Yellow 560 Microscope for Intraoperative Visualization of Fluorescein Stained Intracranial Lesions

Inclusion Criteria: * Age 18 years or older. * Diagnosed by preoperative imaging modalities to have a brain tumor or vascular lesions (aneurysm, arteriovenous malformation or arteriovenous fistula) requiring surgical intervention. * The patient is determined by a board certified Neurosurgeon (above mentioned neurosurgeons) to benefit from the application of Fluorescein Sodium intraoperatively * Patient or legally authorized representative provides written informed consent to enroll in this study. Exclusion Criteria: * Known allergic reaction to Fluorescein Sodium. * Children. * Prisoners. * Students. * Infection of the central nervous system or other sites. * Hemodynamic instability or significant impairments in circulation. * Concomitant treatment with other investigational drugs. * Any uncontrolled condition unrelated to the neurosurgical disease. * History of psychiatric, additive, or any other disorder that compromises the ability to provide informed consent or comply with study protocols. * Participation on other clinical trials during the last thirty days. * Pregnant patients. * Patients unable to discontinue medications that affect Fluorescein metabolism.