[Artificial intelligence in neurosurgery]. / Künstliche Intelligenz in der Neurochirurgie.

BACKGROUND: Artificial intelligence (AI) in neurosurgery is becoming increasingly more important as the technology advances. This development can be measured by the increase of publications on AI in neurosurgery over the last years. OBJECTIVE: This article provides insights into the current possibilities of using AI in neurosurgery. MATERIAL AND METHODS: A review of the literature was carried out with a focus on exemplary work on the use of AI in neurosurgery. RESULTS: The current neurosurgical publications on the use of AI show the diversity of the topic in this field. The main areas of application are diagnostics, outcome and treatment models. CONCLUSION: The various areas of application of AI in the field of neurosurgery with a refined preoperative diagnostics and outcome predictions will significantly influence the future of neurosurgery. Neurosurgeons will continue to make the decisions on the indications for surgery but an optimized statement on diagnosis, treatment options and on the risk of surgery will be made by neurosurgeons with the help of AI in the future.

Brain stimulation in obesity.

Obesity is taking up epidemic proportions worldwide with significant impacts on the health of both the affected individual and on society as a whole. Treatment approaches consist of behavioural and pharmacological approaches, however, these are often found to be ineffective. In severe obesity, bariatric surgery is frequently performed. Unfortunately, 40% of patients show substantial weight gain over the long term or display the associated metabolic syndrome, making the development of novel therapies necessary. This review summarizes some of the current conceptual models, in particularly the 'food addiction' model, and then discusses specific therapeutic targets of brain stimulation, both non-invasive (transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS) and transcutaneous vagus nerve stimulation (VNS)) and invasive (deep brain stimulation and invasive VNS). As we will show, neuromodulatory approaches represent a promising tool for targeting specific brain structures implicated in the pathophysiology of obesity. Non-invasive techniques such as TMS, tDCS and transcutaneous VNS need further investigation before they may become ready for clinical usage. The currently available study data suggest that deep brain stimulation may become an effective and acceptable therapy for otherwise treatment-resistant obese patients. The results of the currently undergoing clinical trials are eagerly awaited.

Biochemical mechanisms of pallidal deep brain stimulation in X-linked dystonia parkinsonism.

OBJECTIVE: Invasive techniques such as in-vivo microdialysis provide the opportunity to directly assess neurotransmitter levels in subcortical brain areas. METHODS: Five male Filipino patients (mean age 42.4, range 34-52 years) with severe X-linked dystonia-parkinsonism underwent bilateral implantation of deep brain leads into the internal part of the globus pallidus (GPi). Intraoperative microdialysis and measurement of gamma aminobutyric acid and glutamate was performed in the GPi in three patients and globus pallidus externus (GPe) in two patients at baseline for 25/30 min and during 25/30 min of high-frequency GPi stimulation. RESULTS: While the gamma-aminobutyric acid concentration increased in the GPi during high frequency stimulation (231 ± 102% in comparison to baseline values), a decrease was observed in the GPe (22 ± 10%). Extracellular glutamate levels largely remained unchanged. CONCLUSIONS: Pallidal microdialysis is a promising intraoperative monitoring tool to better understand pathophysiological implications in movement disorders and therapeutic mechanisms of high frequency stimulation. The increased inhibitory tone of GPi neurons and the subsequent thalamic inhibition could be one of the key mechanisms of GPi deep brain stimulation in dystonia. Such a mechanism may explain how competing (dystonic) movements can be suppressed in GPi/thalamic circuits in favour of desired motor programs.

Diagnostic benefits of presurgical fMRI in patients with brain tumours in the primary sensorimotor cortex.

OBJECTIVES: Reliable imaging of eloquent tumour-adjacent brain areas is necessary for planning function-preserving neurosurgery. This study evaluates the potential diagnostic benefits of presurgical functional magnetic resonance imaging (fMRI) in comparison to a detailed analysis of morphological MRI data. METHODS: Standardised preoperative functional and structural neuroimaging was performed on 77 patients with rolandic mass lesions at 1.5 Tesla. The central region of both hemispheres was allocated using six morphological and three functional landmarks. RESULTS: fMRI enabled localisation of the motor hand area in 76/77 patients, which was significantly superior to analysis of structural MRI (confident localisation of motor hand area in 66/77 patients; p < 0.002). FMRI provided additional diagnostic information in 96% (tongue representation) and 97% (foot representation) of patients. FMRI-based presurgical risk assessment correlated in 88% with a positive postoperative clinical outcome. CONCLUSION: Routine presurgical FMRI allows for superior assessment of the spatial relationship between brain tumour and motor cortex compared with a very detailed analysis of structural 3D MRI, thus significantly facilitating the preoperative risk-benefit assessment and function-preserving surgery. The additional imaging time seems justified. FMRI has the potential to reduce postoperative morbidity and therefore hospitalisation time.

[Neuroablative procedures in pain therapy]. / Neurodestruktive Verfahren in der Schmerztherapie.

Although surgical ablative procedures can be effective in the management of chronic pain of malignant and non-malignant origin, they are often disregarded as treatment options due to the fact that in the past these procedures were associated with high complication rates. The complications include the development of new neurological deficits and in cases of long-term follow-up, the occurrence of the old or new pain syndromes by deafferentation. On the other hand there exist many less invasive, e.g. neuromodulatory procedures or non-invasive measures (systemic oral or transdermal opioids) which are able to considerably reduce chronic pain. Nevertheless, there remain certain very restricted indications for the use of neuroablative procedures for the treatment of chronic pain even today.

Thalamic deep brain stimulation improves eyeblink conditioning deficits in essential tremor.

Several lines of evidence point to a disturbance of olivo-cerebellar pathways in essential tremor (ET). For example, subjects with ET exhibit deficits in eyeblink conditioning, a form of associative learning which is known to depend on the integrity of olivo-cerebellar circuits. Deep brain stimulation (DBS) of the ventrolateral thalamus is an established therapy for ET. If tremor in ET is related to the same pathology of the olivo-cerebellar system as impaired eyeblink conditioning, one may expect modulation of eyeblink conditioning by DBS. Delay eyeblink conditioning was assessed in 11 ET subjects treated with DBS (ET-DBS subjects) who were studied on two consecutive days with DBS switched off (day 1) and on (day 2). For comparison, 11 age-matched ET subjects without DBS (ET subjects) and 11 age-matched healthy controls were studied. On day 1, eyeblink conditioning was diminished in ET-DBS subjects and in ET subjects compared with controls. When DBS was switched on ET-DBS subjects exhibited conditioning rates within the range of controls on day 2, while ET subjects improved only minimally. Improved eyeblink conditioning in ET-DBS subjects suggests that thalamic DBS counteracts a functional disturbance of olivo-cerebellar circuits which is thought to be responsible for eyeblink conditioning deficits in ET. Modulation of cerebello-thalamic and/or thalamo-cortico-cerebellar pathways by DBS may play a role.

[Neuromodulation in cluster headache. Clinical follow-up after deep brain stimulation in the posterior hypothalamus for chronic cluster headache, case report--Part II]. / Neuromodulation bei Clusterkopfschmerz. Klinische Verlaufsbeobachtung nach Tiefenhirnstimulation im posterioren Hypothalamus zur Behandlung des chronischen Clusterkopfschmerzes, Fallbericht--Teil II.

Deep brain stimulation (DBS) of the posterior hypothalamic area is a new treatment option for patients with refractory chronic cluster headache (CCH). A review of the literature reveals that studies based on large numbers of patients, long-term observations and controlled randomised trials are still lacking. In 2006 a case report of the first patient in Germany to be operated on to allow DBS was published, and we now present a report of this patient's course in the first 6 months after the operation; in addition, a current literature review is discussed. In July 2005 a DBS lead was placed in the left posterior hypothalamic area of this 39-year-old woman with CCH. Stimulation on demand achieved complete suppression of the cluster attacks, and the patient no longer needed medication. After about 8 months a decreasing effect of the stimulation, with only about 50% reduction of cluster attacks, and stimulation-induced side effects were observed. Neither reprogramming of the stimulation parameters nor pharmacological therapy with on-demand and long-term medication reduced the frequency or severity of CCH attacks to the level experienced in the early postoperative stage. Because of intolerable subjective side effects and tension-related pain at the site of the connection cable, in September 2006 the whole system was explanted at the patient's request.DBS in the posterior hypothalamic area is an invasive treatment option for use in cases with CCH that is refractory to any pharmacological therapy. As demonstrated by this case report, it is not possible to give a prognosis concerning its long-term efficacy: despite the initial excellent benefit there can be a reduction and even a loss of the effect of stimulation. The clinical results and long-term follow-up observations of the few cases published so far need to be evaluated in a larger multicentre trial with a double-blind study design.

[Deep brain stimulation in the posterior hypothalamus for chronic cluster headache. Case report and review of the literature]. / Tiefenhirnstimulation im posterioren Hypothalamus zur Behandlung des chronischen Clusterkopfschmerzes. Fallbericht und Literaturübersicht.

Primary chronic cluster headache (CCH) is a rare but severe pain syndrome and pathophysiological explanations are still missing. PET studies revealed activation in the hypothalamus and therefore it became a target for therapeutic deep brain stimulation (DBS). A case of a 39-year-old woman and a literature review are presented. The patient suffered from left-sided primary CCH for 14 months. The headache was resistant to any pharmacological therapy or treatment was limited by major drug side effects. Using a stereotactic approach a quadripolar lead was inserted in the left posterior hypothalamus. A test trial was performed and attack frequency, intensity, and adverse events were noted. Intraoperative test stimulation evoked typical side effects like tachycardia, diplopia and panic attacks. During the trial test a marked reduction in frequency and intensity of CCH was recorded. After 7 days the stimulation device was implanted subcutaneously. DBS with implantation of a lead in the ipsilateral inferior posterior hypothalamus is an experimental treatment option and should be offered to selected patients in a prospective controlled clinical trial. Data concerning the long-term follow-up need to be collected.

Behr syndrome variant with tremor treated by VIM stimulation.

Behr syndrome was first described in 1909 as a syndrome of heredofamilial optic atrophy, visual disturbances, nystagmus, and variable pyramidal tract signs. The syndrome has been reported in both sexes. So far, tremor has not been reported to be part of Behr Syndrome. We present the case of a 51-year-old man with a rare complicated dominant inherited cerebellar ataxia with accompanying visual loss and tremor (CICALVT) resembling a Behr Syndrome variant who suffered from advanced visual deterioration since childhood and progressive spastic paraparesis for 15 years. Furthermore, the patient presented increasing tremor of both hands for 5 years. The successful treatment of the tremor using deep brain stimulation (DBS) of the ventral intermediate thalamic nucleus (VIM) is reported. Our case indicates that deep brain stimulation of the ventral intermediate nucleus is an adequate operative intervention that can help to reduce tremor even in patients with complicated movement disorders.

[Spinal cord stimulation in Failed-Back-Surgery-Syndrome. Preliminary study for the evaluation of therapy by functional magnetic resonance imaging (fMRI)]. / Epidurale Rückenmarkstimulation bei Postnukleotomiesyndrom. Pilotstudie zur Therapieevaluation mit der funktionellen Magnetresonanztomographie (fMRT).

BACKGROUND: Spinal cord stimulation (SCS) is an effective alternative treatment in patients with chronic neuropathic pain and mainly radicular distribution. The aim of this prospective study was to investigate changes in BOLD signal with fMRI during active SCS and to correlate the results with the clinical pain intensity, measured with a visual analogue scale (VAS). PATIENTS AND METHODS: Three patients with failed back surgery syndrome were tested during the clinical trial of SCS. A first fMRI was performed with marked pain and a high VAS score. Before the second fMRI a therapeutic stimulation phase with pain reduction was carried out. RESULTS: With high pain levels SCS activated the cingulate gyrus, thalamus, prefrontal cortex, supplementary motor area and postcentral gyrus. After pain reduction, SCS did not elicit these activations in the second fMRI, using the same stimulation parameters. CONCLUSIONS: In patients with chronic neuropathic pain and high VAS levels, SCS elicited BOLD activation in the cingulate gyrus, thalamus, prefrontal cortex, and primary and secondary somatosensory area. Pain reduction by SCS resulted in a reduction of functional activity in these areas as revealed by follow-up fMRI.

Treatment of trigeminal neuralgia associated with multiple sclerosis: case report.

The incidence of trigeminal neuralgia (TN) in patients with multiple sclerosis is higher than in the general population. If pharmacologic therapy fails, invasive procedures in the gasserian ganglion are usually offered. Microvascular decompression is not routinely performed. The authors report a patient with persistent TN after repetitive trigeminal radiofrequency rhizotomy and finally successful microvascular decompression after demonstration of neurovascular compression with high-resolution MRI.

Facial expression recognition and subthalamic nucleus stimulation.

BACKGROUND: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor signs in Parkinson's disease. However, clinical studies suggest that DBS of the STN may also affect cognitive and emotional functions. OBJECTIVE: To study the impact of STN stimulation in Parkinson's disease on perception of facial expressions. RESULTS: There was a selective reduction in recognition of angry faces, but not other expressions, during STN stimulation. CONCLUSIONS: The findings may have important implications for social adjustment in these patients.

Active deep brain stimulation during MRI: a feasibility study.

The goal of this study was to evaluate the feasibility of active deep brain stimulation (DBS) during the application of standard clinical sequences for functional MRI (fMRI) in phantom measurements. During active DBS, we investigated induced voltage, temperature at the electrode tips and lead, forces on the electrode and lead, consequences of defective leads and loose connections, proper operation of the neurostimulator, and image quality. Sequences for diffusion- and perfusion-weighted imaging, fMRI, and morphologic MRI were used. The DBS electrode and lead were placed in a NaCl solution-filled phantom. The results indicate that there are severe potential hazards for patients. Strong heating, high induced voltage, and even sparking at defects in the connecting cable could be observed. However, it was demonstrated that under certain conditions, safe MR examinations during active DBS are feasible. Certain safety precautions are recommended in this report.

Differential modulation of subcortical target and cortex during deep brain stimulation.

The combination of electrical deep brain stimulation (DBS) with functional imaging offers a unique model for tracing brain circuitry and for testing the modulatory potential of electrical stimulation on a neuronal network in vivo. We therefore applied parametric positron emission tomography (PET) analyses that allow characterization of rCBF responses as linear and nonlinear functions of the experimentally modulated stimulus (variable stimulator setting). In patients with electrodes in the thalamic ventrointermediate nucleus (VIM) for the treatment of essential tremor (ET) here we show that variations in voltage and frequency of thalamic stimulation have differential effects in a thalamo-cortical circuitry. Increasing stimulation amplitude was associated with a linear raise in rCBF at the thalamic stimulation site, but with a nonlinear rCBF response in the primary sensorimotor cortex (M1/S1). The reverse pattern in rCBF changes was observed with increasing stimulation frequency. These results indicate close connectivity between the stimulated nucleus (VIM) and primary sensorimotor cortex. Likewise, stimulation parameter-specific modulation occurs at this simple interface between an electrical and a cerebral system and suggests that the scope of DBS extends beyond an ablation-like on-off effect: DBS could rather allow a gradual tuning of activity within a neuronal circuit.

[Neurosurgical therapy of facial neuralgias]. / Neurochirurgische Therapie der Gesichtsneuralgien.

INTRODUCTION: Neuralgias of the face, especially trigeminal neuralgia and glossopharyngeal neuralgia are indications for surgical interventions after failed medical therapy. In contrast to other forms of headache or atypical facial pain, where surgical measures are considered to be contraindicated, percutaneous procedures or microvascular decompression are able to produce immediate and longstanding pain relief. Careful preoperative evaluation is essential to confirm the clinical diagnosis and to rule out other causes as multiple sclerosis or tumors afflicting the cranial nerves. The following study will summarize the common surgical techniques and their role considering a mechanism-based therapy as well as document long-term results of these measures. METHODS: Between 1977 and 1997 316 thermo-controlled radiofrequency trigeminal rhizotomies (TK) and 379 microvascular decompressions (MVD) were performed in our hospital to treat trigeminal neuralgia; additional 6 MVDs for glossopharyngeal neuralgia and one MVD of the intermediate facial nerve were carried out. Questionnaires were sent out to all patients still living in 1981, 1982, 1992 and 1998. For all other patients, interviews with relatives or the general practitioners were conducted. A retrospective analysis of postoperative pain relief was performed using Kaplan-Meier curves at the latest follow-up. Additionally 80 patients underwent careful quantitative sensory testing with Von-Frey-hairs. RESULTS: 225 patients who underwent microvascular decompression and 206 with radiofrequency trigeminal rhizotomies were further analyzed. There was a 50% risk for pain recurrence two years after radiofrequency rhizotomy. On the other hand 64% of patients who underwent microvascular decompression remained painfree 20 years postoperatively. Patients with microvascular decompression without sensory deficit were painfree significantly longer than patients with postoperative hypesthesia. DISCUSSION: Etiology and pathogenesis of facial neuralgias are far from understood despite several hypotheses. Based on current models there is no explanation for the immediate pain relief especially after microvascular decompression. Some authors even discuss surgical trauma as the only cause for postoperative pain relief.

Subthalamic nucleus stimulation affects striato-anterior cingulate cortex circuit in a response conflict task: a PET study.

The subthalamic nucleus (STN) has generally been considered as a relay station within frontal-subcortical motor control circuitry. Little is known about the influence of the STN on cognitive networks. Clinical observations and studies in animals suggest that the STN participates in non-motor functions which can now be probed in Parkinson's disease patients with deep brain stimulation of the STN, allowing selective and reversible modulation of this nucleus. Using PET, we studied changes in regional cerebral blood flow (rCBF) associated with a response conflict task (Stroop task) in Parkinson's disease patients ON and OFF bilateral STN stimulation. The Stroop task requires subjects to name the font colour of colour words (e.g. "blue") printed in an incongruent colour ink (e.g. yellow). During STN stimulation, impaired task performance (prolonged reaction times) was associated with decreased activation in both right anterior cingulate cortex (ACC) and right ventral striatum. Concomitant increased activation in left angular gyrus indicative of ongoing word processing during stimulation is consistent with an impairment to inhibit habitual responses. ACC and ventral striatum are part of the ACC circuit associated with response conflict tasks. The decreased activation during STN stimulation in the ACC circuit, while response conflict processing worsened, provides direct evidence of STN modulating non-motor basal ganglia-thalamocortical circuitry. Impairment in ACC circuit function could account for the subtle negative effects on cognition induced by STN stimulation.

High frequency stimulation of the basal ganglia for the treatment of movement disorders: current status and clinical results.

High frequency stimulation of the basal ganglia has gained much interest during the last years. Based on the reevaluation of the results of functional neurosurgery for movement disorders from Leksell's group, pallidotomy as lesional procedure was the first functional operation that underwent a renaissance for the treatment of movement disorders. The work by Benabid and Siegfried who carried out thalamic high frequency stimulation to suppress tremor, the knowledge about deep brain stimulation (DBS) for the treatment of chronic pain as well as better understanding in basal ganglia physiology and the development of reliable stimulation hardware led to an increasing number of centers worldwide who currently apply high frequency DBS for different movement disorders. In the present review the current status of DBS for movement disorders is presented and the results with high frequency stimulation targeted at different brain areas are summarized.

Treatment of idiopathic trigeminal neuralgia: comparison of long-term outcome after radiofrequency rhizotomy and microvascular decompression.

OBJECTIVE: To evaluate the long-term outcome of patients after either percutaneous trigeminal rhizotomy or microvascular decompression (MVD) for idiopathic trigeminal neuralgia at a single institution. METHODS: From 1977 to 1997, 316 radiofrequency lesion procedures and 378 MVDs were performed. Questionnaires were sent to all patients who were alive in 1981, 1982, 1992, and 1998. For all other patients, interviews were conducted with their relatives and general practitioners. A retrospective comparative analysis was performed with Kaplan-Meier probability curves as of the latest follow-up date. In addition, 80 patients who underwent MVD were examined postoperatively with quantitative sensory measurements by use of von Frey hairs. RESULTS: Two hundred twenty-five patients who underwent MVD and 206 patients who underwent radiofrequency could be analyzed retrospectively in detail. Overall, there was a 50% risk for recurrence of pain 2 years after percutaneous radiofrequency rhizotomy. Conversely, 64% of patients who underwent MVD remained completely pain free 20 years postoperatively. Patients without sensory impairment after MVD were pain free significantly longer than patients who experienced postoperative hypesthesia or partial rhizotomy. CONCLUSION: Because it is curative and nondestructive, MVD is considered the treatment of choice for trigeminal neuralgia in otherwise healthy people. In our study, it proved to be a more effective and long-lasting procedure for patients with typical trigeminal neuralgia than radiofrequency rhizotomy. Patients without postoperative sensory deficit remained pain free significantly longer, which is a strong argument against the "trauma" hypothesis of this procedure.

Thalamic stimulation for essential tremor activates motor and deactivates vestibular cortex.

BACKGROUND: The functional effects of deep brain stimulation in the nucleus ventralis intermedius (VIM) of the thalamus on brain circuitry are not well understood. The connectivity of the VIM has so far not been studied functionally. It was hypothesized that VIM stimulation would exert an effect primarily on VIM projection areas, namely motor and parietoinsular vestibular cortex. METHODS: Six patients with essential tremor who had electrodes implanted in the VIM were studied with PET. Regional cerebral blood flow was measured during three experimental conditions: with 130 Hz (effective) and 50 Hz (ineffective) stimulation, and without stimulation. RESULTS: Effective stimulation was associated with regional cerebral blood flow increases in motor cortex ipsilateral to the side of stimulation. Right retroinsular (parietoinsular vestibular) cortex showed regional cerebral blood flow decreases with stimulation. CONCLUSIONS: Beneficial effects of VIM stimulation in essential tremor are associated with increased synaptic activity in motor cortex, possibly due to nonphysiologic activation of thalamofrontal projections or frequency-dependent neuroinhibition. Retroinsular regional cerebral blood flow decreases suggest an interaction of VIM stimulation on vestibular-thalamic-cortical projections that may explain dysequilibrium, a common and reversible stimulation-associated side effect.

Comparison of intraoperative MR imaging and 3D-navigated ultrasonography in the detection and resection control of lesions.

OBJECT: The authors undertook a study to compare two intraoperative imaging modalities, low-field magnetic resonance (MR) imaging and a prototype of a three-dimensional (3D)-navigated ultrasonography in terms of imaging quality in lesion detection and intraoperative resection control. METHODS: Low-field MR imaging was used for intraoperative resection control and update of navigational data in 101 patients with supratentorial gliomas. Thirty-five patients with different lesions underwent surgery in which the prototype of a 3D-navigated ultrasonography system was used. A prospective comparative study of both intraoperative imaging modalities was initiated with the first seven cases presented here. In 35 patients (70%) in whom ultrasonography was performed, accurate tumor delineation was demonstrated prior to tumor resection. In the remaining 30% comparison of preoperative MR imaging data and ultrasonography data allowed sufficient anatomical localization to be achieved. Detection of metastases and high-grade gliomas and intraoperative delineation of tumor remnants were comparable between both imaging modalities. In one case of a low-grade glioma better visibility was achieved with ultrasonography. However, intraoperative findings after resection were still difficult to interpret with ultrasonography alone most likely due to the beginning of a learning curve. CONCLUSIONS: Based on these preliminary results, intraoperative MR imaging remains superior to intraoperative ultrasonography in terms of resection control in glioma surgery. Nevertheless, the different features (different planes of slices, any-plane slicing, and creation of a 3D volume and matching of images) of this new ultrasonography system make this tool a very attractive alternative. The intended study of both imaging modalities will hopefully allow a comparison regarding sensitivity and specificity of intraoperative tumor remnant detection, as well as cost effectiveness.