Widespread spinal cord involvement in corticobasal degeneration

Rapidly Progressive Corticobasal Degeneration Mimicking Brainstem Encephalitis

Background

Corticobasal degeneration (CBD) may have a rapidly progressive (RP) clinical course, mimicking other neurological conditions.

Objectives

To describe a neuropathologically proven case of RP-CBD in a patient initially diagnosed with immune-mediated brainstem encephalitis.

Methods

Retrospective data collection from electronic records and authorized video material.

Results

A 51-year-old man presented with bilateral ptosis, diplopia, and dysphagia. The diagnostic workup was negative for myasthenic syndromes. He progressively developed cognitive dysfunction with frontal release signs and asymmetric parkinsonism. Cerebrospinal fluid evaluation revealed 4 leukocytes/uL, 0.32 g/L proteins, 0.85 g/L glucose, and absent oligoclonal bands. Weakly positive anti-PNMA2 (Ma2/Ta) antibodies were present, and magnetic resonance imaging showed a T2 hyperintensity involving the midbrain and pons. Based on these features, the diagnosis of immune-mediated brainstem encephalitis was considered. The patient did not improve after several cycles of methylprednisolone, intravenous immunoglobulin, and plasma exchange. At 1 year after onset, he developed horizontal and vertical gaze limitation and worsening of the parkinsonism and cognitive dysfunction. By age 53, he was severely disabled, requiring percutaneous gastrostomy for feeding. Anti-IgLON5 was negative. He fulfilled the clinical criteria for probable progressive supranuclear palsy. He died from pneumonia at age 54. The neuropathological examination revealed a 4-repeat tauopathy with features of CBD with extensive involvement of the brainstem.

Conclusions

RP-CBD may resemble brainstem encephalitis. The severity of brainstem and upper spinal cord pathology in the postmortem examination correlated with the clinical and imaging features.

Motor neuron TDP-43 proteinopathy in progressive supranuclear palsy and corticobasal degeneration

Transactive response DNA-binding protein 43 kDa (TDP-43) is mislocalized from the nucleus and aggregates within the cytoplasm of affected neurons in amyotrophic lateral sclerosis (ALS) cases. TDP-43 pathology has also been found in brain tissues under non-ALS conditions, suggesting mechanistic links between TDP-43-related ALS (ALS-TDP) and various neurological disorders. This study aimed to assess TDP-43 pathology in the spinal cord motor neurons of tauopathies. We examined 106 spinal cords from consecutively autopsied cases with progressive supranuclear palsy (PSP, n = 26), corticobasal degeneration (CBD, n = 12), globular glial tauopathy (GGT, n = 5), Alzheimer's disease (AD, n = 21), or Pick disease (PiD, n = 6) and neurologically healthy controls (n = 36). Ten of the PSP cases (38%) and seven of the CBD cases (58%) showed mislocalization and cytoplasmic aggregation of TDP-43 in spinal cord motor neurons, which was prominent in the cervical cord. TDP-43-aggregates were found to be skein-like, round-shaped, granular, or dot-like and contained insoluble C-terminal fragments showing blotting pattern of ALS or frontotemporal lobar degeneration (FTLD). The lower motor neurons also showed cystatin-C aggregates, although Bunina bodies were absent in hematoxylin-eosin staining. The spinal cord TDP-43 pathology was often associated with TDP-43 pathology of the primary motor cortex. Positive correlations were shown between the severities of TDP-43 and 4-repeat (4R)-tau aggregates in the cervical cord. TDP-43 and 4R-tau aggregates burdens positively correlated with microglial burden in anterior horn. TDP-43 pathology of spinal cord motor neuron did not develop in an age-dependent manner and was not found in the AD, PiD, GGT, and control groups. Next, we assessed splicing factor proline/glutamine rich (SFPQ) expression in spinal cord motor neurons; SFPQ is a recently-identified regulator of ALS/FTLD pathogenesis, and it is also reported that interaction between SFPQ and fused-in-sarcoma (FUS) regulates splicing of microtubule-associated protein tau exon 10. Immunofluorescent and proximity-ligation assays revealed altered SFPQ/FUS-interactions in the neuronal nuclei of PSP, CBD, and ALS-TDP cases but not in AD, PiD, and GGT cases. Moreover, SFPQ expression was depleted in neurons containing TDP-43 or 4R-tau aggregates of PSP and CBD cases. Our results indicate that PSP and CBD may have properties of systematic motor neuron TDP-43 proteinopathy, suggesting mechanistic links with ALS-TDP. SFPQ dysfunction, arising from altered interaction with FUS, may be a candidate of the common pathway.

Tau immunoreactivity in peripheral tissues of human aging and select tauopathies

Many studies have been directed at understanding mechanisms of tau aggregation and therapeutics, nearly all focusing on the brain. It is critical to understand the presence of tau in peripheral tissues since this may provide new insights into disease progression and selective vulnerability. The current study sought to determine the presence of select tau species in peripheral tissues in elderly individuals and across an array of tauopathies. Using formalin fixed paraffin embedded sections, we examined abdominal skin, submandibular gland, and sigmoid colon among 69 clinicopathologically defined cases: 19 lacking a clinical neuropathological diagnosis (normal controls), 26 progressive supranuclear palsy (PSP), 21 Alzheimer's disease (AD), and 3 with corticobasal degeneration (CBD). Immunohistochemistry was performed using antibodies for "total" tau (HT7) and two phosphorylated tau species (AT8 and pT231). HT7 staining of abdominal skin revealed immunoreactivity of potential nerve elements in 5% of cases (1 AD, 1 AD/PSP, and 1 CBD out of 55 cases examined); skin sections lacked AT8 and pT231 immunoreactive nerve elements. Submandibular glands from all cases had HT7 immunoreactive nerve elements; while pT231 was present in 92% of cases, and AT8 in only 3 cases (2 AD and one AD/PSP case). In sigmoid colon, HT7 immunoreactivity was present in all but 2 cases (97%), pT231 in 54%, and AT8 was present in only 5/62 cases (8%). These data suggest select tau species in CNS tauopathies do not have a high propensity to spread to the periphery and this may hold clues for the understanding of CNS tau pathogenicity and vulnerability.

The distribution of phosphorylated tau in spinal cords of Alzheimer's disease and non-demented individuals

Abnormal phosphorylation of the microtubule-associated protein tau develops in selected brain regions in normal aging and becomes widespread throughout the brain in Alzheimer's disease (AD). Braak and others have described the distribution of neurofibrillary tangles and deposition of abnormally phosphorylated tau (p-tau) and correlated this with the progressive cognitive dysfunction in AD. However, to date there have been no comprehensive studies examining abnormally phosphorylated tau deposition in the spinal cord as part of normal aging or AD. We investigated, using immunohistochemical methods, the presence of p-tau in the spinal cord of 46 cases with a clinicopathological diagnosis of AD as well as 37 non-demented aged (ND) individuals lacking any defined central nervous system-related clinicopathological diagnosis. We found the cervical cord segments to be the most frequently affected subdivision (96% AD versus 43% ND), followed by thoracic (69% AD versus 37% ND), lumbar (65% AD versus 27% ND), and sacral (53% AD versus 13% ND). The spinal cord was often affected at early-stage brain disease, with p-tau spinal cord immunoreactivity in 40% of subjects at Braak neurofibrillary stage I; however, there were no cases having spinal cord p-tau that did not have p-tau within the brain. As p-tau immunoreactivity is present within the spinal cords of ND as well as AD subjects, it is likely that the phosphorylation of spinal cord tau occurs in the preclinical stage of AD, prior to dementia. The presence of significant spinal cord p-tau-immunoreactive pathology has important implications for both the pathogenesis and clinical manifestations of AD.

Involvement of the peripheral nervous system in synucleinopathies, tauopathies and other neurodegenerative proteinopathies of the brain

Involvement of the peripheral nervous system (PNS) is relatively common in some neurodegenerative proteinopathies of the brain and may be pathogenetically and diagnostically important. In Parkinson's disease, neuronal alpha-synuclein aggregates are distributed throughout the nervous system, including the central nervous system (CNS), sympathetic ganglia, enteric nervous system, cardiac and pelvic plexuses, submandibular gland, adrenal medulla and skin. The pathological process may target the PNS and CNS at the same time. In multiple system atrophy, numerous glial cytoplasmic inclusions composed of filamentous alpha-synuclein are widely distributed in the CNS, while alpha-synuclein accumulation is minimal in the sympathetic ganglia and is restricted to neurons. Neurofibrillary tangles can occur in the sympathetic and spinal ganglia in tauopathy, although they appear to develop independently of cerebral Alzheimer's disease pathology. In amyotrophic lateral sclerosis, neuronal loss with TDP-43-positive neuronal cytoplasmic inclusions in the spinal ganglia is more frequent than previously thought. Peripheral ganglia and visceral organs are also involved in polyglutamine diseases. Further elucidation and characterization of PNS lesions will have implications for intravital biopsy diagnosis in neurodegenerative proteinopathy, particularly in Parkinson's disease.

Spinal cord tau pathology in cervical spondylotic myelopathy

We conducted an immunohistochemical and ultrastructural examination of the spinal cords from 11 cases of cervical spondylotic myelopathy (CSM), together with those from 11 age- and sex-matched control subjects. Immunostaining with AT8 antibody revealed various numbers of tau-positive neuropil thread-like structures (NTSs), often demonstrating a conspicuous astrocytic foot-like perivascular or subpial arrangement, and glial cells with short and thick processes, so-called thorn-shaped astrocytes (TSAs), in the affected cervical cords in 8 of the 11 CSM cases (73%). A number of tau-positive neuronal cytoplasmic pretangles/tangles were also found in the gray matter in all the CSM cases (100%). No such astrocytic or neuronal tau lesions were found in the control subjects. The tau deposited in the NTSs and TSAs was predominantly 4-repeat tau, whereas the neuronal cytoplasmic pretangles/tangles contained both 3-repeat and 4-repeat tau. Ultrastructurally, paired helical filaments about 20 nm wide, together with glial filaments, were detected occasionally in the astrocytic processes. In conclusion, the present findings indicate that astrocytic and neuronal tau lesions appear in the affected cervical cord during the disease process of CSM.

Widespread spinal cord involvement in progressive supranuclear palsy

We describe the histopathologic features of spinal cord lesions in 10 cases of progressive supranuclear palsy (PSP) and review the literature. Histologic examination revealed atrophy with myelin pallor in the anterior funiculus and anterolateral funiculus in the cervical and thoracic segments in eight of the 10 cases, whereas the posterior funiculus was well preserved. The degrees of atrophy of the anterior funiculus and the anterolateral funiculus correlated with that of the tegmentum of the medulla oblongata. Myelin pallor of the lateral corticospinal tract was observed in two of the 10 cases. Microscopic observation of the spinal white matter, particularly the cervical segment, revealed a few to several neuropil threads, particularly in the white matter surrounding the anterior horn after Gallyas-Braak (GB) staining or AT-8 tau immunostaining. However, the posterior funiculus was completely preserved from the presence of argyrophilic or tau-positive structures. In the spinal gray matter, widespread distribution of neurons with cytoplasmic inclusions and neuropil threads was observed, particularly in the medial division of the anterior horn and intermediate gray matter, especially in the cervical segment. Globose-type neurofibrillary tangles and pretangles were found. The distribution of GB- or AT-8 tau-positive small neurons and neuropil threads resembled that of the spinal interneurons. In conclusion, the spinal cord, especially the cervical segment, is constantly involved in the pathologic process of PSP. We speculate that spinal interneurons and their neuronal processes, particularly in the medial division of the anterior horn and intermediate gray matter of the cervical segment, are most severely damaged in the PSP spinal cord.

Enhanced Aquaporin-4 immunoreactivity in sporadic Creutzfeldt-Jakob disease

Aquaporin-4 (AQP-4) is a water channel protein located on the plasma membrane of astrocytes and is regulated under various conditions. In the present study, a series of brains with sporadic Creutzfeldt-Jakob disease (sCJD) were investigated to determine the possible contribution of AQP-4 in the development of sCJD pathology. Six cases of subacute spongiform encephalopathy (SSE) and four cases of panencephalopathic (PE)-type sCJD were included. Increased AQP-4 immunoreactivity compared to that in controls was observed in all sCJD patients, particularly in the cerebral neocortex and cerebellar cortex. AQP-4 immunoreactivity was present in the cell bodies and processes of protoplasmic astrocytes in SSE and around cell bodies and processes of hypertrophic astrocytes in PE-type sCJD. Analysis of serial sections showed the development of sCJD pathology, particularly in neocortical lesions, as follows: PrP deposition; spongiform change and gliosis; enhanced staining for AQP-4; hypertrophic astrocytosis; and neuronal loss and tissue rarefaction. Strong AQP-4 immunoreactivity was present in burnt-out lesions such as those of status spongiosus. These results indicate that increased AQP-4 expression in sCJD is an early pathologic event and appears to remain until the late disease stage. We suggest that increased expression of AQP-4 is a pathologic feature of sCJD.

Parkinsonian syndromes

The term parkinsonian syndromes refers to a group of disorders whose clinical features overlap those of idiopathic Parkinson's disease. The four major entities include three important neurodegenerations, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration, and a lacunar cerebrovascular disorder, vascular parkinsonism. This article reviews the epidemiology, pathology, clinical features, diagnosis, and management of these disorders.

Corticobasal degeneration with focal, massive tau accumulation in the subcortical white matter astrocytes

We report two sporadic cases of tauopathy with unusual neuropathological features. The ages of the patients at death were 86 and 74 years, and the disease durations were 4 and 3 years, respectively. The former patient showed progressive dementia and amyotrophy (autopsy revealed that severe cervical spondylosis was responsible for the amyotrophy), and the latter showed progressive parkinsonism and dementia. The essential brain pathologies were similar to each other; although ballooned neurons and astrocytic tau lesions (astrocytic plaques) were present in the affected cerebral cortex, the most striking finding was focal, much heavier accumulation of tau in the subcortical white matter. Moreover, double-labeling immunostaining, as well as Gallyas-Braak electron and AT8 immunoelectron microscopic studies strongly suggested that in the affected subcortical white matter, the accumulation of tau occurred mainly in the astrocytic processes. In the latter patient, for whom frozen brain tissue was available, immunoblotting of insoluble tau revealed a pattern compatible with that obtained from brain affected by typical corticobasal degeneration (CBD), and gene analysis of tau revealed no mutations, with a H1 haplotype. Finally, in both cases, the pathological diagnosis of CBD was considered to be appropriate. However, the tau pathology affecting the subcortical white matter astrocytes was very unusual for the disease.