According to researchers at University of Colorado School of Medicine there is a strong association between Meniere's disease and conditions involving temporary low blood flow in the brain such as migraine headaches.
Foster explains that these attacks can be caused by a combination of two factors: 1) a malformation of the inner ear, endolymphatic hydrops (the inner ear dilated with fluid) and 2) risk factors for vascular disease in the brain, such as migraine, sleep apnea, smoking and atherosclerosis.
The researchers propose that a fluid buildup in part of the inner ear, which is strongly associated with Meniere's attacks, indicates the presence of a pressure-regulation problem that acts to cause mild, intermittent decreases of blood flow within the ear. When this is combined with vascular diseases that also lower blood flow to the brain and ear, sudden loss of blood flow similar to transient ischemic attacks (or mini strokes) in the brain can be generated in the inner ear sensory tissues. In young people who have hydrops without vascular disorders, no attacks occur because blood flow continues in spite of these fluctuations. However, in people with vascular diseases, these fluctuations are sufficient to rob the ear of blood flow and the nutrients the blood provides. When the tissues that sense hearing and motion are starved of blood, they stop sending signals to the brain, which sets off the vertigo, tinnitus and hearing loss in the disorder.
Restoration of blood flow does not resolve the problem. Scientists believe it triggers a damaging after-effect called the ischemia-reperfusion pathway in the excitable tissues of the ear that silences the ear for several hours, resulting in the prolonged severe vertigo and hearing loss that is characteristic of the disorder. Although most of the tissues recover, each spell results in small areas of damage that over time results in permanent loss of both hearing and balance function in the ear.
Since the first linkage of endolymphatic hydrops and Meniere's disease in 1938, a variety of mechanisms have been proposed to explain the attacks and the progressive deafness, but no answer has explained all aspects of the disorder, and no treatment based on these theories has proven capable of controlling the progression of the disease. This new theory, if proven, would provide many new avenues of treatment for this previously poorly-controlled disorder.
The researchers propose that a fluid buildup in part of the inner ear, which is strongly associated with Meniere's attacks, indicates the presence of a pressure-regulation problem that acts to cause mild, intermittent decreases of blood flow within the ear. When this is combined with vascular diseases that also lower blood flow to the brain and ear, sudden loss of blood flow similar to transient ischemic attacks (or mini strokes) in the brain can be generated in the inner ear sensory tissues. In young people who have hydrops without vascular disorders, no attacks occur because blood flow continues in spite of these fluctuations. However, in people with vascular diseases, these fluctuations are sufficient to rob the ear of blood flow and the nutrients the blood provides. When the tissues that sense hearing and motion are starved of blood, they stop sending signals to the brain, which sets off the vertigo, tinnitus and hearing loss in the disorder.
Restoration of blood flow does not resolve the problem. Scientists believe it triggers a damaging after-effect called the ischemia-reperfusion pathway in the excitable tissues of the ear that silences the ear for several hours, resulting in the prolonged severe vertigo and hearing loss that is characteristic of the disorder. Although most of the tissues recover, each spell results in small areas of damage that over time results in permanent loss of both hearing and balance function in the ear.
Since the first linkage of endolymphatic hydrops and Meniere's disease in 1938, a variety of mechanisms have been proposed to explain the attacks and the progressive deafness, but no answer has explained all aspects of the disorder, and no treatment based on these theories has proven capable of controlling the progression of the disease. This new theory, if proven, would provide many new avenues of treatment for this previously poorly-controlled disorder.
Many disorders of the inner hear which affect both hearing and balance can be hugely debilitating and are currently largely incurable. Cochlear implants have been used for many years to replace lost hearing resulting from inner ear damage. However, to date, there has not been an analogous treatment for balance disorders resulting from inner ear disease. One potential new treatment is an implantable vestibular prosthesis which would directly activate the vestibular nerve by electrical stimulation.
Phillips and his colleagues have developed a vestibular prosthesis which delivers electrical stimulation to the fluid inside the semi-circular canals of the ear. In effect, the stimulation of the fluid makes the brain believe that the body is moving or swaying in a certain direction. This then causes a compensatory postural reflex to stabilize the posture thereby helping to restore balance.
This prosthesis was inserted into the ears of four subjects all suffering from long-term Meniere's disease and differing degrees of hearing loss which was resistant to other management strategies. The researchers found that electrical stimulation of the fluid in the semicircular canals of the affected ear did result in a change in posture, the direction of which was dependent on which ear was stimulated. However, each subject had different sway responses to the stimulation given. The authors believe this could be caused by small differences in the location of the electrode between subjects. Thus fine tuning and individual calibration for each electrode implant would be required for it to be effective. Overall the results illustrate that this type of prosthesis may eventually be a possible treatment for balance issues caused by Meniere's disease.
References:
Phillips and his colleagues have developed a vestibular prosthesis which delivers electrical stimulation to the fluid inside the semi-circular canals of the ear. In effect, the stimulation of the fluid makes the brain believe that the body is moving or swaying in a certain direction. This then causes a compensatory postural reflex to stabilize the posture thereby helping to restore balance.
This prosthesis was inserted into the ears of four subjects all suffering from long-term Meniere's disease and differing degrees of hearing loss which was resistant to other management strategies. The researchers found that electrical stimulation of the fluid in the semicircular canals of the affected ear did result in a change in posture, the direction of which was dependent on which ear was stimulated. However, each subject had different sway responses to the stimulation given. The authors believe this could be caused by small differences in the location of the electrode between subjects. Thus fine tuning and individual calibration for each electrode implant would be required for it to be effective. Overall the results illustrate that this type of prosthesis may eventually be a possible treatment for balance issues caused by Meniere's disease.
References:
- Carol Foster, MD and Robert Breeze, MD. The Meniere attack: An ischemia/reperfusion disorder of inner ear sensory tissues. Medical Hypotheses, December 2013
- Phillips, C. et al. Postural responses to electrical stimulation of the vestibular end organs in human subjects. Experimental Brain Research, 2013 DOI:10.1007/s00221-013-3604-3
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