Surface electromyography activity in the upper limbs of patients following surgery for compressive cervical
Ananth P Abraham, S Balaji Srinivas, Muthukumar Murthy
1Divisions of Neurosurgery, Department of Neurological Sciences, Christian Medical College, Vellore, Tamil Nadu, India.
Background:
Surface electromyography (EMG) is a noninvasive, accurate method to measure electrical activity produced in muscles.
Aim:
To assess the improvement of spasticity after decompressive surgery for compressive myelopathy using surface EMG.
Setting And Design:
Neurophysiology laboratory of a tertiary care center. Before-after trial. Both EMG and Modified Modified Ashworth Scale (MMAS) were utilized.
Materials And Methods:
Thirty-one nonconsecutive patients (28 males; age 25-72 years) with compressive cervical myelopathy and spasticity (MMAS score ≥1) were recruited. Patients with lower motor neuron findings, Nurick grade 5, and those with joint deformities, contractures, or thrombophlebitis of the upper limbs were excluded. EMG activity was measured from the pronator teres and biceps brachii for 31 age-related controls (25 males) as well as for the patients both pre- and post-operatively.
Statistical Analysis:
Student's t-test for comparison of continuous variables and Pearson correlation co-efficient for assessing the significance of associations.
Results:
EMG recording done 1-week postoperatively showed a reduction in baseline activity in the pronators and supinators by 21% and 36%, respectively. There was a decrease in co-activation of the pronators during active supination by almost 62% and of the supinators during active pronation by around 33% (P < 0.05). On passive movement, there was a decrease in co-activation of the pronators during supination by approximately 23%, and the supinators during pronation by 35% (P < 0.05). EMG activity was significantly reduced in the pronators during supination in all patients, including those in whom the MMAS scores remained the same postoperatively.
Conclusion:
Surface EMG is an objective tool to detect improvement in spasticity following decompressive surgery for compressive cervical myelopathy even in those patients who showed no improvement on the MMAS.
