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Multiple Sclerosis and Hearing Loss

By George Cook, Au.D., CCC-A

Over the years I have had several friends with Multiple Sclerosis (MS). Some have had the disease for many years and others have had rather rapid declines resulting in death. This article was generated by a recent request for information concerning this terrible scourge and its relation to hearing loss. As you will read in the article, hearing loss and balance problems can result from MS and, although rare, can be an initial symptom of MS.

Overview of Pathology

Etiology
Multiple sclerosis is a degenerative autoimmune disease of the central nervous system (CNS). Current belief is that it is an immunologic disturbance triggered by a virus in individuals who are genetically susceptible. The name signifies number (multiple) and condition of scarring and hardening (sclerosis) of the demyelinated areas in the CNS.

Anatomy and Physiology
Inflammation occurs in areas of white matter of the CNS in random patches called plaques and results in demyelination. It occurs most frequently in supratentorial white matter, especially the periventricular region. The plaques occur less frequently in cerebellum, brainstem, and cervical spinal cord areas. In MS, T-cells leak out of the blood vessels and produce agents that attack the myelin sheath of nerve fibers. Occurring at multiple sites (at least two for a diagnosis of MS) they result in nerve impulses being slowed, distorted or halted producing a variety of symptoms. Once the inflammation has subsided, the nervous system begins repair, thus producing a cycle of progression and remission. If the nervous system cannot keep up, chronic progression occurs. Hearing loss is associated with lesions of the brainstem and VIII C.N. as it enters the brainstem or at other sites along the auditory pathway.

Incidence
Estimates of between 350 to 400 thousand MS cases have been diagnosed in the U.S. with 200 cases diagnosed each week. MS has an onset in early adulthood between 20-40 years with a ratio of two men to three women. Caucasians are twice more likely to have MS than other races. MS is five times more prevalent in temperate climates (above 37th parallel, 110-140 cases per 100,000) than in the tropical regions (below 37th parallel, 57-78 cases per 100,000).

Genetic considerations
Most individuals exposed do not develop MS without a genetic influence. An individual’s chance of developing MS is less than one tenth of one percent in the general population (1 in 1,000). However, if one person in a family has MS the risk becomes one to three percent. Because of indications that viral infections may precipitate an MS attack, the disease is thought to have an environmental trigger.

Classification/Type
Most cases are mild in nature with slow progression, but the disease can be aggressive and devastating. Progression of MS is characterized by episodes of progression, remission, and exacerbation. Risk of progression is greatest after acute viral illnesses.

Symbol
Type of MS
Description
Benign
20-70 percent show complete or partial remission after initial onset in early stages. 
Malignant
Rare, swift and relentless decline resulting in significant disability and even death shortly after onset.
RR
Relapsing-Remitting
Repeated attacks followed by complete or partial remission and periods of stability.
Chronic Progressive
SP
Secondary Progressive
Begins with RR and later develops into PP
PP
Primary Progressive
Gradual decline with no remissions. May have temporary plateaus.
PR
Progressive-Relapsing
Rare, progressive path punctuated by acute attacks.


Symptoms
Visual disturbances as diplopia, blurred vision, red-green color distortion may occur early and in 15% of cases is the initial symptom due to involvement of optic nerve. Fatigue, spasticity, and weakness in extremities following exertion or warm temperatures are common. One half of MS patients experience mild cognitive difficulties as concentration, attention, memory, and poor judgment. Other common symptoms include balance problems, dizziness, faintness, unsteadiness, spatial disorientation, and vertigo. Paresthesias and rarely pain may be exhibited. Damage to the V cranial nerve can result in a painful condition known as trigeminal neuralgia.  Speech may be affected in areas of articulation, respiration, and prosody. Other symptoms include nausea, emesis, and sweating. Depression and mood changes are common with psychosis present in extreme cases. Bladder and bowel control may be a problem. Sexual problems are common. Symptoms often remit or stabilize during pregnancy only to reoccur 3 or 4 months after delivery.

MS has a low incidence of hearing acuity loss (6%) or tinnitus. In rare cases, hearing loss is reported as the first symptom, and in exceedingly rare cases MS has resulted in deafness. Hearing loss caused by acute episodes of MS tends to improve.

Other similar syndromic conditions
Stroke, Lyme disease, AIDS, Syphilis, Diabetes Mellitus, brain stem infarcts, brain stem gliomas, acoustic neuroma.

Typical symptom presentation of audiological characteristics
Usually normal hearing acuity is found. Cochlear function is not usually affected. In cases with hearing loss, 85% show sensorineural bilateral high frequency loss. The hearing loss is sometimes unilateral and occasionally it is sudden. One clinician reported that up to 40% of MS patients with normal audiograms report difficulty hearing in background noise.

Typical audiological and vestibular test results
Immittance testing is usually normal for tympanometry and ipsilateral reflexes. Ipsilateral reflex decay may be absent. Contralateral reflex may be absent, reflex decay may be absent or not testable if crossover fibers of the brainstem are involved.

Speech discrimination may be poorer than indicated by pure tone thresholds. Central auditory perceptual testing (CAPT) can be used to assess central auditory pathways and possible retrocochlear lesions. Staggered Spondaic Word Test (SSW), Synthetic Speech Sentence Identification Test (SSI), Competing Sentence Test, Binaural Fusion Test and Rapidly Alternating Speech tests may be used.

ABR testing is very useful in diagnosing MS. Results frequently show abnormalities as absent waveforms except I, delays in absolute latencies for waveforms, delays in interpeak latencies for I, III, and V, interaural latency of V and I-V, and poor wave form morphology and amplitudes of waves III and V. Reduction in click rate often does not result in improvement. ABR can be normal for persons with MS if the brainstem is not involved. A small plaque in the auditory brainstem pathway can alter the ABR.

Balance problems are frequently due to demyelination in the cerebellopotine angle, brainstem, and vestibular spinal tracts. Vestibular symptoms may be aggravated by head or eye movement.

ENG testing can show a wide range of abnormalities and types of nystagmus, including suppression, due to vestibular and oculomotor involvement. Saccade testing may reveal slow velocities and prolonged latencies. Vertical gaze nystagmus may be present when looking upward. Abnormalities in smooth pursuit or sinusoidal tracking indicate cerebellar lesion. Positional nystagmus is frequently present and is characterized as geotropic direction fixed and nonfatigable. Calorics (peripheral assessment) abnormalities include unilateral weakness and directional preponderance due to lesions of central vestibulocular pathways.

Dynamic platform posturography may reveal poor performance in sensory organization tests (SOT) conditions 4, 5, and 6. Impaired conduction in spinal somatosensory feedback from the lower body results in prolonged latencies in the motor control test (MCT).      

Intervention and Rehabilitation
Rehabilitation training including physical therapy for vestibular training may be beneficial in improving motor difficulties. An occupational therapist can help maximize fine motor difficulties. A speech pathologist could be healthful in providing training in speech and cognitive processes. Support groups and counseling may help MS patients, families and friends cope with the changing demands of the progressing disease including unemployment, high medical expenses and automobile/house modifications. There is no clinical evidence of benefits from dietary changes.

Case History

Patient presentation
A 34-year-old woman with auditory complaints secondary to MS was diagnosed with MS two years ago. At that time her complaints were an episode of diplopia accompanied by paresthesias (tingling sensation) and weakness in her left leg. The symptoms appeared to subside and a more severe exacerbation occurred one year later.

Family history
There is no familial history of hearing loss or MS.

Primary concerns and complaints
The patient has vague complaints of hearing difficulties, particularly in the presence of background noise.

Affected lifestyle (education, social emotional, etc.)
Patient is having difficulty understanding children in her classroom setting.

Auditory findings and outcome

Audiological workup and test findings
Immittance audiometry shows normal middle ear functioning, bilaterally. Type A tympanogram, normal static immittance, and normal right and left ipsilateral reflex thresholds were present. Contralateral reflexes were absent for both ears. Pure tone thresholds show a mild low-frequency sensorineural hearing loss bilaterally. SRTs match PTAs. Speech recognition is normal in quiet but abnormal when presented in the presence of noise. ABR for the left ear shows no waves were identifiable beyond component Wave I, and right ear ABR showed absolute latencies and interpeak intervals were significantly prolonged.

Vestibular test results
No vestibular test results reported.

Prognosis
There is no present cure for MS. Many patients survive for years following diagnosis. Patient education is very important in treatment. Outcome measures as MS Functional Composite will assess lower extremity, upper extremity, and cognitive function to help the physician monitor the disease progression. Studies have suggested that patients with few attacks in the first years after diagnosis, have long intervals between attacks, have complete recovery between attacks and have attacks that are sensory in nature (numbness) tend to do better. Patients with early symptoms of tremors, poor coordination, difficulty walking, or frequent attacks tend to do worse.

Medical Management

Imaging studies
MRI studies using gadolinium (a chemical contrast agent that normally does not cross the blood/brain barrier) is the best tool (T1) for diagnosis and monitoring. The contrasting allows detection of new lesions in the presence of older lesions over CT. MRI is more accurate for locating central plaques than peripheral. MRI flair and T2 sequences reveal plaque in middle and inferior peduncles.

Visual evoked potentials measuring electrical potentials of the optic nerve may be used to determine involvement and progression.    

Pharmaceutical treatments
Treatment focuses on relieving current symptoms. Some individuals find help from disease modifying drugs as Avonex, Betaferon, Capaxone, and Rebif. Exacerbations can be shortened or made less severe with a short course of corticosteroids. Glatiramer acetate and interferon betal, a or b, are injected daily or weekly.  Chemotherapy drugs have been used to reduce white blood cells (federally approved: Mitoxantrone, Azathioprine, Cladribine, Cyclophosphamide, Cyclosporine-A, and Methotrexant.

Surgical interventions
No surgical interventions were indicated.

Case Study Conclusions

This 34-year-old female diagnosed with MS two years prior was currently seen for auditory complaints in understanding speech in competing background noise. Immittance testing was consistent for a central pathway disorder of the lower brain stem (crossed reflexes absent bilaterally). SA was consistent with a retro-cochlear pathology (speech recognition normal in quiet but abnormal in the presence of competition, SSI). The patient and her referring physician were informed of the results and the patient was informed of assistive listening devices that could be used with the telephone and TV during periods of exacerbation.

Summary

MS is a degenerative autoimmune disease of the CNS. Current belief is that MS is an immunologic disturbance triggered by a virus in individuals who are genetically susceptible. Inflammation occurs in multiple areas of white matter of the CNS in random patches called plaques and results in demyelination.

Hearing loss is associated with lesions of the brainstem and VIII C.N. or at other sites along the auditory pathway. MS has an onset in early adulthood between 20-40 years with a ratio favoring Caucasians and women. MS is five times more prevalent in temperate climates. Types of MS include benign, malignant, relapsing-remitting, secondary- progressive, primary-progressive, and progressive-relapsing. Visual disturbances may occur early. Fatigue, spasticity, and weakness in extremities following exertion or warm temperatures are common.  MS patients experience mild cognitive difficulties as concentration, attention, memory, and poor judgment. Other common symptoms include balance problems, dizziness, faintness, unsteadiness, spatial disorientation, and vertigo. Depression and mood changes, bladder and bowel control, and sexual problems are common. 94% normal hearing acuity is found. Up to 40% with normal audiograms report difficulty hearing in background noise. Immittance testing is usually normal except for contralateral reflexes.  Speech discrimination may be poorer than indicated by pure tone thresholds particularly with competing noise. ABR testing is very useful in diagnosing MS as results frequently show abnormalities. MRI studies are used for diagnosis and monitoring. Balance problems are frequent. Rehabilitation training including physical therapy, occupational therapy, speech therapy, support groups and counseling may help. There is no present cure for MS. Treatment focuses on relieving current symptoms. Some individuals find help from disease modifying drugs, a short course of corticosteroids, or chemotherapy.

Bibliography

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Nodder, D, Chappell, B., Bates, D., Freeman. J., Hatch, J., Keen, J., Thomas, S., & Young, C. (2000), Multiple sclerosis: Care needs for 2000 and beyond, Journal of Sociology, 93 (5), 219-224.

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