Usefulness of intraoperative magnetic resonance imaging for glioma surgery

BACKGROUND

Radical resection of gliomas can increase patient's survival. There is known concern, however, that aggressive tumour removal can result in neurological morbidity. The objective of the present study was to evaluate the usefulness of low magnetic field strength (0.3 Tesla) open intraoperative magnetic resonance imaging (iMRI) for complete resection of glioma with emphasis on functional outcome.

METHODS

From 2000 to 2004, 96 patients with intracranial gliomas underwent tumour resection with the use of iMRI in Tokyo Women's Medical University. There were 50 men and 46 women; mean age was 39 years. Tumour volume varied from 1.2 ml to 198 ml (median: 36.5 mL). Resection rate and postoperative neurological status were compared between control group (46 cases, operated on during the initial period after installation of iMRI), and study group (50 most recent cases, in whom surgery was done using established treatment algorithm and improved image quality).

FINDINGS

Overall, mean resection rate was 93%, and medial residual tumour volume was 0.17 ml. Total tumour removal was achieved in 44 cases (46%). Compared to control group, resection rate in the study group was significantly higher (91%, vs. 95%; P < 0.05), whereas residual tumour volume was significantly smaller (1.7 mL vs. 0.025 mL; P < 0.001). Nine patients in the control group (20%) and 24 in the study group (48%) experienced temporary postoperative neurological deterioration (P < 0.01), however, the rate of permanent morbidity evaluated 3 months after surgery did not differ significantly between the groups investigated (13% vs. 14%).

CONCLUSIONS

Use of iMRI during surgery for intracranial gliomas permits to attain aggressive tumour resection with good functional outcome. Nevertheless, surgical experience with the iMRI system, establishment of treatment algorithm, and improvement of image quality are of paramount importance for optimal results.

Novel flexible forceps for endoscopic transsphenoidal resection of pituitary tumors: technical report

The endoscope has become an essential tool for transsphenoidal pituitary surgeries because of the panoramic view and the ability to visualize structures beyond the direct line of vision. However, the regular dedicated instruments for these surgeries sometimes do not reach the areas visualized by an angled endoscope, and instrument maneuverability is limited. To overcome or minimize these problems, we constructed a new flexible tumor forceps that can be manipulated to change shape after placing into the surgical fields via the endonasal or sublabial route, to reach any desirable location for tumor dissection and excision. We applied this newly developed instrument in endonasal endoscopic resection complementing microsurgical procedure in 20 cases of pituitary tumors. The flexible forceps was able to access sites where regular dedicated instruments for transsphenoidal pituitary surgeries could not readily reach despite endoscopic visualization. No complication was observed in the present series, confirming the safety of the newly designed flexible forceps. Our newly developed flexible forceps improves the instrument maneuverability of endoscopic transsphenoidal resection of pituitary tumors, especially those located laterally at the cavernous sinuses or with frontal extension. The use of this instrument makes the best use of endoscopic panoramic visualization for tumor removal.

Management and prognosis of cysts developed on long-term follow-up after Gamma Knife radiosurgery for intracranial arteriovenous malformations

BACKGROUND

Delayed cyst formation is a well-recognized complication after radiosurgery for intracranial AVM. The objective of the present study was the evaluation of the different management options for these lesions and the corresponding prognosis of patients.

METHODS

Between 2000 and 2005, 12 patients with intracranial AVM initially treated by GKR were reevaluated at Tokyo Women's Medical University because of delayed cyst formation in the vicinity of the target area. There were 7 men and 5 women. The mean age of the patients was 31.8 years at the time of GKR and 41.1 years at the time of complication. The average period between treatment and diagnosis of the complication constituted 6.7 years. All AVMs had lobar location and showed complete angiographic obliteration after GKR.

RESULTS

The most common neurological signs and symptoms at the time of cyst presentation were headache (10 cases) and seizures (4 cases). Two patients were asymptomatic. Three patients underwent surgery soon after the diagnosis of the cyst, whereas initial observation was done in another 9. Among the latter, 5 patients had to be treated surgically thereafter because of persistent or aggravated neurological symptoms associated with radiological cyst expansion. Four other patients, including both asymptomatic ones, are in stable condition without surgery. Follow-up after treatment of the cyst varied from 7 to 60 months (average, 34.3 months). All patients are in good condition.

CONCLUSIONS

Although delayed formation of cysts after GKR for intracranial AVM should be considered as a complication of the radiosurgical treatment, it has a relatively good prognosis. Observation can be recommended as initial option for compensated and asymptomatic patients.

Bone cancer increases transient receptor potential vanilloid subfamily 1 expression within distinct subpopulations of dorsal root ganglion neurons

Bone cancer pain has a strong impact on the quality of life of patients but is difficult to treat. Therefore, the mechanisms of bone cancer pain require elucidation for the purpose of development of new therapeutics. A recent study showed that activation of transient receptor potential vanilloid subfamily 1 (TRPV1) was involved in bone cancer pain. In this study, we re-evaluated the analgesic effects of pharmacological blockade of TRPV1 using the potent TRPV1 antagonist 5-iodoresiniferatoxin (I-RTX) and examined whether bone cancer can change TRPV1 expression and distribution in the primary sensory neurons in a mouse model of bone cancer pain. Implantation of osteosarcoma into the femur induced ongoing and movement-evoked bone cancer-related pain behaviors. These behaviors were significantly reduced by i.p. administration of I-RTX, compared with vehicle. Western blot and reverse transcription-polymerase chain reaction (RT-PCR) analyses revealed that TRPV1 level was significantly increased in dorsal root ganglions (DRGs) ipsilateral to sarcoma implantation. Immunohistochemical analysis showed that implantation of osteosarcoma induced not only an increase in the percentage of TRPV1-positive neurons among DRG neurons (24.3+/-1.3% in sham mice and 31.2+/-1.3% in mice with osteosarcoma implantation, P<0.05) but also an overall shift in the distribution of area of profiles to the right. Colocalization study showed that the percentages of colocalization of TRPV1 with neurofilament 200 kD (NF200) and calcitonin gene-related peptide (CGRP) but not isolectin B4 (IB4) among DRG neurons in mice with osteosarcoma implantation were increased compared with those in sham mice (from 0.8+/-0.1% to 2.1+/-0.3% for TRPV1 and NF200 and from 21.1+/-1.3% to 26.5+/-0.2% for TRPV1 and CGRP). In conclusion, TRPV1 activation plays a critical role in the generation of bone cancer pain, and bone cancer increases TRPV1 expression within distinct subpopulation of DRG neurons. These findings may lead to novel strategies for the treatment of bone cancer pain.

Perioperative plasma active and total ghrelin levels are reduced in acromegaly when compared with in nonfunctioning pituitary tumours even after normalization of serum GH

OBJECTIVE

Ghrelin is a novel gastric peptide known to stimulate GH secretion, but the relationship between ghrelin and the GH-insulin-like growth factor (IGF)-1 axis in GH excess or deficiency is poorly understood. This study investigated dysregulation of ghrelin secretion in acromegaly and its short-term postoperative recovery.

METHODS

A prospective study was conducted on eight patients who underwent complete transsphenoidal resection of GH-producing pituitary adenomas (acromegaly group) and 22 for endocrinologically nonfunctioning pituitary tumours (control group). Active and total plasma ghrelin levels were measured serially before and after surgery.

RESULTS

Preoperative active and total plasma ghrelin concentrations (mean +/- SD; fmol/ml) were significantly reduced in acromegalic patients when compared with those in the controls (9.6 +/- 4.3 and 157.4 +/- 65.6 vs. 21.8 +/- 13.0 and 267.1 +/- 111.4; P = 0.023 and P = 0.021, respectively). Both levels were still significantly suppressed on postoperative Day 7 in the acromegaly group when compared with those in the control group (11.7 +/- 4.3 and 197.8 +/- 68.9 vs. 22.5 +/- 12.6 and 302.7 +/- 100.0; P = 0.038 and P = 0.018, respectively). The ratios of active to total ghrelin were not significantly different between the two groups before and after operation. In acromegalic patients, active and total ghrelin levels remained significantly suppressed even after normalization of serum GH levels.

CONCLUSIONS

The putative negative feedback mechanism of GH on ghrelin secretion may in part account for the low ghrelin levels observed in acromegalic patients, and the mechanism may persist even after normalization of serum GH.

INTRAOPERATIVE APPLICATION OF THERMOGRAPHY IN EXTRACRANIAL-INTRACRANIAL BYPASS SURGERY

OBJECTIVE

The extracranial-intracranial bypass may have the potential to improve hemodynamic cerebral ischemia caused by occlusive diseases of the main cerebral arteries. Intraoperative confirmation of effective distribution of blood flow via the donor arteries to the involved region will assure a successful bypass surgery.

METHODS

Infrared thermography was used to measure the temperature of the cortical surface at the operative field. Regional cerebral blood flow (rCBF) was measured with a laser Doppler flow meter. Changes in the cortical surface temperature before and after temporary occlusion of the bypass were compared with changes in rCBF values in the corresponding sites.

RESULTS

Thermographic examination demonstrated a heterogeneous increase of cortical surface temperature caused by the blood flow via the extracranial-intracranial bypass and was closely related to rCBF changes.

CONCLUSION

Thermography is useful not only to demonstrate the distribution of blood flow through the extracranial-intracranial bypass but also to quantitatively evaluate the rCBF changes in the operative field.

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.

Immunohistochemical analysis of acid-sensing ion channel 2 expression in rat dorsal root ganglion and effects of axotomy

Several studies have suggested that acid-sensing ion channel 2 (ASIC2) plays a role in mechanoperception and acid sensing in the peripheral nervous system. We examined the expression and distribution of ASIC2 in the rat dorsal root ganglion, the co-localization of ASIC2 with tropomyosin-related kinase (trk) receptors, and the effects of axotomy on ASIC2 expression. ASIC2 immunoreactivity was observed in both neurons and satellite cells. ASIC2-positive neurons accounted for 16.5 +/- 2.4% of the total neurons in normal dorsal root ganglion. Most ASIC2-positive neurons were medium-to-large neurons and were labeled with neurofilament 200 kD (NF200). Within these neurons, ASIC2 was not evenly distributed throughout the cytoplasm, but rather was accumulated prominently in the cytoplasm adjacent to the axon hillock and axonal process. We next examined the co-localization of ASIC2 with trk receptors. trkA was expressed in few ASIC2-positive neurons, and trkB and trkC were observed in 85.2% and 53.4% of ASIC2-positive neurons, respectively, while only 6.9% of ASIC2-positive neurons were co-localized with trkC alone. Peripheral axotomy markedly reduced ASIC2 expression in the axotomized dorsal root ganglion neurons. On the other hand, intense ASIC2 staining was observed in satellite cells. These results show that ASIC2 is expressed in the distinct neurochemical population of sensory neurons as well as satellite cells, and that peripheral axotomy induced marked reductions in ASIC2 in neurons.

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.

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.

Acute hemispheric swelling associated with thin subdural hematomas: pathophysiology of repetitive head injury in sports

INTRODUCTION

The most common head injury in sports is concussion, and repeated concussions occurring within a short period occasionally can be fatal. Acute subdural hematoma is the most common severe head injury and can be associated with severe neurologic disability and death in sports. We investigated severe brain damage resulting from repetitive head injury in sports, and evaluated the pathophysiology of sports-related repetitive injury.

METHODS

We reviewed the literature containing detailed descriptions of repetitive severe sports-related head injury. In total, 18 cases were analyzed with regard to age, gender, type of sports, symptoms before second injury, and pathology of brain CT scans.

RESULTS

The majority of cases involved young males aged 16 to 23 years old, who sustained a second head injury before symptoms from the first head injury had resolved. Ten of 15 cases did not suffer loss of consciousness at insult. Eight cases were confirmed on brain CT scans after the second injury, and all 8 cases revealed brain swelling associated with a thin subdural hematoma.

CONCLUSIONS

Second impact syndrome is thought to occur because of loss of autoregulation of cerebral blood flow, leading to vascular engorgement, increased intracranial pressure, and eventual herniation. Our investigation suggests that the existence of subdural hematoma is a major cause of brain swelling following sports-related, repetitive head injury.

Matrix metalloproteinase-9 is associated with blood-brain barrier opening and brain edema formation after cortical contusion in rats

Matrix metalloproteinases (MMPs) are associated with blood-brain opening and may be involved in the pathophysiology of acute brain injury. Previous research demonstrated that knockout mice deficient in MMP-9 subjected to transient focal cerebral ischemia had reduced blood-brain barrier (BBB) disruption and attenuated cerebral infarction. In this study, we examined MMP-9 up-regulation, BBB disruption, and brain edema formation after cortical impact injury in rats. Cortical contusion was induced by controlled cortical impact. Animals were sacrificed at intervals after injury. MMP up-regulation was assessed by gelatin zymography, and BBB integrity was evaluated using Evans blue dye with a spectrophotometric assay. Brain water content was measured by comparing wet and dry weights of each hemisphere as an indicator of brain edema. Zymograms showed elevated MMP-9 as early as at 3 hours after injury, reaching a maximum at 18 hours. Peak levels of BBB disruption occurred 6 hours after injury. Brain edema became progressively more severe, peaking 24 hours after injury. Compared to control group, treatment with MMP-inhibitor GM6001 significantly reduced BBB disruption 6 hours and brain water content (85.9 +/- 0.5% vs. 82.6 +/- 0.3%; p < 0.05) 24 hours after injury. These findings suggest that MMP-9 may contribute to BBB disturbance and subsequent brain edema after traumatic brain injury.

Surgical management of early massive edema caused by cerebral contusion in head trauma patients

Early massive edema caused by severe cerebral contusion results in elevation of intracranial pressure (ICP) and clinical deterioration within 24-72 hours post-trauma. Previous studies indicate that cells in the central area of the contusion undergo shrinkage, disintegration, and homogenization, whereas cellular swelling is predominant in the peripheral area, suggesting that early massive edema is attributable to high osmolality within necrotic brain tissue and may generate an osmotic potential across central and peripheral areas. We analyzed the effects of surgical excision of necrotic brain tissue in 182 patients with cerebral contusion registered with Japan Neurotrauma Data Bank; 121 patients (66%; Group I) were treated conservatively, and 61 (34%; Group II) were treated surgically. Most Group II cases (90%) underwent complete excision of necrotic brain tissue and evacuation of clots. Group I demonstrated higher mortality at 6 months post-trauma compared to Group II (48%) vs. 23%; p = 0.0001; n = 182). Striking differences were observed in patients scoring 9 or more on Glasgow Coma Scale at admission (56% vs. 17%); p = 0.017; n = 45) and demonstrated "talk-and-deteriorate" (64% vs. 22%: p = 0.026; n = 29), supporting our hypothesis that early massive edema is caused by cerebral contusion accompanied by necrotic brain tissue, indicating that surgical excision of necrotic brain tissue provides satisfactory control of progressive elevation in ICP and clinical deterioration in many cases.

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.

Endothelin-1 enhances capsaicin-evoked intracellular Ca2+ response via activation of endothelin a receptor in a protein kinase Cε-dependent manner in dorsal root ganglion neurons

Increasing evidence indicates that endothelin-1 has a role for peripheral nociceptive signaling in animals and humans. However, the mechanisms of the nociceptive effects of endothelin-1 have not been fully understood. The current study investigated the effects of endothelin-1 on the capsaicin-evoked intracellular Ca2+ response of cultured adult mice dorsal root ganglion neurons. Dorsal root ganglia were harvested from adult male C57B6N mice and were cultured. With a digital image analysis system, we detected the [Ca2+]i image of cultured dorsal root ganglion cells after loading with Fura-2 acetoxymethyl. In addition, co-localization of protein kinase Cepsilon with transient receptor potential V1 and the translocation of protein kinase Cepsilon were investigated using immunohistochemical methods. Endothelin-1 (10 nM) enhanced an increase in [Ca2+]i by capsaicin (10 nM) from 87.6+/-11.6 nM to 414.8+/-62.3 nM (71 of 156 neurons). The inhibition of endothelin A receptor (BQ-123) significantly suppressed the enhancing effect of endothelin-1. In addition, a nonselective protein kinase C inhibitor (bisindolylmaleimide I) significantly suppressed the enhancing effect of endothelin-1. A myristoyl-tagged membrane-permeant-protein kinase Cepsilon V1-2 inhibitory peptide also significantly suppressed the enhancing effect of endothelin-1. In the immunocytochemical study, protein kinase Cepsilon immunoreactivity was found in most of transient receptor potential V1-positive neurons. After endothelin-1 application, protein kinase Cepsilon immunoreactivity was observed to be translocated from the cytosol to the cell membrane in transient receptor potential V1-positive neurons. Our results indicate that endothelin-1 enhances the response of dorsal root ganglion neurons to capsaicin in a protein kinase Cepsilon-dependent manner. Our findings may lead to a new strategy to treat pain associated with endothelin-1.

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.

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.

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.

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.

Experimental model for investigating hyponatremia after subarachnoid hemorrhage in rats

Hyponatremia is a common complication in patients with aneurysmal subarachnoid hemorrhage (SAH). Such patient demonstrates excessive natriuresis and an increased risk of symptomatic cerebral vasospasm. However, the precise mechanisms underlying SAH induced hyponatremia remain unclear. In the present study, in order to establish an experimental model of hyponatremia following SAH, we induced SAH in rats, and evaluated the serum sodium (Na) levels, Na excretion and physiological parameters. Twenty-four male Wistar rats were used. SAH was induced by an endovascular puncture method. The mean arterial pressure (MAP), intracranial pressure (ICP), and cerebral blood flow (CBF) were monitored continuously. The urine was collected cumulatively for 12 hours after SAH, and the urine Na concentration was determined with a spectrophotometer. The serum Na levels were measured at 12 hrs, 2 and 4 days following the SAH induction. The mean (+/- standard deviation) baseline ICP was 3.5 +/- 2.6 mmHg, and increased to 67.4 +/- 17.6 mmHg immediately following induction of SAH. CBF decreased rapidly, and then gradually recovered to 70-80% of baseline. The urine volume and total Na excretion were significantly increased in comparison to those of the sham (P < 0.05). The serum Na level was significantly decreased at 4 days following SAH (P < 0.05). The present results demonstrated for the first time that rats with SAH exhibited excessive natriuresis. The endovascular puncture model is suitable for investigating hyponatremia that occurs concomitantly with natriuresis and diuresis after SAH.

Extravascular application of an intravascular ultrasound (IVUS) catheter during carotid endarterectomy to verify distal ends of stenotic lesions

BACKGROUND

Intravascular ultrasound (IVUS) has been developed initially for intravascular imaging of coronary arteries to investigate vascular structures. We applied the IVUS catheter extravascularly to the cervical carotid arteries to obtain intra-operative ultrasound images during carotid endarterectomy (CEA). Intra-operative assessments of the distal ends of the stenotic lesions as well as pathological vascular structures are important, not only for exposing the lesions sufficiently but also for placing the shunt system safely.

METHOD

An IVUS catheter (3.2 French/30 MHz) was intra-operatively applied close to the outer surface of the cervical carotid arteries during CEA. Ultrasound transection vascular images were obtained in 33 consecutive patients (30 males and 3 females) with a mean age of 66.5 years.

FINDINGS

In 32 of 33 cases, extravascular application of IVUS catheter before making arteriotomies correctly depicted the distal ends of the internal carotid artery (ICA) stenotic lesions as a thin layer of vascular wall [0.64 +/- 0.16 mm (mean +/- SD) compared with 1.66 +/- 0.42 mm for carotid plaque] with intravascular blood flow. Based on the IVUS findings, we were able to adequately expose the normal ICA portion distal to the stenotic lesion before making the arteriotomy even in cases with stenotic lesions at very high positions, and to insert shunts safely. Furthermore, the properties of lesions and blood flow were also verified. However, it was difficult to examine the far vascular wall.

CONCLUSIONS

Extravascular application of IVUS catheter is efficient for intra-operative evaluation of the distal end of the stenotic lesion especially in cases with stenotic lesions at very high positions and cases in whom pre-operative angiograms did not clearly demonstrate the distal end. The findings also demonstrate the properties of lesions and completeness of CEA.

[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.

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.