44.4.4. Retention Effects

Residual balance effects also were observed in all tested BVD subjects; however, the strength and extent of effects significantly varied from subject to subject depending on the severity of vestibular damage, the time of subject recovery, and the length and intensity of EVSS training.

At least three groups of residual balance effects were noted: short-term residual effects (sustained for a few minutes), long-term residual effects (sustained for 1–12 hours), and a rehabilitation effect that we observed during several months of training in a single subject. All residual effects were observed after complete removal of EVSS from the subject’s mouth.

44.4.4.1. Short-Term Aftereffect

This effect was usually observed during the initial stages of EVSS training. Subjects were able to maintain their balance for some time, without immediately developing an abnormal sway. Moreover, the length of short-term aftereffects was almost linearly dependent on the time of EVSS exposure. After 100 seconds of EVSS exposure, stabilization continued for 30–35 seconds; after 200 seconds of EVSS exposure, for 65–70 seconds; and after 300 seconds, the subject was able to maintain balance for more than 100 seconds. The short-term aftereffect continued to be approximately 30%–50% of the EVSS exposure time (Tyler et al., 2003).

44.4.4.2. Long-Term Aftereffect

After longer (up to 40 minutes) sessions of EVSS training long-term aftereffects developed and were sustained for a several hours. The relative duration of the balance improvement was much longer than the observed short-term aftereffect. Instead of the expected 7 minutes of stability (if one were to linearly extrapolate the 30% rule based on 20-minute trials), we observed from 1 to 6 hours of improved stability (Danilov, 2004).

After 20 minutes of training, the BVD subjects were able to not only stand steadily with good alignment on a hard or soft surface, but were also able to accomplish completely different kinds of balance-challenging activities, such as walking on a beam, standing on one leg, and even riding a bicycle or dancing. After a few hours, however, all the symptoms returned, although frequently not as severe as before. We noted that the strength of the long-term aftereffects was also dependent on the time of EVSS exposure: 10-minute trials were much less effective than 20-minute trials, and 40-minute trials had about the same efficiency as 20 minutes. Consequently, we concluded that 20 minutes was sufficient for standing trials with closed eyes.

44.4.4.3. Rehabilitation Effect

We were capable of repeating two and sometimes three 20-minute EVSS trials with a single subject during 1 day. After the second trial, the effects continued about 6 hours on average (Figure 44.2). In total, after two 20-minute EVSS stabilization trials, BVD subjects reported feeling and behaving “normal” for up to 10–14 hours a day. Our conclusion was that consistent, consecutive training produced both systematic improvement and gradual increase in duration of the long-term aftereffect.

Figure 44.2

Long-term retention effect. (a) Head stabilogram of a subject with bilateral vestibular loss, standing with closed eyes test during 100 seconds. Subject could not stand in test position before stimulation. The head stabilograms were recorded every 0.5 (more...)

Moreover, we found that repetitive EVSS training produced both accumulated improvement in balance control, and global recovery of the central mechanisms of the vestibular system (Danilov, 2004). The improvement in most individuals’ balance continued even after the sensory substitution ceased. These subjects exhibited balance retention and functional transfer of postural stability to gait and other activities of daily living (Danilov et al., 2006, 2007).

We have tested more than 200 subjects with peripheral, central, or idiopathic vestibular loss, Parkinson disease, and other sensory-motor control impairments such as stroke and TBI, all with the primary symptom of moderate to severe balance dysfunction. The great majority of subjects showed significant short- and long-term functional improvement when scored by multiple standardized objective measures, regardless of etiology and age (Danilov et al., 2007).

Similar to our vision substitution technology, the portable version of the EVSS was commercialized as the BrainPort Balance device (Figure 44.1c). It received the CE mark and was tested in the United States, Europe, Canada, Brazil, and Russia, mainly reproducing our core results. (Badke et al., 2011; Barros et al., 2010; Bittar and Barros, 2011; Borisoff et al., 2010; Danilov et al., 2007; Robinson et al., 2009; Vuillerme and Cuisinier, 2008; Vuillerme et al., 2008). Unfortunately, Wicab, Inc., decided to postpone BrainPort Balance device development, instead focusing on the BrainPort Vision device, which received CE mark approval in 2013.

It was already becoming clear by 2005 that this technology was also effective with TBI subjects, where balance and gait problems are “secondary” to primary symptoms of brain damage. Our first experience in helping moderate and severe TBI subjects was very encouraging, as was the recovery of balance in people who had suffered a stroke, and functional improvement in people with spinal cord injuries (Badke et al., 2011; Borisoff et al., 2010). In addition to balance recovery effects, we found multiple effects directly or indirectly related to other areas, for example improvement of vision (oscillopsia, visual neglect, and eye movement control), cognitive function, tinnitus, headache, sleep, and mood.

44.4.5. CN-NINM Technology

After the initial successful application of our new portable BrainPort Balance Device system in central and peripheral vestibular affected subjects, it became obvious that we needed to reconsider our main scientific concept. Multiple independent and consistent results led us to believe that these long-lasting retention effects cannot be attributed to sensory substitution alone (translation of meaningful environmental information) because the signal is no longer present, but rather are induced by the mechanism of delivery—the patterned, high-frequency electrical stimulation of the lingual nerve and chorda tympani (Tyler et al., 2003). The source and driving force for neuroplasticity induced by our intervention is the electrotactile stimulation itself, delivered to the brain by two cranial nerves directly to the brainstem.

The new technology, CN-NINM, was born as direct implementation of that idea—noninvasive electrotactile stimulation of the tongue producing strong brain activation and exciting the self-rehabilitation processes. Our stimulation appears to facilitate the state of neuroplasticity simultaneously in many areas of the brain, improving many affected functions in parallel. We also recognized that combining stimulation with intensive rehabilitation therapy methods would enhance the stimulation effects.

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