Expert's comment concerning Grand Rounds case entitled "Subarachnoidal pleural fistula after resection of intradural thoracic disc herniation and multimodal treatment with noninvasive positive pressure ventilation (NPPV)" (H. R. Schlag, S. Muquit, T. B. Hristov, G. Morassi, B. M. Boszczyk, M. Shafafy)