Direct subthalamic nucleus stimulation influences speech and voice quality in Parkinson's disease patients.

BACKGROUND: DBS of the subthalamic nucleus (STN) considerably ameliorates cardinal motor symptoms in PD. Reported STN-DBS effects on secondary dysarthric (speech) and dysphonic symptoms (voice), as originating from vocal tract motor dysfunctions, are however inconsistent with rather deleterious outcomes based on post-surgical assessments. OBJECTIVE: To parametrically and intra-operatively investigate the effects of deep brain stimulation (DBS) on perceptual and acoustic speech and voice quality in Parkinson's disease (PD) patients. METHODS: We performed an assessment of instantaneous intra-operative speech and voice quality changes in PD patients (n = 38) elicited by direct STN stimulations with variations of central stimulation features (depth, laterality, and intensity), separately for each hemisphere. RESULTS: First, perceptual assessments across several raters revealed that certain speech and voice symptoms could be improved with STN-DBS, but this seems largely restricted to right STN-DBS. Second, computer-based acoustic analyses of speech and voice features revealed that both left and right STN-DBS could improve dysarthric speech symptoms, but only right STN-DBS can considerably improve dysphonic symptoms, with left STN-DBS being restricted to only affect voice intensity features. Third, several subareas according to stimulation depth and laterality could be identified in the motoric STN proper and close to the associative STN with optimal (and partly suboptimal) stimulation outcomes. Fourth, low-to-medium stimulation intensities showed the most optimal and balanced effects compared to high intensities. CONCLUSIONS: STN-DBS can considerably improve both speech and voice quality based on a carefully arranged stimulation regimen along central stimulation features.

Deep brain stimulation of the anterior nucleus of the thalamus increases slow wave activity in non-rapid eye movement sleep.

OBJECTIVE: Previous studies suggest that intermittent deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) affects physiological sleep architecture. Here, we investigated the impact of continuous ANT DBS on sleep in epilepsy patients in a multicenter crossover study in 10 patients. METHODS: We assessed sleep stage distribution, delta power, delta energy, and total sleep time in standardized 10/20 polysomnographic investigations before and 12 months after DBS lead implantation. RESULTS: In contrast to previous studies, we found no disruption of sleep architecture or alterations of sleep stage distribution under active ANT DBS (p = .76). On the contrary, we observed more consolidated and deeper slow wave sleep (SWS) under continuous high-frequency DBS as compared to baseline sleep prior to DBS lead implantation. In particular, biomarkers of deep sleep (delta power and delta energy) showed a significant increase post-DBS as compared to baseline (36.67 ± 13.68 µV2 /Hz and 799.86 ± 407.56 µV2 *s, p < .001). Furthermore, the observed increase in delta power was related to the location of the active stimulation contact within the ANT; we found higher delta power and higher delta energy in patients with active stimulation in more superior contacts as compared to inferior ANT stimulation. We also observed significantly fewer nocturnal electroencephalographic discharges in DBS ON condition. In conclusion, our findings suggest that continuous ANT DBS in the most cranial part of the target region leads to more consolidated SWS. SIGNIFICANCE: From a clinical perspective, these findings suggest that patients with sleep disruption under cyclic ANT DBS could benefit from an adaptation of stimulation parameters to more superior contacts and continuous mode stimulation.

Information flows from hippocampus to auditory cortex during replay of verbal working memory items.

The maintenance of items in working memory (WM) relies on a widespread network of cortical areas and hippocampus where synchronization between electrophysiological recordings reflects functional coupling. We investigated the direction of information flow between auditory cortex and hippocampus while participants heard and then mentally replayed strings of letters in WM by activating their phonological loop. We recorded local field potentials from the hippocampus, reconstructed beamforming sources of scalp EEG, and - additionally in four participants - recorded from subdural cortical electrodes. When analyzing Granger causality, the information flow was from auditory cortex to hippocampus with a peak in the [4 8] Hz range while participants heard the letters. This flow was subsequently reversed during maintenance while participants maintained the letters in memory. The functional interaction between hippocampus and the cortex and the reversal of information flow provide a physiological basis for the encoding of memory items and their active replay during maintenance.

Every day, the brain's ability to temporarily store and recall information ­ called working memory ­ enables us to reason, solve complex problems or to speak. Holding pieces of information in working memory for short periods of times is a skill that relies on communication between neural circuits that span several areas of the brain. The hippocampus, a seahorse-shaped area at the centre of the brain, is well-known for its role in learning and memory. Less clear, however, is how brain regions that process sensory inputs, including visual stimuli and sounds, contribute to working memory. To investigate, Dimakopoulos et al. studied the flow of information between the hippocampus and the auditory cortex, which processes sound. To do so, various types of electrodes were placed on the scalp or surgically implanted in the brains of people with drug-resistant epilepsy. These electrodes measured the brain activity of participants as they read, heard and then mentally replayed strings of up to 8 letters. The electrical signals analysed reflected the flow of information between brain areas. When participants read and heard the sequence of letters, brain signals flowed from the auditory cortex to the hippocampus. The flow of electrical activity was reversed while participants recalled the letters. This pattern was found only in the left side of the brain, as expected for a language related task, and only if participants recalled the letters correctly. This work by Dimakopoulos et al. provides the first evidence of bidirectional communication between brain areas that are active when people memorise and recall information from their working memory. In doing so, it provides a physiological basis for how the brain encodes and replays information stored in working memory, which evidently relies on the interplay between the hippocampus and sensory cortex.

Bilateral Focused Ultrasound Pallidotomy for Parkinson-Related Facial Dyskinesia-A Case Report.

Background: For safety reasons, both magnetic resonance-guided high-intensity focused ultrasound (MRgHiFUS) thalamotomy and pallidotomy are currently approved exclusively for unilateral treatment, but axial symptoms like levodopa-induced orofacial dyskinesia require a bilateral approach. Objectives: We report the first case of successful bilateral MRgHiFUS pallidotomy for peak-dose dyskinesia in a patient with Parkinson's disease (PD). Methods: The treatment decision was based on the patient's reluctance toward brain implants and pump therapies and the fact that he had limited access to a deep brain stimulation center in his home country. The treatment was planned as staged procedure with an interval of 18 months because of travel restrictions because of the coronavirus disease (COVID)-19 pandemic. Results: After the second treatment, levodopa-induced orofacial dyskinesia remitted and improved bradykinesia and rigidity with stable gait and good postural reflexes. Conclusions: This promising result suggests that in selected PD patients with dyskinesia, staged bilateral MRgHiFUS pallidotomy might be considered.

Consensus Statement on High-Intensity Focused Ultrasound for Functional Neurosurgery in Switzerland.

Background: Magnetic resonance-guided high-intensity focused ultrasound (MRgHiFUS) has evolved into a viable ablative treatment option for functional neurosurgery. However, it is not clear yet, how this new technology should be integrated into current and established clinical practice and a consensus should be found about recommended indications, stereotactic targets, patient selection, and outcome measurements. Objective: To sum up and unify current knowledge and clinical experience of Swiss neurological and neurosurgical communities regarding MRgHiFUS interventions for brain disorders to be published as a national consensus paper. Methods: Eighteen experienced neurosurgeons and neurologists practicing in Switzerland in the field of movement disorders and one health physicist representing 15 departments of 12 Swiss clinical centers and 5 medical societies participated in the workshop and contributed to the consensus paper. All experts have experience with current treatment modalities or with MRgHiFUS. They were invited to participate in two workshops and consensus meetings and one online meeting. As part of workshop preparations, a thorough literature review was undertaken and distributed among participants together with a list of relevant discussion topics. Special emphasis was put on current experience and practice, and areas of controversy regarding clinical application of MRgHiFUS for functional neurosurgery. Results: The recommendations addressed lesioning for treatment of brain disorders in general, and with respect to MRgHiFUS indications, stereotactic targets, treatment alternatives, patient selection and management, standardization of reporting and follow-up, and initialization of a national registry for interventional therapies of movement disorders. Good clinical evidence is presently only available for unilateral thalamic lesioning in treating essential tremor or tremor-dominant Parkinson's disease and, to a minor extent, for unilateral subthalamotomy for Parkinson's disease motor features. However, the workgroup unequivocally recommends further exploration and adaptation of MRgHiFUS-based functional lesioning interventions and confirms the need for outcome-based evaluation of these approaches based on a unified registry. MRgHiFUS and DBS should be evaluated by experts familiar with both methods, as they are mutually complementing therapy options to be appreciated for their distinct advantages and potential. Conclusion: This multidisciplinary consensus paper is a representative current recommendation for safe implementation and standardized practice of MRgHiFUS treatments for functional neurosurgery in Switzerland.

Deep brain stimulation for locomotion in incomplete human spinal cord injury (DBS-SCI): protocol of a prospective one-armed multi-centre study.

INTRODUCTION: Spinal cord injury (SCI) is a devastating condition with immediate impact on the individual's health and quality of life. Major functional recovery reaches a plateau 3-4 months after injury despite intensive rehabilitative training. To enhance training efficacy and improve long-term outcomes, the combination of rehabilitation with electrical modulation of the spinal cord and brain has recently aroused scientific interest with encouraging results. The mesencephalic locomotor region (MLR), an evolutionarily conserved brainstem locomotor command and control centre, is considered a promising target for deep brain stimulation (DBS) in patients with SCI. Experiments showed that MLR-DBS can induce locomotion in rats with spinal white matter destructions of >85%. METHODS AND ANALYSIS: In this prospective one-armed multi-centre study, we investigate the safety, feasibility, and therapeutic efficacy of MLR-DBS to enable and enhance locomotor training in severely affected, subchronic and chronic American Spinal Injury Association Impairment Scale C patients in order to improve functional recovery. Patients undergo an intensive training programme with MLR-DBS while being regularly followed up until 6 months post-implantation. The acquired data of each timepoint are compared with baseline while the primary endpoint is performance in the 6-minute walking test. The clinical trial protocol was written in accordance with the Standard Protocol Items: Recommendations for Interventional Trials checklist. ETHICS AND DISSEMINATION: This first in-man study investigates the therapeutic potential of MLR-DBS in SCI patients. One patient has already been implanted with electrodes and underwent MLR stimulation during locomotion. Based on the preliminary results which promise safety and feasibility, recruitment of further patients is currently ongoing. Ethical approval has been obtained from the Ethical Committee of the Canton of Zurich (case number BASEC 2016-01104) and Swissmedic (10000316). Results will be published in peer-reviewed journals and presented at conferences. TRIAL REGISTRATION NUMBER: NCT03053791.

Peroral Trigeminal Rhizotomy Using a Novel 3-Dimensional Printed Patient-Specific Guidance Tool.

BACKGROUND: Ganglion Gasseri rhizotomy is a viable therapeutic option for trigeminal pain (TP). For this neurosurgical procedure, different potential operative and technical nuances exist. OBJECTIVE: To evaluate a novel peroral trigeminal rhizotomy method and 3-dimensional printed patient-specific guidance tool (3D-PSGT) with respect to their applicability and safety. METHODS: Between March 2018 and February 2021, 20 peroral balloon compression rhizotomy procedures with a 3D-PSGT were performed in 18 consecutive TP patients (13 female, mean age 58 yr). We registered the procedure duration, side effects, complications, and trigeminal function. The therapeutic effect was gauged from reduction of TP and use of analgesics. RESULTS: All catheter insertions and rhizotomy procedures were successful at the first attempt. Apart from fluoroscopy, no auxiliary material was necessary. The average length of surgery was 19 min (range, 11-27 min). In total, 8 patients indicated complete analgesia and 6 patients pain relief; in 4 patients, persistence of TP was observed during follow-up examinations of up to 20 mo. In total, 6 patients reported of new mild to moderate facial hypesthesia affecting the trigeminal branches V2, V3, or V1-3. No masticatory musculature or corneal affections and device-related complications occurred. CONCLUSION: The peroral 3D-PSGT trigeminal rhizotomy is straightforward for the neurosurgeon. This operative approach allows for rapid, safe, and simple foramen ovale cannulation in TP patients and reduces the use of additional equipment, radiation exposure, and procedure time.

Mobile intraoperative CT-assisted frameless stereotactic biopsies achieved single-millimeter trajectory accuracy for deep-seated brain lesions in a sample of 7 patients.

BACKGROUND: Brain biopsies are crucial diagnostic interventions, providing valuable information for treatment and prognosis, but largely depend on a high accuracy and precision. We hypothesized that through the combination of neuronavigation-based frameless stereotaxy and MRI-guided trajectory planning with intraoperative CT examination using a mobile unit, one can achieve a seamlessly integrated approach yielding optimal target accuracy. METHODS: We analyzed a total of 7 stereotactic biopsy trajectories for a variety of deep-seated locations and different patient positions. After rigid head fixation, an intraoperative pre-procedural scan using a mobile CT unit was performed for automatic image fusion with the planning MRI images and a peri-procedural scan with the biopsy cannula in situ for verification of the definite target position. We then evaluated the radial trajectory error. RESULTS: Intraoperative scanning, surgery, computerized merging of MRI and CT images as well as trajectory planning were feasible without difficulties and safe in all cases. We achieved a radial trajectory deviation of 0.97 ± 0.39 mm at a trajectory length of 60 ± 12.3 mm (mean ± standard deviation). Repositioning of the biopsy cannula due to inaccurate targeting was not required. CONCLUSION: Intraoperative verification using a mobile CT unit in combination with frameless neuronavigation-guided stereotaxy and pre-operative MRI-based trajectory planning was feasible, safe and highly accurate. The setting enabled single-millimeter accuracy for deep-seated brain lesions and direct detection of intraoperative complications, did not depend on a dedicated operating room and was seamlessly integrated into common stereotactic procedures.

A stereotactic frame-based drill guide-aided setting for laser interstitial thermal therapy.

BACKGROUND: Magnetic resonance imaging (MRI)-guided laser interstitial thermal therapy (MRIgLITT) was demonstrated to be a viable neurosurgical tool. Apart from its variety of indications, different operative and technical nuances exist. In the present report, for the first time, the use and ability of a traditional Riechert-Mundinger (RM) stereotactic system combined with a novel drill guide kit for MRIgLITT are described. METHODS: A stereotactic frame-based setting was developed by combining an RM system with a drill guide kit and centering bone anchor screwing aid for application together with an MRIgLITT neuro-accessory kit and cooled laser applicator system. The apparatus was used for stereotactic biopsy and consecutive MRIgLITT with an intraoperative high-field MRI scanner in a brain tumor case. RESULTS: The feasibility of an RM stereotactic apparatus and a drill guide kit for MRIgLITT was successfully assessed. Both stereotactic biopsy and subsequent MRIgLITT in a neurooncological patient could easily and safely be performed. No technical problems or complications were observed. CONCLUSION: The combination of a traditional RM stereotactic system, a new drill guide tool, and intraoperative high-field MRI provides neurosurgeons with the opportunity to reliably confirm the diagnosis by frame-based biopsy and allows for stable and accurate real-time MRIgLITT.

Deep brain electrical neurofeedback allows Parkinson patients to control pathological oscillations and quicken movements.

Parkinsonian motor symptoms are linked to pathologically increased beta-oscillations in the basal ganglia. While pharmacological treatment and deep brain stimulation (DBS) reduce these pathological oscillations concomitantly with improving motor performance, we set out to explore neurofeedback as an endogenous modulatory method. We implemented real-time processing of pathological subthalamic beta oscillations through implanted DBS electrodes to provide deep brain electrical neurofeedback. Patients volitionally controlled ongoing beta-oscillatory activity by visual neurofeedback within minutes of training. During a single one-hour training session, the reduction of beta-oscillatory activity became gradually stronger and we observed improved motor performance. Lastly, endogenous control over deep brain activity was possible even after removing visual neurofeedback, suggesting that neurofeedback-acquired strategies were retained in the short-term. Moreover, we observed motor improvement when the learnt mental strategies were applied 2 days later without neurofeedback. Further training of deep brain neurofeedback might provide therapeutic benefits for Parkinson patients by improving symptom control using strategies optimized through neurofeedback.

A prospective international multi-center study on safety and efficacy of deep brain stimulation for resistant obsessive-compulsive disorder.

Deep brain stimulation (DBS) has been proposed for severe, chronic, treatment-refractory obsessive-compulsive disorder (OCD) patients. Although serious adverse events can occur, only a few studies report on the safety profile of DBS for psychiatric disorders. In a prospective, open-label, interventional multi-center study, we examined the safety and efficacy of electrical stimulation in 30 patients with DBS electrodes bilaterally implanted in the anterior limb of the internal capsule. Safety, efficacy, and functionality assessments were performed at 3, 6, and 12 months post implant. An independent Clinical Events Committee classified and coded all adverse events (AEs) according to EN ISO14155:2011. All patients experienced AEs (195 in total), with the majority of these being mild (52% of all AEs) or moderate (37%). Median time to resolution was 22 days for all AEs and the etiology with the highest AE incidence was 'programming/stimulation' (in 26 patients), followed by 'New illness, injury, condition' (13 patients) and 'pre-existing condition, worsening or exacerbation' (11 patients). Sixteen patients reported a total of 36 serious AEs (eight of them in one single patient), mainly transient anxiety and affective symptoms worsening (20 SAEs). Regarding efficacy measures, Y-BOCS reduction was 42% at 12 months and the responder rate was 60%. Improvements in GAF, CGI, and EuroQol-5D index scores were also observed. In sum, although some severe AEs occurred, most AEs were mild or moderate, transient and related to programming/stimulation and tended to resolve by adjustment of stimulation. In a severely treatment-resistant population, this open-label study supports that the potential benefits outweigh the potential risks of DBS.

[Movement Disorders: What Are You Doing? What Can We Do?] / Bewegungsstörungen: Was machen Sie? Was können wir?

Movement Disorders: What Are You Doing? What Can We Do? Abstract. Disturbances of movement are common and varied. Frequent causes are systemic diseases such as Parkinson's syndromes and the essential tremor. Treatment options in practice and hospital include conservative, predominantly drug strategies such as oral administration of dopamine precursors or agonists, and pharmacological or non-pharmacological escalation strategies such as intramuscular botulinum toxin A injections, the subcutaneous or enteral drug pumps for apomorphine or levodopa and carbidopa, the effective deep brain stimulation and the novel focused ultrasound therapy, which are bound to highly specialized centers and should be considered as treatment option quite earlier and more frequently.

Tremor analysis with wearable sensors correlates with outcome after thalamic deep brain stimulation.

INTRODUCTION: Thalamic deep brain stimulation (DBS) provides excellent tremor control in most patients with essential tremor (ET). However, not all tremor patients show clinically significant improvement after DBS surgery. Currently, there is no reliable clinical or instrument-based measure to predict how patients respond to DBS. Therefore, we set out to provide a method for tremor outcome prediction prior to surgery. METHODS: We retrospectively analysed quantitative tremor data collected with inertial measurement units (IMU) in 13 patients who underwent DBS surgery in the ventral intermediate nucleus of the thalamus (VIM). All patients were diagnosed with either ET or ET-plus according to current diagnostic criteria of the movement disorder society. We used linear and logistic regression models to evaluate the influence of different tremor characteristics on tremor outcome. RESULTS: We found that the ratio between the amplitude of the first overtone and the amplitude of the fundamental frequency, denoted as the Harmonic Index, has a significant influence on tremor reduction after DBS surgery. This measure shows a strong correlation with the post-operative improvement of tremor outcome based on the Whiget Tremor Rating Scale. CONCLUSION: Based on these findings, we propose a novel approach to predict tremor outcome after DBS surgery. Quantitative tremor assessment adds to the preoperative prediction of DBS response and might therefore have a relevant clinical impact in the management of patients suffering from pharmacoresistant tremor.

sEVD-smartphone-navigated placement of external ventricular drains.

BACKGROUND: Currently, the trajectory for insertion of an external ventricular drain (EVD) is mainly determined using anatomical landmarks. However, non-assisted implantations frequently require multiple attempts and are associated with EVD malpositioning and complications. The authors evaluated the feasibility and accuracy of a novel smartphone-guided, angle-adjusted technique for assisted implantations of an EVD (sEVD) in both a human artificial head model and a cadaveric head. METHODS: After computed tomography (CT), optimal insertion angles and lengths of intracranial trajectories of the EVDs were determined. A smartphone was calibrated to the mid-cranial sagittal line. Twenty EVDs were placed using both the premeasured data and smartphone-adjusted insertion angles, targeting the center of the ipsilateral ventricular frontal horn. The EVD positions were verified with post-interventional CT. RESULTS: All 20 sEVDs (head model, 8/20; cadaveric head, 12/20) showed accurate placement in the ipsilateral ventricle. The sEVD tip locations showed a mean target deviation of 1.73° corresponding to 12 mm in the plastic head model, and 3.45° corresponding to 33 mm in the cadaveric head. The mean duration of preoperative measurements on CT data was 3 min, whereas sterile packing, smartphone calibration, drilling, and implantation required 9 min on average. CONCLUSIONS: By implementation of an innovative navigation technique, a conventional smartphone was used as a protractor for the insertion of EVDs. Our ex vivo data suggest that smartphone-guided EVD placement offers a precise, rapidly applicable, and patient-individualized freehand technique based on a standard procedure with a simple, cheap, and widely available multifunctional device.

Patients with a Normal Pressure Hydrocephalus Shunt Have Fewer Complications than Do Patients with Other Shunts.

BACKGROUND: Ventriculoperitoneal (VP) shunting is a well-established therapy for hydrocephalus. However, complications are frequent. The incidence of idiopathic normal pressure hydrocephalus (NPH) increases with the aging of the population. We evaluated the functional status of patients and the classification of complications associated with VP shunt procedures in our center. METHODS: We recorded all VP shunt procedures in our prospective patient registry from January 2013 to December 2015. Functional outcome (Karnofsky Performance Status [KPS] and modified Rankin Scale) and complications were compiled from patient records. Any deviation from the normal postoperative course within 3 months after surgery was considered a complication. Complications were classified with the therapy-oriented Clavien-Dindo grading system. We evaluated potential risk factors with a logistic regression model. RESULTS: From 285 procedures in the reporting period, 90 were excluded, resulting in 195 patients. Among those patients, 174 (90%) were shunt implantations and 21 (11%) were shunt revisions. Forty-four shunts (23%) were implanted for NPH. Median KPS improved over the first year after surgery. Although some type of complication was observed in 114 patients (58%), 60 of those complications (31%) did not require surgical treatment (Clavien-Dindo grade <3). In 50 patients (26%), the complication concerned the shunt itself. A high KPS at admission and NPH as underlying indication significantly reduced the odds ratio for a complication. CONCLUSIONS: Although shunt surgery has a high general rate of complications, this rate is significantly lower for patients with NPH. The decision for shunting in patients with NPH should consider the low complication rate specific for the group of patients with NPH.

UniversitätsSpital Zürich: 80 years of neurosurgical patient care in Switzerland.

BACKGROUND: The predecessor of today's Department of Neurosurgery, UniversitätsSpital Zürich (USZ), was founded 80 years ago as the first independent Swiss clinic dedicated to neurosurgical patient care. On the occasion of this anniversary, we aimed to highlight the history of neurosurgery as a specialty at the USZ, and to put it into the historical context of Swiss and European Neurosurgery. METHOD: A literature review was conducted and we searched the archives of the USZ and the city of Zurich, as well as those of Swiss journals to extract relevant published articles, books, historical reports and pictures. The USZ Department of Medical History, the Museum of Medical History and the Swiss National Library were contacted to provide source material. To further verify the content, (emeritus) faculty from the USZ and external experts on the history of Swiss neurosurgery reviewed the manuscript. RESULTS: Surgeries of the head and spine had occasionally been conducted in Zurich by the general surgeons, Rudolf Ulrich Krönlein and Paul Clairmont, before an independent neurosurgical clinic was founded by Hugo Krayenbühl on 6 July 1937. This was the first Swiss department dedicated to neurosurgical patient care. Besides providing high-quality medicine for both the local and wider population, the department was chaired by eminent leaders of neurosurgery, who influenced the scientific and clinical neurosurgery of their time. As such, it has long been regarded as one of the top teaching and research hospitals in Switzerland and in Europe. CONCLUSIONS: On the occasion of its 80th anniversary, we have performed an in-depth review of its development, successes and challenges, with a special focus on the early decades. Reflecting on the past, we have identified common denominators of success in neurosurgery that remain valid today.

Shunt age-related complications in adult patients with suspected shunt dysfunction. A recommended diagnostic workup.

BACKGROUND: Patients admitted for suspicion of shunt dysfunction (SD) often show unspecific symptoms and require time-consuming, expensive and even invasive diagnostics involving significant radiation exposure. The purpose of this retrospective study was to analyse the current diagnostic procedures and to propose a process optimisation. METHOD: As all patients admitted for suspicion of SD receive imaging studies, we searched for adult patients receiving neuroimaging in the period from January 2010 to July 2013, analysing referring diagnosis, clinical signs, products, diagnostic process and final diagnosis. Recursive partitioning was used to define time intervals for differentiating types of SD. RESULTS: A total of 148 patients, aged 18-89 (mean, 54) years, were studied. Forty-two percent were referred by a hospital or rehabilitation centre, 30% by general practitioners and 24% were self-referrals. The admission diagnosis was in the majority "shunt dysfunction" only. Further differentiations were rarely made. An SD was confirmed in 46% of the patients. In 17%, the symptoms were based on another cause and in 37% they could not be clearly attributed to any specific disorder. Abdominal dislocations (2%) and shunt infections (5%) were found within the first 6 months. Over- (3%) and under-drainage (14%) were the most frequent complications during the first 4 years. Disconnections (13%) occurred generally 4 years or more after implantation. Only shunt obstruction (9%) showed no temporal pattern. CONCLUSIONS: Symptoms of SD remain mostly unspecific. This study showed that the type of SD depends on the time interval from implantation. We propose a workup strategy for patients with SD based on the temporal profile.