Acute fulminant invasive fungal sinusitis in an immunocompromised host and bacterial rhinosinusitis with intracranial or orbital extension are challenging to manage and constitute true otolaryngic emergencies. In the absence of rapid diagnosis and treatment, these diseases can be fatal. In this article, the complications of bacterial rhinosinusitis are divided into three categories: local, orbital, and intracranial. They vary in their characteristics and severity according to their location, duration, and specific symptoms. This article reviews the pathophysiology, clinical presentation, diagnosis, and treatment options of acute invasive fungal sinusitis rhinosinusitis, the most common subtype in the United States.