Increased risk of sensory neuropathy in workers with chloracne after exposure to 2,3,7,8-polychlorinated dioxins and furans

OBJECTIVE: The existence of a peripheral neuropathy after exposure to polychlorinated dioxins (PCDD) is still discussed, as studies concerning dioxin effects on the peripheral nervous system are rare and contradictory. MATERIAL AND METHODS: Clinical and neurophysiological examinations (motor conduction velocity of the peroneal nerve, sensory conduction velocities of the sural and ulnar nerves) were made in 156 dioxin exposed workers (42 with, 114 without cloracne) from one pesticide producing plant. Because of known risk factors for peripheral neuropathy, 7 workers with and 28 without cloracne were excluded from further analysis. RESULTS: Workers with chloracne had a significantly higher exposure against PCDD as documented by back calculated lipid levels. They complained significantly more often of sexual impotence (28.6% compared to 5.8% of workers without chloracne, P<0.001), had significantly more frequent clinical signs of a sensory neuropathy (= abnormal sensory findings plus deep tendon reflex abnormalities) restricted to the legs (17.1% compared to 1.2%, P<0.001), had significantly more frequent > or =2 neurophysiologic abnormalities (34.3% compared to 14.0%, P<0.025), and had significantly lower mean amplitudes of the motor compound muscle potential of the peroneal nerve. CONCLUSION: PCDD has a mild toxic effect on the peripheral nervous system manifesting as mild sensory neuropathy of the legs in a minority of the most severely exposed persons.     

The value of brain stem auditory, visual and somatosensory evoked potentials and blink reflexes in the diagnosis of multiple sclerosis

Cervical and cortical somatosensory evoked potentials (SEP) following electrical stimulation of the median nerve and blink reflexes (BR) following electrical stimulation of the supraorbital nerve were recorded in 30 normal subjects aged 20–49 years. Subjects aged 40–49 had longer SEP latencies than subjects aged 20–39 years.
A total of 29 slightly affected patients with multiple sclerosis (MS) aged 26–49 years, including four patients without clinical signs (suspected MS) and 19 patients with signs indicating only one lesion (possible MS) were examined by low-rate random-stimulated brain stem auditory (BAEP), checkerboard pattern-reversal visual evoked potentials (VEP), SEP and BR. Abnormal recordings by at least one of the examinations were found in all but three patients, and by all four tests in five patients.
In patients with definite or probable MS, demonstration of clinically recognized or subclinical lesions was of minor diagnostic value, in contrast to the importance such findings had in patients with suspected or possible MS. Silent lesions were shown by at least one of the tests in the four suspected and in 13 of the possible MS patients, so these 17 patients could be transferred to a more certain diagnostic category. This reclassification was most often due to the BAEP recording.
In patients with spinal signs, the combination of BAEP and VEP recording was sufficiently efficient. In patients with optic neuritis a combination of BAEP and SEP was preferred. No abnormal recordings were found in 15 normal subjects examined by all four tests.     

Pontine lesions mimicking acute peripheral vestibulopathy

OBJECTIVES: Clinical signs of acute peripheral vestibulopathy (APV) were repeatedly reported with pontine lesions. The clinical relevance of such a mechanism is not known, as most studies were biased by patients with additional clinical signs ofbrainstem dysfunction. METHODS: Masseter reflex (MassR), blink reflex (BlinkR), brainstem auditory evoked potentials (BAEPs), and DC electro-oculography (EOG) were tested in 232 consecutive patients with clinical signs of unilateral APV. RESULTS: Forty five of the 232 patients (19.4%) had at least one electrophysiological abnormality suggesting pontine dysfunction mainly due to possible vertebrobasilar ischaemia (22 patients) and multiple sclerosis (eight patients). MassR abnormalities were seen in 24 patients, and EOG abnormalities of saccades and following eye movements occurred in 22 patients. Three patients had BlinkR-R1 abnormalities, and one had delayed BAEP waves IV and V. Clinical improvement was almost always (32 of 34 re-examined patients) associated with improvement or normalisation of at least one electrophysiological abnormality. Brain MRI was done in 25 of the 44 patients and confirmed pontine lesions in six (two infarcts, three inflammations, one tumour). CONCLUSIONS: Pontine dysfunction was suggested in 45 of 232 consecutive patients with clinical signs of APV on the basis of abnormal electrophysiological findings, and was mainly attributed to brainstem ischaemia and multiple sclerosis. The frequency of pontine lesions mimicking APV is underestimated if based on MRI established lesions only.     

Neurophysiologic assessment of mucopolysaccharidosis III.

OBJECTIVE: To describe finding of various neurophysiologic tests in patients with mucopolysaccharidosis III (MPS III) early in the disease course. METHODS: Patients were evaluated with flash visual evoked potentials (VEP), brainstem auditory evoked potentials (BAEP), electroencephalography (EEG), and nerve conduction studies (NCS) before they underwent hematopoietic stem cell transplantation (HSCT). RESULTS: Thirteen children underwent at least one neurophysiologic test before HSCT. The mean age at testing was 2.7 years. Ten of 11 (91%) patients had a normal flash VEP, and all 9 who had BAEP had normal central conduction. EEG was normal in 7/13 (54%), with the others showing diffuse slowing. NCS was normal in 10/11 (91%) patients. CONCLUSIONS: Despite extensive central nervous system involvement in MPS III, flash VEP and BAEP are almost always normal. EEG is often abnormal early in the disease. SIGNIFICANCE: This is the first report of neurophysiologic tests in a large series of MPS III patients.     

A case of alpha coma in acute brainstem dysfunction--consecutive electroencephalograms and evoked potentials

A 31-year-old woman was admitted because of severe headache and dysarthria in December 1985. Neurological examination on admission revealed severe impairment of consciousness, anisocoria, absent light reflex on the right side, and evidence of left hemiparesis, but other brainstem reflexes were intact. A CT scan taken shortly after arrival demonstrated a large hematoma in the right temporal lobe and the right cerebellum. Breathing became irregular and intubation was needed. An emergency operation was performed. After the operation the patient remained comatose without any spontaneous respiration or brainstem reflexes. The next day she was still comatose without any spontaneous movement and other neurological finding remained unchanged. An initial EEG obtained at this time showed an 8- to 9-Hz alpha rhythm of about 15-40 microV with preponderance over the posterior and central regions. Some spontaneous variability was noted. The same day, investigations of brainstem auditory evoked potential (BAEP), visual evoked potential (VEP), and somatosensory evoked potential (SEP) were performed. BAEP showed only the first, second and third waves (I-III) bilaterally. VEP was able to elicit the primary response (II-III) without the secondary response. SEP could not be obtained from the early cortical response to left median nerve stimulation, but showed N14 bilaterally and small N20 upon right median nerve stimulation. On the second day of hospitalization, a repeated EEG showed generalized slowing with loss of alpha frequency rhythms and it proved impossible for SEP to elicit N20 bilaterally. At this time, BAEP showed bilateral I-IIIth waves and VEP still showed primary response.(ABSTRACT TRUNCATED AT 250 WORDS)     

Multimodal evoked potentials in neuro-Behçet: a longitudinal study of two cases

Two neuro-Behçet patients have been studied, over a period of several months, by means of peroneal and median somatosensory- (SEP), brainstem auditory- (BAEP), and visual- (VEP) evoked potentials. In both patients, peroneal SEP showed evidence of a pathological reduction in the central conduction velocity without a related deep sensation impairment, while VEP changes were consistent with the visual disorders. Conversely, BAEP and median SEP findings did not show disease-related abnormalities. The observed anomalies were detectable irrespective of the clinical phase of the disease. Thus, evoked potential assessment is useful in providing objective evidence for evaluating and monitoring CNS damage in neuro-Behçet's syndrome.     

Visual involvement in Friedreich's ataxia: PERG and VEP study

Neuro-ophthalmological assessment, including red-free light retinography, in conjunction with simultaneous visual evoked potential (VEP) and pattern electroretinogram (PERG) recordings were performed in 10 Friedreich's ataxia patients: 9 patients showed marked VEP abnormalities. Moderate PERG amplitude reduction, with normal latencies, was related to mild and scattered fiber loss revealed by red-free light retinography. The initial part of the visual pathways does not seem to be the main site of electrophysiological abnormalities as demonstrated by the greater extent and relative independence of VEP versus PERG alterations. Primary axonal degeneration of the optic nerve and tracts cannot account for all features of VEP abnormalities, thus implying some dysfunction in succeeding visual structures as well.     

Evoked potentials

ABSTRACT- A survey is given of my studies of evoked potentials in patients with multiple sclerosis (MS) and in control subjects. Potentials were recorded following random low-rate auditory stimulation (BAEP), checkerboard pattern-reversal stimulation (VEP), somatosensory stimulation (SEP); blink reflexes (BR) were recorded following electrical stimulation of the supraorbital nerve. Normal data had to be related to age and sex in evaluating BAEPs and VEPs.
In 160 MS patients, a total of 421 recordings were obtained. Changes by repeated BAEP and VEP tests might reflect changes in the clinical state, but they also did occur in clinically stable patients. In patients with definite MS, high incidences of abnormality were shown, supporting the clinical findings. The diagnostic value was greatest when clinically silent lesions were demonstrated in patients with suspected or possible MS. In these patients, either BAEP or VEP gave evidence of subclinical lesions in about 50%, and when combined, in 71% of the patients, thus making a transfer to a more certain diagnostic classification possible and invasive examinations unnecessary. When SEP and BR tests were added, subclinical lesions were found in 74% of the patients. The SEP recordings did show a high incidence of abnormality, but only few silent lesions; the BR test was the least sensitive. The VEP was abnormal in all patients with signs of optic neuritis and in all but one with a history of optic neuritis.
The present results are compared to those obtained in other laboratories and with other types of examinations in MS patients. It is concluded that although the tests are not specific for MS, they give valuable information in the majority of patients with a clinically uncertain diagnosis. This information will most often not be given by other types of examination. The combination of VEP and BAEP is recommended, but it should be supplemented by SEP recording in patients without spinal signs.     

Neurophysiological and neuro-otological study of homozygous beta-thalassemia under long-term desferrioxamine (DFO) treatment

This report presents data on visual evoked potentials (VEPs) and brainstem auditory evoked potentials (BAEPs), as well as neurologic, ophthalmologic and otologic assessments performed on 120 patients with beta-thalassemia major undergoing long-term DFO treatment. A total of 32 patients showed abnormal VEPs and 14 abnormal BAEPs; seven had both VEP and BAEP abnormalities; 12 had sensorineural hearing loss (SNHL); 18 had conductive hearing loss, while 14 showed a combination of SNHL and conductive hearing loss. After DFO administration was modified (taking in consideration the serum ferritin levels) patients with abnormal findings were retested. The values of 15 patients of 23 who underwent VEP examinations had been normalized. Eleven of 15 who repeated the BAEP test had also gained normal values. The audiogram had not returned to normal in any patient with SNHL. In a second repetition of the examinations, no change was observed. It is concluded that in a great percentage of thalassemics at least one of the above examinations shows abnormal values. These abnormalities are mostly reversible, and probably reflect a dysfunction of the visual or auditory system, due either to DFO neurotoxicity or to iron overload or both.     

Adrenoleukodystrophy in the child and adrenomyeloneuropathy. Study of 2 families

Ten subjects from 2 families with adrenoleukodystrophy (ALD) and adrenomyeloneuropathy (AMN), hereditary X-linked diseases, were systematically explored. We performed endocrinological, biochemical assays and neurophysiological tests; the latter consisted of nerve conductions (CNV), Hoffmann's reflex and multimodal evoked potentials: visual (flash and pattern, VEP), brainstem auditory (BAEP) and somesthetic (SEP) using median nerve stimulation at the wrist. We only considered values above 2 SD. The purpose of our study was to determine the correlation between neurophysiological and endocrinological perturbations and the presence of pathological traits. Our results suggest that the correlation is high in diseased male patients, lower for the ALD carriers (BAEP, SEP and CNV were more frequently abnormal) and very low for the AMN carriers. Only the biochemical assays appeared to have any value for the characterization of female carriers of ALD and AMN.     

Visual and auditory evoked potentials during long-term vigabatrin treatment in children and adolescents with epilepsy.

OBJECTIVES: The aim of the study was to estimate the effects of Vigabatrin (VGB) as add-on therapy on visual (VEP) and brain-stem (BAEP) evoked potentials. METHOD: The investigation covered 100 epileptic patients from 8 to 18 years of age. The treatment included therapy with carbamazepine (CBZ) or valproate acid (VPA) using slow release formulations of these AEDs. Combination therapy was administered using add-on VGB in the recommended dose 57.4+/-26.5 mg/kg body mass/day. VEP and BAEP evoked potentials were recorded by means of Multiliner (Toennies, Germany). The obtained values were compared with age matched control group. RESULTS: Compared to control groups, significant differences in epileptic groups emerged in latencies of the peak III, V along with the interpeak intervals I-III of BAEP. Also VEP studies showed the reduction of N75/P100 and P100/N145 amplitudes. CONCLUSIONS: Adding VGB did not significantly increase the percentage of pathological abnormalities observed from EPs. Our electrophysiological studies demonstrate abnormalities in EPs parameters due to subclinical toxicity induced by AEDs. Major alterations produced bitherapy of VPA-SR + VGB and minor SR formulations of CBZ or VPA.     

Visual, early auditory and somatosensory evoked potentials in multiple sclerosis (917 cases)

Visual (VEP), brainstem auditory (BAEP) and somatosensory (SEP) evoked potentials were recorded over a 6 year period in 917 patients with or suspected of multiple sclerosis according to Mc Alpine's criteria. Evoked potentials provided information of diagnostic relevance in detecting clinically unsuspected lesions (spatial dissemination). They also gave valuable informations in patients with atypical or borderline clinical features. When abnormal, VEP indicated clinically silent lesions in 45.1 p. 100 of patients with definite MS, 66 p. 100 of those with probable MS and 78 p. 100 of the possible MS. Less than 15 p. 100 of SEP and/or BAEP abnormalities were found in 83 patients with a simple or recurring retrobulbar optic neuritis. Thirteen patients with acute transverse myelopathy and no prior history of neurological disease were studied. All had normal visual and brainstem auditory evoked potentials. Abnormal VEPs helped to the clinical assessment of 88 patients with progressive spastic paraparesis 46,6 p. 100 of whom had abnormal VEPs demonstrating disseminated lesions and 36,1 p. 100 had abnormal BAEPs. The frequency of the various types of VEP, BAEP and SEP abnormalities was studied as well as their course on repeated recordings. Results of multivariate analysis are given. It was found that the longer the time interval between the first MS relapse and the evoked potential recording, the higher the incidence of abnormalities. The incidence of evoked potentials abnormalities was lower in patients with normal CSF and higher in patients with inflammatory CSF. The abnormalities were more frequent when patients had clinical evidence of lesions of the sensory pathways explored by the tests.     

Electrophysiological study in patients with chronic hepatic insufficiency

Twenty patients affected by chronic hepatic insufficiency were studied by means of combined EEG, VEP and BAEP recordings. Subjects were classified, according to Parsons-Smith criteria, in grade 0 (without any clinical sign) and grade I (with minimal mental disturbances). In group 0 patients an elevated incidence of VEP alterations (40%) was observed, while EEG and BAEP recordings were less frequently (10%) abnormal. In group I patients a high degree of EEG (60%), VEP (70%) and BAEP (70%) abnormalities was found. Mean latency and interpeak interval values in group I patients were significantly prolonged if compared with the grade 0 and control groups. No correlations were found between electrophysiological data and blood biochemical parameters examined (ammoniemia, aminoacidemic pattern).     

Early electrophysiological findings in acute inflammatory demyelinating polyradiculoneuropathy variant of Guillain‐Barre syndrome in the Pakistani population – a comparison with global data

Acute inflammatory demyelinating polyradiculoneuropathy (AIDP) and acute motor axonal neuropathy are the most common variants of Guillian‐Barre syndrome documented in the Asian population. However, the variability of early neurophysiologic findings in the Asian population compared to western data has not been documented. Eighty‐seven cases of AIDP were retrospectively reviewed for their demographic, clinical, electrophysiological, and laboratory data. Mean age of subjects was 31 ± 8 years with males more commonly affected. Motor symptoms (97%) at presentation predominated. Common early nerve conduction findings included low motor amplitudes (85%), recordable sural sensory responses (85%), and absent H‐reflex responses (65%). Prolonged F‐latencies were found most commonly in posterior tibial nerves (23%) in the lower limbs and median and ulnar nerves (18%) in the upper limbs. Blink reflex (BR) studies were performed in 57 patients and were abnormal in 80% of those with clinical facial weakness and in 17 of 52 patients (33%) with no clinical cranial nerve signs, suggesting subclinical cranial nerve involvement. Abnormal motor and sensory amplitudes are seen early. Prolonged distal latencies, temporal dispersion/conduction blocks and sural sparing pattern are other common early nerve conduction study findings of AIDP seen in the Pakistani population. There are no significant differences in abnormalities of conduction velocities and delayed reflex responses compared to published data. The BR can help in the early diagnosis of AIDP.     

Visual and auditory evoked potentials in the early diagnosis and follow-up of neurosarcoidosis

Visual and brainstem auditory evoked potentials (VEPs, BAEPs) were recorded in 23 patients with neurosarcoidosis. Eight patients (35%) had abnormal BAEPs, and 10 (43%) had abnormal VEPs. Four of the 8 patients with abnormal BAEPs had facial paresis, one had impaired memory and only 3 had symptoms and signs compatible with brainstem lesion. Seven of the patients with abnormal VEPs had no visual symptoms. These findings suggest that BAEP and VEP can reveal subclinical nervous system involvement in sarcoidosis and can also help in the early diagnosis of neurosarcoidosis. Successive recordings of 5 patients showed that BAEP and VEP were useful in the follow-up of these patients.     

Brain stem auditory and visual evoked potentials in multiple sclerosis

The diagnostic value of the checkerboard pattern-reversal visual evoked potential (VEP) and the random, low rate stimulated brain stem auditory evoked potential (BAEP) was compared in 99 patients with established or suspected multiple sclerosis (MS). In normal subjects examined by both techniques no abnormal recordings were found. In 49 patients with definite MS an incidence of abnormality was found in 100% of VEP and in 84% of BAEP recordings. In 50 patients with probable or possible MS an abnormal VEP was found in 70% and an abnormal BAEP in 50%. When the two examinations were combined, the diagnostic yield increased to 100 and 80%, respectively. 22 patients had only spinal symptoms; in these the VEP gave 73%, the BAEP 55% and the combination 82% abnormalities. The combination of the two techniques was found useful for demonstrating demyelinating lesions in the central nervous system, the diagnostic value being greatest when these lesions were clinically silent.     

The 20/20 eye in multiple sclerosis

Using clinical and electrophysiologic measures, we evaluated the visual pathway of patients who had multiple sclerosis, 20/20 Snellen acuity, and no history of optic neuritis. Delayed latencies were found in the transient visual evoked potentials (VEPs) of 38% of the patients, and interocular latency differences were abnormal in 67%. Contrast VEPs were abnormal in 46%. Psychophysical determinations of contrast sensitivity were abnormal in 78%. Only 17% of the patients had dyschromatopsia, 36% had afferent pupillary abnormalities, and 59% had optic nerve pallor or nerve fiber layer loss. Psychophysical contrast evaluations and VEP studies were superior to other clinical evaluations in demonstrating visual dysfunction in these patients.     

Bimodal evoked potentials during long-term therapy with conventional or slow release preparations of carbamazepine and valproic acid in children and adolescents with epilepsy

The measurement of evoked potentials (EPs) may be particularly useful in clinical neuropharmacology for investigation of drug effects of afferent nerve conduction within CNS. The study aims at estimating the long term effects of conventional or slow release formulation (CR) of carbamazepine (CBZ) and valproid acid (VPA) on visual (VPA) and brainstem auditory (BAEP) evoked potentials. Investigation covered 125 patients 8 to 18 years old to whom both formulations of CBZ or VPA were administered in monotherapy. Everyone received a drug dosage which gave an adequate therapeutic plasma concentration and satisfactory seizure control. Antiepileptic drugs (AEDs) plasma levels were measured by means of fluorescence polarization immunoassay method aided of TDx Analyzer (Abbott, Diagnostic). EPs were registered by means of Multiliner (Toennies, Germany). A pattern of reversal stimulation for VEP was used. The latencies of N75, P100, N145 as well as interpeak amplitudes of N75/P100, P100/N145 were evaluated. The following BAEP parameters were considered: morphology of the potential, absolute latencies of waves I, III, V and I-III, III-V, I-V. EP were always performed in the same conditions and with the same equipment for the epileptic and control groups. The obtained values were compared with age-matched control group. The following BAEP abnormalities were observed: prolonged absolute latencies of waves I, III, V as well as prolonged IPLs I-III. The BAEP V/I amplitude ratio and morphology of the waves were normal in all patients. The VEPs abnormalities manifested as prolongation of P100 or N145 latencies and reduction of amplitudes N75/P100, P100/N145. Results of these electrophysiological studies with CBZ and VPA demonstrate that EP are sensitive, noninvasive reflectors of AEDs effects within the CNS.     

Electrophysiological studies of the visual system in myotonic dystrophy

Ocular signs and electroretinal alterations frequently occur in Myotonic Dystrophy (MD). Surprisingly few reports describe VEP abnormalities for this syndrome. Since the evaluation of cortical visual responses is linked to an understanding of preceding retinal changes, we conducted a systematic study of the visual system including ophthalmological and electrophysiological (EOG, ERG, PERG, VEP) investigation in 14 confirmed myotonic patients. The various tests revealed consistent abnormalities, the most frequent of these being PERG and VEP changes. These alterations seemed to occur independently of one another, suggesting impaired function at different levels of visual pathway. A generalized defect of cell membrane has recently been proposed as etiopathogenesis of typical EMG and systemic features of the disease. Such membrane dysfunction might account for the early and marked abnormalities in electrophysiological tests, even in the absence of neuro-ophthalmological changes.