RESUMEN
The arachnoid cyst is a rare disease that accounts for about 1% of the intracranial mass. The etiology of arachnoid cyst is due to either congenital compromise of arachnoidal development or acquired inflammatory reaction or trauma in the subarachnoid space. Computed tomography of arachnoid cyst demonstrates well-marginated low density lesions, whereas magnetic resonance image shows identical signal intensities of cerebrospinal fluid on T1 and T2 weighted image and low signal intensity on diffuse weight imaging without contrast-enhancement. The treatment of intracavernous sinus arachnoid cyst must be tailored to each patient according to the location of the lesion within cavernous sinus and the patient's symptoms. We experienced a case of arachnoid cyst of the cavernous sinus accompanying mycotic sphenoidal sinusitis. There are no previously reported cases of patients with an intracavernous sinus arachnoid cyst accompanying mycotic sphenoidal sinusitis.