Pauline Anderson

June 06, 2017

VANCOUVER — Spinal cord stimulation (SCS) reduces freezing of gait (FOG) in men with advanced Parkinson's disease (PD), a small new pilot study has shown.

The intervention had a dramatic effect, allowing study patients to walk independently, Mandar Jog, MD, professor, neurology, the University of Western Ontario, London, Canada, and director, London Movement Disorder Center, told Medscape Medical News.

"They were able to get up and walk around without difficulty whereas before the stimulation, some were wheelchair bound."

The research was presented here at the International Congress of Parkinson's Disease and Movement Disorders (MDS) 2017.

Dopaminergic therapy and deep-brain stimulation (DBS) reduce motor symptoms in PD, but their effects on gait dysfunction lessen as the disease progresses.

Epidural SCS may be a new therapeutic approach for levodopa-resistant motor symptoms in PD, said Dr Jog.

The study included five male patients, mean age 71 years, who had been diagnosed with PD for a mean of 14 years. These patients had significant gait disturbances, FOG, and postural instability.

The men were not eligible for DBS because, even while receiving high doses of levodopa, they still had gait issues.

"One of the criteria for DBS is response to levodopa," said Dr Jog. "On the maximum, or what one would call optimized, levodopa, these patients still couldn't walk."

The men underwent midthoracic SCS. This involved placing electrodes on either side of the spinal cord.

"It's a dorsal epidural implant, which means it doesn't actually penetrate or puncture anything; it's just sitting on top of the dura," explained Dr Jog.

At eight study visits over 6 months, researchers tested a range of SCS settings at 200 to 500 microseconds and 30 to 130 Hz at supra-threshold intensity.

Investigators measured dynamic gait characteristics, including step length, stride width, stride velocity, stance, and swing time. They also analyzed timed sit-to-stand and automated FOG detection by using foot pressures.

Questionnaires completed at each visit included the FOG questionnaire, Unified Parkinson's Disease Rating Scale (UPDRS) motor items, activities-specific balance confidence (ABC) scale, and the 8-item Parkinson's disease questionnaire. 

Best Combination

In three patients, the best SCS setting combination was 300 microseconds and 60 Hz. That combination led to a mean improvement of 63.8% in timed sit-to-stand, a mean improvement of 76.2% in stride velocity, and a mean improvement of 91.1% in step length.

For two patients, a combination of 130 Hz with 200 or 300 microseconds was most beneficial, with a mean improvement of 58.4% for timed sit-to-stand, 36.6% for stride velocity, and 56.7% for step length.

At 6 months after implantation, the mean UPDRS motor score improved by 39.4%. There were a 26.8% improvement on the FOG questionnaire and a 116.9% improvement in the ABC score.

The mean number of FOG episodes was reduced significantly from 16 before surgery to 0 at 6 months while patients were "on" levodopa and off stimulation.

Dr Jog described one patient, who had been largely homebound for 6 years. After the stimulation, this patient went on a trip to the East coast.

"His wife was literally crying when she told us he went from their cottage and walked up and down the beach, on his own."

There were no side effects of the stimulation "at all," said Dr Jog.

It's not clear how the stimulation improves gait. The "best theory," said Dr Jog, is that it's "turning up the volume" on directions the spinal cord gives to systems in the brain involved in walking and these systems respond in a similar "loud" or exaggerated fashion.

Although the poster provided data to 6 months, the researchers now have data out to 9 months. Dr Jog reported that the patients "are still doing well."

The London team aims to eventually implant 25 patients with PD and is already getting additional referrals. They also plan to investigate the neurophysiologic changes occurring at different SCS parameters in a larger clinical study.

They would also like to implant patients with progressive supranuclear palsy (PSP). However, Dr Jog pointed out that unlike patients with PD, who fall because of their gait issues, those with PSP tend to fall because of their spontaneous postural instability.

"I'm not sure we will be able to improve the falls" in these patients, he said.

Dr Jog foresees that patients will eventually program the system at home. The idea is that they would get a variety of settings already programmed and a sensor would indicate whether the system is working optimally and, if not, "tell them to switch to the next setting," he said.

"So over a period of a few days or maybe a week or two at home, they will program it so they don't even have to come to the lab."

The intervention might benefit the substantial number of patients with PD who aren't candidates for DBS because of their lack of response to levodopa, said Dr Jog.

"Gait is not something that responds very well to levodopa to begin with, and if a patient is not responding to the maximum dose, we don't have any other choice."

Interesting Concept

Asked to comment, Joachim Krauss, MD, director, Department of Neurosurgery, Hanover Medical School, Germany, said SCS "is a very interesting concept" for patients with PD, especially if it's shown to have consistent benefits.

Pedunculopontine nucleus stimulation works well in some patients with PD but not in others, so it's no longer widely used, said Dr Krauss.

"SCS might be a great alternative for patients with freezing of gait."

Dr Krauss added that SCS is easier to perform than pedunculopontine nucleus stimulation and might be a more acceptable option for patients.

The authors have disclosed no relevant financial relationships.

International Congress of Parkinson's Disease and Movement Disorders (MDS) 2017. Poster 344. Presented June 5, 2017.

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