Pain in Parkinson's disease and the role of the subthalamic nucleus.

Pain is a frequent and poorly treated symptom of Parkinson's disease, mainly due to scarce knowledge of its basic mechanisms. In Parkinson's disease, deep brain stimulation of the subthalamic nucleus is a successful treatment of motor symptoms, but also might be effective in treating pain. However, it has been unclear which type of pain may benefit and how neurostimulation of the subthalamic nucleus might interfere with pain processing in Parkinson's disease. We hypothesized that the subthalamic nucleus may be an effective access point for modulation of neural systems subserving pain perception and processing in Parkinson's disease. To explore this, we discuss data from human neurophysiological and psychophysical investigations. We review studies demonstrating the clinical efficacy of deep brain stimulation of the subthalamic nucleus for pain relief in Parkinson's disease. Finally, we present some of the key insights from investigations in animal models, healthy humans and Parkinson's disease patients into the aberrant neurobiology of pain processing and consider their implications for the pain-relieving effects of subthalamic nucleus neuromodulation. The evidence from clinical and experimental studies supports the hypothesis that altered central processing is critical for pain generation in Parkinson's disease and that the subthalamic nucleus is a key structure in pain perception and modulation. Future preclinical and clinical research should consider the subthalamic nucleus as an entry point to modulate different types of pain, not only in Parkinson's disease but also in other neurological conditions associated with abnormal pain processing.

No Adverse Effects following Off-Label Magnetic Resonance Imaging in a Patient with Two Deep Brain Stimulation Systems: A Case Report.

Magnetic resonance imaging (MRI) in patients with implanted deep brain stimulation (DBS) systems is subject to strict guidelines in order to ensure patient safety. Criteria include limits on the number of implanted leads. Here, we describe the case of a 29-year-old patient with generalized dystonia implanted with 4 DBS electrodes and 2 implantable pulse generators, who had an off-label spinal MRI without regard for manufacturer guidance yet suffered no adverse effects. This suggests that manufacturer guidelines might be overly restrictive with regards to limits on implanted DBS hardware. Further research in this area is needed to widen access to this fundamental imaging modality for patients with DBS.

Acute foot drop secondary to lumbar disc prolapse after seizure.

Generalised tonic-clonic seizures have been reported to cause musculoskeletal injuries including vertebral fractures usually without resultant neurological deficit. Lumbar disc prolapse resulting in neurological deficits following seizures has not been reported. We report a 43-year-old man who presented after a generalised seizure at which point he developed worsening of low back pain and left sciatica followed by an acute foot drop. His lumbo-sacral MRI demonstrated a diffuse disc bulge at L4-5 level and a large, caudally migrated, free disc fragment with resulting severe canal stenosis at L4/5 and left lateral recess stenosis at L5/S1. He underwent urgent left L4/5 and L5/S1 micro-discectomies with resolution of his symptoms. We illustrate a rare but important treatable complication of seizures. Detailed history and clinical examination in patients with post-ictal neurological deficit should be conducted to identify the specific cause. Appropriate imaging should be performed if there remains any doubt regarding diagnosis.

Why are neurosurgeons sued? A single-center, half-decade review.

Purpose:The burden of medicolegal claims in neurosurgery is increasing in the UK. Trepidation associated with malpractice claims has the potential to negatively impact surgical practice and patient safety. What are the causes of these claims and can we address them? The aim of this study was to identify the incidence and total burden of litigation claims related to neurosurgery in a London tertiary center.Methods:We retrospectively reviewed all consecutive cases of claims in neurosurgery that were reported to NHSR between March 2013 and April 2018 by St George's Hospital legal department. This was an extension of previous study by Mukherjee et al., who studied the medicolegal claims in our institution in the preceding 9-year period (2004-2013).Results:There were 18 litigation claims against neurosurgery. Claims were reviewed for clinical event, cause, likelihood of pay-out and legal outcome. Eleven claims were settled in court and seven were settled without court proceeding. All claims were spinal cases, 56% emergency admissions. Causes included faulty surgical technique (39%), delayed treatment (33%), delayed diagnosis/misdiagnosis (17%), and lack of information (11%) with a likelihood of financial success of 43%, 67%, 33%, and 100%, respectively. The highest median pay-outs were for lack of information (£2.8 million) and faulty surgical technique (£1 million). When compared to the preceding 9-year period, there a modest reduction in claims per year, despite an increase in workload. Distribution of litigation causes remained similar but overall financial burden was higher.Conclusion:Spinal surgery has the highest malpractice claim risk in neurosurgical practice. Our review shows that faulty surgical technique is the leading cause of neurosurgical claims. Claims against lack of information, although less frequent, resulted in the highest median pay-out. This study reinforces previously published data that good surgical technique and thorough process of informed consent may reduce litigation in neurosurgery.

The Cumulative Effect of Transient Synchrony States on Motor Performance in Parkinson's Disease.

Bursts of beta frequency band activity in the basal ganglia of patients with Parkinson's disease (PD) are associated with impaired motor performance. Here we test in human adults whether small variations in the timing of movement relative to beta bursts have a critical effect on movement velocity and whether the cumulative effects of multiple beta bursts, both locally and across networks, matter. We recorded local field potentials from the subthalamic nucleus (STN) in 15 PD patients of both genders OFF-medication, during temporary lead externalization after deep brain stimulation surgery. Beta bursts were defined as periods exceeding the 75th percentile amplitude threshold. Subjects performed a visual cued joystick reaching task, with the visual cue being triggered in real time with different temporal relationships to bursts of STN beta activity. The velocity of actions made in response to cues prospectively triggered by STN beta bursts was slower than when responses were not time-locked to recent beta bursts. Importantly, slow movements were those that followed multiple bursts close to each other within a trial. In contrast, small differences in the delay between the last burst and movement onset had no significant impact on velocity. Moreover, when the overlap of bursts between the two STN was high, slowing was more pronounced. Our findings suggest that the cumulative, but recent, history of beta bursting, both locally and across basal ganglia networks, may impact on motor performance.SIGNIFICANCE STATEMENT Bursts of beta frequency band activity in the basal ganglia are associated with slowing of voluntary movement in patients with Parkinson's disease. We show that slow movements are those that follow multiple bursts close to each other and bursts that are coupled across regions. These results suggest that the cumulative, but recent, history of beta bursting, both locally and across basal ganglia networks, impacts on motor performance in this condition. The manipulation of burst dynamics may be a means of selectively improving motor impairment.

Closed-Loop Deep Brain Stimulation for Essential Tremor Based on Thalamic Local Field Potentials.

BACKGROUND: High-frequency thalamic stimulation is an effective therapy for essential tremor, which mainly affects voluntary movements and/or sustained postures. However, continuous stimulation may deliver unnecessary current to the brain due to the intermittent nature of the tremor. OBJECTIVE: We proposed to close the loop of thalamic stimulation by detecting tremor-provoking movement states using local field potentials recorded from the same electrodes implanted for stimulation, so that the stimulation is only delivered when necessary. METHODS: Eight patients with essential tremor participated in this study. Patient-specific support vector machine classifiers were first trained using data recorded while the patient performed tremor-provoking movements. Then, the trained models were applied in real-time to detect these movements and triggered the delivery of stimulation. RESULTS: Using the proposed method, stimulation was switched on for 80.37 ± 7.06% of the time when tremor-evoking movements were present. In comparison, the stimulation was switched on for 12.71 ± 7.06% of the time when the patients were at rest and tremor-free. Compared with continuous stimulation, a similar amount of tremor suppression was achieved while only delivering 36.62 ± 13.49% of the energy used in continuous stimulation. CONCLUSIONS: The results suggest that responsive thalamic stimulation for essential tremor based on tremor-provoking movement detection can be achieved without any requirement for external sensors or additional electrocorticography strips. Further research is required to investigate whether the decoding model is stable across time and generalizable to the variety of activities patients may engage with in everyday life. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Neurophysiological Correlates of Trait Impulsivity in Parkinson's Disease.

BACKGROUND: Impulsivity is common in people with Parkinson's disease (PD), with many developing impulsive compulsive behavior disorders (ICB). Its pathophysiological basis remains unclear. OBJECTIVES: We aimed to investigate local field potential (LFP) markers of trait impulsivity in PD and their relationship to ICB. METHODS: We recorded subthalamic nucleus (STN) LFPs in 23 PD patients undergoing deep brain stimulation implantation. Presence and severity of ICB were assessed by clinical interview and the Questionnaire for Impulsive-Compulsive Disorders in PD-Rating Scale (QUIP-RS), whereas trait impulsivity was estimated with the Barratt Impulsivity Scale (BIS-11). Recordings were obtained during the off dopaminergic states and the power spectrum of the subthalamic activity was analyzed using Fourier transform-based techniques. Assessment of each electrode contact localization was done to determine the topography of the oscillatory activity recorded. RESULTS: Patients with (n = 6) and without (n = 17) ICB had similar LFP spectra. A multiple regression model including QUIP-RS, BIS-11, and Unified PD Rating Scale-III scores as regressors showed a significant positive correlation between 8-13 Hz power and BIS-11 score. The correlation was mainly driven by the motor factor of the BIS-11, and was irrespective of the presence or absence of active ICB. Electrode contact pairs with the highest α power, which also correlated most strongly with BIS-11, tended to be more ventral than contact pairs with the highest beta power, which localize to the dorsolateral motor STN. CONCLUSIONS: Our data suggest a link between α power and trait impulsivity in PD, irrespective of the presence and severity of ICB. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Postoperative Externalization of Deep Brain Stimulation Leads Does Not Increase Infection Risk.

OBJECTIVES: Externalization of deep brain stimulation (DBS) leads is performed to allow electrophysiological recording from implanted electrodes as well as assessment of clinical response to trial stimulation before implantable pulse generator (IPG) insertion. Hypothetically, lead externalization provides a route for inoculation and subsequent infection of hardware, though this has not been established definitively in the literature. We sought to determine if lead externalization affects the risk of infection in DBS surgery. MATERIALS AND METHODS: We present our center's experience of lead externalization and surgical site infection (SSI) in DBS surgery for movement disorders. Patients were divided into two cohorts: one in which leads were not externalized and IPGs were implanted at the time of electrode insertion, and one in which leads were externalized for six days while patients underwent electrophysiological recording from DBS electrodes for research. We compare baseline characteristics of these two cohorts and their SSI rates. RESULTS: Infective complications were experienced by 3/82 (3.7%) patients overall with one (1.2%) requiring complete hardware removal. These occurred in 1/36 (2.7%) in the externalized cohort and 2/46 (4.3%) in the nonexternalized cohort. The incidence of infection between the two cohorts was not significantly different (p = 1, two-tailed Fisher's exact test). This lack of significant difference persisted when baseline variation between the cohorts in age, hardware manufacturer, and indication for DBS were corrected by excluding patients implanted for dystonia, none of whom underwent externalization. We present and discuss in detail each of the three cases of infection. CONCLUSIONS: Our data suggest that externalization of leads does not increase the risk of infective complications in DBS surgery. Lead externalization is a safe procedure which can provide a substrate for unique neurophysiological studies to advance knowledge and therapy of disorders treated with DBS.

Operative planning aid for optimal endoscopic third ventriculostomy entry points in pediatric cases.

OBJECT: Endoscopic third ventriculostomy (ETV) uses anatomical spaces of the ventricular system to reach the third ventricle floor and create an alternative pathway for cerebrospinal fluid flow. Optimal ETV trajectories have been previously proposed in the literature, designed to grant access to the third ventricle floor without a displacement of eloquent periventricular structures. However, in hydrocephalus, there is a significant variability to the configuration of the ventricular system, implying that the optimal ETV trajectory and cranial entry point needs to be planned on a case-by-case basis. In the current study, we created a mathematical model, which tailors the optimal ETV entry point to the individual case by incorporating the ventricle dimensions. METHODS: We retrospectively reviewed the imaging of 30 consecutive pediatric patients with varying degrees of ventriculomegaly. Three dimensional radioanatomical models were created using preoperative MRI scans to simulate the optimal ETV trajectory and entry point for each case. The surface location of cranial entry points for individual ETV trajectories was recorded as Cartesian coordinates centered at Bregma. The distance from the Bregma in the coronal plane represented as "x", and the distance from the coronal suture in the sagittal plane represented as "y". The correlation between the ventricle dimensions and the x, y coordinates were tested using linear regression models. RESULTS: The distance of the optimal ETV entry point from the Bregma in the coronal plane ("x") and from the coronal suture in the sagittal plane ("y") correlated well with the frontal horn ratio (FHR). The coordinates for x and y were fitted along the following linear equations: x = 85.8 FHR-13.3 (r 2 = 0.84, p < 0.001) and y = -69.6 FHR + 16.7 (r 2 = 0.83, p < 0.001). CONCLUSION: The surface location of the optimal cranial ETV entry point correlates well with the ventricle size. We provide the first model that can be used as a surgical planning aid for a case specific ETV entry site with the incorporation of the ventricle size.

Neurosurgical interventions for cancer pain.

PURPOSE OF REVIEW: Half of all cancer patients will develop cancer-related pain, and a fifth of these patients will continue to experience pain refractory to maximal pharmacological therapy. This, together with the opioid crisis, has prompted a resurgence in neurosurgical treatments. Neuromodulatory or neuroablative procedures are largely used for various nonmalignant, chronic pain conditions, but there is growing evidence to support their use in cancer pain. This review aims to cover the main neurosurgical treatments that may prove useful in the changing sphere of cancer pain treatment. RECENT FINDINGS: Neuromodulation techniques for pain have largely replaced neuroablation in neurosurgical practice due to the higher risk of inadvertent permanent neurological deficits from the latter. When compared to neuroablative approaches for severe treatment-refractory cancer pain, neuromodulation is more expensive (largely due to implant cost) and requires more follow-up, with greater engagement needed from the health service, the patient and their carers. Furthermore, neuroablation has a more rapid onset of effect. SUMMARY: Neuromodulation techniques for pain have largely replaced neuroablation in neurosurgical practice due to the higher risk of inadvertent permanent neurological deficits from the latter. Whilst this approach is beneficial when treating nonmalignant pain, neuromodulation in patients with pain related to advanced cancer still has a limited role. Neuroablative procedures are less expensive, require less follow-up, and can have a lower burden on health services, patients and their carers.

Clinical neurophysiological interrogation of motor slowing: A critical step towards tuning adaptive deep brain stimulation.

OBJECTIVE: Subthalamic nucleus (STN) beta activity (13-30 Hz) is the most accepted biomarker for adaptive deep brain stimulation (aDBS) for Parkinson's disease (PD). We hypothesize that different frequencies within the beta range may exhibit distinct temporal dynamics and, as a consequence, different relationships to motor slowing and adaptive stimulation patterns. We aim to highlight the need for an objective method to determine the aDBS feedback signal. METHODS: STN LFPs were recorded in 15 PD patients at rest and while performing a cued motor task. The impact of beta bursts on motor performance was assessed for different beta candidate frequencies: the individual frequency strongest associated with motor slowing, the individual beta peak frequency, the frequency most modulated by movement execution, as well as the entire-, low- and high beta band. How these candidate frequencies differed in their bursting dynamics and theoretical aDBS stimulation patterns was further investigated. RESULTS: The individual motor slowing frequency often differs from the individual beta peak or beta-related movement-modulation frequency. Minimal deviations from a selected target frequency as feedback signal for aDBS leads to a substantial drop in the burst overlapping and in the alignment of the theoretical onset of stimulation triggers (to âˆ¼ 75% for 1 Hz, to âˆ¼ 40% for 3 Hz deviation). CONCLUSIONS: Clinical-temporal dynamics within the beta frequency range are highly diverse and deviating from a reference biomarker frequency can result in altered adaptive stimulation patterns. SIGNIFICANCE: A clinical-neurophysiological interrogation could be helpful to determine the patient-specific feedback signal for aDBS.

Electrophysiological localization of eyeblink-related microzones in rabbit cerebellar cortex.

The classically conditioned eyeblink response in the rabbit is one of the best-characterized behavioral models of associative learning. It is cerebellum dependent, with many studies indicating that the hemispheral part of Larsell's cerebellar cortical lobule VI (HVI) is critical for the acquisition and performance of learned responses. However, there remain uncertainties about the distribution of the critical regions within and around HVI. In this learning, the unconditional stimulus is thought to be carried by periocular-activated climbing fibers. Here, we have used a microelectrode array to perform systematic, high-resolution, electrophysiological mapping of lobule HVI and surrounding folia in rabbits, to identify regions with periocular-evoked climbing fiber activity. Climbing fiber local field potentials and single-unit action potentials were recorded, and electrode locations were reconstructed from histological examination of brain sections. Much of the sampled cerebellar cortex, including large parts of lobule HVI, was unresponsive to periocular input. However, short-latency ipsilateral periocular-evoked climbing fiber responses were reliably found within a region in the ventral part of the medial wall of lobule HVI, extending to the base of the primary fissure. Small infusions of the AMPA/kainate receptor antagonist CNQX into this electrophysiologically defined region in awake rabbits diminished or abolished conditioned responses. The known parasagittal zonation of the cerebellum, supported by zebrin immunohistochemistry, indicates that these areas have connections consistent with an essential role in eyeblink conditioning. These small eyeblink-related areas provide cerebellar cortical targets for analysis of eyeblink conditioning at a neuronal level but need to be localized with electrophysiological identification in individual animals.

Stereotactic Radiofrequency Thalamotomy for Cancer Pain: A Systematic Review.

Pain is a common occurrence in patients with cancer, which, in some cases, is not adequately controlled with medical analgesia. Thalamotomy is a treatment option in such circumstances, but synthesis of historical evidence and thalamic stratified data are lacking. We therefore sought to systematically review evidence supporting radiofrequency thalamotomy for intractable cancer pain. This review was performed using multiple electronic databases and a (PICO) patient/problem, intervention, comparison, outcome search with the terms "radiofrequency thalamotomy" and "cancer pain." Of 22 full-text studies assessed for eligibility, 14 were included for review. Articles were excluded in which radiofrequency ablation was not used, chronic implantation was used, or the study did not include patients with cancer pain. Thirteen case series and 1 case report were included. Thalamic targets included ventral posterior, central lateral, dorsomedial, centromedian, centromedian/parafascicular, centromedian and anterior pulvinar, pulvinar, limitans, suprageniculate and posterior nuclei. Patient characteristics, operative methods, lesioning parameters, patient follow-up, and outcomes were variably reported across the studies. Where relevant outcome data were available, 97% of patients experienced initial pain relief and 79% experienced significant lasting relief. Adverse events were typically transient. We conclude that radiofrequency thalamotomy for cancer pain is well tolerated and can produce significant relief from intractable cancer pain. No superiority of thalamic target could be determined.

Multiple cerebral cavernous malformations in association with a Dubowitz-like syndrome.

Cerebral cavernous malformations (CCMs) are proliferative sinusoidal vascular lesions and are the most common vascular malformations of the brain. They can occur sporadically or secondary to an underlying genetic predisposition where multiple lesions are commonly seen. Dubowitz syndrome is a clinically-diagnosed rare genetic disorder with an unknown molecular basis. An association between these conditions has not been reported previously. A 30-year-old woman with a Dubowitz-like syndrome presented with acute left leg weakness, gait ataxia and transient loss of consciousness. Imaging revealed five CCMs with recent hemorrhage in relation to one lesion in the left middle cerebellar peduncle. A recurrent hemorrhage from the same lesion occurred ten weeks later and she underwent microsurgical excision of this malformation. Genetic analysis revealed an unbalanced chromosomal rearrangement involving partial deletion of chromosome 7q21, the locus of the CCM1/KRIT1 gene known to be associated with familial CCMs. This is the first description of CCMs in association with the Dubowitz phenotype. The genetic basis of Dubowitz syndrome may be heterogeneous but, for the first time, overlap is demonstrated between this condition and multiple CCMs, with a possible common genetic etiology. Knowledge of this association may be of help in the management of acute neurological presentations in Dubowitz-like syndromes. Keywords: Hemangioma, Cavernous, Central nervous system, Dubowitz syndrome, Genetics.

Stereotactic radiofrequency ventral posterolateral thalamotomy for cancer pain.

Palliative neuroablative procedures are often performed for medication-refractory cancer pain. A 57-year-old female with lung carcinoma and metastases to the brachial plexus and cervical spine with severe neuropathic pain affecting the right upper limb was referred to the authors' functional neurosurgery service. This video shows her treatment with an awake stereotactic radiofrequency thalamotomy targeting the left ventral posterolateral nucleus. Postoperatively, she experienced immediate and complete resolution of the pain. Palliative radiofrequency thalamotomy can be a viable and effective procedure for somatotopically distributed regional cancer pain. The video can be found here: https://youtu.be/jykYWXTP3c4.

Closed-loop DBS triggered by real-time movement and tremor decoding based on thalamic LFPs for essential tremor.

High frequency Deep Brain Stimulation (DBS) targeting the motor thalamus is an effective therapy for essential tremor (ET). However, since tremor mainly affects periods of voluntary movements and sustained postures in ET, conventional continuous stimulation may deliver unnecessary current to the brain. Here we tried to decode movement states based on local field potentials (LFPs) recorded from motor thalamus and zona incerta in real-time to trigger the switching on and off of DBS in three patients with ET. Patient-specific models were first identified using thalamic LFPs recorded while the patient performed movements that tended to trigger tremor in everyday life. During the real-time test, LFPs were continuously recorded to decode movements and tremor, and the detection triggered stimulation. Results show that voluntary movements can be detected with a mean sensitivity ranging from 76.8% to 88.6% and a false positive rate ranging from 16.0% to 23.1% Postural tremor was detected with similar accuracy. The closed-loop DBS triggered by tremor detection suppressed intention tremor by 90.5% with a false positive rate of 20.3%.Clinical Relevance- This is the first study on closed-loop DBS triggered by real-time movement and tremor decoding based solely on thalamic LFPs. The results suggest that responsive DBS based on movement and tremor detection can be achieved without any requirement for external sensors or additional electrocorticography strips.

Subthalamic beta-targeted neurofeedback speeds up movement initiation but increases tremor in Parkinsonian patients.

Previous studies have explored neurofeedback training for Parkinsonian patients to suppress beta oscillations in the subthalamic nucleus (STN). However, its impacts on movements and Parkinsonian tremor are unclear. We developed a neurofeedback paradigm targeting STN beta bursts and investigated whether neurofeedback training could improve motor initiation in Parkinson's disease compared to passive observation. Our task additionally allowed us to test which endogenous changes in oscillatory STN activities are associated with trial-to-trial motor performance. Neurofeedback training reduced beta synchrony and increased gamma activity within the STN, and reduced beta band coupling between the STN and motor cortex. These changes were accompanied by reduced reaction times in subsequently cued movements. However, in Parkinsonian patients with pre-existing symptoms of tremor, successful volitional beta suppression was associated with an amplification of tremor which correlated with theta band activity in STN local field potentials, suggesting an additional cross-frequency interaction between STN beta and theta activities.

Spinal cord stimulation in the treatment of neuropathic pain in chronic inflammatory demyelinating polyneuropathy.

We describe a case of a 70-year old man with sensorimotor chronic inflammatory demyelinating polyneuropathy (CIDP) with small-fibre involvement resulting in severe diffuse neuropathic pain which was refractory to immunotherapy and anti-neuropathic medication. His pain was successfully treated with implantation of a spinal cord stimulation (SCS) system comprising bilateral cervical and lumbar epidural leads. Following SCS programming, he experienced a 50% reduction in average pain severity with substantial improvement in quality of life, persisting at 18 months after surgery. SCS has been employed to treat a variety of neuropathic pain syndromes. However, this is the first report to our knowledge of SCS utilised effectively for pain in CIDP. This therapy should be considered in painful CIDP for neuropathic pain refractory to medical management, though further studies are required to evaluate its efficacy.

Outcomes from deep brain stimulation targeting subthalamic nucleus and caudal zona incerta for Parkinson's disease.

Both subthalamic nucleus (STN) and caudal zona incerta (cZI) have been implicated as the optimal locus for deep brain stimulation (DBS) in Parkinson's disease (PD). We present a retrospective clinico-anatomical analysis of outcomes from DBS targeting both STN and cZI. Forty patients underwent bilateral DBS using an image-verified implantable guide tube/stylette technique. Contacts on the same quadripolar lead were placed in both STN and cZI. After pulse generator programming, contacts yielding the best clinical effect were selected for chronic stimulation. OFF-medication unified PD rating scale (UPDRS) part III scores pre-operatively and ON-stimulation at 1-2 year follow up were compared. Active contacts at follow-up were anatomically localised from peri-operative imaging. Overall, mean UPDRS part III score improvement was 55 ± 9% (95% confidence interval), with improvement in subscores for rigidity (59 ± 13%), bradykinesia (58 ± 13%), tremor (71 ± 24%) and axial features (36 ± 19%). Active contacts were distributed in the following locations: (1) within posterior/dorsal STN (50%); (2) dorsal to STN (24%); (3) in cZI (21%); and (4) lateral to STN (5%). When contacts were grouped by location, no significant differences between groups were seen in baseline or post-operative improvement in contralateral UPDRS part III subscores. We conclude that when both STN and cZI are targeted, active contacts are distributed most commonly within and immediately dorsal to STN. In a subgroup of cases, cZI contacts were selected for chronic stimulation in preference. Dual targeting of STN and cZI is feasible and may provide extra benefit compared with conventional STN DBS is some patients.