Brain tumors have been loosely divided between primary (occurring from the cells native to the CNS) and secondary or metastatic (from spread by direct contiguous contact or hematologic spread). The incidence of primary brain tumors in the USA is roughly 6.4 for every 100,000 people, with the majority comprising the glioblastoma subtype. Metastatic brain tumors occur in 15–20% of all cancer patients with the primary etiology being lung, breast, melanoma, and renal tumors. With the development of new imaging techniques, innovative surgical techniques, and progressive adjunctive therapies, the treatment of brain tumors now involves earlier diagnosis, improved accuracy for surgery, and more medical and radiation options for patients with brain tumors. Despite improved imaging techniques that can better describe the characteristics of brain tumors without tissue evaluation, the role of craniotomy surgery is an important component of both diagnosis and treatment of patients with brain tumors. As opposed to formal craniotomy, stereotactic needle biopsy can be used for those patients with tumor in a deep, functionally important region of the brain and in patients with poor systemic health. Histologic examination of these core needle biopsies is then used to direct therapy. Craniotomy and surgical debulking/excision are especially beneficial in those patients with large lesions that are symptomatic due to size and edema that cause compression of surrounding brain tissue.

Preoperative imaging for brain tumors is technically specific to each individual patient. With expert interpretation, surgical planning can be made with a general understanding of the goal of the procedure. Imaging techniques have progressed to include digital subtraction angiography, MRI, MR spectroscopy and functional MRI, to name a few. These techniques provide valuable information, but are frequently unable to exclude all other non-tumorous lesions like infarction, infection, and multiple sclerosis. Thus a craniotomy or needle biopsy is required to obtain definitive diagnosis.