Under evaluation: vagus nerve stimulation against tinnitus

Battling hearing loss is a topic that I sadly neglected in 2010. I aim to correct this by sharing at least 1 post per mo nth this topic.

Let us start 2011 with a short report on tinnitus, a poorly understood condition characterized by a persistent noise in the ear. It usually “comes in the form of a high-pitched tone in one or both ears, but can also sound like a clicking, roaring or whooshing sound.”

Millions of people of suffering from some form of tinnitus. Unfortunately, there is currently no cure for tinnitus. Therapies to ease the symptoms include reducing the persistent sound or simply learning to ignore it. However, studies indicate that tinnitus adversely affect quality of life.

“…it is known to be a sign that something is wrong in the auditory system: the ear, the auditory nerve that connects the inner ear to the brain, or the parts of the brain that process sound. Something as simple as a piece of earwax blocking the ear canal can cause tinnitus, but it can also arise from a number of health conditions. For example, when sensory cells in the inner ear are damaged from loud noise, the resulting hearing loss changes some of the signals in the brain to cause tinnitus.”

Conditions associated with tinnitus include “allergies, high or low blood pressure, tumors and problems in the heart, blood vessels, jaw and neck.”

A research study led by Dr. Michael Kilgard at the University of Texas at Dallas and Dr. Navzer Engineer at MicroTransponder, Inc indicates that tinnitus is not only in the auditory system but in the brain itself. The research team tried to find a means to reverse tinnitus by essentially “resetting” the brain’s auditory system. They did this by electrical stimulation of the vagus nerve (VNS) of lab rats using a tone. Through VNS, they could induce release of chemicals responsible for changes in the brain using different tone frequencies. By monitoring the neural responses in the rat’s brain auditory cortex during the test, they could determine that VNS plus tone stimulation restored responses to normal level – an indication of the absence of tinnitus. They were also able to demonstrate that VNS could reverse tinnitus even in noise-exposed animals.

“The key is that, unlike previous treatments, we’re not masking the tinnitus, we’re not hiding the tinnitus. We are retuning the brain from a state where it generates tinnitus to a state that does not generate tinnitus. We are eliminating the source of the tinnitus.”

This technique has a great potential in brining relief to tinnitus patients. Testing the method in humans is being planned.

This is not the first clinical application of the of VNS. The technique is already used in treating depression and epilepsy.
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