Two-minute standing endurance test for axial postural abnormalities in patients with Parkinson's disease.

BACKGROUND: Photo-based measurement methods are used to assess axial postural abnormalities (PA) in Parkinson's disease (PD). However, they capture only moments in time. We developed the 2-minute standing endurance test (2 M-SET), which specifically captures temporal changes in posture, as a novel dynamic method for measuring axial PA in patients with PD. RESEARCH QUESTION: This study aimed to verify the effectiveness and validity of the 2 M-SET for capturing temporal changes in axial PA in patients with PD. METHODS: Twenty-eight patients with PD participated. The participants attempted to maintain an upright posture for 2 minutes during three tasks: standing, stepping in place, and walking. The rate of change in postural angle was recorded at 10-second intervals. Based on the results, the 2 M-SET was developed. Therapists evaluated the 2 M-SET using the NeuroPostureApp© to measure anterior trunk flexion (ATF) angles and lateral trunk flexion (LTF) angles at 0, 10, 30, 60, and 120 seconds. To assess reliability, the congruence between the measurements obtained by the therapists and those obtained using a three-dimensional motion-analysis system was examined. For validity, we assessed whether the ATF and LTF angles measured by the therapists could accurately capture postural changes at regular intervals over time. RESULTS: The average postural changes over 2 minutes for the standing, stepping in place, and gait tasks were 59.2±83.5%, 37.6±30.7%, and 45.4±50.6%, respectively. The intraclass correlation coefficients showed high reliability, with values of 0.985 and 0.970 for the ATF and LTF angles, respectively. SIGNIFICANCE: The results of our proposed 2 M-SET method, which uses temporal photo-based measurements to assess the patient's ability to maintain an upright standing position for 2 minutes, demonstrate the potential to capture temporal changes in axial PA. DATA AVAILABILITY STATEMENT: The data supporting the findings of this study are available upon reasonable request and approval from the local ethics committee.

Predictors and Pathophysiology of Axial Postural Abnormalities in Parkinsonism: A Scoping Review.

Background: Postural abnormalities involving the trunk are referred to as axial postural abnormalities and can be observed in over 20% of patients with Parkinson's disease (PD) and in atypical parkinsonism. These symptoms are highly disabling and frequently associated with back pain and a worse quality of life in PD. Despite their frequency, little is known about the pathophysiology of these symptoms and scant data are reported about their clinical predictors, making it difficult to prompt prevention strategies. Objectives: We conducted a scoping literature review of clinical predictors and pathophysiology of axial postural abnormalities in patients with parkinsonism to identify key concepts, theories and evidence on this topic. Methods: We applied a systematic approach to identify studies, appraise quality of evidence, summarize main findings, and highlight knowledge gaps. Results: Ninety-two articles were reviewed: 25% reported on clinical predictors and 75% on pathophysiology. Most studies identified advanced disease stage and greater motor symptoms severity as independent clinical predictors in both PD and multiple system atrophy. Discrepant pathophysiology data suggested different potential central and peripheral pathogenic mechanisms. Conclusions: The recognition of clinical predictors and pathophysiology of axial postural abnormalities in parkinsonism is far from being elucidated due to literature bias, encompassing different inclusion criteria and measurement tools and heterogeneity of patient samples. Most studies identified advanced disease stage and higher burden of motor symptoms as possible clinical predictors. Pathophysiology data point toward many different (possibly non-mutually exclusive) mechanisms, including dystonia, rigidity, proprioceptive and vestibular impairment, and higher cognitive deficits.

Longitudinal Assessment of Botulinum Toxin Treatment for Lateral Trunk Flexion and Pisa Syndrome in Parkinson's Disease: Real-life, Long-Term Study.

Lateral trunk flexion (LTF) and its severe form, called Pisa syndrome (PS), are highly invalidating axial postural abnormalities associated with Parkinson's disease (PD). Management strategies for LTF lack strong scientific evidence. We present a real-life, longitudinal study evaluating long-term efficacy of botulinum toxin (BoNT) injections in axial muscles to reduce LTF and PS in PD. A total of 13 PD patients with LTF > 5° received ultrasound- and electromyography-guided BoNT injections every 4 months. Seven untreated matched PD patients with LTF served as controls and their changes in posture after 18 months were compared with those of seven patients continuing BoNT over 12 months. 53.8% of patients continued the BoNT injections for at least 12 months. Various individual LTF responses were observed. Overall, BoNT-treated patients obtained a not statistically significant improvement of LTF of 17 ± 41% (p = 0.237). In comparison, the seven untreated PD patients suffered a deterioration in LTF over 12 months by 36 ± 45% (p = 0.116), showing a significantly different trajectory of posture change (p = 0.026). In conclusion, repeated BoNT injections in axial muscles showed varying effects in managing PD-associated LTF, suggesting that: (a) a relevant number of patients with LTF can benefit from BoNT; (b) long-term treatment could prevent LTF worsening; (c) an instrumented, personalized approach is important; and (d) there is a need for prospective, long-term studies.

Assessment of Axial Postural Abnormalities in Parkinsonism: Automatic Picture Analysis Software.

Background: Software-based measurements of axial postural abnormalities in Parkinson's disease (PD) are the gold standard but may be time-consuming and not always feasible in clinical practice. An automatic and reliable software to accurately obtain real-time spine flexion angles according to the recently proposed consensus-based criteria would be a useful tool for both research and clinical practice. Objective: We aimed to develop and validate a new software based on Deep Neural Networks to perform automatic measures of PD axial postural abnormalities. Methods: A total of 76 pictures from 55 PD patients with different degrees of anterior and lateral trunk flexion were used for the development and pilot validation of a new software called AutoPosturePD (APP); postural abnormalities were measured in lateral and posterior view using the freeware NeuroPostureApp (gold standard) and compared with the automatic measurement provided by the APP. Sensitivity and specificity for the diagnosis of camptocormia and Pisa syndrome were assessed. Results: We found an excellent agreement between the new APP and the gold standard for lateral trunk flexion (intraclass correlation coefficient [ICC] 0.960, IC95% 0.913-0.982, P < 0.001), anterior trunk flexion with thoracic fulcrum (ICC 0.929, IC95% 0.846-0.968, P < 0.001) and anterior trunk flexion with lumbar fulcrum (ICC 0.991, IC95% 0.962-0.997, P < 0.001). Sensitivity and specificity were 100% and 100% for detecting Pisa syndrome, 100% and 95.5% for camptocormia with thoracic fulcrum, 100% and 80.9% for camptocormia with lumbar fulcrum. Conclusions: AutoPosturePD is a valid tool for spine flexion measurement in PD, accurately supporting the diagnosis of Pisa syndrome and camptocormia.

[Abnormal posture of the trunk related to donepezil hydrochloride: report of 2 cases].

Patient 1, an 80-year-old woman with Alzheimer's disease, had been taking donepezil 5 mg for 2 years. Donepezil was increased to 10 mg, and 2 months later, the patient developed dropped head syndrome. MRI and needle EMG abnormality of the neck extensor muscles suggested focal myopathy, but the symptom disappeared within 2 months by discontinuing donepezil. Patient 2, a 78-year-old man with Lewy body dementia, had been taking levodopa and pramipexole (PPX). One month after tapering levodopa, donepezil 3 mg was introduced, and Pisa syndrome (bending of the trunk to the right anterior direction) developed 10 days later. Donepezil and PPX were discontinued and levodopa was increased. Within 5 months, his posture had almost recovered. Cholinesterase inhibitors can induce abnormal posture of the trunk, and clinicians should be aware of this uncommon but important side effect.

Visuospatial Deficits Are Associated with Pisa Syndrome and not Camptocormia in Parkinson's Disease.

Background: Pisa syndrome (PS) and camptocormia (CC) are postural abnormalities frequently associated with Parkinson's disease (PD). Their pathophysiology remains unclear, but the role of cognitive deficits has been postulated. Objectives: To identify differences in the neuropsychological functioning of patients with PD with PS or CC compared with matched patients with PD without postural abnormalities. Methods: We performed a case-control study including 57 patients with PD with PS (PS+) or CC (CC+) and 57 PD controls without postural abnormalities matched for sex, age, PD duration, phenotype, and stage. Patients were divided into four groups: PS+ (n = 32), PS+ controls (PS-, n = 32), CC+ (n = 25), and CC+ controls (CC-, n = 25). We compared PS+ versus PS- and CC+ versus CC- using a neuropsychological battery assessing memory, attention, executive functions, visuospatial abilities, and language. Subjective visual vertical (SVV) perception was assessed by the Bucket test as a sign of vestibular function; the misperception of trunk position, defined as a mismatch between the objective versus subjective evaluation of the trunk bending angle >5°, was evaluated in PS+ and CC+. Results: PS+ showed significantly worse visuospatial performances (P = 0.025) and SVV perception (P = 0.038) than their controls, whereas CC+ did not show significant differences compared with their control group. Reduced awareness of postural abnormality was observed in >60% of patients with PS or CC. Conclusions: Low visuospatial performances and vestibular tone imbalance are significantly associated with PS but not with CC. These findings suggest different pathophysiology for the two main postural abnormalities associated with PD and can foster adequate therapeutic and prevention strategies.

Axial postural abnormalities and pain in Parkinson's disease.

Axial postural abnormalities and pain are two main determinants of poor quality of life in patients with Parkinson's disease (PD). Indeed, a detailed characterization of pain and other non-motor symptoms in patients with PAs has not been provided yet. The aim of this study is to assess the phenomenology of pain and other non-motor symptoms in PD patients with Pisa syndrome and camptocormia compared to PD patients without axial postural abnormality. Forty-five PD participants were equally distributed in three groups: patients with Pisa syndrome (PS), patients with Camptocormia (CC), and patients without postural abnormalities (PD). Pain characteristics were assessed by Kings Parkinson's Pain Scale (KPPS), brief pain inventory (BPI), and numeric pain rating scale (NRS). All participants completed clinical assessments by non-motor symptom scale (NMSS), and movement disorder society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) parts II-III. Patients with and without axial postural abnormalities showed one or more types of pain, being fluctuation, nocturnal, chronic, and musculoskeletal the most frequently reported in Pisa Syndrome and camptocormia. PD group compared with PS and CC groups showed differences in the KPPS, NMSS, BPI pain severity and interference, and NRS total scores. No significant differences were found between PS group compared with CC group with exception of the NMSS total scores. PD patients with Pisa syndrome or camptocormia have a higher burden of musculoskeletal, chronic and fluctuation pain than PD patients without axial postural abnormalities, suggesting different etiologies of pain and possible different treatments.

Effect of electroacupuncture for Pisa syndrome in Parkinson's disease: A case report.

BACKGROUND: Pisa syndrome (PS) refers to marked lateral flexion of the trunk with a Cobb angle greater than 10°, which is typically mobile and can be resolved by lying down. PS is one of the most common postural deformities secondary to Parkinson's disease (PD) and can aggravate scoliosis in the advanced stages of PD. CASE SUMMARY: Here, we present the case of a 53-year-old woman who presented with lateral curvature for 6 mo. Full spine X-ray films in the correct position showed that the thoracolumbar spine was bent to the right without any rotation of the vertebrae. The patient was diagnosed with Pisa syndrome. After receiving a month's treatment with electroacupuncture, the Cobb angle decreased from 18.14° to 13.41°. CONCLUSION: This case demonstrates that electroacupuncture can effectively improve Pisa syndrome secondary to PD with few side effects and a low risk of recurrence. Additionally, early accurate diagnosis and timely intervention are meaningful for the prognosis of PS.

Reversible Pisa syndrome caused by chronic subdural hematoma in a patient with Parkinson's disease: a case report.

BACKGROUND: Pisa syndrome (PS), characterized by lateral trunk flexion, is quite common in patients with Parkinson's disease (PD). Patients with PS are older and have a significantly longer disease duration, more severe motor phenotype, ongoing combined treatment with levodopa and dopamine agonists, and higher levodopa equivalent daily dose. We describe here, to the best of our knowledge, the first case of a woman with PD who developed acute-onset PS caused by chronic subdural hematoma (CSDH). CASE PRESENTATION: A 70-year-old woman developed acute-onset lateral flexion of her trunk to the left side while standing, and she was admitted to our hospital. One month before, she had a mild head trauma with loss of consciousness. At 65 years of age, she noticed difficulty with walking and clumsiness with her hands. She was diagnosed as having PD (Hoehn and Yahr stage 2) and levodopa was initiated. Her symptoms were markedly improved. At 67 years of age, she developed orthostatic hypotension and was treated sequentially with fluids, compression stockings, and midodrine. Urgently performed brain computed tomography (CT) showed a CSDH in the right hemisphere resulting in a marked compression of the hemisphere. After surgical evacuation, her PS disappeared. She has fully recovered to her preoperative level of function. CONCLUSION: The present case provides a valuable insight, that is, the mesial frontal lobe and its connections from the posterior parietal cortex play crucial roles in maintaining the body schema and in the pathophysiology of PS. This case suggests that CSDH should be considered when clinicians examine acute-onset PS, even in patients with neurodegenerative disorders such as PD. Appropriate patient triage and timely neurosurgical intervention should be considered.

Impaired virtual space-tilting perception in Parkinson's disease with Pisa syndrome.

INTRODUCTION: The mechanism of Pisa syndrome in Parkinson's disease (PD) is unclear. We aimed to analyze the spatial perception of patients with PD with Pisa syndrome using virtual reality. METHODS: In total, 16 patients with Pisa syndrome, 16 age-matched patients without Pisa syndrome, and 16 age-matched controls were included. They viewed the virtual room gradually tilting to different 8 directions randomized across trials. The 75% discrimination threshold angle and the mean tilting discrimination angle for each direction were evaluated. Participants' lateral trunk deviation was measured using Kinect. Neuropsychological status was evaluated, using the Mini-Mental Status Examination (MMSE), the Japanese version of the Montreal-Cognitive Assessment, Frontal Assessment Battery, and the color-word interference task of the Stroop test. Visuospatial abilities were assessed using Benton Judgement of Line Orientation, and vestibular function was evaluated using Subjective Visual Vertical (SVV). RESULTS: The 75% discrimination threshold in the tilting discrimination angle was larger in all directions for those in the Pisa syndrome group compared to patients in the without Pisa syndrome group and those in the control group. There were significant differences between the three groups for Front-Right, Right, and Back. Patients with Pisa syndrome showed a significantly worse performance in these tests compared with controls and tended to have worse SVV performance compared with patients without Pisa syndrome. CONCLUSION: The present findings support the hypothesis of visuo-spatial disability and/or attentional impairment in patients with Pisa syndrome.

Pisa syndrome in dementia with Lewy bodies: A Chinese multicenter study.

BACKGROUND: Pisa syndrome (PS) is rarely reported in Dementia with Lewy bodies (DLB). The aim of this article is to investigate the prevalence rate of PS and the correlation with clinical features evaluated in patients with DLB. METHODS: A total of 209 DLB patients were consecutively recruited and underwent standardized clinical evaluation in our multicenter study. The associations between PS and clinical factors were evaluated. RESULTS: The prevalence rate of PS in patients with DLB was 15.3%, which was higher in the moderate and severe stages than mild cognitive impairment and mild stages (81.2% vs. 18.8%). Patients with PS had a longer duration of disease (P = 0.020) and parkinsonism (P = 0.003), higher scores of NPI (P = 0.028), ADL (P = 0.002) and UPDRS part III (P < 0.001), lower scores of clock drawing test (P = 0.009), visuospatial/executive abilities (P = 0.018), attention (P = 0.020), language and praxis (P = 0.020), registration (P = 0.012), greater H&Y stage (P < 0.001), and higher proportion of cholinesterase inhibitors used (P = 0.044) than those without PS. Longer disease duration (OR = 1.166, P = 0.023), presence of parkinsonism (OR = 7.971, P = 0.007), moderate and severe dementia (OR = 3.215, P = 0.021) were associated with the presence of PS. Patients had a longer duration of PS (P = 0.014) and lower mean age of onset (P = 0.040) in the group with severe lateral trunk flexion. CONCLUSION: The development of PS may be associated with longer disease duration, the presence of parkinsonism and severe stages of dementia in DLB. Cholinesterase inhibitors may have a correlation with PS. The severity of lateral flexion is related to the duration of PS and mean age of onset.

Task Force Consensus on Nosology and Cut-Off Values for Axial Postural Abnormalities in Parkinsonism.

Background: There is no consensus with regard to the nosology and cut-off values for postural abnormalities in parkinsonism. Objective: To reach a consensus regarding the nosology and cut-off values. Methods: Using a modified Delphi panel method, multiple rounds of questionnaires were conducted by movement disorder experts to define nosology and cut-offs of postural abnormalities. Results: After separating axial from appendicular postural deformities, a full agreement was found for the following terms and cut-offs: camptocormia, with thoracic fulcrum (>45°) or lumbar fulcrum (>30°), Pisa syndrome (>10°), and antecollis (>45°). "Anterior trunk flexion," with thoracic (≥25° to ≤45°) or lumbar fulcrum (>15° to ≤30°), "lateral trunk flexion" (≥5° to ≤10°), and "anterior neck flexion" (>35° to ≤45°) were chosen for milder postural abnormalities. Conclusions: For axial postural abnormalities, we recommend the use of proposed cut-offs and six unique terms, namely camptocormia, Pisa syndrome, antecollis, anterior trunk flexion, lateral trunk flexion, anterior neck flexion, to harmonize clinical practice and future research.

Add-on Cariprazine in Patients with Long-term Clozapine Treatment and Treatment Resistant Schizophrenia: Two Cases of Psychotic Deterioration and Pisa Syndrome.

An increasing number of studies deal with medical options for treatment resistant schizophrenia. If no remission can be achieved with clozapine, a combination of antipsychotics can be considered. The combination of clozapine and cariprazine is rarely studied. Cariprazine is a partial agonist on dopamine D2 and D3 receptors and a pharmaceutically rational add-on to clozapine. Stimulating D3 receptors has been linked to improved cognition and mood, with negligible extrapyramidal side effects. We present two patients with long-term treatment resistant schizophrenia receiving cariprazine and clozapine. Whereas psychotic symptoms worsened, the patients developed extrapyramidal side effects with a Pisa syndrome. The syndrome remitted after discontinuation of cariprazine. Possible explanations by pharmacodynamic interactions and drug specific receptor profiles are discussed.

Effect of Bilateral Subthalamic Nucleus Deep Brain Stimulation on Pisa Syndrome in Parkinson's Disease.

Objective: To observe the efficacy of bilateral subthalamic nucleus deep brain stimulation on Pisa syndrome in patients with Parkinson's disease. Methods: A total of 52 patients with Parkinson's disease who underwent deep brain stimulation in Beijing Hospital from July 1, 2016 to July 1, 2020 were reviewed. The clinical data were collected for the patients who met the diagnostic criteria of Pisa syndrome on "Medication-Off" state pre-operatively. Results: Two patients met the diagnostic criteria of Pisa syndrome before operation, with a Pisa angle of 10 and 14°, respectively. The lateral trunk flexion of the two patients improved after operation. In stimulation-on/medication-off state, the Pisa angle decreased from 10 to 2° and from 14 to 6°, respectively. Conclusion: Bilateral subthalamic nucleus deep brain stimulation might have beneficial effects on lateral trunk flexion in PD patients, but the predictors of curative effect are not clear.

Chronic form of Pisa syndrome after prolonged exposure to low-dose amisulpride treatment.

Pisa syndrome is a movement problem defined by tonic, sustained lateral flexion with a slight posterior rotation of the trunk. It seems to be a side effect of antipsychotic medicine in most cases. The clinical duration of Pisa syndrome can be acute, chronic, or recurrent. As far as we know, no reports are available in the literature on the chronic form of Pisa syndrome caused by low-dose amisulpride. A case of refractory tardive dystonia form of Pisa syndrome during treatment with stable low-dose amisulpride is presented in this report. Long-term, low-dosage amisulpride therapy may induce tardive dystonia even in patients with no other risk factors for dystonia.

Pisa syndrome: Pathophysiology, physical rehabilitation and falls risk.

BACKGROUND: Pisa syndrome (PS) is a postural disorder characterised by lateral flexion of the spine (> 10°), predisposing the affected individuals to falls, and contributing to increased mortality in neurodegenerative diseases. OBJECTIVE: An overview of currently applied therapeutic management options, primarily focused on specifically structured rehabilitation exercises, in conjunction with falls-risk assessment in the individuals affected by PS. METHODS: A narrative literature review, augmented with the authors' own experience in physical rehabilitation management. RESULTS: As individuals affected by PS are evidenced to be intrinsically exposed to higher falls-risk through acquired postural deformities, they often fall victims of traumatic accidents, occasionally also facing relocation into 24-hour nursing facilities due to the injuries sustained/resultant disability, consequently having overall quality of their life appreciably reduced. CONCLUSIONS: sA comprehensive approach is postulated in designing optimal therapeutic management, comprised of the exercises controlling postural stability, whilst reducing lower back pain, and the ones also promoting specific skills essential for coping unassisted after an accidental fall effectively. Rehabilitation of individuals affected by PS should be a fully integrated service, eliminating all identified risk factors for falls. As clinical PS symptoms tend to recur after completion of a full course of therapeutic management, all PS patients should continue the pursuit of therapeutic exercises on an individual basis, to effectively retard their recurrence. In view of overall scarcity of clinical studies completed on the large population samples of PS patients, further in-depth research is still required to ensure higher credence to overall efficacy of the presently proposed therapeutic solutions.

Effects of Prismatic Lenses on Lateral Axial Dystonia in Parkinson's Disease: A Pilot Study.

OBJECTIVE: In Parkinson's disease (PD), postural abnormalities such as lateral axial dystonia (LAD) are relatively common. Evidence suggests that both peripheral and central mechanisms contribute to these postural abnormalities. We previously reported an improvement in LAD following the use of prisms in two PD patients. Here, we further investigate the effects of prismatic lenses in a case series of nine patients with PD and LAD. METHODS: Nine patients underwent an orthoptic evaluation and were provided with prismatic lenses. Patients were evaluated at baseline and after one and three months of permanent prismatic lens use and again re-evaluated one month after the discontinuation of prismatic lens use. RESULTS: We found a linear relationship between disease duration and LAD severity. Compared to basal measurements, we observed a slight improvement in LAD. Furthermore, we found a significant reduction in self-perceived back pain due to the use of prismatic lenses. There was no significant association between the individual effects of prismatic lenses in patients with PD and their baseline LAD or other clinical and demographic features (all P>0.05). CONCLUSION: The present pilot study provides novel data on the possible effectiveness of prismatic lenses for LAD treatment in PD patients.

«El convento de las monjas torcidas». Síndrome de Pisa y camptocormia inducido por antipsicóticos / “The bent nuns convent”. Antipsycotic-induced Pisa Syndrome and Camptocormia

La camptocormia y el sídrome de Pisa (pleurothotonus) se caracteriza por una postura anormal en el tronco, con una flexión de la columna toracolumbar de entre 15-45° durante la bipedestación y la marcha que se corrige completamente con el decúbito supino. Se asocia a la enfermedad de Parkinson y a otras enfermedades neurodegenerativas, siendo su fisiopatología incierta. Se presentan 3 casos de camptocormia secundaria a antipsicóticos atípicos (AU)

Camptocormia is an involuntary flexion between 15-45° of the thoracolumbar spine when standing, walking or sitting, which disappears completely in the supine position. Is associated to Parkinson's disease and other neurodegenerative conditions, being its physiopatology unknown. We report three cases of atypical anti-psychotic induced camptocormia (AU)

Contribution of Basal Ganglia to the Sense of Upright: A Double-Blind Within-Person Randomized Trial of Subthalamic Stimulation in Parkinson's Disease with Pisa Syndrome.

BACKGROUND: Verticality perception is frequently altered in Parkinson's disease (PD) with Pisa syndrome (PS). Is it the cause or the consequence of the PS? OBJECTIVE: We tested the hypothesis that both scenarios coexist. METHODS: We performed a double-blind within-person randomized trial (NCT02704910) in 18 individuals (median age 63.5 years) with PD evolving for a median of 17.5 years and PS for 2.5 years and treated with bilateral stimulation of the subthalamus nuclei (STN-DBS) for 6.5 years. We analyzed whether head and trunk orientations were congruent with the visual (VV) and postural (PV) vertical, and whether switching on one or both sides of the STN-DBS could modulate trunk orientation via verticality representation. RESULTS: The tilted verticality perception could explain the PS in 6/18 (33%) patients, overall in three right-handers (17%) who showed net and congruent leftward trunk and PV tilts. Two of the 18 (11%) had an outstanding clinical picture associating leftward: predominant parkinsonian symptoms, whole-body tilt (head -11°, trunk -8°) and transmodal tilt in verticality perception (PV -10°, VV -8.9°). Trunk orientation or VV were not modulated by STN-DBS, whereas PV tilts were attenuated by unilateral or bilateral stimulations if it was applied on the opposite STN. CONCLUSION: In most cases of PS, verticality perception is altered by the body deformity. In some cases, PS seems secondary to a biased internal model of verticality, and DBS on the side of the most denervated STN attenuated PV tilts with a quasi-immediate effect. This is an interesting track for further clinical studies.