Risk of Bone Wax Migration During Retrosigmoid Craniotomy for Microvascular Decompression: Case-Control Study.

BACKGROUND AND OBJECTIVES: Bone wax is a flexible hemostatic agent commonly used for surgery in the posterior cranial fossa to control bleeding from the mastoid emissary vein. A large amount of bone wax can migrate into the sigmoid sinus through the mastoid emissary canal (MEC). We aimed to identify clinical factors related to intraoperative bone wax migration through the MEC during microvascular decompression (MVD) surgery, which may result in sigmoid sinus thrombosis. METHODS: We retrospectively collected the clinical data of patients with trigeminal neuralgia, hemifacial spasm, or trigeminal neuralgia accompanied by painful tic convulsif who underwent MVD. Basic information and the residual width and length (from the bone surface to the sigmoid sinus) of the MEC on computed tomography images were collected. We compared the collected clinical data between 2 groups of cases with and without intraoperative bone wax migration in the sigmoid sinus. RESULTS: Fifty-four cases with intraoperative bone wax migration and 187 patients without migration were enrolled. The t -test revealed significant differences in the width and length of the MEC ( P = .013 and P = .003, respectively). These variables were identified as significant factors in predicting intraoperative bone wax migration using multivariate logistic regression analysis. CONCLUSION: The large size of the MEC may be related to intraoperative bone wax migration into the sigmoid sinus in MVD. Neurosurgeons should be aware of these risks. Bone wax should be applied appropriately and hemostasis should be considered to control bleeding from the mastoid emissary vein in patients with a large MEC.

Acute Brainstem Dysfunction Caused by Cavernous Sinus Dural Arteriovenous Fistula.

Symptoms of cavernous sinus dural arteriovenous fistula depend on the drainage patterns and are very diverse. Among these, brainstem dysfunction is a rare but serious complication. Here, we describe a case with isolated and rapidly progressive brainstem dysfunction due to cavernous sinus dural arteriovenous fistula. An 80-year-old woman presented with a 2-day history of progressive gait disturbance. Neurological examination revealed mild confusion, dysarthria, and left hemiparesis. Magnetic resonance imaging (MRI) revealed pontine swelling without evidence of infarction. Magnetic resonance angiography suggested a faint abnormality near the cavernous sinus. Dural arteriovenous fistula was suspected, and digital subtraction angiography was planned for the next day. Her condition had progressed to coma by the next morning. Pontine swelling worsened, and hyperintensity appeared on diffusion-weighted imaging. Digital subtraction angiography revealed a right-sided cavernous sinus dural arteriovenous fistula with venous reflux into the posterior fossa. Orbital or ocular symptoms had preceded brainstem symptoms in all nine previously reported cases, but brainstem symptoms were the only presentation in our case, making the diagnosis difficult. Some dural arteriovenous fistulas mimic inflammatory diseases when the clinical course is acute. Prompt diagnosis using enhanced computed tomography or MRI and emergent treatment are needed to avoid permanent sequelae.

Vascular Reconstruction for Radiation-induced Bilateral Internal Carotid Artery Occlusion and Unilateral External Carotid Artery Stenosis by a Combination of Surgical and Endovascular Method: Case Report.

We present a case of a 63-year-old male presenting with right hemiparesis and diagnosed as cerebral infarction. He had a previous history of left pharyngeal carcinoma, which was treated by radial dissection and radiation therapy 10 years before. Magnetic resonance imaging (MRI) showed multiple cerebral infarction in the bilateral cerebral hemisphere, predominantly on the left. Cerebral angiography showed occlusion of bilateral internal carotid arteries and severe stenosis at the orifice of the left external carotid artery (ECA). Single photon emission tomography (SPECT) showed reduced cerebral blood flow and decreased cerebral vascular reserve in the bilateral anterior cerebral artery and left middle cerebral artery territories. He was successfully treated by a combination of carotid stenting for the left ECA and left superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis. He did not have further ischemic symptom for more than 2 years. Radiation-induced carotid vasculopathy often involves multiple arteries and treatment is often complex and difficult. Safer and less invasive treatment strategy should be considered using both endovascular and direct surgery.

Role of posterior parietal cortex in reaching movements in humans: clinical implication for 'optic ataxia'.

OBJECTIVE: To clarify the spatio-temporal profile of cortical activity related to reaching movement in the posterior parietal cortex (PPC) in humans. METHODS: Four patients with intractable partial epilepsy who underwent subdural electrode implantation were studied as a part of pre-surgical evaluation. We investigated the Bereitschaftspotential (BP) associated with reaching and correlated the findings with the effect of electrical stimulation of the same cortical area. RESULTS: BPs specific for reaching, as compared with BPs for simple movements by the hand or arm contralateral to the implanted hemisphere, were recognized in all patients, mainly around the intraparietal sulcus (IPS), the superior parietal lobule (SPL) and the precuneus. BPs near the IPS had the earlier onset than BPs in the SPL. Electrical stimulation of a part of the PPC, where the reach-specific BPs were recorded, selectively impaired reaching. CONCLUSIONS: Intracranial BP recording and cortical electrical stimulation delineated human reach-related areas in the PPC. SIGNIFICANCE: The present study for the first time by direct cortical recording in humans demonstrates that parts of the cortices around the IPS and SPL play a crucial role in visually-guided reaching.

Recipient targeting for revascularization using pulsed Doppler ultrasonography for the treatment of an intracranial giant aneurysm.

Aneurysmal occlusion after blood flow revascularization is a promising management strategy for the treatment of intracranial giant aneurysms. However, it is necessary to design robust revascularization for preventing postoperative flow-related infarctions caused by abrupt occlusion of the parent vessels. Since direct anastomosis of donor vessels to recipient vessels near giant aneurysms is often difficult, it is preferable to select cortical recipient branches away from the aneurysm, thus providing a sufficient working space for the surgeon. In this paper, the authors' goal was to identify distal cortical recipient arteries on the brain surface, based on pulsed Doppler ultrasonography analysis of blood flow alteration after temporary closure of the efferent vessels. This method is used to visualize the area around the sacrificed vessels, omits intraoperative arteriography or the risk of a surgical trace of the vessels by dissecting the distal sulci, and could be advantageous for necessary and sufficient revascularization.

[MEP showed peculiar changes after temporal ICA occlusion in aneurysm surgery, in spite of cerebral tolerance to preoperative test occlusion. A case report].

Preoperative balloon test occlusion (BTO) has generally been used to predict intraoperative tolerance for temporary vascular occlusion to prevent a premature rupture during aneurysm surgery or to perform complete treatment for large aneurysms. We encountered a case in which intraoperative motor evoked potential (MEP) revealed peculiar changes after temporal occlusion of the internal carotid artery during aneurysm surgery, in spite of showing sufficient tolerance to preoperative BTO. We emphasize the importance of intraoperative MEP monitoring, even if patients have shown tolerance in preoperative BTO.

Negative motor seizure arising from the negative motor area: is it ictal apraxia?

PURPOSE: Seizure manifesting motor arrest, that is, negative motor seizure (NMS), is a rare epileptic condition in which only inability to conduct voluntary movements or praxis is produced, although consciousness is preserved. The negative motor area (NMA) seems to be responsible, but its generator mechanism has not yet been clarified. PATIENTS AND METHODS: Three patients manifesting NMS were investigated. Two patients (ages 33 and 17) with intractable frontal lobe epilepsy had subdural grid implantation for epilepsy surgery, and one (age 77) had scalp electroencephalography (EEG) monitoring. RESULTS: Ictal semiologies commonly observed, at least in the two patients, were found as follows; (1) indescribable or ill-localized aura, (2) repetitive involuntary vocalization, (3) inability to speak, (4) inability to move the extremities, and (5) subsequent evolution to positive motor seizures. Awareness and comprehension were preserved throughout the episode before generalized seizures. In two patients with epicortical EEG recording, ictal activity arose from the lateral NMA in one, and from the rostral supplementary motor area in the other. Cortical stimulation at NMA in one patient elicited symptoms identical to NMS. Another patient had scalp EEG and magnetic resonance imaging (MRI) abnormality, both suggesting the epileptogenic focus in the mesial frontal area. CONCLUSION: We showed that (1) NMS was a rare condition in patients with seizure focus in the frontal lobe, and (2) that the NMA was responsible for the symptoms. The documented state in the present study may reflect ictal apraxia, but it requires further investigation.

Improved cerebral function in mesial temporal lobe epilepsy after subtemporal amygdalohippocampectomy.

The functional changes that occur throughout the human brain after the selective removal of an epileptogenic lesion remain unclear. Subtemporal selective amygdalohippocampectomy (SAH) has been advocated as a minimally invasive surgical procedure for patients with medically intractable mesial temporal lobe epilepsy (MTLE). We evaluated the effects of subtemporal SAH on cerebral glucose metabolism and memory function in 15 patients with medically intractable MTLE with hippocampal sclerosis using [(18)F]-fluorodeoxyglucose PET (FDG-PET) and the Wechsler Memory Scale-Revised. The patients were evaluated before and 1-5 years (mean 2.6 years) after surgery. In patients with MTLE of the language-dominant hemisphere, the basal temporal language area was preserved by this surgical approach. Voxel-wise comparison of FDG-PET images was conducted using SPM5 to identify the brain regions showing postoperative changes in glucose metabolism (height threshold, P = 0.01 corrected for multiple comparisons; extent threshold, 100 voxels). During spatial normalization of the postoperative FDG-PET images, we used cost-function masking to minimize any inappropriate image distortion as a result of the abnormal signal within the surgically resected region. Postoperative glucose metabolism increased in extratemporal areas ipsilateral to the affected side, such as the dorsolateral prefrontal cortex, and the dorsomedial and ventromedial frontal cortices. Glucose metabolism also increased in the bilateral inferior parietal lobules and in the remaining temporal lobe regions remote from the resected mesial temporal region, such as the superior temporal gyrus and the temporal pole. By contrast, postoperative glucose metabolism decreased only in the mesial temporal area adjacent to the resected region. Postoperative verbal memory, delayed recall and attention/concentration scores were significantly better than preoperative scores regardless of the resected side. This study suggests that the selective removal of the epileptogenic region in MTLE using a subtemporal approach improved cerebral glucose metabolism in the areas receiving projections from the affected mesial temporal lobe. Cognitive improvement might result from a combination of good seizure control and minimizing the regions of the brain with postoperative functional impairment.

Successful "blind-alley" formation with bypass surgery for a partially thrombosed giant basilar artery tip aneurysm refractory to upper basilar artery obliteration. Case report.

Partially thrombosed giant aneurysms that are located at the basilar artery (BA) bifurcation and are not amenable to clip application are among the most challenging lesions for neurosurgeons. They compress vital structures such as the brainstem and the thalamus, and the prognosis is extremely poor when they are left untreated. Although obliteration of the upper BA is a promising approach for these aneurysms, some lesions are refractory to this treatment, and effective additional strategies have not been clearly established. The authors report a case treated by placement of clips in the unilateral posterior cerebral artery (PCA) and posterior communicating artery as well as by superficial temporal artery-PCA bypass after unsuccessful upper BA obliteration. Complete thrombosis and dramatic shrinkage of the aneurysm were obtained.

Comparison between motor evoked potential recording and fiber tracking for estimating pyramidal tracts near brain tumors.

OBJECT: The utility of subcortical electrical stimulation and fiber tracking were compared to estimate the pyramidal tract near brain tumors. METHODS: In 22 patients, the white matter at the bottom of a tumor was electrically stimulated near the fiber tracking of the pyramidal tract shown on a neuronavigation system. The distance between the center of the fiber tracking of these tracts and the stimulated region was measured and defined as the motor evoked potential (MEP) response. The MEP was consistently produced at distances less than 7 mm (six patients), but was consistently absent at distances more than 13 mm (seven patients) from the fiber tracking of the pyramidal tracts. In the nine patients in whom the distance was between 8 and 12 mm, an MEP was elicited when stimulation was applied at the level of the corona radiata. Motor function was preserved or even improved with appropriate tumor resection in all patients. CONCLUSIONS: The anteroposteriorly running superior longitudinal fasciculus could cause complications in the fiber tracking of upper-extremity motor pathways at the level of the corona radiata. During resection of tumors located near the corona radiata, subcortical electrical stimulation should be applied at some distance from the pyramidal tract, as estimated by fiber tracking.

Fibers from the dorsal premotor cortex elicit motor-evoked potential in a cortical dysplasia.

OBJECTIVE: To identify the fibers originating from the dorsal premotor cortex (dorsal PMC) that contribute to motor-evoked potentials (MEP), we have applied integrated functional neuronavigation and awake surgery during removal of an epileptic cortical dysplasia located in the right premotor cortex. METHODS: Chronic subdural electrodes were employed for functional mapping during a routine invasive evaluation for intractable epilepsy. After the fibers originating from the dorsal PMC were plotted into the tractography-integrated functional neuronavigation, subcortical MEPs and clinical symptoms were examined during resection of the epileptogenic dorsal PMC. RESULTS: During removal of the epileptogenic area, MEPs were elicited by electrical stimulation of the fibers originating from the dorsal PMC, which were separated from the pyramidal tracts from the precentral gyrus. Resection of the dorsal PMC and its fibers caused a transient dysmetric movement of the left toe without motor weakness. CONCLUSION: Functional corticospinal tract fibers originating from the dorsal PMC can be defined and removed safely under local anesthesia with the aid of integration of functional neuronavigation and subcortical electrical stimulation.

Heterogeneous epileptogenicity and cortical function within malformations of cortical development: a case report.

The authors report a 24-year-old patient with intractable partial epilepsy and massive malformations of cortical development (MCD). Subdural EEG recordings of habitual seizures showed heterogeneous epileptogenicity, and visual evoked potential was recorded within the MCD just adjacent to the most active epileptogenic focus. Resection of the small cortical area presumably with core epileptogenicity, while sparing the cortical functional area, improved seizure outcome without any postoperative functional deficits.

Subtemporal hippocampectomy preserving the basal temporal language area for intractable mesial temporal lobe epilepsy: preliminary results.

PURPOSE: Decline in verbal memory as a surgical complication remains an unresolved problem in mesial temporal lobe epilepsy. Some areas in the temporal lobe associated with the language function, often including the basal temporal language area, have been removed or transected by conventional surgical procedures. The authors defined the basal temporal language area and removed only the epileptogenic zone with a subtemporal approach. METHODS: The basal temporal language area was evaluated by using long-term subdural electrodes in five patients with language-dominant-side mesial temporal lobe epilepsy. While preserving this area, the hippocampus and the parahippocampal gyrus were removed by using a combined subtemporal, transventricular, transchoroidal fissure approach. Verbal memory performance was assessed with the Wechsler Memory Scale-Revised (WMS-R) before and after the operation. RESULTS: The basal temporal language area, defined as a part of the inferior temporal gyrus, the fusiform gyrus, and the parahippocampal gyrus, was spared by entering the temporal horn via collateral sulcus. Verbal memory was significantly improved by 3 months and 1 year after the operation. CONCLUSIONS: In language-dominant-side mesial temporal lobe epilepsy, preserving the basal temporal language area would have potential to improve verbal memory outcomes after removal of the epileptogenic zone.

Generators and temporal succession of giant somatosensory evoked potentials in cortical reflex myoclonus: epicortical recording from sensorimotor cortex.

OBJECTIVE: To clarify the generator mechanism of giant somatosensory evoked potentials (giant SEPs) and the hyperexcitability of primary somatosensory and motor cortices (SI and MI). METHODS: In a patient with intractable focal seizures manifesting cortical reflex myoclonus of the left foot, giant SEPs to left tibial nerve stimulation were epicortically recorded as a part of presurgical evaluation with subdural electrodes. RESULTS: In the single pulse SEPs, enlarged P1-N1 components were observed at the foot area of the SI and MI (86.5-258.8 microV, respectively), and the peak latencies were always shorter at SI than at MI by 6 ms. Similar findings were obtained for peroneal and sural nerve stimulation. In the paired pulse SEPs, the second response was less suppressed, as compared to other interstimulus intervals (ISIs), with ISIs of 40 and 200 ms both at SI and MI. CONCLUSIONS: In this particular patient, cortical hyperexcitability to somatosensory stimuli seems to originate from SI but subsequently both SI and MI are responsible for the generation of giant SEPs and cortical reflex myoclonus. SIGNIFICANCE: Somatosensory and primary motor cortices both generated enhanced early cortical components of SEPs, most likely by enhancing the latter by the former.

Evidence for a wide distribution of negative motor areas in the perirolandic cortex.

OBJECTIVE: The perirolandic regions were studied by extensive electrical stimulation to clarify the topography and somatotopic distribution of negative motor areas (NMAs) and examine the clinical significance of these areas. METHODS: We evaluated the cortical function elicited by electrical stimulation in 30 patients with tumors or intractable epilepsy. The somatotopic distribution of NMAs was examined by localizing these regions using Talairach's bicommissural reference system. NMAs within the lesions of two patients were removed under local anesthesia. RESULTS: We obtained negative motor responses following the stimulation of 30 electrodes in 15 patients. On the lateral brain surface, the majority of NMAs for the upper extremities were distributed broadly throughout the premotor cortex, while NMAs for the tongue were only found in the inferior frontal gyrus of the dominant hemisphere. During removal of the NMAs within the lesions of two patients, we documented transient hand clumsiness in one patient. CONCLUSIONS: NMAs were widely distributed throughout the perirolandic area, as well as the previously reported regions in the inferior frontal gyrus. These areas likely function in the control of skilled movements; dysfunction of such movements transiently follows resection of these regions, but is subsequently well compensated for after surgery. SIGNIFICANCE: The localization and consequences of resection of NMAs suggests their clinical significance in motor control.

In vivo epileptogenicity of focal cortical dysplasia: a direct cortical paired stimulation study.

PURPOSE: Alternation of the intracortical inhibitory and excitatory mechanisms in focal cortical dysplasia (FCD) has not been well elucidated in vivo in humans. We investigated in vivo alternation of these mechanisms in epileptogenesis of FCD by means of paired-pulse direct cortical electrical stimulation. METHODS: A 31-year-old man with FCD at the left foot primary somatosensory (SI) and motor areas who underwent invasive monitoring with subdural electrodes was studied. By means of subdural electrodes, paired-pulse electrical stimulation was performed at the epileptic focus (foot SI) and control cortex (hand SI) with interstimulus interval (ISI) of 1-100 ms. Instead of using motor evoked potentials to investigate the degree of cortical excitability in response to motor cortex stimulation, we evaluated the size change of corticocortical evoked potentials (CCEPs), which are elicited at the adjacent cortex by direct cortical stimulation via fiber projection and thus reflect direct and indirect excitation of corticocortical projection neurons at the site of stimulation. RESULTS: During the interictal state, paired-pulse stimulation of the focus revealed abnormally enhanced intracortical inhibition at ISI of 1-10 ms (maximum, 22%) compared with control stimulation of the hand SI (ISI of 1-2 ms; maximum, 18%) (p < 0.01). While the patient was having the somatosensory aura that later evolved into the left-leg clonic seizure, single and paired stimulation at the focus showed increased cortical excitability (enlarged CCEP) and decreased intracortical inhibition, respectively. CONCLUSIONS: During the aura, interictally enhanced intracortical inhibition at the focus was replaced by increased cortical excitability and decreased intracortical inhibition, suggesting increased net intrinsic epileptogenicity during seizure generation in this patient with FCD.

Endotracheal tube electrodes to map and monitor activities of the vagus nerve intraoperatively. Technical note.

Difficulty swallowing due to damage of the vagus nerve is one of the most devastating complications of surgery in and around the medulla oblongata; therefore, intraoperative anatomical and functional evaluation of this nerve is crucial. The authors applied endotracheal tube surface electrodes to record electromyography (EMG) activity from vocal cords innervated by the vagus nerve. The vagal nucleus or rootlet was electrically stimulated during surgery and vocalis muscle EMG activities were displayed by auditory and visual signals. This technique was used successfully to identify the vagus motor nerve and evaluate its integrity during surgery. The advantages of this method compared with the use of needle electrodes include safe simple electrode placement and stable recording during surgery. In cases involving a pontine cavernoma pressing the nucleus or a jugular foramen tumor encircling the rootlet, this method would be particularly valuable. Additional studies with a larger number of patients are needed to estimate the significance of this method as a means of functional monitoring to predict clinical function.

[Early application of the lung protective ventilation strategy at different stages in two ARDS patients].

We experienced 2 patients with acute respiratory distress syndrome (ARDS) from pneumonia after intervention for subarachnoidal hemorrhage. We applied lung protective ventilation strategy (LPVS) on both cases: a tidal volume less than 6 ml x kg(-1) ideal body weight and PEEP at 10-15 cmH2O. Although etiology and degree of hypoxia were very similar in two patients when ARDS was diagnosed, clinical course was quite different. The patient in whom LPVS had been started on the 5th day of ARDS required mechanical ventilation of 23 days. In contrast, another patient in whom LPVS had been started on the 16th day of ARDS required mechanical ventilation of 219 days. PaCO2 during LPVS with permissive hypercapnia in the latter patient increased up to 161 mmHg but no adverse effect was observed. These cases suggest that early application of the LPVS may be important to improve respiratory outcomes of ARDS patients.