Stereotactic surgery in India: the past, present and the future.
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The achievements of Indian neurosurgeons in different fields of stereotactic surgery over the past decades have been discussed. This covers diverse areas like Parkinson's disease, abnormal movements, cerebral palsy, spasticity, pain relief, and sedative and functional neurosurgery. Recently, technological advances have made stereotactic surgery useful in many fields like deep biopsies, minimally invasive surgery and radiosurgery. Apart from these areas, there is still a big scope for revival of surgery on deep structures of the brain, as was practised earlier. This will lead to newer knowledge about brain function and also give relief to many patients. The future is bright, provided Indian neurosurgeons show a paradigm shift in their thinking and bring out new ideas. Interaction with other scientific disciplines is necessary in the future if new knowledge has to be added or new techniques have to be devised. (+info)
Stereotactic computed tomographic-guided aspiration and thrombolysis of intracerebral hematoma : protocol and preliminary experience.
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BACKGROUND AND PURPOSE: We review preliminary experience with patients harboring intracerebral hematoma (ICH) treated by stereotactic computed tomographic (CT) guided thrombolysis and aspiration and assess procedure feasibility and safety. METHODS: Twelve patients with supratentorial ICH >/=25 mL without suspected underlying structural etiology or coagulopathy and an initial Glasgow Coma Scale (GCS) score of >/=5 were treated. A catheter was directed stereotactically or manually into the ICH through a burr hole under CT guidance. Hematoma aspiration was followed by instillation of urokinase (5 000 to 10 000 IU). This was repeated every 6 to 8 hours at bedside, with interval CT imaging, until the ICH volume diminished to <25 mL, less than half of its initial volume, or after a maximum of 10 aspirations/instillations. RESULTS: Mean age was 69 years (range 55 to 82 years). Median initial GCS was 12 (range 5 to 14). There were 7 ganglionic and 5 lobar ICH, and baseline hematoma size ranged 29 to 70 mL (mean 46 mL). Final ICH volume ranged from 14 to 51 mL (mean 21 mL), with ICH volume reduction by an average of 57% (range 38% to 70%). One patient (8. 3%) suffered hematoma expansion during the procedure. At 6 months after the procedure, 3 patients (25%) had achieved a good recovery (Glasgow Outcome Scale [GOS] score of 5), 5 patients (42%) were dependent (GOS 3), and 1 (8.3%) remained vegetative (GOS 2). Three patients (25%) died in hospital (1 from cardiac arrhythmia and 2 from respiratory failure). CONCLUSIONS: CT-guided thrombolysis and aspiration appears safe and effective in the reduction of ICH volume. Further studies are needed to assess optimal thrombolytic dosage and must include controlled comparisons of mortality, disability outcome, time until convalescence, and cost of care in treated and untreated patients. (+info)
Convergent properties of vestibular-related brain stem neurons in the gerbil.
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Three classes of vestibular-related neurons were found in and near the prepositus and medial vestibular nuclei of alert or decerebrate gerbils, those responding to: horizontal translational motion, horizontal head rotation, or both. Their distribution ratios were 1:2:2, respectively. Many cells responsive to translational motion exhibited spatiotemporal characteristics with both response gain and phase varying as a function of the stimulus vector angle. Rotationally sensitive neurons were distributed as Type I, II, or III responses (sensitive to ipsilateral, contralateral, or both directions, respectively) in the ratios of 4:6:1. Four tested factors shaped the response dynamics of the sampled neurons: canal-otolith convergence, oculomotor-related activity, rotational Type (I or II), and the phase of the maximum response. Type I nonconvergent cells displayed increasing gains with increasing rotational stimulus frequency (0.1-2.0 Hz, 60 degrees /s), whereas Type II neurons with convergent inputs had response gains that markedly decreased with increasing translational stimulus frequency (0.25-2.0 Hz, +/-0.1 g). Type I convergent and Type II nonconvergent neurons exhibited essentially flat gains across the stimulus frequency range. Oculomotor-related activity was noted in 30% of the cells across all functional types, appearing as burst/pause discharge patterns related to the fast phase of nystagmus during head rotation. Oculomotor-related activity was correlated with enhanced dynamic range compared with the same category that had no oculomotor-related response. Finally, responses that were in-phase with head velocity during rotation exhibited greater gains with stimulus frequency increments than neurons with out-of-phase responses. In contrast, for translational motion, neurons out of phase with head acceleration exhibited low-pass characteristics, whereas in-phase neurons did not. Data from decerebrate preparations revealed that although similar response types could be detected, the sampled cells generally had lower background discharge rates, on average one-third lower response gains, and convergent properties that differed from those found in the alert animals. On the basis of the dynamic response of identified cell types, we propose a pair of models in which inhibitory input from vestibular-related neurons converges on oculomotor neurons with excitatory inputs from the vestibular nuclei. Simple signal convergence and combinations of different types of vestibular labyrinth information can enrich the dynamic characteristics of the rotational and translational vestibuloocular responses. (+info)
Parietal neurons represent surface orientation from the gradient of binocular disparity.
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In order to elucidate the neural mechanisms involved in the perception of the three-dimensional (3D) orientation of a surface, we trained monkeys to discriminate the 3D orientation of a surface from binocular disparity cues using a Go/No-go type delayed-matching-to-sample (DMTS) task and examined the properties of the surface-orientation-selective (SOS) neurons. We recorded 57 SOS neurons from the caudal part of the lateral bank of the intraparietal sulcus (area CIP) of three hemispheres of two Japanese monkeys (Macaca fuscata). We tested 29 of 57 SOS neurons using the square plate of a solid figure stereogram (SFS) and random-dot stereogram (RDS) without perspective cues; almost all of the tested neurons (28/29) showed surface orientation selectivity for the SFS and/or the RDS without perspective cues. Eight of these 28 neurons (28.6%) showed selectivity for both the RDS and SFS, 7 (25.0%) were dominantly selective for the RDS, and 13 (46.4%) were dominantly selective for the SFS. These results suggest that neurons that show surface orientation tuning for the RDS without perspective cues compute surface orientation from the gradient of the binocular disparity given by the random-dot across the surface. On the other hand, neurons that show surface orientation tuning for the SFS without perspective cues may represent surface orientation primarily from the gradient of the binocular disparity along the contours. In conclusion, the SOS neurons in the area CIP are likely to operate higher order processing of disparity signals for surface perception by integrating the input signals from many disparity-sensitive neurons with different disparity tuning. (+info)
Potent and nontoxic antisense oligonucleotides containing locked nucleic acids.
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Insufficient efficacy and/or specificity of antisense oligonucleotides limit their in vivo usefulness. We demonstrate here that a high-affinity DNA analog, locked nucleic acid (LNA), confers several desired properties to antisense agents. Unlike DNA, LNA/DNA copolymers were not degraded readily in blood serum and cell extracts. However, like DNA, the LNA/DNA copolymers were capable of activating RNase H, an important antisense mechanism of action. In contrast to phosphorothioate-containing oligonucleotides, isosequential LNA analogs did not cause detectable toxic reactions in rat brain. LNA/DNA copolymers exhibited potent antisense activity on assay systems as disparate as a G-protein-coupled receptor in living rat brain and an Escherichia coli reporter gene. LNA-containing oligonucleotides will likely be useful for many antisense applications. (+info)
A high-resolution fast spin-echo inversion-recovery sequence for preoperative localization of the internal globus pallidus.
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A fast spin-echo inversion-recovery (FSE-IR) sequence is described for its utility regarding surgical planning for patients with Parkinson's disease (PD) who are undergoing microelectrode-guided internal globus pallidus (GPi) ablation. Images from thirty-seven adult patients with PD were reviewed and visualization of the GPi, globus pallidus externa (GPe), and the intervening lamina was noted. High-resolution images were acquired from all patients despite the external hardware and the patients' movement disorder. In all cases, the conventional surgical trajectory, determined indirectly by a fixed measurement from the anteroposterior commissure line, was modified by the ability to visualize the GPi and optic tract directly. This sequence facilitated accurate stereotactic targeting. (+info)
Human anterior cingulate cortex neurons modulated by attention-demanding tasks.
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Recent imaging studies have implicated the anterior cingulate cortex (ACC) in various cognitive functions, including attention. However, until now, there was no evidence for changes in neuronal activity of individual ACC neurons during performance of tasks that require attention and effortful thought. We hypothesized these neurons must exist in the human ACC. In this study, we present electrophysiological data from microelectrode single neuron recordings in the human ACC of neuronal modulation during attention-demanding tasks in 19% of 36 neurons tested. These findings provide the first direct evidence of an influence of a cognitive state on the spontaneous neuronal activity of human ACC neurons. (+info)
Eye movements in Parkinson's disease: before and after pallidotomy.
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PURPOSE: To evaluate the effects of unilateral, stereotactic, posteroventral pallidotomy on saccadic eye movements in patients with Parkinson disease (PD). METHODS: Eye movements of 31 patients with moderate to advanced PD were recorded with an infrared system 1 month before and 3 months after pallidotomy. Two kinds of saccade tasks were used: saccade tasks for eliciting visually guided saccades and saccade tasks for eliciting internally mediated saccades (memory-guided, predictive, and anti-saccades). Latency, accuracy, peak velocity, and other parameters of saccades were evaluated. RESULTS: Internally mediated saccades were more impaired in patients with advanced PD compared with those with moderate PD. Pallidotomy did not affect visually guided saccades. After pallidotomy, the peak saccadic velocity of internally mediated saccades decreased. CONCLUSIONS: Hence, although pallidotomy has led to improvements in other motor functions, none were observed in saccadic responses. Rather, several modest decrements, below the level of clinical significance and all in internally mediated saccades, were observed. (+info)