Nobuo Oka

Measurement of regional blood flow using hydrogen gas generated by electrolysis.

Electrochemically generated hydrogen gas was used to measure local blood flow by Stosseck et al. The data obtained by their method, however, did not correlate well with those obtained by hydrogen inhalation. We have modified the equation proposed by Stosseck, prolonging the stimulus duration in order to increase the amount of hydrogen generated. In dog white matter the resulting clearance curves were formed to be monoexponential both in the living animal as well as after circulatory arrest when all the clearance is by diffusion away from the electrode. The values calculated by our equation correlated well with those obtained by hydrogen inhalation.

Spontaneous occlusion of traumatic carotid cavernous fistula after orbital venography

A 50-year-old man was admitted to our hospital with a diagnosis of traumatic carotid cavernous fistula. The fistula was observed to disappear spontaneously just after orbital venography. This was confirmed by clinical examinations and subsequent carotid angiogram. The possible mechanisms responsible for the spontaneous occlusion of carotid cavernous fistula are discussed.

Post-traumatic intention tremor--clinical features and CT findings.

Eight patients with post-traumatic intention tremor were reported. Intention tremor developed in the young as a late complication of severe head injury (Glasgow Coma Scale was below 8 in all cases) and impaired their functional outcome. This state was treatable with medication or by stereotactic thalamotomy. Neurologically, all the patients lapsed into coma immediately after the injury and many patients manifested clinical signs of a midbrain lesion in the chronic stage. The characteristic CT (computed tomography) findings in the acute stage were a high density area in the midbrain, accompanied by diffuse cerebral swelling or intraventricular hemorrhage, and in the chronic stage, brain atrophy or ventricular enlargement were the most prominent CT findings. These characteristics, indicating diffuse brain damage in addition to midbrain injury, may suggest the presence of shearing injury. The midbrain damage is consistent with the classical hypothesis that the damage to the Dentate-Rubro-thalamic system accounts for the occurrence of intention tremor. Furthermore, the presence of diffuse brain damage suggests that a more widespread brain injury may participate in its development.

Hyperactivity of the facial nucleus produced by chronic electrical stimulation in rats

OBJECTIVE There are two hypotheses for the pathogenesis of hemifacial spasm (HFS): abnormal cross-transmission between the facial nerve fibers at a site of vascular compression, and hyperactivity of the facial nucleus. To further elucidate the mechanism of HFS, we established an animal model. We applied chronic electrical stimulation (CES) to the facial nucleus in rats, and clarified functional and morphological changes in the nucleus. METHOD Under anesthesia, a novel intracranial electrode was stereotactically implanted in the facial nucleus of six rats. CES of the facial nucleus via the implanted electrode was applied for 5 min daily for three weeks (CES animals). Facial electromyograms (EMGs) were recorded at rest and during electrical stimulation to study the excitability of the facial nucleus at 1, 2, and 4 weeks after initiating CES. As control animals, six rats were implanted with intracranial electrodes, but did not undergo CES. Electrophysiological studies of the control animals were performed using the same protocol as in the CES animals. RESULT Spontaneous abnormal movement of the facial muscle mimicking HFS did not occur. Four weeks after starting CES, one of the six CES animals developed an abnormal EMG response with a latency of 10 ms. No control animals developed such a response. CONCLUSIONS CES of the facial nucleus can produce an abnormal EMG response very similar to the abnormal muscle response (AMR) characteristic of HFS patients. Kindling-like hyperactivity of the facial nucleus induced by CES is the cause of the AMR, suggesting a pathogenesis of HFS.

Presurgical functional localization of primary somatosensory cortex by dipole tracing method of scalp-skull-brain head model applied to somatosensory evoked potential

The aim of the present study was to explore the utility of dipole tracing (DT) of a scalp-skull-brain (SSB) head model in preoperative functional localization of the human brain. Nine patients who underwent surgery of mass lesions around the central sulcus (CS) were employed. By using SSB/DT, dipole source location of early cortical components of the somatosensory evoked potential (SEP) was estimated before surgery. Motor cortex, CS and primary somatosensory cortex were determined by cortical SEP during surgery. After surgery precise functional mapping was reproduced in MRI, and the accuracy of DT was evaluated by measuring the distance between estimated dipole source and the posterior bank of the CS. We defined this distance as localization error of DT. In 4 cases without structural change around the sensorimotor cortex, localization error ranged from 1 to 4 mm with an average of 2 mm. In 5 cases with structural alteration of sensorimotor cortex, localization error ranged from 6 to 10 mm with an average of 8 mm. The difference in localization error between the two groups was statistically significant, and may have been caused by changes of conductance near sensorimotor cortex in the latter group. Functional localization by DT was accurate and useful. But localization error could not be ignored in cases with structural alteration in the sensorimotor cortex.

Intraoperative monitoring of cochlear nerve compound action potential in cerebellopontine angle tumour removal

Cochlear nerve compound action potential (CNAP) provides a real-time auditory evoked potential. Because of technical difficulty, CNAP monitoring has not been popular during the removal of cerebellopontine angle (CPA) tumour. To clarify the efficiency of intraoperative CNAP monitoring, we designed an intracranial electrode for CNAP monitoring and performed the simultaneous monitoring of CNAP and auditory brainstem response (ABR) in 10 patients undergoing CPA tumour removal in an attempt to preserve hearing. ABR recordings during microsurgical tumour removal were unsatisfactory in 6 patients because of severe artifacts. Reliable CNAP recordings were obtained without artifacts in all 10 patients throughout surgery. Eight patients preserved useful hearing after tumour removal, and the CNAP amplitude reflected the postoperative hearing. The newly designed intracranial electrode enables CNAP monitoring predicting the postoperative hearing more reliably than ABR. CNAP monitoring is efficient to improve the hearing preservation rate following CPA tumour removal.

Intracranial hemorrhage due to rupture of an arteriovenous malformation in a full-term neonate

A case of neonatal intracerebral hemorrhage (ICH) secondary to rupture of an arteriovenous malformation (AVM) is reported. The baby began to vomit frequently 9 h after birth. Computed tomographic scan revealed the presence of an ICH. Intravenous digital subtraction angiography (IVDSA) demonstrated an AVM, which was successfully excised on the 2nd day after birth. It is stressed that IVDSA is safe and noninvasive in comparison with conventional angiography and is useful for diagnosis of cerebral vascular disease in neonates.

A case of septic cavernous sinus thrombosis with sequential dynamic angiographic changes. A case report

A case of intracavernous aneurysm secondary to septic cavernous sinus thrombosis demonstrating sequential dynamic angiographic changes is reported. Serial angiograms of a 32-year-old man with septic cavernous sinus infection revealed a normal study, stenosis, recovery of stenosis, and aneurysmal formation. Superficial temporal-middle cerebral artery anastomosis and internal carotid artery ligation were performed because of progressive ophthalmoplegia. Neurological deficit rapidly disappeared. Anigiographic changes and surgical treatment of septic cavernous sinus thrombosis are discussed.

Dipole source localization of ictal epileptiform activity in estimation of epileptogenic zone

Abstract Localization analysis of epileptogenic zone was performed by dipole tracing method with scalp–skull–brain head model (SSB-DT) in patients with intractable epilepsy. Eight temporal lobe epilepsy (TLE) and one frontal lobe epilepsy were studied. EEG was recorded by digital electroencephalograph with 21 scalp electrodes. Generator source of the peak of ictal epileptiform activity (IEA) was estimated by SSB-DT. All the patients underwent electrocorticography (ECoG) and resection of epileptogenic zone. Surgical outcome was good in every patient. Locations of generator source of the peak of IEA estimated by SSB-DT were consistent with locations of epileptogenic zone determined by ECoG and neuroimagings, such as magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT). In TLE, medial and lateral temporal epileptogenic zone could be discriminated, which could not be determined by visual interpretation of scalp EEG. In medial TLE, as an advance of seizure, generator source of IEA either stayed in the medial temporal lobe, or propagated to the lateral temporal lobe. Locations of epileptogenic zone could be estimated by SSB-DT not invasively. Electrophysiological event in the brain during an advance of seizure attack could also be observed. Application of SSB-DT to IEA was useful in the medical treatment of epilepsy, especially in surgical planning for patients with medically intractable epilepsy.

Increased brain glucose metabolism in chronic severe traumatic brain injury as determined by longitudinal 18F-FDG PET/CT

Little is known about changes in glucose metabolism in patients with chronic severe traumatic brain injury (sTBI). It remains to be elucidated how neurological manifestations of sTBI are associated with brain glucose metabolism during longitudinal follow-up. We show here that neurological manifestations are associated with changes of brain glucose metabolism by using two serial 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) images. In this longitudinal observational study, two serial 18F-FDG PET/CT images from each of 45 patients were analyzed for whole-brain maximum standardized uptake values (SUVmax). For clinical assessment, we applied two different scales: the coma recovery scale-revised and the original Chiba score with additional information regarding nutrition, excretion, facial expression, and position change of the patients relative immobility and bedridden state. As a result, the increased FDG uptake group was associated with a high level of wakefulness (first PET, p = 0.04; second PET, p = 0.01) and small ventricular size (first PET, p = 0.01; second PET, p = 0.01). In addition, anticonvulsant withdrawal (p = 0.001), improvement of total Chiba score (p = 0.01), language expression (p = 0.03), position change (p = 0.03), and communication (p = 0.03) were accelerated in the increased FDG uptake group. Spearmans rank correlation coefficients of change in SUVmax and language expression between the first and second PET were 0.4 (p = 0.01). Our results indicate that chronic severe traumatic head injury patients have changed brain glucose metabolism.