Takayuki Ohira

Abnormal muscle response (lateral spread) and F-wave in patients with hemifacial spasm

In patients with hemifacial spasm (HFS) the spasm is due to cross compression of the facial nerve by a blood vessel and microvascular decompression (MVD) has proved to be a successful treatment. Abnormal muscle response (AMR), which can be elicited by one facial nerve branch stimulation in muscles innervated by other branches of the facial nerve, is specific for patients with HFS, and the AMR consists of a constant response occurring about 10 ms after stimulus and an afterdischarge with long duration (variable response, autoexcitation). The F-wave in facial muscles is a small recurrent discharge that antidromically propagates to the facial motonucleus and returns orthodromically down the same axon. We measured the AMRs and F-waves of facial muscles in HFS patients in order to investigate the relationship of both potentials and the origin of the AMRs. We obtained facial nerve evoked electromyograms from 10 HFS patients. The afterdischarges of the AMRs and the enhanced F-waves were always elicited at the same time by marginal mandibular branch stimulation of the facial nerve. There was a linear correlation between the duration of these two potentials in each case. Between the duration of the afterdischarge of the AMRs elicited in the mentalis muscles by the zygomatic branch stimulation of the facial nerve and that of the F-waves in the mentalis muscles, there was also a linear correlation in 10 cases. These results suggest that the F-wave and the afterdischarge have the same origin and that the AMR is an exaggerated F-wave.

Four subtypes of petroclival meningiomas: differences in symptoms and operative findings using the anterior transpetrosal approach

SummaryBackground. Petroclival meningiomas are vaguely defined as tumours arising from the antero-medial zone to the internal auditory meatus. This report subclassifies petroclival meningiomas based on their origin determined by using radiological and intra-operative findings.Method. Ninety-one patients with petroclival meningioma underwent surgery via the anterior transpetrosal approach. The Meckel’s cave was routinely opened. Tumour origin was classified into four subtypes according to the main attachment and trigeminal nerve deviation into, upper clivus (UC), cavernous sinus (CS), tentorium (TE), and petrous apex (PA). Their characteristic clinical symptoms and anatomical features were investigated.Findings. The characteristic symptom was ataxia in the UC type (37.5%), abducens nerve palsy in the CS type (64.3%) and trigeminal neuropathy, mainly neuralgia in the PA type (80.0%) with a higher statistical difference from other subtypes. The rate of tumour invasion into Meckel’s cave reached 70.3% in average, with the lowest rate in the PA type (25.0%). The rate of middle fossa extension was the highest in the TE type (59.5%). The middle fossa approach was considered to be ideal for UC and TE types because of easier access to the Meckel’s cave. Radical dissection without complications was difficult in the CS type. Both the anterior transpetrosal approach and the lateral suboccipital approach could be indicated in the PA type due to the rare invasion of Meckel’s cave and middle fossa, and frequent extension into the internal auditory meatus.Conclusions. This classification is useful to predict the relation between the tumour and the cranial nerves based on symptoms and images. The anterior transpetrosal approach could be used for all four subtypes and with an absolute indication in the UC and TE types showing middle fossa extension.

Nationwide investigation of the current status of therapeutic neuroendoscopy for ventricular and paraventricular tumors in Japan: Clinical article

OBJECT The authors report their investigation on the current status of neuroendoscopic biopsy for ventricular and paraventricular tumors as well as treatment for associated hydrocephalus in Japan. METHODS Patients who had undergone therapeutic neuroendoscopy between 2005 and 2009 were included in this study. The main items examined were age; sex; localization of tumor; pathological diagnosis using biopsy; the presence, treatment, and efficacy of treatment of associated hydrocephalus; perioperative complications; activities of daily living (ADL) before and after therapeutic neuroendoscopy; and the presence of dissemination during the postoperative course. RESULTS Seven hundred fourteen patients from 123 sites (462 male and 252 female patients, mean age 33.3 years) were enrolled. Localization of the tumor was mainly classified into the lateral ventricle in 91 patients, the third ventricle in 339, the fourth ventricle in 18, the suprasellar region in 75, and other paraventricular areas in 191 patients. The most commonly observed tumors were germ cell tumors in the third ventricle (177 cases [39%]), cystic lesions in the suprasellar region (56 cases [75%]), and astrocytic tumors in the thalamus-basal ganglia (71 cases [38%]). Although 641 (92.8%) of 691 patients could receive neuroendoscopic diagnosis using biopsy, the diagnosis obtained with endoscopic biopsy differed from the final diagnosis based on subsequent craniotomy in 18 patients and clinical course in 3 patients. Of these 21 patients, 7 had astrocytic tumors, 4 had pineal tumors, 6 had germ cell tumors, and 4 had other tumors. The final diagnostic accuracy rate was 89.7%. Associated hydrocephalus was observed in 517 patients (72.4%), of whom 316 and 39 underwent third ventriculostomy and fenestration of the septum, respectively. The response rates were 96.2% and 89.7%, respectively. Third ventriculostomy was required for recurrence of hydrocephalus in 41 patients (13.0%), and the long-term response rate was therefore 83.2% (263 of 316 patients). Perioperative complications other than fever, such as new onset of or progressive hydrocephalus, infection due to CSF leakage, and bleeding in the ventricle or tumor, were found in 81 patients (11.3%). The median Karnofsky Performance Scale score before endoscopic surgery was 80, but it increased to 90 after surgery. The score was thus significantly increased after surgery (p < 0.0001, Mann-Whitney U-test). Activities of daily living after surgery decreased due to perioperative complications in 15 patients (2.1%). The incidence of new dissemination after endoscopic biopsy was 6.8% and not high compared with routine surgical treatment. CONCLUSIONS The authors concluded that neuroendoscopic diagnosis using biopsy for ventricular and paraventricular tumors is adequately accurate and safe. It was demonstrated that endoscopic procedures play important roles not only in the treatment of hydrocephalus associated with intra- and paraventricular tumors but also in significantly improving ADL. Furthermore, the long-term outcome of endoscopic third ventriculostomy was clearly favorable.

Computed tomographic analysis of hemifacial spasm: narrowing of the posterior fossa as a possible facilitating factor for neurovascular compression.

Hemifacial spasm can be caused by vascular compression of the facial nerve at the root exit zone from the brainstem. Several case reports suggest that narrowing of the cerebellopontine angle cistern caused by Pagets disease, abnormal elevation of the petrous bone caused by hyperplasia, or contralateral acoustic neurinoma may increase the chance of vascular compression of the facial nerve. Therefore, posterior fossa narrowness has been evaluated in 34 patients with hemifacial spasm by measuring the petrous angle and pons diameter index to elucidate whether narrowing of the posterior fossa can act as a facilitating factor for neurovascular compression. The petrous angle in the hemifacial spasm group was significantly smaller than that in the control group, which consisted of 33 patients with an unruptured supratentorial aneurysm, and the pons diameter index in the hemifacial spasm group was significantly greater than that in the control group. These results indicate that the cerebellopontine angle cistern of patients with hemifacial spasm is narrower resulting in more crowded cranial nerves and vascular structures compared with patients without hemifacial spasm. The narrowness of the cerebellopontine angle cistern may be a possible factor in facilitating neurovascular compression in hemifacial spasm.

TMS Orientation for NIRS-Functional Motor Mapping

SummaryFunctional near-infrared spectroscopic imaging (NIRS imaging) has the potential to elucidate the relationship between neuronal activity and oxygenation responses. However, its signal specificity to the functional cortex is sometimes spoiled by its rough spatial resolution. In this study we incorporated transcranial magnetic stimulation (TMS) motor mapping into an NIRS imaging study to enhance spatial specificity to the functional cortex. Distinctive biphasic responses in the cortical oxygenation status were observed in the center of the primary motor cortex during a motor task. The early response phase, occurring within 1 to 3 seconds after task initiation, represents a cortical deoxygenation which consists of a significant increase in deoxygenated hemoglobin concentration (HbR) and a nonsignificant decreasing tendency in oxygenated hemoglobin concentration (HbO2). The delayed response phase represents an excess of incoming blood flow, which appears as an increase in HbO2/total Hb (tHb) and a decrease in HbR following the early response. In the surrounding area, cortical oxygenation change showed a monophasic response consisting of an increase in HbO2/tHb and a decrease in HbR. Combining TMS mapping with NIRS imaging enabled us to specify the cortex with the strongest functional activity.

Long-term surgical outcome and biological prognostic factors in patients with skull base meningiomas

OBJECT Although gross-total resection (GTR) is a preferable treatment for skull base meningiomas, subtotal resection (STR) with or without radiation therapy can be considered as an alternative treatment for patients at considerable surgical risk. The long-term prognosis of such patients might be related to the biological activity of the tumor. This study examined predictors of progression-free survival (PFS) and sought to determine the optimal treatment strategies, focusing on the pathobiological findings of skull base meningiomas. METHODS This study included 281 patients with skull base meningiomas (mean follow-up period 88.4 months). Risk factors for tumor progression were examined using a multivariate analysis. The PFS and overall survival (OS) rates were evaluated using the Kaplan-Meier method. The functional outcomes of the patients were measured using the Karnofsky Performance Scale (KPS). RESULTS The 10-year PFS and OS rates were 66.4% and 97.4%, respectively. Overall, 83.3% of patients achieved a favorable outcome, that is, an improved or unchanged KPS score. The extent of resection, additional radiotherapy, histological grade, MIB-1 index, and p53-positive rate were significantly associated with PFS. The PFS of patients undergoing STR without radiation therapy was significantly shorter than that of either those undergoing STR with radiation therapy or GTR, while no statistical difference was observed between the latter 2 groups. Among the patients undergoing STR with pathobiological risk factors (histological grade, MIB-1 index, and p53-positive rate), the PFS of the patients who received radiation therapy was better than that of those who did not receive radiation therapy. Among the patients undergoing STR without such risk factors, the PFS was not significantly different between patients who received radiation therapy and those who did not. CONCLUSIONS For patients with skull base meningiomas, a GTR is desirable and additional radiation therapy after STR may contribute to a longer PFS. Additional radiation therapy should be recommended, especially for patients with pathobiological risk factors, but not necessarily for those without such risks.

Antihistamine effects on prefrontal cortex activity during working memory process in preschool children: a near-infrared spectroscopy (NIRS) study.

Histamine H1 receptor antagonists (antihistamines) are widely used for the treatment of allergic disorders in young children. This study examined the effects of antihistamine on prefrontal cortex activity in preschool children using near-infrared spectroscopy (NIRS), an emerging brain-imaging method suitable for psychological experiments, especially in young children. We examined the changes of oxygenated hemoglobin concentration in the prefrontal cortex while children performed a spatial working memory task, 3h after taking a first-generation antihistamine (ketotifen), second-generation antihistamine (epinastine), or placebo. Fifteen healthy preschool children (mean age, 5.5 years) participated. Ketotifen significantly impaired behavioral performance and cortical activation at the lateral prefrontal cortex in the working memory task, compared with epinastine and placebo. There were no sedative effects on neural response or behavioral performance after epinastine administration. This paper demonstrates for the first time differential sedation effects of first- and second-generation antihistamines on brain hemodynamic response in young children. Also discussed is the utility of the NIRS technique in neuropsychopharmacological studies of children.

Effect of repetitive stimulation on lateral spreads and F-waves in hemifacial spasm

The lateral spread (LS) response, which can be elicited in muscles innervated by other branches of the facial nerve, is electromyographycally specific for patients with hemifacial spasm (HFS), occurring about 10 ms after stimulus. The F-wave in facial muscles, which is a late response that antidromicaly propagates to the facial motonucleus and returns orthodromicaly down the same axon, revealed a trend toward enhancement in patients with HFS. The LSs were facilitated by repetitive stimulation during the microvascular decompression (MVD) operation, which has proved to be a successful treatment, and the F-waves were also facilitated by repetitive stimulation on the spasm side more than on the normal side. Greater facilitation of these responses was in direct proportion to higher stimulation rates and greater numbers of stimulations. The repetitive stimulation of the facial nerve may result in activation of the motoneuron pool and in the lowering of the threshold of somatic membranes. These results support the hypothesis that hemifacial spasm is caused by hyperexcitability of the facial motonucleus, which is increased by antidromic repetitive stimulation.

F-wave in patients with hemifacial spasm: observations during microvascular decompression operations.

In patients with hemifacial spasm (HFS), the spasm is due to cross compression of the facial nerve by a blood vessel. There are currently two hypotheses how the cross compression can cause HFS: 1. the spasm is caused by ephaptic transmission and hyperexcitability at the site of compression; and 2. the spasm is caused by hyperexcitability in the facial motonucleus. In peripheral nerves, F-waves, which result from the backfiring of antidromically activated anterior horn cells, have been proposed as indices of anterior horn cell excitability. Enhancement of the F-waves in facial muscles also indicates increased excitability of the facial motonucleus. On the other hand, abnormal muscle response (AMR), which can be elicited by stimulating one branch of the facial nerve and recording electromyographically from muscles innervated by other branches of the facial nerve, is specific for patients with HFS. We have therefore measured the AMRs and the F-waves in the facial muscle of HFS patients under anesthesia in order to investigate the excitability of the facial motonucleus. We obtained facial nerve evoked electromyograms from 14 HFS patients during microvascular decompression (MVD) operation. The F-waves, obtained with surface electrodes from the mentalis muscle, were defined as the second response after the M-wave. The F-waves in facial muscles cannot usually be elicited during surgical anesthesia using inhalation anesthetics. However, the F-waves were elicited on the spasm side in 10 out of 14 patients with HFS and the F-waves disappeared after MVD under anesthesia, as the early responses (R1) of the blink reflex were elicited on the spasm side before MVD under anesthesia. The F-waves elicited during anesthesia were suppressed significantly, compared with those before MVD. These results suggest that excitability in facial motonucleus increased on the spasm side.

Repetitive Transcranial Magnetic Stimulation Once a Week Induces Sustainable Long-Term Relief of Central Poststroke Pain

Central poststroke pain is a serious problem for some patients after stroke. Repetitive transcranial magnetic stimulation (rTMS) has been reported to relieve poststroke pain but its efficacy is still controversial. We tested the possibility that rTMS, when applied once a week, would induce sustainable relief of poststroke pain.