Changes in the visual systems of newly diagnosed Parkinson’s disease patients may provide important biomarkers for the early detection and monitoring of the disease, according to a new study published online in the journal Radiology.
“Just as the eye is a window into the body, the visual system is a window into brain disorders,” said lead researcher Alessandro Arrigo, M.D., a resident in ophthalmology at the University Vita-Salute San Raffaele of Milan, Italy.
Parkinson’s disease is a neurodegenerative condition caused by neuronal loss in several brain structures. Parkinson’s disease is characterized by tremors, rigidity or stiffness throughout the body, and impaired balance and coordination.
“Although Parkinson’s disease is primarily considered a motor disorder, several studies have shown non-motor symptoms are common across all stages of the disease,” Dr. Arrigo said. “However, these symptoms are often undiagnosed because patients are unaware of the link to the disease and, as a result, they may be under-treated.”
Non-motor symptoms experienced by patients with Parkinson’s disease include visual alterations such as an inability to perceive colors, a change in visual acuity, and a decrease in blinking which can lead to dry eye.
“These non-motor Parkinson’s symptoms may precede the appearance of motor signs by more than a decade,” Dr. Arrigo said.
The study of 20 newly diagnosed and not yet treated patients (11 men, 9 women) with Parkinson’s disease and 20 age- and gender-matched healthy controls involved a multi-disciplinary team of researchers in ophthalmology, neurology and neuroradiology of the University of Messina, Italy. MRI was performed on both the healthy controls and the patients, who underwent imaging within four weeks of their diagnosis. Researchers used an MRI technique called diffusion weighted imaging to assess white matter changes and voxel-based morphometry (VBM) to investigate concentration changes of brain’s gray and white matter. All study participants also had ophthalmologic examinations.
The researchers found significant abnormalities within the visual system brain structures of Parkinson’s disease patients, including alterations of optic radiations, a reduction of white matter concentration and a reduction of optic chiasm volume. The optic chiasm is the part of the brain where the left and right optic nerves intersect.
“The study in depth of visual symptoms may provide sensitive markers of Parkinson’s disease,” Dr. Arrigo said. “Visual processing metrics may prove helpful in differentiating Parkinsonism disorders, following disease progression, and monitoring patient response to drug treatment.”
Dr. Arrigo added that future studies are needed to better understand the timing of degeneration along visual pathways, as well as the specific changes.
“We’re excited by our findings,” he said. “However, this is just a starting point.”
Source: Queen Muse – RSNA
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Original Research: Full open access research for “Visual System Involvement in Patients with Newly Diagnosed Parkinson Disease” by Alessandro Arrigo, Alessandro Calamuneri, Demetrio Milardi, Enricomaria Mormina, Laura Rania, Elisa Postorino, Silvia Marino, Giuseppe Di Lorenzo, Giuseppe Pio Anastasi, Maria Felice Ghilardi, Pasquale Aragona, Angelo Quartarone, and Michele Gaeta in Radiology. Published online July 11 2017 doi:10.1148/radiol.2017161732
Visual System Involvement in Patients with Newly Diagnosed Parkinson Disease
Parkinson disease (PD) is a common neurodegenerative disease caused by dopaminergic neuronal loss in several brain structures, primarily in the substantia nigra. Although PD primarily is considered a motor disorder, results of several studies have shown that nonmotor symptoms are common throughout all stages of the disease. These symptoms are often undiagnosed because patients are embarrassed by them or unaware of their link to PD, and consequently, they may be undertreated.
Nonmotor symptoms encompass olfactory deficits, visual alterations, apathy, depression, pain, sexual difficulties, bowel incontinence, and sleep disorders. They usually precede the appearance of motor signs by more than a decade, in keeping with the progression of Lewy abnormalities. Although many patients with PD do not report visual problems, the disease can be associated with visual symptoms and signs that occur at different neural levels, including loss of visual acuity, difficulty with discrimination of contrast, alteration of color perception, impairment in visual skills in performing visual-spatial tasks, and difficulty in discriminating orientation and motion. In addition, eye movements and latency times of blinking and pupillary reflexes might be altered.
Retinal dysfunction might be partially responsible for some of the visual dysfunctions, because (a) retinal levels of dopamine are decreased in both patients with PD and in animal models of PD with visual electrophysiologic abnormalities that are similar to those reported in patients with PD and (b) electroretinographic abnormalities are present in both patients with and animal models of PD. In keeping with this interpretation, acute administration of levodopa induces recovery of the electrophysiologic abnormalities in both patients with and animal models of PD and relieves symptoms of visual blurring in patients. On the other hand, deficits at the cortical level might contribute to visual dysfunction, because results of studies have shown reduced metabolism and hypoperfusion in the occipital cortex of patients with PD. Moreover, authors of previous magnetic resonance (MR) imaging studies who used in vivo neuroanatomic quantitative approaches have reported significant focal reductions in cortical thickness of the occipital cortex in intermediate to advanced stages of the disease. Hence, the pathophysiologic basis of visual dysfunction in patients with PD requires further definition. On the basis of the existing literature, we hypothesized the presence of wide abnormalities in visual system pathways and related structures in patients with PD. The main aim of our study was to investigate the intracranial visual system in drug-naïve patients with newly diagnosed PD.
“Visual System Involvement in Patients with Newly Diagnosed Parkinson Disease” by Alessandro Arrigo, Alessandro Calamuneri, Demetrio Milardi, Enricomaria Mormina, Laura Rania, Elisa Postorino, Silvia Marino, Giuseppe Di Lorenzo, Giuseppe Pio Anastasi, Maria Felice Ghilardi, Pasquale Aragona, Angelo Quartarone, and Michele Gaeta in Radiology. Published online July 11 2017 doi:10.1148/radiol.2017161732