✓ A new 1.45-mm endoscope is described that can be inserted through a thin-walled No. 16 needle. The instrument was used in 10 cadavers for endoscopic exploration of the cisterna magna, the C1–2 space, Meckel's cave, and the cerebellopontine angle. Its potential clinical application is discussed.
Effect of microvascular decompression and etiological considerations
Phyo Kim and Takanori Fukushima
✓ In 95 patients with hemifacial spasm, synkinetic actions were measured objectively using electromyographic examination of the blink reflex and impedance audiometry. Abnormal synkinesis between the orbicularis oculi and the orbicularis oris muscles was recorded in 93% of cases, while synkinesis between the stapedius muscle and the facial muscles was recorded in 87%. Neither of these effects could be demonstrated on the unaffected side. The examinations were performed before and after microvascular decompression in 66 cases. Rapid disappearance of synkinesis, often within 10 days, was observed after the relief of vascular compression in 81% of patients who had not undergone previous peripheral facial nerve block procedures. These findings indicate that the synkinesis seen in hemifacial spasm is essentially a reversible condition, and suggest that axonal ephaptic conduction at the vascular compression site plays an important role in the pathophysiological mechanism of hemifacial spasm.
William T. Couldwell and Takanori Fukushima
✓ The authors describe a cosmetic mastoidectomy technique for use when performing a combined supra/infratentorial craniotomy and transtemporal exposure. The technique involves a single temporal suboccipital bone flap and cosmetic mastoidectomy, removing the outer table of bone for later replacement. Replacement of the outer table of mastoid bone enables tamponade of a fat graft against the dura to reduce the risk of postoperative cerebrospinal fluid leaks. The technique has been performed in eight patients treated for petroclival meningiomas with excellent cosmetic results.
Shinichiro Miyazaki, Takanori Fukushima and Takamitsu Fujimaki
✓ Two patients with large high-cervical paragangliomas were treated with radical resection and placement of a cervical-to-petrous internal carotid artery saphenous vein bypass. The high-cervical and infratemporal segments of the internal carotid artery engulfed within the tumor were resected and successfully replaced with a saphenous vein interposition graft. The postoperative course was uneventful in both cases and follow-up angiography revealed satisfactory reconstruction of the high-cervical and infratemporal skull base carotid artery. The operative technique, indications, and potential future applications of this newly developed skull base bypass procedure are discussed.
Alterations of cortical and spinal evoked potentials
Johannes Schramm, Keizo Hashizume, Takanori Fukushima and Hiroshi Takahashi
✓ A new model of experimental spinal cord injury produced by slow, graded compression in cats is described. The extent of cord compression was evaluated by monitoring somatosensory evoked potentials (SEP's). The compression was exerted by means of a special screw-plate assembly with stepwise advancement of the compression plate at different time intervals and was completed when cortical SEP had disappeared. Every stage in the total course of gradual compression was expressed as a percentage of the total. Cortical and spinal SEP's were recorded at each increment. The SEP pattern was analyzed in terms of latency, amplitude, and wave form. It was noteworthy that SEP's were remarkably resistant to gradual compression. The amplitude of cortical SEP's began decreasing at a late stage of compression, usually at about 80% of total compression, and that of spinal SEP's some time earlier, at about 60% of total compression. They both then rapidly fell to zero. Cortical SEP's showed a slight increase in latency concurrent with the reduction of amplitude, while the latency of spinal SEP's was constant. Mid-thoracic SEP's showed considerable individual variation in wave form. Their changes were similar to those of cortical SEP. Thoracolumbar SEP's, recorded immediately rostral to the compression, showed little individual variation, and did not show flat recordings even with maximum compression. A small monophasic positive wave was present in all animals even after the cortical SEP's became flat. This “final potential” was assumed to be caused by electrotonic volume conduction from the activities of the dorsal white matter caudal to the compression site. The reversibility of SEP's after the release of compression was remarkable. Both cortical and spinal SEP's could show complete recovery even when histological examination demonstrated hemorrhagic necrosis. The present data show no linear correlation between SEP changes and degree of compression. There are no changes with slight or moderate degree of compression. Alterations of SEP's in slow compression models should suggest the presence of a severe degree of compression.
Takanori Fukushima and Keiji Sano
✓ A new modification of the transseptal, transsphenoidal approach to the sella turcica is described. The procedure consists of unilateral dissection of the septal mucosa through a sublabial route, and retraction of the entire nasal septum with its upper attachment as a hinge. For mobilization of the septum, an L-shaped osteotomy is made along the base of the septum and along the anterior wall of the sphenoid sinus. It provides adequate exposure of the sphenoid sinus while preserving the septal structures. The anterior nasal spine and the edges of the nares are also left intact. The anterior wall of the sphenoid sinus is resected en bloc and is used as a bone splint for the reconstruction of the sellar floor. This approach has been performed in 45 cases of pituitary adenoma, one of craniopharyngioma, and one with sphenoid mucocele. There was no instance of complications such as mucosal perforation, septal deformity, or infection. Modifications of the surgical instruments used are described.
Takamitsu Fujimaki, Takanori Fukushima and Shinichiro Miyazaki
✓ The results in 122 patients with trigeminal neuralgia who underwent percutaneous retrogasserian glycerol injection are presented. Eighty patients were followed from 38 to 54 months. The recurrence rate at 54 months was 72% (Kaplan-Meier analysis), and the median pain-free interval was 32 months. Complications associated with the procedure were significantly high: 63% of the patients had definite hypesthesia of the face and 29% had unpleasant dysesthesias, including two cases of anesthesia dolorosa. Sensory disturbances were most frequent in patients who had received a previous alcohol block procedure. Among the patients without previous peripheral procedures, 50% developed sensory disturbances. Because of the high rates of recurrence and sensory disturbances, the authors prefer microvascular decompression for the management of trigeminal neuralgia.
Ketan R. Bulsara, Toral Patel and Takanori Fukushima
Despite advancements in endovascular neurosurgery, there remains an important role for cerebral bypass surgery in the treatment of skull base lesions. The authors describe their replacement cerebral bypass surgery techniques incorporating lessons learned over 2 decades.
The authors performed a retrospective review of cerebral bypass surgery performed by the senior author for skull base lesions between 1986 and 2006. One hundred patients had adjunct bypass surgery for skull base lesions.
The bypass surgeries performed are conceptually divided into Skull Base Bypass I, II, and III. The majority of lesions requiring bypass surgery were giant cavernous carotid artery aneurysms or skull base meningiomas. There were no deaths in this case series. There was a 7% morbidity rate.
The ability to perform this surgery is an important adjunct in the armamentarium of skull base/cerebrovascular neurosurgeons.
Han Soo Chang, Takanori Fukushima, Shinichiro Miyazaki and Teruaki Tamagawa
✓ A case of a ruptured fusiform aneurysm of the posterior cerebral artery is reported. The aneurysm was excised and end-to-end anastomosis was carried out between the two ends of the posterior cerebral artery. There is no previous report of a posterior cerebral artery aneurysm treated with this technique. The pertinent literature is reviewed and the significance of this technique in the treatment of unclippable cerebral aneurysms is discussed.