Assessment of the motor pathway to the diaphragm using cortical and cervical magnetic stimulation in the decision-making process of phrenic pacing.
BACKGROUND
Phrenic nerve pacing is a recognized substitute to positive pressure ventilation via tracheotomy in patients with high cervical cord lesions or central hypoventilation. Although its indications are infrequent, reliable strategies need to be used in the determinations of patients who may benefit from this treatment; contraindications should be carefully respected.


OBJECTIVE
To determine whether modern and noninvasive means to study the motor pathway to the diaphragm, namely cortical magnetic stimulation (CxMS) and cervical magnetic stimulation (CMS), can contribute to the selection of patients who may benefit from phrenic pacing.


METHODS
Prospective study (18 months), on a consecutive basis, of patients referred for possible phrenic pacing to a 10-bed ICU associated with a respiratory neurophysiology laboratory.


METHODS
Seven patients (high cervical cord injury, n = 5; central hypoventilation following neurosurgery, n = 1; idiopathic acquired central hypoventilation, n = 1). INTERVENTION, MEASUREMENTS, AND RESULTS: Electromyography of the diaphragm and transdiaphragmatic pressure were assessed in response to CxMS and CMS. In three cases, no interruption of the corticodiaphragmatic pathway was evidenced, the decision of pacing was postponed, and the patients eventually recovered a spontaneous breathing activity. In two cases, the diagnosis of irreversible peripheral phrenic dysfunction was reached and pacing was denied. In two cases, complete interruption of the corticodiaphragmatic pathway and integrity of peripheral conduction led to the decision of phrenic pacemaker implantation.


CONCLUSIONS
CxMS and CMS can be used to refine the assessment of patients proposed for phrenic pacing. CxMS can possibly identify those in whom there is a possibility for eventual recovery, and therefore substantiate a decision to postpone the pacing.
Similowski
T
T
Unité de Réanimation, Groupe Hospitalier Pitié-Salpêtrière, Paris, France.
Straus
C
C
Attali
V
V
Duguet
A
A
Jourdain
B
B
Derenne
J P
JP
D000293:Adolescent; D000328:Adult; D000368:Aged; D002540:Cerebral Cortex; D003964:Diaphragm / Q000294:innervation* / Q000503:physiopathology; D004599:Electric Stimulation Therapy; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008280:Magnetics / Q000627:therapeutic use*; D008297:Male; D009333:Neck; D009434:Neural Pathways; D010791:Phrenic Nerve / Q000502:physiology*; D011446:Prospective Studies; D012133:Respiratory Paralysis / Q000503:physiopathology / Q000628:therapy*