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Takakazu Kawamata

Publications and source records attributed to Takakazu Kawamata.

18 recordsLinked to original sources
PubMed2006

Expression of type 5 somatostatin receptor in TSH-secreting pituitary adenomas: a possible marker for predicting long-term response to octreotide therapy.

In TSH-secreting pituitary adenomas (TSHoma), octreotide (OCT) therapy reduces tumor size and TSH secretion in some cases but not in others. As OCT acts through various types of somatostatin receptors (SSTRs), the different responses of TSHoma to OCT might be explained by the differences of SSTR expression. We therefore studied the expression of subtype-specific SSTR mRNA transcripts in tumor tissues by RT-PCR. Type 2 (SSTR2) mRNA transcripts were detected in all 8 tumors but those of SSTR3 and SSTR5 were demonstrated only in 5 of them. Serum TSH levels were decreased by OCT administration test in all patients but OCT therapy was effective in two patients out of three. SSTR5 mRNA was detected in two tumors from the responder, but not in one tumor that was resistant to OCT. These observations suggest that the temporal decrease of TSH by OCT may be mediated by SSTR2, and that the long term response to OCT therapy may be related with the expression of SSTR5. Therefore, the expression of SSTR5 in TSHoma may be a useful marker for predicting the outcome of the therapy, but further studies with larger numbers of patients are necessary.

Adenoma↗
PubMed2006

Intrasellar remote metastasis from adenoid cystic carcinoma of parotid gland: case report.

Adenoid cystic carcinoma is a tumor of exocrine glands originating primarily from the minor and major salivary glands, lacrimal gland, bronchus, breast, and intestinal and genital tracts. Intracranial remote metastasis from adenoid cystic carcinoma in salivary gland is quite rare. The authors encountered a case of intrasellar remote metastasis from an adenoid cystic carcinoma of parotid gland origin, presenting with hyponatremia secondary to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). To our knowledge, this is the first reported case of metastasis from an adenoid cystic carcinoma to intrasellar area. A 78-year-old woman had an adenoid cystic carcinoma in the left parotid gland, which was resected surgically followed by local radiation therapy of 60 Gy. After 4 years, the patient presented with general malaise, followed by disturbed consciousness caused by hyponatremia. The clinical data showed severe hyponatremia induced by SIADH. An intrasellar heterogenous mass lesion compressing the optic chiasm was resected subtotally via an endonasal transsphenoidal approach. Histopathological examination of the tumor specimens revealed adenoid cystic carcinoma, which had identical histological findings as those of the painful superficial cervical lymph nodes resected in the same operation. Tumors such as the present case are easily confused with pituitary adenoma or craniopharyngioma. Although rare, metastasis from tumors including those of salivary gland origin should be considered in the differential diagnosis of unusual pituitary tumors.

Aged↗
PubMed2006

Hyponatremia after transsphenoidal surgery for hypothalamo-pituitary tumors.

Transient diabetes insipidus is a well-known complication after transsphenoidal surgery (TSS). On the other hand, transient hyponatremia has been reported as being a delayed complication of TSS. Transient hyponatremia has been attributed to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), but the details of hyponatremia have not been clarified. In the present study, we retrospectively reviewed 110 consecutive patients (39 males and 71 females, age 9-80 years) operated on transsphenoidally for pituitary and hypothalamic tumors. We investigated the frequency, time of onset, duration of hyponatremia after TSS, and analyzed possible factors associated with it. A postoperative sodium concentration <135 mEq/l was observed in 29 (26%) patients. Five patients were excluded from this study because their hyponatremia could be due to either overdose of desmopressin or SIADH for meningitis. Therefore, we investigated 24 (22%) patients with hyponatremia in this study. The sodium levels in the patients with hyponatremia ranged from 110 to 134, with a mean of 126.2 +/- 5.3 mEq/l. Hyponatremia was observed on average on postoperative day 9.5 +/- 2.4, the serum sodium levels normalized within 3.8 +/- 1.7 days. Hyponatremia occurred in patients with non-functioning pituitary adenoma (26%, 11/42), Rathke's cleft cyst (29%, 5/17), prolactinoma (31%, 4/13) and acromegaly (15%, 4/27). 18 patients (75%, 6/24) who developed hyponatremia had macrotumor (>10 mm), and 6 patients (25%, 6/24) had microtumor. The plasma arginine vasopressin (AVP) levels in the patients with hyponatremia ranged from 0.21 to 2.1, with a mean of 0.79 +/- 0.46 pg/ml, and the levels were inversely correlated with plasma osmolality (r = -0.80, p = 0.002). The urine to plasma osmolality ratios were >1. All the patients received appropriate hormonal replacement, including hydrocortisone. These data showed that postoperative hyponatremia after TSS was not rare, and the hyponatremia was mainly associated with SIADH. As the hyponatremia could be a life-threatening complication, all patients should be screened for serum electrolytes after TSS.

Adolescent↗
PubMed2006

[Rathke's cleft cyst].

Explore the source record for details and available documents.

Central Nervous System Cysts↗
PubMed2005

Surgical removal of growth hormone-secreting pituitary adenomas with intensive microsurgical pseudocapsule resection results in complete remission of acromegaly.

Although some investigators recommended surgical removal of the borders between pituitary adenoma and the surrounding normal pituitary gland, there is so far little documentation of how intensive dissection of the border zone affects the actual clinical remission rate of pituitary adenomas. We investigated the precise histological characteristics of the boundary, using surgical specimens from patients who underwent intensive resection of "microsurgical pseudocapsule" of growth hormone (GH)-secreting pituitary adenomas. Furthermore, we compared the remission rate of acromegaly between subjects with (Group 1) and without (Group 2) intensive resection of microsurgical pseudocapsule in order to correlate the histological complete resection and endocrinological remission. Histologically, most adenomas were in direct contact with normal pituitary gland that formed an increased fibrous component facing the adenoma, without a true histological pseudocapsule. It was impossible to dissect the tumor at exactly the tumor--normal pituitary interface for the whole extent of the pituitary adenoma during surgery, and complete removal of the tumor inevitably included a portion of normal tissue (microsurgical pseudocapsule). The biochemical remission rate was significantly higher in Group 1 than in Group 2 (90.0 vs 61.1%), and Group 1 showed no additional postoperative pituitary hypofunction. The present results suggested that intensive resection of the microsurgical pseudocapsule is essential to accomplish histological and endocrinological total resection of the GH-secreting pituitary adenomas for remission of acromegaly.

Adult↗
PubMed2005

Large facial nerve schwannomas without facial palsy: case reports and review of the literature.

Although approximately 30% of facial nerve schwannoma cases present with no facial palsy, a large facial nerve schwannoma extending to the middle and posterior cranial fossa quite rarely presents without facial palsy. The authors encountered two patients with large facial nerve schwannoma who presented with only hearing impairment and no facial palsy. The first patient was a 64-year-old woman who presented with right auditory impairment without facial palsy. MR images demonstrated a dumbbell-shaped tumor in the cerebellopontine angle. Another patient, a 40-year-old woman, also presented with vertigo and right tinnitus without facial palsy. MR images demonstrated a huge tumor expanding into both the posterior cranial fossa and middle cranial fossa. In both cases, intraoperative findings confirmed that the tumors had grown from the facial nerve. Facial nerve schwannoma can be easily diagnosed if detailed neurological evaluations and appropriate neuroimagings are conducted. However, in spite of such huge tumoral size and expanding pattern, the facial nerve function was relatively preserved. Anatomical features of the facial schwannoma are discussed. A tumor extending to the middle and posterior cranial fossa should remind neurosurgeons to consider facial nerve schwannomas even in the absence of facial palsy.

Aged↗
PubMed2005

Scaled suction for microneurosurgery: technical note.

OBJECTIVE: We have developed scaled suction to facilitate the measurement of aneurysm neck width and tumor size during operations. METHODS: We constructed a new suction device scaled every 1 mm from the tip to 3 cm and every 5 mm from 3 to 5 cm. The scaled suction devices have been used in 50 aneurysm and brain tumor operations. RESULTS: The new suction device permits easy measurement of aneurysm neck width, tumor size, the extent of internal decompression of tumor, and depth from the surface of the brain to the lesion. CONCLUSION: Our scaled suction device is a simple and useful navigator for continuously measuring intraoperative variables such as lesion size and distance between the lesion and the surrounding vital structures.

Aneurysm↗
PubMed2005

Image-guided neurosurgery system integrating AR-based navigation and open-MRI monitoring.

As endoscopic surgery has become a popular form of minimally invasive surgery, it increasingly requires useful imaging tools to help the surgeons perform safe and secure operations. Our navigation system provides surgeons with visual information by overlaying 3D wire frame models of tumor onto live images, as well as by displaying relative the positions of surgical tools and the target tumor. Such 3D wire frame models are generated from pre-operative CT/MR images with the help of a 3D surgical simulation software. Another important function of our system is real-time volume rendering of intra-operative MR images for the target tumor. This function allows surgeons to carefully observe the vicinity of the tumor regions to be removed, by rendering the sectional views with respect to the surgical tool position, so that surgical performance can be easily monitored during the operation. We tested this navigation system in more than 10 clinical operations and verified the effectiveness of the navigation and surgical performance.

Brain Diseases↗
PubMed2005

Carotid tissue levels of argatroban after direct local delivery during carotid endarterectomy to prevent perioperative cerebral embolism.

OBJECTIVE: Argatroban is a synthetic direct thrombin inhibitor. We applied argatroban locally during carotid endarterectomy to prevent local mural thrombus formation. Although local delivery of argatroban is expected to be effective for inhibition of mural clot formation, there is no report of the evaluation of its clinical effectiveness or local drug concentration in humans. METHODS: Five mg of argatroban (0.5 mg/ml) was applied twice intraoperatively just after arteriotomy for measurement of intraplaque level of argatroban and during closure of the arteriotomy for preventing thrombus formation. After exposure of the carotid plaque to argatroban for a specified duration (0, 3, 5, or 10 min), argatroban was sufficiently washed with saline and the carotid plaque was removed for measurement of tissue concentration of argatroban. Intraplaque level of argatroban was determined by high-performance liquid chromatography. A second application was performed during closure of the arteriotomy. Argatroban was applied for 10 minutes, followed by washing with saline. Postoperative embolic cerebrovascular complications and carotid restenosis also were investigated to verify the efficacy of direct local application of argatroban. RESULTS: Tissue levels of argatroban in the carotid plaque after 3, 5, and 10 minutes of direct application were 24.0 +/- 13.7, 31.6 +/- 20.0, and 44.0 +/- 15.1 mug/g, respectively. The concentrations at all time points were significantly elevated compared with the control, and a significant difference in concentration was observed between 3 minutes and 10 minutes. In the present study, concentration at 3 minutes was much higher than the effective tissue levels of argatroban reported in experimental studies. No patient developed postoperative cerebrovascular complications. CONCLUSION: The results suggest that direct local application of argatroban during carotid endarterectomy for at least 3 minutes may deliver high local tissue levels. Argatroban may be effective for prevention of perioperative embolic cerebral complications during carotid endarterectomy.

Adult↗
PubMed2004

Pravastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, reduces delayed neuronal death following transient forebrain ischemia in the adult rat hippocampus.

Recent evidence indicates that statins have beneficial effects on the brain in the ischemic condition. However, there is a lack of studies related to the effect of statins on delayed neuronal death. We investigated the effect of prophylactic therapy with pravastatin on delayed neuronal death in the rat hippocampus. The rats were given a daily dose of 20 mg/kg of pravastatin orally for 14 days. Transient forebrain ischemia was induced by the four-vessel occlusion method. Three days after ischemia, surviving neurons of the hippocampal CA1 subfield were counted. Our results demonstrated that prophylactic statin treatment significantly reduced delayed neuronal death after transient forebrain ischemia. Our findings suggest that prophylactic statin treatment may be useful in preventing functional neurological disorders after transient cerebral ischemic insult.

Animals↗
PubMed2004

Continuous laryngoscopic vocal cord monitoring for vascular malformation surgery in the medulla oblongata: technical note.

OBJECTIVE: Resection of lesions located in the medulla oblongata may result in significant morbidity. The most lethal complications are swallowing disturbances, which can lead to aspiration pneumonia. To prevent this problem, the lower cranial nerves can be mapped with recording needles placed in the posterior pharyngeal wall and the tongue. However, mapping alone is not sufficient to preserve the lower cranial nerves and swallowing functions. To overcome this problem, we attempted to devise a method to intraoperatively monitor vocal cord movements with a laryngoscope. We used this method, in addition to other types of brainstem mapping, in three cases. METHODS: Recording needles were inserted into the posterior pharyngeal wall and the tongue, to record the responses of Cranial Nerves IX and XII. A laryngoscope was inserted orally, for direct observation of vocal cord movements, and was maintained until the end of the operation. The floor of the fourth ventricle was stimulated with a monopolar stimulator. Somatosensory evoked potentials, auditory evoked potentials, and motor evoked potentials were simultaneously monitored. RESULTS: We were able to confirm synchronized vocal cord adduction with stimulation of the expected vagal trigonum location and to monitor rhythmic vocal cord movements during spontaneous respiration. In all three cases, we removed the lesions without postoperative complications. CONCLUSION: In addition to intraoperative vocal cord monitoring with a laryngoscope, we could safely determine the optimal location for the first incision in the floor of the fourth ventricle. Potentially lethal postoperative complications can be avoided with brainstem mapping and vocal cord monitoring.

Brain Mapping↗
PubMed2004

[Pituitary tumors].

Pituitary adenomas have been reported to be the most common benign intracranial neoplasms. Recent radiological advancement has resulted in incidental diagnosis of pituitary tumors such as pituitary adenomas and Rathke's cleft cysts. The most common location of pituitary adenomas is intrasellar region with or without suprasellar extension. Pituitary tumors in unusual site, however, have been reported previously, including the sphenoid sinus, suprasellar region, clivus, nasal cavity, or something like that. The sources of ectopic pituitary tumors have been thought to be migration of pituitary cells in pituitary adenomas and of squamous epithelial cell remnants of the obliterated craniopharyngeal canal in craniopharyngiomas. We describe ectopic pituitary tumors and recent knowledge of etiology and pathology of pituitary tumors. Furthermore, we mention recent advancement of endonasal transsphenoidal surgery to treat pituitary tumors.

Adenoma↗
PubMed2003

Divergence in signaling pathways involved in promotion of cell viability mediated by bFGF, NGF, and EGF in PC12 cells.

We employed a series of inhibitors of intracellular cascade to disclose the precise molecular mechanisms by which basic fibroblast growth factor (bFGF) promotes viability of PC12 cells and compared with nerve growth factor (NGF) and epidermal growth factor (EGF). The MEK 1 and 2 inhibitors, U0126 and PD98059, significantly suppressed cell viability mediated by bFGF in a dose-dependent manner, and to a greater extent compared with EGF and NGF. The degree of MEK dependency for growth factor-mediated cell viability was estimated to be in the order of bFGF, EGF, and NGF. Rapamycin strongly inhibited the effect of NGF on cell viability, compared with bFGF and EGF. The mechanisms of action of NGF-mediated cell viability may depend largely on p70 S6 kinase-related signal transduction pathways comparing to bFGF and EGF. The present findings suggest that different signal transduction systems may be involved in the molecular mechanisms by which bFGF, NGF, and EGF mediate cell viability.

Animals↗
PubMed2002

Endoscopic augmented reality navigation system for endonasal transsphenoidal surgery to treat pituitary tumors: technical note.

OBJECTIVE: Endoscopes have been commonly used in transsphenoidal surgery to treat pituitary tumors, to compensate for the narrow surgical field. Although many navigation systems have been introduced for neurosurgical procedures, there have been few reports of navigation systems for endoscopic operations. This report presents our recently developed, endoscopic, augmented reality (AR) navigation system. METHODS: The technology is based on the principles of AR environment technology. The system consisted of a rigid endoscope with light-emitting diodes, an optical tracking system, and a controller. The operation of the optical tracking system was based on two sets of infrared light-emitting diodes, which measured the position and orientation of the endoscope relative to the patient's head. We used the system during endonasal transsphenoidal operations to treat pituitary tumors in 12 recent cases. RESULTS: Anatomic, "real," three-dimensional, virtual images of the tumor and nearby anatomic structures (including the internal carotid arteries, sphenoid sinuses, and optic nerves) were superimposed on real- time endoscopic live images. The system also indicated the positions and directions of the endoscope and the endoscopic beam in three-dimensional magnetic resonance imaging or computed tomographic planes. Furthermore, the colors of the wire-frame images of the tumor changed according to the distance between the tip of the endoscope and the tumor. These features were superior to those of conventional navigation systems, which are available only for operating microscopes. CONCLUSION: The endoscopic AR navigation system allows surgeons to perform accurate, safe, endoscope-assisted operations to treat pituitary tumors; it is particularly useful for reoperations, in which midline landmarks may be absent. We consider the AR navigation system to be a promising tool for safe, minimally invasive, endonasal, transsphenoidal surgery to treat pituitary tumors.

Endoscopy↗
PubMed2002

Minimally invasive endoscope-assisted endonasal trans-sphenoidal microsurgery for pituitary tumors: experience with 215 cases comparing with sublabial trans-sphenoidal approach.

Recent advances in endoscopic surgery have developed an endonasal route suitable for pituitary surgery. The main goal of this article is to evaluate benefits of our endoscope-assisted endonasal trans-sphenoidal microsurgery for pituitary tumors in 215 consecutive cases. The pathological classifications of the 215 cases are as follows: 163 pituitary adenomas, 23 Rathke's cleft cysts, 17 craniopharyngiomas, and 12 others. The patients were surgically treated via the endonasal trans-sphenoidal approach using an operating microscope as the primary instrument for tumor resection. Endoscopes were used to complement the operating microscope in visualization. We compared the new approach to the sublabial trans-sphenoidal approach (197 cases) with respect to endocrinological outcomes and surgical complications. Our endonasal trans-sphenoidal approach was beneficial in eliminating the complications of lip numbness, which was often observed in patients undergoing sublabial surgery, and nasal septal perforation. In addition, endocrinological outcome comparable to those in the sublabial group was achieved in the endonasal group. We consider that the endoscope, which allows visualization of areas not seen with the operating microscope, should be used actively in conjunction with the operating microscope that provides three-dimensional visualization and is timesaving. Our surgical method for pituitary tumors provides good results with minimal invasion, by exploiting the advantages of a microscope and an endoscope.

Adolescent↗
PubMed2002

Role of a synthetic pyrimidine compound, MS-818, in reduction of infarct size and amelioration of sensorimotor dysfunction following permanent focal cerebral ischemia in rats.

OBJECT: A synthetic heterocyclic pyrimidine compound, MS-818 (2-piperadino-6-methyl-5-oxo-5,6-dihydro-(7H) pyrrolo-[3,4-d] pyrimidine maleate) is reported to have a variety of biological activities including neurite outgrowth, astrocyte differentiation, suppression of neuronal apoptosis, regeneration of injured peripheral nerves, fracture repairs, angiogenesis, and superovulation. To be able to explicate the neurotrophic effects of MS-818, the authors evaluated its effect on the reduction of infarct volume and amelioration of sensorimotor dysfunction in a rat model of focal ischemia. METHODS: Forty male Sprague-Dawley rats were subjected to right middle cerebral artery occlusion and assigned to one of four treatment groups (10 animals in each group). The MS-818 (1, 5, or 10 mg/kg) or phosphate-buffered saline (control group) was administered intraperitoneally at onset of ischemia and again 24 hours later. The rats were killed 48 hours after they underwent surgery to induce stroke, and infarct volume was determined using an image-analysis computer software program following staining with 2,3,5-triphenyltetrazolium chloride. Postischemic neurological deficit and body weight were also assessed. CONCLUSIONS: Significant reductions in infarct volume (total and cortical infarction) were found in all the MS-818-treated groups compared with the control group. Furthermore, MS-818 induced significant amelioration of sensorimotor dysfunction, as indicated by the results of forelimb and hindlimb placing tests. The present findings suggest that MS-818, which has a much smaller molecular weight than neurotrophic peptides. represents a new approach to the treatment of focal cerebral ischemia.

Animals↗