Transcranial magnetic stimulation study of expiratory muscle weakness in acute ischemic stroke

Background: Expiratory muscle weakness due to cerebral infarction may contribute to reduced airway clearance in stroke patients. Methods: Transcranial magnetic stimulation (TMS) at the vertex and over each hemisphere and magnetic stimulation over the T10-11 spinal roots (Tw T-10) and the phrenic nerves bilaterally BAMPS) were performed in 15 acute ischemic stroke patients (age 68.9 +/- 9.8 years) and 16 matched controls. Surface electrodes recorded motor evoked potentials (MEPs) in the rectus abdominis (RA) and external oblique (EO) muscles bilaterally. Respiratory muscle function was assessed by measuring maximum static expiratory pressure (PEmax) and changes in intragastric (P gas) and transdiaphragmatic (P-di) pressure after voluntary cough, TMS, TwT(10), and BAMPS. Regression models were used to assess determinants of peak voluntary cough flow rates (PCFR). Results: PCFR, cough P gas, and vertex TMS P gas were decreased in stroke patients compared with controls (203.6 +/- 151.1 vs 350.8 +/- 111.7 L/min, p = 0.004; 72.7 +/- 64.5 vs 163.4 +/- 55.8 cm H2O, p = 0.0003 and 8.7 +/- 3.3 vs 16.7 +/- 11.5 cm H2O, p = 0.023, respectively). There were no differences in TwT(10) P gas (25.2 +/- 7.8 vs 29.4 +/- 12.4 cm H2O, p = 0.153) or BAMPS P-di (21.6 +/- 7.2 vs 19.2 +/- 3.4 cm H2O, p = 0.163). TMS P gas was lower (4.1 +/- 2.8 vs 6.1 +/- 1.9 cm H2O, p = 0.023) following TMS of the injured compared with the uninjured hemisphere in stroke patients. Age and gender adjusted PCFR correlated with P gas (r = 0.51, p = 0.009) and PE max (r = 0.46, p = 0.024). Stroke was an independent determinant of PCFR after adjusting for P gas and PE max (p = 0.031). Conclusion: Ischemic cortical injury is associated with expiratory muscle weakness and may contribute to cough impairment in stroke patients. Neurology (R) 2008;71:2000-2007