Intratumoral histological and molecular heterogeneity in an adult diffuse glioma

Adult-type diffuse gliomas are the most prevalent type of malignant adult brain tumors. Intratumoral heterogeneity can hinder accurate diagnosis and subsequent treatment. This case report documents a tumor with intratumoral heterogeneity, both histologically and by methylation analysis, located within the left cerebral hemisphere of a 29-year-old female. She presented after a witnessed generalized tonic clonic seizure at home. Two years prior she had a witnessed seizure; however, no brain imaging was done at the time. Magnetic resonance imaging (MRI), on this admission, showed a mass lesion in the left frontal operculum with poorly identified margins and right-sided midline shift. Sampling from the left temporal lobe showed an IDH-mutant, ATRX-mutant astrocytoma, which appeared grade 4 in the enhancing anterior portion and grade 2 in the left temporal lobe. Methylation analysis confirmed this heterogeneity. In summary, this is an excellent example of tumor heterogeneity both histologically and by molecular analysis. It is probable, given the clinical history of presentation 2 years prior, that this tumor originated as a low-grade glioma and subsequently evolved.

Immunoproteasome deficiency results in age-dependent development of epilepsy

The immunoproteasome is a central protease complex required for optimal antigen presentation. Immunoproteasome activity is also associated with facilitating the degradation of misfolded and oxidized proteins, which prevents cellular stress. While extensively studied during diseases with increasing evidence suggesting a role for the immunoproteasome during pathological conditions including neurodegenerative diseases, this enzyme complex is believed to be mainly not expressed in the healthy brain. In this study, we show an age-dependent increase in polyubiquitination in the brains of wild-type mice, accompanied by an induction of immunoproteasomes, which was most prominent in neurons and microglia. In contrast, mice completely lacking immunoproteasomes (triple-knockout mice), displayed a strong increase in polyubiquitinated proteins already in the young brain and developed spontaneous epileptic seizures, beginning at the age of 6 months. Injections of kainic acid led to high epilepsy-related mortality of aged triple-knockout mice, confirming increased pathological hyperexcitability states. Notably, the expression of the immunoproteasome was reduced in the brains of patients suffering from epilepsy. In addition, the aged triple-knockout mice showed increased anxiety, tau hyperphosphorylation and degeneration of Purkinje cell population with the resulting ataxic symptoms and locomotion alterations. Collectively, our study suggests a critical role for the immunoproteasome in the maintenance of a healthy brain during ageing.

CPEB4-CLOCK crosstalk during temporal lobe epilepsy

OBJECTIVE

Posttranscriptional mechanisms are increasingly recognized as important contributors to the formation of hyperexcitable networks in epilepsy. Messenger RNA (mRNA) polyadenylation is a key regulatory mechanism governing protein expression by enhancing mRNA stability and translation. Previous studies have shown large-scale changes in mRNA polyadenylation in the hippocampus of mice during epilepsy development. The cytoplasmic polyadenylation element-binding protein CPEB4 was found to drive epilepsy-induced poly(A) tail changes, and mice lacking CPEB4 develop a more severe seizure and epilepsy phenotype. The mechanisms controlling CPEB4 function and the downstream pathways that influence the recurrence of spontaneous seizures in epilepsy remain poorly understood.

METHODS

Status epilepticus was induced in wild-type and CPEB4-deficient male mice via an intra-amygdala microinjection of kainic acid. CLOCK binding to the CPEB4 promoter was analyzed via chromatin immunoprecipitation assay and melatonin levels via high-performance liquid chromatography in plasma.

RESULTS

Here, we show increased binding of CLOCK to recognition sites in the CPEB4 promoter region during status epilepticus in mice and increased Cpeb4 mRNA levels in N2A cells overexpressing CLOCK. Bioinformatic analysis of CPEB4-dependent genes undergoing changes in their poly(A) tail during epilepsy found that genes involved in the regulation of circadian rhythms are particularly enriched. Clock transcripts displayed a longer poly(A) tail length in the hippocampus of mice post-status epilepticus and during epilepsy. Moreover, CLOCK expression was increased in the hippocampus in mice post-status epilepticus and during epilepsy, and in resected hippocampus and cortex of patients with drug-resistant temporal lobe epilepsy. Furthermore, CPEB4 is required for CLOCK expression after status epilepticus, with lower levels in CPEB4-deficient compared to wild-type mice. Last, CPEB4-deficient mice showed altered circadian function, including altered melatonin blood levels and altered clustering of spontaneous seizures during the day.

SIGNIFICANCE

Our results reveal a new positive transcriptional-translational feedback loop involving CPEB4 and CLOCK, which may contribute to the regulation of the sleep-wake cycle during epilepsy.

Case report: BRAF-inhibitor therapy in BRAF-mutated primary CNS tumours including one case of BRAF-mutated Rosai-Dorfman disease

BRAF V600E oncogene mutations have been reported in multiple central nervous system (CNS) tumor types, and emerging evidence supports the use of targeted therapy in BRAF-mutated gliomas. BRAF oncogene mutations have been recently identified in Rosai-Dorfman disease (RDD)-a rare non-Langerhans cell histiocytosis. This series describes three patients from two neurosurgical centers in Ireland with BRAF V600E-mutated CNS tumors. The study participants include a 19-year-old male patient with ganglioglioma with anaplastic features, a 21-year-old male patient with CNS involvement of RDD, and a 28-year-old female patient with ganglioglioma with anaplastic features. Two patients received radiation with concurrent temozolomide before BRAF-targeted therapy. This case series describes clinical and radiological responses to BRAF-targeted therapy in BRAF V600E-mutated gliomas across multiple tumor grades and is only the second published report of response to targeted therapy in BRAF-mutated RDD. The durability of disease control with BRAF-targeted therapy was generally superior to that achieved with chemoradiation; one patient has experienced ongoing disease control for 5 years. The reported case of treatment response in BRAF-mutated RDD supports the strategy of genotyping and utilization of targeted therapy in this rare disease. The optimal sequencing of BRAF-targeted therapy in BRAF-mutated gliomas/glioneuronal tumors remains unclear, and further prospective studies are required to guide the use of genome-matched therapy in this patient population.

MicroRNA inhibition using antimiRs in acute human brain tissue sections

Antisense inhibition of microRNAs is an emerging preclinical approach to pharmacoresistant epilepsy. A leading candidate is an 'antimiR' targeting microRNA-134 (miR-134), but testing to date has used rodent models. Here, we develop an antimiR testing platform in human brain tissue sections. Brain specimens were obtained from patients undergoing resective surgery to treat pharmacoresistant epilepsy. Neocortical specimens were submerged in modified artificial cerebrospinal fluid (ACSF), dissected for clinical neuropathological examination, and unused material transferred for sectioning. Individual sections were incubated in oxygenated ACSF, containing either antimiR-134 or a non-targeting control antimiR, for 24 hours at room temperature. RNA integrity was assessed using BioAnalyzer processing, and individual miRNA levels measured using RT-qPCR. Specimens transported in ACSF could be used for neuropathological diagnosis and had good RNA integrity. AntimiR-134 mediated a dose-dependent knockdown of miR-134, with approximately 75% reduction of miR-134 at 1 µM and 90% reduction at 3 µM. These doses did not have off-target effects on expression of a selection of three other miRNAs. This is the first demonstration of antimiR-134 effects in live human brain tissues. The findings lend further support to the preclinical development of a therapy that targets miR-134 and offer a flexible platform for the pre-clinical testing of antimiRs, and other antisense oligonucleotide therapeutics, in human brain.

O50: DEVELOPMENT OF A PATIENT-DERIVED TUMOUR ORGANOIDS FROM METASTATIC BREAST CANCER FOR ASSESSMENT OF NOVEL CLINICALLY ACTIONABLE TARGETS

Introduction

Metastatic breast cancer (MBC) is the main source of mortality in breast cancer patients largely due to lack of effective treatments. Our previous results suggest that tumour transcriptional heterogeneity drives therapy resistance and cancer relapse. While traditional in vitro human cancer cell line models have been widely used for disease modelling, they do not faithfully recapitulate the pathophysiology of MBC.

Method

In this study we developed patient-derived tumour organoid cultures from frozen patient-derived (PDX) models of MBC. Using those models we performed preclinical drug screening of investigational and FDA approved therapeutics previously uncovered by us as potentially clinically actionable in MBC.

Result

Our results reveal high heterogeneity in the responses to various targeted therapies among tested MBC organoids, which makes them a valuable tool for studying intra-tumor heterogeneity and drug response. Moreover, drug screening identified a divergent set of the breast to brain metastatic MBC organoids that showed high sensitivity to a new class of tyrosine kinase receptors, RET.

Conclusion

Taken together, our novel MBC models and methodology applied here provides an important modelling tool to assess the contribution of intra-tumour heterogeneity and microenvironment to drug response as they recapitulate the cellular, structural and biochemical complexity previously observed in our genomic characterisation of MBCs. Application of this type of translational research will enhance the development of new targeted precision medicine strategies and prelude stratification for clinical trials. Abbreviations MBC- Metastatic Breast Cancer; PDX- Patient-Derived Xenografts; FDA- Food and Drug Administration; RET- Receptor Tyrosine Kinase

Take-home message

Patient-derived tumour organoid cultures provide an important modelling tool to assess the contribution of intra-tumour heterogeneity and microenvironment to drug response as they recapitulate the cellular, structural and biochemical complexity previously observed in genomic characterisation of metastatic breast cancer.

SURGICAL EDUCATION AND TRAINING

Melanoma brain metastases in Ireland: surgical and systemic considerations

BACKGROUND

Cerebral metastases is a common complication in patients with melanoma. There is a paucity of information in the Republic of Ireland regarding the factors associated with melanoma brain metastases (MBM).

METHODS

Patients diagnosed with melanoma brain metastases in Ireland were retrospectively identified in Beaumont Hospital between 1999 and 2018. Patient demographics; age at diagnosis of primary melanoma, age at detection of MBM, year of detection of MBM, anatomical location of primary melanoma, BRAF mutation analysis and the number of metastases were investigated. Follow-up data were also derived, including overall survival.

RESULTS

There has being a 158% increase in the incidence of primary melanoma from 1999 compared to 2016. Over the same time period 128 patients with melanoma brain metastases were diagnosed. There was a significant male predominance (n = 77/128; 60%; p < 0.0001). BRAF mutation and leptomeningeal disease were independent prognostic factors in our cohort with a median survival 8 months and 0.5 months, respectively.

CONCLUSIONS

Male predominance, leptomeningeal disease and BRAF mutation represent important considerations in this population group. The results of this study add to our knowledge concerning outcomes in melanoma brain metastases and may be useful in clinical planning and future treatments.

Comparative analysis of the AIB1 interactome in breast cancer reveals MTA2 as a repressive partner which silences E-Cadherin to promote EMT and associates with a pro-metastatic phenotype

Steroid regulated cancer cells use nuclear receptors and associated regulatory proteins to orchestrate transcriptional networks to drive disease progression. In primary breast cancer, the coactivator AIB1 promotes estrogen receptor (ER) transcriptional activity to enhance cell proliferation. The function of the coactivator in ER+ metastasis however is not established. Here we describe AIB1 as a survival factor, regulator of pro-metastatic transcriptional pathways and a promising actionable target. Genomic alterations and functional expression of AIB1 associated with reduced disease-free survival in patients and enhanced metastatic capacity in novel CDX and PDX ex-vivo models of ER+ metastatic disease. Comparative analysis of the AIB1 interactome with complementary RNAseq characterized AIB1 as a transcriptional repressor. Specifically, we report that AIB1 interacts with MTA2 to form a repressive complex, inhibiting CDH1 (encoding E-cadherin) to promote EMT and drive progression. We further report that pharmacological and genetic inhibition of AIB1 demonstrates significant anti-proliferative activity in patient-derived models establishing AIB1 as a viable strategy to target endocrine resistant metastasis. This work defines a novel role for AIB1 in the regulation of EMT through transcriptional repression in advanced cancer cells with a considerable implication for prognosis and therapeutic interventions.

Desmoplastic myxoid tumor, SMARCB1-mutant: clinical, histopathological and molecular characterization of a pineal region tumor encountered in adolescents and adults

Atypical teratoid/rhabdoid tumor (ATRT) is a highly malignant brain tumor predominantly occurring in infants. Mutations of the SMARCB1 gene are the characteristic genetic lesion. SMARCB1-mutant tumors in adolescents and adults are rare and may show uncommon histopathological and clinical features. Here we report seven SMARCB1-deficient intracranial tumors sharing distinct clinical, histopathological and molecular features. Median age of the four females and three males was 40 years (range 15-61 years). All tumors were located in the pineal region. Histopathologically, these tumors displayed spindled and epithelioid cells embedded in a desmoplastic stroma alternating with a variable extent of a loose myxoid matrix. All cases showed loss of nuclear SMARCB1/INI1 protein expression, expression of EMA and CD34 was frequent and the Ki67/MIB1 proliferation index was low in the majority of cases (median 3%). Three cases displayed heterozygous SMARCB1 deletions and two cases a homozygous SMARCB1 deletion. On sequencing, one tumor showed a 2 bp deletion in exon 4 (c.369_370del) and one a short duplication in exon 3 (c.237_276dup) both resulting in frameshift mutations. Most DNA methylation profiles were not classifiable using the Heidelberg Brain Tumor Classifier (version v11b4). By unsupervised t-SNE analysis and hierarchical clustering analysis, however, all tumors grouped closely together and showed similarities with ATRT-MYC. After a median observation period of 48 months, three patients were alive with stable disease, whereas one patient experienced tumor progression and three patients had succumbed to disease. In conclusion, our series represents an entity with distinct clinical, histopathological and molecular features showing epigenetic similarities with ATRT-MYC. We propose the designation desmoplastic myxoid tumor (DMT), SMARCB1-mutant, for these tumors.

Acute multiple sclerosis lesion pathology does not predict subsequent clinical course-a biopsy study

BACKGROUND

Knowledge of the clinical outcome in tumefactive demyelination remains limited.

AIMS

This study aims to characterise the natural history of biopsy-proven, pathogen-free, cerebral demyelination in an adult Irish population.

METHODS

We identified all patients with biopsy-proven demyelination in a single neuropathology centre between 1999 and 2017. A baseline, and at least one follow-up MRI scan was available in each instance (mean of 3 scans per patient), together with both the presenting and most recent clinical details including disability level and disease-modifying drugs.

RESULTS

In 21 patients, white matter biopsies showed the following: macrophages with myelin debris, myelin-axonal dissociation, reactive astrocytes and occasional lymphocytes. During a mean follow-up time of 8 years (± 4.4), 17 patients developed MS, confirmed both clinically and on MRI, using the 2010 McDonald criteria: 11 relapsing remitting (RR) MS, four secondary progressive and two primary progressive MS. Four patients had a monophasic illness with lesion regression, without clinical or radiological evidence of any further disease activity on follow-up. The patients with progressive MS had significantly higher levels of physical disability than either the RRMS or monophasic patients.

CONCLUSION

Uniform white matter subacute demyelination is associated with a diverse clinical course ranging from a monophasic illness to progressive MS, suggesting that extraneous factors distinct from the basic pathology significantly influence the clinical course in MS.

Evaluation of the specificity of the central diagnostic criterion for chronic traumatic encephalopathy

INTRODUCTION

Chronic traumatic encephalopathy (CTE) is a postmortem diagnosis. Consensus postmortem, but not antemortem, diagnostic criteria have been established. A key factor in these criteria is evidence of phosphorylated-tau (p-tau) around sulcal vessels in the cortex. However, this sign has been observed anecdotally in a diverse range of neurodegenerative diseases (NDD). We therefore hypothesise that this criterion may lack specificity.

METHODS

To test this, we assessed patients with NDD, but no documented history of brain trauma, for sulcal p-tau. Tissue was retrieved from Dublin Brain Bank (known NDD n = 17; control with no diagnosed NDD n = 6; CTE n = 1), and slides were prepared from three sites with a predilection for trauma: superior frontal gyrus, temporal pole, and superior temporal gyrus. We stained the resulting anonymised slides with both hemotoxylin and eosin (H&E) and p-tau. Three neuropathologists, blinded to the clinical history and neuropathological diagnosis in each instance, evaluated each case for sulcal p-tau. We calculated the interrater agreement, using Fleiss's kappa, and the specificity of this neuropathological sign.

RESULTS

Sulcal p-tau was highly specific to diagnosed CTE cases (specificity 0.98), with moderate interrater agreement (κ = 0.45).

CONCLUSION

In conclusion, therefore, we observed sulcal p-tau to be a sign highly specific to CTE when compared with NDD cases in the absence of head trauma.

Neuropathology correlates of cognitive assessments

BACKGROUND

Alzheimer's disease and other dementias are the fourth largest contributors to neurological disability and the second largest contributor to deaths from neurological disease. Described in the 1980s as 'the silent epidemic' these disorders principally, though not exclusively, affect persons 80 years or older, and in developed countries, this 'old old' population continues to grow. Definitive diagnosis of the underlying cause of the neurodegenerative disease relies on neuropathological evaluation.` AIMS: Herein, we review the sampling methods, analysis and interpretation of both pathological and immunocytochemical techniques in the diagnostic assessment of neurodegenerative disease.

FINDINGS

Neurodegenerative disorders are characterised by accumulation of pathologically altered protein in the human brain, and in some cases, in the peripheral tissues. Whilst it is suggested that a comprehensive review of the patient's clinical history, cognition and behaviour, together with a full clinical examination and radiological analysis, should lead to a high degree of confidence in the clinical diagnosis, the view persists that underlying pathology can only be predicted on clinical grounds especially in Alzheimer's disease, vascular brain injury and diffuse Lewy body disease with only limited accuracy.

CONCLUSIONS

Neuropathological assessment of well characterised clinical cases provides accurate data on the prevalence of neurodegenerative diseases. This will aid future biomarker, neuroimaging studies and clinical trials focussed on population based cohorts.

IgG4 hypophysitis - a rare and underdiagnosed cause of pituitary gland and stalk mass-like thickening

Our aim is to present a typical case of IgG4-related hypophysitis, which will offer insight into the aetiology and pathogenesis of this relatively newly described disease. IgG4 Related Disease is a protean systemic condition that mimics inflammatory, infectious, and malignant processes. Biopsy of affected organs will show a typical histopathological pattern.

Temporal stability of MGMT promoter methylation in glioblastoma patients undergoing STUPP protocol

Epigenetic silencing of O-6-methylguanine-DNA methyltransferase (MGMT) promoter via methylation in a glioblastoma (GBM), has been correlated with a more favourable response to alkylating chemotherapeutic agents such as temozolomide. The use of global methylation surrogates such as Long Interspersed Nucleotide Element 1 (LINE1) may also be valuable in order to fully understand these highly heterogeneous tumours. In this study, we analysed both original and recurrent GBMs in 22 patients (i.e. 44 tumours), for both MGMT and LINE1 methylation status. In the 22 patients: 14 (63.6%) displayed MGMT methylation stability in the recurrent GBM versus 8 (36.4%), with instability of methylation status. No significant differences in overall and progression free survival was evident between these two groups. LINE1 methylation status remained stable for 12 (54.5%) of recurrent GBM patients versus 9 (41%) of the patients with instability in LINE1 methylation status (p = 0.02), resulting in an increase in overall survival of the stable LINE1 group (p = 0.04). The results obtained demonstrated major epigenetic instability of GBMs treated with temozolomide as part of the STUPP protocol. GBMs appear to undergo selective evolution post-treatment, and have the ability to recur with a newly reprogrammed epigenetic status. Selective targeting of the altered epigenomes in recurrent GBMs may facilitate the future development of both prognostic biomarkers and enhanced therapeutic strategies.

EBV driven natural killer cell disease of the central nervous system presenting as subacute cognitive decline

Brain biopsy in patients presenting with subacute encephalopathyis never straightforward and only undertaken when a ‘treatable condition’ is a realistic possibility.

This 63 year old right handed, immunocompetent Caucasian woman presented with an 8 month history of rapidly progressive right-sided hearing impairment, a 4 month history of intermittent headaches, tinnitus, ‘dizziness’, dysphagia, nausea and vomiting, with the subsequent evolution of progressive gait ataxia and a subacute global encephalopathy. The possibility of CJD was raised. Brain biopsy was carried out. Western blot for prion protein was negative. She died 9 days later and autopsy brain examination confirmed widespread subacute infarction due to an EBV positive atypical NK/T-cell infiltrate with positivity for CD3, CD56, granzyme B, perforin and EBER with absence of CD4, CD5 and CD8 expression. Molecular studies for T-cell clonality were attempted but failed due to insufficient DNA quality. Serology was consistent with past EBV infection (EBV VCA and EBNA IgG Positive). There was no evidence of disease outside the CNS. Primary central nervous system NK/T-cell lymphoma is extremely rare. The rare reported cases all present with a discrete intracranial mass, unlike the diffuse infiltrative pattern in this case. Whilst the diffuse interstitial pattern is reminiscent of chronic active EBV infection (CAEBV) seen in other organ systems such as the liver and bone marrow, the clinical presentation and epidemiologic profile are not typical for CAEBV.

Brain biopsies requiring Creutzfeldt-Jakob disease precautions in the Republic of Ireland 2005-2016

AIMS

Creutzfeldt-Jakob disease (CJD) risk precautions are required when performing brain biopsies on patients with a dementing illness and in 'risk' groups. The impact on a diagnostic neuropathology service is considerable. We sought to determine if better case selection might reduce the necessity for application of CJD risk precautions.

METHODS

We reviewed the clinical information, contributory investigations and final neuropathologic diagnosis in a cohort of patients (n = 21), referred to the National CJD Surveillance Centre between January 1, 2005, and December 31, 2016.

RESULTS

Of this 21-patient cohort, five were positive for CJD, four belonged to the 'at risk of CJD' category requiring brain surgery, while the remaining 12 were referred to the National CJD Surveillance Unit with CJD as part of their differential diagnosis. CJD was confirmed in 5/21 (three sporadic [s]CJD, one variant [v]CJD and one iatrogenic [i] CJD). CJD was clinically probable in 4/5 proven CJD patients (80%). The patients (n = 4) in the 'at risk of CJD' group were diagnosed with tumour (n = 2), inflammation (n = 1) and non-specific changes (n = 1). Of the remaining 12 patients (in whom CJD was included in the differential diagnosis), the final neuropathologic diagnoses included tumour (n = 2), neurodegenerative (n = 2), inflammatory (n = 1), metabolic (n = 2), vascular (n = 2) and non-specific gliosis (n = 3).

CONCLUSIONS

More often than not, the clinical suspicion of CJD was not borne out by the final neuropathological diagnosis. Failure by clinicians to adhere to the recommended CJD investigation algorithm impacts adversely on the neuropathology workload and causes unnecessary concern among operating theatre, laboratory and nursing personnel.

Intravascular large B-cell lymphoma presenting clinically as rapidly progressive dementia

BACKGROUND

In patients presenting with rapidly progressive dementia, prion disease may enter the differential diagnosis. The commonest malignancies masquerading as prion disease are primary CNS lymphoma and intravascular large B-cell lymphoma, both rare and difficult to diagnose without brain biopsy.

CASE PRESENTATION

This 82-year-old lady with a past history of hypertension, presented with rapidly progressive cognitive impairment and ataxia. The possibility of sCJD was raised. Brain biopsy was carried out. Western blot for prion protein was negative. Brain biopsy showed intravascular large B-cell lymphoma. She died shortly afterwards.

CONCLUSION

The clinical presentation of intravascular large B-cell lymphoma is diverse. Patients may present as in this case with dementia, seizures, and myoclonus leading to a clinical diagnosis of sCJD. The diagnosis here was made at biopsy but is made at autopsy in over 50% of cases.

Autoregulated paracellular clearance of amyloid-β across the blood-brain barrier

The blood-brain barrier (BBB) is essential for maintaining brain homeostasis and protecting neural tissue from damaging blood-borne agents. The barrier is characterized by endothelial tight junctions that limit passive paracellular diffusion of polar solutes and macromolecules from blood to brain. Decreased brain clearance of the neurotoxic amyloid-β (Aβ) peptide is a central event in the pathogenesis of Alzheimer's disease (AD). Whereas transport of Aβ across the BBB can occur via transcellular endothelial receptors, the paracellular movement of Aβ has not been described. We show that soluble human Aβ(1-40) monomers can diffuse across the paracellular pathway of the BBB in tandem with a decrease in the tight junction proteins claudin-5 and occludin in the cerebral vascular endothelium. In a murine model of AD (Tg2576), plasma Aβ(1-40) levels were significantly increased, brain Aβ(1-40) levels were decreased, and cognitive function was enhanced when both claudin-5 and occludin were suppressed. Furthermore, Aβ can cause a transient down-regulation of claudin-5 and occludin, allowing for its own paracellular clearance across the BBB. Our results show, for the first time, the involvement of the paracellular pathway in autoregulated Aβ movement across the BBB and identify both claudin-5 and occludin as potential therapeutic targets for AD. These findings also indicate that controlled modulation of tight junction components at the BBB can enhance the clearance of Aβ from the brain.

Parkin disease: a clinicopathologic entity?

IMPORTANCE

Mutations in the gene encoding parkin (PARK2) are the most common cause of autosomal recessive juvenile-onset and young-onset parkinsonism. The few available detailed neuropathologic reports suggest that homozygous and compound heterozygous parkin mutations are characterized by severe substantia nigra pars compacta neuronal loss.

OBJECTIVE

To investigate whether parkin-linked parkinsonism is a different clinicopathologic entity to Parkinson disease (PD).

DESIGN, SETTING, AND PARTICIPANTS

We describe the clinical, genetic, and neuropathologic findings of 5 unrelated cases of parkin disease and compare them with 5 pathologically confirmed PD cases and 4 control subjects. The PD control cases and normal control subjects were matched first for age at death then disease duration (PD only) for comparison.

RESULTS

Presenting signs in the parkin disease cases were hand or leg tremor often combined with dystonia. Mean age at onset was 34 years; all cases were compound heterozygous for mutations of parkin. Freezing of gait, postural deformity, and motor fluctuations were common late features. No patients had any evidence of cognitive impairment or dementia. Neuronal counts in the substantia nigra pars compacta revealed that neuronal loss in the parkin cases was as severe as that seen in PD, but relative preservation of the dorsal tier was seen in comparison with PD (P = .04). Mild neuronal loss was identified in the locus coeruleus and dorsal motor nucleus of the vagus, but not in the nucleus basalis of Meynert, raphe nucleus, or other brain regions. Sparse Lewy bodies were identified in 2 cases (brainstem and cortex).

CONCLUSIONS AND RELEVANCE

These findings support the notion that parkin disease is characterized by a more restricted morphologic abnormality than is found in PD, with predominantly ventral nigral degeneration and absent or rare Lewy bodies.

A progressive multifocal neurological syndrome in a 42-year-old woman

This is the case of a 42-year-old female who presented with transient dizziness. Her symptoms and signs progressed to include dysarthria, ataxia and cognitive decline over 2 years, such that she was unable to care for herself. She died 4 years after first presentation without a diagnosis. Investigations revealed a normochromic normocytic anaemia. Cerebrospinal fluid was normal. Serial computed tomography brain showed a wedge-shaped frontal infarct but no progressive changes. Examination at autopsy showed discoloration of the gray and white matter of the brain and spinal cord.Microscopy of leptomeningeal and parenchymal vessels showed they were filled with atypical B lymphocytes confined to the intravascular space with multiple infarcts in the brain, cerebellum and spinal cord. A diagnosis of intravascular B cell lymphoma was made and is discussed.

The contribution of alcohol to fatal traumatic head injuries in the forensic setting

Excessive drinking increases the risk of dying unnaturally. In the Republic of Ireland such deaths are referred to the State Pathologist. Blood alcohol concentration (BAC) is routinely measured. We created a database of cases presenting to the State Pathologist over a nine year period (2000-2008 inclusive) to evaluate the relationship between alcohol and fatal traumatic brain injuries (FTBI). Of a total of 1778 cases, 332 (275 Male [M]; 57 Female [F]) died of head injuries. Fatalities were highest in males aged 36-50 (N = 97) and 26-35 (N = 73). Assaults (N = 147), falls (N = 95), road traffic accidents (RTA) (N = 50) and suicide (N = 15) were the commonest modes of presentation. A positive blood alcohol concentration (BAC) was found in 36% of assaults, 41% of falls and 40% of suicides. In the RTA group BAC was positive in 59% of pedestrians, 33% of drivers and 14% of passengers. Alcohol clearly plays a significant role in FTBI in the forensic setting.

20 year old lady with a paraspinal mass

A 20 year old female presented with a 4 month history of right upper limb pain and paraesthesias. She had no systemic symptoms and no prior medical or family history of note. MRI revealed a right-sided intradural extramedullary mass extending from C7-T1 and displacing the spinal cord. While awaiting surgery her symptoms progressed to involve the right lower limb. She was re-imaged and the lesion now extended from C5 to T3 with spinal cord compression at C7-T1. The radiological features and recent rapid growth were felt to be in keeping with a large plexiform neurofibroma. The patient underwent emergency resection of the lesion and pathology revealed Hodgkin's Lymphoma (HL)-mixed cellularity type. A mediastinal mass was identified on further imaging and biopsy confirmed the diagnosis of HL-stage IV. The patient is currently undergoing treatment with ABVD chemotherapy. CNS-HL is extremely rare and may occur de novo or in association with systemic disease. Lesions may be parenchymal or dural based and are usually intracranial with an increased risk of CNS involvement in HL-mixed-cellularity type as in our patient. This is the first report in the literature of CNS-HL radiologically mimicking a paraspinal plexiform neurofibroma.

Is the contribution of alcohol to fatal traumatic brain injuries being underestimated in the acute hospital setting?

Alcohol consumption in Ireland has nearly doubled during the period 1989-2001. To evaluate the relationship of alcohol to fatal head injuries in the acute hospital setting we created a data base of all fatal traumatic brain injuries in the Department of Neuropathology at Beaumont Hospital over a ten year period (1997-2006 inclusive). 498 cases were identified (351 males: 147 females). Fatalities were highest in males aged 19-25 years (N=101) and 51-70 years (N=109). Falls (N=210) and road traffic accidents (N=183) were the commonest modes of presentation. 36/210 (17%) falls had positive blood alcohol testing, 9/210 (4.3%) had documentation of alcohol in notes but no testing, 35/210 (16.7%) tested negative for alcohol and 130/210 (61.9%) were not tested. The RTA group (N=183) comprised drivers (n=79), passengers (n=47) and pedestrians (n=57). 65/79 (82.2%) of drivers were males aged 19-25 years. Blood alcohol was only available in 27/79 (34.1%) drivers and was positive in 13/27 (48.1%). 14/75 (18.7%) pedestrians were tested for alcohol, 4/14 (28.6%) were positive. Overall 142/183 (77.6%) of the RTA group were not tested. The contribution of alcohol to fatal traumatic brain injuries is probably being underestimated due to omission of blood alcohol concentration testing on admission to hospital. Absence of national guidelines on blood alcohol testing in the emergency department compounds the problem.

Facial nerve schwannoma of the internal auditory canal

BACKGROUND

Facial nerve schwannoma of the internal auditory canal is a very rare tumour.

AIM

While Bell's palsy is the commonest cause of a facial paresis, more serious causes should be excluded if recovery is delayed.

METHOD

A case report of a young man who presented with a long standing facial palsy.

CONCLUSION

Any facial palsy that does not show evidence of recovery within six weeks should be investigated radiologically to exclude a tumour.

Response of glia, mast cells and the blood brain barrier, in transgenic mice expressing interleukin-3 in astrocytes, an experimental model for CNS demyelination

Transgenic mice overexpressing cytokines facilitate analysis of the effects of these immunomodulators on indigenous cells of the central nervous system. This study examines morphological aspects of demyelination and permeability changes, in a recently described transgenic model (termed GFAP-IL3). GFAP-IL3 mice develop progressive motor disease at approximately 5 months. Lesions identified after disease onset, showed activation of microglia, astroglial proliferation with phagocytosis of lipids, and immigration of macrophages and mast cells into neural parenchyma. Lymphocytes failed to appear until the later stages of the disease. Later, cerebellar and brain stem white matter contained focal demyelinating lesions with intense macrophage infiltration and a proliferative astrocytosis. Dystrophic axonal changes were noted, in addition to demyelination in heavily infiltrated lesions. Mast cells, variably present in the thalamus and meninges of wild type mice, were greatly increased at these sites in GFAP-IL3 mice. Blood-brain barrier (BBB) defects were documented with leakage of intravenously injected horseradish peroxidase. Mast cell infiltration into the CNS and their degranulation at the site of injury, may represent initial events in a spontaneous process of macrophage mediated demyelination in which glial cells and macrophages are both involved in the phagocytic process.

July 2004: 40-year-old man with headaches and dyspnea

A 40-year-old man had a 6-week history of severe frontal headaches and dry cough. Chest x-ray showed hilar adenopathy with bilateral parenchymal infiltrates. A diagnosis of atypical pneumonia was made. Four weeks later he was admitted with persistent headache. Infectious screen was negative. Brain MR post contrast, revealed cerebellar enhancement and swelling with moderate tonsillar herniation; findings which precluded the performance of a lumbar puncture. High resolution CT thorax confirmed hilar abnormalities; shown by microscopy to represent non caseating granulomata. A presumptive diagnosis of sarcoidosis was reached. Despite an initial symptomatic improvement his headache persisted. Repeat MRI, eleven days after admission, showed reduced cerebellar enhancement and swelling with no change in the degree of tonsillar herniation. He deteriorated acutely and died two weeks after admission. Autopsy revealed cerebral oedema with tonsillar herniation secondary to cryptococcal meningitis variety neoformans. There was no evidence of neurosarcoid. Active and inactive sarcoid was identified in the lungs and hilar nodes with no evidence of systemic sarcoid. Focal evidence of cryptococcal pneumonitis was present in the lung as a necrotic focus. A strong index of clinical suspicion is necessary to diagnose the rare association of cryptococcus complicating sarcoidosis.

Does ageing have an effect on midbrain premotor nuclei for vertical eye movements?

Currently, there is debate in the clinical literature as to whether defects in vertical gaze are a consequence of normal ageing or a component of an underlying neurodegenerative disorder. Although pathological changes have been demonstrated in diseased subjects, no study to date has addressed the question of normal ageing effects. In this retrospective study, we examined 23 neurologically and pathologically normal subjects (age 18-91). Using an unbiased, frame-based sampling method, we quantified neuronal and glial cell densities in 10 young (<50) and 13 aged (>65) subjects in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), the key premotor substrate in the vertical gaze pathway. We found no statistically significant difference in neuronal density, glial cell density, or neuron-to-glial cell ratios between the young and the aged. We conclude, therefore, that neuronal loss, neuronal atrophy, or gliosis in the riMLF are not consequences of normal ageing.

"True" sporadic ALS associated with a novel SOD-1 mutation

Mutations in the Cu/Zn superoxide dismutase gene (SOD-1) are reported in 20% of familial amyotrophic lateral sclerosis (ALS) cases, but no definite report of a mutation in a "truly" sporadic case of ALS has been proved. We present the first case of a novel SOD-1 mutation in a patient with genetically proven sporadic ALS. This mutation (H80A) is believed to alter zinc ligand binding, and its functional significance correlates well with the aggressive clinical course and postmortem findings observed in this patient.

Atypical ganglion cell tumor of the sciatic nerve

CONTEXT

Although herniation of a lumbosacral intervertebral disk is a major cause of sciatic distribution pain, relentlessly progressive symptoms or signs should alert one to the possibility of a tumor involving the nerve.

OBJECTIVE

To describe the clinical, neurophysiological, and histological features of a pathologically unique tumor involving the sciatic nerve.

SETTING

Tertiary referral university hospital.

PATIENT

A 36-year-old woman was seen with a 6-year history of increasingly severe symptoms in the distribution of the left sciatic nerve.

RESULTS

Electromyography indicated a sciatic nerve lesion in the region of the greater sciatic notch. Magnetic resonance imaging demonstrated a tumor involving the left sciatic nerve in this area. Light microscopy, electron microscopy, and immunohistochemistry results confirmed the presence of an atypical ganglion cell tumor of the sciatic nerve that exhibited prognostically conflicting clinical and histological features.

CONCLUSIONS

To our knowledge, this is the first report of an atypical ganglion cell tumor affecting the sciatic nerve, and illustrates the value of detailed neurophysiological examination in localizing the site of peripheral nerve injury to facilitate focused neuroimaging when standard investigations are uninformative. Longer follow-up is required to determine the true biologic potential of this lesion.

Familial diffuse Lewy body disease, eye movement abnormalities, and distribution of pathology

BACKGROUND

Familial diffuse Lewy body disease (DLBD) is rare and not yet associated with a defect in the synuclein gene. In the differential diagnosis of the parkinsonian syndromes, defects in vertical gaze tend to be identified with progressive supranuclear palsy. False-positive diagnosis of progressive supranuclear palsy can occur, and defects in vertical gaze have been reported in DLBD, although so far a pure vertical gaze palsy associated with pathological abnormalities in the substrate for vertical gaze has not been described.

OBJECTIVES

To report the clinical and pathological findings in 2 siblings with DLBD, and to relate the distribution of the pathological abnormalities in the brainstem to centers for vertical gaze.

MATERIALS

For several years, 2 Irish siblings experienced a progressive parkinsonism-dementia complex associated in one with a defect in vertical gaze and in both with visual hallucinations.

RESULTS

In both patients, results of pathological examination revealed (1) Lewy bodies positive for ubiquitin and alpha-synuclein together with cell loss and gliosis in the substantia nigra, locus ceruleus, and neocortex; and (2) similar findings in the rostral interstitial nucleus of the medial longitudinal fasciculus, the posterior commissure, and the interstitial nucleus of Cajal (substrates for vertical gaze).

CONCLUSIONS

Familial DLBD (not shown to be genetically as distinct from environmentally transmitted) has been shown to exist in an Irish family. Caution should be enjoined in the interpretation of defects in vertical gaze in the differential diagnosis of the parkinsonian syndromes.

Herpes simplex encephalitis occurring after chemotherapy, surgery, and stereotactic radiotherapy for medulloblastoma

Reactivation of latent herpes simplex virus (HSV) in the trigeminal ganglion most commonly gives rise to recurrent herpes labialis and rarely to herpes simplex encephalitis. The mechanisms underlying reactivation of latent trigeminal HSV are complex. Here we report the case history of a 25-year-old woman who developed a fatal, bilateral necrotizing destructive temporal lobe lesion following surgical removal of a cerebellar medulloblastoma and combined radiotherapy and chemotherapy for recurrent tumor. Neuropathologic examination of the brain revealed minimal inflammatory changes, but immunohistochemistry was positive for HSV protein, and HSV deoxyribonucleic acid (DNA) was recovered from formalin-fixed paraffin-embedded brain tissue. The temporal proximity of the surgery, chemotherapy, and radiotherapy to the onset of disease suggests that these factors may have acted as triggers that precipitated conversion of latent HSV to overt HSV.

Acute demyelination, neuropathological diagnosis, and clinical evolution

A retrospective analysis of 14 patients who presented with a progressively expanding mass lesion(s) shown at biopsy/autopsy to represent acute demyelination was carried out. The aims of this study were to determine the optimal neuropathological approach to diagnosis and to determine the clinical evolution of this condition. Subsequent investigations and clinical outcome studies confirmed MS in 10 cases. Two patients had received an incorrect neuropathologic diagnosis of astrocytoma resulting in cranial irradiation. Key histologic parameters in establishing a diagnosis of acute demyelination were a predominance of lipid filled macrophages, macrophage alignment along axons, and an absence of oligodendroglial inclusions. Axonal injury was present in all cases and a lymphocytic/plasma cell infiltrate was sparse in areas of demyelination. Neuroimaging revealed single lesions in 10 patients and multiple lesions in 4 patients. Two patients were lost to follow-up, 3 died within 18 months of diagnosis, 8 had a relapsing remitting clinical course, and 1 patient had a chronic progressive course. In conclusion, a dense lymphocytic and plasma cell infiltrate is unusual in acute human demyelination. Although axonal injury is a frequent histologic finding in acute demyelination, it does not preclude a favorable clinical outcome.

Crystalloid inclusions in brain macrophages and hemopoietic tissue in GFAP-IL3 mice resemble inclusions identified in multiple sclerosis

Crystalloid inclusions or "pole bodies" observed in brain macrophages in human demyelinating disease represent a morphological enigma. Similar inclusions were detected in brain macrophages from the GFAP-IL3 mouse, a transgenic murine model for macrophage mediated demyelination. Mice also showed inclusions in hematopoietic tissue. They appear to be related to phagocytosis and secretion, respectively, as evidenced by the fact that in phagocytosing cells they often merged with lysozomes and that affected cells showed empty channels open to the interstitium. Based on ultrastructural and immunolocalization studies using chaperonin-10, lysozyme, and cathepsin the authors suggest that these inclusions are consistent with phagocytosis-related secretory products. This study may provide insight into the nature and significance of similar macrophage inclusions recently identified in multiple sclerosis.

Extradural haematoma--a preventable cause of death

Traumatic extradural haematoma (EDH) complicates 1-4% of all head injuries and is a major factor contributing to morbidity and mortality. Clinical awareness and early diagnosis are the keys to successful management. With the advent of computerised tomographic (CT) scanning a trend towards 'zero mortality' has been reported. We report four adolescent cases presenting with mild head injury (Glascow Coma Score 13-15) who subsequently died as a result of EDH. We suggest that excessive delay both in recognising the condition and the subsequent referral and transfer are factors contributing to the mortality of these patients.

Histological parameters as predictors of prognosis in childhood brain tumors

Using histological parameters with high recognition reliability, we retrospectively analyzed all newly diagnosed patients under the age of 16 years (n = 100) with brain and spinal cord tumors presenting to the National Neuroscience Centres of the Richmond and Beaumont Hospitals, Dublin, Ireland, between 1985 and 1990, allowing analysis of 5-year survival in all cases. Tumor histology was reviewed by two neuropathologists blinded to previous histological diagnosis and to the site of lesion. We found that certain histological features such as very low cell density and microcyst formation had a positive effect on prognosis. Mitoses and pleomorphism had a negative effect on prognosis, whereas necrosis and meningeal involvement had no effect on prognosis. It is suggested that identification of reliably recognized histological features rather than assignation of tumors to particular diagnostic categories may be a more reliable predictor of tumor behavior in the pediatric age-group.

MCP-1, MCP-2 and MCP-3 expression in multiple sclerosis lesions: an immunohistochemical and in situ hybridization study

Chemokines are low molecular weight chemotactic cytokines that have been shown to play a central role in the perivascular transmigration and accumulation of specific subsets of leukocytes at sites of tissue damage. Two major families have been defined depending on the positioning of four conserved cysteines. The CXC chemokines predominantly attract neutrophils, whereas the CC chemokines predominantly attract monocytes and other leukocyte cell types. Members of the monocyte chemotactic protein (MCP)-1 family form a major component of the CC family of chemokines and are considered the principal chemokines involved in the recruitment of monocytes/macrophages and activated lymphocytes. In this study we addressed the expression and distribution of MCP-1, -2 and -3 in multiple sclerosis (MS) lesions of differing ages and levels of inflammatory activity using immunohistochemistry and in situ hybridization. In acute and chronic-active MS lesions immunoreactivity for MCP-1, -2 and -3 was prominent throughout the lesion center with reactivity diminishing abruptly at the lesion edge. Hypertrophic astrocytes were strongly reactive and inflammatory cells showed variable reactivity. Outside of the lesion only hypertrophic astrocytes were reactive. The results obtained by in situ hybridization for MCP-1 were in agreement with those obtained by immunostaining. In more chronic lesions immunoreactivity for MCP-1, -2 and -3 was considerably diminished, and in chronic-silent lesions immunoreactivity was restricted to a few scattered reactive astrocytes. Normal control brains showed no immunoreactivity for MCP-1, -2 and -3. Although the cellular distribution of all three members of this family was similar, antibodies to MCP-3 gave prominent staining of the extracellular matrix that was not noted for MCP-1 and -2. These results support the conclusion that members of the MCP family of chemokines are involved in the development of MS lesions in the central nervous system.

Pathogen-free granulomatous diseases of the central nervous system

Pathogen-free granulomatous diseases (PFGD) of the central nervous system (CNS) are a group of disorders with protean clinical and pathological findings. Failure to identify a causative organism leads to considerable diagnostic difficulty. The neuropathology records between 1985 and 1995 were retrospectively reviewed, and the medical records of all patients in whom a diagnosis of PFGD of the CNS was made were retrieved. Patients in whom an infective agent was shown either by culture, special staining techniques, or by immunohistochemical methods were excluded. We identified 11 patients (eight male, three female) who fulfilled the pathological criteria for this condition. Average age at diagnosis was 38.7 years (range, 17 to 78). Neurological symptoms were the presenting feature in nine patients. Neuroimaging findings included hydrocephalus (54.5%), meningeal enhancement (45.5%), and mass lesions (45.5%). Seven patients had antemortem CNS biopsies (brain/meninges [n = 6], spinal [n = 1]), which showed noncaseating granulomas. Eight patients died (mortality rate: 72.7%). Postmortem examination showed granulomatous involvement of the leptomeninges and cerebral parenchyma in all cases with systemic involvement in 50%, chiefly in the form of noncaseating granulomas of the hilar nodes. Six patients fulfilled the clinical, radiological, and pathological diagnostic criteria for neurosarcoidosis. The remaining five patients had an unclassifiable pathogen-free granulomatous disease of the CNS. PFGD of the CNS are associated with a poor prognosis. Although neurosarcoidosis may account for some of the cases, there remains an unclassifiable subgroup that continues to be a diagnostic and management challenge.

Immunohistochemical evaluation of merosin deficiency in congenital muscular dystrophies

OBJECTIVES

To determine the prevalence of merosin deficiency in cases of unclassified congenital muscular dystrophy and to determine the temporal stability of merosin epitopes in fixed and stored archival material.

MATERIALS AND METHODS

Using an antibody to human merosin we retrospectively studied 12 cases of undiagnosed muscular dystrophy from our files to determine the prevalence of merosin deficiency. Where fresh muscle was not available, unstained stored cryostat sections or destained archival stored sections were incubated with the merosin antibody.

RESULTS

Two of the 12 cases of undiagnosed muscular dystrophy were merosin-deficient. No difference in intensity of merosin staining was found between freshly cut cryostat sections and unstained stored cryostat sections. There was no difference in the intensity of merosin staining in sections archived for up to 10 years.

CONCLUSIONS

We conclude that 16% of unclassified muscular dystrophies in our study are due to merosin deficiency and that merosin antigenicity remains intact in archival stored muscle tissue, facilitating retrospective evaluation of patients in whom frozen muscle is not available. To our knowledge, this latter observation has not been reported previously.

Merosin-deficient congenital muscular dystrophy and cortical dysplasia

Congenital muscular dystrophy (CMD) encompasses a heterogenous group of muscle disorders with autosomal recessive inheritance, characterized by muscular weakness and hypotonia at birth or within the first few months of life and developmental delay. Merosin-deficient CMD is a clinically distinct form which may be associated with significant abnormalities of the brain detectable by neuroimaging. We report two siblings of consanguineous parents with merosin-deficient CMD in an Irish family who in addition to the characteristic white matter abnormalities on neuroimaging, had occipital dysplasia. Clinical, electrophysiological muscle biopsy findings and neuroimaging were very similar in both cases. Although merosin-deficient CMD with white matter abnormalities on neuroimaging is well documented in the literature, the association with occipital dysplasia has only rarely been reported. The appearance of an identical cortical defect in these siblings suggests an underlying genetic mechanism.

Effects of seven days of galactose feeding and aldose reductase inhibition on mast cells and vessel morphometry in rat sciatic nerve

The association between mast cells and vessel morphometry in sciatic nerve was examined after seven days in animals fed a diet of 40% D-galactose and compared to control rats and to galactose-fed animals treated with the aldose reductase inhibitor, Tolrestat. Electron microscopy revealed an increase in the total number of mast cells and the number of degranulated mast cells in galactose-fed animals (7.8 +/- 2.9; 2.6 +/- 2.9; mean +/- SD) compared to controls (4.6 +/- 2.1; degranulated mast cells were not seen in any control nerves) and Tolrestat-treated, galactose-fed animals (4.4 +/- 2.5; 0.1 +/- 0.4). Although no significant differences were noted in the numbers of vessels between the three groups, an index of vasoconstriction was significantly increased in the galactose-fed animals (0.115 +/- 0.048; mean +/- SD) compared to controls (0.068 +/- 0.011) and Tolrestat-treated, galactose-fed animals (0.075 +/- 0.20). These data suggest that mast cell degranulation is associated with the vascular constriction induced by seven days of galactose intoxication and that both may be prevented by inhibiting aldose reductase.

Evolution of neuropathologic abnormalities associated with blood-brain barrier breakdown in transgenic mice expressing interleukin-6 in astrocytes

As both astrocytes and cytokines modulate the permeability of cerebral endothelial cells, transgenic animal models which overexpress cytokines, such as interleukin-6 (IL-6), may provide insight into the neuropathological consequences of increased BBB permeability. In this study, a GFAP-IL6 transgenic mouse model and horseradish peroxidase (HRP) were used to investigate BBB permeability and associated neuropathologic changes. In the cerebellum of control mice, the BBB developed between postnatal days 7 and 14. In transgenic mice, the BBB never developed and extensive breakdown was evident in both high- and low-expressor animals by 1 month after birth. Vascular proliferation was apparent from birth in association with development and retention of normal cerebellar architecture until 3 and 6 months in high- and low-expressor animals, respectively. At these times, a leptomeningeal inflammatory infiltrate, vacuolated astrocytic foot processes and endothelial abnormalities were apparent in the cerebellum. At 6 months in high-expressor and 12 months in low-expressor animals, parenchymal inflammation, gliosis, spongiform change, axonal degeneration and macrophage accumulation were evident. The findings suggest that increased production of IL-6 can influence the development and physiologic function of the BBB as well as contribute to parenchymal central nervous system injury.