Parkinson and other neurodegenerative diseases are hard to distinguish. Surface-based MRI shows promise as a diagnostic tool.
Patients with clinically established progressive supranuclear palsy (PSP) exhibit distinct patterns of cortical atrophy, particularly affecting the frontal lobe, according to researchers in London.
The researchers compared brain surface-based MRI in 3 neurodegenerative diseases: PSP, multiple system atrophy (MSA), and Parkinson disease (PD). Although these are distinct conditions, they can be hard to tell apart, especially in the early stages.
The disorders have different symptoms and damage to different brain regions. MSA has some clinical symptoms of PD, but it targets more brain areas, including those that control autonomic function, such as the brainstem and spinal cord, and those controlling movement, such as the basal ganglia and cerebellum. PD is characterized by gradual death of the substantia nigra dopamine cells specifically, causing slow movement, rigidity, and trouble starting and stopping movements.
Similar to PD, PSP causes problems with movement and balance and damage to the brainstem, including the substantia nigra, but damage to more brainstem regions also occurs. There are subtle differences between the movement problems found in PD and PSP, although they may initially appear to be the same. For example, vision, speech, and swallowing are more severely affected in PSP and PD causes more problems with stiffness.
Even neurologists can have a hard time distinguishing these diseases in the clinic.
That’s where surface-based MRI-which measures the shape and thickness of brain structures-might help. Lead author Amanda Worker at King’s College London, Institute of Psychiatry, and colleagues, used MRI to study brain images from 14 patients with PD, 18 with MSA, and 14 with PSP, as well as 19 healthy controls who had no neurological condition. They compared measurements of disease severity and duration with brain changes in each group.
The investigators found that PSP in particular has a distinct pattern of brain changes. They measured thinning of the cerebral cortex, as well as loss of volume within the frontal lobe, particularly in the superior frontal gyrus. The patients with PD or MSA did not have significant changes in the cerebral cortex. Also, the patients with PSP had increased surface area in a region of the occipital lobe-the left pericalcarine-compared with the MSA group.
“These findings support the hypothesis that PSP patients display more clinically severe symptoms as well as differential and more established patterns of cortical atrophy that particularly affects the frontal lobe,” the investigators concluded.
Lead author Amanda Worker conveyed to Neurology Times, “I think that it is difficult to say whether this could be used as a diagnostic tool just yet, as the results seen in this study are at a group level-in order to be useful in a clinical setting the changes to the cortex need to be robust enough to be seen at an individual patient level. This is something that we haven't yet looked at and it would be interesting to see, especially in PSP patients.”
According to the study authors, this was the first study to investigate cortical thickness and surface area in MSA and the first to compare brain surface characteristics among the 3 neurodegenerative disorders.
Although the present study distinguished MRI patterns in PSP and compared them with MSA and PD, the investigators did not report defining characteristics to distinguish PD compared with MSA. Worker told Neurology Times, “We did not see any differences in cortical thickness between the MSA and PD groups in this study. We did, however, find differences between these two groups in another paper where we looked at white matter microstructural properties, which might be a more useful avenue for exploring these particular diseases.”
Future studies may focus on the further identification of distinct MRI patterns-whether surface-based or using other techniques-to distinguish all of these neurological conditions, which present with similar clinical symptoms. Worker remarked on ongoing directions for this research group: “We are currently looking at combining different measures from different tissue types in order to help distinguish the three diseases based on changes seen in the grey and white matter.”
The study appeared in PLoS One.1
• MSA, PD, and PSP are hard to tell apart, and more distinct clinical measurements for these diseases are needed.
• Surface-based MRI distinguished PSP from MSA and PD.
• PSP is specifically characterized by changes in the frontal lobe.
1. Worker A, Blain C, Jarosz J, et al. Cortical thickness, surface area and volume measures in Parkinson’s disease, multiple system atrophy and progressive supranuclear palsy. PLoS One. 2014;9:e114167. doi: 10.1371/journal.pone.0114167.