Case Report: Semantic Variant of Primary Progressive Aphasia Associated With Anti-Glial Fibrillary Acid Protein Autoantibodies

BackgroundFrontotemporal lobar degeneration is a heterogeneous disorder entailing a semantic variant of primary progressive aphasia (svPPA). A subtype of frontotemporal dementia associated with glutamate receptor subunit 3 (GluA3) antibody of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) was recently identified. Here, we describe the novelty of a svPPA associated with anti-glial fibrillary acid protein (GFAP) antibodies.MethodsTo diagnose this 68-year-old woman we conducted a clinical examination, neuropsychological testing, CSF analysis, MRI and 18F-fluorodeoxyglucose (18F-FDG) Positron Emission Tomography (PET)/computed tomography (CT) imaging.ResultsThe clinical phenotype corresponds to a svPPA based on impaired confrontation naming and single-word comprehension. In addition, we observed spared speech production, impaired object knowledge, and surface dyslexia - further supporting the diagnosis of svPPA. Additional characteristic imaging features such as anterior temporal hypometabolism in 18F-FDG PET/CT confirmed patient’s svPPA diagnosis. CSF analysis revealed signs of axonal degeneration, as both tau and phosphorylated tau proteins exceeded normal levels. Her serum showed anti-GFAP autoantibodies.ConclusionWe diagnosed a svPPA in this patient and report an association between serum anti-GFAP antibodies and svPPA never reported in the literature so far, thereby expanding the clinical spectrum of svPPA and anti-GFAP-antibody related disease. Further research is needed to elucidate the underlying immunopathology of this disease entity to ultimately improve treatment.

Neuronavigated repetitive transcranial magnetic stimulation as novel mapping technique provides insights into language function in primary progressive aphasia

Navigated repetitive transcranial magnetic stimulation (nrTMS) is an innovative technique that provides insight into language function with high accuracy in time and space. So far, nrTMS has mainly been applied in presurgical language mapping of patients with intracranial neoplasms. For the present study, nrTMS was used for language mapping in primary progressive aphasia (PPA). Seven patients (median age: 70 years, 4 males) with the non-fluent variant of PPA (nfvPPA) were included in this pilot study. Trains of nrTMS (5 Hz, 100% resting motor threshold) caused virtual lesions at 46 standardized cortical stimulation targets per hemisphere. Patients’ errors in a naming task during stimulation were counted. The majority of errors induced occurred during frontal lobe stimulation (34.3%). Timing errors and non-responses were most frequent. More errors were induced in the right hemisphere (58%) than in the left hemisphere (42%). Mapping was tolerated by all patients, however, discomfort or pain was reported for stimulation of frontal areas. The elevated right-hemispheric error rate in our study could be due to a partial shift of language function to the right hemisphere in neurodegenerative aphasia during the course of disease and therefore points to the existence of neuronal plasticity in nfvPPA. While this is an interesting finding for neurodegenerative disorders per se, its promotion might also harbor future therapeutic targets.

Primary progressive aphasias: clinical and genetic heterogeneity and diagnostic difficulties

This systematic review describes primary progressive aphasia (PPA) variants and includes the authors' own clinical observations. Over 20 genes have now been identified, with mutations that are directly involved in the development of the behavioural variant of frontotemporal dementia, as well as other forms of PPA. Pathomorphological markers of Alzheimer's disease were identified in 76% of cases of logopenic PPA, while signs of frontotemporal dementia associated with TDP-43 were identified in 80% of cases of the semantic variant, and those associated with TDP-43/tau were identified in 64% of cases of agrammatic PPA. The clinical diagnosis of PPA is based on a history of long-term, progressive speech disturbances and identifying a particular variant: agrammatic, semantic or logopenic. The primary variant of the speech disorder cannot be identified in approximately 30% of cases. The focus should be on the main and additional clinical signs (presence of agrammatism, object naming, word comprehension, preserved repetition), as well as neuroimaging (presence of asymmetrical frontal and/or temporal lobe atrophy). The article also provides key aspects of differential diagnosis of the PPA variants, and puts forth a stepwise diagnostic algorithm. It examines features of PPA progression, with possible development of corticobasal syndrome, illustrated by a clinical case. A dissociation between neuroimaging findings and clinical disease variant is also demonstrated to be possible. Different neuropsychological assessments of patients with aphasia and methods of determining the severity of speech dysfunction are presented. Standardized aphasia assessment tools and the adapted PPA severity scale are provided.