Development of Action Potential Waveform in Hippocampal CA1 Pyramidal Neurons.

CA1 pyramidal neurons undergo intense morphological and electrophysiological changes from the second to third postnatal weeks in rats throughout a critical period associated with the emergence of exploratory behavior. Using whole cell current-clamp recordings in vitro and neurochemical methods, we studied the development of the somatic action potential (AP) waveform and some of the underlying channels in this critical period. At the third postnatal week, APs showed a more hyperpolarized threshold, higher duration and amplitude. Subthreshold depolarization broadened APs and depolarized their peak overshoots more pronouncedly in immature neurons (2 weeks old). These features were mimicked by pharmacologically blocking the fast-inactivating A-type potassium current (IA) and matched well with the higher concentrations of Kv4.2 and Kv4.3 and the lower concentrations of BK and Kv1.2 channels detected by Western blotting. Repetitive stimulation with high frequency trains (50 Hz) reproduced AP broadening associated to inactivation of the A-type current in immature cells. Moreover, repetitive firing showed changes in AP amplitude consistent with the inactivation of both sodium and potassium subthreshold currents, which resulted in higher AP amplitudes in the more immature neurons. We propose that maturation of AP waveform and excitability in this critical developmental period could be related to the onset of exploratory behaviors.

Primary central nervous system lymphoma and 5-aminolevulinic acid.

BACKGROUND: Despite surgical resection of primary central nervous system lymphomas (PCNSL) having been always discouraged, recent evidence supports that it might improve prognosis in this patient population. Five- aminolevulinic acid-derived fluorescence is widely used for the resection of malignant gliomas, but its role in PCNSL surgery remains unclear. CASE DESCRIPTION: We present two patients with a solitary solid intraparenchymal mass. As high-grade glioma leaded the list of differential diagnosis (other possibilities were metastasis, abscess, and PCNSL), a five- aminolevulinic acid-guided complete resection (with strong fluorescence in both cases) was done. Surgery was uneventfully carried on with complete resection until five-aminolevulinic acid-induced fluorescence was no longer evident. After surgery, patients have no neurological deficits and had good recovery. Pathological examination revealed that both tumors were PCNSL. Adjuvant radiotherapy and chemotherapy were started. After 1 year of follow-up, patients have good evolution and have no recurrences. CONCLUSION: These cases add to the growing literature which shows that surgery might play an important role in the management of PCNSL with an accessible and single lesion. Five-aminolevulinic acid could also be a useful tool to achieve complete resection and improve prognosis in this group of patients.

Optical coherence tomography: Translation from 3D-printed vascular models of the anterior cerebral circulation to the first human images of implanted surface modified flow diverters.

BACKGROUND: The new generation of flow diverters includes a surface modification with a synthetic biocompatible polymer, which makes the device more biocompatible and less thrombogenic. Optical coherence tomography (OCT) can be used to visualize perforators, stent wall apposition, and intra-stent thrombus. Unfortunately real world application of this technology has been limited because of the limited navigability of these devices in the intracranial vessels. In this report, we share our experience of using 3D-printed neurovascular anatomy models to simulate and test the navigability of a commercially available OCT system and to show the application of this device in a patient treated with the new generation of surface modified flow diverters. MATERIAL AND METHODS: Navigability of OCT catheters was tested in vitro using four different 3D-printed silicone replicas of the intracranial anterior circulation, after the implantation of surface modified devices. Intermediate catheters were used in different tortuous anatomies and positions. After this assessment, we describe the OCT image analysis of a Pipeline Shield for treating an unruptured posterior communicating artery (PCOM) aneurysm. RESULTS: Use of intermediate catheters in the 3D-printed replicas was associated with better navigation of the OCT catheters in favorable anatomies but did not help as much in unfavorable anatomies. OCT image analysis of a PCOM aneurysm treated with Pipeline Embolization Device Shield demonstrated areas of unsatisfactory apposition with no thrombus formation. CONCLUSIONS: OCT improves the understanding of the flow diversion technology. The development of less thrombogenic devices, like the Pipeline Flex with Shield Technology, reinforces the need for intraluminal imaging for neurovascular application.

Internal Carotid Artery Reconstruction with a "Mega Flow Diverter": First Experience with the 6×50 mm DERIVO Embolization Device.

Endoluminal reconstruction with a flow diverter device has emerged as a viable and often preferable alternative to traditional techniques for the treatment of intracranial aneurysms. Precise measurement and device selection are mandatory steps when considering flow diverters usage in order to avoid potential complications. In this sense, incomplete wall-apposition has been described as a predictive factor for immediate in-stent and delayed thrombosis after stent use. One significant usage limitation of flow diverter devices is the parent artery diameter, since the maximum opening of the sizes available are recommended for vessel diameters between 5.2-5.75 mm. Here we present the first clinical use of the largest flow diverter available, the 6×50 mm DERIVO embolization device (Acandis GmbH & Co. KG, Pforzheim, Germany), into the arterial circulation for a cervical internal carotid artery endovascular reconstruction. This is a new device for large or fusiform aneurysms requiring flow diversion, especially located in the vertebrobasilar system or extracranial segments.