Corpus Callosum-Mediated Interhemispheric Interactions in Cervical Spondylotic Myelopathy.

PURPOSE: The corpus callosum is crucial for interhemispheric interactions in the motor control of limb functions. Human and animal studies suggested spinal cord pathologies may induce cortical reorganization in sensorimotor areas. We investigate participation of the corpus callosum in executions of a simple motor task in patients with cervical spondylotic myelopathy (CSM) using transcranial magnetic stimulation. METHODS: Twenty patients with CSM with various MRI grades of severity of cord compression were compared with 19 normal controls. Ipsilateral silent period, contralateral silent period, central motor conduction time, and transcallosal conduction time (TCT) were determined. RESULTS: In both upper and lower limbs, TCTs were significantly increased for patients with CSM than normal controls ( p < 0.001 for all), without side-to-side differences. Ipsilateral silent period and contralateral silent period durations were significantly increased bilaterally for upper limbs in comparison to controls ( p < 0.01 for all), without side-to-side differences. There were no significant correlations of TCT with central motor conduction time nor severity of CSM for both upper and lower limbs ( p > 0.05 for all) bilaterally. CONCLUSIONS: Previous transcranial magnetic stimulation studies show increased motor cortex excitability in CSM; hence, increased TCTs observed bilaterally may be a compensatory mechanism for effective unidirectional and uniplanar execution of muscle activation in the distal limb muscles. Lack of correlation of TCTs with severity of CSM or central motor conduction time may be in keeping with a preexistent role of the corpus callosum as a predominantly inhibitory pathway for counteracting redundant movements resulting from increased motor cortex excitability occurring after spinal cord lesions.

Utility of Sensory Nerve Conduction Study in Radiologically Positive Lumbosacral Plexopathy.

MRI is the most appropriate imaging method for visual evaluation of lumbosacral plexopathy (LSP) and a reference for comparing with nerve conduction study (NCS). Eight patients with clinical, electrophysiological, and lumbosacral plexus MRI findings suggestive of LSP were prospectively recruited. Saphenous nerve abnormalities were present in seven patients (88%), compared to three for the superficial fibular (38%), and three for the sural nerve (38%). MRI showed tumor, hematoma, abscess, contrast enhancement, or hyperintense signals on the T2-weighted sequences. The SN has the highest yield in MRI positive LSP and may be a vital adjunct for electrophysiological evaluation of LSP.