Auditory DysFunction & Multiple Sclerosis

Subjects with BrainStem lesions due to either an infarct or Multiple Sclerosis (MS) underwent two types of BinAural testing (Lateralization Testing and InterAural Discrimination) for three types of sounds (Clicks and High and Low Frequency narrow-band noise) with two kinds of InterAural differences (Level and Time).

Two major types of abnormalities were revealed in the Lateralization performances:
1. Perception of all stimuli, regardless of InterAural differences (Time and/or Level) in the center of the head (center-oriented), or
2. Lateralization of all stimuli to one side or the other of the head (side-oriented)

Similar patterns of abnormal Lateralization (center-oriented and side-oriented) occurred for MS and Stroke patients. A subject's pattern of abnormal lateralization testing was the same regardless of the type of stimulus or type of InterAural disparity.

Lateralization testing was a more sensitive test than InterAural discrimination testing for both types of subjects.

Magnetic Resonance Image (MRI) scanning in three Orthogonal planes of the BrainStem was used to detect lesions. A semi-automated algorithm superimposed the Auditory Pathway onto each MRI section.

Whenever a lesion overlapped the Auditory Pathway, some BinAural performance was abnormal and vice versa.

Given a lateralization test abnormality, whether the pattern was center-oriented or side-oriented was mainly determined by lesion site.

Center-oriented performance was principally associated with Caudal Pontine lesions and side-oriented performance with lesions Rostral to the Superior Olivary Complex.

For lesions restricted to the Lateral Lemniscus and/or Inferior Colliculus, whether unilateral or bilateral, Just Noticeable Differences (JNDs) were nearly always abnormal, but for Caudal Pontine lesions JNDs could be normal or abnormal.

MS subjects were more sensitive to InterAural time delays than InterAural level differences particularly for Caudal Pontine lesions, while Stroke patients showed no differential sensitivity to the two kinds of InterAural differences.

These results suggest that Neural processing of BinAural stimuli is multilevel and begins with independent InterAural time and level analyzers in the Caudal Pons.

Four individuals diagnosed as having Multiple Sclerosis (MS) and four matched controls were assessed with the Arizona Battery for Communication Disorders (ABCD), a standardized battery of Memory and Cognitive-Linguistic tasks.

Subjects with MS and controls performed in an equivalent or nearly equivalent fashion for nine of the ABCD subtests.

For five of the subtests (Object Description, Generative Naming, Concept Definition, Generative Writing, and Picture Description), subjects with MS performed substantially lower than the control subjects.

Results of this pilot study suggest that portions of the ABCD may be useful in identifying profiles of Memory, and Cognitive-Linguistic Impairment among individuals with Multiple Sclerosis.

Further research using a larger sampling of individuals with MS is needed to more fully assess the usefulness of the ABCD with this population.

The present study examined the effects of Multiple Sclerosis (MS) on the N1, P2, and P300 components of the Late Auditory Evoked Potential (LAEP).

A group of 30 subjects with confirmed MS were compared with 30 control subjects who were pair-matched to the MS subjects with respect to age and gender.

A standard stimulus oddball procedure was used to elicit the LAEP, in which subjects had to selectively attend to rare tones randomly interspersed among more frequently occurring tones of a different frequency.

LAEPs were recorded with and without the presence of simultaneous Speech competition in the nontest ear.

Although the presence of Speech competition produced significant latency and amplitude changes with the different components of the LAEP, the magnitude of the changes were similar for both subject groups.

However, in comparison to the control group, a significantly higher proportion of MS subjects exhibited absent P300 responses on all test runs.

To understand the relationship between BrainStem lesions and Auditory Neurology in patients with Multiple Sclerosis, we compared ElectroPhysiological, Imaging, and Behavioral data in 38 patients with Probable or Definite Multiple Sclerosis and normal or near normal Hearing.

Behavioral Measures Included:

1. General Hearing Tests
   (Audiogram, Speech Discrimination)
2. Hearing Tests likely to be critically dependent upon BrainStem processing
   (Masking Level Difference, InterAural time and Level Discrimination).

BrainStem Auditory Evoked Potentials provided the ElectroPhysiological data. Multiplanar high-resolution MRI of the BrainStem provided the anatomical data.

InterAural Time Discrimination for high-frequency sounds was by far the most sensitive of all tests, with abnormalities in 71% of all subjects. Whenever any other test was abnormal this test was always abnormal.

InterAural Time Discrimination for low-frequency sounds and Evoked Potentials were closely related and next most sensitive, with abnormalities in approximately 40% of all subjects.

InterAural level discrimination and masking level difference were least sensitive with abnormalities in 10% of subjects.

Speech discrimination scores correlated significantly with the masking level differences, as well as with InterAural time discrimination for high-frequency sounds.

Pontine lesions were found in five of the 16 patients, in whom an objective method for detecting Magnetic Resonance lesions could be applied.

All four with lesions involving the Pontine Auditory Pathway had marked abnormalities in InterAural Time Discrimination and Evoked Potentials. None of the other 12 had Evoked Potentials abnormalities.

We conclude that Neurological tests requiring Precise Neural Timing can reveal Behavioral Deficits for Multiple Sclerosis lesions of the Auditory Pons that are otherwise 'Silent '.

Of all Neurological Systems the Auditory System at the level of the Pons is probably the most sensitive to Multiple Sclerosis Lesions, because of its exceptional dependence upon Neural Timing in the microsecond range.

And the lack of redundancy in the encoding of high-frequency sounds. Precise Neural Timing may be critical for some aspects of Speech Processing.

Disturbances of Hearing in Multiple Sclerosis patients have been variably reported, likely because standard Audiologic Testing emphasizes assessment of Peripheral, rather than Central, Auditory Function.

This study investigated a group of patients with Multiple Sclerosis (MS), prospectively selected on the basis of Magnetic Resonance Imaging (MRI) scans.

Five of these patients had DeMyelinating lesions that included the Rostral Auditory fiber tracts, while another seven patients had lesions restricted to BrainStem Auditory sites.

A further four had no lesions in the distribution of their Auditory Pathways. A comprehensive battery of Audiometric Tests, including standard Audiometry and RetroCochlear Testing, was performed.

In addition, their findings on ElectroPhysiologic Testing, including Auditory BrainStem Responses (ABR) and Middle Latency Responses (MLR), were studied.

Finally, their performances in Gap Detection and Speech Recognition in continuous and interrupted background noise were examined to assess their Auditory Temporal Resolution.

The MS patients were found to be selectively impaired under the interrupted masker of this Speech-in-noise paradigm, confirming a Temporal Processing Defect.

Furthermore, these patients' performances suggested a predominant role of ForeBrain Pathways in mediating Auditory Temporal Resolution.

An MS patient experienced sudden Hearing loss. BrainStem Auditory Evoked Potentials, previously normal, showed substantial abnormalities that suggested the impairment of the distal part of the Acoustic Nerve.

MRI detected a small HyperIntense lesion along the Acoustic Nerve; the lesion decreased in size and then disappeared after Steroid treatment.

This demonstrates that a DeMyelinating lesion in the distal tract of the Eighth Cranial Nerve (Auditory Nerve) may cause an acute Hearing loss in MS.

Objectives
To assess the processing of SpectroTemporal sound patterns in Multiple Sclerosis by using Auditory Evoked Potentials (AEPs) to complex harmonic tones.

Methods
22 patients with Definite Multiple Sclerosis but mild disability and no Auditory complaints were compared with 15 normal controls. Short latency AEPs were recorded using standard methods.

Long Latency AEPs were recorded to synthesized musical instrument tones, at onset every two seconds, at abrupt frequency changes every two seconds.

And at the end of a two second period of 16/s frequency changes. The subjects were inattentive but awake, reading irrelevant material.

Results
Short Latency AEPs were abnormal in only 4 of 22 patients, whereas long Latency AEPs were abnormal to one or more stimuli in 17 of 22.

No significant Latency prolongation was seen in response to onset and infrequent frequency changes (P1, N1, P2) but the Potentials at the end of 16/s frequency modulations.

Particularly the P2 peaking approximately 200 ms after the next expected change, were significantly delayed.

Conclusion
The delayed responses appear to be a mild disorder in the Processing Of Change in Temporal sound patterns.

The delay may be conceived of as extra time taken to compare the incoming sound with the contents of a Temporally Ordered Sensory Memory Store (the Long Auditory Store or Echoic Memory), which generates a response when the next expected frequency change fails to occur.

The defect cannot be ascribed to lesions of the Afferent Pathways and so may be due to disseminated Brain lesions visible or invisible on Magnetic Resonance Imaging.

Multiple Sclerosis is known to affect the Myelin of the Auditory Pathway resulting in acute hearing loss.

Two cases of sudden deafness due to Multiple Sclerosis have been evaluated by conventional Audiometry, BrainStem Auditory Evoked Response Audiometry and Transtympanic ElectroCochleoGraphy.

The abnormalities of the compound action potential in both patients (enhanced latency, abnormal adaptation using fast stimulus rate) and the normal Receptor Potentials (Cochlear Microphonic, Summating Potential).

As well as the absence of BrainStem Responses suggest a disturbance of synchronization at the level of the First Auditory Neuron.

The ElectroCochleoGraphy provides valuable information for the topodiagnosis of this and other Neural Hearing losses, especially in the absence of reliable BrainStem Responses.

Hearing disorders are a well-described symptom in patients with Multiple Sclerosis (MS). Unilateral or bilateral Hyperacusis or deafness in patients with normal sound audiometry is often attributed to DeMyelinating lesions in the Central Auditory Pathway.

Less known in MS is a Central Phonophobia, whereby acoustic stimuli provoke unpleasant and painful Paresthesia and lead to the corresponding avoidance behaviour.

In our comparison collective, patient 1 described acute shooting pain attacks in his right cheek each time set off by the ringing of the telephone.

Patient 2 complained of intensified, unbearable noise sensations when hearing nonlanguage acoustic stimuli.

Patient 3 noticed hearing unpleasant echoes and disorders of the directional hearing. All patients had a clinical Brainstem Syndrome. ENT inspection, Sound Audiometry and Stapedius reflex were normal.

All three patients had pathologically changed Auditory Evoked Potentials (AEPs) with indications of a BrainStem lesion, and in Magnetic Resonance Imaging (MRI) DeMyelinating lesions in the ipsilateral Pons and in the Central Auditory Pathway.

The origin we presume in case 1 is an abnormal impulse conduction from the Leminiscus Lateralis to the Central Trigeminus Pathway and, in the other cases, a disturbance in the central sensory modulation. All patients developed in the further course a clinically definite MS.

Having excluded peripheral causes for a Hyperacusis, such as, e.g., an idiopathic Facial Nerve Palsy or Myasthenia Gravis, one should always consider the possibility of MS in a case of Central Phonophobia.

Therapeutic possibilities include the giving of Serotonin Reuptake Inhibitors or acoustic lenses for clearly definable disturbing frequencies.

Objective
To investigate the role of Magnetic Resonance Imaging (MRI) in the diagnosis of Sudden Sensorineural Hearing Loss (SSNHL).

Methods
Fifty-four consecutive patients affected by SSNHL were investigated using Brain MRI. MRI was performed with an eight-channel phased-array head coil to study the entire AudioVestibular Pathway and the whole Brain.

The protocol study consisted of a high-resolution study of the temporal bone, Internal Auditory Canal (IAC), CerebelloPontine Angle (CPA), and BrainStem.

Combining 2 mm thin-slice axial T₂-weighted two-dimensional fast spin echo (FSE) and Fluid-Attenuated Inversion Recovery (FLAIR) sequences, pre- and postcontrast (gadolinium-diethylenetriamine pentaacetic acid) administration fat-suppressed axial T₁-weighted two-dimensional FSE sequences.

And a T(2)*-weighted three-dimensional Fourier transformation-constructive interference in steady state sequence (FT-CISS) , with 0.4 mm ultrathin partitions.

The rest of the Brain was studied with a 4 mm axial T₂-weighted FLAIR sequence.

Results
Thirty-one of 54 (57%) cases of SSNHL presented with MRI abnormalities.

In 6 of 54 cases, the detected abnormality was directly correlated to the clinical picture (2 Labyrinthine Hemorrhage, 1 Cochlear Inflammation, 1 Acoustic Neuroma, 1 Arachnoid Cyst of the CPA, and 1 case of White Matter lesions in the Pons, compatible with DeMyelinating plaques along the Central AudioVestibular Nervous Pathway, as the first expression of Multiple Sclerosis).