Corticobasal syndrome presenting Foix-Chavany-Marie syndrome with suggested 4-repeat tauopathy by tau PET

Background: Corticobasal syndrome (CBS) is a neurodegenerative disease diagnosed based on clinical manifestations such as asymmetrical parkinsonism, limb apraxia, and speech and language impairment. Foix-Chavany-Marie syndrome (FCMS) is a rare neurological disorder characterized by bilateral impairment of voluntary movement in the facial, pharyngeal, lingual, and masticatory muscles, leading to apraxia of speech. FCMS is commonly attributable to stroke. Transactive response DNA binding protein of 43 kD (TDP-43) proteinopathy is also known as the pathological background of FCMS, while the pathological background of the majority of CBS cases are diverse tauopathies instead of TDP-43 proteinopathy. In this report, we describe a case of FCMS that finally received a diagnosis of CBS with suggested 4-repeat tauopathy. Case presentation: A 68-year-old female started experiencing difficulty speaking followed by difficulty writing, especially texting difficulty, several years before her visit. Her impairment had been gradually worsening, and she came to our hospital. On neurological examination, she demonstrated the facial apraxia, frontal lobe dysfunction, and upper motor neuron signs. Based on her clinical features, she was diagnosed with FCMS. Her symptoms exhibited rapid progression and myoclonus, parkinsonism, and left-side dominant cortical sensory deficit occurred, resulting in the fulfillment of diagnostic criteria for CBS after 9 months. Tau PET imaging displayed notable ligand uptake in the brainstem, subthalamic nuclei, basal ganglia, and bilateral subcortical frontal lobe, suggesting her pathological background was 4-repeat tauopathy. As a result of the progressive dysphagia, she became unable to eat and passed away at 12 months. Conclusion: We hereby present an atypical case of CBS presenting with rapidly progressive FCMS. TDP-43 proteinopathy was suspected based on the clinical symptoms in the early stages of the disease; however, tau PET suggested that her pathological background was 4-repeat tauopathy.