Cerebral evoked potentials in multiple sclerosis

Multimodal evoked potentials were analyzed from 58 possible, 62 probable and 100 definite (total 220) multiple sclerosis (MS) patients. Visual evoked potentials (VEP) were most frequently abnormal yielding 39%, 69%, 84% in the three diagnostic groups respectively. Median nerve sensory evoked potentials (SEP) yielded abnormalities in 26%, 65%, 79% respectively. Brainstem auditory evoked responses (BAER) were abnormal in 17%, 39%, 66% respectively. We measured the combined amplitude (CA) of waves III, IV, V in the BAER of these patients as an objective measure of amplitude asymmetry. The CA was considered abnormal if it was 1SD below the lowest CA value in the control group. The CA was abnormal in 9.2% of BAER with normal central conduction time. The BAER diagnostic yield in MS patients increased 11% by using CA analysis.     

Sensory evoked potentials in herpes simplex encephalitis.

Flash visual potentials (FEPs), somatosensory evoked potentials (SEPs) and auditory brainstem responses (ABR) were recorded in a 66-year-old patient presenting with clinical, EEG and CT brain scan features of herpes simplex encephalitis (HSE). At the time of evoked potential study (10 days after onset of the disease) the patient was treated with iv barbiturate on controlled respiration (lidocaine and phenytoin were not utilized); core temperature was 37 degrees C and pupils were dilated and nonreactive. Cortical FEPs were not recognizable on 02 lead, whereas they were clearly evident on 01 with normal latency of early N1, P1, N2 waves and delayed P2 component. SEPs showed normal peripheral and central conduction times, but N20 peak was bilaterally absent with unrecognizable (on P3) or delayed (on P4) N33 wave. No ABR (including wave I) were found on stimulation of the right ear, whereas delayed wave V with prolonged interpeak I-V latency was found on stimulation of the left ear. In conclusion, changes in sensory evoked potentials in HSE seem to be caused either by necrotic-hemorrhagic damage (with the disappearance of some cortical responses), by coma (with alterations in middle-latency cortical responses) and by increased intracranial pressure (with subsequent ABR abnormalities).     

Multimodality evoked potentials in motor neuron disease

We performed median and tibial nerve somatosensory evoked potentials (SEPs), pattern-shift visual evoked potentials (PSVEPs), and brain-stem auditory evoked potentials (BAEPs) on 27 patients with motor neuron disease (MND). Median and tibial nerve SEPs were abnormal in 8 (30%) of 27 and 3 (14%) of 21 patients tested, respectively. Central and peripheral abnormalities were recorded in the absence of spondylosis. As a group, patients with MND and no evidence of cervical spondylosis had normal conduction to Erb's point following median nerve stimulation, but conduction times beyond this point were prolonged. The PSVEPs and BAEPs were within normal limits in all patients, excluding abnormalities attributable to other disease, but the group P100 latency was significantly prolonged in the group with MND. The BAEPs were normal in the group with MND. This study provides neurophysiological evidence of sensory system involvement in MND.     

Detection and peripheral or central localization of sensory pathway involvement of the lower limbs by somatosensory evoked potentials

In the presence of more or less atypical sensory or sensorimotor symptoms the questions that arise most frequently concern the authenticity of the disorders and the precise level of the lesion. In this study, somatosensory evoked potentials (SEPs) to stimulation of the tibial nerve at the ankle were recorded at different levels in 35 healthy subjects and 32 patients with sensory disorders. Recording electrodes were placed at the popliteal fossa (peripheral sensory nerve conduction velocity), at the T12-L1 level (medullary potential: N21) and at the vertex (P40 wave). The spine to cortex time interval was measured. A systematic study of evoked responses to median nerve stimulation was performed. The 32 patients were divided into 4 groups: Group I (3 cases) had slowed sensory conduction velocity (SCV), similar delay in N21 latency and normal N21-P40: peripheral neuropathy. Group II (4 cases) had normal SCV, delayed N21 latency and normal N21-P40: radicular or conus medullaris injury. Group III (19 cases) had normal SCV, normal N21 latency and lengthened N21-P40 interval. A study of responses to median nerve stimulation made it possible to discriminate between spinal and cortical or subcortical impairment. Group IV (6 cases) had abnormalities from any two of the three groups defined above. In 24 out of 32 patients (75 p. 100), further investigations (myelography, MRI, EMG) confirmed the localization determined by evoked responses. In the other 8 patients (25 p. 100) whose clinical picture suggested a medullary or radicular impairment, SEPs alone clearly revealed an injury. SEPs can distinctly show a spinal impairment and determine the choice of further investigations.     

Electrophysiologic study in acute lead poisoning

A 2-month-old girl with acute lead poisoning demonstrated electrophysiologic evidence of neurotoxicity. Motor nerve conduction studies of the median, ulnar, peroneal, and posterior tibial nerves revealed both axonal and demyelinating neuropathy. Somatosensory evoked potential studies of median and posterior tibial nerves demonstrated evidence of cortical involvement. Brainstem auditory evoked potential study disclosed the possibility of acoustic nerve involvement but no evidence of a brainstem lesion. Postmortem examination revealed cerebral edema and focal segmental demyelination of the median nerve.     

Adrenoleukodystrophy with high signal intensity areas in bilateral pyramidal tracts from internal capsule through medullary pyramids on MRI

We reported a case of adrenoleukodystrophy in which MRI showed high signal intensity areas in the pyramidal tracts from the internal capsule through the medullary pyramids. A 20-year-old man was admitted with complaints of slowly progressive spastic paraparesis of one and a half year duration. He had no mental deterioration, visual disturbance or sensory impairment. His maternal cousin died of adrenoleukodystrophy at the age of 13 years old, after showing progressive visual disturbance, dementia and quadriplegia. On admission, neurological examination revealed spastic tetraparesis and exaggerated deep tendon reflexes with pathological reflexes. Examination of the mental function and cranial nerves were normal. There were no sensory abnormalities in all modalities. Routine laboratory data including hematological studies, urinalysis, serum electrolytes and enzymes were all normal. Endocrinological examinations showed no adrenocortical insufficiency, and testicular function was normal. Cerebrospinal fluid, EEG, needle EMG and nerve conduction studies were also normal. CT scan showed a mild ventricular enlargement and no low density areas were seen in the cerebral white matter. Spin-echo MRI (SE 2,000/100, 2,000/40) revealed continuous high signal intensity areas in the pyramidal tracts from the internal capsule through medullary pyramids bilaterally. There were no abnormal findings in the spinal cord on MRI. Electrophysiologically, the brain-stem auditory evoked potentials (BAEPs) were abnormal and suggested the presence of bilateral dorsal brain stem lesions. Short latency somatosensory evoked potentials (SEPs) obtained by the bilateral tibial nerve stimulation revealed slowing of the central conduction time, showing delayed P37 latency and normal peripheral conduction time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Somatosensory evoked potentials in the evaluation of patients with stocking/glove paresthesias

We studied 10 patients referred for suspicion of peripheral neuropathy. They all complained of paresthesias with a stocking distribution. As EMG, motor and sensory nerve conduction studies failed to confirm the clinical diagnosis, we studied somatosensory evoked potentials (SEP) following median and tibial nerve stimulation. The SEP findings were compared with controls and 10 spastic paraplegias. The evoked potential study revealed prolonged latencies of cortical potentials after tibial nerve stimulation in all the patients with paresthesias and were considered evidence of myelopathy.     

Peripheral neuropathy in children on long-term phenytoin therapy

Nerve conduction studies of the ulnar, median, posterior tibial, peroneal and sural nerves were performed in 21 epileptic children aged 6 to 17 years on long-term phenytoin therapy. Auditory brain stem evoked responses were obtained in 16 patients to evaluate the effect of phenytoin on central nervous system synapses. Of the 21 patients examined, 15 (71.4%) showed abnormal findings. The most frequent abnormality was slowed motor conduction velocity of the ulnar nerve (33.3%) and posterior tibial nerve (23.8%), followed by slowed sensory conduction velocity of the sural nerve (20%), lowered H/M ratio (14.3%), slowed motor conduction velocity of the peroneal nerve (14.3%) and of the median nerve (14.2%). A significant correlation was noted between the total dosage and duration of therapy with PHT and the reduction of motor conduction velocity in the posterior tibial nerve. Auditory brain stem evoked responses showed no significant differences in each peak latency between the patients and the normal control group. The study indicates that long-term phenytoin therapy can cause latent impairment of peripheral nerve function in children with no clinical evidence of peripheral neuropathy.     

Electrocutaneous reflexes and multimodality evoked potentials in multiple sclerosis

Electrical stimulation of the digital nerves of the index finger produces changes in the EMG signal during steady voluntary contraction of the first dorsal interosseous muscle. This electrocutaneous reflex (ECR) was studied in 90 patients classified into different categories according to diagnostic criteria for multiple sclerosis. In addition, pattern reversal visual evoked responses (VER), brainstem auditory evoked responses (BAER) as well as spinal and scalp recorded somatosensory evoked potentials (SSEP) were investigated by stimulating both the index finger and the posterior tibial nerve. The reflex response was altered uni- or bilaterally in 56 per cent of the patients and the abnormalities of the ECR were related to the categories of diagnostic probability. Pathological results were found in 28 per cent of the hands without clinical evidence of sensorimotor deficit. Although ECR abnormalities were often associated with clinical signs, significant correlation was found only with hyperreflexia and/or increased muscle tone in the corresponding upper limb. Pathological ECR were more common than pathological SSEPs with finger stimulation recorded under identical stimulus conditions. Fewer abnormalities were found by ECR testing than with VER, but the proportion of abnormal ECR was higher than that of BAER. ECR provides a valuable supplement to existing electrophysiological procedures for detecting lesions in the central nervous system.     

A case of deaf–mutism as an expression of pure word deafness: neuroimaging and electrophysiological data

We report a case of pure word deafness, clinically expressed as deaf–mutism in a 17-year-old girl, who was affected from encephalitis when she was 18 months old and hadn't acquired language skills. Actually, physical examination revealed buccolingual apraxia and absence of spontaneous speech, auditory comprehension, repetition and denomination, whereas perception of non-verbal sounds was preserved. The seven waves of brainstem auditory evoked responses (BAER) were present with normal latencies; middle latency responses (MLR) were also normal. Magnetic resonance imaging (MRI) showed bilateral temporoparietal lesions. This case proves that lesions which may give rise to word deafness, when they occur in prelingual age, can determine a peculiar deafmutism clinical picture.     

Delayed somatosensory conduction in acute painful neuropathy of diabetes

We examined the peripheral–central sensory conduction by using somatosensory evoked potential (SEP) in a 48 year old diabetic patient with acute painful neuropathy. The sural, ulnar and median sensory nerve conduction and SEP elicited by wrist stimulation showed no abnormalities, nevertheless, the tibial nerve SEP revealed absent spinal N19 and a remarkable delay of the cortical arrival time. These findings suggest involvement of the dorsal roots or the dorsal column in the acute painful neuropathy of diabetes.     

Electrophysiological studies in five cases of abetalipoproteinemia

Auditory brainstem responses (ABRs), visual and somatosensory evoked responses (VEPs and SEPs) and nerve conduction studies were conducted in 5 patients with abetalipoproteinemia. The ABRs were normal in all cases. The VEPs were of normal amplitude but of increased latencies in two patients. The four eldest patients had delayed cortical SEPs but normal peripheral sensory nerve conduction studies. The peripheral motor conduction velocities were normal in all cases. The peripheral sensory studies showed normal velocity when a response was seen; however, the amplitude of the response was often reduced or it was absent. The electrophysiological studies reported here support a model of axonal loss of large myelinated fibres with secondary demyelination in abetalipoproteinemia.     

SHORT-LATENCY CORTICAL SOMATOSENSORY EVOKED RESPONSES OF PRETERM INFANTS WITH ULTRASOUND ABNORMALITY OF THE BRAIN

Somatosensory evoked response (SER) testing was carried out on 30 neonates with abnormality of the brain diagnosed by ultrasound, and the results were compared with previously defined normal ranges. The N1 peak latencies of the cortical SER were significantly different from normal, but peripheral nerve conduction velocities were not. Early neurological follow-up of these infants suggests that the cortical SER shows good correlation with neurological and developmental outcome, and may provide useful additional diagnostic information to cranial ultrasound for these high-risk infants.     

Evaluation of central nervous system involvement in uncomplicated optic neuritis after prolonged follow-up

Magnetic resonance imaging (MRI), multimodal evoked responses (ER) and HLA antigens were examined in 10 patients with idiopathic acute optic neuritis (ON) without any clinical symptoms or signs of multiple sclerosis (MS) during 9-14 years. In MRI, abnormalities compatible with MS were seen in 4 patients. In spite of clinically unilateral ON, a bilateral abnormality in visual evoked responses (VER) was seen in 3 of 9 cases. Brain stem auditory evoked responses (BAER) were normal in all cases, short latency somatosensory evoked response (SER) in all but one. The cerebrospinal fluid at time of ON showed signs of demyelination in one case only. The frequency of HLA antigens DR2 (78%) and B18 (40%) was significantly increased in comparison to healthy controls. MRI seems to be the most sensitive method in the detection of cerebral lesions of MS, especially in mild or asymptomatic forms of the disease. The present techniques are, however, mostly unable to demonstrate optic nerve lesions which more reliably can be evaluated by VERs. The question whether idiopathic ON represents a form of MS solely, cannot be resolved.     

Somatosensory evoked potentials in amyotrophic lateral sclerosis.

Forty five patients with amyotrophic lateral sclerosis were investigated, by means of somatosensory evoked potentials, in order to detect the presence of subclinical sensory changes. Cervical SEPs from the median nerve and cortical SEPs from the median and tibial nerve were recorded, showing a delay of N13 and subsequent components; the latency of the first constant cortical potential was also increased in many patients. Only the SEPs from the tibial nerve showed a decrease of amplitude. These results suggest a pathological slowing of conduction along the central sensory pathways in amyotrophic lateral sclerosis.     

Electrophysiological studies in spinocerebellar ataxia type 6: a statistical approach

In spinocerebellar ataxia type 6 (SCA6), the cerebellum is predominantly affected, but several electrophysiological studies have revealed subclinical disorders other than cerebellar lesions. We conducted statistical analyses by comparing SCA6 patients and age-matched normal controls to asses whether electrophysiological abnormalities are directly associated with SCA6 because late onset of SCA6 may involve senile changes. We performed brain stem auditory evoked potentials (BAEP), visual evoked potentials, somatosensory evoked potentials and nerve conduction studies in 10 SCA6 patients. The BAEP latencies of wave I was prolonged and compound muscle action potentials of peroneal nerve and sensory nerve action potentials of sural nerve reduced in SCA6 patients. Our results suggest an existence of peripheral impairment in the auditory pathway and axonal neuropathy in SCA6.     

A case of Moebius syndrome--electrophysiological studies of facial nerve and brainstem]

A five-year old boy was the product of a 40 week pregnancy by vertex presentation complicated only by threatened abortion at approximately 8 weeks gestation. Apgar score was 5 after one minute. At birth he was noted to have a generalized hypotonia associated with facial diplegia, small mandible, weak suck and swallow reflexes. Admission examination revealed small mandible, mask-like facial expression and mild mental retardation. Cranial nerve examination showed bilateral blepharoptosis and facial nerve palsies. Pupil reflexes were normal, but corneal reflexes were impaired bilaterally. Diplopia due to the left abducens nerve palsy was suggested. There was no atrophy of the tongue. Motor tone, strength, and deep tendon reflexes were normal. A normal 46 XY karyotype was present. The other clinical and laboratory findings were normal. MRI of the brain was unremarkable. The characteristics of electrophysiological studies were summarized as follows: 1) Auditory brainstem evoked responses demonstrated waveforms IV-V were abnormal because their amplitudes were less than 30% of wave I bilaterally. 2) Somatosensory evoked potentials documented by central conduction times from cervical region to sensory cortex were prolonged on both sides. 3) Facial nerve conduction velocity was calculated by evoked EMGs of the mentalis muscle electrically stimulated at two distal points over the marginal mandibular branch. MCV of the left side was reduced (34.2 m/sec). 4) The amplitude of the facial muscle potentials evoked by facial nerve stimulation was reduced on both sides. 5) Blink reflex responses documented by the latency difference of R1 responses between the two sides were prolonged.(ABSTRACT TRUNCATED AT 250 WORDS)     

Auditory brain stem and middle latency responses in a patient with cortical deafness

Auditory brain stem (ABR) and middle latency responses (MLR) were recorded in a patient with bilateral temporal lobe lesions. Audiological and higher cortical functions were assessed using conventional behavioral methods. Roentgenological findings were presented for localizing the lesions. Initially the patient showed no behavioral response to sound. Subsequently the patient reported inconsistent awareness of environmental sounds and pure tone sensitivity was impaired to a severe degree. Higher cortical function was essentially intact and the patient was not aphasic. ABR and acoustic reflex findings were consistent with normal functioning of the auditory periphery and brain stem pathways. MLR component Pa was absent bilaterally. These findings suggest that MLR component is bilaterally generated in the temporal lobes. Auditory cortex appears to play a role in auditory sensitivity in humans.     

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.     

Usefulness of BAER studies in the early diagnosis of Pelizaeus-Merzbacher disease

Brainstem auditory evoked responses (BAERs) were markedly abnormal in a 1-month-old infant with Pelizaeus-Merzbacher disease. Wave II occurred at a prolonged latency, and all of the following waves were absent bilaterally. BAER is useful for early diagnosis in this disease.