Alma Patrizia Tormene

Visual evoked potentials standard (2004)

IntroductionThisdocumentpresentsthecurrent(2004)standardfor the visual evoked potential (VEP). The VEPisanevokedelectrophysiologicalpotentialthatcanbeextracted,usingsignalaveraging,fromtheelectro-encephalographicactivityrecordedatthescalp.TheVEPcanprovideimportantdiagnosticinformationregardingthefunctionalintegrityofthevisualsystem.The current standard presents basic responseselicited by three commonly used stimulus condi-tionsusingasingle,midlinerecordingchannelwithanoccipital,activeelectrode.Becausechiasmalandretrochiasmaldiseasesmaybemissedusingasinglechannel,threechannelsusingthemidlineandtwolateralactiveelectrodesaresuggestedwhenonegoesbeyondthestandardandtestspatientsforchiasmalandretrochiasmaldysfunction.Patternreversalisthepreferredtechniqueformostclinical purposes. The results of pattern reversalstimuli are less variable in waveform and timingthantheresultselicitedbyotherstimuli.Thepatternonset/offsettechniquecanbeusefulinthedetectionofmalingeringandinpatientswithnystagmus,andtheflashVEPisparticularlyusefulwhenopticalfactorsorpoorcooperationmaketheuseofpatternstimu-lationinappropriate.Theintentofthisstandardisthat

Ocular manifestations in the mucopolysaccharidoses – a review

Ocular manifestations are very common in all types of mucopolysaccharidoses (MPS) and often lead to visual impairment. They arise as a result of the accumulation of glycosaminoglycans deposits in ocular tissues or secondary to increased intracranial pressure. Typical ocular features in MPS include corneal clouding, retinopathy, glaucoma, optic disc swelling, optic atrophy, and ocular motility and refractive error problems. This paper reviews the ocular features in patients with MPS, discusses the diagnosis of these ocular features and the diagnostic problems that may arise in patients (children) with MPS, and highlights the central role ophthalmologists may play in the diagnosis and follow‐up of these patients.

Ataxia and Congenital Muscular Dystrophy: the follow-up of a new specific phenotype

Cerebellar hypoplasia may, at neuroimaging studies, be found in association with congenital muscular dystrophy (CMD), although it is an extremely rare occurrence. We here report on three CMD patients who underwent a longitudinal evaluation of clinical and neuroimaging features for a mean period of 18 years. Case 1, a 22-year-old woman, and cases 2 and 3, brothers aged 26 and 20 years, respectively, had presented a mild to moderate muscular weakness and increased serum creatine kinase (CK) levels since birth. All cases were diagnosed in the first years of life, with identification of evident dystrophic changes at muscle biopsy and moderate to severe cerebellar hypoplasia at brain computed tomography (CT) scan. Subsequently, all the patients underwent a second muscle biopsy, with immunostaining and immunoblot analysis, which showed normal values for merosin, dystrophin and dystrophin-related proteins. During the longitudinal study, the patients underwent repeated neurological and psychiatric examinations, serum CK controls, intellectual ability assessments and neuroimaging evaluations (CT and/or magnetic resonance imaging (MRI)). In all cases, these investigations indicated a mild to moderate deficit in the proximal muscles and a clear-cut cerebellar syndrome which, it was assumed, had been present since the first years. The patients also presented some intellectual difficulties, with an IQ of 0.69 in case 1, 0.83 in case 2 and 0.61 in case 3. The clinical course of all the patients was static, and all symptoms of the combined muscle and brain involvement persisted. Nor were any changes in the cerebellar hypoplasia observed at repeat MRIs. Findings obtained by us on the longitudinal study and a review of the literature indicate that cerebellar hypoplasia and merosin-positive CMD constitute a particular clinical phenotype, mainly characterized by an ataxic syndrome associated with a non-severe muscular involvement and a possible mild intellectual impairment.

Electroretinogram and visual-evoked potentials in children with optic nerve coloboma.

The aim was to evaluate alterations in Visual-Evoked Potentials (VEP) and Electroretinogram (ERG) and discover whether these tests are useful for determining residual visual acuity in cases where a patient is unable to collaborate. Flash and, when possible, Transient Pattern Reversal Visual-Evoked Potentials and Maximal Response ERG were recorded in 8 children (under three years old) affected by different aspects of optic nerve coloboma. None of them had visual acuity evaluated because of poor collaboration. All examinations were carried out using skin electrodes. Amplitude of the a and b component of ERG, amplitude, morphology and latency of the major components of Flash VEP and amplitude and latency of P100 Pattern Reversal VEP were evaluated. Four of the patients were examined three years later and visual acuity was compared with the previous electrofunctional results. Alterations in ERG were found only in the case of significant retinal anomalies (great coloboma, retinal detachment), huge alterations were found in both Flash VEP and in Pattern Reversal VEP. The retrospective study of VEP traces and visual acuity showed a good correlation between electrofunctional data and visual capability. Electrofucntional examinations can identify important conductive retinocortical anomalies. The possibility of correlating electrophysiological results with residual visual acuity is important for rehabilitative management in such optic disc malformations.

The Role of Visual Electrophysiology in Mucopolysaccharidoses

Visual electrophysiological techniques represent excellent means for assessing retinal, optic pathways and visual cortex function. Electroretinograms, visual evoked potentials, and clinical records of 17 patients with mucopolysaccharidosis registered in the neurophysiological database of our institution were reviewed retrospectively. Ten patients were on enzyme replacement therapy, 2 underwent bone marrow transplantation, one also keratoplasty. Changes in the electroretinogram pointed to the diagnosis of retinal dystrophy type rod-cone in 8 patients. In patients in whom severe corneal clouding precluded fundus oculi inspection and at an early stage before typical fundus appearance diagnosis was possible only using the electroretinogram. Visual evoked potentials were useful to confirm the loss of visual function in patients difficult to test clinically. The authors suggest the use of electroretinogram and visual evoked potentials primarily as research tools to describe the natural history and ophthalmologic outcome in mucopolysaccharidoses, although they may have clinical utility in very selected cases.

ISCEV guide to visual electrodiagnostic procedures

Clinical electrophysiological testing of the visual system incorporates a range of noninvasive tests and provides an objective indication of function relating to different locations and cell types within the visual system. This document developed by the International Society for Clinical Electrophysiology of Vision provides an introduction to standard visual electrodiagnostic procedures in widespread use including the full-field electroretinogram (ERG), the pattern electroretinogram (pattern ERG or PERG), the multifocal electroretinogram (multifocal ERG or mfERG), the electrooculogram (EOG) and the cortical-derived visual evoked potential (VEP). The guideline outlines the basic principles of testing. Common clinical presentations and symptoms are described with illustrative examples and suggested investigation strategies.

Correlation of ERG and pigment epithelium changes in external progressive ophthalmoplegia (EPO)

Six out of 17 patients with progressive external ophthalmoplegia (EPO) were found to have pigment anomalies with alterations in the electroretinographical (ERG) tracings. However, fluorangiography demonstrated alterations of the retinal pigment epithelium in patients with normal fundus and ERG examinations. We conclude that in our series there was no correlation between retinopathy and tapetoretinal degeneration.

Alterations of the retino-cortical conduction in patients affected by Classical Congenital Muscular Dystrophy (Cl-CMD) with merosin deficiency

Immunocytochemical analysis of the laminin alpha-2 (merosin) chain in the muscle of patients with Classic Congenital Muscular Dystrophy (Cl-CMD) differentiates the types of the disease associated with a merosin deficit from those that are merosin positive. Patients with Central Nervous System involvement in merosin negative Cl-CMD always present alterations of the white matter at RMI, but usually these are not clinically significant. While ocular malformations (microphthalmia, alterations of the anterior chamber, of the retina, or of the angle and cataract) and damage to the Central Nervous System are described in some subtypes of CMD (Muscle Eye Brain disease, Walker Warburg Syndrome), ocular involvement and retino-cortical conduction in merosin negative Cl-CMD are not well known. This study reports on four patients affected by merosin negative Cl-CMD. All these patients presented important alterations of the white matter associated with ventricular enlargement and, in one case, with pachygyria and micropolygyria. Refraction, visual acuity, ocular motility, anterior segment and fundus were examined. ERG Maximal, Cone and Rod response, VEP transient pattern reversal was carried out as well. Significant alterations at the standard ophthalmologic examination or of the electroretinogram responses were not registered while, in all cases, important modifications in retino cortical conduction (reduction in amplitude, increase in latency, reduction in amplitude on the lateral derivations) were observed, demonstrating involvement of the optic pathway at different levels during the course of this disease.

Opto-Chiasmatic Arachnoiditis in the Young

14 young patients, operated upon for opto-chiasmatic arachnoiditis by craniotomy are presented. 2 main etiopathogenetic forms (and their respective clinical equivalents) of the disease could be recognized. Only 1 postoperative death occurred, in a patient with a dominant clinical picture of intracranial hypertension. Results of surgery (craniotomy and lysis of adhesions) could be distinguished as positive (functional improvement) in 5 cases, indifferent or negative in the others, with a follow-up duration of up to 23 years. The role of the diagnostic value of the pneumoencephalogram as a basis for surgical indication is discussed: it is felt that this examination, when reported as negative, is not of sufficient value to rule out the diagnosis, which must essentially rely upon clinical data.

Long-term rearrangement of retinal structures in a novel mutation of X-linked retinoschisis

The aim of the present study was to report a novel mutation in the retinoschisin 1 (RS1) gene in a Caucasian family affected by X-linked juvenile retinoschisis (XLRS) and to describe the long-term modification of retinal structure. Two brothers with an early onset maculopathy were diagnosed with XLRS. Fundus photography, fluorescein angiography, spectral domain optical coherence tomography and electroretinogram analyses were performed. Their sister was also examined. All subjects were screened for mutations in the RS1 gene. XLRS patients demonstrated a marked reduction of best-corrected visual acuity. SD-OCT scans reported a cystic degeneration primarily involving the inner nuclear layer, though some cysts were detected in the outer plexiform layer and in the ganglion cell layer. During the ten-year follow-up, a progressive retinal thickening and coalescence of the cysts was observed. Genetic testing revealed a novel mutation (p.Ile212Asn) in the RS1 gene in both XLRS patients, whereas their sister was not a genetic carrier. Several mutations of the RS1 gene were recognized to be responsible for XLRS. Although the correspondence between genotype and phenotype is still under debate, is reasonable that siblings affected by XLRS could share other genetic and/or epigenetic factors capable to influence clinical course of the disease.