Fatal hemorrhagic complication after coil embolization of a petrosal arteriovenous shunt

BACKGROUND

Cerebello-pontine AVMs (CPAVMs) and petrous apex dural arteriovenous fistulae (DAVFs) are rare and sometimes difficult to distinguish. We report a fatal hemorrhagic complication after coil embolization of the petrosal vein draining a trigeminal AVM misdiagnosed as a DAVF.

CASE PRESENTATION

A 73-year-old woman with a petrous apex arteriovenous shunt with dual dural and pial arterial supply presented with posterior fossa hemorrhage. The draining petrosal vein was catheterized and coiled via the superior petrosal sinus. Two episodes of contrast extravasation occurred during coiling, but the lesion was completely occluded at the end of the procedure. The patient developed a fatal posterior fossa hemorrhage in the recovery room. Microscopic pathology revealed numerous dilated vessels within the trigeminal nerve.

CONCLUSION

CPAVMs and DAVFs with pial drainage should be distinguished pre-operatively. Occlusion of a pial vein (as opposed to a sinus) in the treatment of an arteriovenous shunt carries hemorrhagic risk if a liquid embolic agent is not used to completely occlude all pathological vessels.

BIOS-02. CLINICAL OUTCOMES OF OVER 600 PATIENTS WITH GLIOBLASTOMA TREATED AT A CANADIAN TERTIARY CENTER IN THE PAST 15 YEARS: A COMPARATIVE ANALYSIS WITH THE PIVOTAL STUPP TRIAL

Glioblastoma is the most common malignant primary central nervous system tumor in adults and is associated with a poor prognosis. The benefit of adding concomitant followed by adjuvant temozolomide to radiotherapy after maximal safe resection was demonstrated by Stupp and colleagues in 2005 and has since remained the standard of care. This regimen conferred a statistically significant benefit with a 2-year survival rate of 26.5% compared to 10.4% in patients treated with radiotherapy alone. Our primary goal was to retrospectively assess the clinical outcomes of patients with glioblastoma treated at our institution over the past 15 years by comparing the overall survival (OS) and progression-free survival (PFS) from our cohort to data from the pivotal trial. Our secondary objective was to create a comprehensive database with clinical and pathological information in order to identify predictive and prognostic factors. We reviewed the clinical records of patients treated for glioblastoma from January 2005 to November 2019 at our center. We extracted data on survival and calculated OS and PFS using the Kaplan-Meier method. 617 patient charts were reviewed, out of which 17 were excluded because of missing data. The remaining 600 patients were included. Baseline demographic information was similar to that of the Stupp cohort, with the exception of a larger proportion of patients aged 50 or above (76% versus 69%, respectively). The median OS at our center was 14.3 months, 95% confidence interval [12.8-15.2], which was comparable to that of the original trial (14.6 months [13.2-16.8]). PFS was better in our cohort at 6 months (74.2% [70.7-77.7] versus 53.9% [48.1-59.6]) and 12 months (36.3% [32.5-40.2] versus 26.9% [21.8-32.1]), and comparable thereafter. Our study confirms that the data from the Stupp trial are reproducible in a Canadian academic center setting. Our database will allow us to explore potentially new predictive factors.

PATH-10. A CASE OF ADULT THALAMIC DIFFUSE MIDLINE GLIOMA, H3 K27-ALTERED WITH AN IMPRESSIVE RESPONSE TO RADIOTHERAPY AND CONCOMITANT PLUS ADJUVANT TEMOZOLOMIDE

Diffuse midline glioma (DMG), H3 K27-altered is a newly defined diagnosis in the 2021 WHO Classification of Tumors of the Central Nervous System. H3 K27 alterations are associated with a uniformly poor prognosis in children with DMG, but they have been linked to improved survival in adults. Clinical experience in adults with DMG, H3 K27M-altered remains limited. Consequently, there exists a knowledge gap regarding the optimal management and responsiveness to chemoradiation therapy, which translates into the current absence of standard treatment. Here we present the case of an 18-year-old female patient treated for a thalamic DMG, H3 K27-altered at a Canadian tertiary center. The patient first presented with headache, dysarthria, and signs of increased intracranial pressure. Her initial brain magnetic resonance imaging demonstrated a right thalamo-mesencephalic lesion with central nodular enhancement and secondary hydrocephalus. She underwent an endoscopic third ventriculostomy followed by a subtotal resection, and pathology confirmed the presence of a DMG, H3 K27-altered, WHO grade 4. She was treated with combined radiotherapy and concomitant plus adjuvant (12 cycles) temozolomide. The Stupp regimen induced a spectacular response with a reduction in tumor dimensions on T2/FLAIR (20 x 18 mm versus 60 x 51 mm), > 50% decrease in size of the enhancing component, complete resolution of mass effect, and return to functional independence (KPS = 100%). Unfortunately, her disease progressed 16 months after diagnosis and she passed away 8 months later, despite having received 3 cycles of ONC201 through a clinical trial. Her progression-free survival (16 months) was superior to that reported in the literature, which could be related to her young age, subtotal resection status, and thalamic location. Although the addition of chemotherapy to adjuvant radiotherapy has not been shown to improve survival in children with DMG, the Stupp regimen may provide a survival benefit in adults.

Adult Medulloblastoma Demographic, Tumor and Treatment Impact since 2006: A Canadian University Experience

Medulloblastoma is an aggressive primary brain tumor that is extremely rare in adults; therefore, prospective studies are limited. We reviewed the information of all MB patients treated at the CHUM between 2006 and 2017. We divided our cohort by age and further divided adult patients (53%) in two groups, those diagnosed between 2006–2012 and 2013–2017. In our adult population, median follow up was 26 months and SHH-activated MB comprised 39% of tumors. Adult 5yOS was 80% and first-line therapy led to a 5yPFS of 77%. The absence of radiosensitizing chemotherapy (100% vs. 50%; p = 0.033) negatively influenced 5yPFS. 96% of adult patients received radiotherapy and 48% of them received concomitant radiosensitizing chemotherapy. Complete surgical resection was performed on 85% of adults, but the extent of resection did not have a discernable impact on survival and did not change with time. Adjuvant chemotherapy did not clearly affect prognosis (5yOS 80% vs. 67%, p = 0.155; 5yPFS 78% vs. 67%, p = 0.114). From 2006–2012, the most common chemotherapy regimen (69%) was Cisplatinum, Lomustine and Vincristine, which was replaced in 2013 by Cisplatinum, Etoposide and Cyclophosphamide (77%) with a trend for worse survival. Nine patients recurred and seven of these (78%) were treated with palliative chemotherapy. In conclusion, we did not identify prognostic demographic or tumor factors in our adult MB population. The presence of radiosensitizing chemotherapy was associated with a more favorable PFS. Cisplatinum, Lomustine and Vincristine regimen might be a better adjuvant chemotherapy regimen.

Vulvar Cutaneous Myxoma in a Patient With Carney Complex: Avoiding Pitfalls of Myxoid Lesions of the Vulva

We present the case of a 31-year-old woman who underwent surgical excision for a polypoid, vulvar lesion. Histopathological analysis showed a diffuse myxoid stroma admixed with scant collagen fibrils. Thin-walled and branching blood vessels were prominent, with a mild perivascular lymphocytic infiltrate. Cytologically bland spindle cells with inconspicuous nucleoli were immersed in a loose myxoid stroma. This combination of histopathological features along with multinodularity in the subcutaneous fat raised concern for deep angiomyxoma, a locally destructive neoplasm. Among our differential of myxoid lesions of the vulva, we ultimately favored the diagnosis of vulvar cutaneous myxoma. Upon further investigation, we learned that our patient was indeed known for the Carney complex. We highlight that vulvar cutaneous myxomas arising in the context of the Carney complex pose a significant diagnostic challenge for pathologists and should not be overdiagnosed as aggressive lesions such as deep angiomyxoma or other malignant stromal neoplasms.

Corticotroph tumor progression during long-term therapy with osilodrostat in a patient with persistent Cushing's disease

PURPOSE

Corticotroph tumor progression (CTP) or Nelson's syndrome (NS) can occur in patients with Cushing's disease (CD) following bilateral adrenalectomy. It has rarely been observed in patients treated with long-term medical therapy for persistent CD. Osilodrostat (LCI699) is a new steroidogenesis inhibitor of 11β-hydroxylase (CYP11β1) that induced remission of hypercortisolism in 86% of patients with refractory CD in the randomized placebo-controlled trial LINC-3 (NCT02180217).

METHODS

A 40-year-old woman with persistent CD following transsphenoidal surgery was treated with osilodrostat in the LINC-3 trial and was followed with regular hormonal assessments and imaging of residual corticotroph tumor.

RESULTS

Under oral therapy with osilodrostat 10 mg twice daily, urinary free cortisol (UFC) normalized and clinical signs of CD regressed during therapy. However after 4 years of treatment, ACTH levels increased from 73 to 500 pmol/L and corticotroph tumor size increased rapidly from 3 to 14 mm, while UFCs remained well controlled. Surgical resection of an atypical tumor with weak ACTH expression and increased proliferative index (Ki-67 ≥ 8%) resulted in current remission but will require close follow-up.

CONCLUSION

This case highlights the importance of monitoring ACTH and corticotroph tumor size in patients with persistent CD, either under effective treatment with steroidogenesis inhibitors or after bilateral adrenalectomy.

Successful Management of Natalizumab-Associated Primary Central Nervous System Lymphoma through Autologous Stem Cell Transplant

Natalizumab is used as a second-line treatment for multiple sclerosis (MS). Some reports have linked natalizumab to primary central nervous system lymphoma (PCNSL), although few have described its management. A 45-year-old woman with Balo’s Concentric Sclerosis presented dizziness, vertigo accompanied by dysarthria, weakness on the left side and blurred vision to the right eye after the fourth dose of natalizumab. Magnetic resonance imaging (MRI) and a brain biopsy confirmed the diagnosis of PCNSL. The patient received modified PCNSL chemotherapy (MATRix protocol) followed by high-dose chemotherapy (HDC) supported by an autologous hematopoietic stem cell transplant (ASCT) as a consolidation therapy. Thirty months later, she is still in complete remission of her PCNSL and MS. In this case, whole brain radiotherapy was excluded because it may be associated with an increased risk of neurotoxicity in MS. ASCT was preferred because it has been shown to prevent disability progression in less advanced MS stages. Our patient is the second to receive an ASCT in this context and this option of treatment should be the preferred if the patient is eligible.

HOUT-14. PROGNOSTIC IMPACT OF FIRST PSEUDOPROGRESSION ON MRI IN GLIOBLASTOMA, AN 11 YEARS EXPERIENCE FROM A CANADIAN UNIVERSITY CENTER

BACKGROUND

In glioblastomas (GBM) patients the first post-radiation MRI is usually difficult to interpret given the post-radiotherapy enhancement and possible pseudo-progression which is present in almost 50% of the patients.

METHODS

We retrospectively analyzed all patients with GBM treated between 2006 and 2017 at the CHUM (SARDO database). If the first brain MRI done within 3 months after the systemic treatment showed progression of contrast, these patients were considered pseudoprogressors (PsP) while the patients who had stable or response to treatment were the non-progressors (nP). If progression persisted in subsequent MRI with a change of treatment within 6 months, they were considered early progressors (eP). If subsequent MRI improved or was stable, they were classified as nP (or true pseudo-progression).

RESULTS

In our cohort of 470 patients with GBM, 57.7% were nP and 42.3% were PsP after the first post-treatment imagery. The median follow-up was 10 months. The nP had a longer mOS 15.3m vs 11.3m, p < 0.001, regardless of subsequent evolution. After the second assessment, 67.8% of PsP patients were then considered as eP and 36.4% of nP patients also progressed within 6 months. The nP either after the first or second evaluation had the same mOS (19.9m vs 18.3m), just like the eP (9.3m vs 8.6m), independently of the subsequent treatment. No demographic, molecular or clinical factor predicted PsP, except for tumor size (> 5cm, p=0.024). PsP incidence was similar between 2006–2011 (PsP 57.8%) and 2012–2017 (42.2%). The 1y OS with pseudo progression at the first MRI was 39.7% vs 54.8% with no progression (p=0.001) which has a meaningful impact for the patient.

CONCLUSION

Pseudo-progression is frequent (42%) in glioblastoma and predicts a poorer prognosis with 1y OS of 39,7%. In fact, PsP patients have more than two-thirds chance to progress precociously.

HOUT-23. ADULT MEDULLOBLASTOMA TREATMENT IMPACT SINCE 2006: A CANADIAN UNIVERSITY CENTER EXPERIENCE

INTRODUCTION

Medulloblastoma (MB) is an aggressive primary brain tumor rare in adults. Prospective studies in adults are limited by the small number of patients.

METHODS

We retrospectively reviewed all MB patients treated at the CHUM between 2006 and 2017 in our clinical database adult SARDO. We don’t have the children follow up. We divided our cohort in 2 groups, those diagnosed between 2006–2013 and those diagnosed between 2014–2017.

RESULTS

49 patients were treated, 23 (47%) were children referred for radiation only from a pediatric center and 26 (53%) were adults. Median follow up of adults was 26 months. At 5 years, the entire cohort OS was 58%, but specifically for adults, the 5yOS was 80%. First line therapy had a 5y PFS 77% for adults, negatively influenced by the absence of adjuvant radiotherapy (83% vs 0%; p < 0.001) and the absence of adjuvant chemotherapy (80% vs 39%; p < 0.008). 96% of adult patients received radiotherapy and 52% of them received concomitant radiosensitizing chemotherapy with no impact on survival. Complete surgical resection was performed on 88% of patients, but the extent of resection did not have an impact on survival and did not change with time. From 2006–2013, the most common chemotherapy treatment (80%) in adults was Vincristine, Cisplatin and Lomustine. From 2014–2017, the chemotherapy was replaced by Cisplatin, Etoposide and Cyclophosphamide in 82% with no impact on survival (specific mortality for this chemo 3yOS 100% for both, 3y PFS 100%). Non Cisplatin based chemotherapy regimens were associated with decrease in PFS (67% at 3y). 78% of the progressive patients received second line chemo.

CONCLUSION

In our adult MB population, the demographic and tumor factors did’nt have an impact on prognosis but adjuvant radiotherapy and chemotherapy had a favorable impact on survival especially with Cisplatin, Etoposide and Cyclophosphamide regimen.

HOUT-28. FIRST-LINE TEMOZOLOMIDE VS PCV FOR LOW GRADE GLIOMAS: A 11 YEARS REAL-WORLD DATA FROM CHUM, UNIVERSITY CENTER

BACKGROUND

Before 2012, Temozolomide (TMZ) was used for low-grade gliomas (LGG) to avoid Lomustine toxicity. After 2012 RTOG data, Procarbazine, Lomustine and Vincristine (PCV) given sequentially with radiotherapy became standard treatment with the side effects burden associated.

METHODS

We retrospectively reviewed our SARDO clinical database of patients with low-grade glioma LGG grades 2 and 3 between 2006 and 2017 at CHUM University Health Center. Molecular profile for these tumors is reflex and standard in our institution since 2016.

RESULTS

A total of 123 patients were identified with grade 2 and grade 3 LGG; 37 (30%) treated with PCV and 86 (70%) received TMZ. Median follow up was 11mo for PCV 11mo vs 22mo TMZ. Both groups were balanced in terms of median age, sex, neurologic symptoms and surgery rate. 53% patients had tumor untested for IDH1-2 and codeletion1p19q because of diagnostic before 2016. Disparities were noted with a predominance of grade 3 in the TMZ group (74% vs 27%, p< 0.01). TMZ was the preferred regimen before 2012 (100% vs 43%) and PCV became the standard of care after 2012 (0% vs 57%). Radiation use as first line treatment was 90%. The 4y OS was not significantly longer for PCV 50% compared with TMZ 47% with mOS between both groups (PCV NR vs TMZ 39.9mo, p=0.158). When controlled for tumor grade, the 2y OS was 80% for PCV vs 64% for TMZ,p=0.542. The 4y PFS was trendly longer for PCV group 78% than TMZ group 45%, p=0.148.

CONCLUSION

As we are still waiting for the prospective ongoing prospective trials comparing these 2 regimens, PCV and radiation are still standard of care regimens for grade 2 and 3 LGG. This retrospective data is not reassuring for a replacement for PCV with TMZ.

Procarbazine, lomustine and vincristine toxicity in low-grade gliomas

Background

Procarbazine, lomustine, and vincristine (pcv) significantly improve survival outcomes in lgg (low-grade gliomas). Administration of pcv to lgg patients increased tremendously over the past years as it went from 2 patients per year between 2005 and 2012 to 23 patients in 2015 only in our centre. However, serious hematological and non-hematological adverse events may occur. The purpose of this study was to evaluate the toxicity of pcv and its clinical relevance in our practice.

Methods

We retrospectively reviewed the charts of 57 patients with lgg who received pcv at the Centre hospitalier de l'Université de Montréal between 1 January 2005 and 27 July 2016.

Results

Procarbazine, lomustine, and vincristine were associated with severe hematological toxicity as clinically significant grade 3 anemia, neutropenia, and thrombocytopenia occurred in 7%, 10%, and 28% of patients, respectively. Other frequent adverse events such as the increase of liver enzymes, cutaneous rash, neurotoxicity, and vomiting occurred in 65%, 26%, 60%, and 40% of patients, respectively. Patients with prophylactic trimethoprim/sulfamethoxazole had more grade 3 hematological toxicity with pcv, especially anemia (p = 0.040) and thrombocytopenia (p = 0.003) but we found no increase in pcv toxicity in patients on concurrent anticonvulsants. Patients with grade 3 neutropenia had a significantly lower survival (median survival 44.0 months vs. 114.0 months, p = 0.001). Patients who were given pcv at diagnosis had more grade 3 anemia than those who received it at subsequent lines of treatment (p = 0.042).

Conclusion

Procarbazine, lomustine, and vincristine increase survival in lgg but were also associated with major hematologic, hepatic, neurologic, and cutaneous toxicity. Anti-Pneumocystis jiroveci pneumonia (pjp) prophylaxis, but not anticonvulsants, enhances hematologic toxicity.

Efficiency of Crizotinib on an ALK-Positive Inflammatory Myofibroblastic Tumor of the Central Nervous System: A Case Report

Inflammatory myofibroblastic tumors (IMT) of the central nervous system (CNS) are rare entities that have a predilection for local recurrences. Approximately half of the inflammatory myofibroblastic tumors contain translocations that result in the over-expression of the anaplastic lymphoma kinase (ALK) gene. We hereby present the case of a patient diagnosed with a left parieto-occipital IMT that recurred after multiple surgeries and radiotherapy. Immuno-histochemical examination of the tumor demonstrated ALK overexpression and the presence of an ALK rearrangement observed in lung cancers. The patient was subsequently started on an ALK inhibitor. A response evaluation criteria in solid tumors (RECIST) partial response was observed by the seventh month of ALK inhibition and the tumor remained in control for 14 months. The current case reiterates the activity of ALK inhibitors within the CNS and suggests that radiotherapy may potentiate the permeability of ALK inhibitors in CNS tumors addicted to ALK signalling.

Fatal avulsion of choroidal or perforating arteries by guidewires. Case reports, ex vivo experiments, potential mechanisms and prevention

Innovations in endovascular tools have permitted an increasingly broad range of neurovascular lesions to be treated via minimally invasive methods. However, some device modifications may carry additional risks, not immediately apparent to operators. A patient with a symptomatic, partially thrombosed basilar apex aneurysm was allocated balloon-assisted coiling. Attempts were made to place a microwire across the basilar apex through the posterior communicating artery. Overlapping courses of the posterior cerebral and posterior choroidal arteries on the roadmap images were not recognized and a flanged-tip microwire was inadvertently advanced deep into the choroidal artery. Following the wire with a microcatheter led to binding of arterial tissue within the microcatheter. Removing the wire led to an avulsion of the choroidal artery and a severe hemorrhagic complication which proved fatal. Tissue was identified on the tip of the guidewire. Pathology showed layers of vascular tissue within the laser-cut flanges of the distal wire tip. A similar complication, also fatal, occurred during balloon angioplasty of a distal vertebral artery, when an exchange wire was accidently introduced into a perforator from a posterior cerebral artery. Ex vivo catheterization of distal mesenteric arterial branches showed that the wall of small arteries can be entrapped by laser-cut, flanged, but not by smooth guidewire tips. Microwires with a flanged instead of smooth distal tip, when placed into small caliber vessels, may cause hemorrhagic complications from avulsions*.

Inflammatory myofibroblastic tumors of the central nervous system that express anaplastic lymphoma kinase have a high recurrence rate

Background:

Inflammatory myofibroblastic tumors (IMTs) of the central nervous system (CNS) are rare entities with diverse histopathological features and varying propensities to recur.

Case Description:

A 26 year-old male with an IMT of the CNS of the left tentorium had tumor progression 2 months after partial surgical resection. Histopathological studies confirmed expression of ALK. Macroscopic total resection was performed followed by radiotherapy. A recurrence occurred 20 months after the second surgery that necessitate reoperation. Including the present case, we identified 30 cases of IMT of the CNS corresponding to our search criteria in the literature. The extent of resection was reported in 26 of these cases. Gross total resection was done in 75% of ALK-positive and in 61% of ALK-negative cases. Recurrence rate after gross total resection for ALK-positive and ALK-negative cases was 33% and 9%, respectively. Every recurrence in ALK-positive patients occurred within 2 years after surgery.

Conclusion:

IMT of the CNS are a heterogeneous group of tumors and the treatment of choice is complete surgical resection. Because of the high recurrence rate reported for IMT of the CNS expressing ALK, a closed follow-up is recommended. When faced with an early recurrence, a surgical resection followed by radiotherapy may be advised.

Aneurysm rupture after endovascular flow diversion: the possible role of persistent flows through the transition zone associated with device deformation

Haemorrhagic complications can occur following aneurysm treatment with flow diverters (FD), but the underlying mechanism remains unknown. We describe a case where deformation of the device may have contributed to the complication. A patient with a giant, previously unruptured cavernous aneurysm that extended intracranially to cause oedema of the internal capsule was treated with flow diversion. Treatment was followed by multiple episodes of peri-aneurysmal haemorrhages within eight days. A deformation of the device which occurred where it curved to cross the aneurysm neck created residual flows which, in the presence of a stent stenosis immediately beyond the neck, may have contributed to the observed ruptures. Following multiple haemorrhages the patient subsequently died. Autopsy demonstrated early red thrombus partially bridging the struts of the flow diverter, and intra-aneurysmal thrombus of various ages. Microscopic pathology showed an aneurysm wall consisting of collagen infiltrated with neutrophils, but the wall was absent near the cerebral peduncle, adjacent to the brain haemorrhage. Radiographs of the extracted specimen confirmed deformation of the FD construct, located at the transition zone of the stent, leading to increased pore size and porosity. The site of the deformation correlated with the angiographic presence of a continued blood inflow jet into the aneurysm. Stent deformation at the transition zone may promote persistent blood entry into the aneurysm, and in turn potentially contribute to haemorrhagic complications.

A 30 year old man with an acute presentation of a cerebellopontine angle lesion

Schwannomas are slow-growing tumors with symptoms manifesting progressively. We report the case of a patient who manifested a sudden loss of consciousness as clinical presentation of an intracranial schwannoma with no acute hemorrhage or hydrocephalus. A 30-year-old male presented comatose and posturing. Cerebral CT revealed an extra-axial lesion with a heterogeneous enhancement and a cystic component located on the right cerebellopontine angle (CPA), displacing the brain stem. No acute hemorrhage or hydrocephalus was documented. Through a retrosigmoid suboccipital craniotomy, an extended subtotal tumor resection was performed. The patient experienced no functional hearing impairment and resumed his daily-life activities 3 months after surgery. Histopathological examination was compatible with a benign schwannoma. An exuberant lymphoplasmacytic infiltrate was found in many areas, signing the presence of an unusual inflammatory reaction with adjacent important intratumoral edema. We propose that the exuberant inflammatory infiltrate and the associated intratumoral edema acted as determining elements in the increase of mass effect and sudden clinical deterioration.

Thrombosis heralding aneurysmal rupture: an exploration of potential mechanisms in a novel giant swine aneurysm model

BACKGROUND AND PURPOSE

The relationship between aneurysm dimensions, flow, thrombosis, and rupture remains poorly understood. We attempted to clarify this relationship by exploring various swine aneurysm models.

MATERIALS AND METHODS

Bilateral carotid aneurysms were constructed according to 3 protocols in 24 animals: small aneurysms with wide necks (group 1; n = 6 animals); small aneurysms with small necks (group 2; n = 4 animals), and giant aneurysms with large necks (group 3; n = 14 animals). Group 3 included 3 subgroups, related to testing the model in various experimental conditions: The neck was clipped in 3 animals; venous pouches lacked an endothelial lining in 4 animals; and 7 were control animals. Animals were followed until rupture, or for 1-4 weeks. Angiography was performed postoperatively and before euthanasia. We studied lesion pathology, paying attention to thrombosis, recanalization, wall composition, and perianeurysmal hemorrhage.

RESULTS

Groups differed significantly in aneurysm dimensions and aspect ratio (P = .002). Ruptures occurred more frequently in animals with untreated giant aneurysms (7/7) than in animals with small wide-neck (0/6) or small-neck (2/4) aneurysms (P = .002). Ruptures occurred only in animals with thrombosed aneurysms. Lesions lacking an endothelial lining and 5 of 6 clipped venous pouches thrombosed but did not rupture. One giant lesion ruptured despite complete clipping. The wall was deficient in α-actin and was infiltrated with inflammatory cells and erythrocytes in all thrombosed cases, ruptured or not. Ruptures were associated with recanalizing channels in 9 of 10 cases.

CONCLUSIONS

Thrombosis, inflammation, and recanalization may precipitate aneurysmal ruptures in a swine model.

Failure of temozolomide and conventional doses of pegvisomant to attain biochemical control in a severe case of acromegaly

It has been suggested that treatment with adequate dose titration of pegvisomant, a GH antagonist, up to a maximum of 40 mg daily, can achieve IGF-1 normalisation in virtually all patients with acromegaly. On the other hand, temozolomide (TMZ), an alkylating cytostatic agent, has been reported to reduce pituitary tumour size and hormone hypersecretion in a small number of aggressive pituitary macroadenomas. In this paper we report the case of a patient resistant to very high doses of pegvisomant used in combination with somatostatin analogs (SSA) and to TMZ therapy. The patient, initially a 22 year-old man with an invasive GH-secreting pituitary macroadenoma (IGF-1, 371% upper limit of normal), had active acromegaly despite a repeat transsphenoidal surgery followed by radiotherapy and SSA (octreotide 800 μg sc daily) (IGF-1, 262% ULN). In combination with SSA, pegvisomant was started at 20 mg daily and doses were titrated up to 60 mg daily. IGF-1 was moderately reduced and stabilized at 200% ULN after 1 year of treatment. Serum pegvisomant level was 30,500 ng/l, the denaturalized GHBP concentration 1,120 pM and the endogenous GH level was 220 μg/l. Pegvisomant was stopped and TMZ therapy was given for 5 cycles. However, the patient reported an increase of acromegaly symptoms and the serum IGF-1 was raised to the same level prior to pegvisomant therapy. Consequently, pegvisomant was tried again with doses up to 100 mg daily finally resulting in normalisation of serum IGF-1 level and improvement of acromegaly symptoms and patient well-being. We conclude that in some patients with severe acromegaly refractory to multimodal therapy, biochemical control may be difficult to attain with conventional doses of pegvisomant or TMZ therapy.

Cooperation between cyclin E and p27(Kip1) in pituitary tumorigenesis

Cushing's disease is caused by glucocorticoid-resistant pituitary corticotroph adenomas. We have previously identified the loss of nuclear Brg1 as one mechanism that may lead to partial glucocorticoid resistance: this loss is observed in about 33% of human corticotroph adenomas. We now show that Brg1 loss of function correlates with cyclin E expression in corticotroph adenomas and with loss of the cell cycle inhibitor p27(Kip1) expression. Because Brg1 is thought to have tumor suppressor activity, the present study was undertaken to understand the putative contribution of cyclin E derepression produced by loss of Brg1 expression on adenoma development. Overexpression of cyclin E in pituitary proopiomelanocortin cells leads to abnormal reentry into cell cycle of differentiated proopiomelanocortin cells and to centrosome instability. These alterations are consistent with the intermediate lobe hyperplasia and anterior lobe adenomas that were observed in these pituitaries. When combined with the p27(Kip1) knockout, overexpression of cyclin E increased the incidence of pituitary tumors, their size, and their proliferation index. These results suggest that cyclin E up-regulation and p27(Kip1) loss-of-function act cooperatively on pituitary adenoma development.

An unusual association of a sellar gangliocytoma with a prolactinoma

The simultaneous occurrence of a hypothalamic and sellar gangliocytoma with a pituitary prolactinoma is very rare. The explanation for such an association is not known. We describe the case of a woman who had a coexisting adjacent pituitary prolactinoma and gangliocytoma within the same sellar mass. The tumor cells of the gangliocytoma demonstrated expression of enkephalin, a product of proopiomelanocortin known to be a prolactin secretagogue. We postulate that in this patient there may be a link between gangliocytoma enkephalin and prolactin hypersecretion.

Angiotensin II controls occludin function and is required for blood brain barrier maintenance: relevance to multiple sclerosis

The blood-brain barrier (BBB) restricts molecular and cellular trafficking between the blood and the CNS. Although astrocytes are known to control BBB permeability, the molecular determinants of this effect remain unknown. We show that angiotensinogen (AGT) produced and secreted by astrocytes is cleaved into angiotensin II (AngII) and acts on type 1 angiotensin receptors (AT1) expressed by BBB endothelial cells (ECs). Activation of AT1 restricts the passage of molecular tracers across human BBB-derived ECs through threonine-phosphorylation of the tight junction protein occludin and its mobilization to lipid raft membrane microdomains. We also show that AGT knock-out animals have disorganized occludin strands at the level of the BBB and a diffuse accumulation of the endogenous serum protein plasminogen in the CNS, compared with wild-type animals. Finally, we demonstrate a reduction in the number of AGT-immunopositive perivascular astrocytes in multiple sclerosis (MS) lesions, which correlates with a reduced expression of occludin similarly seen in the CNS of AGT knock-out animals. Such a reduction in astrocyte-expressed AGT and AngII is dependent, in vitro, on the proinflammatory cytokines tumor necrosis factor-alpha and interferon-gamma. Our study defines a novel physiological role for AngII in the CNS and suggests that inflammation-induced downregulation of AngII production by astrocytes is involved in BBB dysfunction in MS lesions.

Role of Brg1 and HDAC2 in GR trans-repression of the pituitary POMC gene and misexpression in Cushing disease

Negative feedback regulation of the proopiomelanocortin (POMC) gene by the glucocorticoid (Gc) receptor (GR) is a critical feature of the hypothalamo-pituitary-adrenal axis, and it is in part exerted by trans-repression between GR and the orphan nuclear receptors related to NGFI-B. We now show that Brg1, the ATPase subunit of the Swi/Snf complex, is essential for this trans-repression and that Brg1 is required in vivo to stabilize interactions between GR and NGFI-B as well as between GR and HDAC2. Whereas Brg1 is constitutively present at the POMC promoter, recruitment of GR and HDAC2 is ligand-dependent and results in histone H4 deacetylation of the POMC locus. In addition, GR-dependent repression inhibits promoter clearance by RNA polymerase II. Thus, corecruitment of repressor and activator at the promoter and chromatin modification jointly contribute to trans-repression initiated by direct interactions between GR and NGFI-B. Loss of Brg1 or HDAC2 should therefore produce Gc resistance, and we show that approximately 50% of Gc-resistant human and dog corticotroph adenomas, which are the hallmark of Cushing disease, are deficient in nuclear expression of either protein. In addition to providing a molecular basis for Gc resistance, these deficiencies may also contribute to the tumorigenic process.

Intra-parenchymal mesenchymal chondrosarcoma of the cerebellum: case report and review of the literature

A 44-year-old male presented with a 3-week history of clumsiness and numbness of the left hemibody. CT scan and MRI revealed a 2 cm mass in the right hemisphere of the cerebellum. The patient underwent a sub-occipital craniotomy with gross total resection of the intra-parenchymal lesion. On pathology, the lesion was found to be compatible with a mesenchymal chondrosarcoma. The patient received adjuvant radiation treatment and remains free of disease 60 months after completion of treatment. Mesenchymal chondrosarcomas are neoplasms that rarely arise intra-cranially. Thirty cases have been found in the literature. Our case resembles more closely six of these cases because the tumour had no dural attachment. We describe our case in more detail and review similar cases found in the English literature.

Down-regulation of caveolin-1 in glioma vasculature: modulation by radiotherapy

Primary brain tumors, particularly glioblastomas (GB), remain a challenge for oncology. An element of the malignant brain tumors' aggressive behavior is the fact that GB are among the most densely vascularized tumors. To determine some of the molecular regulations occuring at the brain tumor endothelium level during tumoral progression would be an asset in understanding brain tumor biology. Caveolin-1 is an essential structural constituent of caveolae that has been implicated in mitogenic signaling, oncogenesis, and angiogenesis. In this work we investigated regulation of caveolin-1 expression in brain endothelial cells (ECs) under angiogenic conditions. In vitro, brain EC caveolin-1 is down-regulated by angiogenic factors treament and by hypoxia. Coculture of brain ECs with tumoral cells induced a similar down-regulation. In addition, activation of the p42/44 MAP kinase is demonstrated. By using an in vivo brain tumor model, we purified ECs from gliomas as well as from normal brain to investigate possible regulation of caveolin-1 expression in tumoral brain vasculature. We show that caveolin-1 expression is strikingly down-regulated in glioma ECs, whereas an increase of phosphorylated caveolin-1 is observed. Whole-brain radiation treatment, a classical way in which GB is currently being treated, resulted in increased caveolin-1 expression in tumor isolated ECs. The level of tumor cells spreading around newly formed blood vessels was also elevated. The regulation of caveolin-1 expression in tumoral ECs may reflect the tumoral vasculature state and correlates with angiogenesis kinetics.

Adult Alexander disease with autosomal dominant transmission: a distinct entity caused by mutation in the glial fibrillary acid protein gene

BACKGROUND

Infantile and juvenile forms of Alexander disease are well characterized and are caused by de novo mutations in the glial fibrillary acid protein (GFAP) gene. In contrast, the adult form of the disease has been rarely described, and the etiology of this variant remains unknown.

OBJECTIVE

To characterize the clinical phenotype and identify the gene causing an autosomal dominant form of adult Alexander disease.

METHODS

We identified a large kindred segregating clinical features compatible with adult Alexander disease in an autosomal dominant fashion. A neurological examination was performed on all affected members of this family. Most of these patients also underwent magnetic resonance imaging of the brain and a polysomnographic study. The diagnosis was confirmed pathologically in 2 individuals. We screened all coding regions of the GFAP gene in affected individuals by means of direct sequencing and single-stranded conformational polymorphisms analysis.

RESULTS

We found a novel D78E mutation in GFAP in all affected individuals. This mutation was not detected in more than 100 control subjects. Clinical and radiological features of affected individuals were clearly different from those of patients with the infantile and juvenile forms of the disease. The most consistent finding was the presence of bulbar signs. In addition, sleep disturbance (mainly sleep apnea), symptoms of dysautonomia, and dysmorphism were found in all affected individuals. In younger patients, magnetic resonance imaging showed T2 signal abnormalities in the medulla compatible with an area of demyelination. In contrast, in older patients, we found marked atrophy of the medulla without signal abnormalities. None of the affected individuals exhibit signs of demyelination of the cerebral white matter.

CONCLUSIONS

The present study is the first demonstration of a mutation in GFAP that causes an autosomal dominant form of Alexander disease and establishes the existence of the adult variant. Clinical evaluation in individuals carrying mutation in the GFAP gene allowed a better definition of this heterogeneous clinical syndrome and will help increase its recognition in neurological practice.

Differences in multidrug resistance phenotype and matrix metalloproteinases activity between endothelial cells from normal brain and glioma

Endothelial cells (ECs) are new targets for tumor therapy. In this work, we purified endothelial cells from intracerebral and subcutaneous experimental gliomas as well as from normal brain in order to define some of the phenotypical differences between angiogenic and quiescent brain vasculature. We show that the multidrug resistance genes encoding drug efflux pumps at the brain endothelium are expressed differently in normal and tumoral vasculature. We also show that ECs from gliomas present increased activity of gelatinase B (MMP9), key enzyme in the angiogenic process. Importantly, we observe a different phenotype between ECs in the intracerebral and subcutaneous models. Our results provide molecular evidence of phenotypic distinction between tumoral and normal brain vasculature and indicate that the EC phenotype depends on interactions both with tumor cells and also with the microenvironment.

Multidrug resistance in brain tumors: roles of the blood-brain barrier

Malignant brain tumors and brain metastases present a formidable clinical challenge against which no significant advances have been made over the last decade. Multidrug resistance (MDR) is one of the main factors in the failure of chemotherapy against central nervous system tumors. The MDR1 gene encoding P-glycoprotein (P-gp), a drug efflux pump which plays a significant role in modulating MDR in a wide variety of human cancers, is highly expressed in the blood-brain barrier (BBB). The BBB controls central nervous system exposure to many endogenous and exogenous substances. The exact molecular mechanisms by which the BBB is involved in the resistance of brain tumors to chemotherapy remain to be identified. The purpose of this review is to summarize reports demonstrating that P-gp, one of the most phenotypically important markers of the BBB, is present in primary brain tumors and thus plays a crucial role in their clinical resistance to chemotherapy.

Drug transport to the brain: key roles for the efflux pump P-glycoprotein in the blood-brain barrier

1. The blood-brain barrier (BBB) contributes to brain homeostastis and fulfills a protective function by controlling the access of solutes and toxic substances to the central nervous system (CNS). The efflux transporter P-glycoprotein (P-gp) is a key element of the molecular machinery that confers special permeability properties to the BBB. 2. P-gp, which was initially recognized for its ability to expel anticancer drugs from multidrug-resistant cancer cells, is strongly expressed in brain capillaries. Its expression in the BBB limits the accumulation of many hydrophobic molecules and potentially toxic substances in the brain. 3. The purpose of this review is to summarize the current state of knowledge about the expression of P-gp, its cellular localization as well as its possible functions in the BBB.

The expression of rho proteins decreases with human brain tumor progression: potential tumor markers

Astrocytic tumors are the most common human brain tumors. Establishment of tumor grade is a key determinant both in the choice of a therapeutic approach and in the prognosis. The diagnosis of astrocytic tumors is currently determined following histopathological analysis. The identification of molecular markers would offer a complementary tool for characterizing tumors with respect to their clinical behavior. In this study we determined the expression levels of 3 small GTP binding proteins (RhoA, RhoB and Rac1), of their inhibitor RhoGDI and of caveolin-1 in 24 human astrocytic tumors of grades I to IV. Our results demonstrated that the expression of RhoA and RhoB decreased significantly in all brain tumors studied and was inversely related with tumor of grade II to IV malignancy. The amount of caveolin-1 immunodetected was not significantly different from normal brain samples while the Rac1 expression level was diminished in astrocytic tumors of grades III and IV. Our finding that RhoA and RhoB expression levels are correlated to tumor malignancy suggests that they may serve as novel and efficient diagnostic markers for astrocytic brain tumors of histological grade II to IV and complement currently applied histopathological analysis.

Cyanoacrylate embolization of experimental aneurysms

BACKGROUND AND PURPOSE

Cyanoacrylates are effective occlusive agents in neurovascular interventions. To study their potential to improve long-term results of endovascular treatment of aneurysms, we conducted experimental studies in canine aneurysm models.

METHODS

Venous pouch carotid aneurysms were constructed in dogs. Results of coil embolization of lateral wall and bifurcation aneurysms were compared. A lateral wall model of embolization with gelatin sponges was used to study the effects of coating sponges with cyanoacrylate on angiographic results and neointima thickness at 3 and 12 weeks. These models were also used to investigate the control of endovascular cyanoacrylate deposition, alone or over a coil placed at the neck of the treated lesions. The results of endovascular cyanoacrylate embolization of bifurcation aneurysms were compared with those of coil embolization at 3 months.

RESULTS

Bifurcation aneurysms treated with coils showed more frequent recurrences (P <.01) and thinner neointimas (P <.01) at 3 months than did lateral wall aneurysms. Cyanoacrylate-coated sponges improved angiographic results (P <.05) and led to thicker neointimas at 3 and 12 weeks (P <.05) as compared with uncoated sponges. Endovascular cyanoacrylate deposition with microcatheters led to stray emboli in all cases. Cyanoacrylate delivery was improved by a single coil positioned at the neck of the aneurysm, but parent vessel embolization still occurred in 25% of the animals. Cyanoacrylate embolization of bifurcation aneurysms improved angiographic results at 3 months as compared with coil embolization (P <.01).

CONCLUSION

Cyanoacrylate embolization is currently difficult to control. It has the potential to decrease recurrences after endovacular treatment of aneurysms, but a safe method for endovascular delivery has yet to be developed.

Expression of multidrug-resistance P-glycoprotein (MDR1) in human brain tumors

Multidrug resistance (MDR) is associated with the expression of P-glycoprotein (P-gp), an ATP-dependent transporter which expels anti-cancer drugs from cells. In the present study, MDR1 P-gp was immunodetected by Western blot analysis in 60 human brain tumors, including meningiomas, schwannomas, low-grade gliomas (astrocytomas, pilocytic astrocytomas) and high-grade gliomas (anaplastic astrocytomas, glioblastomas and anaplastic oligodendrogliomas). Most samples from primary tumors expressed P-gp at the same levels as normal brain tissue except for schwannomas, in which levels were reduced by 65%, and meningiomas, in which levels were more than 10-fold higher in 7 of 10 samples. P-gp levels were 70% and 95% lower in brain metastases from melanomas and lung adenocarcinomas, respectively, than in normal brain tissue. These results indicate that the majority of primary brain tumors express MDR1 P-gp and that its high expression levels in meningiomas may be a marker for this type of brain tumor.

Isolation of endothelial cells from brain, lung, and kidney: expression of the multidrug resistance P-glycoprotein isoforms

Endothelial cells (EC) were isolated from brain, lung, and renal cortex using magnetic microbeads cross-linked to an antibody directed against the platelet-endothelial cell adhesion molecule-1 (PECAM-1). Levels of endothelial nitric oxide synthase (eNOS) and PECAM-1 were measured by Western blots and both were enriched in the positively selected EC fractions. The multidrug resistance P-glycoprotein (P-gp) was strongly enriched (59-fold) in the EC fraction from brain and was absent in the negative fraction, in which the glial fibrillary acidic protein (GFAP), an astrocyte marker, was present. Lower P-gp levels were detected in EC from renal cortex and lung. Reverse transcription-polymerase chain reaction analysis showed that the mdr1a gene was preferentially expressed in EC fraction from the brain. The mdr1b gene was found in EC from renal cortex whereas both mdr1 genes were detected in EC from lung. Our results indicate that EC can be isolated using microbeads and that the isoform of P-gp found in brain is mostly mdr1a, associated with EC.

Expression of matrix metalloproteinases and their inhibitors in human brain tumors

Sixty human brain tumors, classified according to the New World Health Organization (WHO) classification including, grade I schwannomas, meningiomas and pilocytic astrocytomas, grade II astrocytomas, grade III anaplastic astrocytomas, grade IV glioblastomas, grade III anaplastic oligodendrogliomas and grade IV glioblastomas and lung and melanoma metastases were analyzed for the expression of three matrix metalloproteinases (MMPs), two tissue inhibitors of MMPs (TIMPs) and for MMP activity. Some correlation was found between MMP expression and the degree of malignancy. Western blotting analysis revealed a more uniform pattern of distribution of MMP-2 (gelatinase A) than of MMP-9 (gelatinase B) and MMP-12 (metalloelastase) among tumors. MMP-9 levels were found to be significantly higher in grade III anaplastic astrocytomas and anaplastic oligodendrogliomas than those in grade I schwannomas and meningiomas. Anaplastic astrocytomas and Grade IV glioblastomas expressed significantly higher levels MMP-12 than grade I meningiomas. All sixty tumors showed a similar pattern of activity in zymography, proMMP-9 being the major species detected. Interestingly, TIMP-1 and TIMP-2 expression levels were especially low in tumors of grade II and grade III but significantly higher in tumors of grade I, particularly in schwannomas. Taken together, these data suggest that: 1) a balance between MMPs and TIMPs has an important role to play in human brain tumors; 2) TIMP expression may be valuable markers for tumor malignancy.

Expression of matrix metalloproteinases and their inhibitors in human brain tumors

Sixty human brain tumors, classified according to the New World Health Organization (WHO) classification including, grade I schwannomas, meningiomas and pilocytic astrocytomas, grade II astrocytomas, grade III anaplastic astrocytomas, grade IV glioblastomas, grade III anaplastic oligodendrogliomas and grade IV glioblastomas and lung and melanoma metastases were analyzed for the expression of three matrix metalloproteinases (MMPs), two tissue inhibitors of MMPs (TIMPs) and for MMP activity. Some correlation was found between MMP expression and the degree of malignancy. Western blotting analysis revealed a more uniform pattern of distribution of MMP-2 (gelatinase A) than of MMP-9 (gelatinase B) and MMP-12 (metalloelastase) among tumors. MMP-9 levels were found to be significantly higher in grade III anaplastic astrocytomas and anaplastic oligodendrogliomas than those in grade I schwannomas and meningiomas. Anaplastic astrocytomas and Grade IV glioblastomas expressed significantly higher levels MMP-12 than grade I meningiomas. All sixty tumors showed a similar pattern of activity in zymography, proMMP-9 being the major species detected. Interestingly, TIMP-1 and TIMP-2 expression levels were especially low in tumors of grade II and grade III but significantly higher in tumors of grade I, particularly in schwannomas. Taken together, these data suggest that: 1) a balance between MMPs and TIMPs has an important role to play in human brain tumors; 2) TIMP expression may be valuable markers for tumor malignancy.

Expression of matrix metalloproteinases and their inhibitors in human brain tumors

Sixty human brain tumors, including grade I meningiomas, schwannomas, and pilocytic astrocytomas, grade II astrocytomas, grade III anaplastic astrocytomas and oligodendrogliomas, and grade IV glioblastomas and lung and melanoma metastases were analyzed for expression of four matrix metalloproteinases (MMPs), two tissue inhibitors of MMPs (TIMPs), and MMP activity. No marked correlation was found between MMP expression and the degree of malignancy. Western blotting analysis revealed a more uniform pattern of distribution of MMP-2 (gelatinase A) than of MMP-9 (gelatinase B) and MMP-12 (metalloelastase) among tumors. All 60 tumors showed a similar pattern of activity in zymography, MMP-2 being the major species detected. Interestingly, TIMP-1 and TIMP-2 expression levels were low in tumors of grade III but significantly higher in tumors of grade I, particularly schwannomas. Altogether, these data suggest that: (1) the balance between MMP-2 and TIMP-2 is important in human brain tumors; and (2) TIMP expression may be a valuable marker for tumor malignancy.

Interrelationship between organelles in kidney cells of adult and developing rat

The morphologic interrelationships between mitochondria, the endoplasmic reticulum (ER) and other organelles were examined in rat kidney cells by stereomicroscopy of thick sections (0.3-1.0 micron) using either standard transmission (80-100 kV) or high voltage (1 mEV) electron microscopy. Mitochondria fit into three different categories: (1) elongated cylinders observed in S1 and S2 segments; (2) irregular lamina in the cortical ascending limb or plates in the distal straight and convoluted segments; (3) small spheres or short rods mostly in intercalated and principal cells of the collecting tubule. The chondrioma occupies a large volume in all cells except in the thin limb and in principal cells of the collecting tubule. This volume occupied by the chondrioma is likely to be related to metabolic functions, but its polymorphic configuration could also be explained by a passive adaptation of the mitochondria to the space left by the basilar membrane infoldings and the ER network, which was found to have an extensive three-dimensional organization which varies, as for the mitochondria, with the cell type. In fact, in the proximal nephron, mitochondria surrounded by the ER and the plasma membranes appear to form a functional unit. Organelle interrelationship is extensively modified during ontogeny or under hormonal influence. Disruption in organelle relationships or in their motility could probably have far reaching consequences which would be more deleterious than the pathological lesions observed at the level of a single organelle. The extent of the disassembly can be fully explored only with thick sections and stereomicroscopy.

Dopaminergic projection from nucleus raphe dorsalis to neostriatum in the rat

The existence of a dopamine (DA) projection from nucleus raphe dorsalis (RD) to neostriatum was demonstrated in the rat by combined tyrosine hydroxylase (TH) immunohistochemistry and radioautography after retrograde axonal transport of [3H]noradrenaline ([3H]NA). Intrastriatal injections of [3H]NA were carried out in normal rats or after ipsilateral destruction of the nigrostriatal DA system by injection of 6-hydroxydopamine (6-OHDA) into the substantia nigra. Some 1,000 TH-positive nerve cell bodies were counted within the confines of RD as defined by its content in serotonin (5-HT) neurons. These DA neurons occupied the upper third of the RD and they were part of its small cell population. In all cases, a small proportion of the TH-immunoreactive nerve cell bodies in RD were retrogradely radiolabeled. Radiolabeled but immunonegative cells were exceedingly rare. The double-labeled neurons were generally more numerous after elimination of the nigrostriatal DA innervation than in normal rats. They mostly lay within the ventral portion of the medial subdivision of RD and always predominated on the [3H]NA- injected side. Some were also present in nucleus linearis caudalis. It was concluded that [3H]NA had been taken up and retrogradely transported exclusively by catecholamine neurons; part of the DA cell group in RD projects to the neostriatum; and that most if not all non-5-HT neurons projecting from RD to neostriatum are likely to be dopaminergic.

[The dopaminergic innervation of neostriatum: a new possibility of radioautographic investigation (author's transl)]

Precise knowledge of the ultrastructural features and interneuronal relationships of dopaminergic (DA) axon terminals or varicosities in neostriatum is still lacking. This ignorance is due to current limitations of the methods applicable to their specific visualization at electron microscopic level. High resolution radioautography, in particular, has not yet permitted a clearcut identification of the DA nerve endings which take up and store exogenous catecholamines in vivo, due to an apparent mobilization of tracer during standard histological preparative procedures for light and electron microscopy (Fig. 1 A). In this context, histological processing of the central nervous system by vascular perfusion, tested in adult rats subjected to prolonged lateroventricular instillation of [3H]DA, led to the following results and conclusions: 1 Axonal varicosities having accumulated [3H]DA in vivo may be detected in great number in the ipsilateral paraventricular neostriatum (Figs. 1 B and 1 C). 2 The specificity of this radioautographic labelling is evidenced by: (a) its disappearance or persistance, depending on the addition of a high concentration of non-radioactive noradrenaline or serotonin to the [3H]DA solution (Fig. 1 C); (b) the absence of labelled axonal varicosities in the supraependymal region (Figs. 2 E and 2 F) and suprachiasmatic nucleus (Fig. 1 E to be compared with 1 F) after administration of [3H]DA alone; (c) the absence of any localized accumulation of [3H]DA in neostriatum following prior destruction of the nigro-striatal DA system by 6-hydroxydopamine (Fig. 1 D). 3 It seems that carrying out the double fixation with glutaraldehyde and osmium by vascular perfusion is the prerequisite for retaining in situ the [3H]DA accumulated in vivo by neostriatal nerve endings. 4 Preliminary ultrastructural examination shows that the DA axonal varicosities of paraventricular neostriatum are of small caliber (mean diameter: 0.5 micron) and mostly contain clear synaptic vesicles, occasionally associated with a few larger dense-core vesicles (figs. 2 A-D). Several of these nerve endings establish axo-dendritic synaptic junctions (Fig. 2 C) and a few, perhaps, axo-somatic contacts (Fig. 2 D).