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PubMed2000

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.

Adult↗

PubMed1988

Auditory brainstem response patterns in familial and sporadic olivopontocerebellar atrophy.

Auditory brainstem responses (ABR) have been obtained in 22 patients, 15 with familial and 7 with sporadic olivopontocerebellar atrophy; 8 of them were pairs of siblings. ABR abnormalities have been found in 72.7%, with a significant higher percentage in familial versus sporadic patients. Similar ABR patterns have been obtained in affected members of the same family. No correlations have been found between ABR results and the following parameters: age, gender, disease duration, degree of clinical involvement and fashion of inheritance. ABR pattern did not show any modification over a follow-up period of 15-24 months. Our findings suggest that the involvement of the auditory pathways may be under genetic control.

Adult↗

PubMed1988

Auditory brain stem responses in dyslexic and normal children. A prospective clinical investigation.

Auditory Brain stem Responses (ABR) were performed prospectively in 24 severely constitutionally dyslexic children. None of the subjects showed any signs of organic or psychologic abnormality. The results were matched with a corresponding group of normal children. The response latencies of the two groups were almost identical (no statistically significant difference). We conclude that dysfunction of the brain stem auditory pathways should not be expected in constitutionally dyslexic children.

Adolescent↗

PubMed1992

Auditory evoked response in patients of diabetes mellitus.

Brainstem auditory evoked response (BAER) and the mid latency response (MLR) were recorded in 25 diabetic men and compared with a group of 25 control subjects. The threshold of hearing was higher (P less than 0.001) in the patients. The BAER peak latencies were also significantly prolonged in both the ears; however, the degree of prolongation was more prominent in the right ear. The interpeak latencies of waves I-III were also prolonged (P less than 0.01) in the left ear, with non significant increase noticed in the right ear also. The wave V amplitude was lower (P less than 0.05) in diabetics. The MLR, on the other hand, was not affected in patients. These findings suggest functional impairment in the auditory pathway in patients of diabetes mellitus.

Adult↗

PubMedDate not supplied

Auditory dysfunction caused by multiple sclerosis: detection with MR imaging.

We reviewed the MR examinations of 167 patients who presented over a 3-year period with a chief symptom of hearing loss and/or tinnitus. In 14 of these patients the only MR abnormality was the presence of multiple parenchymal high-signal foci on T2-weighted images. Nine of the 14 had clinical evidence of multiple sclerosis; the remaining five had no clinical evidence of multiple sclerosis. Lesions in the auditory pathways, potentially responsible for the patients' symptoms, were identified in only five cases. We recommend T2-weighted images of the whole brain in addition to T1-weighted images of the internal auditory canals and cerebellopontine angles in patients with hearing loss. In some patients, lesions found at higher levels in the periventricular white matter may provide the only clue to the origin of auditory abnormalities.

Adult↗

PubMed1992

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↗

PubMed1995

Morphology and spatial distribution of corticothalamic terminals originating from the cat auditory cortex.

In this paper we studied the morphology and spatial distribution of corticothalamic axons and terminals originating from the auditory cortical fields of the cat. The anterograde tracer biocytin was injected at electrophysiologically characterized loci in the primary (AI) (N = 2), anterior (AAF) (N = 1), posterior (PAF) (N = 1) and secondary (AII) (N = 2) auditory fields. In all cases, two different types of labeled terminals were found in the auditory thalamus: small spherical endings (1-2 microns) and giant, finger-like endings (5-10 microns). After biocytin injections in AI and AAF, the majority of anterogradely labeled axons terminated in the rostral half of the pars lateralis (LV) of the ventral division of the medial geniculate body (vMGB). In LV, the corticothalamic axons ramified profusely, giving rise to dense terminal fields forming well delineated curved stripes, with small spherical endings. Additional terminal fields formed by small endings were observed in the medial division of the medial geniculate body (mMGB). Giant endings were observed in a small area in the dorsal nucleus (D) of the dorsal division of the medial geniculate body (dMGB), near its border with the vMGB. PAF projections were located in the caudal half of vMGB and in mMGB, where only small terminals were found. Giant endings were seen in the superficial part of dMGB emerging from labeled corticothalamic axons oriented in parallel to the dorsal surface of the MGB. Projections from AII gave rise to a main terminal field of small endings in D; a second terminal field consisting of giant endings intermingled with small endings was found in the deep dorsal nucleus (DD) of dMGB. We conclude that small terminals serve the feedback projection to the thalamic nucleus from which the injected cortical field receives its main input, whereas giant terminals cross the borders between the parallel ascending auditory pathways.

Acoustic Stimulation↗

PubMedDate not supplied

Transient neurologic abnormalities and BAEPs in high-risk infants.

We examined brainstem auditory evoked potentials in 2 neurodevelopmentally different groups of high-risk premature infants during the first year of life. Our 77 patients were considered at birth to be at risk for neurologic disabilities, but were found to have normal development in the second year of life. The patients were divided into 2 groups on the basis of their neurologic findings during the first year of life; 24 of the 77 patients demonstrated transient neurologic abnormalities (group I) and the remaining 53 demonstrated normal neurologic findings through the first year of life (group II). Normative data of brainstem auditory evoked potentials were obtained from 60 low-risk and neurologically normal infants. Group I patients had prolonged III-V and I-V intervals at 2 months of age or younger and poorly detectable waves VI and VII at 5 months of age or younger, compared with control subjects. Wave VI was poorly detected in group II patients only at 35-39 weeks of conceptional age. Brainstem auditory evoked potentials suggested that the patients with transient neurologic abnormalities had transient dysfunction or maturational delay in the brainstem and upper auditory pathway early in the first year of life.

Evoked Potentials, Auditory, Brain Stem↗

PubMed1983

Brainstem auditory-evoked potentials in progressive myoclonus epilepsy without Lafora bodies.

We studied brainstem auditory-evoked potentials of 11 patients suffering from the Finnish type of progressive myoclonus epilepsy (without Lafora bodies). All patients were ambulatory and had regular antiepileptic medication. The responses of 5 patients were interpreted as totally normal. In 6 cases there were slight deformations of the wave forms or of the amplitudes of the responses. The central conduction time of all patients was within the +/- 2 S.D. limits of the normal values. Postauricular muscular responses were not more prominent in patients than in controls. The results indicate that there is not any significant dysfunction in the cholinergic auditory pathways of the brainstem of these patients.

Adolescent↗

PubMed2002

Auditory brainstem evoked potentials in early-treated congenital hypothyroidism.

To evaluate the effect of early treatment of congenital hypothyroidism on central nervous system development, auditory brainstem evoked potentials were determined in 32 patients with hyperthyrotropinemia diagnosed during neonatal screening. The patients included 27 with congenital hypothyroidism and 5 with transient hypothyroidism. Abnormal auditory brainstem evoked potential tracings were found in 8 patients (congenital hypothyroidism in 7 and transient hypothyroidism in 1). Four of these patients had increased peripheral conduction time (wave I prolongation), and the other 4 had increased central conduction time (wave III or V prolongation). The patients with abnormal auditory brainstem evoked potentials did not show increased initial manifestations, yet 6 of them had lower initial thyroxine levels. Specific auditory brainstem evoked potential abnormalities were found in 25% of early-treated patients with congenital hypothyroidism. The possible causal relationship between deviant auditory brainstem evoked potential patterns and later neurodevelopment demands further clarification. This study suggests the usefulness of auditory brainstem evoked potential assessment to provide information about electrophysiologic deviation of the auditory pathway in patients with early-treated congenital hypothyroidism.

Child, Preschool↗

PubMed1985

Auditory brain stem response in experimentally induced hypothyroidism in albino rats.

In order to elucidate the relationship between the auditory function and the thyroid state, experiments were designed to study the effect of hypothyroidism on the onset of auditory brain stem response (ABR) in 26 adult myxedematous albino rats. A state of hypothyroidism was induced by daily oral administration of 6-N-propyl-2-thiouracil (PTU). In 23 out of 26 rats we found minor changes in the amplitudes of all ABR waves without any correlation with the rats' T4 variation. We noted a conspicuous, dynamic, and reversible change in the amplitude of the third wave (N3) of ABR which correlates directly with the thyroxin (T4) levels in the rats' blood. The electrophysiological finding in this report indicates a lesion in the auditory tracts in the brain stem but mainly in the second main relay station of the central auditory pathway, i.e., the superior olivary complex.

Animals↗

PubMed1994

[Auditory evoked potentials by electric stimulation of the cochlea].

The recording of auditory brain stem potentials evoked by electrical stimulation of the cochlea is a part of our assessment protocol before pediatric cochlear implantation. It constitutes an objective and reproducible method to estimate the stimulability of the auditory system for candidates to cochlear implant. Ten children, aged from 3 to 12 years, with deep deafness of the 2nd and 3rd group with no response to ABR, undergone electric stimulation of the cochlea. All patients were anesthetized and paralyzed. Electric pulses are delivered by a cochlear stimulator, through a transtympanic needle electrode, placed in the promontory. We record responses on a Medelec "Saphire" computer. One of the main problem we try to solve is the stimulus artefact which occurs during the first ms. The other one is to be sure that the recorded responses are corresponding to the neural activity of the auditory nerve and the brainstem auditory pathway.

Anesthesia, General↗

PubMedDate not supplied

[Auditory evoked potentials in addicts to organic solvent inhalation].

Organic solvents affect the membrane lipids of neurons and glial cell. This led us to search for auditory damage, by means of brainstem auditory evoked responses, in subjects with chronic inhalation of thinner. Waves III and V showed delayed latency at an intensity of 90 dB, and wave V was delayed at 70 and 30 dB; the interwave intervals I-III and I-V at 90 dB and the interpeak I-V at 70 dB were also retarded. Three subjects did not show a response to stimulation at 30 dB: pure tone audiometry showed biaural mild hypoacusia in them. These results show that chronic inhalation of thinner may alter the auditory pathway of addicts.

Administration, Inhalation↗

PubMed2001

The auditory startle reaction in parkinsonian disorders.

The auditory startle reaction to an unexpected loud stimulus is regarded as a brainstem reflex originating in the nucleus reticularis pontis caudalis and being distributed up the brainstem and down the spinal cord along slowly conducting pathways. Auditory startle responses (ASR) have been reported absent or reduced in progressive supranuclear palsy (PSP), and delayed in Parkinson's disease (PD), but normal in multiple-system atrophy (MSA). For the first time we studied ASR in patients fulfilling the clinical criteria of dementia with Lewy bodies (DLB) (n = 8), a neurodegenerative disorder characterized by cortical and subcortical depositions of Lewy bodies resulting in parkinsonism and progressive cognitive decline. For comparison, we also investigated patients with PD (n = 10), MSA (n = 7), PSP (n = 10), and age-matched healthy controls (n = 10). ASR were elicited by binaural high-intensity auditory stimuli. Surface electromyographic activity was simultaneously recorded from facial, upper, and lower extremity muscles. For each muscle, we assessed response probability and measured latency, amplitude, duration, and habituation rate. Patients with DLB had fewer and abnormally delayed ASR of low amplitude and short duration in extremity muscles compared to healthy controls. Furthermore, we confirm and extend previous findings of abnormal ASR in PSP and PD, and also demonstrate exaggerated ASR in extremity muscles of MSA patients. The different patterns of ASR abnormalities may reflect distinct types of brainstem dysfunction in DLB.

Acoustic Stimulation↗

PubMed2002

Sudden deafness and anterior inferior cerebellar artery infarction.

BACKGROUND AND PURPOSE: Acute ischemic stroke in the distribution of the anterior inferior cerebellar artery (AICA) is known to be associated with vertigo, nystagmus, facial weakness, and gait ataxia. Few reports have carefully examined the deafness associated with the AICA infarction. Furthermore, previous neurological reports have not emphasized the inner ear as a localization of sudden deafness. The aim of this study was to investigate the incidence of deafness associated with the AICA infarction and the sites predominantly involved in deafness. METHODS: Over 2 years, we prospectively identified 12 consecutive patients with unilateral AICA infarction diagnosed by brain MRI. Pure-tone audiogram, speech discrimination testing, stapedial reflex testing, and auditory brainstem response were performed to localize the site of lesion in the auditory pathways. Electronystagmography was also performed to evaluate the function of the vestibular system. RESULTS: The most common affected site on brain MRI was the middle cerebellar peduncle (n=11). Four patients had vertigo and/or acute auditory symptoms such as hearing loss or tinnitus as an isolated manifestation from 1 day to 2 months before infarction. Audiological testings confirmed sensorineural hearing loss in 11 patients (92%), predominantly cochlear in 6 patients, retrocochlear in 1 patient, and combined on the affected side cochlear and retrocochlear in 4 patients. Electronystagmography demonstrated no response to caloric stimulation in 10 patients (83%). CONCLUSIONS: In our series, sudden deafness was an important sign for the diagnosis of AICA infarction. Audiological examinations suggest that sudden deafness in AICA infarction is usually due to dysfunction of the cochlea resulting from ischemia to the inner ear.

Adult↗

PubMed1991

Physiologic measures of electrically evoked auditory system responsiveness: effects of pathology and electrical stimulation.

During the past years we have addressed issues of implant application in children related to candidate selection and time of implantation. The studies have incorporated an assessment of the utility of the electrically evoked middle latency response (EMLR) as a measure of responsiveness of the central auditory pathways elicited by electrical stimulation. We have demonstrated that the EMLR in the guinea pig is similar in waveform characteristics to the acoustically elicited MLR, that it is equal in sensitivity to the electrically evoked auditory brainstem response (EABR) and can be used to reflect the sensitivity of different sites of stimulation. Because of its longer latency, the EMLR shows far less sensitivity to electrical artifact than the EABR. While suprathreshold characteristics of the EMLR are affected by anesthesia (ketamine and xylazine), threshold is not. In the ototoxically deafened animal we have found a decrease in the amplitude input/output function slope with decreasing density of spiral ganglion cell survival and that moderately high intensity of electrical stimulation produces a temporary threshold shift (eTTS) in the EMLR. These data suggest that this measure may be useful in assessing surviving spiral ganglion cell populations for the selecting of candidates for implantation and establishing safe, functional, upper-limits of electrical stimulation for young children. Finally, we have found that early electrical stimulation can reduce the progress of spiral ganglion cell degeneration secondary to ototoxic-induced hair cell loss.

Acoustic Stimulation↗

PubMed1990

Visual and auditory evoked potential correlates of cerebral malformations.

To date there are no systematic studies of the evoked potential correlates of cerebral malformations. A total of 109 sensory evoked potential studies (20 ERGs, 61 VEPs and 28 ABRs) were performed in 27 children with defined cerebral malformations. Diagnoses were confirmed by CT scan, supplemented by MRI, cranial ultrasound, or neuropathological examination. Sensory evoked potential studies were abnormal in over half of patients studied, but the VEP was unable to identify or distinguish specific supratentorial cerebral malformations. ABR abnormalities were documented in cases of holoprosencephaly, lissencephaly, pachygyria and generalized megalencephaly. ABR abnormalities were not observed in septo-optic dysplasia or focal dysplasia of the cerebral cortex. We conclude that evoked potentials are not a diagnostic criterion of severe dysplasias, but rather serve as a supplementary tool for detecting the variable associated abnormalities of brain development that may affect visual and central auditory pathways or their cerebral cortical or brainstem targets.

Brain↗

PubMed1988

Normal ABR's in dyslexic children.

Auditory Brain stem Responses (ABR) were recorded in 24 severely constitutional dyslexic--and 21 normal children. The response latencies of the two groups were almost identical. We conclude that dysfunction of the brain stem auditory pathways should not be expected in dyslexic children.

Adolescent↗