DELAYED-ONSET DYSPNEA AND ABNORMAL FLOW-VOLUME LOOPS IN EPILEPSY PATIENTS BEING TREATED BY VAGUS NERVE STIMULATION
Abstract number :
2.426
Submission category :
Year :
2003
Submission ID :
1925
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Lauren Beslow, Ann Weinacker, Michael Risinger, Bonnie Pamiroyan, Mimi Callanan, Gary Heit, Robert Fisher Neurology, Stanford Medical Center, Stanford, CA; Medicine, Stanford Medical Center, Stanford, CA; Neurosurgery, Stanford Medical Center, Stanford, C
Dyspnea is a recognized complication of the vagus nerve stimulation (VNS) during the time of stimulation. We report three cases of delayed-onset dyspnea, with abnormal flow-volume loops.
Pulmonary function tests (PFTs) including flow-volume loops were obtained on three patients who complained of significant dyspnea. The patients were three women ages 31, 41 and 46, with partial and secondarily generalized seizures.
Dyspnea appeared 6, 49, and 5 months after initiation of stimulation and 3, 7, and 2 months following the last increase in stimulation parameters. Patient 1 had recurrent dyspnea for approximately15 minute periods, while patients 2 and 3 felt constant shortness of breath, with occasional exacerbations. Effects of exercise and position varied, but dyspnea was not linked to stimulation cycling. Stimulation intensity varied from 1.75 - 2.0 mA, on cycles of 30 seconds and off cycles of 1.1 - 5 minutes. FVC was mildly reduced in patient 1 and was normal in the other two. FEV1 was normal in all three patients. All three patients demonstrated abnormal flow-volume loops with decreased expiratory flow per second, a finding consistent with large airway partial obstruction. All reported resolution of their dyspnea immediately to fifteen minutes after reduction of stimulation parameters. Dyspnea symptoms were reproducible in all patients upon increasing the stimulation parameters.
Dyspnea can present as a delayed complication of vagus nerve stimulation, even when stimulation parameters have been stable for many months. The mechanism of dyspnea is unknown but flow-loop studies suggest that it might result from decreased inspiratory or expiratory flows.