Technical and clinical aspects of topographic brain mapping

TBM provides physiological and diagnostic information which is quite complementary to EEG, but does not replace the need for standard EEG recordings. For example, it does not show subtle morphologic abnormalities such as FIRDA, PLEDs or epileptiform discharges. Simultaneous EEG recording as well as impeccable technique are essential in proper recording of TBM, particularly as it can generate new forms of artifact. By prolonging the averaging time to over 180 seconds, and by application of flexible montages, a more accurate and cleaner record with less artifact can be obtained. Certain phenomena such as "centrifugal effect" and "comet effect" are examples of new problems generated by the advent of TBM. On the other hand, TBM can demonstrate subtle asymmetries, lateralization and localization effects more efficiently than a standard EEG. TBM is quite helpful clinically, when recording is done properly from a technical standpoint, in the diagnosis of post-traumatic syndrome and post-traumatic seizure disorder. It demonstrates subtle focal and lateralized asymmetries in cerebral hemispheric frequency bands in such patients. This information helps differentiate neurologic complications from psychiatric disorders. TBM plays a useful role in the differentiation and management of various other disorders, including depression, behavioral disturbances and dementias.