Reykjavik, 13th of July 2017
by Neurophysiology Plus
To avoid a new neurological deficit after a brain growing tumor surgery located in or near eloquent brain areas (speech, motor, visual cortex) the surgeon uses now intraoperative neuromonitoring complementary procedures performed together with clinical neurophysiology team in the operating room.
In 1998, Sawaya et al published the tumor functional grade classification after a scheme developed at the Anderson Cancer Center in Houston Texas based on the tumor location relative to the brain function as following: Grade I non-eloquent brain: Frontal or temporal polar regions, Right parieto-occipital regions, Cerebellar hemispheres lesions; Grade II near eloquent brain: Near motor or sensory cortex, Near calcarine fissure, Near speech center, Corpus callosum, Near dentate nucleus, Near brainstem, including supplementary motor area if was investigated with preoperative magnetic resonance; Grade III eloquent brain: Motor/Sensory cortex, Visual center, Speech center, Internal capsule, Basal ganglia, Hypothalamus/thalamus, Brainstem, Dentate nucleus.
The preoperative studies used to identify the structure and the "function" of the eloquent brain are MRI, fMRI, CT, DatScan, SPECT, PET, TMS. From all these TMS-EMG and TMS-EEG modalities are used for motor mapping and speech mapping or EEG temporal related evoked potentials. The results, the identified motor hot-spots or speech area are then saved and used in operating room by neurosurgeon.
Neuro-Navigated TMS preoperative mapping using same operating room system
13th of July 2017
If eloquent brain areas and motor cortex hot-spots with Talairach coordinates are already set on the patient MRI (structural model of the brain) before surgery the neurophysiology and neurosurgery team will use them when proposing the surgery and during the resection of tumors or abnormal (non-functional) tissues.
In Iceland, preoperative motor mapping started in January 2017 (here) and recently a team formed by Ingvar Hakón Ólafsson, Aron Björnsson, Ágúst H. Guðmundsson (Intermedica/Medtronic), David B., Aron Dalin Jónasson and Ovidiu C. Banea could prove the combination of operating room neuronavigation system (Medtronic) with TMS motor mapping and Intraoperative device (Nim Eclipse Medtronic).
The pilot study was successful and was performed in surgery room. In close future the preoperative neuro-navigated mapping will be used for the proposed patients before surgery time.