Troubleshooting Gait Problems in Parkinson’s Disease Patients with Subthalamic Nucleus Deep Brain Stimulation

THE CLINICAL DILEMMA

Subthalamic nucleus deep brain stimulation (STN DBS) is a recognized therapy that improves motor fluctuations, dyskinesia, and quality of life in appropriately selected patients with Parkinson’s disease (PD). The success of DBS therapy does not rely solely on the surgery itself but depends upon the entire process, encompassing pre-operative patient selection, patient-specific surgical treatment to minimize risk and maximize benefit, and post-operative management, including optimal DBS programming. The adjustment of stimulation parameters in DBS is typically guided by the assessment of patients’ rigidity (mainly in the upper limbs) followed by tremor evaluation, which has more variable responses [1]. Although these clinical parameters remain relatively stable over time [2], progressive worsening of axial symptoms including gait and balance commonly diminish motor function and quality of life. Thus, rigidity and tremor are less helpful to guide long-term DBS adjustments [2].

Although gait and balance impairments are similarly influenced by levodopa and STN DBS, post-surgical outcomes are strongly influenced by variables such as lead location, stimulation parameters, medical management, and disease progression. Basically, four main scenarios of gait/balance disorder can be observed after STN DBS: 1) impairment of ambulation secondary to a lesion-associated effect of the electrode implantation, which can be transient or permanent; 2) stimulation-induced adverse effects due to spreading of current into surrounding structures such as the internal capsule; 3) levodopa-responsive gait impairments, for which increases in medication and stimulation energy are expected to help, but troublesome dyskinesia might be therapy limiting; and 4) gait problems resistant to dopaminergic medication and classical neurostimulation strategies. The latter are commonly due to PD progression, but can sometimes be ameliorated with advanced DBS programming strategies discussed below.

Many patients report improvements in their overall parkinsonism after gait is ameliorated as gait function is an excellent mirror of a patient’s global mobility. In view of that finding, we have been adjusting DBS in our outpatient clinic based on gait analysis, especially during long-term follow-up. Here, we describe a practical strategy for troubleshooting gait problems in PD DBS patients by revising stimulation parameters through “hands-on” programming, which can be useful for improving patient outcomes in clinical practice.

THE ROADMAP

Step 1. Observe the problem

Pragmatically, the first step is to watch the patients rise from a chair and walk through a straight corridor at a comfortable pace (Fig. 1). The walking speed, step symmetry, signs of dyskinesia or dystonia, and signs of freezing of gait (FoG) should be evaluated.

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Fig. 1

Observe the patient’s gait.

Step 2. Mind the gap: the internal capsule.

Sometimes the spread of current into the internal capsule is not obvious and can lead to gait impairment and falls after long-term STN DBS [1]. We recommend turning off the stimulation and re-evaluating the patient’s gait. If ambulation improves with stimulation off, each electrode should be turned on separately to identify the “guilty” one, then the stimulation parameters on that side (Video, segment 1) should be reduced to diminish the stimulation induced adverse effect. If deactivation of DBS does not improve ambulation, especially in cases where gait and balance impairment occurs immediately after DBS implantation, a lesional effect of the surgical procedure is likely responsible. Such lesional effects commonly improve with time but may recover incompletely and produce permanent adverse effects on ambulation.

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Flowchart.

an algorithm for programming subthalamic nucleus deep brain stimulation based on gait analysis. ^*LEDD: dopaminergic equivalent daily dose. ^**Stimulate subthalamic nucleus (STN) and substantia nigra (SN): use the best contact to improve cardinal symptoms plus a ventral contact. In order to achieve this, use double monopolar stimulation, interleaving, or multiple independent current delivery at different levels (depending upon device capabilities).

DISCUSSION

The art of optimizing DBS parameters in PD can be challenging and time-consuming [6, 8]. Particularly in the long-term, cardinal symptoms such as rigidity and tremor may become less useful in guiding DBS programming, and gait analysis can play a more meaningful role in DBS optimization. Herein, we propose a stepwise approach that employs gait evaluation as a tool that can serve as a potentially useful adjunct to traditional STN DBS programming (see Flowchart). This conceptual model harkens back to Charcot’s teachings, which emphasize the utility of clinical observation as a powerful “weapon” in neurology. In keeping with this theme, while carefully performing the aforementioned steps, the clinician should be perceptive of patient-specific DBS tendencies that can be useful when fine-tuning stimulation parameters. For example, if a patient responds positively to a pulse-width increase and not to amplitude elevation, then further adjustments should take this tendency into account. It is also important to train the patient and caregiver to use of the DBS patient controller, which can be useful in determining individual patient tendencies and in making optimal, patient-tailored DBS parameter adjustments.

CONCLUSION

Gait impairment is a very common mid- to long-term complaint in patients with Parkinson’s disease after STN DBS. A systematic approach that includes programming strategies based on gait analysis can maximize patients’ global motor benefits and enhance quality of life.