Recurrent Profound Hypercapnea and Respiratory Arrest - A Mystery Solved

Abstract

INTRODUCTION: Limbic encephalitis (LE) is a paraneoplastic process involving temporo-limbic structures of brain. Usually, LE presents with behavioral changes, short-term memory problems, seizures and cognitive dysfunction. Central hypoventilation has been reported in some patients with LE but we report a patient who had profound hypercapnea and respiratory arrest. CASE PRESENTATION: A 65-year-old woman was admitted from floor to MICU after intubation for respiratory arrest. Six months ago, she had behavioral changes with short-term memory problems and was found to have LE on MRI of brain. LE being a paraneoplastic syndrome, comprehensive work up was done, which revealed mediastinal mass with high SUV uptake on PET Scan, proven to be a neuroendocrine tumor on biopsy. Her ABG revealed profound hypercapnea with pCO2 of 142 mm Hg. Her CBC, BMP, ammonia, CSF analysis, EEG, chest x-ray and CT head were normal. No etiology of her hypoventilation and respiratory arrest was found. She was successfully extubated 2 days later and was transferred to floor. Next day, she was intubated again for another episode of profound hypercapneic respiratory arrest with pCO2 of 150. Considering her history of LE, a literature search was done revealing central hypoventilation in these patients. A repeat brain MRI revealed worsening of LE, which did not respond to previous trials of intravenous steroids, immunoglobulins, plasmapheresis and chemoradiation. She self extubated herself the next day, following which she was transferred to floor on non invasive positive pressure ventilation (BIPAP). She had no further episodes while on intermittent BIPAP during 3-month follow up. DISCUSSION: Paraneoplastic LE can be associated with any malignancy, however 50% will have small cell lung cancer. Somnolence and central hypoventilation is seen in approximately 30% of patients with LE but profound hypercapnea with respiratory arrest is rare. Paraneoplastic autoantibodies are positive in 65% but diagnosis is made by characteristic MRI findings as described in our case[1][2]. Specific antineoplastic treatment may result in improvement of LE. Other therapies like corticosteroids, intravenous immunoglobulin's, plasmapheresis and rituximab have been tried with varied response [3]. CONCLUSIONS: Early identification and use of noninvasive ventilation in LE patients with hypercapnea may prevent respiratory arrest needing mechanical ventilation.