Deep Brain Stimulation in Parkinson’s Disease: Assessing Efficacy

Figures & data

Table 1 Unified Parkinson’s Disease Rating Scale (UPDRS) and Movement Disorders Society Revision of UPDRS (MDS-UPDRS)

Subscale	Assessment Made (UPDRS)^Citation15–Citation18	Assessment Made MDS-UPDRS^Citation19,Citation69	Method of Assessing
I	Mentation, behavior, and mood	Non-motor Experiences of Daily Living	Data elicited from patient or caregiver; Reliability depends on patient/caregiver reporting and examiner’s ability to elicit response.
II	Activities of daily living	Motor Experiences of Daily Living	Data elicited from patient or caregiver; Training tapes are available to improve reliability of measures
III	Clinician rated motor manifestations	Motor Examination	Examination based; Training tapes are available to improve reliability of measures
IV	Complications of therapy	Motor Complications	Data elicited from patient or caregiver; Reliability depends on patient/caregiver reporting and examiner’s ability to elicit response.
Final scoring	Five response options: 0 = normal, 1 = slight, 2 = mild, 3 = moderate, and 4 = severe		UPDRS: not an interval scale, not quantifiable; a score of 4 is not twice as severe as score of 2. MDS-UPDRS: scores have uniform anchors

Table 2 DBS Benefits on Different Targets

Target	Effect	Benefit of DBS (Conventional DBS Unless Specified)
Established targets
Subthalamic nucleus (STN) and local fiber pathways	Suppress cardinal PD symptoms like bradykinesia, rigidity and tremor^Citation9	MDS-UPDRS improvement in both motor and non-motor symptoms 6 months after onset of stimulation^Citation20 Part I: improved by 3.1 points Part II: improved by 5.3 point Part III: improved by 13.1 points Part IV: improved by 7.1 points UPDRS improvement in score from “preoperative “off” medication to the one-year follow-up of the “off” medication “on” stimulation score”^Citation31 UPDRS: I: Improvement was not statistically significant II scores improved by 73.8%. III: significant improvement seen tremor, rigidity, bradykinesia and axial score (P<0.001 for all) IV: dyskinesia and motor fluctuations reduced by 65.1% and 48.6%, respectively UPDRS improvement in score from “the preoperative “on” medication motor subscore to the one-year follow-up “on” medication “on” stimulation score”^Citation31 UPDRS III: significant improvement seen tremor (P=0.002), rigidity (P<0.001), bradykinesia (P=0.002), and axial score (P=0.046) Baseline UPDRS motor off-medication scores improve by 30-67%^Citation27,Citation39,Citation70 ADLs improve by 6-56%^Citation40,Citation71
Internal globus pallidus (GPi)	Strong antidyskinesia effect; Suppress cardinal PD symptoms like bradykinesia, rigidity and tremor^25	Baseline UPDRS motor off-medication scores improve by 27–54%^Citation70,Citation72,Citation73 ADLs improve by 30–39%^Citation40,Citation72,Citation73
Newer targets
Ventrolateral thalamus: Reduces tremor severity; relatively ineffective in improving bradykinesia and rigidity^9
Ventral intermediate nucleus (Vim)	Mostly effective in controlling ET^Citation74,Citation75 or in patients with PD and ET^Citation26,Citation76	According to a network-meta-analysis, Vim DBS shows better improvement in UPDRS scores than GPi DBS and STN DBS in off medication phase and therefore can be used in tremor dominant PD^26 The beneficial effect of Vim DBS has been seen even 10 years post procedure^77
Pedunculopontine nucleus (PPN) Typically low stimulation frequencies are employed (20–80 Hertz) and closed-loop DBS strategies are employed.^Citation9,Citation78	Effective in PD patients with predominant postural instability and gait difficulty (PIGD) Usually used with simultaneous STN DBS) as its efficacy as a lone target is debatable.^78	Bilateral PPN DBS alone^79 Total UPDRS improved by 53% UPDRS part III (motor sub score) improved by 57% Levodopa dose reduction by 32.5% Dual PPN DBS and STN DBS^80 UPDRS III reduction in off medication phase: 56% STN plus PPN DBS vs 54% STN DBS and 33% PPN DBS Dual PPN DBS and STN DBS improves spinal excitability in PD.^81
Posterior subthalamic area (PSA)	Effective in PD tremor^82	Two years after surgery^82 Tremor improved by 78.3% Rigidity by 92.7% Akinesia by 65.7% Gait, posture and handwriting also showed improvement
Dual STN and caudal zona incerta (cZI)	cZI associated with better motor improvement than BMT, especially tremor^46	Improvement in mean UPDRS part III score in patients with idiopathic PD was 55 ± 9% (95% CI); improvement in subscores for rigidity, bradykinesia, tremor and axial features.^47

Abbreviations: ADL, activities of daily living; BMT, best medical treatment; CI, confidence interval; ET, essential tremor; PD, Parkinson’s disease; UPDRS, Unified Parkinson Disease Rating Scale.

Figure 1 Open versus closed-loop DBS.

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