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Neuroscience

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Biomedical Science

Abstract

Background: Recent research has suggested that after a spinal cord injury (SCI), detrimental reorganization of neural structures favors stronger muscles while inhibiting weaker muscles. Temporary deafferentation (TD) is a technique that uses short-term anesthesia, to inactivate sensation pathways from stronger muscles so that the brain releases inhibition that was placed on weaker muscles, thereby strengthening them. Here, we seek to evaluate when peak TD is achieved to define when strength-building exercises on a weaker muscle should begin.

Methods: 5% lidocaine cream was applied to the right biceps of 7 healthy volunteers. We measured sensation every 15 minutes after applying the cream using von Frey monofilaments of different thicknesses. Sensation was assessed for 75 minutes. Percent sensitivity was assessed across time.

Results: We found that at 45 minutes after the application of the short-term anesthesia, at least 50% of the monofilaments had less than 50% sensitivity. Our results suggest that 45 minutes is required to achieve maximum temporary deafferentation after lidocaine cream application. Hence, our protocol could be used in patients with a spinal cord injury to improve triceps function since TD reduces output to the biceps.

Conclusions: Our results suggest that most sensation was significantly reduced 45 minutes after the application of the lidocaine cream. However, we found that the anesthetic effect varied in our subjects. Future research will evaluate how the arm size, gender, age, body fat percentage, BMI, and other factors influence the effect of short-term anesthesia.

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Background: Recent research has suggested that after a spinal cord injury (SCI), detrimental reorganization of neural structures favors stronger muscles while inhibiting weaker muscles. Temporary deafferentation (TD) is a technique that uses short-term anesthesia, to inactivate sensation pathways from stronger muscles so that the brain releases inhibition that was placed on weaker muscles, thereby strengthening them. Here, we seek to evaluate when peak TD is achieved to define when strength-building exercises on a weaker muscle should begin.

Methods: 5% lidocaine cream was applied to the right biceps of 7 healthy volunteers. We measured sensation every 15 minutes after applying the cream using von Frey monofilaments of different thicknesses. Sensation was assessed for 75 minutes. Percent sensitivity was assessed across time.

Results: We found that at 45 minutes after the application of the short-term anesthesia, at least 50% of the monofilaments had less than 50% sensitivity. Our results suggest that 45 minutes is required to achieve maximum temporary deafferentation after lidocaine cream application. Hence, our protocol could be used in patients with a spinal cord injury to improve triceps function since TD reduces output to the biceps.

Conclusions: Our results suggest that most sensation was significantly reduced 45 minutes after the application of the lidocaine cream. However, we found that the anesthetic effect varied in our subjects. Future research will evaluate how the arm size, gender, age, body fat percentage, BMI, and other factors influence the effect of short-term anesthesia.

 

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