Long-term maintenance of mature hippocampal slices in vitro.

Cultures of primary neurons or thin brain slices are typically prepared from immature animals. We introduce a method to prepare hippocampal slice cultures from mature rats aged 20-30 days. Mature slice cultures retain hippocampal cytoarchitecture and synaptic connections up to 3 months in vitro. Spontaneous epileptiform activity is rarely observed suggesting long-term retention of normal neuronal excitability and of excitatory and inhibitory synaptic networks. Picrotoxin, a GABAergic Cl(-) channel antagonist, induced characteristic interictal-like bursts that originated in the CA3 region, but not in the CA1 region. These data suggest that mature slice cultures displayed long-term retention of GABAergic inhibitory synapses that effectively suppressed synchronized burst activity via recurrent excitatory synapses of CA3 pyramidal cells. Mature slice cultures lack the reactive synaptogenesis, spontaneous epileptiform activity, and short life span that limit the use of slice cultures isolated from immature rats. Mature slice cultures are anticipated to be a useful addition for the in vitro study of normal and pathological hippocampal function.

Chronic and cyclical neuronal loss in hippocampal slice cultures following transient inhibition of the type 1 isoform of superoxide dismutase.

Increased oxidative stress contributes to chronic neurodegenerative diseases, yet the underlying mechanisms are poorly understood. Hippocampal slice cultures prepared from 20-30-day-old mice or rats were used to model chronic neuronal loss following oxidative stress. Neuronal loss was initiated by inhibition of the antioxidant enzyme, superoxide dismutase type 1 (SOD1), using the copper chelator diethyldithiocarbamate (DDC). Continuous DDC treatment of slice cultures induced delayed neuronal loss beginning at 9 days of treatment that lasted for over 4 weeks. Neuronal loss was not uniform, rather it was cyclic: peaking at days 9-13 and at days 19-21 after DDC exposure. Neuronal loss was significantly attenuated in slice cultures that overexpress SOD1, suggesting that SOD1 inhibition was responsible. Inhibitors of nitric oxide synthase also attenuated DDC-induced neuronal loss. Chronic neuronal loss, however, did not require continuous SOD1 inhibition. Application of DDC for 13 days resulted in loss of SOD1 activity. Removal of DDC restored SOD1 activity, yet the cycles of cell loss continued until no neurons remained. Astrocyte activation was observed following the second peak of neuronal loss. Media conditioned by cultures following DDC removal induced neuronal loss and microglial activation in recipient cultures. These data suggest that slice cultures released soluble neurotoxic factor(s) following DDC removal. These data also suggest that a transient reduction of SOD1 activity leads to chronic loss of hippocampal neurons. This neuronal loss may be mediated by soluble neurotoxic factor(s) and microglial activation. Cyclical neuronal loss may also underlie chronic neurodegeneration in vivo.

DynaCT evaluation of in-stent restenosis following Wingspan stenting of intracranial stenosis.

OBJECTIVE AND IMPORTANCE: To describe the use of DynaCT angiographic imaging for the evaluation of Wingspan in-stent restenosis (ISR). METHODS: Two patients were treated with Wingspan stenting and percutaneous transluminal angioplasty (Patient 1 had treatment of a severe stenosis of the right middle cerebral artery and patient 2 had severe stenosis of the left intracranial internal carotid artery. Both patients developed ISR and were evaluated with high resolution DynaCT angiographic imaging. RESULTS: DynaCT demonstrated circumferential soft tissue density material distributed within the stent as the cause of the stenosis visualized with conventional angiography. CONCLUSIONS: These findings support the hypothesis that ISR is caused by neointimal proliferation, rather than vascular re-coil with stent collapse.

Endovascular treatment of carotid embolic occlusions has a higher recanalization rate compared with cardioembolic occlusions.

BACKGROUND AND PURPOSE: Treatment of large artery cerebral occlusions is rapidly evolving. We hypothesized that patients with intracranial embolic occlusions secondary to an extracranial carotid artery stenosis or occlusion have a higher probability of successful endovascular recanalization compared with those with cardioembolic occlusions. METHODS: We retrospectively reviewed the databases of three institutions (University of Pittsburgh Medical Center (UPMC), Michigan State University (MSU) and Cleveland Clinic Foundation (CCF)) for acute anterior circulation ischemic strokes treated with endovascular therapies from January 2006 to July 2008. After collection of demographic, radiographic and angiographic variables, two groups were identified: artery to artery embolic occlusions and cardioembolic/cryptogenic intracranial occlusions. We defined recanalization as TIMI 2 or 3 flow. A binary logistic regression model was constructed to determine which characteristics were unique to patients with carotid embolic occlusions. RESULTS: A total of 207 patients were identified (UPMC=100, CCF=71, MSU=36) with a mean age of 69±11 years and mean NIHSS of 17±5. Of these, 157 (75%) were due to a cardiac or cryptogenic source and 50 (25%) were from a carotid embolic source. The use of multimodal therapy (OR 2.6 (1.2-5.6), p<0.009) and the presence of a carotid embolic intracranial occlusion (OR 3.6 (1.2-7.1), p<0.012) were associated with successful recanalization, while carotid terminus occlusions were associated with unsuccessful recanalization (OR 0.35 (0.18-0.68), p<0.002). CONCLUSIONS: Patients with intracranial occlusions secondary to an extracranial carotid stenosis or total occlusion appear to have more successful recanalization rates when treated with endovascular therapy compared with those with cardioembolic occlusions.

Cumulative radiation dose during hospitalization for aneurysmal subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Radiation exposure from neurointerventional procedures and diagnostic neuroimaging can be substantial, with many recommendations offered to guide the interventionalist in the conscientious use of ionizing radiation. Patients presenting with an aneurysmal subarachnoid hemorrhage can undergo multiple imaging procedures during a prolonged hospital course. Therefore, we reviewed a cohort of such patients to identify the sources and quantify the cumulative radiation exposure seen during their hospitalization. MATERIALS AND METHODS: We retrospectively reviewed a single-center experience with these patients to define the potential for short-term skin injury and long-term oncologic risk due to absorbed radiation dose and sources of ionizing radiation and their contribution to the cumulative absorbed dose to the cranial tissues. RESULTS: We demonstrated that substantial cumulative doses can be seen, with 87% of the cumulative absorbed dose occurring during neurointerventional procedures and 7% from CT. Mathematic modeling was performed identifying potential techniques to further reduce the cumulative radiation absorbed dose to these patients. CONCLUSIONS: We conclude that repetitive irradiation during the care of patients with aneurysmal subarachnoid hemorrhage can result in significant cumulative doses and a variety of techniques can be applied to reduce this absorbed dose. Use of radiation for diagnostic and therapeutic purposes during prolonged procedures of patients with subarachnoid hemorrhage demands diligence throughout the hospitalization.

Impact of WASID and Wingspan on the frequency of intracranial angioplasty and stenting at a high volume tertiary care hospital.

BACKGROUND AND PURPOSE: The impact of the Warfarin and Aspirin for Symptomatic Intracranial Disease (WASID) data is described in combination with the commercial release of the Wingspan stenting system on the frequency of neurointervention for the treatment of symptomatic intracranial atherosclerotic disease (ICAD) in a tertiary care center. METHODS: Endovascular case logs were reviewed from April 2004 to July 2007. The total number of intracranial neurointerventions and the number of neurointerventions (percutaneous transluminal angioplasty alone (PTA) or with stenting (PTAS)) performed for symptomatic ICAD were calculated. The time period evaluated was divided into two equal 19.5-month epochs representing the time periods before and after the availability of the Wingspan system. RESULTS: The frequency of neurointerventions for ICAD increased by 763%, from seven of 354 total cases (2%) to 56 of 367 total cases (15.3%) (p<0.001) after the Wingspan system became available. The increase in intracranial PTAS volume occurred immediately and was stable throughout the "Wingspan era". CONCLUSIONS: The publication of the WASID trial results combined with the availability of the Wingspan stent system led to a marked increase in the frequency of neurointervention for symptomatic ICAD at our institution. The adoption of this technology occurred without direct evidence that PTAS with Wingspan is superior to traditional medical therapy. These findings underscore the need for a randomized trial of stenting and medical therapy for the treatment of this disease process.

Delayed migration of a self-expanding intracranial microstent.

A 43-year-old patient with a basilar apex aneurysm had a 4.5-mm x 14-mm Enterprise stent placed from the midbasilar artery to the left P1 segment of the posterior cerebral artery. The patient experienced vertigo 4 months after stent placement and 1 week after stopping clopidogrel. At 5 months postembolization, angiography showed stent migration into the proximal basilar artery. This is the first described case of the spontaneous delayed migration of a self-expanding intracranial microstent.

Acidosis induces necrosis and apoptosis of cultured hippocampal neurons.

Acidosis, hypoxia, and hypoglycemia rapidly and transiently appear after reduction of cerebral blood flow. Acidosis also accompanies head trauma and subarachnoid hemorrhage. These insults result in necrotic and apoptotic loss of neurons. We previously demonstrated that transient acidification of intracellular pH from 7.3 to 6.5 induces delayed neuronal loss in cultured hippocampal slices (49). We now report that acidosis induced both necrotic and apoptotic loss of neurons. Necrosis and apoptosis were distinguished temporally and pharmacologically. Necrosis appeared rapidly and was dose dependent with the duration of the acidosis treatment. Apoptosis was delayed with maximal number of apoptotic cells seen with a 30-min acidosis treatment. Apoptotic neuronal loss was accompanied by DNA fragmentation and was blocked by inhibitors of protein and RNA synthesis, ectopic expression of the anti-apoptotic gene bcl-2, or an inhibitor of caspases, proteases known to be activated during apoptosis. Necrotic neuronal loss was unaffected by these treatments. Hypothermia, a treatment known to attenuate neuronal loss following a variety of insults, blocked both acidosis-induced necrosis and apoptosis. These results indicate that acidosis is neurotoxic in vitro and suggest that acidosis contributes to both necrotic and apoptotic neuronal loss in vivo.