Juan M. Bilbao

Understanding White Matter Disease: Imaging-Pathological Correlations in Vascular Cognitive Impairment

Most strokes are covert and observed incidentally on brain scans, but their presence increases risk of overt stroke and dementia. Amyloid angiopathy, associated with Alzheimer Disease (AD) causes stroke, and when even small strokes coexist with AD, they lower the threshold for dementia. Diffuse ischemic white matter disease impairs executive functioning, information processing speed, and gait. Neuroimaging techniques, such as tissue segmentation, Diffusion Tensor Imaging, MR Spectroscopy, functional MRI and amyloid PET, probe microstructural integrity, molecular biology, and activation patterns, providing new insights into brain-behavior relationships. MR-pathological studies of periventricular hyperintensity (leukoaraiosis) in aging and dementia reveal arteriolar tortuosity, reduced vessel density, and occlusive venous collagenosis which causes venous insufficiency and vasogenic edema. Activated microglia, oligodendroglial apoptosis, clasmatodendritic astrocytosis, and upregulated hypoxia-markers are seen on immunohistochemistry. Further research is needed to understand and treat this chronic subcortical vascular disease, which is epidemic in our aging population.

Lymphocytic hypophysitis of pregnancy resulting in hypopituitarism: a distinct clinicopathologic entity.

Two patients presented with abnormalities suggestive of pituitary adenoma; one during pregnancy and one in the postpartum period. However, pathologic examination of the pituitary showed extensive destruction by a lymphoplasmacytic infiltrate; no tumor was identified. Both patients developed hypopituitarism. We know of eight additional cases of lymphocytic hypophysitis, seven of which have been reported in the literature. In only three cases, including the two reported here, the diagnosis was established by biopsy. In each of those cases, the entity mimicked a pituitary tumor. This is the first report of electron microscopy of this lesion and the ultrastructural features support the previously suggested autoimmune etiology. The lesion has been described only in women and seven of ten patients were pregnant or postpartum at the onset. This fact and previously reported experimental evidence, including the identification of anti-prolactin cell antibodies, support our suggestion that lymphocytic hypophysitis associated with pregnancy represents a distinct clinicopathologic entity.

A Multicenter Study of Glucocerebrosidase Mutations in Dementia With Lewy Bodies

IMPORTANCE While mutations in glucocerebrosidase (GBA1) are associated with an increased risk for Parkinson disease (PD), it is important to establish whether such mutations are also a common risk factor for other Lewy body disorders. OBJECTIVE To establish whether GBA1 mutations are a risk factor for dementia with Lewy bodies (DLB). DESIGN We compared genotype data on patients and controls from 11 centers. Data concerning demographics, age at onset, disease duration, and clinical and pathological features were collected when available. We conducted pooled analyses using logistic regression to investigate GBA1 mutation carrier status as predicting DLB or PD with dementia status, using common control subjects as a reference group. Random-effects meta-analyses were conducted to account for additional heterogeneity. SETTING Eleven centers from sites around the world performing genotyping. PARTICIPANTS Seven hundred twenty-one cases met diagnostic criteria for DLB and 151 had PD with dementia. We compared these cases with 1962 controls from the same centers matched for age, sex, and ethnicity. MAIN OUTCOME MEASURES Frequency of GBA1 mutations in cases and controls. RESULTS We found a significant association between GBA1 mutation carrier status and DLB, with an odds ratio of 8.28 (95% CI, 4.78-14.88). The odds ratio for PD with dementia was 6.48 (95% CI, 2.53-15.37). The mean age at diagnosis of DLB was earlier in GBA1 mutation carriers than in noncarriers (63.5 vs 68.9 years; P < .001), with higher disease severity scores. CONCLUSIONS AND RELEVANCE Mutations in GBA1 are a significant risk factor for DLB. GBA1 mutations likely play an even larger role in the genetic etiology of DLB than in PD, providing insight into the role of glucocerebrosidase in Lewy body disease.

FET proteins TAF15 and EWS are selective markers that distinguish FTLD with FUS pathology from amyotrophic lateral sclerosis with FUS mutations

Accumulation of the DNA/RNA binding protein fused in sarcoma as cytoplasmic inclusions in neurons and glial cells is the pathological hallmark of all patients with amyotrophic lateral sclerosis with mutations in FUS as well as in several subtypes of frontotemporal lobar degeneration, which are not associated with FUS mutations. The mechanisms leading to inclusion formation and fused in sarcoma-associated neurodegeneration are only poorly understood. Because fused in sarcoma belongs to a family of proteins known as FET, which also includes Ewings sarcoma and TATA-binding protein-associated factor 15, we investigated the potential involvement of these other FET protein family members in the pathogenesis of fused in sarcoma proteinopathies. Immunohistochemical analysis of FET proteins revealed a striking difference among the various conditions, with pathology in amyotrophic lateral sclerosis with FUS mutations being labelled exclusively for fused in sarcoma, whereas fused in sarcoma-positive inclusions in subtypes of frontotemporal lobar degeneration also consistently immunostained for TATA-binding protein-associated factor 15 and variably for Ewings sarcoma. Immunoblot analysis of proteins extracted from post-mortem tissue of frontotemporal lobar degeneration with fused in sarcoma pathology demonstrated a relative shift of all FET proteins towards insoluble protein fractions, while genetic analysis of the TATA-binding protein-associated factor 15 and Ewings sarcoma gene did not identify any pathogenic variants. Cell culture experiments replicated the findings of amyotrophic lateral sclerosis with FUS mutations by confirming the absence of TATA-binding protein-associated factor 15 and Ewings sarcoma alterations upon expression of mutant fused in sarcoma. In contrast, all endogenous FET proteins were recruited into cytoplasmic stress granules upon general inhibition of Transportin-mediated nuclear import, mimicking the findings in frontotemporal lobar degeneration with fused in sarcoma pathology. These results allow a separation of fused in sarcoma proteinopathies caused by FUS mutations from those without a known genetic cause based on neuropathological features. More importantly, our data imply different pathological processes underlying inclusion formation and cell death between both conditions; the pathogenesis in amyotrophic lateral sclerosis with FUS mutations appears to be more restricted to dysfunction of fused in sarcoma, while a more global and complex dysregulation of all FET proteins is involved in the subtypes of frontotemporal lobar degeneration with fused in sarcoma pathology.

Amyotrophic lateral sclerosis is a non-amyloid disease in which extensive misfolding of SOD1 is unique to the familial form

Amyotrophic lateral sclerosis (ALS) is a conformational disease in which misfolding and aggregation of proteins such as SOD1 (familial ALS) and TDP-43 (sporadic ALS) are central features. The conformations adopted by such proteins within motor neurons in affected patients are not well known. We have developed a novel conformation-specific antibody (USOD) targeted against SOD1 residues 42–48 that specifically recognizes SOD1 in which the beta barrel is unfolded. Use of this antibody, in conjunction with the previously described SEDI antibody that recognizes the SOD1 dimer interface, allows a detailed investigation of the in vivo conformation of SOD1 at the residue-specific level. USOD and SEDI immunohistochemistry of spinal cord sections from ALS cases resulting from SOD1 mutations (A4V and ΔG27/P28) shows that inclusions within remaining motor neurons contain SOD1 with both an unfolded beta barrel and a disrupted dimer interface. Misfolded SOD1 can also be immunoprecipitated from spinal cord extracts of these cases using USOD. However, in ten cases of sporadic ALS, misfolded SOD1 is not detected by either immunohistochemistry or immunoprecipitation. Using the amyloid-specific dyes, Congo Red and Thioflavin S, we find that SOD1-positive inclusions in familial ALS, as well as TDP-43- and ubiquitin-positive inclusions in sporadic ALS, contain non-amyloid protein deposits. We conclude that SOD1 misfolding is not a feature of sporadic ALS, and that both SOD1-ALS and sporadic ALS, rather than being amyloid diseases, are conformational diseases that involve amorphous aggregation of misfolded protein. This knowledge will provide new insights into subcellular events that cause misfolding, aggregation and toxicity.

Xanthochromic cysts associated with meningioma.

Three cases of cystic meningioma encountered in one year are presented. It appears from a review of the literature, and an analysis of these three cases, that large xanthochromic cerebral cysts may be associated with meningiomas in any of three configurations: (1) centrally within the tumour; (2) peripherally within the tumour; (3) in the adjacent brain. Regardless of which configuration applies, the CAT scan appearance of such cystic meningiomas may mimic that of a glial tumour with cystic or necrotic change, and lead to an incorrect presumptive diagnosis. This false impression may be perpetuated by the gross appearance at operation, which can also mimic malignant glioma. Although several radiological features should suggest the possible presence of a cystic meningioma, we know of no definite radiological means of differentiating this lesion from the more common malignant glioma. This finding should underline the need to biopsy all suspected cerebral neoplasms, regardless of how much their appearance on CAT scan may suggest malignant glioma.

RNA targets of TDP-43 identified by UV-CLIP are deregulated in ALS

TDP-43 is a predominantly nuclear DNA/RNA binding protein involved in transcriptional regulation and RNA processing. TDP-43 is also a component of the cytoplasmic inclusion bodies characteristic of amyotrophic lateral sclerosis (ALS) and of frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U). We have investigated the premise that abnormalities of TDP-43 in disease would be reflected by changes in processing of its target RNAs. To this end, we have firstly identified RNA targets of TDP-43 using UV-Cross-Linking and Immunoprecipitation (UV-CLIP) of SHSY5Y cells, a human neuroblastoma cell line. We used conventional cloning strategies to identify, after quality control steps, 127 targets. Results show that TDP-43 binds mainly to introns at UG/TG repeat motifs (49%) and polypyrimidine rich sequences (17.65%). To determine if the identified RNA targets of TDP-43 were abnormally processed in ALS versus control lumbar spinal cord RNA, we performed RT-PCR using primers designed according to the location of TDP-43 binding within the gene, and prior evidence of alternative splicing of exons adjacent to this site. Of eight genes meeting these criteria, five were differentially spliced in ALS versus control. This supports the premise that abnormalities of TDP-43 in ALS are reflected in changes of RNA processing.

Pathological heterogeneity in amyotrophic lateral sclerosis with FUS mutations: two distinct patterns correlating with disease severity and mutation.

Mutations in the gene encoding the fused in sarcoma (FUS) protein are responsible for ~3% of familial amyotrophic lateral sclerosis (ALS) and <1% of sporadic ALS (ALS-FUS). Descriptions of the associated neuropathology are few and largely restricted to individual case reports. To better define the neuropathology associated with FUS mutations, we have undertaken a detailed comparative analysis of six cases of ALS-FUS that include sporadic and familial cases, with both juvenile and adult onset, and with four different FUS mutations. We found significant pathological heterogeneity among our cases, with two distinct patterns that correlated with the disease severity and the specific mutation. Frequent basophilic inclusions and round FUS-immunoreactive (FUS-ir) neuronal cytoplasmic inclusions (NCI) were a consistent feature of our early-onset cases, including two with the p.P525L mutation. In contrast, our late-onset cases that included two with the p.R521C mutation had tangle-like NCI and numerous FUS-ir glial cytoplasmic inclusions. Double-labeling experiments demonstrated that many of the glial inclusions were in oligodendrocytes. Comparison with the neuropathology of cases of frontotemporal lobar degeneration with FUS-ir pathology showed significant differences and suggests that FUS mutations are associated with a distinct pathobiology.

Biopsy Diagnosis of Peripheral Neuropathy

CONTENTS: Role of nerve biopsy in clinical practice Special techniques in examination of peripheral nerve Normal structure of peripheral nerve, and pathologic alterations of vascular elements Normal structure and pathological alterations of axons Schwann cells and myelin in the peripheral nervous system Normal vascular anatomy and pathological alterations Examination of the peripheral nerve biopsy Clinical issues in peripheral nerve disease Idiopathic inflammatory demyelinating polyneuropathies Idiopathic inflammatory neuropathies Infectious or infection associated neuropathy Leprous neuropathy Vasculitic neuropathy Dysproteinemic neuropathies Amyloid neuropathy Neuropathy associated with neoplasia Neuropathies associated with endocrine/metabolic disease Toxic neuropathies Genetically based neuropathies Peripheral nerves in storage diseases Unclassified neuropathies and peripheral nerve syndromes.

The Significance of Spinal Cord Compression as the Initial Manifestation of Lymphoma

Eighteen patients with spinal cord compression caused by previously undiagnosed lymphoma were treated at our institution between 1976 and 1991. There were 14 male and 4 female patients (mean age, 58.2 years). The absence of bony involvement on radiographic images was a feature in 16 of the cases. All patients underwent laminectomy for decompression and tissue diagnosis, after which 5 underwent radiotherapy, 3 underwent chemotherapy, and 10 underwent combined-modality treatment. The functional outcome was improvement in 8 patients and no change in 10; no patient worsened after surgery. Eleven had advanced disease at diagnosis, while seven had limited disease, including three patients with localized extradural lymphoma. There were 16 cases of non-Hodgkins lymphoma and 2 of Hodgkins disease. Two patients had T-cell lymphoma and were among the longest survivors. DNA flow cytometry identified the low-grade tumors as diploid with very low proliferative indices, while the high-grade tumors all had high indices. At a mean observation time of 41.7 months, five patients have died of their disease, and seven remain in complete remission. Survival is markedly better than that reported for other malignant extradural tumors; however, even limited stage lymphoma can behave aggressively. Similarities in age, sex distribution, histological features, and the results of flow cytometry suggest behavior similar to extranodal lymphoma at other sites. Surgery to provide a tissue diagnosis, followed by combined radiotherapy and chemotherapy, is indicated for all cases.