Keiko Oda

Motor evoked potential monitoring of the vagus nerve with transcranial electrical stimulation during skull base surgeries

OBJECT Dysphasia is one of the most serious complications of skull base surgeries and results from damage to the brainstem and/or cranial nerves involved in swallowing. Here, the authors propose a method to monitor the function of the vagus nerve using endotracheal tube surface electrodes and transcranial electrical stimulation during skull base surgeries. METHODS Fifteen patients with skull base or brainstem tumors were enrolled. The authors used surface electrodes of an endotracheal tube to record compound electromyographic responses from the vocalis muscle. Motor neurons were stimulated using corkscrew electrodes placed subdermally on the scalp at C3 and C4. During surgery, the operator received a warning when the amplitude of the vagal motor evoked potential (MEP) decreased to less than 50% of the control level. After surgery, swallowing function was assessed clinically using grading criteria. RESULTS In 5 patients, vagal MEP amplitude permanently deteriorated to less than 50% of the control level on the right side when meningiomas were dissected from the pons or basilar artery, or when a schwannoma was dissected from the vagal rootlets. These 5 patients had postoperative dysphagia. At 4 weeks after surgery, 2 patients still had dysphagia. In 2 patients, vagal MEPs of one side transiently disappeared when the tumors were dissected from the brainstem or the vagal rootlets. After surgery, both patients had dysphagia, which recovered in 4 weeks. In 7 patients, MEP amplitude was consistent, maintaining more than 50% of the control level throughout the operative procedures. After surgery all 7 patients were neurologically intact with normal swallowing function. CONCLUSIONS Vagal MEP monitoring with transcranial electrical stimulation and endotracheal tube electrode recording was a safe and effective method to provide continuous real-time information on the integrity of both the supranuclear and infranuclear vagal pathway. This method is useful to prevent intraoperative injury of the brainstem corticobulbar tract or the vagal rootlets and to avoid the postoperative dysphagia that is often associated with brainstem or skull base surgeries.

OUTCOME OF CLIVAL CHORDOMAS AFTER SKULL BASE SURGERIES WITH MEAN FOLLOW-UP OF 10 YEARS

BACKGROUND AND OBJECTIVE Skull base chordomas are clinically malignant because of the difficulty of total removal, high recurrence rate, and occasional drop metastasis. Although aggressive surgical resection and postoperative radiation have been recommended, the long-term outcome remains unsatisfactory. METHODS From 1992 to 2011, we treated 24 patients with skull base chordoma using aggressive surgical removal as a principal strategy. Skull base approaches were selected according to tumor extension to remove the tumor and surrounding bone as completely as possible. After surgery, all patients were closely observed with MRI to find small and localized recurrent tumors, which were treated with gamma-knife radiosurgery or surgical resection. The mean postoperative follow-up duration was 10.2 years (range, 1-17.2 years). RESULTS The 5-, 10-, and 15-year overall survival rates were 86%, 72%, and 72%, respectively. The 5- and 10-year progression-free survival rates were 47% and 35%, respectively. Tumor extension to the brainstem and partial tumor removal were the factors related to poor survival. CONCLUSIONS Our results suggest that aggressive surgical removal improves the long-term outcome of patients with skull base chordoma. We would like to emphasize that skull base chordomas should be aggressively removed using various skull base approaches.

Intracranial hemorrhage and platelet transfusion after administration of anti-platelets agents: Fukushima Prefecture.

We conducted a case series study to assess intracerebral hemorrhage (ICH) in the context of anti-platelets agents (APAs) and platelet (PLT) transfusion in Fukushima Prefecture.This study included patients who were newly diagnosed with ICH between January 2008 and June 2014 in the neurosurgical hospitals of Fukushima Prefecture.　Four of ten neurosurgical hospitals responded to our questionnaire.　Of 287 ICH patients, 51 (20.6%) were on APA therapy, of whom PLT transfusion was given to only one persistently bleeding patient who was on dual anti-platelet therapy.　In a follow-up survey, 30 out of 51 ICH patients on APA therapy, average age 75 years, were analyzed, of whom 21 (70%) were male.　The predominant underlying disease was diabetes mellitus.　It is interesting to note that peripheral artery disease and aortic aneurysm were among the indications for APAs.　ICH was mainly observed supratentorially.　Hematoma enlargement was observed in 13 (44.8%) cases.　By day 7, 3 patients (10%) had died from complications of ICH.　In this study, we show that ICH during APA therapy matched what was observed in Kanagawa Prefecture.　Whether or not a national survey differs, we anticipate greater statistical validity and an opportunity to improve patient outcomes in Japan and around the world.

Skull base invasive low-grade meningiomas, a distinct genetic subgroup: A microarray gene expression profile analysis.

Introduction Meningioma is the most common adult primary brain tumor originating from meningeal coverings of the brain and spinal cord. Commonly, World Health Organization (WHO) grade-I meningiomas are slowly growing and surgically curative, some present with clinically aggressive behavior, invading the skull base bone and soft tissues by extending into the extracranial spaces. Methods To detect the genetic background of the Skull Base Invasive Low-grade Meningioma (SBILM), we conducted a comprehensive analysis of gene expression was conducted on 32 meningioma samples. Results The cluster analysis of the gene expression profile demonstrated a distinctive clustering pattern of the SBILM. Based on the clinical behavior and the microarray findings, they might be a distinct subgroup of meningiomas. Conclusion Further studies on characterization of genes specifically expressed by the SBILM could lead to the development of diagnostic tools, differentiating it from other WHO grade-I meningiomas and assist in the appropriate management and follow-up strategy, and open the door for development of pharmacological therapies.

Usefulness of three-dimensional computed tomography to quantify the subarachnoid hemorrhage volume: prediction of symptomatic vasospasm.

We quantified the subarachnoid hemorrhage (SAH) volume in 64 patients on three-dimensional computed tomography (3D-CT) scans and studied the correlation between the SAH volume and the occurrence of symptomatic vasospasm (SVS). We studied 64 patients with SAH onset (day 0) and on days 1, 4, 7, and 14. We compared the hematoma volume by 3D-CT with 2D-CT on day 0 and examined the correlation between the hematoma volume and the occurrence of SVS. The hematoma volume, including the volume of normal structures, was automatically calculated (V1). The volume of normal structures manifesting identical CT numbers was previously calculated in patients without intracranial lesions (V2). The total hematoma volume was defined as V1 minus mean value of V2 (= 12 ml). The mean hematoma volume by 3D-CT was 48 ± 12 ml and by 2D-CT was 31 ± 45 ml (mean ± SD, n = 64). The hematoma volume was significantly larger by 3D-CT than by 2D-CT (p < 0.05). At all time points, the hematoma volumes were significantly larger in patients with than without SVS. We developed a new method for the quantitative determination of the SAH volume by 3D-CT. This method may allow us to quantify the volume of SAH in clinical studies of cerebral vasospasm.