Middle latency auditory evoked potentials in patients with parkinsonism

The aim of this study was to assess the middle latency auditory evoked potential (MLAEP) findings in idiopathic Parkinson's disease (IPD) and in patients who are regarded as having atypical parkinsonian disorders (AP) and to determine whether MLAEPs could contribute to the differential diagnosis of IPD and AP.MLAEPs were evaluated in 19 control subjects and in a total of 35 patients with parkinsonism, of which 27 had IPD and 8 had AP. Among IPD patients, P1 was absent in 1 nondemented patient with young-onset Parkinson's disease (YOPD) (5%) and in 2 of 7 demented (28.5%) IPD patients. In the AP group, 3 of the 7 (42.8%) nondemented patients and the one patient with dementia showed the absence of P1. The absence of P1 was found to be significantly higher in AP patients than IPD patients (p=0.0335).In conclusion, MLAEPs were found to be normal in nondemented IPD patients with only a few exceptions. The absence of P1 in nondemented patients with parkinsonian symptoms may bring the diagnosis of IPD into question. The absence of P1 could be detected in AP patients at least as often as in demented IPD patients. Thus, the measurement of MLAEPs may be a clinically useful adjunct to the clinical examination of patients with parkinsonism.     

The latency distribution of motor evoked potentials in patients with multiple sclerosis

Objective

To compare the individual latency distributions of motor evoked potentials (MEP) in patients with multiple sclerosis (MS) to the previously reported results in healthy subjects (Firmin et al., 2011).

Methods

We applied the previously reported method to measure the distribution of MEP latencies to 16 patients with MS. The method is based on transcranial magnetic stimulation and consists of a combination of the triple stimulation technique with a method originally developed to measure conduction velocity distributions in peripheral nerves.

Results

MEP latency distributions in MS typically showed two peaks. The individual MEP latency distributions were significantly wider in patients with MS than in healthy subjects. The mean triple stimulation delay extension at the 75% quantile, a proxy for MEP latency distribution width, was 7.3 ms in healthy subjects and 10.7 ms in patients with MS.

Conclusions

In patients with MS, slow portions of the central motor pathway contribute more to the MEP than in healthy subjects. The bimodal distribution found in healthy subjects is preserved in MS.

Significance

Our method to measure the distribution of MEP latencies is suitable to detect alterations in the relative contribution of corticospinal tract portions with long MEP latencies to motor conduction.     

Middle latency auditory evoked potentials (MAEPs) in chronic schizophrenics.

Middle latency auditory evoked potentials were recorded in medicated chronic schizophrenics and controls at stimulation rates of 10/s, 2/s, and 1/s. Increasing the stimulation rate did not change Pa amplitude but decreased Pb amplitude. There was no difference between the two groups.     

Middle latency auditory evoked potentials in cortical lesions. Critical of interhemispheric asymmetry

Middle latency auditory evoked potentials after monaural stimulation have been recorded in 16 normal subjects and in 21 patients with unilateral cortical or subcortical lesions determined by computed tomographic scan examination. An interhemispheric index was studied to quantify the asymmetry of Na and Pa middle latency auditory evoked potential components recorded over each hemisphere. This index has been calculated for each ear separately and after adding the responses of both ears. Its reliability is shown to be better in the latter situation. In all of the patients the interhemispheric asymmetry index was in the normal range for the Na component. For the Pa component this index was abnormal in 11 patients with cortical temporal lobe or subcortical lesions interrupting acoustic radiations. These results confirm that the Pa is dependent on the integrity of acoustic radiations and auditory cortex in the supratemporal plane, whereas the Na component would be generated at a subcortical level. Unilateral extinction of the dichotic listening test was found to correlate with abnormal Pa component asymmetry in the case of lesions involving the auditory structures.     

Brainstem auditory evoked potentials in the diagnosis of multiple sclerosis

Brainstem auditory evoked potentials (BAEPs) have been investigated in 34 patients affected by Multiple Sclerosis. Abnormalities were found in 68% of the patients. Silent lesions of the brainstem were detected in 60% of the clinically definite and in 44% of the probable cases. The diagnostic value of these findings is discussed.

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Sommario I potenziali evocati uditivi sono stati investigati in 34 pazienti affetti da sclerosi multipla. Anormalità sono state evidenziate nel 68% dei pazienti affetti da sclerosi multipla clinicamente definita. Lesioni silenti del brainstem sono state trovate nel 60% delle forme clinicamente definite e nel 44% di quelle probabili. Il valore diagnostico di questi reperti è discusso.

     

Brainstem auditory evoked potentials evoked by clicks of different polarity in multiple sclerosis patients

Brainstem auditory evoked potentials (BAEP) evoked by condensation, rarefaction clicks and clicks of alternating polarity were examined in 52 controls and in 95 patients with a certain or presumed diagnosis of multiple sclerosis. It was shown that the type of stimulation could influence the shape of the BAEP considerably. In multiple sclerosis patients pathological results were found in 67 ears from 44 patients. Rarefaction as well as condensation clicks independently could elicit BAEPs with increased latencies of one or more peaks, while clicks of alternating polarity failed to detect abnormalities in a great number of cases. These findings make the application of the latter type of stimulation doubtful.     

Brainstem auditory evoked potentials and middle latency auditory evoked potentials in young children

Measurements of brainstem auditory evoked potentials (BAEP) and middle latency auditory evoked potentials (MLAEP) are readily available neurophysiologic assessments. The generators for BAEP are believed to involve the structures of cochlear nerve, cochlear nucleus, superior olive complex, dorsal and rostral pons, and lateral lemniscus. The generators for MLAEP are assumed to be located in the subcortical area and auditory cortex. BAEP are commonly used in evaluating children with autistic and hearing disorders. However, measurement of MLAEP is rarely performed in young children. To explore the feasibility of this procedure in young children, we retrospectively reviewed our neurophysiology databank and charts for a 3-year period to identify subjects who had both BAEP and MLAEP performed. Subjects with known or identifiable central nervous system abnormalities from the history, neurologic examination and neuroimaging studies were excluded. This cohort of 93 children up to 3 years of age was divided into 10 groups based on the age at testing (upper limits of: 1 week; 1, 2, 4, 6, 8, 10 and 12 months; 2 years; and 3 years of age). Evolution of peak latency, interpeak latency and amplitude of waveforms in BAEP and MLAEP were demonstrated. We concluded that measurement of BAEP and MLAEP is feasible in children, as early as the first few months of life. The combination of both MLAEP and BAEP may increase the diagnostic sensitivity of neurophysiologic assessment of the integrity or functional status of both the peripheral (acoustic nerve) and the central (brainstem, subcortical and cortical) auditory conduction systems in young children with developmental speech and language disorders.     

Wave I of early auditory evoked potentials in multiple sclerosis

Early auditory evoked potentials (EAEPs) were recorded in a series of 71 consecutively examined patients suffering from clinically definite or probable multiple sclerosis (MS). Wave I abnormalities, i.e., delayed latency, with or without reduced amplitude, were observed in 15 such patients and were interpreted as due to MS in 8 of them. As EAEP wave I is identical with the potential N1 in electrocochleography and corresponds to activity of the most distal part of the acoustic nerve or the spiral ganglion, it is concluded that the peripheral part of the acoustic nerve is involved in about 10% of MS patients. In two cases normalization of initially delayed wave I latencies were demonstrated during follow-up recording. The pattern of a late wave I but normal hearing in 3 patients is interpreted in terms of a desynchronized compound nerve activity with fully preserved conductivity, segmental demyelination of a considerable number of acoustic nerve fibres being the most likely cause.     

Middle latency auditory evoked potentials (MLAEPs) in (MS)

Middle latency auditory evoked potentials (MLAEPs) were studied in 30 definite multiple sclerosis (MS) patients in addition to brain-stem auditory evoked potentials (BAEPs). BAEP abnormalities were detected in 18 (60%) patients. MLAEPs were abnormal in 22 (73%) of them. In 15 patients BAEPs and MLAEPs were both abnormal. MLAEPs were found abnormal in 7 of the 12 patients with normal BAEPs. In 18 patients with abnormal BAEPs only 3 had normal MLAEPs. MLAEPs abnormalities are consistent with a rostral auditory pathway involvement. Therefore, they can be used in combination with BAEPs to examine the whole auditory system to improve the sensitivity.     

Evaluation of ipsilateral and contralateral brainstem auditory evoked potentials in multiple sclerosis patients

Brainstem auditory evoked potentials (BAEP) were recorded simultaneously between the vertex and the mastoid ipsilateral and contralateral to the ear stimulated in 30 patients with multiple sclerosis (MS) and compared with the responses in a control group of 30 normal hearing adults. The control group showed that significant latency differences exist between ipsilateral and contralateral recording. Definitions of abnormalities were based on interwave separation and the wave V amplitude ratio. No case was found among the MS patients with an abnormal contralateral but normal ipsilateral response.     

Early abnormalities of evoked potentials and future disability in patients with multiple sclerosis

Evoked potentials (EP) have a role in making the diagnosis of multiple sclerosis (MS) but their implication for predicting the future disease course in MS is under debate. EP data of 94 MS patients examined at first presentation, and after five and ten years were retrospectively analysed. Patients were divided into two groups in relation to the prior duration of disease at the time point of first examination: group 1 patients (n=44) were first examined within two years after disease onset, and group 2 patients (n=50) at later time points. As primary measures sum scores were calculated for abnormalities of single and combined EP (visual (VEP), somatosensory (SEP), magnetic motor evoked potentials (MEP)). In patients examined early after disease onset (group 1), a significant predictive value for abnormal EP was found with MEP and SEP sum scores at first presentation correlating significantly with Expanded Disability Status Scale (EDSS) values after five years, while the VEP sum score was not. The cumulative number of abnormal MEP, SEP and VEP results also indicated higher degrees of disability (EDSS > or = 3.5) after five years. Combined pathological SEP and MEP findings at first presentation best predicted clinical disability (EDSS > or = 3.5) after five years (odds ratio 11.0). EP data and EDSS at first presentation were not significantly linked suggesting that EP abnormalities at least in part represented clinically silent lesions not mirrored by EDSS. For patients in later disease phases (group 2), no significant associations between EP data at first presentation and EDSS at five and ten years were detected. Together with clinical findings and MR imaging, combined EP data may help to identify patients at high risk of long-term clinical deterioration and guide decisions as to immunomodulatory treatment.     

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.     

Vestibular evoked myogenic potentials in multiple sclerosis patients.

OBJECTIVES: Vestibular evoked myogenic potentials (VEMPs) are saccular responses to loud acoustic stimuli and are recordable from the sterno-cleido-mastoid muscle ipsilaterally to the stimulated ear. This study aimed to investigate VEMPs in patients suffering from multiple sclerosis (MS), and to compare these findings with both clinical and instrumental data. METHODS: We recorded VEMPs from 70 MS patients, whose clinical data were retrospectively evaluated for the possible occurrence of: past and current (with respect to VEMP recording) brainstem and/or cerebellar symptoms; current brainstem and/or cerebellar signs. Sixty-five patients underwent brainstem auditory evoked potentials (BAEPs) recording; 63 of the same patients underwent saccadic eye movement recording and subjective visual vertical (SVV) evaluation. RESULTS: VEMPs were abnormal in 31%, BAEPs in 38% and SVV in 21% of the patients. Saccadic eye movements showed a possible brainstem dysfunction in 44.4% of the patients. There was no correlation between the occurrence of abnormalities and the technical means of detection. The same held true for correlations with clinical data, with the exception of the BAEPs; these proved to be more frequently abnormal in patients presenting at neurological examination with brainstem and/or cerebellar signs that were possibly related to the complaint of dizziness. CONCLUSIONS: VEMPs should be considered a useful complementary neurophysiological tool for the evaluation of brainstem dysfunction.     

Vector analysis of brain-stem auditory evoked potentials in patients with multiple sclerosis and subtentorial tumors.

Vector analysis of BAEPs was done in 10 patients with posterior fossa tumors and 14 patients with MS. Latency abnormalities were found in both groups without significant differences. However, deviations of wave V vectors from its normal orientation were observed in tumor cases, correlated with tumor size and latency increase. It is concluded that vector deviations may indicate distortion of auditory pathways in the brain-stem.     

Brain stem auditory evoked potentials and blink reflexes in quiescent multiple sclerosis.

Brain stem auditory evoked potentials (BAEP) and blink reflexes (BR) were studied in 25 patients with multiple sclerosis (MS), the diagnosis being definite according to McAlpine's criteria, in the quiescent phase, without signs of brain stem involvement. BAEP abnormalities were found in 64% of the cases and BR abnormalities in 60%. A good correlation between the two tests was found in most patients. The abnormalities consisted of delayed latencies and/or high intraindividual variability in shape and latency of BAEP and BR components. It seems that demyelination of brain stem pathways results not only in conduction slowing but also in more serious dysfunction of the generators of the evoked components.     

Age-related latency changes in the brain-stem auditory evoked potentials

The effects of age on the brain-stem auditory evoked potentials were studied on 156 healthy subjects with ages ranging from 18 to 76 years. The latencies of peaks I-VII and the interpeak latencies of I-III, III-V and I-V were consistently shorter for the female group than the male group. The females also had higher peak amplitude than the males. The effects of sex on the peak and interpeak latencies were observed in all age groups. There was a small progressive prolongation in the peak latency with increasing age, particularly peak V. Although a correlation between the age and the I-III interval was not observed, there was also a small increase with age in the interpeak latencies of III-V and I-V.     

The functional anatomy of middle latency auditory evoked potentials.

The neural origins of middle latency auditory evoked potentials (MAEP) were studied in rat cortex. MAEP were mapped from the cortical surface with a high spatial resolution electrode array. Spatiotemporal analysis, based on multivariate statistical methods, was then used to relate putative neural generators of the MAEP complex to established cytoarchitectural anatomy. These data indicate that the MAEP waveform reflects systematic asynchronous activation of both primary and secondary auditory cortex during the processing of simple click stimuli.