Hisao Hirai

Correlated long-term increase of brain-derived neurotrophic factor and Trk B proteins in enlarged granule cells of mouse hippocampus after kainic acid injection.

Our previous studies have shown that a single injection of kainic acid into the dorsal hippocampus of adult mice resulted in hypertrophy of the dentate gyrus granule cells. This hypertrophy was correlated with a long-lasting increase of brain-derived neurotrophic factor messenger RNA, and prevented by anti-sense brain-derived neurotrophic factor oligonucleotide treatment. These results suggest that an increase of brain-derived neurotrophic factor messenger RNA may be a major trigger of granule cells enlargement. However, the level of messenger RNA of Trk B, the high-affinity receptor of brain-derived neurotrophic factor, was not increased significantly, raising the question of whether increased brain-derived neurotrophic factor messenger RNA level leads actually to an increased protein production. The objective of the present study was to examine this; changes in contents of brain-derived neurotrophic factor and TrkB protein were monitored by immunohistochemistry during kainic acid-induced hypertrophy. Results show that immunoreactivities of brain-derived neurotrophic factor and Trk B were present in enlarged granule cells. These immunoreactivities increased from two to 16 weeks after kainic acid injection and were maintained up to 12 months. Simultaneous increases of brain-derived neurotrophic factor messenger RNA and protein, and of TrkB protein were coupled tightly to the chronology of granule cell enlargement, suggesting that the action of brain-derived neurotrophic factor in the induction and maintenance of kainic acid-induced granule cells enlargement is likely to be mediated by TrkB. The discrepancy between the previously described lack of increase of TrkB messenger RNA and the herein observed increase of the protein further reveals the existence of translational regulations of the receptor messenger RNA.

Long-term increase of GluR2 α-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor subunit in the dispersed dentate gyrus after intrahippocampal kainate injection in the mouse

Intrahippocampal injection of a subtoxic dose of kainate in mice has been shown to induce a dispersion of granule cells of the dentate gyrus, which is a characteristic morphological change often seen in human hippocampal sclerosis. In addition, it has been shown recently that such injections lead to recurrent hippocampal seizures and changes in glucose metabolism, which are reminiscent of temporal lobe epilepsy. Previous reports on human hippocampal sclerosis have shown an increase of the expression of the GluR2 alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate subunits in the dispersed granule cell somata. However, no such changes have been observed so far in animal models of epilepsy with hippocampal sclerosis. In this study, the expression of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor subunits was examined by immunohistochemistry following intrahippocampal injection of kainate in mice and rats. In mice, such injection induced a persistent increase of GluR2 immunoreactivity in the granule cells for up to 180 days. By contrast, GluR1 immunoreactivity was transiently increased during the first four days after the injection and progressively decreased thereafter. By contrast, intrahippocampal injection of kainate in rats did not result in granule cell dispersion and no changes in GluR1 immunoreactivity or GluR2 immunoreactivity were observed. These results show that, in addition to morphological, clinical and metabolical similarities, intrahippocampal injection of kainate results in a persistent increase of GluR2 associated with granule cell dispersion, as in human hippocampal sclerosis. These data suggest the existence of common mechanisms between granule cell dispersion and regulation of GluR2 subunits associated with hippocampal sclerosis.

Ocular neuromyotonia treated by microvascular decompression: usefulness of preoperative 3D imaging: case report.

Ocular neuromyotonia is a rare ocular motility disorder characterized by involuntary contraction of extraocular muscles resulting in paroxysmal diplopia. Although ocular neuromyotonia is reported as a rare complication after radiation therapy, there are a few cases of ocular neuromyotonia in the absence of irradiation. In the reported cases the possibility of vascular compression has been suggested on radiological imaging. The authors report a case of ocular neuromyotonia treated by microvascular decompression of the third cranial nerve, supporting the hypothesis that neurovascular compression may play a role in its pathogenesis. The usefulness of preoperative 3D imaging for microvascular decompression is also discussed.

Trochlear Nerve Schwannoma Treated with Gamma Knife after Excision: A Case Report and Review of the Literature

Trochlear nerve schwannomas are extremely rare. We present a surgically excised case of trochlear nerve schwannoma followed by Gamma Knife (ELEKTA, Stockholm, Sweden) after histologic confirmation. A 52-year-old man presented with diplopia, gait disturbance, and sensory disturbance. Magnetic resonance imaging demonstrated a large cystic mass at ambient cistern on the right side. Subtotal excision followed by Gamma Knife surgery was undertaken. His neurologic symptoms disappeared with radiologic reduction in size at 15-month follow-up. Because Gamma Knife can manage trochlear nerve schwannomas well, surgical excision should be reserved for large ones and limited to subcapsular or subtotal removal with the expectation of possible recovery of neurologic dysfunction.

Trigeminal Neuralgia due to an Isolated Cerebral Varix: Case Report

Intracranial isolated varix is a very rare entity. Although it is usually asymptomatic, there are reports on symptomatic cases with hemorrhage or mass effect that mostly relate to arteriovenous fistulas or arteriovenous malformations. We present an extremely rare case of trigeminal neuralgia caused by an isolated varix. A 55-year-old woman had been experiencing right trigeminal neuralgia for 3 years. Computed tomography and magnetic resonance imaging revealed an enhanced mass lesion on the root entry zone of the right trigeminal nerve. Angiograms confirmed the mass was a varix arising on the vein connecting the basal vein of Rosenthal and the superior petrosal vein. Preoperative three-dimensional (3D) imaging clearly depicted the anatomical relation of the varix, adjacent vessels, and trigeminal nerve, which helped plan operative procedures. The varix with its parent vein was successfully transposed from the nerve without sacrificing any veins. Her pain disappeared immediately after the surgery and did not recur during a 30-month follow-up period. The 3D image contributed to making an accurate and safer operative plan especially for this rare case.

Mouse Flamingo1/Celsr2 relates neuronal reorganization of the hypertrophic dentate granule cells after kainate injection

Single injection of kainate into the dorsal hippocampus of adult mice induced long-lasting hypertrophy and dispersion of dentate granule cells with dendritic hypertrophy and mossy fiber sprouting that resembled human hippocampal sclerosis. Our previous study indicated that brain derived neurotrophic factor was related to the initiation of these morphological changes. In this study, gene expression of the enlarged hippocampus was examined by differential display to find the gene relating to the progression of the pathological changes. Several genes were identified that were overexpressed in the enlarged dentate gyrus. One of them was highly homologous with mouse Flamingo1/Celsr2, suggesting that mouse Flamingo1/Celsr2 is related to the development of hippocampal sclerosis.

Nervus Intermedius Neuralgia Treated with Microvascular Decompression: A Case Report and Review of the Literature

Nervus intermedius neuralgia is one of the craniofacial neuralgias, which is extremely rare compared with trigeminal or glossopharyngeal neuralgia. Despite its unique symptom, the aetiology remains unclear. We present a case of a surgically treated 36-year-old woman who suffered from paroxysmal stabbing deep-ear pain for over 10 years. Preoperative magnetic resonance imaging demonstrated a vascular loop compressing the root entry zone of the vestibulocochlear nerve between the seventh and eighth cranial nerves, suggesting nervus intermedius neuralgia as a cause of her pain. Surgical exploration revealed that the nervus intermedius was displaced upward by the anterior inferior cerebellar artery. Transposition of the artery from the brainstem relieved the patient’s neurological symptom immediately after the surgery, supporting the hypothesis that nervus intermedius neuralgia could be caused by neurovascular compression.

Trigeminal Neuralgia Due to Red Vein Draining a Supratentorial Arteriovenous Malformation: Case Report

Trigeminal neuralgia (TGN) is rarely caused by arteriovenous malformation (AVM). The AVMs causing TGN are reported mostly in the ipsilateral posterior fossa. The culprit vessels are dilated feeding artery or nidus itself. We present a rare case of TGN caused by dilated draining veins from a supratentorial AVM. The patient suffered from TGN with an incidentally found large AVM, which had been left untreated. The neuralgia was successfully relieved by microvascular decompression. Dilated red veins compressed the nerve at the root entry zone and distant cisternal portion of the nerve. Technically, transposition is not practical for fragile, dilated red veins with high pressure. Interposition is safer method in this case.

Single-stage total resection of giant dumbbell-shaped hypoglossal schwannoma: a case report

Extensive large dumbbell-shaped hypoglossal schwannoma is extremely rare, and total resection is nearly impossible. We present a case of a 61-year-old male with a giant-size hypoglossal schwannoma with moderate tongue atrophy. The tumor extended from the enlarged hypoglossal canal to the brainstem intradurally and the high cervical region extradurally. Through the extreme lateral infrajugular transcondylar (ELITE) skull base approach, the tumor was totally removed in a single-stage operation. Single-stage total resection is feasible by an experienced skull base team utilizing transcondylar skull base techniques and high cervical dissection.

Trigeminal neurofibroma in the infratemporal fossa arising from the inferior alveolar nerve: A case report

Solitary neurofibromas arising from cranial nerves are rare, and those arising from the peripheral divisions of the trigeminal nerve are even rarer. Although infratemporal fossa (ITF) masses are challenging to remove, certain approaches are considered feasible for this region. The present study reports a rare case of an ITF neurofibroma arising from the inferior alveolar nerve. The 27-year-old male patient presented with numbness of the right jaw. A radiological examination revealed a large mass occupying the ITF, from the mandible to the foramen ovale, originating from the inferior alveolar nerve in the mandible. The tumor was successfully excised via a transtemporal approach followed by a transoral-retromolar approach. A histological examination confirmed the diagnosis of neurofibroma. The present case demonstrates that a combination of the transtemporal and transoral-retromolar approaches may provide wide access to the ITF region.