ntraoperative neurophysiology is a rapidly growing ﬁeld of clinical neurophysiology. Its signiﬁcant development over the last two decades stems from the positive impact it has had on postoperative neurologic outcome in a wide range of surgeries. The oldest neurophysiologic techniques used intraoperatively have been EEG and somatosensory evoked potentials to continuously assess the function of cerebral hemispheres and of large ﬁber sensory system, respectively. Over the years, other neurophysiologic tests, such as motor evoked responses, brainstem auditory evoked responses, and free electromyogram, were added to the neurophysiologist’s toolbox for functional monitoring of other parts of neuroaxis such as the motor and auditory systems, motor roots, and nerves. Hence, the name of intraoperative (neuro) monitoring. Without doubt, neuromonitoring procedures have been the bulk of neurophysiologic testing in the OR. However, many have argued that neuromonitoring picks up functional disturbances too late, when damage has already occurred. Thus, identifying functionally eloquent structures in advance makes a lot of sense. Neurophysiologic mapping adds new dimensions to ﬁeld of intraoperative (neuro) monitoring. Although it cannot replace the utility of continuous monitoring, it offers the possibility of delineating functionally eloquent nervous tissue before hand and, thus, protects it during surgery. In my view, neurophysiologic mapping is in many situations more challenging technically and interpretatively than neuromonitoring. Unlike neuromonitoring, which in general relies on stimulation and recording from standard locations (e.g., stimulation of median nerve at the wrist and recording from scalp channels), mapping often involves stimulation of and/or recording from multiple regions, diverse and unexpected locations, and from histologically unknown tissue. In addition, these locations can be distorted and, thus, functionally disabled, by the presence of local pathology. More so, unlike neuromonitoring, which relies on interpreting changes from the patient’s own baseline, in mapping, interpretation of recorded responses is rarely straightforward. The latter is more likely to be inﬂuenced by interindividual variability, possible disrupted neurophysiologic–neuronatomic correlation, and technically challenging recordings, which in general are signiﬁcantly noisier than during standard neuromonitoring procedures. This issue of JCN is dedicated to intraoperative neurophysiologic mapping of different parts of the neuroaxis. Each article is meant to bring a useful review on the subject of interest, while adding the authors’ own experience in the matter, and thus hopefully constituting a practical and succint presentation on each mapping technique and of their applications. Dr. Fernandez and Dr. Loddenkemper give a comprehensive overview of the use of direct cortical EEG recordings as a unique tool to map seizure foci in epilepsy surgery. They address both chronic, extraoperative recordings via implanted hardware and intraoperative recordings. The tables and pictures are particularly illustrative and helpful. Two articles are dedicated to supratentorial functional mapping. Regarding sensorimotor mapping, I have tried to share my experience on the subject, while placing it in a historical perspective and offering many visual examples, with the hope that the ﬁnal result can serve anyone with a broad interest in this topic. Dr. Kilbride wrote about language mapping, about his expertise in the ﬁeld. His details on methodology, troubleshooting, and patient’s testing offer great tips. The examples given underline the utility of cortical EEG recordings in language mapping. Dr. Karakis gives a useful overview of the literature on brainstem mapping, methodology, challenges, and indications. Dr. Gonzalez continues with a clear and complete presentation of the sensory and motor mapping techniques of the spinal cord, exempliﬁed by pictures. Dr. Nair offers a nice overview of neurophysiologic mapping of the peripheral nervous system; the pictures on anatomy are particularly useful in understanding the principles of these techniques. In the end, we hope this issue will become an easily accessible and yet comprehensive reference on neurophysiologic mapping procedures used along the neuraxis, from the cerebral hemispheres to peripheral nerves.
Mirela Simon From the Massachusetts General Hospital, Boston, Massachusetts, U.S.A. Copyright Ó 2013 by the American Clinical Neurophysiology Society
Copyright Ó 2013 by the American Clinical Neurophysiology Society