What is Meniere's Disease?
Meniere’s Disease is a type of endolymphatic hydrops that affects both the hearing and vestibular organs of the inner ear. Meniere’s Disease is characterized by an abnormal build up of endolymph resulting in episodes of excessive intracochlear pressure. Over time, these episodes of excessive pressure damage the sensory organs of the cochlea. The exact etiology of Meniere’s Disease is unknown. There are many hypotheses for the cause of Meniere’s Disease, but no consensus.
Meniere's Disease Symptomology:
Meniere’s Disease has two stages: active and latent. During the active stage of Meniere’s Disease, patients will experience episodes of severe vertigo, nausea and vomiting that is prefaced by roaring tinnitus, fluctuating hearing loss, and/or aural fullness. Episodes can last for hours. During the latent stage of Meniere’s Disease, patients no longer experience episodes of symptomology because the sensory tissues of the cochlea have been destroyed. During the latent stage of Meniere’s Disease, patients often experience permanent hearing loss. Patient may experience imbalance and dizziness until the brain can compensate for the resultant unilateral vestibular weakness.
Meniere's Disease Testing:
On the audiogram, low frequency or fluctuating sensorineural hearing loss may be revealed during the active stage of Meniere’s Disease. Flat sensorineural hearing loss across the frequency range may be revealed during the latent stage of Meniere’s Disease.
Electrocochleography is the gold standard test to determine if a patient in fact has endolymphatic hydrops (ELH) or Meniere's Disease. This is a neurophysiologic test that utilizes surface electrodes on the head and scalp along with auditory cues in the form of click stimuli to measure the fluid levels of the inner ear. It is important to note that the patient does NOT need to be symptomatic for the test to be conclusive. Four metrics are taken into account for diagnosis of ELH: 1) SP/AP area ratio 2) SP/AP amplitude ratio 3) interaural latency and 4) the ability for the waveform to return to baseline. In a person with Meniere's Disease or ELH, you will see and elevated SP/AP area ratio (greater than 2), increased SP/AP amplitude ratio, an interaural difference greater than 0.2 in the affected ear (if binaural ELH this will not apply) and an inability to return to baseline.
Unilateral vestibular weakness, resultant from Meniere’s Disease, may be revealed during caloric testing, an integral part of videonsytagmography (VNG). During caloric testing, the vestibular system is stimulated by “irrigating” both ears with warm and cool air. When warm air is used to irrigate the ear, endolymph within the horizontal canal becomes lighter and flows upward. When cool air is used to irrigate the ear, endolymph in the horizontal semicircular canal becomes heavier and flows downward. This flow of endolymph results in the patient feeling as if his/her head moving. When a patient experiences this spinning sensation, or vertigo, the eyes reflexively move in a specific pattern called nystagmus. It is normal to experience vertigo and nystagmus during caloric testing. The intensity of the nystagmus is measured to determine the strength of the vestibular response at each ear. A unilateral vestibular weakness is revealed when one ear’s response is weaker than expected.
vHIT assesses the integrity of the vestibulo-ocular reflex (VOR) relative to each semicircular canal. For more information regarding the VOR and its relationship with the semicircular canals please refer to the vestibular anatomy section. During vHIT, the patient wears goggles that are used to measure eye movements. The provider instructs patient to keep eyes focused on a visual target and then moves the patient’s head in short, quick motions. The measurement of eye movement is then compared to head movement. In a patient with normal VOR function, eye movement should be equal but opposite of head movement, allowing the patient’s eyes to stay focused on the visual target despite head movement. In a patient with impaired VOR function, patient’s eyes will lose focus on visual target when head is moved. Meniere’s Disease can result in impaired VOR function related to the side of unilateral weakness.
Meniere's Disease Management:
Due to a lack of consensus regarding the cause of Meniere’s Disease, there is also a lack of consensus regarding the treatment of Meniere’s Disease. Lifestyle changes such as reduced intake of salt, caffeine and alcohol are suggested to aid in the management of Meniere’s Disease. Diuretics, antihistamines or anti-inflammatory medications may be prescribed. More invasive intervention, such as VIIIth cranial nerve sectioning, may be considered for patients who suffer from debilitating vertiginous episodes. During the latent stage of Meniere’s Disease, vestibular rehabilitation therapy can aid in the brain’s compensation for resultant unilateral vestibular weakness. Refer to this link for more information regarding vestibular rehabilitation therapy: http://www.fyzicalbalance.com/our-approach/howdoesitwork . Amplification can be used to treat resultant unilateral hearing loss.