Eye test can distinguish Parkinson’s from secondary parkinsonism
Patients with Parkinson's had a lower density of nerve fibers: Study
Imaging of nerves in the eyes may be used to differentiate between Parkinson’s disease and secondary forms of parkinsonism, a new study shows.
The study, “Corneal confocal microscopy differentiates patients with secondary parkinsonism from idiopathic Parkinson’s disease,” was published in NPJ Parkinson’s Disease.
Parkinson’s can cause abnormalities in nerves connecting eyes and brain
Parkinson’s disease is a neurodegenerative disorder caused by the dysfunction and death of brain cells that are responsible for making the chemical messenger dopamine. Parkinson’s is marked by motor symptoms such as slowed movement, tremor, stiffness, and balance issues. Most people with Parkinson’s have idiopathic disease, meaning the underlying cause is not known.
Secondary parkinsonism refers to health conditions that can cause Parkinson’s-like motor symptoms, but are not actually Parkinson’s disease. Secondary parkinsonism can develop due to drugs or toxins, or because of problems with blood flow or fluid pressure in and around the brain. Since secondary parkinsonism is by definition characterized by symptoms that are similar to Parkinson’s disease, it can be difficult for clinicians to tell the two apart.
Parkinson’s disease can cause abnormalities in the nerves that connect the eyes to the brain, which are generally less affected in secondary parkinsonism. These nerves can be visualized using a technique called corneal confocal microscopy, or CCM. In this study, scientists in China tested whether CCM might be used to reliably distinguish between true Parkinson’s disease and secondary parkinsonism.
CCM may have clinical utility as a rapid ophthalmic neuroimaging method for distinguishing patients with [secondary parkinsonism] from [Parkinson’s disease].
The study included 45 people with idiopathic Parkinson’s disease and 25 with secondary parkinsonism. The researchers found patients with Parkinson’s had a lower density of nerve fibers detected by CCM than those with secondary parkinsonism. They also tended to have more branch-like protrusions on their nerves than those with secondary parkinsonism.
To test if these CCM-based measures could distinguish between the two conditions, the researchers calculated a statistical value called the area under the receiver operating characteristic curve (AUC). This is a statistical test of how well a measure (in this case, CCM) can distinguish between two groups, Parkinson’s or secondary parkinsonism in this study. AUC values can range from 0.5 to 1, with higher numbers reflecting better accuracy.
The AUC for CCM in this study was 0.924, suggesting high accuracy for distinguishing true Parkinson’s from secondary parkinsonism. The researchers noted they could get even better accuracy if they also included clinical measures like assessments of symptom severity.
“CCM may have clinical utility as a rapid ophthalmic neuroimaging method for distinguishing patients with [secondary parkinsonism] from [Parkinson’s disease],” the scientists concluded.
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