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Cervical Epidural Stimulation Elicits Evoked Potentials and Modulates Diaphragm EMG
Author(s) -
Dale Erica,
Gad Parag,
Zhong Hui,
Roy Roland,
Edgerton V Reggie
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.656.4
Subject(s) - stimulation , medicine , anesthesia , spinal cord , diaphragm (acoustics) , lumbar , anatomy , physics , psychiatry , acoustics , loudspeaker
Approximately 2/3 of traumatic spinal injuries occur at the cervical level leading to severe respiratory dysfunction. There are currently few clinical interventions for recovery from complete ventilator dependence after spinal cord injury. Our lab has shown that the spinal circuitry involved in locomotion can be stimulated via epidural stimulation by modulating the excitability of the lumbar spinal circuitry and enabling complex motor tasks after complete paralysis. We hypothesized that cervical epidural stimulation could modulate excitability of phrenic motor circuitry (and, thus, breathing) in much the same way. In this study, adult, female, Sprague‐Dawley rats (n=2) were implanted with bilateral cervical (C4, an area within the phrenic motor pool) epidural stimulating electrodes and bilateral diaphragm recording electrodes. Under isoflurane anesthesia, one rat was stimulated at C4 with varying intensities, frequencies, and polarities. With increasing voltage (1‐8V), amplitude of spinal evoked potentials (SEP) increased accordingly. Ten SEPs were averaged in each voltage range from 1‐8V. Right to left bilateral stimulation elicited SEPs from 0.41± 0.002mV to 2.3±0.001mV (LDia) and 0±0.0001mV‐2.0±0.001mV (RDia); left to right: 1.50±0.001mV‐4.32±0.003mV (LDia) and 0.70±0.0001mV‐2.12±0.002mV (RDia); right to ground: 0.45±0.0002mV‐2.0±0.001mV (LDia) and 1.0±0.001mV‐3.9±0.002mV (RDia); left to ground: 0.82±0.001mV‐2.4±0.002mV (LDia) and 0.18±0.0002mV‐3.0±0.003mV (RDia). Latencies ranged from 2.9‐3.1ms. In other experiments, an unanesthetized rat was given the same epidural cervical stimulation but via current‐based stimulation parameters (400‐1000uA). Right to left stimulation elicited SEPs from 2.1±0.003mV‐5.8±0.004mV (LDia); left to right: 4.0±0.003mV‐6.8±0.004mV (LDia); right to ground: 1.9±0.002mV‐6.7±0.004mV (LDia); left to ground: 1.9±0.002mV‐2.8±0.002mV (LDia). Latencies ranged from 2.9‐3.3ms. LDia EMG amplitude increased by 23.37±3.2% of baseline value (vs ‐2.0±1.3% by RDia) at 8V, right to left stimulation, 1Hz indicating at least a short term modulation of phrenic motor networks. These data demonstrate that cervical epidural stimulation at the phrenic motor pool elicits activation of diaphragmatic motor units. This short‐term modulation of the phrenic motor network offers great therapeutic potential for patients who are ventilator‐dependent after spinal cord injury. Further study is required to determine if long‐term stimulation can lead to plasticity of these highly plastic motor networks. Supported by U01EB015521 and T32 NS058280.