Imaging Biomarkers in Parkinson Disease?
Imaging Biomarkers in Parkinson Disease?
Editor's Note: While on site at the International Parkinson and Movement Disorder Society 18th International Congress of Parkinson's Disease and Movement Disorders, held in Stockholm, Sweden, June 8-12, 2014, Medscape spoke to Femke Dijkstra, MD, about her study looking at potential imaging biomarkers in Parkinson disease (PD).
Medscape: What was the objective of your study?
Dr. Dijkstra: There is a large research project in Leiden that previously identified 4 specific PD subtypes. As a follow-up, the goal of this new study is to find MRI findings specific for each subtype.
Medscape: Can you briefly review the 4 PD subtypes?
Dr. Dijkstra: Yes. With increasing subtype number, patients are characterized by more severe symptoms of especially the predominantly nondopaminergic features. In short, subtype 1 patients are mildly affected in all domains; subtype 2 is predominantly characterized by severe motor complications; subtype 3 involves impairment mainly in nondopaminergic domains without prominent motor complications; and lastly subtype 4 patients are severely affected on all domains. Patients of subtypes 1 and 2 are younger and have a younger age at onset than those of subtypes 3 and 4.
Medscape: What imaging correlates did you find?
Dr. Dijkstra: The research is ongoing, but in this study we looked at T1-weighted MRI images of the mildest affected subtype and compared them with images of healthy controls. We found atrophy that was most pronounced in the temporal regions including the hippocampus. We then were interested in the location of this hippocampal atrophy, so we did a shape analysis showing that it is most pronounced in the hippocampal body. This differs from the pattern of atrophy found in Alzheimer disease, which is most pronounced in the hippocampal head.
Medscape: So these patients were not showing signs of dementia at the time of the scan?
Dr. Dijkstra: No, they did not have any cognitive complaints, and the atrophy we found did not correlate with their scores on our cognition scale. Apparently, hippocampal differences in PD on MRI are not only associated with PD-related dementia, but they have a broader role in the pathology underlying the disease. The hippocampal body is one of 2 brain areas where adult neurogenesis occurs, and animal and postmortem research has shown that neurogenesis is impaired in PD. This may be an explanation for our findings.
Medscape: Do you think this atrophy contributes to early PD symptoms?
Dr. Dijkstra: We scored patients on a number of clinical items like motor scores, depression, autonomic failure, and cognition, and these symptoms didn't correlate with atrophy. But the patients were mildly affected on all domains, so our next step is to investigate more severely affected patients, and we might find some correlations in that group.
Medscape: What are the potential clinical implications of this work?
Dr. Dijkstra: Many clinicians are looking for practical biomarkers for PD. In combination with other MRI techniques, these findings could contribute to this approach. Even though hippocampus body atrophy may not be associated with symptoms, it could help to identify PD or subtypes within PD.
Editor's Note: While on site at the International Parkinson and Movement Disorder Society 18th International Congress of Parkinson's Disease and Movement Disorders, held in Stockholm, Sweden, June 8-12, 2014, Medscape spoke to Femke Dijkstra, MD, about her study looking at potential imaging biomarkers in Parkinson disease (PD).
Medscape: What was the objective of your study?
Dr. Dijkstra: There is a large research project in Leiden that previously identified 4 specific PD subtypes. As a follow-up, the goal of this new study is to find MRI findings specific for each subtype.
Medscape: Can you briefly review the 4 PD subtypes?
Dr. Dijkstra: Yes. With increasing subtype number, patients are characterized by more severe symptoms of especially the predominantly nondopaminergic features. In short, subtype 1 patients are mildly affected in all domains; subtype 2 is predominantly characterized by severe motor complications; subtype 3 involves impairment mainly in nondopaminergic domains without prominent motor complications; and lastly subtype 4 patients are severely affected on all domains. Patients of subtypes 1 and 2 are younger and have a younger age at onset than those of subtypes 3 and 4.
Medscape: What imaging correlates did you find?
Dr. Dijkstra: The research is ongoing, but in this study we looked at T1-weighted MRI images of the mildest affected subtype and compared them with images of healthy controls. We found atrophy that was most pronounced in the temporal regions including the hippocampus. We then were interested in the location of this hippocampal atrophy, so we did a shape analysis showing that it is most pronounced in the hippocampal body. This differs from the pattern of atrophy found in Alzheimer disease, which is most pronounced in the hippocampal head.
Medscape: So these patients were not showing signs of dementia at the time of the scan?
Dr. Dijkstra: No, they did not have any cognitive complaints, and the atrophy we found did not correlate with their scores on our cognition scale. Apparently, hippocampal differences in PD on MRI are not only associated with PD-related dementia, but they have a broader role in the pathology underlying the disease. The hippocampal body is one of 2 brain areas where adult neurogenesis occurs, and animal and postmortem research has shown that neurogenesis is impaired in PD. This may be an explanation for our findings.
Medscape: Do you think this atrophy contributes to early PD symptoms?
Dr. Dijkstra: We scored patients on a number of clinical items like motor scores, depression, autonomic failure, and cognition, and these symptoms didn't correlate with atrophy. But the patients were mildly affected on all domains, so our next step is to investigate more severely affected patients, and we might find some correlations in that group.
Medscape: What are the potential clinical implications of this work?
Dr. Dijkstra: Many clinicians are looking for practical biomarkers for PD. In combination with other MRI techniques, these findings could contribute to this approach. Even though hippocampus body atrophy may not be associated with symptoms, it could help to identify PD or subtypes within PD.
