Quantitative electrodiagnostic patterns of damage and recovery after spinal cord injury: a pilot study

Study design Prospective observational pilot study. Objectives To compare quantitative electromyographic (EMG), imaging and strength data at two time points in individuals with cervical spinal cord injury (SCI). Setting SCI center, Veterans Affairs Health Care System, Palo Alto, California, USA. Methods Subjects without suspected peripheral nerve injury were recruited within 3 months of injury. Needle EMG examination was performed in myotomes above, at, and below the SCI level around 11- and 12-months post injury. EMG data were decomposed using custom software into constituent motor unit trains and each distinct motor unit was analyzed for firing rate and amplitude. Strength measurements were made with dynamometry and according to the International Standard of Neurologic Classification of SCI (ISNCSCI). Cervical magnetic resonance images (MRI) were evaluated by two neuroradiologists for gray and white matter damage around the SCI. Here, we compare the EMG, strength, and imaging findings of the one of the four participants who completed both 3- and 12-month EMG evaluations. Results There was an increase in force generation in all muscles tested at 1 year. Localized findings of very fast firing motor units helped localize spinal cord damage and revealed gray matter damage in spinal segments where MRI was normal. Meanwhile, improvement in strength over time corresponded with different electrophysiologic patterns. Conclusions Electromyographic decomposition at two time points provides valuable information about localization of spinal cord damage, integrity of motor neuron pools and may provide a unique understanding of neural recovery mechanisms.