Effects of propofol on cortico-cortical evoked potentials in the dorsal language white matter pathway.

OBJECTIVE: In order to evaluate the clinical utility even under general anesthesia, the present study aimed to clarify the effect of anesthesia on the cortico-cortical evoked potentials (CCEPs). METHODS: We analyzed 14 patients' data in monitoring the integrity of the dorsal language pathway by using CCEPs both under general anesthesia with propofol and remifentanil and awake condition, with the main aim of clarifying the effect of anesthesia on the distribution and waveform of CCEPs. RESULTS: The distribution of larger CCEP response sites, including the locus of the maximum CCEP response site, was marginally affected by anesthesia. With regard to similarity of waveforms, the mean waveform correlation coefficient indicated a strong agreement. CCEP N1 amplitude increased by an average of 25.8% from general anesthesia to waking, except three patients. CCEP N1 latencies had no correlation in changes between the two conditions. CONCLUSIONS: We demonstrated that the distribution of larger CCEP responses was marginally affected by anesthesia and that the CCEP N1 amplitude had tendency to increase from general anesthesia to the awake condition. SIGNIFICANCE: The CCEP method provides the efficiency of intraoperative monitoring for dorsal language white matter pathway even under general anesthesia.

Effects of a stable concentration of propofol on interictal high-frequency oscillations in drug-resistant epilepsy.

The aim of this study was to clarify the effect of a stable concentration of propofol on interictal high-frequency oscillations (HFOs), which may contribute to identifying the epileptogenic zone intraoperatively for resection surgery. Nine patients with drug-resistant focal epilepsy who underwent invasive pre-surgical evaluation with chronic subdural electrodes were recruited. Five-minute electrocorticograms during wakefulness, slow-wave sleep, and under a stable brain concentration of propofol were recorded with the same electrodes. In each patient, 1-10 pairs of electrodes were selected for both electrodes with EEG changes within 5 seconds from the ictal onset (ictal pattern for 5 seconds [IP5]) and those outside the area of IP5 with no interictal epileptiform discharges (non-epileptiform [nEPI]). The numbers of ripples (80-250 Hz) and fast ripples (>250 Hz) were measured semi-automatically using an established algorithm. Statistical testing was performed with a mixed effect model. Thirty-seven pairs of electrodes from nine patients were analysed for IP5 and 29 pairs from seven patients were analysed for nEPI. The numbers of HFOs differed between the areas (IP5 and nEPI) and among the conditions (wakefulness, slow-wave sleep, propofol anaesthesia) (all p <0.01). The HFO occurrence rates were significantly higher for IP5 than those for nEPI in all conditions (for both ripples and fast ripples in all conditions; p <0.01). The occurrence rates of HFOs for IP5 were significantly higher than those for nEPI under propofol anaesthesia. These are fundamental findings for intraoperative HFO analysis, however, the following limitations should be considered: physiological HFOs could not be completely differentiated from pathological HFOs; in order to apply an HFO detector, an appropriate cut-off threshold is needed; an artefact of the impulse response filter appears as an HFO; and the series was comprised of a small number of heterogeneous patients.

Intraoperative Electrophysiologic Mapping of Medial Frontal Motor Areas and Functional Outcomes.

OBJECTIVE: To propose a method for intraoperative mapping and monitoring of the medial frontal motor areas (MFMA). METHODS: We estimated the location of the MFMA using the corticocortical evoked potential (CCEP) provoked by electric stimuli to the primary motor area (M1) of the upper limb. We localized or defined the MFMA by recording the motor evoked potentials (MEPs) provoked by electric stimuli to the medial frontal cortex around the estimated area. We monitored the patients' motor function during awake craniotomy and sequentially recorded the MEPs of the upper and/or lower limbs. This method was applied to 8 patients. RESULTS: Four patients who had part of the areas identified as the MFMA removed showed transient hemiparesis postoperatively (supplementary motor area [SMA] syndrome). The MEP from the M1 was preserved in the 4 patients. The resection of the identified MFMA might have caused their SMA syndrome. The CCEP showed a strong connection between the M1 and the SMA of the upper limb. Our method did not provoke any seizures. CONCLUSIONS: This is a safe and sensitive method for intraoperative mapping and monitoring of the MFMA by combining electrophysiologic monitoring and awake craniotomy. It is clinically useful for mapping the MFMA and can prevent permanent motor deficits.

Clinical impact of intraoperative CCEP monitoring in evaluating the dorsal language white matter pathway.

In order to preserve postoperative language function, we recently proposed a new intraoperative method to monitor the integrity of the dorsal language pathway (arcuate fasciculus; AF) using cortico-cortical evoked potentials (CCEPs). Based on further investigations (20 patients, 21 CCEP investigations), including patients who were not suitable for awake surgery (five CCEP investigations) or those without preoperative neuroimaging data (eight CCEP investigations including four with untraceable tractography due to brain edema), we attempted to clarify the clinical impact of this new intraoperative method. We monitored the integrity of AF by stimulating the anterior perisylvian language area (AL) by recording CCEPs from the posterior perisylvian language area (PL) consecutively during both general anesthesia and awake condition. After tumor resection, single-pulse electrical stimuli were also applied to the floor of the removal cavity to record subcortico-cortical evoked potentials (SCEPs) at AL and PL in 12 patients (12 SCEP investigations). We demonstrated that (1) intraoperative dorsal language network monitoring was feasible even when patients were not suitable for awake surgery or without preoperative neuroimaging studies, (2) CCEP is a dynamic marker of functional connectivity or integrity of AF, and CCEP N1 amplitude could even become larger after reduction of brain edema, (3) a 50% CCEP N1 amplitude decline might be a cut-off value to prevent permanent language dysfunction due to impairment of AF, (4) a correspondence (<2.0 ms difference) of N1 onset latencies between CCEP and the sum of SCEPs indicates close proximity of the subcortical stimulus site to AF (<3.0 mm). Hum Brain Mapp 38:1977-1991, 2017. © 2017 Wiley Periodicals, Inc.

MEG May Reveal Hidden Population of Spikes in Epilepsy With Porencephalic Cyst/Encephalomalacia.

Porencephalic cyst/encephalomalacia is often associated with intractable epilepsy. A limited number of studies reported magnetoencephalography's (MEG's) potential to help construct treatment strategy for epilepsies associated with porencephalic cyst/encephalomalacia. The authors present here simultaneous electroencephalography (EEG) and MEG findings in three adult patients with pediatric-onset epilepsy due to porencephalic cyst/encephalomalacia. There were two types of spikes: one type was detected by MEG only (EEG-/MEG+), and the other detected by both EEG and MEG (EEG+/MEG+). Both types were seen in all three cases. The EEG-/MEG+ spikes all formed tight clusters; in contrast, the majority of EEG+/MEG+ spikes formed loose clusters. These data suggest that MEG may be helpful to better identify spike populations in epilepsy patients with porencephalic cyst/encephalomalacia. If hidden spike populations were to be found by MEG, this information would affect the interpretation of patient's pathophysiology and planning of intracranial electrode placement.

Voxel-based clustered imaging by multiparameter diffusion tensor images for glioma grading.

Gliomas are the most common intra-axial primary brain tumour; therefore, predicting glioma grade would influence therapeutic strategies. Although several methods based on single or multiple parameters from diagnostic images exist, a definitive method for pre-operatively determining glioma grade remains unknown. We aimed to develop an unsupervised method using multiple parameters from pre-operative diffusion tensor images for obtaining a clustered image that could enable visual grading of gliomas. Fourteen patients with low-grade gliomas and 19 with high-grade gliomas underwent diffusion tensor imaging and three-dimensional T1-weighted magnetic resonance imaging before tumour resection. Seven features including diffusion-weighted imaging, fractional anisotropy, first eigenvalue, second eigenvalue, third eigenvalue, mean diffusivity and raw T2 signal with no diffusion weighting, were extracted as multiple parameters from diffusion tensor imaging. We developed a two-level clustering approach for a self-organizing map followed by the K-means algorithm to enable unsupervised clustering of a large number of input vectors with the seven features for the whole brain. The vectors were grouped by the self-organizing map as protoclusters, which were classified into the smaller number of clusters by K-means to make a voxel-based diffusion tensor-based clustered image. Furthermore, we also determined if the diffusion tensor-based clustered image was really helpful for predicting pre-operative glioma grade in a supervised manner. The ratio of each class in the diffusion tensor-based clustered images was calculated from the regions of interest manually traced on the diffusion tensor imaging space, and the common logarithmic ratio scales were calculated. We then applied support vector machine as a classifier for distinguishing between low- and high-grade gliomas. Consequently, the sensitivity, specificity, accuracy and area under the curve of receiver operating characteristic curves from the 16-class diffusion tensor-based clustered images that showed the best performance for differentiating high- and low-grade gliomas were 0.848, 0.745, 0.804 and 0.912, respectively. Furthermore, the log-ratio value of each class of the 16-class diffusion tensor-based clustered images was compared between low- and high-grade gliomas, and the log-ratio values of classes 14, 15 and 16 in the high-grade gliomas were significantly higher than those in the low-grade gliomas (p < 0.005, p < 0.001 and p < 0.001, respectively). These classes comprised different patterns of the seven diffusion tensor imaging-based parameters. The results suggest that the multiple diffusion tensor imaging-based parameters from the voxel-based diffusion tensor-based clustered images can help differentiate between low- and high-grade gliomas.

Intraoperative dorsal language network mapping by using single-pulse electrical stimulation.

The preservation of language function during brain surgery still poses a challenge. No intraoperative methods have been established to monitor the language network reliably. We aimed to establish intraoperative language network monitoring by means of cortico-cortical evoked potentials (CCEPs). Subjects were six patients with tumors located close to the arcuate fasciculus (AF) in the language-dominant left hemisphere. Under general anesthesia, the anterior perisylvian language area (AL) was first defined by the CCEP connectivity patterns between the ventrolateral frontal and temporoparietal area, and also by presurgical neuroimaging findings. We then monitored the integrity of the language network by stimulating AL and by recording CCEPs from the posterior perisylvian language area (PL) consecutively during both general anesthesia and awake condition. High-frequency electrical stimulation (ES) performed during awake craniotomy confirmed language function at AL in all six patients. Despite an amplitude decline (≤32%) in two patients, CCEP monitoring successfully prevented persistent language impairment. After tumor removal, single-pulse ES was applied to the white matter tract beneath the floor of the removal cavity in five patients, in order to trace its connections into the language cortices. In three patients in whom high-frequency ES of the white matter produced naming impairment, this "eloquent" subcortical site directly connected AL and PL, judging from the latencies and distributions of cortico- and subcortico-cortical evoked potentials. In conclusion, this study provided the direct evidence that AL, PL, and AF constitute the dorsal language network. Intraoperative CCEP monitoring is clinically useful for evaluating the integrity of the language network.

[Primary central nervous system lymphoma mimicking ventriculitis].

A 66-year-old man presented with deteriorated bradykinesia, gait disturbance, disorientation, and urinary incontinence for three weeks. Magnetic resonance imaging (MRI) showed dilatation of the ventricles. Cerebrospinal fluid (CSF) examination demonstrated lymphocytic pleocytosis, elevation of protein levels, and decreased of glucose levels. A gadolinium-enhanced MRI revealed lesions in the ventricular wall and choroid plexus, mimicking ventriculitis. No evidence of bacterial, fungal, mycobacterial, or viral infections were observed in the CSF. Flow cytometry of CSF showed predominance of CD20+, λ+ cells. PCR examination of CSF revealed positive IgH gene rearrangement, suggesting B cell lymphoma. Endoscopic brain biopsy showed diffuse large B cell lymphoma. As the patient had no evidence of lymphoma in the other organs, we made a diagnosed of primary central nervous system lymphoma (PCNSL). A limited intraventricular spread of PCNSL is rare but important as one of differential diagnosis of ventriculitis.

Long-term seizure outcome following resective surgery for epilepsy: to be or not to be completely cured?

Surgical intervention is expected to improve the quality of life in patients with intractable epilepsy by providing adequate seizure control. Although many previous studies showed various rates of seizure freedom, definite conclusions have not yet been made regarding outcomes. In order to clarify the long-term postoperative outcome for a period up to 10 years, a retrospective review of our patients was performed longitudinally by using the survival analysis method. The postoperative state of epilepsy in 76 patients who underwent resection surgery was assessed based on Engel's criteria. In addition, Kaplan-Meier survival analysis was used to calculate the probability of seizure freedom. In this patient group, abnormal lesion were detected by MRI in 70 out of 76 cases, and the ictal onset zone was finally identified within temporal lobe in 51 cases. The most favorable outcome, defined as Engel Class Ia, was observed in 26 (37%), 24 (40%), and 18 (41%) cases at 2, 5, and 10 years after surgery, respectively. The Kaplan-Meier survival curve in the overall group estimated the probability of seizure freedom as 75% (95% confidence interval [CI] 70-80%), 67% (62-72%), and 51% (45-57%) at 2, 5, and 10 years follow up, respectively. Half of all seizure recurrences occurred within the first 2 postoperative years. In this study, we showed that long-term favorable outcome of seizure control following resection surgery can be achieved in more than half of the patients.

Preoperative localization of intracranial lesions with MRI using marking pills.

OBJECTIVE: To describe a simple technique for preoperative surface localization of intracranial lesions. METHODS: 11 pills in total, including Alfarol (alfacalcidol) capsules, were affixed to a phantom with adhesive tape and a MRI scan was performed. The visibility of the pills and any spatial errors in determining their locations were evaluated. Between June 2006 and April 2009, we employed Alfarol capsules as a skin marker in MRI in clinical surgical cases. RESULTS: Alfarol capsules, whose actual size is 5.6 mm in diameter, were identified as a hyperintense spot at a size of 4.2, 4.2, and 4.5mm in diameter in T1-weighted, T2-weighted, and FLAIR (fluid attenuated inversion recovery) sequence images, respectively. The size discrepancies were within 1.4 mm. The average spatial errors were 0.7, 0.6, and 0.7 mm in T1-weighted, T2-weighted, and FLAIR sequence images, respectively. Other pills were not identified in the MRI scans. During this 35-month period, 8 patients underwent preoperative MRI-guided localization at our institution. There were 5 men and 3 women in whom 8 biopsies were performed. In all cases, the result of the biopsy was positive and useful for the treatment that followed. No perioperative complications were encountered. CONCLUSION: Alfarol capsule can be used as an external skin marker. Our simple and inexpensive method is a useful addition to preoperative evaluation of superficial intracranial lesions.

Bilateral discal cysts managed by partial hemilaminectomy and microscopic resection of hemilateral cyst.

STUDY DESIGN: A case report. OBJECTIVE: The objective of this article was to report a case of bilateral lumbar discal cysts and discuss the clinical, radiological, and surgical findings. SUMMARY OF BACKGROUND DATA: Discal cysts are rare lesions and to our knowledge there has been no report on multiple discal cysts at one disc level. METHODS: The patient's history, clinical examination, imaging findings, and treatment were reported. RESULTS: We reported on the case of a 33-year-old woman with left lower back and lower extremity pain. Neurological imagings demonstrated bilateral cysts at the L4-L5 disc level. She underwent left partial hemilaminectomy at the L4-L5 level and microscopic resection of the left cyst. The cyst contained bloody serous fluid. A connection between the cyst wall and the L4-L5 intervertebral disc and a small laceration in the annulus fibrosus were identified. Histologic examination revealed a cyst lined by fibrous connective tissue without synovium. Her symptoms improved remarkably immediately after surgery. Follow-up imaging 3 months after the operation showed that the bilateral cysts had completely disappeared. CONCLUSION: This is the first reported case of bilateral discal cysts at one disc level. Magnetic resonance images demonstrated rounded cysts on both sides of the posterior longitudinal ligament, which suggests that the discal cysts in our case were unlikely to have developed from an epidural hematoma. Partial hemilaminectomy and microscopic resection of the left cyst lead to complete regression of the bilateral cysts. This suggests that there was a communication between the two cysts via the intervertebral disc and that the content of the right cyst passed from the cyst to the disc.

[A case of A3-A3 bypass and proximal clipping for a ruptured left A1 dissecting aneurysm].

A 58-year-old woman was admitted to our hospital with sudden onset of headache. CT and angiogram revealed subarachnoid hemorrhage due to a dissecting aneurysm at the left A1 segment. ACoA was not identified. We performed proximal clipping with A3-A3 bypass for preventing the recurrence of the hemorrhage and for reducing ischemia in the territory of the left ACA. After the operation, CT revealed the infarctions in the corpus callosum, the left medial frontal lobe and the genu of the internal capsule. But the postoperative angiogram demonstrated no aneurysm and the opacification of the recurrent artery of Heubner and the part of perforating branches. A3-A3 bypass was patent. The patient experienced a good recovery without recurrence of bleeding.