Kimiaki Hashiguchi

Effect of tumor removal on tinnitus in patients with vestibular schwannoma.

OBJECT Tinnitus is one of the most common symptoms in patients with vestibular schwannomas (VSs), but the effect of surgery on this symptom has not been fully evaluated. The aim of this study was to define the effect on tinnitus of tumor removal, cochlear nerve resection, and useful hearing preservation in patients with VSs. METHODS The authors retrospectively analyzed the status of tinnitus before and after surgery in 242 patients with unilateral VSs who underwent surgery via the retrosigmoid lateral suboccipital approach. RESULTS Of 242 patients, 171 (70.7%) complained of tinnitus before surgery; the symptom disappeared in 25.2%, improved in 33.3%, remained unchanged in 31.6%, and worsened in 9.9% of these cases after tumor removal. In the 171 patients with preoperative tinnitus, the cochlear nerve was resected in 85 (49.7%) and preserved in 86 (50.3%), but there was no significant difference in the incidence of postoperative tinnitus between these 2 groups (p = 0.293). In the 71 patients without preoperative tinnitus, the symptom developed postoperatively in 6 cases (8.5%). Among those without preoperative tinnitus, the cochlear nerve was resected in 45 cases (63.4%) and tinnitus appeared postoperatively in 3 (6.7%). The authors also analyzed the association between postoperative tinnitus and useful hearing preservation, but could not find any statistically significant association between the 2 factors (p = 0.153). CONCLUSIONS Tumor removal via the retrosigmoid lateral suboccipital approach may provide some chance for improvement of tinnitus in patients with VSs; however, neither cochlear nerve resection nor useful hearing preservation affects the postoperative development of tinnitus.

Correlation between scalp-recorded electroencephalographic and electrocorticographic activities during ictal period

OBJECTIVE To investigate the correlation between scalp-recorded electroencephalographic (EEG) and electrocorticographic (ECoG) activities during ictal periods. METHODS Simultaneous EEG and ECoG recordings with chronic subdural electrodes were performed in eight patients with partial epilepsy. RESULTS In two cases where the ictal ECoG discharges originated in deep brain structures such as the hippocampus and interhemispheric surface of the frontal lobe, ictal discharges could not be detected on EEG until they expanded to the cortex of convexity. In four cases, the ictal onset zones were located in the lateral convexity. When synchronous or near synchronous ictal ECoG discharges with amplitudes of 200-2000muV were recorded on more than 8-15cm(2) of cortex, corresponding discharges were recorded on EEG in these four cases. However, in a case of frontal lobe epilepsy, asynchronous ictal ECoG discharges were recorded on 10 electrodes of convexity but no ictal EEG activity was recorded. Furthermore, in two frontal lobe epilepsy cases, ictal EEG discharges did not always reflect the ictal ECoG spike, but occasionally reflected slow background ECoG activity around the ictal discharges. CONCLUSIONS Multiple factors such as the width of the cortical area involved, amplitude of ictal discharges and degree of synchronization of electrical potentials play important roles in the appearance of ictal EEG recordings, and the relationship between ictal EEG and ECoG is not straightforward.

Assessment of Contact Location in Subthalamic Stimulation for Parkinson’s Disease by Co-Registration of Computed Tomography Images

Aims: To study the validity of a co-registration method for postimplantation computed tomography (CT) images for localizing the location of an intracranial deep brain stimulator. Methods: Three-dimensional reconstruction images of postimplantation CTs were co-registered with preoperative CTs by stereotactic planning software and used to localize 18 leads in the subthalamic nuclei of 10 patients with Parkinson’s disease. Our conventional method using superimposition of sagittal postimplantation magnetic resonance (MR) images were employed as a comparison. Results: The co-registered CT images separately visualized four individual contacts; on the other hand, the MR superimposition method demonstrated the leads as a group of no MR signal areas. Although laterality of the distal contact did not differ between two methods, the distal contact was located more anteriorly and inferiorly by the MR superimposition method than by the CT co-registration method. Conclusion: The CT co-registration method is superior to MR in visualizing deep brain stimulation contacts and resolves problems of MR safety in patients treated with a neurostimulator.

Dynamic morphological changes in lumbosacral lipoma during the first months of life revealed by constructive interference in steady-state (CISS) MR imaging

Objects and methodsIn this study, we demonstrate the morphological change in two cases of lumbosacral lipoma during the first few months of life using a three-dimensional Fourier transformation-constructive interference in a steady-state (CISS) sequence that enables high-resolution images to be obtained with excellent contrast between cerebrospinal fluid (CSF), spinal roots, and lipoma.ResultsThe CISS images clearly demonstrated the dynamic morphological changes such as lipoma growth observed in both cases and increased tethering effect in the case with lipomyelomeningocele.ConclusionWe have to keep in mind the potential for these morphological changes of the spinal lipoma during the first few months of life.

Feasibility and limitation of constructive interference in steady-state (CISS) MR imaging in neonates with lumbosacral myeloschisis

IntroductionThe aim of this study was to evaluate three-dimensional Fourier transformation-constructive interference in steady-state (CISS) imaging as a preoperative anatomical evaluation of the relationship between the placode, spinal nerve roots, CSF space, and the myelomeningocele sac in neonates with lumbosacral myeloschisis.MethodsFive consecutive patients with lumbosacral myeloschisis were included in this study. Magnetic resonance (MR) CISS, conventional T1-weighted (T1-W) and T2-weighted (T2-W) images were acquired on the day of birth to compare the anatomical findings with each sequence. We also performed curvilinear reconstruction of the CISS images, which can be reconstructed along the curved spinal cord and neural placode.ResultsNeural placodes were demonstrated in two patients on T1-W images and in three patients on T2-W images. T2-W images revealed a small number of nerve roots in two patients, while no nerve roots were demonstrated on T1-W images. In contrast, CISS images clearly demonstrated neural placodes and spinal nerve roots in four patients. These findings were in accordance with intraoperative findings. Curvilinear CISS images demonstrated the neuroanatomy around the myeloschisis in one slice. The resulting images were degraded by a band artifact that obstructed fine anatomical analysis of the nerve roots in the ventral CSF space. The placode and nerve roots could not be visualized in one patient in whom the CSF space was narrow due to the collapse of the myelomeningocele sac.ConclusionMR CISS imaging is superior to T1-W and T2-W imaging for demonstrating the neural placode and nerve roots, although problems remain in terms of artifacts.

Fetal Germinal Matrix and Intraventricular Hemorrhage

Subependymal germinal matrix with intraventricular hemorrhage (GMIVH) is a common complication associated with delivery in preterm neonates but has rarely been observed in the fetus. Clinical and neuroradiological findings of 5 patients who were diagnosed as having fetal GMIVH with prenatal ultrasonographic examinations (US) and MRI, and postnatal MRI were reviewed retrospectively. During a seemingly uneventful pregnancy, fetal GMIVH occurred at approximately 30–33 weeks of gestation, with the absence of any known factor predisposing to fetal hemorrhage. Routine obstetric US revealed an intraventricular lesion in the enlarged ventricles. Prenatal MRI clearly demonstrated parenchymal change such as intracerebral hematoma adjacent to the subependymal and intraventricular hematoma, and periventricular leukomalacia as well as GMIVH. Although patients without parenchymal destruction (hemosiderin deposit alone) had a favorable neurodevelopmental outcome, encephalomalacia and periventricular leukomalacia contributed to long-term neurodevelopmental deficits. Evaluating parenchymal damage with prenatal MRI can therefore help to predict neurodevelopmental prognosis of the fetus with GMIVH.

Spectral Analysis of Field Potential Recordings by Deep Brain Stimulation Electrode for Localization of Subthalamic Nucleus in Patients with Parkinson’s Disease

Aims: Spectral analysis of local field potential (LFP) recorded by deep brain stimulation (DBS) electrode around the subthalamic nucleus (STN) in patients with Parkinson’s disease was performed. Methods: The borders of the STN were determined by microelectrode recording. The most eligible trajectory for the sensorimotor area of the STN was used for LFP recording while advancing the DBS electrode. Results: The low-frequency LFP power (θ- to β-band) increased from a few millimeters above the dorsal border of the STN defined by microelectrode recording; however, the low-frequency power kept the same level beyond the ventral border of the STN. Only high β-power showed close correlation to the dorsal and ventral borders of the STN. Conclusions: A spectral power analysis of LFP recording by DBS electrode helps with the final confirmation of the dorsal and ventral borders of the STN of Parkinson’s disease in DBS implantation surgery.

Focal cortical dysplasia type IIa underlying epileptogenesis in patients with epilepsy associated with Sturge-Weber syndrome.

In patients with epilepsy associated with Sturge‐Weber syndrome (SWS), epileptogenesis has been suggested to be caused by chronic ischemia in cortical areas affected by leptomeningeal angiomatosis or by ischemia‐related cortical malformations. However, this has not been fully verified electrophysiologically. We herein present two cases of SWS with medically intractable epilepsy in which the epileptogenic area involved focal cortical dysplasia (FCD) type IIa near the region of leptomeningeal angiomatosis. In both cases, the ictal‐onset zones were identified by chronic subdural electrodes, and the presence of FCD type IIa was shown histopathologically. In SWS, especially in association with focal leptomeningeal angiomatosis, FCD may thus play a major role in epileptogenesis. FCD should therefore be demonstrated by the collective findings of perioperative neurophysiologic examination, anatomic and functional neuroimaging, and histopathologic examination.

Utility of 3-T FLAIR and 3D short tau inversion recovery MR imaging in the preoperative diagnosis of hippocampal sclerosis: Direct comparison with 1.5-T FLAIR MR imaging

Purpose:  To examine the utility of fluid‐attenuated inversion recovery (FLAIR) imaging and three‐dimensional short tau inversion recovery (3DSTIR) imaging using a 3‐Tesla (3‐T) magnetic resonance (MR) imager in the preoperative evaluation of hippocampal sclerosis (HS).

Thalamic hypometabolism on 18FDG-positron emission tomography in medial temporal lobe epilepsy

Abstract Objectives: Degree of hypometabolism in the thalamus on 18Fluorodeoxyglucose-positron emission tomography (FDG-PET) was compared with those of medial and lateral temporal lobes in patients with medial temporal lobe epilepsy (mTLE), and its relationship with post-operative seizure outcomes was investigated. Methods: Twenty-six patients with mTLE who underwent anterior temporal lobectomy were included. Post-operatively, 13 patients became completely seizure-free and 13 showed residual seizure, regardless of frequency (five patients became almost seizure-free, six had rare seizures and two showed significant improvements). Degrees of hypometabolism in bilateral thalamus, ipsilateral medial and lateral temporal lobes were evaluated visually and semi-quantitatively by determining the asymmetry index (AI), a value indicating 100 × (ipsilateral - contralateral)/[1/2 × (ipsilateral + contralateral)] and the region-to-cerebral hemisphere ratio (R/C ratio) being the ratio between averaged counts in each area and those in the cerebral hemisphere of the same side. Results: Hypometabolism in the medial temporal lobe was visually observed in all patients. Hypometabolism in the lateral temporal lobe was observed in 20 patients and was semi-quantitatively more prominent than that of the medial temporal lobe. Pathologically, hippocampal sclerosis and prominent astrogliosis of the lateral temporal lobe were present in all cases. However, while thalamic hypometabolism was visually observed in nine patients (in the ipsilateral side of four cases, contralateral side of three and on both sides of two), no significant thalamic hypometabolism was semi-quantitatively observed. No significant differences in metabolic rate in any area except for the lateral temporal lobe between seizure-free patients and residual seizure patients were seen semi-quantitatively. Discussion: Data indicated that metabolism in the lateral temporal lobe of patients with mTLE significantly decreased and revealed pathologic glial changes. Thalamic hypometabolism was quite mild and did not correlate with post-operative seizure outcome.