DBS may best help Parkinson’s patients with posture and gait issues

Greater nonmotor, life benefits evident in PIGD group than tremor dominant

Joana Vindeirinho, PhD avatar

by Joana Vindeirinho, PhD |

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Deep brain stimulation (DBS) is more effective at easing nonmotor symptoms and improving life quality for people with the postural instability and gait disturbance (PIGD) subtype of Parkinson’s disease than for those with the tremor-dominant (TD) subtype, a study showed.

While previous studies have suggested different effects of DBS on motor function by Parkinson’s subtype, this study provides evidence of the approach’s superior nonmotor and life benefits for PIGD patients.

“These differences of clinical efficacy on non-motor aspects should be considered when advising and monitoring patients with PD [Parkinson’s disease] undergoing DBS,” the researchers wrote.

The study, “Non-motor effects of deep brain stimulation in Parkinson’s disease motor subtypes,” was published in the journal Parkinsonism & Related Disorders.

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Study in 82 postural instability and gait disturbance patients, 33 tremor dominant

Parkinson’s is caused by the progressive loss of nerve cells in the brain that produce dopamine, a major chemical messenger. This leads to the disease’s hallmark motor symptoms, as well as such nonmotor symptoms as cognitive impairments, sleeping problems, fatigue, depression, and anxiety.

Nonmotor symptoms “are a fundamental feature of PD and have been identified as one of the most important predictors of quality of life,” the researchers wrote.

Parkinson’s can be divided into subtypes according to its most prevalent motor symptoms. These include the TD subtype, associated with tremors, and the PIGD subtype, associated with difficulty standing or walking.

Studies have shown that the PIGD subtype is linked to a higher nonmotor symptom burden and worse quality of life than the TD subtype.

DBS, a surgical treatment for advanced Parkinson’s, involves implanting small wires into specific areas of the brain to stimulate those regions with electrical impulses. The wires are connected to a pulse generator, which is powered by a battery. Once implanted, stimulation settings can be adjusted according to the patient’s needs.

While differing effects of DBS on motor symptoms have been reported for PIGD and TD patients, less is known about how DBS affects nonmotor symptoms by disease subtype.

Researchers in Europe hypothesized that PIGD patients, because of their more severe nonmotor symptoms, might benefit more from DBS than those with the TD subtype.

They enrolled 130 Parkinson’s patients who underwent DBS at two study centers in Germany and one in the U.K. between February 2012 and April 2021.

A total of 82 patients had the PIGD subtype, 33 had the TD subtype, and the remaining 15 had a mix of other subtypes. In most patients (95.4%), DBS was applied to the subthalamic nucleus, a small brain region involved in the regulation of motor control and a key area affected by the disease.

Researchers then focused on the PIGD and TD groups, which had similar mean ages (63 vs. 62.1) with women about 30% of both groups.

Changes in nonmotor symptoms, measured by the Non-Motor Symptoms Scale (NMSS), at six months after DBS was the study’s main goal.

NMSS includes nine domains: cardiovascular, sleep/fatigue, mood/apathy, perceptual problems/hallucinations, attention/memory, gastrointestinal symptoms, urinary symptoms, sexual function, and miscellaneous symptoms including items for pain, inability to smell/taste, weight change, and excessive sweating. Higher scores indicate greater symptom burden.

Secondary goals included changes in quality of life, as assessed with the Parkinson’s Disease Questionnaire (PDQ-8) that covers eight areas: mobility, activities of daily living, emotional well-being, stigma, social support, cognition, communication, and bodily discomfort. Higher scores indicate a poorer life quality.

Changes in patients’ ability to perform daily activities, motor symptoms, levodopa equivalent daily dose (LEDD; a sum of all Parkinson’s medications taken), and disease severity also were assessed with validated measures.

Before DBS, the PIGD group had higher total NMSS scores, including poorer scores for urinary symptoms, than the TD group. PIGD patients also had greater difficulties in daily activities, worse motor symptoms, more severe disease, and higher PDQ-8 total scores and those of various domains.

In both groups, DBS led to a significant reduction in the NMSS sleep/fatigue domain score, the PDQ-8 bodily discomfort domain score, motor complications, and LEDD after six months. The only measure showing the surgery’s benefit for the TD group alone was stigma scores in the PDQ-8.

‘Wide range’ of gains in nonmotor and motor symptoms, life quality reported

By contrast, DBS led to significant reductions in total NMSS scores for PIGD patients, as well as gains for the domains of perceptual problems/hallucinations, attention/memory, urinary symptoms, and miscellaneous symptoms — and particularly with smell/taste problems and excessive sweating.

PIGD patients also experienced significant benefits in all motor-related measures, as well as in total PDQ-8 scores and specific areas involving mobility, activities of daily living, cognition, and communication.

“To our knowledge, this is the first study to report an improvement of [non-motor symptom] total burden in PIGD patients and a stable outcome in the tremor-dominant group,” the researchers wrote.

Further analyses showed that changes in NMSS total scores and miscellaneous domain scores — led by changes in the sense of smell or taste — were significantly more favorable for PIGD than TD patients.

Similar findings were obtained for motor complication changes and PDQ-8 domains for activities of daily living and communication. The only change found to be significantly more favorable in the TD group, again, was for stigma, a PDQ-8 domain.

PIGD patients have harsher nonmotor and motor symptoms and a poorer quality of life than TD patients, the researchers noted, and the observed benefits of DBS on these outcomes were greater in the PIGD group than in the TD group.

These patients “experienced an improvement of a wide range of QoL [quality of life], non-motor, and motor aspects” of Parkinson’s after undergoing the surgery, they wrote.

“Based on this observation, we advocate comprehensive assessments of preoperative motor and non-motor symptoms to improve patients’ preoperative [DBS] selection and postoperative monitoring,” the researchers concluded.

The team noted the TD group’s small size and the relatively short follow-up period of six months as study limitations. Larger studies, with a longer follow-up period and more detailed measures, are needed to further explore the long-term improvements in TD and PIGD patients after DBS.