A new Israeli study comparing the handwriting of healthy people to those with Parkinson’s disease (PD) holds out the promise of providing a simple diagnostic tool at the earliest stages of the progressive disorder caused by the death of nerve cells in the brain’s muscle-movement control areas.
As many as 10 million people worldwide suffer the tremors, impaired balance and rigidity associated with PD, which has no cure. The handwriting study is the latest in many Israeli investigations into causes, diagnosis and treatment for PD.
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Unfortunately, physicians can diagnose PD definitively only by observing clinical symptoms that appear at a relatively advanced stage, or by administering a test called SPECT, which uses radioactive material to image the brain.
But researchers at the University of Haifa and Rambam Medical Center in Haifa believe their study shows how the disease can be detected sooner, noninvasively and without radiation.
“Identifying the changes in handwriting could lead to an early diagnosis of the illness and neurological intervention at a critical moment,” explained Prof. Sara Rosenblum of the university’s department of occupational therapy.
She reported that publication of results in the journal of the European Neurological Society aroused great interest at the International Congress of Parkinson’s Disease and Movement held last summer in Sydney, Australia.
Rosenblum initiated the study, which compared handwriting samples from 40 PD and disease-free subjects.
She was building on previous research that has shown unique and distinctive differences between the handwriting of PD patients and that of healthy people. However, most of those studies focused on motor skills (drawing spirals, for instance) and not on writing that involves cognitive abilities, such as signing a check or copying addresses.
According to Rosenblum, PD patients notice a change in their cognitive abilities even before they experience a change in their motor abilities.
Her handwriting research was conducted in cooperation with Dr. Ilana Schlesinger, head of the Center for Movement Disorders and Parkinson’s Disease at Rambam, and occupational therapists at the hospital.
Half of the 40 participants were known to be in the early stages of Parkinson’s disease, before obvious motor signs are visible. The subjects were instructed to write their names and to copy addresses — two everyday tasks that require cognitive abilities.
The writing was done on a regular piece of paper placed on an electronic tablet, using a special pen with pressure-sensitive sensors. A computerized analysis of the results compared writing form (length, width and height of the letters), time required, and the pressure exerted on the surface while performing the assignment.
There were significant differences between the PD patients and the healthy group, and all subjects, except one, had their status correctly diagnosed (97.5% accuracy).
More air time
The Parkinson’s disease patients wrote their letters smaller, exerted less pressure on the writing surface and took more time to complete the task.
Rosenblum said the most striking difference was the length of time the pen was in the air between the writing of each letter and each word.
“This finding is particularly important because while the patient holds the pen in the air, his mind is planning his next action in the writing process, and the need for more time reflects the subject’s reduced cognitive ability. Changes in handwriting can occur years before a clinical diagnosis and therefore can be an early signal of the approaching disease,” she said.
Validating these findings in a broader study could pave the way for this method to be used for a preliminary diagnosis of the disease in a safe and non-invasive fashion. “This study is a breakthrough toward an objective diagnosis of the disease,” said Schlesinger, noting that this method would reduce the load on the health system, because the test can be performed by a professional other than a doctor.
The researchers are currently applying the same method in a new experiment, using handwriting analysis to evaluate the degree of functional improvement in PD patients who have received brain-implanted pacemakers.