EEG in Brain Tumors

A brain tumor is one of the scariest diagnoses a patient can hear. Until the past 4 decades, with advent of advanced imaging (CT scanning, MRI), localization of brain tumors and other focal lesions was difficult. Old neuroimaging techniques consisted of skull radiography, which was usually negative, and pneumoencephalograms, which were invasive, painful, and often uninformative.

Electroencephalograms (EEG) in man started in 1920s; in 1936, Walter, who introduced the term "delta waves," first identified the association between localized slow waves on EEG and tumors of the cerebral hemispheres. ^[1] Delta is the frequency of EEG that is under 4 Hertz (Hz) whereas the normal alpha is between 8-12 Hz. This established EEG as an important tool for localizing brain tumors. For the next 4 decades, electroencephalographers mounted an enormous effort to improve accuracy of localization and to seek clues to underlying pathological processes.

Experience has shown EEG to be somewhat reliable in localizing lesions involving superficial portions of the cerebral hemispheres, though it is of limited value in deep-seated lesions, especially posterior fossa tumors. The role of EEG in detecting focal cerebral disturbances has undergone a significant change since the development of CT scan and MRI.

Today, EEG is primarily used to complement these studies by evaluating functional changes in the patient's condition, especially in regards to seizures and epilepsy; it demonstrates aspects of brain physiology that are not reflected in structural neuroimaging. Functional neuroimaging techniques, such as positron emission tomography (PET), single-photon emission computed tomography (SPECT), and functional MRI (fMRI), can exhibit physiologic changes but not with the temporal resolution of EEG. Furthermore, EEG provides the only continuous measure of cerebral function over time and is the diagnostic test of choice regarding seizures and epilepsy which is common with brain tumors.

This article reviews the major EEG changes that occur with different brain tumors.

Brain TumorSymptoms:

Symptoms (signs) of benign brain tumors often are not specific. The following is a list of symptoms that, alone or combined, can be caused by benign brain tumors; unfortunately, these symptoms can occur in many other diseases:

• vision problems
• hearing problems
• balance problems
• changes in mental ability (for example, concentration, memory, speech)
• seizures, muscle jerking
• change in sense of smell
• nausea/vomiting
• facial paralysis
• headaches
• numbness in extremities