Evaluating patients with non-malignant brain tumors begins with a detailed history. The majority of patients lack symptoms even if there is mass effect. The most common presenting symptoms for patients with low-grade gliomas are seizures (72 %), headaches (30 %), language (7 %), and sensorimotor (32 %) changes [115]. Common presenting symptoms for meningioma patients are seizures (45 %), headaches (34–41 %), dizziness (29.3 %), tinnitus (14.6 %), syncope (9.8 %), memory disturbance (4.9 %), visual disturbance (4.9 %), and trigeminal neuralgia (2.4 %) [51, 68]. Classically, headaches tend to be worse upon waking in the morning and may be severe enough to wake one from sleep. It is not uncommon for tumor-related headaches to initially be misdiagnosed as sinus, tension, or migraine headaches. Headaches related to obstructive hydrocephalus are relatively rare in non-malignant brain tumors; however, this does require urgent neurosurgical evaluation.

Seizures are the most common presenting symptom, occurring in 72–80 % of patients with low-grade gliomas and 45 % of meningioma patients [51, 115]. Seizure control is important for maintaining optimum quality of life. The use of anticonvulsant medications such as levetiracetam, lacosamide, topiramate, or phenytoin in brain tumor patients is somewhat controversial. Patients presenting with seizures should be started on anticonvulsant therapy. However, there is little data to suggest prophylactic use of anticonvulsants to reduce the risk of new-onset seizures in patients with low-grade gliomas or meningiomas [58]. Even so, it is common practice to offer perioperative anticonvulsant medications to patients with large tumors involving highly epileptogenic areas. Gross total resection is the strongest predictor of seizure freedom [30, 88]. Radiotherapy and chemotherapeutic agents such as temozolomide and alkylating agents are also effective in reducing seizure frequency in patients with tumor-associated medication-resistant epilepsy [88].

The majority of people with non-malignant brain tumors have a normal neurological examination. Physical findings, when evident, are variable depending on tumor location, size, and scope of disease. Papilledema (swelling of the head of the optic nerve associated with engorgement of retinal veins) and oculomotor palsy are due to tumor mass effect and elevated intracranial pressure. Aphasia suggests involvement of cortical or subcortical language centers of the dominant frontal, temporal, or parietal lobes. Focal motor weakness can be caused by tumor invasion of the corticospinal pathway or peritumoral edema, which may be reversible with the administration of corticosteroids. The diagnosis of brain tumor should always be considered in patients who develop a new psychiatric condition.

Non-malignant brain tumors with no clinical symptoms have a different natural history from those that are symptomatic. Incidental low-grade gliomas tend to occur more frequently in females, have smaller tumor volumes, and improved patient outcomes [77, 80]. Incidental low-grade gliomas are more likely to undergo gross total resection; however, if untreated, they demonstrate consistent radiographic growth eventually leading to symptoms over a median of 4 years [76, 77]. Incidental meningiomas fall into one of three growth patterns: no growth, steady linear growth, or exponential growth [68]. For this reason some advocate serial imaging and a brief observation period, reserving surgical intervention for patients with symptomatic lesions, documented tumor growth over time, or imaging suspicious for other pathologic lesions that mimic meningiomas [16].

Due to its wide availability, speed, and affordability, non-contrast computed tomography (CT) is commonly the initial imaging modality for symptomatic patients with non-malignant brain tumors. Brain magnetic resonance imaging (MRI) with and without gadolinium contrast is the definitive imaging modality to assess tumor location, size, cellularity, associated cystic components, associated edema or hemorrhage, necrosis, margins and invasion into surrounding structures, vascularity, and enhancement. Radiographically, low-grade gliomas are isodense or hypodense when compared to brain tissue on CT scan and do not enhance with contrast administration. Calcifications are common in oligodendrogliomas. On MRI, low-grade gliomas are isointense to hypointense on T1-weighted imaging, hyperintense on T2-weighted imaging, and are not contrast-enhancing (Fig. 1.3). Meningiomas are hyperintense compared to brain tissue and have a broad dural attachment. On T2-weighted MRI, most meningiomas are hyperintense and are typically contrast-enhancing on both CT and MRI (Fig. 1.4). Radiographic imaging provides information about tumor localization, proximity to functional areas, mass effect, and associated edema [35]. Functional MRI and diffusion tensor imaging (DTI) shows the integrity of white matter tracts and can be used to create an operative corridor or plan for resection that minimizes risk to eloquent surrounding structures (Fig. 1.5). Metabolic MRI or magnetic resonance spectroscopy can be used to supplement information obtained from traditional morphologic MRI, particularly for differentiating radiation necrosis and residual tumor. Cerebral angiography is used preoperatively to illustrate and embolize the vascular supply to meningiomas and hemangiomas (Fig. 1.4c).

Maximum safe surgical resection is the best option to relieve symptoms, improve functional outcome, and boost long-term survival. Decisions regarding surgical approach require careful consideration of a number of key factors including: tumor size, proximity to presumed functional areas, imaging characteristics, and patient age, health, and functional status. The value of surgical resection for low-grade gliomas has been validated by a number of studies illustrating a survival benefit of 60–90 months with maximal resection [14, 38, 47, 91, 99, 105]. While some advocate initial tumor biopsy followed by watchful waiting for low-grade gliomas, several studies have suggested that this is not the best choice for long-term survival. In a large population-based series of Norwegian patients, early maximal resection was superior to biopsy and watchful waiting with respective 5-year survival rates of 74 and 60 % [47]. Furthermore, maximal resection has also been shown to delay malignant transformation with improved survival and less malignant transformation seen in patients receiving greater than 90 % extent of resection [105]. Tumor-associated epilepsy is also better managed after gross total resection [30, 114]. A small meningioma with no documented growth in an asymptomatic patient can be considered for observation [35]. This however must be balanced with the known fact that younger age at diagnosis and greater extent of resection are strong predictors of improved outcome for meningioma patients [65, 95].

The central goal of brain tumor surgery is maximizing the removal of neoplastic tissue while minimizing collateral damage to functional areas and vascular structures [29]. The timing of surgery is important in preoperative planning. The majority of patients with non-malignant brain tumors can be scheduled for elective surgery. However, patients who present with rapid deterioration due to elevated intracranial pressure or obstructive hydrocephalus require prompt intervention. For low-grade gliomas, the goal is to safely remove as much tumor as possible, as visualized by T2/FLAIR signal. The goal for meningioma resection is to remove both the tumor and its dural origin. A variety of technologies have been developed to improve surgical outcomes. Stereotactic navigation (also known as neuronavigation) is utilized to precisely localize tumor location and tailor focused craniotomies, but there is little evidence that it can improve extent of resection. Intraoperative MRI, an approach in which brain tumor resection is performed in a highly specialized surgical suite containing MRI, is another technique used to improve identification of residual tumor [59, 63, 71, 98]. The use of direct stimulation mapping to identify functional pathways is the gold standard for preserving language and sensorimotor function. Individual patient variability and pathway distortion by mass lesions makes localization of functional sites difficult by any other means [5, 18, 28, 40, 54, 72–74, 92, 102] (Fig. 1.6). Numerous studies have failed to predict the specific location of language sites using anatomical locations and functional neuroimaging (DTI and functional MRI) [1, 21, 31, 41, 60, 67, 83, 101, 110]. Using specialized neuroanesthesia, awake brain tumor surgery has proven both safe and effective, with an acceptable morbidity and mortality compared with asleep procedures [6, 22, 34, 55, 56, 89, 92, 94, 109].

Following brain tumor surgery, patients are commonly observed closely in an intensive care setting with hemodynamic and neurological monitoring. Corticosteroid medications are tapered and anticonvulsants continued in patients who have a seizure history. Given the prognostic significance of extent of resection, it is standard practice for many surgeons to obtain an early postoperative MRI to evaluate for residual tumor.

Although surgical resection is the foundation of brain tumor therapy, it is incapable of eliminating every tumor cell. Adjuvant radiation and chemotherapeutic regimens have been developed to treat remaining tumor cells.