there were significantly larger P100 and P2 amplitudes compared with males. CONCLUSION: Appropriate clinical values in VEP should take into consideration WMH in addition to gender and age-related changes.     

Brainstem auditory evoked potentials in tuberous sclerosis

Brainstem auditory evoked potentials were recorded in 4 subjects and pattern reversal evoked potentials in 1 subject, all with tuberous sclerosis. Alterations were found (absence or delay of components and prolonged interpeak intervals) which may suggest impaired nervous conduction also at brainstem level in patients with tuberous sclerosis.

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Sommario Sono stati registrati i potenziali evocati auditivi troncoencefalici in 4 soggetti con sclerosi tuberosa, in uno di essi sono stati registrati anche i potenziali evocati visivi da pattern reversal. Sono state ritrovate alterazioni delle risposte (assenza o ritardo di alcune componenti ed intervalli interpicco prolungati) che possono suggerire l'esistenza di una conduzione nervosa alterata anche a livello del tronco dell'encefalo nei pazienti con sclerosi tuberosa.

     

Cognitive dysfunction in mitochondrial disorders

Among the various central nervous system (CNS) manifestations of mitochondrial disorders (MIDs), cognitive impairment is increasingly recognized and diagnosed (mitochondrial cognitive dysfunction). Aim of the review was to summarize recent findings concerning the aetiology, pathogenesis, diagnosis and treatment of cognitive decline in MIDs. Among syndromic MIDs due to mitochondrial DNA (mtDNA) mutations, cognitive impairment occurs in patients with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes syndrome, myoclonus epilepsy with ragged-red fibres syndrome, mitochondrial chronic progressive external ophthalmoplegia, Kearns-Sayre syndrome, neuropathy, ataxia and retinitis pigmentosa syndrome and maternally inherited diabetes and deafness. Among syndromic MIDs due to nuclear DNA (nDNA) mutations, cognitive decline has been reported in myo-neuro-gastro-intestinal encephalopathy, mitochondrial recessive ataxia syndrome, spinocerebellar ataxia with encephalopathy, Mohr-Tranebjaerg syndrome, leuko-encephalopathy; brain and spinal cord involvement and lactic acidosis, CMT2, Wolfram syndrome, Wolf-Hirschhorn syndrome and Leigh syndrome. In addition to syndromic MIDs, a large number of non-syndromic MIDs due to mtDNA as well as nDNA mutations have been reported, which present with cognitive impairment as the sole or one among several other CNS manifestations of a MID. Delineation of mitochondrial cognitive impairment from other types of cognitive impairment is essential to guide the optimal management of these patients. Treatment of mitochondrial cognitive impairment is largely limited to symptomatic and supportive measures. Cognitive impairment may be a CNS manifestation of syndromic as well as non-syndromic MIDs. Correct diagnosis of mitochondrial cognitive impairment is a prerequisite for the optimal management of these patients.     

Cervical vestibular evoked myogenic potentials in primary headache disorders

ObjectiveTo determine if cervical vestibular evoked myogenic potentials (cVEMPS) differ in patients with migraine without aura (MoA), vestibular migraine (VM) and tension type headache (TTH).MethodsTwenty patients with MoA, 24 patients with VM and 20 patients with TTH were included in the study. Thirty healthy volunteers of comparable age and gender were taken as the control group. The latencies of peaks p13 and n23, peak-to-peak amplitude of p13–n23 divided by a mean prestimulus EMG recorded during cVEMP testing were measured. The amplitude asymmetry between right and left sides was also calculated and taken into consideration. Caloric testing was conducted to check if the results are associated with the results of the cVEMPs.ResultsFive (one on the right, four on the left side) of the 24 patients with VM (20.8%) displayed a unilateral caloric hypofunction. Normal results were recorded from patients with MoA and TTH. p13, n23 latencies and amplitudes of the patient groups were not statistically different from the results of the healthy controls (p > 0.05). An amplitude asymmetry between right and left sides exceeding that of the healthy controls was not also present (p > 0.05).ConclusionsThough a hypofunctioning horizontal semicircular canal was detected in 20.8% of the patients with VM, saccular function seemed to be unaffected. Patients with MoA and TTH did not display any vestibular test abnormality.SignificancePrimary headache disorders seem to be associated with a normal interictal cVEMP profile.