Isolated sphenoid sinusitis is a rare, potentially destructive entity. Presenting symptoms are often vague and non-specific therefore the diagnosis is made late when complications have had already occurred. The most frequent complications of sinusitis are the neurological ones--being serious life--threatening conditions. We report a case of isolate right sphenoid sinusitis with concurrent thrombophlebitis of left cavernous sinus. Accordingly, we review the salient clinical features of this illness, with emphasis on the importance of a high index of suspicion, the potentially rapid and fatal course of the disease process and the aspects of the diagnosis and treatment. We also reviewed the predisposing factors of complications of sphenoid sinusitis.