Localization of macroscopically undetectable intramedullary hematoma by intraoperative epidural motor evoked potential.

Introduction: Intramedullary hematoma is an uncommon, serious neurological disease, representing a diagnostic challenge. The preferred treatment is surgical. In most of the cases the lesion can be identified macroscopically. Otherwise, finding the optimal place to perform myelotomy is demanding. Intraoperative neurophysiological monitoring plays an important role in preventing surgical complications, but its versatility for localization has not been studied so far. Case report: The present case report describes a 17-year-old patient with flaccid right inferior monoparesis (later paraparesis), ipsilateral loss of proprioception and vibration sense, contralateral analgesia below the T10 dermatome level and urinary retention (Brown-Séquard syndrome). The MRI revealed an intramedullary hematoma at the level of T8-T9 vertebral bodies. Digital subtraction angiography did not identify any vascular malformation. Urgent surgical intervention was performed. In order to prevent any complication somatosensory-evoked potential (SSEP), transcranial and epidural motor-evoked potential (tcMEP, eMEP) recordings were planned. SSEP in response to right tibial nerve stimulation and tcMEP were absent bilaterally. From electrophysiological point of view, the eMEP revealed a total conduction block of the corticospinal tract. In the absence of typical macroscopic signs (discoloration, swelling, abnormal vascularization etc.), the small intramedullary hematoma could not be identified. Therefore, it was decided to adopt eMEP technique for mapping and localizing the conduction block intraoperatively by changing the distance between the two electrodes used for recording. The hematoma was precisely localized and successfully evacuated. Postoperatively, a slow but continuous improvement was noted. Conclusion: Intraoperative neurophysiological monitoring has been suggested to play crucial role in spinal cord surgery. To our knowledge, this is the first case report using eMEP recording for guiding and localizing of an intramedullary hematoma. Beside the clear limitations of our study, it could result in a novel application of the aforementioned monitoring technique.