[Application of shot-latency cortical somato-sensory evoked potentials for evaluation of swallowing disorders in early period after posterior fossa surgery].

ABSTRACT

UNLABELLED Main tasks of early postoperative period in patients after posterior fossa surgery are the timely and safe weaning from mechanical ventilation and extubation. For clinical assessment of the hypopharynx function we use an algorithm developed in the intensive care unit (ICU) of the Burdenko Scientific Research Institute of Neurosurgery. Disadvantages of the clinical test for assessment of patient's readiness for extubation are subjectivity and impossibility to use it in conditions of even superficial sedation. Shot-latency somato-sensory evoked potentials (SSEP) can be applied in conditions of sedation and objectify the brain stem deficit. The goal of the study was to define the changes of cortical SSEP in patients with disorders of swallowing after posterior fossa surgery. To assess the swallowing disorders we used a scale of swallowing disorders in intubated patients with brain stem damage. We compared results of cortical SSEP, test of swallowing disorders in intubated patients and clinical results of extubation. 17 patients with tumors of posterior fossa were included in the study. All patients were divided into two groups depending on duration of mechanical ventilation. Patients of the group-1 were successfully extubated in 4.5 hours. Patients of the group-2 were mechanically ventilated more than 15 hours because of impossibility to pass the test of readiness for extubation. RESULTS: Central conduction time symmetry index after the surgery was lower in the group-1 than in group-2. There was inverse correlation between amplitude of cortical response N20 and time from the patient's admission to the ICU until the moment of extubation. CONCLUSIONS: Asymmetry of central conduction time and decreasing of N20 amplitude can be used as additional predictor of swallowing disorder.