Stapedius reflex in multiple sclerosis

Quantification of the stapedial reflex reveals delayed responses in autism

Autism is a developmental disorder characterized, in part, by sensory abnormalities. It is well established that most if not all patients with autism have problems with auditory processing, ranging from deafness to hyperacusis, and physiological testing of auditory function (i.e. auditory brain stem responses) implicates brain stem dysfunction in autism. Additionally, previous research from this lab has revealed significantly fewer auditory brain stem neurons in autistic subjects as young as 2 years of age. These observations have led us to hypothesize that objective, noninvasive measures of auditory function can be used as an early screening tool to identify neonates with an elevated risk of carrying a diagnosis of autism. Here, we provide a detailed quantitative investigation of the acoustic stapedial reflex (ASR), a three- or four-neuron brain stem circuit, in young autistic subjects and normal developing controls. Indeed, we find significantly lower thresholds, responses occurring at significantly longer latency and right-left asymmetry in autistic subjects. The results from this investigation support deficits in auditory function as a cardinal feature of autism and suggest that individuals with autism can be identified by their ASR responses.

The acoustic reflex in patients with asymptomatic multiple sclerosis

A convenient, inexpensive test to identify multiple sclerosis during periods of symptomatic remission would be clinically advantageous. Recent studies have suggested that examination of acoustic reflex onset latency and rise time may be useful in detecting some forms of retrocochlear auditory pathology. This prospective, single-blinded study compares these features of the human acoustic reflex in a control sample, a sample with sensorineural hearing loss, and a sample with multiple sclerosis, to determine the usefulness of acoustic reflex measurements as a screening test for otherwise asymptomatic multiple sclerosis. Acoustic reflex threshold, onset latency, and rise time measurements were similar for all groups. This finding suggests that tests for abnormalities of acoustic reflex rise time and onset latency, under the conditions used in this study, may not be sufficiently sensitive to screen for the presence of otherwise asymptomatic multiple sclerosis.

Auditory brainstem response and audiologic findings in adrenoleukodystrophy: its variant and carrier

Auditory brain stem response, auditory sensitivity, speech discrimination function, acoustic reflex threshold, and reflex decay were studied in seven children with adrenoleukodystrophy (ALD), nine adults with adrenomyeloneuropathy (AMN), one child with neonatal ALD, and two carriers of ALD. Significant auditory dysfunctions were found in only two patients; a retrocochlear type auditory disorder in one child with ALD, and a profound deafness in a child with neonatal ALD. None of the patients showed significant abnormality in acoustic reflex threshold and reflex decay except for one patient with ALD who showed a slightly elevated reflex threshold. All but two ALD patients showed significantly prolonged wave latencies and interwave intervals. The latency values revealed the highest incidence of abnormality in the I to III interval; this was followed by the III to V interval, then by wave I. Significantly, one child with asymptomatic ALD and both heterozygous female relatives showed abnormal ABRs, demonstrating the high sensitivity of ABR in detection of the existence of pathophysiological condition in subclinical or presymptomatic ALD.

Abnormalities of the acoustic reflex in multiple sclerosis

Acoustic reflect morphology was examined in 122 patients with a diagnosis of definite multiple sclerosis. Abnormality in some dimension of acoustic reflex morphology was observed in 75 per cent of the study population. The most commonly observed abnormality was an alteration in one or more of the three relative amplitude indices (afferent, efferent, or central pathway index). Other abnormalities included delayed onset latency, delayed offset latency, reduction in absolute amplitude, and threshold elevation.

Stapedius reflex in multiple sclerosis

The stapedius reflex (StR) was studied in humans by impedance audiometry. Ipsilateral and contralateral reflexes, obtained from 48 multiple sclerosis (MS) patients and 26 controls, were analysed. MS patients showed smaller reflex amplitudes, longer onset latencies and higher contralateral reflex thresholds. Using onset latencies, 33% of all MS patients had at least two abnormal ipsi- and/or contralateral StRs. If the diagnosis was MS of the definite type, this figure was 39%. The StR is therefore a useful tool for detecting a subclinical lesion in the brainstem and can contribute to the early diagnosis of MS.

Problems in the clinical measurement of acoustic reflex latency

Two problems in the clinical measurement of acoustic reflex latency are discussed. First, the rise characteristic of the reflex is affected by the frequency of the eliciting signal. Due to the closed ipsilateral feedback loop system the reflex rises more rapidly at low frequencies than at high frequencies. Second, the temporal characteristic of the measurement apparatus may influence the apparent morphology of the reflex at low frequencies.

Acoustic reflex characteristics in hypo- and hyperthyroid patients

The various parameters of the stapedial reflex, evoked by acoustic stimuli and recorded using an impedance meter, were evaluated in untreated hyperthyroid and hypothyroid patients and in normal controls. In hyperthyroid patients neither the threshold nor the latency time, the rise time, the recovery time and the maximal amplitude of the reflex were different from normal subjects. On the contrary, hypothyroid patients showed a longer recovery time and a reduced maximal amplitude, suggesting, in the absence of alterations of middle ear structures, a weaker contractile activity of the stapedial muscle.

Stapedius reflex and brainstem auditory evoked responses in multiple sclerosis patients

The stapedius reflex (SR), its adaptation and the brainstem auditory evoked potential (ABR) were recorded in a group of 53 multiple sclerosis patients. All cases were classified as definite according to Schumacher's criteria, and their grade of disability in Hyllested's system was 1-4: no cases of the gravest (grades 5 and 6) disability were included in the series. The peripheral hearing (pure-tone audiogram and speech threshold) was normal in 44 and slightly impaired in 8 cases. SR was abnormal in 6 (11%) and borderline in 11 (21%), whereas the ABR was considered abnormal in 21 (40%) patients. Deviant SR and ABR findings had only slight or no correlation to clinical data. Intercorrelation between SR and ABR abnormality was better but not implicit and a few cases with deviant ABR showed normal SR: The frequency of abnormal and borderline SR findings was clearly higher in bilateral than in unilateral ABR abnormality. Subclassification of ABR into an upper and a lower type of pathology did not correlate with SR abnormality.

Relationships among auditory brain stem responses, masking level differences and the acoustic reflex in multiple sclerosis

We report the results of a study in which we compared auditory brain stem responses (ABR), the binaural masking level difference (MLD) for a 500-Hz pure tone and acoustic reflexes in 20 patients with confirmed multiple sclerosis. Our intent was to determine whether abnormalities in the three measures were related or whether they varied independently. The results indicated that the size of the MLD varied with the integrity of wave III of the ABR. When the ABR was abnormal to the extent of lacking wave III on one or both ears, there was no release from masking and the crossed acoustic reflex was abnormal, as well. The sensitivity of the MLD to retrocochlear disorder was comparable to that of ABR, and was greater than that provided by speech audiometry or acoustic reflexes.