Ken-ichi Nagamatsu

Neuromagnetic localization of N15, the initial cortical response to lip stimulus.

The initial cortical response of the trigeminal somatosensory evoked magnetic fields was measured for electrical stimulation of the lower lip in eleven subjects. The stimulus frequency was 0.7 Hz and stimulus intensity was nine times sensory threshold. The initial contralateral response was detected in 20 hemispheres at a latency of 14.6 ± 1.3 ms and was named N15m. The equivalent current dipole of N15m was localized at the posterior bank of the central sulcus with anterior–superior orientation, and inferior to the dipole of N20m for median nerve stimulation.

Surgical Implications of Neuromagnetic Spike Localization in Temporal Lobe Epilepsy

Summary:  Purpose: To investigate the clinical usefulness of magnetoencephalography (MEG) as a guide to the surgical treatment of temporal lobe epilepsy (TLE).

Remote discharges in the posterior language area during basal temporal stimulation.

A 23-year-old woman with refractory complex partial seizures underwent implantation of subdural grid electrodes over the left hemisphere to map epileptic foci and language function. Aphasic symptoms occurred during stimulation of the basal temporal area, which were always associated with intrastimulus remote discharges (ISRDs) in the classical posterior language area. No sequential language deficits occurred after anterior temporal lobectomy including the basal temporal area. These results suggest a close functional relationship between the basal temporal area and posterior language area in patients with temporal lobe epilepsy. ISRDs may explain the paradoxical observation that resection of the basal temporal language area results in no language deficits.

Regression of recurrent glioblastoma infiltrating the brainstem after convection-enhanced delivery of nimustine hydrochloride

This 13-year-old boy with a history of cranial irradiation for the CNS recurrence of acute lymphocytic leukemia developed a glioblastoma in the right cerebellum. Resection and chemo- and radiotherapy induced remission of the disease. However, recurrence was noted in the brainstem region 8 months later. Because no effective treatment was available for this recurrent lesion, the authors decided to use convection-enhanced delivery (CED) to infuse nimustine hydrochloride. On stereotactic insertion of the infusion cannula into the brainstem lesion, CED of nimustine hydrochloride was performed with real-time MR imaging to monitor the co-infused chelated gadolinium. The patients preinfusion symptom of diplopia disappeared after treatment. Follow-up MR imaging revealed the response of the tumor. The authors report on a case of recurrent glioblastoma infiltrating the brainstem that regressed after CED of nimustine hydrochloride.

Use of microscope-integrated near-infrared indocyanine green videoangiography in the surgical treatment of intramedullary cavernous malformations: report of 8 cases.

OBJECT The characteristics and efficacy of indocyanine green (ICG) videoangiography in cavernous malformation (CM) have not been fully elucidated. The purpose of this paper is to examine the potential utility of ICG videoangiography in the surgical treatment of intramedullary CMs. METHODS The authors conducted a retrospective review of 8 cases involving 5 men and 3 women who had undergone surgery for intramedullary CM between January 2008 and July 2011. All patients were evaluated by means of MRI. The MRI findings and clinical history in all cases suggested intramedullary CM as a preoperative diagnosis. In 2 of 8 cases, dilated venous structures associated with CMs were demonstrated. In one of these cases, there were coexisting extramedullary CMs. Intraoperatively, ICG fluorescence was observed for 5 minutes using microscope-integrated videoangiography. RESULTS In all 8 cases, intra- and extramedullary CMs were seen as avascular areas on ICG videoangiography. Indocyanine green videoangiography helped surgeons to localize and predict margins of the lesions before performing myelotomy. Importantly, in the cases with associated venous anomalies, ICG videoangiography was useful in delineating and preserving the venous structures. In extramedullary CMs located dorsal to the spinal cord, gradual ICG infiltration was seen, starting at 110 seconds and maximal at 210 seconds after injection. Postoperative MRI confirmed total removal of the lesions in all cases, and subsequent recovery of all patients was uneventful. CONCLUSIONS Indocyanine green videoangiography provided useful information with regard to the detection of lesion margins by demonstrating intramedullary CMs as avascular areas. In cases associated with venous anomalies, ICG contributed to safe and complete removal of the CMs by visualizing the venous structure. In extramedullary CMs, ICG videoangiography demonstrated the characteristic of slow blood flow within CMs.

Neuromagnetic separation of secondarily bilateral synchronized spike foci: report of three cases

To demonstrate the high spatiotemporal resolution of magnetoencephalography (MEG), we report three cases with focal epilepsy that exhibited bilateral synchronized spikes on simultaneous scalp EEG and MEG recording. Constant time lags (19.4 +/- 3.0 ms and 20.0 +/- 5.5) between the leading and the following contralateral spikes were noted on MEG and the current dipole sources were localized in the bilateral homotopic regions symmetrically in Cases 1 and 3. In Case 2, MEG indicated leading spikes in the left frontal region, with a time lag of 42.3 +/- 8.4 ms to reach the contralateral frontal and bilateral temporal regions as well. Chronic subdural EEG recording in Cases 1 and 2 confirmed that the leading spike focus in MEG was close to the seizure onset zone in cortical EEG. Spatio-temporal analysis of MEG spikes may be useful to identify the primary epileptic region in patients with synchronized bilateral epileptiform discharges.

5-aminolevulinic acid fluorescence-guided resection of intramedullary ependymoma: report of 9 cases.

BACKGROUND: Resection guided by 5-aminolevulinic acid (5-ALA) fluorescence has proved to be useful in intracranial glioma surgery. However, the effects of 5-ALA on spinal cord tumors remain unknown. OBJECTIVE: To evaluate the usefulness of 5-ALA fluorescence-guided resection of intramedullary ependymoma for achieving maximum tumor resection. METHODS: This study included 10 patients who underwent surgical resection of an intramedullary ependymoma. Nine patients were orally administered 5-ALA (20 mg/kg) 2 hours before the induction of anesthesia. 5-ALA fluorescence was visualized with an operating microscope. Tumors were removed in a standardized manner with electrophysiological monitoring. The extent of resection was evaluated on the basis of intraoperative findings and postoperative magnetic resonance imaging. Histopathological diagnosis was established according to World Health Organization 2007 criteria. Cell proliferation was assessed by Ki-67 labeling index. RESULTS: 5-ALA fluorescence was positive in 7 patients (6 grade II and 1 grade III) and negative in 2 patients (grade II). Intraoperative findings were dichotomized: Tumors covered by the cyst were easily separated from the normal parenchyma, whereas tumors without the cyst appeared to be continuous to the spinal cord. In these cases, 5-ALA fluorescence was especially valuable in delineating the ventral and cranial and caudal margins. Ki-67 labeling index was significantly higher in 5-ALA-positive cases compared with 5-ALA-negative cases. All patients improved neurologically or stabilized after surgery. CONCLUSION: 5-ALA fluorescence was useful for detecting tumor margins during surgery for intramedullary ependymoma. When combined with electrophysiological monitoring, fluorescence-guided resection could help to achieve maximum tumor resection safely. ABBREVIATIONS: 5-ALA, 5-aminolevulinic acid LI, labeling index MEP, motor evoked potential

Somatosensory evoked fields in comatose survivors after severe traumatic brain injury

OBJECTIVE To evaluate the cortical function quantitatively in patients in the chronic phase of severe traumatic brain injury. METHODS Thirteen patients with severe traumatic brain injury due to traffic accident followed by persistent consciousness disturbance and disability were studied. Somatosensory evoked magnetic fields (SEFs) for unilateral median nerve stimulation were measured using a whole-head magnetoencephalography system. The latency and electrical current dipole (ECD) moment for the N20m, P30m, N45m and P60m components were calculated and compared with those of 14 age-matched healthy adults. RESULTS The peak latency of N20m was longer (P<0.05) and those of P30m and N45m were shorter (P<0.01) in the patients than in normal adults. The ECD moment of N20m and P30m was smaller and that of N45m and P60m was larger in the patients than in normal adults (P<0.01). CONCLUSIONS These results can be explained by the hypothesis that diffuse brain injury induces decreased and delayed input of the somatosensory afferent and compensational amplification of the response in the primary somatosensory cortex. Middle-latency SEFs may be applicable as a cortical functional measure for patients with severe traumatic brain injury.

Intraoperative localisation of the lip sensory area by somatosensory evoked potentials

Accurate localisation of the central sulcus enables maximum tumour resection with minimum morbidity in peri-Rolandic surgery. We investigated intraoperative somatosensory evoked potentials (SSEPs) with combined recording of lower lip and median nerve stimuli during craniotomy in nine patients with peri-Rolandic glioma. Using a custom clip electrode, the lip mucous membrane was stimulated with biphasic pulses with 0.2 ms duration, 10-14 mA intensity and a frequency of 0.7 Hz. Polarity inversion of the SSEP was detected across the central sulcus using median nerve and/or lower lip stimulation in eight of the nine patients in whom the tumour did not infiltrate the lip or hand sensory area. Recording of SSEPs with lower lip stimulation is useful if the resection margin is planned lateral to the hand representation area, if the hand representation area is not exposed by the craniotomy, or if the SSEPs for median nerve stimulation are not clear due to tumour infiltration.