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Early Involvement of Caudate Brain Region Linked to Worse Prognosis in Parkinson’s Patients, Study Finds

caudate involvement

Almost half of people in the early stages of Parkinson’s disease already have signs of neurodegeneration in a brain region called the caudate, which was previously thought to affect mostly those at advanced disease stages, a study reports.

Early caudate involvement on both sides of the brain, as seen by DaTscan imaging of the brain, appeared to predict the risk for worse outcomes, including cognitive impairment, depression, and gait problems, over a four-year follow-up period.

These findings suggest that caudate involvement detected through DaTscan neuroimaging may serve as an early biomarker to identify patients at a greater risk of faster disease progression in the near future.

The study, “Clinical implications of early caudate dysfunction in Parkinson’s disease,” was published in the Journal of Neurology, Neurosurgery & Psychiatry.

Parkinson’s disease is believed to be caused by the impairment or death of dopamine-producing nerve cells (neurons) in a region of the brain called the substantia nigra, which controls the body’s balance and movement.

When the disease is established, or advanced, the degeneration of dopaminergic neurons and nerve fibers frequently extends to a brain region called the caudate nucleus. This region plays important roles in motor control as well as in various other non-motor tasks, such as learning and sleep.

In fact, the loss of dopaminergic function in this region is known to contribute to the hallmark symptoms of Parkinson’s including cognitive impairment, depression, sleep disorders, and gait problems.

Although less common, caudate dopaminergic dysfunction may also emerge in the early stages of the disease, in which case it could also contribute to the onset of non-motor symptoms. However, the frequency of this specific brain impairment in early Parkinson’s is unknown as are its clinical implications for patients.

To address this lack of knowledge, a team, led by researchers at the University of Milan in Italy and Newcastle University in England, investigated the prevalence of caudate dopaminergic dysfunction in people who were still in the very early stages of Parkinson’s.

By comparing the participants’ state at the beginning of the study and four years later, they also looked for associations between caudate involvement and an increased risk of disease progression.

They analyzed clinical data from 397 patients who had had a Parkinson’s diagnosis for two years or less, and were participating in the Parkinson’s Progression Markers Initiative (PPMI), an ongoing study attempting to identify biomarkers of disease progression. The team compared the collected clinical data from Parkinson’s patients with that of 177 healthy volunteers.

Caudate dysfunction was detected using 123I-FP-CIT single-photon emission computed tomography, commonly known as DaTscan. This is an imaging technique that depicts the levels of dopamine transporters in the brain that is often used to confirm a Parkinson’s diagnosis.

Based on DaTscan imaging data, the participants were divided into three groups: those who had no reduction of dopamine transporters, those who showed reduction in just one side of the brain, and those who had involvement of both sides of the brain.

Initial data showed that 51.6% of the patients had signs of normal caudate dopamine function, while 26% had caudate dopaminergic dysfunction on one side of the brain (unilateral), and 22.4% on both sides (bilateral).

Four years later, the patients who initially had bilateral caudate involvement were found to experience more frequent and worse cognitive impairment and depression, and more severe gait disability.

In general, after four years of follow-up, more patients showed a loss of dopaminergic nerve fibers in the caudate, compared with the study start, affecting 83.9% of patients (unilateral 22.5%, bilateral 61.4%).

“In this study, we have demonstrated a high frequency of early caudate dopaminergic dysfunction in patients with recently diagnosed [Parkinson’s disease],” the researchers wrote.

“Our study suggests that early bilateral caudate dopaminergic dysfunction is associated with an increased frequency of clinically significant depression and to worse depressive symptoms, regardless of age,” they added.

DaTscan parameters used to define the presence of early caudate dysfunction may be a “valid indicator of more rapid onset of such symptoms,” they said, which may help in “identifying patients at risk of clinical progression to cognitive impairment, depression, and gait problems in the near future.”

Assessment of caudate dopaminergic denervation may also assist clinicians in better predicting disease course at an early stage and identifying patients who may benefit the most from early, targeted disease-modifying therapies.

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Changes in Neuronal Communication Linked to Falls and Freezing of Gait in Parkinson’s, Study Finds

neuronal communication changes, Parkinson's motor symptoms

Parkinson’s disease-related falls and freezing of gait — when patients are unable to move their feet forward when trying to walk — are associated with changes in a specific type of neuronal communication in different brain regions, a study reports.

The study, “Cholinergic system changes of falls and freezing of gait in Parkinson disease,” was published in Annals of Neurology.

Many people with Parkinson’s disease will experience falling and freezing of gait, which tend to become more frequent as the disease progresses. In some cases, symptoms cannot be controlled with dopaminergic therapy, suggesting that non-dopamine mechanisms contribute to Parkinson’s disease motor symptoms.

Previous studies have shown that the brainstem (region that connects the brain to the spinal cord) and basal forebrain (important in the production of acetylcholine) regions with degenerated acetylcholine-releasing neurons projecting to the thalamus and cerebral cortex are associated with falls and slow gait speed in Parkinson’s patients.

Acetylcholine is a brain chemical (neurotransmitter) released by nerve cells to send signals to other cells (neurons, muscles, and glands). The thalamus is involved in several important processes, including consciousness, sleep, and sensory interpretation; the cerebral cortex plays a key role in memory, attention, perception, awareness, thought, language, and consciousness.

Scientists have also observed reduced dopaminergic nerve terminals in the striatum, reduced cholinergic (meaning “acetylcholine-releasing”) nerve terminals in the cortex, and more severe beta-amyloid accumulation in Parkinson’s disease “freezers” compared with “non-freezers.”

The striatum coordinates multiple aspects of cognition, including both motor and action planning; the cholinergic system contains nerve cells that use acetylcholine to propagate a nerve impulse, and has been associated with a number of cognitive functions, including memory, selective attention, and emotional processing.

University of Michigan researchers hypothesized that distinct patterns of cholinergic projection system changes in the brain are associated with freezing of gait and falls in Parkinson’s patients.

The team examined and performed [18F]FEOBV positron emission tomography (PET) scans on 94 Parkinson’s patients (72 men and 22 women) with a history of falling and “freezing.” Most subjects were taking dopamine agonists, carbidopa-levodopa or combinations of both.

[18F]FEOBV is a radioactive marker that selectively binds to the vesicular acetylcholine transporter (VACht) that loads acetylcholine into synaptic vesicles — sac-like structures in neurons that store chemical messengers before releasing them into the gap between nerve cells (synapse), enabling neuronal communication.

A PET scan is a non-invasive imaging technique to visualize metabolic processes in the body. Before the scan, [18F]FEOBV is administered via injection; doctors wait for the radiotracer to be distributed throughout the body, and then scan the patient to detect and quantify the patterns of its accumulation in the body.

Because the marker binds to VACht, scientists use it to quantify active cholinergic nerve terminals in the brain.

“Participants were asked about a history of falling. A fall was defined as an unexpected event during which a person falls to the ground. The presence or absence of (freezing of gait) was based on clinical examination and directly observed by the clinician examiner,” according to The Movement-Disorder Society Sponsored-Unified Parkinson’s Disease Rating Scale (MDSUPDRS), the researchers wrote.

They reported that 35 participants (37.2%) had a history of falls, and 15 (16%) had observed freezing of gait.

Compared with non-fallers, fallers had a significant decrease in VACht expression within the right thalamus, specifically in the lateral geniculate nucleus, which is the primary center for processing visual information. This suggests that the visual information processing required for walking around safely might be compromised in Parkinson’s patients with a history of falling.

On the other hand, patients with freezing of gait had significantly reduced VACht expression in the bilateral striatum and hippocampus — required for learning and memory — compared with non-freezers.

The team found that a history of falls was associated with cholinergic projection system changes that relay to the thalamus, while the neural signals behind freezing of gait transmit to the caudate nucleus — a brain region associated with motor processing.

They also found that Parkinson’s fallers had a lower density of thalamic cholinergic nerve terminals compared with non-fallers.

Freezing of gait was related to longer disease duration, more severe parkinsonian motor ratings, and higher levodopa levels.

These results suggest that changes in acetylcholine-mediated neuronal communication are linked to falls or freezing behavior, depending on the affected brain region.

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