Medication intake and hemorrhage risk in patients with familial cerebral cavernous malformations.

OBJECTIVE: The objective of this study was to analyze the impact of medication intake on hemorrhage risk in patients with familial cerebral cavernous malformation (FCCM). METHODS: The authors' institutional database was screened for patients with FCCM who had been admitted to their department between 2003 and 2020. Patients with a complete magnetic resonance imaging (MRI) data set, evidence of multiple CCMs, clinical baseline characteristics, and follow-up (FU) examination were included in the study. The authors assessed the influence of medication intake on first or recurrent intracerebral hemorrhage (ICH) using univariate and multivariate logistic regression adjusted for age and sex. The longitudinal cumulative 5-year risk of hemorrhage was calculated by applying Kaplan-Meier and Cox regression analyses adjusted for age and sex. RESULTS: Two hundred five patients with FCCMs were included in the study. Multivariate Cox regression analysis revealed ICH as a predictor for recurrent hemorrhage during the 5-year FU. The authors also noted a tendency toward a decreased association with ICH during FU in patients on statin medication (HR 0.22, 95% CI 0.03-1.68, p = 0.143), although the relationship was not statistically significant. No bleeding events were observed in patients on antithrombotic therapy. Kaplan-Meier analysis and log-rank test showed a tendency toward a low risk of ICH during FU in patients on antithrombotic therapy (p = 0.085), as well as those on statin therapy (p = 0.193). The cumulative 5-year risk of bleeding was 22.82% (95% CI 17.33%-29.38%) for the entire cohort, 31.41% (95% CI 23.26%-40.83%) for patients with a history of ICH, 26.54% (95% CI 11.13%-49.7%) for individuals on beta-blocker medication, 6.25% (95% CI 0.33%-32.29%) for patients on statin medication, and 0% (95% CI 0%-30.13%) for patients on antithrombotic medication. CONCLUSIONS: ICH at diagnosis was identified as a risk factor for recurrent hemorrhage. Although the relationships were not statistically significant, statin and antithrombotic medication tended to be associated with decreased bleeding events.

Multiple cerebral cavernous malformations: Clinical course of confirmed, assumed and non-familial disease.

BACKGROUND AND PURPOSE: Analyze and compare the natural course of confirmed familial cerebral cavernous malformation (FCCM), assumed FCCM and non-familial multiple cerebral cavernous malformation (CCM) disease over a 5-year period. METHODS: Our institutional database was screened for patients with CCM admitted between 2003 and 2020. Patients with complete magnetic resonance imaging dataset, evidence of multiple CCM, clinical baseline characteristics, and follow-up examination were included. Patients were separated into confirmed familial cases, assumed familial cases or non-familial multiple cavernous malformations. Kaplan-Meier and Cox regression analyses were performed to determine the cumulative 5-year risk for hemorrhage and recurrent hemorrhage. RESULTS: A total of 238 patients with multiple CCM were analyzed; 90 individuals had a confirmed FCCM disease, 115 an assumed FCCM, and 33 were allocated to the non-FCCM group. Univariate Cox regression analysis identified intracerebral hemorrhage (ICH) as mode of presentation (p = 0.001) as a predictor for occurrence of recurrent hemorrhage during the 5-year follow-up (FU). The cumulative 5-year risk of (re)bleeding was 21.6% for the entire cohort, 30.7% for patients with ICH at diagnosis, 22.1% for those patients with a confirmed diagnosis of FCCM, 23.5% for those with an assumed FCCM, and 21% for the non-FCCM cases. CONCLUSIONS: FCCM patients with ICH at diagnosis are prone to develop rebleeding. During untreated 5-year FU, FCCM patients and patients with sporadic multiple CCM reveal an almost equal susceptibility for (re)hemorrhage. Moreover, confirmed, assumed and non-FCCM patients showed an equal cumulative 5-year risk of symptomatic ICH. The probability of hemorrhage tends to increase over time, particularly in cases with ICH at presentation.

Natural Course of Cerebral Cavernous Malformations in Children: A Five-Year Follow-Up Study.

BACKGROUND AND PURPOSE: The purpose of this study was to investigate the natural course of cerebral cavernous malformations (CCM) in the pediatric population, with special emphasis on the risk of first and recurrent bleeding over a 5-year period. METHODS: Our institutional database was screened for patients with CCM treated between 2003 and 2020. Patients ≤18 years of age with complete magnetic resonance imaging data set, clinical baseline characteristics, and ≥1 follow-up examination were included. Surgically treated individuals were censored after CCM removal. We assessed the impact of various parameters on first or recurrent intracerebral hemorrhage (ICH) at diagnosis using univariate and multivariate logistic regression adjusted for age and sex. Kaplan-Meier and Cox regression analyses were performed to determine the cumulative 5-year risk for (re)hemorrhage. RESULTS: One hundred twenty-nine pediatric patients with CCM were analyzed. Univariate logistic regression identified brain stem CCM (odds ratio, 3.15 [95% CI, 1.15-8.63]; P=0.026) and familial history of CCM (odds ratio, 2.47 [95% CI, 1.04-5.86]; P=0.041) as statistically significant predictors of ICH at diagnosis. Multivariate logistic regression confirmed this correlation (odds ratio, 3.62 [95% CI, 1.18-8.99]; P=0.022 and odds ratio, 2.53 [95% CI, 1.07-5.98]; P=0.035, respectively). Cox regression analysis identified ICH as mode of presentation (hazard ratio, 14.01 [95% CI, 1.80-110.39]; P=0.012) as an independent predictor for rehemorrhage during the 5-year follow-up. The cumulative 5-year risk of (re)bleeding was 15.9% (95% CI, 10.2%-23.6%) for the entire cohort, 30.2% (20.2%-42.3%) for pediatric patients with ICH at diagnosis, and 29.5% (95% CI, 13.9%-51.1%) for children with brain stem CCM. CONCLUSIONS: Pediatric patients with brain stem CCM and familial history of CCM have a higher risk of ICH as mode of presentation. During untreated 5-year follow-up, they revealed a similar risk of (re)hemorrhage compared to adult patients. The probability of (re)bleeding increases over time, especially in cases with ICH at presentation or brain stem localization.

The occurrence of neuropathic pain following surgery of brainstem cavernous malformations.

BACKGROUND AND PURPOSE: This study aimed to assess the occurrence and significance of postoperative neuropathic pain (NP) in patients with surgically treated brainstem cavernous malformations (BSCMs). METHODS: Seventy-four BSCM patients surgically treated between 2003 and 2019 were reviewed for the occurrence of postoperative NP and related treatment. The relevance of BSCM location, preoperative characteristics, influence on functional outcome, postoperative health-related quality of life (HRQOL) and life satisfaction was evaluated. RESULTS: Six out of 74 patients (8%) suffered from NP. The Leeds Assessment of Neuropathic Symptoms and Signs scores ranged from 12 to 16 (mean 14.28 ± 1.6). Visual analog scale pain was 5.2 ± 2.0. NP had no effect on preoperative characteristics or functional outcome. Bodily pain (HRQOL) and vocational time (life satisfaction) were significantly decreased in NP compared to non-NP patients. Specific BSCM location (regarding brainstem nuclei involved in pain processing) and other preoperative patient- and BSCM-related parameters were not associated with the occurrence of postoperative NP. Three out of six patients were currently under NP-specific treatment. The proportion of patients suffering from postoperative NP (8%) was substantially higher compared to previously published studies. The pain affected the HRQOL of patients, most of whom were insufficiently treated and not satisfied with treatment results. CONCLUSION: Our findings may help to raise awareness for postoperative NP in BSCM, which is essential to improve diagnosis and initiation of proper treatment, as well as preoperative informed consent of patients.

Natural course of untreated spinal cord cavernous malformations: a follow-up study within the initial 5 years after diagnosis.

OBJECTIVE: Cavernous spinal cord malformations (SCMs) are believed to have a high rate of bleeding. The risk of intramedullary hemorrhage (IMH) or recurrent IMH and the neurological impact of bleeding events are important for clinical decision-making and could impact current treatment strategies. METHODS: The authors screened their institutional database for patients with cavernous SCM treated between 2003 and 2020. Patients with complete MRI data sets and clinical baseline characteristics were included. Surgically treated patients were censored after cavernous SCM removal. Neurological functional status was obtained using the modified McCormick (MMcC) scale at diagnosis, first IMH, and second IMH. Kaplan-Meier and Cox regression analyses were performed to determine the cumulative 5-year risk for hemorrhage or rehemorrhage. RESULTS: Seventy-one patients with cavernous SCM were analyzed. Cox regression analysis identified previous IMH (hazard ratio 7.86, 95% confidence interval 1.01-61.47, p = 0.049) as an independent predictor for rehemorrhage during the 5-year follow-up. The cumulative 5-year risk of bleeding or rebleeding was 41.3% for cavernous SCM. The MMcC score significantly deteriorated in 75% of patients after recurrent hemorrhage (p = 0.012). CONCLUSIONS: During untreated 5-year follow-up, a considerably increased risk for hemorrhage or rehemorrhage was found in cavernous malformations of the spinal cord compared to cerebral cavernous malformations. Neurological function significantly deteriorates after the second bleeding. The probability of recurrent IMH increased significantly after initial presentation with hemorrhage.

Effects of medication intake on the risk of hemorrhage in patients with sporadic cerebral cavernous malformations.

Objective: Recurrent intracerebral hemorrhage (ICH) poses a high risk for patients with cerebral cavernous malformations (CCMs). This study aimed to assess the influence of medication intake on hemorrhage risk in sporadic CCMs. Methods: From a database of 1,409 consecutive patients with CCM (2003-2021), subjects with sporadic CCMs and complete magnetic resonance imaging data were included. We evaluated the presence of ICH as a mode of presentation, the occurrence of ICH during follow-up, and medication intake, including beta blockers, statins, antithrombotic therapy, and thyroid hormones. The impact of medication intake on ICH at presentation was calculated using univariate and multivariate logistic regression with age and sex adjustment. The longitudinal cumulative 5-year risk for (re-)hemorrhage was analyzed using the Kaplan-Meier curves and the Cox regression analysis. Results: A total of 1116 patients with CCM were included. Logistic regression analysis showed a significant correlation (OR: 0.520, 95% CI: 0.284-0.951, p = 0.034) between antithrombotic therapy and ICH as a mode of presentation. Cox regression analysis revealed no significant correlation between medication intake and occurrence of (re-)hemorrhage (hazard ratios: betablockers 1.270 [95% CI: 0.703-2.293], statins 0.543 [95% CI: 0.194-1.526], antithrombotic therapy 0.507 [95% CI: 0.182-1.410], and thyroid hormones 0.834 [95% CI: 0.378-1.839]). Conclusion: In this observational study, antithrombotic treatment was associated with the tendency to a lower rate of ICH as a mode of presentation in a large cohort of patients with sporadic CCM. Intake of beta blockers, statins, and thyroid hormones had no effect on hemorrhage as a mode of presentation. During the 5-year follow-up period, none of the drugs affected the further risk of (re-)hemorrhage.

Cerebral cavernous malformations: Prevalence of cardiovascular comorbidities and allergic diseases compared to the normal population.

BACKGROUND: To determine the prevalence of cardiovascular comorbidities and allergic diseases in patients with cavernous malformations of the central nervous system compared to the normal population. METHODS: Clinical and magnetic resonance imaging data of 1352 patients with cerebral cavernous malformations (CCM) from an observational, cross-sectional, single-institutional study were analyzed and compared to an age-and-gender stratified and matched sample from a population-based, epidemiological study assessing cardiovascular risk factors in the local normal population of the same area (RECALL study). RESULTS: Of 1352 patients, 810 (60%) were female. Mean age was 40.4 ± 16 years. 221 patients (16%) suffered from familial disease. Presence of cardiovascular risk factors and intake of certain drugs in the overall cohort was mostly equal to the normal population reference sample (n = 786). The prevalence of allergic diseases was found to be significantly higher in all CCM patients compared to the normal population (30% vs. 20%, odds ratio [OR] 1.35 [1.12-1.63]) and in sporadic CCM cases compared to the normal population and familial cases (32% vs. 20% (OR 1.46 [1.19-1.78], p = 0.0001) and 22% vs. 20%, respectively). CONCLUSIONS: We present novel data on CCM using a large single-institution and population-based setup. The study elaborates disease characteristics of CCM patients in detail. For the first time, evidence for an unexplained high prevalence of allergic diseases in this patient population is described (differing between sporadic and familial cases), supporting the hypothesis that immune response is involved in the pathogenesis of CCM.

Modifiable Cardiovascular Risk Factors in Patients With Sporadic Cerebral Cavernous Malformations: Obesity Matters.

BACKGROUND AND PURPOSE: This study aims to assess the influence of modifiable cardiovascular risk factors on hemorrhage risk of sporadic cerebral cavernous malformations (CCMs). METHODS: From 1219 consecutive CCM patients (2003-2018), adult subjects with sporadic CCM and complete magnetic resonance imaging were included. We evaluated presence of intracerebral hemorrhage (ICH) as mode of presentation, occurrence of ICH during follow-up and risk factors arterial hypertension, diabetes, hyperlipidemia, nicotine abuse, and obesity (body mass index >30 kg/m2). Impact of risk factors on ICH at presentation was calculated using univariate and multivariate logistic regression with age and sex adjustment. We performed Kaplan-Meier and Cox regression to analyze cumulative 5-year risk for (re)bleeding. RESULTS: We included 682 patients with CCM. The univariate logistic regression showed a significant relationship (odds ratio=1.938 [95% CI, 1.120-3.353], P=0.018) between obesity and ICH as mode of presentation. Multivariate adjusted logistic regression confirmed significant correlation with odds ratio=1.902 (95% CI, 1.024-3.532, P=0.042). Cox regression did not identify predictors for occurrence of (re)hemorrhage (P>0.05; hazard ratios: arterial hypertension 1.112 [95% CI, 0.622-1.990], diabetes 0.850 [95% CI, 0.208-3.482], hyperlipidemia 0.719 [95% CI, 0.261-1.981], nicotine abuse 1.123 [95% CI, 0.591-2.134], and obesity 0.928 [95% CI, 0.416-2.070]). CONCLUSIONS: This study provides evidence that obesity may be a risk factor for CCM hemorrhage. It was significantly associated with ICH as mode of presentation. Other risk factors (arterial hypertension, diabetes, hyperlipidemia, and current nicotine abuse) showed no such effect. None of the factors showed to be independent predictors for cumulative 5-year risk of (re)bleeding.

DNA promoter methylation of CCM genes in human cerebral cavernous malformations: Importance of confirming MSP data through sequencing.

BACKGROUND: Cerebral cavernous malformations (CCMs) is the second most common cerebrovascular disease and is classified as familial (20%) and sporadic (80%) forms. Loss of function mutation of three CCM genes results in the familial CCM. Considering the similar clinic presentation of familial and sporadic CCMs, and based on enriched CpG islands in the DNA promoter region of three CCM genes, we hypothesized that DNA methylation of the CpG islands of the CCM genes is involved in human CCM, thereby leading to loss of CCM genes. MATERIAL AND METHODS: 69 human CCMs including sporadic (n = 40), multiple (n = 15) and familial (n = 14) cases. DNA was extracted from the surgical specimens of CCMs followed by bisulfite conversion. The methylation status of the promoter regions of three CCM genes was detected by methylation specific PCR (MSP). To confirm the results of MSP, four MSP-positive probes showing CCM3 methylation underwent deep bisulfite sequencing (DBS). RESULTS: MSP mostly excluded methylation of CCM1 and CCM2 promotor regions (data not shown). In the case of CCM3, 12 out of 55 sporadic cases showed positivity for MSP (21.8%). Deep bisulfite sequencing revealed that four CCM3 MSP positive cases were all negative for DNA methylation. CONCLUSION: The present study suggests that DNA promotor methylation of CCM1-3 genes is not involved in human family CCMs and that it is important to confirm MSP data with DBS. Further study with higher number of sporadic CCM patients is required for better understanding whether this epigenetic mechanism is involved in the pathology of CCM.

PDCD10-Deficiency Promotes Malignant Behaviors and Tumor Growth via Triggering EphB4 Kinase Activity in Glioblastoma.

We previously reported an angiogenic and tumor-suppressor-like function of programmed cell death 10 (PDCD10) in glioblastoma (GBM). However, the underlying mechanism remains to be elucidated. We hypothesized that loss of PDCD10 activates GBM cells and tumor progression via EphB4. To this end, PDCD10 was knocked down in U87 and T98g by lentiviral mediated shRNA transduction (shPDCD10). GBM cell phenotype in vitro and tumor growth in a mouse xenograft model were investigated in presence or absence of the treatment with a specific EphB4 kinase inhibitor NVP-BHG712 (NVP). We demonstrated that knockdown of PDCD10 in GBM cells significantly upregulated the mRNA and protein expression of EphB4 accompanied by the activation of Erk1/2. EphB4 kinase activity, reflected by phospho-EphB4, significantly increased in shPDCD10 GBM cells, and in tumors derived from shPDCD10 GBM xenografts, which was abolished by the treatment with NVP. Furthermore, NVP treatment significantly suppressed PDCD10-knockdown mediated aggressive GBM cell phenotype in vitro and extensive tumor cell proliferation, the tumor neo-angiogenesis, and a quick progression of tumor formation in vivo. In summary, loss of PDCD10 activates GBM cells and promotes tumor growth via triggering EphB4. Targeting EphB4 might be an effective strategy particularly for the personalized therapy in GBM patients with PDCD10-deficiency.

Hemorrhage from cerebral cavernous malformations: The role of associated developmental venous anomalies.

OBJECTIVE: To determine the role of associated developmental venous anomalies (DVAs) in intracranial hemorrhage (ICH) caused by cerebral cavernous malformations (CCMs). METHODS: We analyzed patient registry data of 1,219 patients with cavernous malformations treated in our institution between 2003 and 2018. Patients with spinal and familial CCM and patients without complete MRI data were excluded. The impact of various variables on ICH as a mode of presentation was assessed with multivariate binary logistic regression analysis. Kaplan Meier/Cox regression analysis was performed to analyze cumulative 5-year-risk for (re)hemorrhage and to identify baseline predictors of this outcome. RESULTS: Seven hundred thirty-one patients with CCM were included. Multivariate logistic regression confirmed a statistically significant negative correlation with DVA (odds ratio [OR] 0.635 [95% confidence interval (CI) 0.459-0.878]) and positive correlation with brainstem localization (OR 6.277 [95% CI 4.287-9.191]) with ICH as the mode of presentation. Among 731 patients, 76 experienced (re)hemorrhage during 2,338 person-years of follow-up. Overall cumulative 5-year risk was 24.1% (95% CI 21.1%-27.5%). Cox regression analysis revealed initial presentation with ICH (hazard ratio [HR] 8.0 [95% CI 3.549-18.122]) and brainstem localization (HR 2.9 [95% CI 1.756-4.765]) as independent baseline predictors of (re)hemorrhage. Presence of DVA added no independent prognostic information (HR 1.1 [95% CI 0.717-1.885]). CONCLUSION: Patients with CCM with associated DVA are at lower risk to present with ICH. During untreated 5-year follow-up, they showed equal (re)hemorrhage risk compared to patients with CCM without DVA.

Loss of programmed cell death 10 activates tumor cells and leads to temozolomide-resistance in glioblastoma.

PURPOSE: Glioblastoma (GBM) is one of the most aggressive and incurable primary brain tumors. Identification of novel therapeutic targets is an urgent priority. Programmed cell death 10 (PDCD10), a ubiquitously expressed apoptotic protein, has shown a dual function in different types of cancers and in chemo-resistance. Recently, we reported that PDCD10 was downregulated in human GBM. The aim of this study was to explore the function of PDCD10 in GBM cells. METHODS: PDCD10 was knocked down in three GBM cell lines (U87, T98g and LN229) by lentiviral-mediated shRNA transduction. U87 and T98g transduced cells were used for phenotype study and LN229 and T98g cells were used for apoptosis study. The role of PDCD10 in apoptosis and chemo-resistance was investigated after treatment with staurosporine and temozolomide. A GBM xenograft mouse model was used to confirm the function of PDCD10 in vivo. A protein array was performed in PDCD10-knockdown and control GBM cells. RESULTS: Knockdown of PDCD10 in GBM cells promoted cell proliferation, adhesion, migration, invasion, and inhibited apoptosis and caspase-3 activation. PDCD10-knockdown accelerated tumor growth and increased tumor mass by 2.1-fold and led to a chemo-resistance of mice treated with temozolomide. Immunostaining revealed extensive Ki67-positive cells and less activation of caspase-3 in PDCD10-knockdown tumors. The protein array demonstrated an increased release of multiple growth factors from PDCD10-knockdown GBM cells. CONCLUSIONS: Loss of programmed cell death 10 activates tumor cells and leads to temozolomide-resistance in GBM, suggesting PDCD10 as a potential target for GBM therapy.

Aneurysmal intracerebral hematoma: Risk factors and surgical treatment decisions.

OBJECTIVES: Intracerebral hematoma (ICH) complicates the course of aneurysmal subarachnoid hemorrhage (SAH). To date, there are no unique guidelines for management of aneurysmal ICH. The aim of this study was to identify risk factors for and impact of aneurysmal ICH with special attention on treatment decisions derived from ICH volume. PATIENTS AND METHODS: All patients admitted with aneurysmal SAH between 2003 and 2016 were eligible for this study. Various demographic, clinical and radiographic characteristics of patients were correlated with the occurrence and volume of ICH in univariate and multivariate manner. The associations between ICH volume and the need for surgical procedures and functional outcome were also analyzed. RESULTS: 991 patients were included into final analysis. ICH occurred in 301 (30.4%) cases. Location in the middle cerebral artery (MCA, p < 0.001, aOR = 7.04), WFNS grade 4-5 (p < 0.001, aOR = 4.43), rebleeding before therapy (p = 0.004, aOR = 2.45), intracranial pressure over 20 mmHg upon admission (p = 0.008, aOR = 1.60) and intraventricular bleeding (p = 0.008, aOR = 1.62) were independently associated with ICH presence. In turn, WFNS grade 4-5 (p < 0.001) and MCA aneurysms (p < 0.001) were the only independent predictors of ICH volume. According to the receiver operating characteristic curves, the clinically relevant cutoff for additional surgical interventions (decompression/hematoma evacuation) was 17 mL. ICH occurrence and ICH volume ≥17 mL independently predicted poor outcome at 6 months after SAH (defined as modified Rankin Scale>3). CONCLUSION: Of over 30 tested variables, the location of the ruptured aneurysm in the MCA remains the major risk factor for occurrence and volume of ICH. Given the presence of brain swelling and other bleeding components of SAH, surgical intervention on aneurysmal ICH is indicated at lower volume values, than it is generally accepted for spontaneous ICH.

Structure-based drug design identifies polythiophenes as antiprion compounds.

Prions cause transmissible spongiform encephalopathies for which no treatment exists. Prions consist of PrP(Sc), a misfolded and aggregated form of the cellular prion protein (PrP(C)). We explore the antiprion properties of luminescent conjugated polythiophenes (LCPs) that bind and stabilize ordered protein aggregates. By administering a library of structurally diverse LCPs to the brains of prion-infected mice via osmotic minipumps, we found that antiprion activity required a minimum of five thiophene rings bearing regularly spaced carboxyl side groups. Solid-state nuclear magnetic resonance analyses and molecular dynamics simulations revealed that anionic side chains interacted with complementary, regularly spaced cationic amyloid residues of model prions. These findings allowed us to extract structural rules governing the interaction between LCPs and protein aggregates, which we then used to design a new set of LCPs with optimized binding. The new set of LCPs showed robust prophylactic and therapeutic potency in prion-infected mice, with the lead compound extending survival by >80% and showing activity against both mouse and hamster prions as well as efficacy upon intraperitoneal administration into mice. These results demonstrate the feasibility of targeted chemical design of compounds that may be useful for treating diseases of aberrant protein aggregation such as prion disease.

Prion pathogenesis is faithfully reproduced in cerebellar organotypic slice cultures.

Prions cause neurodegeneration in vivo, yet prion-infected cultured cells do not show cytotoxicity. This has hampered mechanistic studies of prion-induced neurodegeneration. Here we report that prion-infected cultured organotypic cerebellar slices (COCS) experienced progressive spongiform neurodegeneration closely reproducing prion disease, with three different prion strains giving rise to three distinct patterns of prion protein deposition. Neurodegeneration did not occur when PrP was genetically removed from neurons, and a comprehensive pharmacological screen indicated that neurodegeneration was abrogated by compounds known to antagonize prion replication. Prion infection of COCS and mice led to enhanced fodrin cleavage, suggesting the involvement of calpains or caspases in pathogenesis. Accordingly, neurotoxicity and fodrin cleavage were prevented by calpain inhibitors but not by caspase inhibitors, whereas prion replication proceeded unimpeded. Hence calpain inhibition can uncouple prion replication from its neurotoxic sequelae. These data validate COCS as a powerful model system that faithfully reproduces most morphological hallmarks of prion infections. The exquisite accessibility of COCS to pharmacological manipulations was instrumental in recognizing the role of calpains in neurotoxicity, and significantly extends the collection of tools necessary for rigorously dissecting prion pathogenesis.