Acute neurologic crisis after bronchoscopic biopsy: Carcinoid-like presentation of pulmonary mucoepidermoid carcinoma.

Introduction: Bronchoscopic evaluation of endobronchial tumors rarely triggers systemic complications. While bronchial carcinoid tumors can precipitate carcinoid syndrome or crisis through serotonin release, classic carcinoid syndrome occurs in under 5% of bronchial carcinoids. We describe a patient who developed acute neurologic and autonomic crisis following bronchoscopy of an unknown endobronchial tumor, initially mimicking carcinoid crisis but ultimately attributed to cerebral air embolism with final pathology revealing pulmonary mucoepidermoid carcinoma. Case presentation: A 52-year-old nonsmoking female with recurrent pneumonia underwent bronchoscopy for an obstructive endobronchial lesion. Multiple biopsies and argon plasma coagulation were performed. Within 1-2 hours post-procedure, she developed acute agitation, fever (39.4 °C), facial flushing, tachycardia, and generalized seizure activity, requiring emergent intubation. Normal serum serotonin and 24-h urine 5-HIAA excluded carcinoid crisis. Bronchoscopic biopsy revealed low-grade mucoepidermoid carcinoma, confirmed by subsequent surgical resection showing a 2-cm well-circumscribed tumor without neuroendocrine features or lymph node involvement. The patient recovered fully within 24 hours without focal deficits. Discussion: Pulmonary mucoepidermoid carcinoma, comprising 0.2% of lung cancers, originates from submucosal glandular cells and does not secrete serotonin or other hormonal mediators. Unlike carcinoids, MECs are not associated with endocrine crises. The clinical presentation suggested cerebral air embolism-a rare bronchoscopic complication that can manifest with seizures, altered consciousness, and autonomic instability. No systemic mediator release from the MEC was identified. The patient underwent right lower lobectomy with complete resection and excellent prognosis (5-year survival ∼95% for low-grade MEC). Conclusion: Acute neurovascular collapse after bronchoscopy of a bronchial tumor is not always carcinoid crisis. Key clinical lessons include maintaining a broad differential for post-procedural flushing, fever, and neurologic dysfunction; obtaining biochemical testing before assuming carcinoid crisis; recognizing that salivary gland-type pulmonary MECs can mimic carcinoids endoscopically but lack serotonin production; and recalling that bronchoscopic air embolism, while rare, presents with sudden seizures and altered consciousness requiring early recognition and high-flow oxygen therapy.