Predicting the recovery of ventilatory activity in central respiratory paralysis

Objective: To assess the value of the diaphragmatic response to transcranial magnetic stimulation (TMS) in predicting the recovery of ventilatory activity after CNS lesions responsible for central respiratory paralysis. Methods: The authors studied 11 long-term ventilator-dependent patients with central respiratory paralysis (description group: spinal trauma 10, medullary ischemia 1) and 16 patients with central respiratory paralysis for less than 10 weeks (prognostic group, evaluated after a 1-year follow-up: spinal trauma 8, medullary ischemia 4, radiation myelitis 1, subdural hematoma 1, complication of neurosurgery 2). Results: In the description group, all the patients had a bilaterally abolished diaphragm response. In the prognostic group, six patients were fully ventilator dependent because of a complete absence of ventilatory activity at follow-up time. They lacked any diaphragm response. The 10 other patients had recovered ventilatory activity and full (n = 9) or partial (n = 1) ventilatory autonomy. In nine cases, diaphragm response was present at least on one side, with a normal latency (right: 15.6 +/- 1.5 milliseconds; left: 16.2 +/- 2.2 milliseconds). The test had 100% specificity (95% CI 52 to 100) and 90% sensitivity (95% CI 54 to 99) to predict the recovery of ventilatory activity. Conclusion: Electrophysiologic studies of the diaphragm in response to transcranial magnetic stimulation may help predict the recovery of central respiratory paralysis within 1 year.