Hand Movement Triggers Eyeblinks in Parkinson’s Patient

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by Steve Bryson, PhD |

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Hand movements induced eyeblinks in a 70-year-old man with Parkinson’s disease, a case study reported for the first time.

Although more studies are necessary, researchers suggest that eyeblink bursts induced by hand movements may be regarded as a potential hallmark of Parkinson’s disease.

The case study, “Hand Movement-Induced Eyeblink Bursts in a Patient With Parkinson’s Disease,” was published in the Journal of Movement Disorders.

Impairment of eyeblinks is a characteristic motor symptom of Parkinson’s disease. Studies suggest a link between the level of dopamine in the brain, which is abnormally low in Parkinson’s, and the rate at which a person spontaneously blinks.

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Blink reflexes, which originate in the brain stem, typically are evoked by stimulation of the cornea, the transparent outer layer at the front of the eye, as well as sound and visual stimulation or movement of the limbs.

In this report, researchers at the Nagoya City University West Medical Center in Japan described the case of eyeblink bursts that were induced by hand movements in a Parkinson’s patient.

The 70-year-old patient had bradykinesia, or slow movements, in both legs and the left hand, with resting tremor in the left toes, mild rigidity in both legs. He had shown some benefits from taking the medication levodopa, which increases dopamine levels. As a result, he was diagnosed with probable Parkinson’s.

He also had a three-year history of freezing of gait, walking with short steps, a tendency to speed up when performing repetitive movements (festination), and frequent falls.

During an examination, when he wasn’t taking levodopa, the patient was asked to perform hand movements, including opening and closing his hands, finger tapping with the index finger and thumb, and flipping the hand.

When looking at these hand movements, the bursts of eyeblinks occurred immediately . However, no eye blink occurred when the examiner tapped his finger.

Neurological examinations were performed again when the patient was on his medication, and gazing at the finger-tapping movement induced eyeblink bursts similar to when he was not on levodopa. When he avoided eye contact with the hand movements, blinking occurred when opening and closing his hand or flipping the hand.

An MRI of his brain showed no abnormalities, including no substantial shrinkage in the midbrain, where the cells that generate dopamine are lost in people with Parkinson’s.

“To the best of our knowledge, this unusual phenomenon has not been described in the previous literature,” the research team wrote. “Considering that hand movement was presumed to always be included in the patient’s visual field (central or peripheral), eyeblink bursts might occur as a protective response from repetitive hand movements.”

“This is the first study to reveal that eyeblink bursts can be induced by visual perception of repetitive hand movement,” the researchers stated.