Visual networks: Electric brain stimulation and diffusion tensor imaging.

OBJECTIVE: The present study investigated the networks of visual functional areas using electric brain stimulation (EBS) and diffusion tensor imaging (DTI). METHODS: Thirteen patients with intractable focal epilepsy in which visual functional areas were identified by EBS were enrolled. An electric stimulation at 50Hz was applied to electrodes during several tasks. DTI was used to identify subcortical fibers originating from the visual functional areas identified by EBS. RESULT: The electrical stimulation induced three types of visual symptoms: visual illusions (change of vision), visual hallucinations (appearance of a new object), and blurred vision. Visual illusions were associated with stimulation of lateral temporo-parieto-occipital areas, and visual hallucinations with stimulation of lateral/basal temporal areas, the occipital lobe and the precuneus. Stimulus intensities eliciting visual illusions were significantly higher than those for visual hallucinations. Tractography revealed that the superior fronto-occipital fasciculus was associated with visual illusions and the middle longitudinal fasciculus with visual hallucinations, and both symptoms shared several subcortical fibers such as the vertical occipital fasciculus, inferior fronto-occipital fasciculus, superior longitudinal fasciculus, inferior longitudinal fasciculus, optic radiations, and commissural fibers. CONCLUSION: The present study revealed the characteristic cortical regions and networks of visual functional areas. The results obtained provide information on human visual functions and are a practical guide for electrical cortical stimulation.

Usefulness of Intraoperative Electrocorticography for the Localization of Epileptogenic Zones.

Intraoperative electrocorticography (iECoG) is widely performed to identify irritative zones in the cortex during brain surgery; however, several limitations (e.g., short recording times and the effects of general anesthesia) reduce its effectiveness. The present study aimed to evaluate the utility of iECoG for localizing epileptogenic zones. We compared the results of iECoG and chronic electrocorticography (cECoG) in 25 patients with refractory epilepsy. Subdural electrodes were implanted with iECoG under general anesthesia (2% sevoflurane). cECoG recordings were performed for 3-14 days. The distribution of iECoG spikes was compared with cECoG spike, seizure onset zone, and resection areas. The concordance patterns of each distribution were classified into four patterns: Group 1: No spike in iECoG, Group 2: concordant (2a: iECoG smaller, 2b: iECoG larger, Group 3: discordant >50%). The concordance rate of interictal spikes, seizure onset zones, and resection areas were 88.0% (Group 2a: 72.0%, Group 2b: 16.0%), 70.0% (Group 2a: 25.0%, Group 2b: 45.0%), and 81.0% (Group 2a: 42.9%, Group 2b: 38.1%), respectively. The resection of iECoG spike areas significantly correlated with good surgical outcomes. The indication and limitations of iECoG need to be realized, and the complementary use of iECoG and cECoG may enhance clinical utility.

Cerebrospinal Fluid CSF Flow Artifacts are Associated with Brain Pulsation in Patients with Severe Carotid Artery Stenoses.

OBJECTIVE: We investigated the factors associated with cerebrospinal fluid (CSF) flow artifacts on fluid-attenuated inversion recovery imaging in patients with carotid artery (CA) stenosis. METHODS: Each CSF artifact grade was defined by comparing the highest intensity in a given region of interest (ROI) to those in reference ROIs, as follows: higher than the intensity of normal white matter in the centrum semiovale = 2 points; equal to or less than the white matter, and higher than CSF = 1 point; and equal to CSF = 0. CSF flow scores in eight sites were measured and added to the total score (0 -16). The prevalences of each finding, specifically white matter lesions, CA stenoses and brain atrophy, were compared using multivariate logistic regression models. RESULTS: We evaluated the findings in 54 patients with CA stenosis treated by CA stenting (CAS) and 200 adults with no history of neurological disorders (control group). Adjusted by stroke risk factors, a CSF flow score ≤ 11 was positively associated with CA stenosis, heart rate > 70 / min, and brain atrophy, and negatively with the female gender. The score was 12.8 ± 1.8 in the control group and 12.0 ± 2.0 in CA stenosis group after CAS, which was significantly higher than before CAS (10.4 ± 2.8, p<0.001). CONCLUSION: The CSF flow score was associated with female gender, brain atrophy, heart rate, and severe CA stenosis, and was found to be elevated after revascularization.

Comparison of Thresholds between Bipolar and Monopolar Electrical Cortical Stimulation.

Electrical cortical stimulation is widely performed and is the gold standard for functional mapping in intractable epilepsy patients; however, a standard protocol has not yet been established. With respect to stimulation methods, two techniques can be applied: monopolar and bipolar stimulation. We compared the threshold to induce clinical symptoms between these two stimulation techniques. Twenty patients with intractable epilepsy who underwent electrical cortical stimulation for functional mapping were retrospectively investigated. We evaluated the stimulation intensity thresholds required to induce motor, sensory, and language symptoms. A total of 114 electrodes in 20 patients were used to investigate motor, sensory, and language symptoms. The thresholds required to induce motor (median value, bipolar: 4 mA, monopolar: 5 mA, p < 0.05) and language symptoms (bipolar: 8 mA, monopolar: 10 mA, p < 0.0005) were significantly higher for monopolar stimulation than those for bipolar stimulation. However, for sensory symptoms, no significant differences were found in the required thresholds between monopolar and bipolar stimulation (bipolar: 4 mA, monopolar: 4 mA, p = 0.474). Bipolar cortical stimulation required lower intensities to produce clinical motor and language symptoms and thus would be safe and suitable for screening of the eloquent area in functional mapping.

Elongated Internal Carotid Arteries in Patients with Severe Carotid Artery Stenosis.

OBJECTIVE: This study aimed to investigate the risk factors and asymptomatic cerebrovascular diseases associated with elongated internal carotid arteries (ICAs) and the relationship between ICA elongation and severe carotid artery (CA) stenosis. METHODS: We evaluated risk factors for stroke and magnetic resonance imaging (MRI) findings in patients with severe CA stenosis compared with people without neurological disorders who underwent brain screening (controls). On magnetic resonance angiography (MRA) images, we measured the longest distance, defined as the ICA distance, from the most distant anterior wall of the cervical ICA at the site of bending or kinking to the line between the origin of the external CA and the anterior protrusion of the ICA near the petrosal bone. We retrospectively compared various asymptomatic findings, including cerebral microbleeds, lacunar infarctions, and deep white matter hyperintensities (WMHs), between participants with an ICA distance ≥ 1.2 cm vs. < 1.2 cm. The prevalence of findings and stroke risk factors were compared using multivariate logistic regression models. RESULTS: We evaluated 53 patients (70.0 ± 8.1 years old, nine female) with severe CA stenosis treated by CA stenting and 400 controls (63.0 ± 9.2 years old, 227 females). Multivariate analyses showed that ICA distance ≥ 1.2 cm was associated with age ≥ 65 years (odds ratio (OR) = 1.8, p < 0.01), severe deep WMHs (OR = 2.0, p = 0.02), and severe CA stenosis (OR = 0.17, p < 0.01). CONCLUSION: ICA elongation, measured by ICA distance, was positively associated with age and deep WMHs and negatively associated with severe CA stenosis.

Natural Y-shaped radial artery graft bypass for a complex middle cerebral artery aneurysm: A case report.

Giant thrombosed middle cerebral artery (MCA) aneurysms are difficult to treat and sometimes require complex revascularization using allografts. We describe a technical method using revascularization with a natural Y-shaped graft that provides a normal variation for a complex MCA aneurysm. A 65-year-old man with a giant thrombosed MCA aneurysm presented with right hemiparesis and aphasia. The patient had a history of clipping surgery for the ipsilateral side of the MCA aneurysm 25 years before, and a de novo aneurysm developed over the previous 18 years. For the giant thrombosed aneurysm, trapping and revascularization were performed. A natural radial artery Y-graft was used as the graft and anastomosed to both M2 trunks. The symptoms improved after surgery, and the patient was discharged 3 weeks later. This is the first report of a double-barrel bypass using a natural Y-graft. This method attained a normal variation, and the flow of the Y-graft was physiological. For the radical cure of giant thrombosed MCA aneurysms, multiple revascularizations might be required. With this natural Y-graft, complex transpositions could be avoided.

Inflammation promotes progression of thrombi in intracranial thrombotic aneurysms.

Advances in the understanding of the pathogenesis of arteriosclerosis, abdominal aorta aneurysms and dissections, and carotid artery plaques have focused on chronic inflammation. In this study, we report that inflammatory changes of thrombi contribute to the enlargement and growth of giant intracranial thrombotic aneurysms. Surgical and postmortem samples were collected from 12 cases of large or giant intracranial thrombotic aneurysms diagnosed via pathological investigations. Degeneration of the aneurysmal wall and the infiltration of inflammatory cells in the thrombi were assessed. The number of blood cells and immunohistochemical stain-positive cells was enumerated, and the inflammation and neovascularization in the thrombi were assessed. In all cases, the appearance of inflammatory cells (CD68+ cells, CD206+ cells, lymphocytes, and neutrophils) was apparent in the thrombi. The number of CD34+ cells was moderately correlated with the number of CD68+ cells, and CD34+ cells significantly and strongly correlated with the number of CD206+ cells. Based on the number of neutrophils per CD68+ cells, we classified the cases into 2 groups: a macrophage inflammation-dominant group and a neutrophilic inflammation-dominant group. The neutrophilic inflammation-dominant group had significantly more cases with previous treatments and neurological symptoms due to mass effect than the macrophage inflammation-dominant group. Chronic inflammation due to macrophages in thrombi is a fundamental mechanism in the enlargement of an intracranial thrombotic aneurysm, and neutrophilic inflammation can accelerate this process. Microvascularization in thrombi is linked to inflammation and might promote thickening of the intima and repeated intimal microbleeds.

Total Resection of Unilateral Adult-onset Xanthogranuloma of the Orbit via a Transcranial Orbital Approach.

Adult orbital xanthogranuloma is rare and usually associated with systemic disease. There are several options available to treat this disorder. Periorbital lesions are treated with steroids, chemotherapy, radiotherapy, or local excision; however, there is still no consensus regarding optimal treatment. Here, we report a rare case of orbital xanthogranuloma that was not associated with systemic disease and was treated by transcranial surgery. The patient was a 52-year-old man who presented with a 2-year history of unilateral eye symptoms. A computed tomography scan revealed a well-defined mass in the right orbit. The mass was completely removed via a transcranial orbital approach. The histopathologic diagnosis was xanthogranuloma. No recurrence was observed during 15 months of postoperative follow-up. Complete surgical resection might be an effective treatment option for locally growing sporadic adult xanthogranulomatous disease of the orbit, and allows systemic steroids, chemotherapy, and irradiation to be avoided.

Psychogenic Pseudo-responses in an Electrical Cortical Stimulation.

An electrical cortical stimulation provides important information for functional brain mapping. However, subjective responses (i.e. sensory, visual, and auditory symptoms) are purely detected by patients' descriptions, and may be affected by patients' awareness and intelligence levels. We experienced psychogenic responses in the electrical cortical stimulation of two patients with intractable epilepsy. A sham stimulation was useful for differentiating pseudo-responses from real responses in the electrical cortical stimulation. Inductive questions, long testing durations, and clear cues of stimulation onsets need to be avoided to prevent psychogenic pseudo-responses in the electrical cortical stimulation. Furthermore, a sham stimulation is applicable for detecting pseudo-responses the moment patients show atypical or inexplicable symptoms.

Pseudoaneurysm presenting around polytetrafluoroethylene fiber following microvascular decompression: A case report and literature review.

We report the first case of pseudoaneurysm associated with polytetrafluoroethylene fiber used in microvascular decompression (MVD). A 62-year-old female who had undergone MVD for hemifacial spasm 30 years ago presented with a 4-month history of progressive facial palsy. Computed tomography angiography revealed a large thrombosed aneurysm originating from the right posterior inferior cerebellar artery and having a mass effect upon the pons. The aneurysm was treated by trapping and bypass procedure. Intraoperatively, the pseudoaneurysm adhered to the dura mater, and the thrombus contained a large amount of polytetrafluoroethylene fiber. The cause and management of pseudoaneurysm after MVD is discussed.

Giant petrous internal carotid aneurysm causing epistaxis: A case report.

Aneurysms of the internal carotid artery (ICA) arising from the petrous portion are extremely rare, and most cases are asymptomatic or cause a mass effect leading to palsy of the adjacent cranial nerves. In rupture cases, massive nasal and ear bleeding occurs, which may cause death. We describe a 73-year-old man with a giant ICA aneurysm arising from the petrous portion and presenting as epistaxis. The patient had no history of trauma or clotting disorders. Computed tomography angiography demonstrated a giant petrous carotid aneurysm and erosion of a part of the left temporal bone. The patient was treated by trapping of the aneurysm with high-flow bypass using a radial artery. From an anatomical view point, rupture of ICA aneurysms of this portion might be caused by thinness of the bone partition between the ICA and the sphenoidal sinus. It should be noted that petrous carotid aneurysms are usually asymptomatic but may cause massive epistaxis in cases of rupture.

Meningioma mimicking an intraparenchymal cystic tumor.

Meningiomas rarely exhibit cystic lesions with mural nodules, and may be misdiagnosed as intraparenchymal cystic tumors. We herein present a 64-year-old woman with a cystic lesion and enhancing mural nodule in the left temporal lobe accompanied by peritumoral brain edema. Differential diagnoses included low-grade gliomas, hemangioblastoma, and cystic meningioma. Gross total resection of the tumor was achieved through a temporal surgical approach. Intraoperative findings showed that the tumor was an extraparenchymal tumor. The cyst was covered by an extraparenchymal thin membrane and the cystic fluid was yellowish in color. The final result of the pathological examination was microcystic meningioma, WHO grade I. Although intraparenchymal tumors, such as hemangioblastoma, ganglioglioma, pilocytic astrocytoma, and pleomorphic xanthoastrocytoma, commonly display this MRI pattern, meningioma needs to be included in the differential diagnosis.

Influence of hemodynamics on enlarged perivascular spaces in atherosclerotic large vessel disease.

OBJECTIVES: Enlarged perivascular spaces (EPVS) are often observed in small vessel disease on T2-weighted images. However, their role in ischemic conditions caused by cerebral large vessel disease remains unclear. We evaluated EPVS in patients with hemodynamic compromise associated with atherosclerotic large vessel disease and aimed to identify the pathophysiology of EPVS. METHODS: We examined 28 adults with atherosclerotic large vessel disease. EPVS numbers in the basal ganglia and the centrum semiovale were assessed. For each affected hemisphere, the total numbers of EPVS were compared with those on the unaffected side. EPVS in the impaired hemodynamics group were compared with those in the unimpaired hemodynamics group. Moreover, EPVS were compared in the presence/absence of large stroke. RESULTS: The number of EPVS was significantly increased on the affected side in the centrum semiovale (p = 0.023), particularly in the impaired hemodynamics group (p = 0.006). Moreover, in the small stroke subgroup of the impaired hemodynamics group, the number of EPVS was significantly increased on the affected side (p = 0.002), although this number was insignificant in the large ischemic stroke subgroup. CONCLUSIONS: The number of EPVS was increased in patients with atherosclerotic large vessel disease with hemodynamic compromise and decreased in the presence of a large stroke. EPVS might act as fluid absorbers in a hemodynamically compromised state until the occurrence of an ischemic stroke.