Low-frequency deep brain stimulation

Low-frequency deep brain stimulation

Patients with Parkinson’s disease can develop axial symptoms, including speechgait, and balance difficulties. Chronic high-frequency deep brain stimulation (>100 Hz) can contribute to these impairments while low-frequency stimulation (<100 Hz) may improve symptoms but only in some individuals.

DBS at frequencies below 100 Hz is a therapeutic option in select cases of Parkinson’s disease with freezing of gait and other axial symptoms, and in select patients with dystonia and other hyperkinetic movements, particularly those requiring an energy-saving strategy 1).

In ten studies with 132 patients, the pooled results showed no significant difference in the total Unified Parkinson Disease Rating Scale part III (UPDRS-III) scores (mean effect, -1.50; p = 0.19) or the rigidity subscore between HFS and LFS. Compared to LFS, HFS induced a greater reduction in the tremor subscore within the medication-off condition (mean effect, 1.01; p = 0.002), while no significance was shown within the medication-on condition (mean effect, 0.01; p = 0.92). LFS induced greater reduction in akinesia subscore (mean effect, -1.68, p = 0.003), the time to complete the stand-walk-sit (SWS) test (mean effect, -4.84; p < 0.00001), and the number of freezing of gait (FOG) (mean effect, -1.71; p = 0.03). These results suggest that two types of frequency settings may have different effects, that is, HFS induces better responses for tremor and LFS induces greater response for akinesia, gait, and FOG, respectively, which are worthwhile to be confirmed in a future study, and will ultimately inform the clinical practice in the management of PD using STN-DBS 2).

Vijiaratnam et al. from the Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, Unit of Functional Neurosurgery, the National Hospital for Neurology and Neurosurgery, London, Unit of Neurology of Ospedale “M. Bufalini” of Cesena, Cesena, Italy Department of Neurology, the Walton Centre NHS Foundation Trust, Liverpool recruited patients who developed axial motor symptoms while using high-frequency stimulation and objectively assessed the short-term impact of low-frequency stimulation on axial symptoms, other aspects of motor function and quality of life. A retrospective chart review was then conducted on a larger cohort to identify which patient characteristics were associated with not only the need to trial low-frequency stimulation but also those which predicted its sustained use. Among 20 prospective patients, low-frequency stimulation objectively improved mean motor and axial symptom severity and quality of life in the short term. Among a retrospective cohort of 168 patients, those with less severe tremor and those in whom axial symptoms had emerged sooner after subthalamic nucleus deep brain stimulation were more likely to be switched to and remain on long-term low-frequency stimulation. These data suggest that low-frequency stimulation results in objective mean improvements in overall motor function and axial symptoms among a group of patients, while individual patient characteristics can predict sustained long-term benefits. Longer follow-up in the context of a larger, controlled, double-blinded study would be required to provide definitive evidence of the role of low-frequency deep brain stimulation 3).

To investigate whether LF-SNr-DBS combined with standard HF stimulation of the subthalamic nucleus (STN) is clinically relevant in improving gait disorders that no longer respond to levodopa in PD patients, compared with HF-STN or LF-SNr stimulation alone.

Methods: Patients received LF-SNr or HF-STN stimulation alone or combined (COMB) stimulation of both nuclei (crossover design). The nucleus to be stimulated was randomly assigned and clinical evaluations performed by a blinded examiner after three months follow-up for each. Clinical assessment included the Freezing of Gait questionnaire, Tinetti Balance and Walking Assessing tool, and Unified Parkinson’s Disease Rating.

Results: We included six patients (mean age 59.1 years, disease duration 16.1 years). All patients suffered motor fluctuations and dyskinesias. The best results were obtained with COMB in four patients (who preferred and remained with COMB over 3 years of follow-up) and with HF-STN in two patients. SNr stimulation alone did not produce better results than COMB or STN in any patient.

Conclusion: COMB and HF-STN stimulation improved PD-associated gait disorders in this preliminary case series, sustained over time. Further multicenter investigations are required to better explore this therapeutic option 4).

Sidiropoulos et al. studied the effects of low-frequency stimulation (LFS) (≤80 Hz) for improving speech, gait, and balance dysfunction in the largest patient population to date. PD patients with bilateral STN-DBS and resistant axial symptoms were switched from chronic 130 Hz stimulation to LFS and followed up to 4 years. Primary outcome measures were total motor UPDRS scores, and axial and gait subscores before and after LFS. Bivariate analyses and correlation coefficients were calculated for the different conditions. Potential predictors of therapeutic response were also investigated. Forty-five advanced PD patients who had high-frequency stimulation (HFS) for 39.5 ± 27.8 consecutive months were switched to LFS. LFS was kept on for a median period of 111.5 days before the assessment. There was no significant improvement in any of the primary outcomes between HFS and LFS, although a minority of patients preferred to be maintained on LFS for longer periods of time. No predictive factors of response could be identified. There was overall no improvement from LFS in axial symptoms. This could be partly due to some study limitations. Larger prospective trials are warranted to better clarify the impact of stimulation frequency on axial signs 5).


Baizabal-Carvallo JF, Alonso-Juarez M. Low-frequency deep brain stimulation for movement disorders. Parkinsonism Relat Disord. 2016 Oct;31:14-22. doi: 10.1016/j.parkreldis.2016.07.018. Epub 2016 Jul 30. PMID: 27497841.

Su D, Chen H, Hu W, Liu Y, Wang Z, Wang X, Liu G, Ma H, Zhou J, Feng T. Frequency-dependent effects of subthalamic deep brain stimulation on motor symptoms in Parkinson’s disease: a meta-analysis of controlled trials. Sci Rep. 2018 Sep 27;8(1):14456. doi: 10.1038/s41598-018-32161-3. PMID: 30262859; PMCID: PMC6160461.

Vijiaratnam N, Girges C, Wirth T, Grover T, Preda F, Tripoliti E, Foley J, Scelzo E, Macerollo A, Akram H, Hyam J, Zrinzo L, Limousin P, Foltynie T. Long-term success of low-frequency subthalamic nucleus stimulation for Parkinson’s disease depends on tremor severity and symptom duration. Brain Commun. 2021 Jul 28;3(3):fcab165. doi: 10.1093/braincomms/fcab165. PMID: 34396114; PMCID: PMC8361419.

Valldeoriola F, Muñoz E, Rumià J, Roldán P, Cámara A, Compta Y, Martí MJ, Tolosa E. Simultaneous low-frequency deep brain stimulation of the substantia nigra pars reticulata and high-frequency stimulation of the subthalamic nucleus to treat levodopa unresponsive freezing of gait in Parkinson’s disease: A pilot study. Parkinsonism Relat Disord. 2019 Mar;60:153-157. doi: 10.1016/j.parkreldis.2018.09.008. Epub 2018 Sep 5. PMID: 30241951.

Sidiropoulos C, Walsh R, Meaney C, Poon YY, Fallis M, Moro E. Low-frequency subthalamic nucleus deep brain stimulation for axial symptoms in advanced Parkinson’s disease. J Neurol. 2013 Sep;260(9):2306-11. doi: 10.1007/s00415-013-6983-2. Epub 2013 Jun 9. PMID: 23749331.

Subthalamic deep brain stimulation for Parkinson’s disease outcome

The bilateral effects of deep brain stimulation (DBS) on motor and non-motor symptoms of Parkinson’s disease (PD) have been extensively studied and reviewed. However, the unilateral effects-in particular, the potential lateralized effects of left- versus right-sided DBS-have not been adequately recognized or studied.

Lin et al. summarized the current evidence and controversies in the literature regarding the lateralized effects of DBS on motor and non-motor outcomes in PD patients. Publications in the English language before February 2021 were obtained from the PubMed database and included if they directly compared the effects of unilateral versus contralateral side DBS on the motor or non-motor outcomes in PD. The current literature is overall of low-quality and is biased by various confounders. Researchers have investigated mainly PD patients receiving subthalamic nucleus (STN) DBS while the potential lateralized effects of globus pallidus internus (GPi) DBS have not been adequately studied. Evidence suggests potential lateralized effects of STN DBS on axial motor symptoms and deleterious effects of left-sided DBS on language-related functions, in particular, the verbal fluency, in PD. The lateralized DBS effects on appendicular motor symptoms as well as other neurocognitive and neuropsychiatric domains remain inconclusive. Future studies should control for varying methodological approaches as well as clinical and DBS management heterogeneities, including symptom laterality, stimulation parameters, location of active contacts, and lead trajectories. This would contribute to improved treatment strategies such as personalized target selection, surgical planning, and postoperative management that ultimately benefit patients 1).

The surgical and clinical outcomes of asleep DBS for Parkinson’s disease are comparable to those of awake DBS 2).

Suboptimal targeting within the STN can give rise to intolerable sensorimotor side effects, such as dysarthria, contractions and paresthesias 3) 4) 5). eye movement perturbations, and psychiatric symptoms 6) 7) 8), limiting the management of motor symptoms. The small size of the STN motor territory and the consequences of spreading current to immediately adjacent structures obligate precise targeting. Neurosurgeons therefore rely on a combination of imaging, electrophysiology, kinesthetic responses, and stimulation testing to accurately place the DBS lead into the sensorimotor domain of STN 9) 10) 11).

Deep Brain Stimulation has been associated with post-operative neuropsychology changes, especially in verbal memory.

Deep brain stimulation (DBS) of subthalamic nucleus (STN) is widely accepted to treat advanced Parkinson disease (PD). However, published studies were mainly conducted in Western centers 12).

High frequency subthalamic nucleus (STN) deep brain stimulation (DBS) improves the cardinal motor signs of Parkinson’s disease (PD) and attenuates STN alpha/beta band neural synchrony in a voltage-dependent manner. While there is a growing interest in the behavioral effects of lower frequency (60 Hz) DBS, little is known about its effect on STN neural synchrony.

Low-frequency stimulation of the subthalamic nucleus via the optimal contacts is effective in improving overall motor function of patients with Parkinson Disease 13). In Parkinson’s disease significantly improved important aspects of QoL as measured by PDQ-39. The improvements were maintained at 2 years follow-up except for social support and communication. Sobstyl et al., demonstrated a positive correlation between changes in the off condition of motor UPDRS scores and Unified Dyskinesia Rating Scale in several PDQ-39 dimensions, whereas fluctuation UPDRS scores were negatively correlated with PDQ-39 mobility scores 14).

The degree of clinical improvement achieved by deep brain stimulation (DBS) is largely dependent on the accuracy of lead placement.

A study reports on the evaluation of intraoperative MRI (iMRI) for adjusting deviated electrodes to the accurate anatomical position during DBS surgery and acute intracranial changes 15).

Although dementia is a contraindication in deep brain stimulation for Parkinson’s disease, the concept is supported by little scientific evidence. Moreover, it is unclear whether PD with mild cognitive impairment (PD-MCI) or domain-specific cognitive impairments affect the outcome of DBS in non-demented PD patients.

Baseline cognitive levels of patients with PD who underwent DBS were classified into PD with dementia (PDD) (n = 15), PD-MCI (n = 210), and normal cognition (PD-NC) (n = 79). The impact of the cognitive level on key DBS outcome measures [mortality, nursing home admission, progression to Hoehn&Yahr (HY) stage 5 and progression to PDD] were analyzed using Cox regression models. Park et al. also investigated whether impairment of a specific cognitive domain could predict these outcomes in non-demented patients.

Results: Patients with PDD showed a substantially higher risk of nursing home admission and progression to HY stage 5 compared with patients with PD-MCI [hazard ratio (HR) 4.20, P = .002; HR = 5.29, P < .001] and PD-NC (HR 7.50, P < .001; HR = 7.93, P < .001). MCI did not alter the prognosis in patients without dementia, but those with visuospatial impairment showed poorer outcomes for nursing home admission (P = .015), progression to HY stage 5 (P = .027) and PDD (P = .006).

Conclusions: Cognitive profiles may stratify the pre-operative risk and predict long-term outcomes of DBS in PD 16).


Lin Z, Zhang C, Li D, Sun B. Lateralized effects of deep brain stimulation in Parkinson’s disease: evidence and controversies. NPJ Parkinsons Dis. 2021 Jul 22;7(1):64. doi: 10.1038/s41531-021-00209-3. PMID: 34294724.

Wang J, Ponce FA, Tao J, Yu HM, Liu JY, Wang YJ, Luan GM, Ou SW. Comparison of Awake and Asleep Deep Brain Stimulation for Parkinson’s Disease: A Detailed Analysis Through Literature Review. Neuromodulation. 2019 Dec 12. doi: 10.1111/ner.13061. [Epub ahead of print] Review. PubMed PMID: 31830772.
3) , 10)

Benabid AL, Chabardes S, Mitrofanis J, Pollak P: Deep brain stimulation of the subthalamic nucleus for the treatment of Parkinson’s disease. Lancet Neurol 8:67–81, 2009
4) , 11)

Groiss SJ, Wojtecki L, Südmeyer M, Schnitzler A: Deep brain stimulation in Parkinson’s disease. Ther Adv Neurol Disorder 2:20–28, 2009

Zhang S, Zhou P, Jiang S, Wang W, Li P: Interleaving subthalamic nucleus deep brain stimulation to avoid side effects while achieving satisfactory motor benefits in Parkinson disease: a report of 12 cases. Medicine (Baltimore) 95:e5575, 2016

Kulisevsky J, Berthier ML, Gironell A, Pascual-Sedano B, Molet J, Parés P: Mania following deep brain stimulation for Parkinson’s disease. Neurology 59:1421–1424, 2002

Mallet L, Schüpbach M, N’Diaye K, Remy P, Bardinet E, Czernecki V, et al: Stimulation of subterritories of the subthalamic nucleus reveals its role in the integration of the emotional and motor aspects of behavior. Proc Natl Acad Sci U S A 104:10661–10666, 2007

Raucher-Chéné D, Charrel CL, de Maindreville AD, Limosin F: Manic episode with psychotic symptoms in a patient with Parkinson’s disease treated by subthalamic nucleus stimulation: improvement on switching the target. J Neurol Sci 273:116–117, 2008

Abosch A, Timmermann L, Bartley S, Rietkerk HG, Whiting D, Connolly PJ, et al: An international survey of deep brain stimulation procedural steps. Stereotact Funct Neurosurg 91:1–11, 2013

Chiou SM, Lin YC, Huang HM. One-year Outcome of Bilateral Subthalamic Stimulation in Parkinson Disease: An Eastern Experience. World Neurosurg. 2015 Jun 10. pii: S1878-8750(15)00709-3. doi: 0.1016/j.wneu.2015.06.002. [Epub ahead of print] PubMed PMID: 26072454.

Khoo HM, Kishima H, Hosomi K, Maruo T, Tani N, Oshino S, Shimokawa T, Yokoe M, Mochizuki H, Saitoh Y, Yoshimine T. Low-frequency subthalamic nucleus stimulation in Parkinson’s disease: A randomized clinical trial. Mov Disord. 2014 Jan 21. doi: 10.1002/mds.25810. [Epub ahead of print] PubMed PMID: 24449169.

Sobstyl M, Ząbek M, Górecki W, Mossakowski Z. Quality of life in advanced Parkinson’s disease after bilateral subthalamic stimulation: 2 years follow-up study. Clin Neurol Neurosurg. 2014 Sep;124:161-5. doi: 10.1016/j.clineuro.2014.06.019. Epub 2014 Jun 23. PubMed PMID: 25051167.

Cui Z, Pan L, Song H, Xu X, Xu B, Yu X, Ling Z. Intraoperative MRI for optimizing electrode placement for deep brain stimulation of the subthalamic nucleus in Parkinson disease. J Neurosurg. 2016 Jan;124(1):62-9. doi: 10.3171/2015.1.JNS141534. Epub 2015 Aug 14. PubMed PMID: 26274983.

Park KW, Jo S, Kim MS, et al. Cognitive profile as a predictor of the long-term outcome after deep brain stimulation in Parkinson’s disease [published online ahead of print, 2020 Jul 28]. J Neurol Sci. 2020;417:117063. doi:10.1016/j.jns.2020.117063

Brain death

Brain death

The published World Brain Death Project aims in alleviating inconsistencies in clinical guidelines and practice in the determination of death by neurologic criteria. However, critics have taken issue with a number of epistemic and metaphysical assertions that critics argue are either false, ad hoc, or confused.

Lazaridis disscussed the nature of a definition of death; the plausibility of neurologic criteria as a sensible social, medical, and legal policy; and within a Rawlsian liberal framework, reasons for personal choice or accommodation among neurologic and circulatory definitions. Declaration of human death cannot rest on contested metaphysics or unmeasurable standards, instead it should be regarded as a plausible and widely accepted social construct that conforms to best available and pragmatic medical science and practice. The definition(s) and criteria should be transparent, publicly justifiable, and potentially allow for the accommodation of reasonable choice. This is an approach that situates the definition of death as a political matter. The approach anticipates that no conceptualization of death can claim universal validity, since this is a question that cannot be settled solely on biologic or scientific grounds, rather it is a matter of normative preference, socially constructed and historically contingent 1).

The concept of brain death has periodically come under criticism 2).

Confirmatory tests for the diagnosis of brain death in addition to clinical findings may shorten observation time required in some countries and may add certainty to the diagnosis under specific circumstances.

The current U.S. approach to determining death was developed in response to the emergence of technologies that made the traditional standard of cardiopulmonary death problematic. In 1968, an ad hoc committee at Harvard Medical School published an influential article arguing for extending the concept of death to patients in an “irreversible coma.“ 3). The emerging neurologic criteria for death defined it in terms of loss of the functional activity of the brain stem and cerebral cortex. Although clinical criteria were developed in the 1960s, it took more than a decade for consensus over a rationale for the definition to emerge. In 1981, the President’s Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research provided a philosophical definition of brain death in terms of the loss of the critical functions of the organism as a whole 4).

Shortly thereafter, the National Conference of Commissioners on Uniform State Laws produced the Uniform Determination of Death Act, which has been adopted in 45 states and recognized in the rest through judicial opinion 5).

see Computed tomography angiography for brain death.

Changes in S100B protein, especially the levels of this dimer 48 hours after trauma can be used as marker to predict brain death. Alongside other known prognostic factors such as age, GCS and diameters of the pupils, however, this factor individually can not conclusive predict the patient’s clinical course and incidence of brain death. However, it is suitable to use GCS, CT scan, clinical symptoms and biomarkers together for a perfect prediction of brain death 6).

Near-Infrared Spectroscopy for Brain death

The practicability of Gadolinium-enhanced magnetic resonance angiography to confirm cerebral circulatory arrest was assessed after the diagnosis of brain death in 15 patients using a 1.5 Tesla MRI scanner. In all 15 patients extracranial blood flow distal to the external carotid arteries was undisturbed. In 14 patients no contrast medium was noted within intracerebral vessels above the proximal level of the intracerebral arteries. In one patient more distal segments of the anterior and middle cerebral arteries (A3 and M3) were filled with contrast medium. Gadolinium-enhanced MRA may be considered conclusive evidence of cerebral circulatory arrest, when major intracranial vessels fail to fill with contrast medium while extracranial vessels show normal blood flow 7).

The level of knowledge of medical students at Centro Universitário Lusíada – UNILUS- Santos (SP), Brazil, regarding brain death and transplantation is limited, which could be the result of inadequate education during medical school 8).

Brain death criteria.

In a editorial, Hibi et al., aimed to provide an outline of the world history of liver transplantation (LT), with a special focus on the innovation, development, and current controversies of living donor (LD) LT from East Asian and Western perspectives. In 1963, Starzl et al. (University of Colorado, U.S.) performed the world’s first human LT for a 3-year-old child with biliary atresia. The donor was a 3-year-old patient who had suffered from brain death following neurosurgery9).


Lazaridis C. Defining Death: Reasonableness and Legitimacy. J Clin Ethics. 2021 Summer;32(2):109-113. PMID: 34129526.

Truog RD, Miller FG, Halpern SD. The dead-donor rule and the future of organ donation. N Engl J Med 2013;369:1287-1289

A definition of irreversible coma: report of the Ad Hoc Committee of the Harvard Medical School to Examine the Definition of Brain Death. JAMA 1968;205:337-340

President’s Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research. Defining death: a report on the medical, legal and ethical issues in the determination of death. Washington, DC: Government Printing Office, 1981.

National Conference of Commissioners on Uniform State Laws. Uniform Determination of Death Act, 1981 (http://www.uniformlaws.org/shared/docs/determination%20of%20death/udda80.pdf).

Shakeri M, Mahdkhah A, Panahi F. S100B Protein as a Post-traumatic Biomarker for Prediction of Brain Death in Association With Patient Outcomes. Arch Trauma Res. 2013 Aug;2(2):76-80. doi: 10.5812/atr.8549. Epub 2013 Aug 1. PubMed PMID:24396798.

Luchtmann M, Beuing O, Skalej M, Kohl J, Serowy S, Bernarding J, Firsching R. Gadolinium-enhanced magnetic resonance angiography in brain death. Sci Rep. 2014 Jan 13;4:3659. doi: 10.1038/srep03659. PubMed PMID: 24413880.

Reis FP, Gomes BH, Pimenta LL, Etzel A. Brain death and tissue and organ transplantation: the understanding of medical students. Rev Bras Ter Intensiva. 2013 Oct-Dec;25(4):279-283. Portuguese, English. PubMed PMID: 24553508.

Hibi T, Eguchi S, Egawa H. Evolution of living donor liver transplantation: A global perspective. J Hepatobiliary Pancreat Sci. 2018 Jun 28. doi: 10.1002/jhbp.571. [Epub ahead of print] PubMed PMID: 29953731.
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