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HOME > J Mov Disord > Volume 18(4); 2025 > Article
Letter to the editor
 Atypical Imaging Findings in Corticobasal Syndrome: A Case Report
Hyunji Kim1*orcid, Seo Young Kang2orcid, Ji Young Yun1corresp_iconorcid, Jee Hyang Jeong1corresp_iconorcid
Journal of Movement Disorders 2025;18(4):365-368.
DOI: https://doi.org/10.14802/jmd.25034
Published online: May 22, 2025

1Department of Neurology, Ewha Womans University Seoul Hospital, Ewha Womans University College of Medicine, Seoul, Korea

2Department of Nuclear Medicine, Ewha Womans University Seoul Hospital, Ewha Womans University College of Medicine, Seoul, Korea

Corresponding author: Ji Young Yun, MD, PhD Department of Neurology, Ewha Womans University Seoul Hospital, Ewha Womans University College of Medicine, 260 Gonghang-daero, Gangseo-gu, Seoul 07804, Korea / Tel: +82-2-6986-1743 / E-mail: dream-yoon@hanmail.net, movement@ewha.ac.kr
Corresponding author: Jee Hyang Jeong, MD, PhD Department of Neurology, Ewha Womans University Seoul Hospital, Ewha Womans University College of Medicine, 260 Gonghang-daero, Gangseo-gu, Seoul 07804, Korea / Tel: +82-2-6986-1792 / E-mail: jjeong@ewha.ac.kr
*Current affiliation: Dizziness Center, Clinical Neuroscience Center, Department of Neurology, Seoul National University Bundang Hospital, Seongnam, Korea
• Received: February 7, 2025   • Revised: April 2, 2025   • Accepted: May 22, 2025

Copyright © 2025 The Korean Movement Disorder Society

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Dear Editor,
Corticobasal syndrome (CBS) is a rare, progressive neurodegenerative disease characterized by asymmetric cortical and extrapyramidal features [1]. CBS represents a clinical syndrome associated with diverse pathological substrates, including corticobasal degeneration (CBD), Alzheimer’s disease (AD), and Lewy body dementia. The largest autopsy-controlled study involving 40 CBS patients identified CBD in 35% and AD in 23% of patients [2]. Despite the high proportion of AD pathology in patients with CBS, achieving clinicopathological differential diagnosis during life remains critical.
Clinically, patients with CBS-AD exhibit higher frequencies of myoclonus, visual neglect, and cortical sensory loss [1,2]. In neuropsychological assessments, visuospatial impairment is suggestive of CBS-AD, whereas frontal dysexecutive function is indicative of CBS-CBD [1]. Despite these clinical distinctions, determining the underlying pathology through neuroclinical evaluation remains challenging. Pathological studies and research using positron emission tomography (PET) imaging can facilitate the differentiation of AD from other pathologies and broaden our understanding of CBS.
Amyloid PET imaging distinguishes AD pathology from non-AD pathology. Amyloid PET imaging in patients with AD shows diffuse ligand uptake in cortical gray matter and the striatum, with relatively unaffected uptake in regions such as subcortical white matter, the pons, and the cerebellum [3]. CBS-AD patients are known to exhibit a similar diffuse amyloid PET pattern. However, no comparative amyloid PET imaging studies between CBS-AD and CBS-CBD have been reported.
We present a case of probable CBS with amyloid PET positivity observed in the asymmetric ventral diencephalon and adjacent structures. A 76-year-old woman with gradual cognitive impairment and gait disturbance visited our clinic. She experienced progressive gait disturbance and recurrent falls, necessitating wheelchair use. She also reported difficulties with word finding and impaired judgment but demonstrated relatively preserved memory. Her medical history was unremarkable.
On examination, the patient exhibited slurred speech and nonfluent aphasia alongside buccofacial and ideomotor apraxia. Despite intact muscle strength, she showed severe postural instability and gait disturbance accompanied by right dominant dystonia, clumsiness, rigidity, and hyperreflexia, suggesting dysfunction of the left extrapyramidal tract. Neuropsychological evaluation revealed prodromal dementia, with instrumental activities of daily living deteriorating to a borderline level. The Mini-Mental State Examination score was 25/30, and the clinical dementia rating was 0.5. She presented with symptoms of Gerstmann syndrome, including dysgraphia, dyscalculia, right‒left disorientation, and perseveration, along with severely impaired frontal executive functions.
Dopamine transporter (DAT) PET imaging with N-3[18F]fluoropropyl-2β-carbomethoxy-3β-4-iodophenyl nortropane revealed reduced striatal uptake in the left posterior putamen (Figure 1A). The standardized uptake value ratio (SUVR) of the left posterior putamen decreased, with the asymmetry index (AI) of -10.14% (SUVR: left 2.66, right 3.26) (Supplementary Material in the online-only Data Supplement).
Amyloid PET imaging with [18F]florapronol revealed a positive scan, predominantly involving the left frontal (AI 3.206%), bilateral parietal (AI 7.828%), left posterior transverse temporal cortices (AI 7.650%), and the left thalamus (AI 6.611%) extending to the midbrain (Figure 1B, C, and Supplementary Material in the online-only Data Supplement).
The patient was initially diagnosed with probable CBS on the basis of asymmetric cortical and extrapyramidal signs. With asymmetric cortical atrophy on magnetic resonance imaging (MRI), a subsequent amyloid PET scan revealed significant amyloid deposition in the deep diencephalic regions contralateral to the symptoms. She was subsequently managed with oral donepezil and levodopa therapy and showed no remarkable response to levodopa.
Recent advances in tau- and amyloid-targeted therapies have prioritized determining the underlying pathology for treatment. Owing to the overlap in the clinical presentations of CBS, researchers have aimed to identify specific features that distinguish CBS-AD from CBS-CBD. Previous pathological studies revealed substantia nigral degeneration in both CBS-AD and CBS-CBD patients with respect to parkinsonism [4]. In a recent case report, a patient with probable CBS had pathologically confirmed concomitant Alzheimer’s and Lewy-related pathology [5]. Immunohistochemistry revealed tau protein deposits in the midbrain at the level of the substantia nigra, indicating Alzheimer’s pathology. These postmortem pathological studies provide accurate pathology and confirm the diagnosis; however, their implementation in clinical practice is often limited. The findings underscore the need to identify in vivo biomarkers that can be used to determine the underlying pathology and differential diagnosis.
On brain MRI, the most accessible structural imaging technique, CBS patients present asymmetric cortical atrophy contralateral to the clinically affected side [2]. However, volumetric asymmetry analysis demonstrated that the asymmetric cortical atrophy pattern is not specific to any particular underlying pathology in CBS patients [2].
Amyloid PET imaging of CBS-AD patients revealed patterns similar to those of AD patients, with diffuse ligand uptake in the cortical gray matter and striatum [3]. While there have been reports indicating that cortical deposition precedes striatal deposition in the progression of AD [6], there are currently no documented cases suggesting that the primary amyloid deposition site is located within the deep diencephalon and adjacent structures.
To our knowledge, this may be a rare instance of asymmetric parkinsonism accompanied by in vivo amyloid deposition involving the ventral diencephalon and adjacent structures, although the causal relationship remains uncertain. It is hypothesized that a presynaptic dopaminergic deficit at the site of amyloid deposition may lead to contralateral extrapyramidal symptoms via the dopaminergic pathway, which is supported by a reduction in the ipsilateral putaminal DAT binding uptake. Like many CBS patients, this patient exhibited levodopa-nonresponsive parkinsonism, possibly related to asymmetrical amyloid deposition affecting cortical and presynaptic dopaminergic function.
Several counterarguments can be made regarding this interpretation. First, the amyloid plaque-specific radiotracer we used, [18F]florapronol, was developed and studied in South Korea to demonstrate concordant amyloid positivity [7]. However, it has not been approved by the United States Food and Drug Administration because of the absence of brain autopsy confirmation. A study suggested that the striatal uptake was greater in the negative scan with [18F]florapronol than with other radiotracers [7]. For our patient, we used [18F]florapronol for amyloid PET imaging and detected striatal uptake, which may affect the reliability of meaningful interpretation. Nevertheless, asymmetric uptake still provides potentially valuable information regarding the patient’s symptoms. Second, the absence of tau imaging limits the confirmation of tau deposition at sites of amyloid accumulation, leaving room for alternative pathological possibilities and constraining interpretation.
This localized and dense amyloid deposition may be indicative of the heterogeneity of CBS and could broaden the understanding of this complex disease. Additionally, these findings underscore the importance of in vivo biomarkers, such as PET imaging with specific ligands, for identifying underlying mixed pathology in the pursuit of more accurate diagnosis and management in clinical practice.
The online-only Data Supplement is available with this article at https://doi.org/10.14802/jmd.25034.
Supplementary Material.
jmd-25034-Supplementary-Material.pdf

Ethics Statement

The study was approved by the institute review board of Ewha Womans University Seoul Hospital (IRB no: 2025-01-027) and written informed consent by the patient was waived due to a retrospective nature of our study

Conflicts of Interest

The authors have no financial conflicts of interest.

Funding Statement

This work was supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (Grant number: RS-2024-00439928).

Acknowledgments

None

Author Contributions

Conceptualization: Jee Hyang Jeong, Ji Young Yun. Data curation: Hyunji Kim, Seo Young Kang. Formal analysis: Hyunji Kim, Seo Young Kang. Funding acquisition: Ji Young Yun. Investigation: Hyunji Kim, Ji Young Yun. Methodology: Hyunji Kim, Seo Young Kang. Project administration: Hyunji Kim, Ji Young Yun. Resources: Jee Hyang Jeong. Software: Seo Young Kang. Supervision: Ji Young Yun, Jee Hyang Jeong. Validation: Hyunji Kim, Ji Young Yun. Visualization: Hyunji Kim, Seo Young Kang. Writing—original draft: Hyunji Kim. Writing—review & editing: all authors.

Figure 1.
Brain imaging. A: DAT PET image showing asymmetrically reduced striatal uptake in the left putamen posterior segment. B: Amyloid PET with axial (a) and coronal (b) images revealed significant binding in the bilateral frontoparietal cortices, which was more prominent on the left image, and the left lateral temporal cortex. C: The amyloid PET SUVR was markedly increased in the left superior frontal, parietal, posterior transverse temporal, thalamic, and ventral diencephalic regions. AI, asymmetry index; DAT, dopamine transporter; PET, positron emission tomography; SUVR, standardized uptake value ratio.
jmd-25034f1.jpg
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      Atypical Imaging Findings in Corticobasal Syndrome: A Case Report
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      Figure 1. Brain imaging. A: DAT PET image showing asymmetrically reduced striatal uptake in the left putamen posterior segment. B: Amyloid PET with axial (a) and coronal (b) images revealed significant binding in the bilateral frontoparietal cortices, which was more prominent on the left image, and the left lateral temporal cortex. C: The amyloid PET SUVR was markedly increased in the left superior frontal, parietal, posterior transverse temporal, thalamic, and ventral diencephalic regions. AI, asymmetry index; DAT, dopamine transporter; PET, positron emission tomography; SUVR, standardized uptake value ratio.

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      Atypical Imaging Findings in Corticobasal Syndrome: A Case Report
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