Three-axis Modification of Coordinates Enables Accurate Stereotactic Targeting in Non-human Primate Brains of Different Sizes

The brain grows with age in non-human primates (NHPs). Therefore, atlas-based stereotactic coordinates cannot be used directly to target subcortical structures if the size of the animal's brain differs from that used in the stereotactic atlas. Furthermore, growth is non-uniform across different cortical regions, making it difficult to simply apply a single brain-expansion ratio. We determined the skull reference lines that best reflect changes in brain size along the X, Y, and Z axes and plotted the changes in reference-line length against the changes in body weight. The skull reference lines had a linear relationship with body weight. However, comparison of skull reference lines with body weight confirmed the non-uniform skull growth during postnatal development, with skull growth more prominent in the X and Y axes than the Z axis. Comparing the differences between the atlas-based lengths and those calculated empirically from plot-based linear fits, we created craniometric indices that can be used to modify stereotactic coordinates along all axes. We verified the accuracy of the corrected stereotactic targeting by infusing dye into internal capsule in euthanized and preserved NHP brains. Our axis-specific, craniometric-index-adjusted stereotactic targeting enabled us to correct for targeting errors arising from differences in brain size. Histological verification showed that the method was accurate to within 1 mm. Craniometric index-adjusted targeting is a simple and relatively accurate method that can be used for NHP stereotactic surgery in the general laboratory, without the need for high-resolution imaging.

Experiencia inicial en biopsias mamarias bajo guía mamográfica digital con sistema de vacío / Initial experience with vacuum assisted breast biopsies under stereotactic guidance

Objetivos Describir la experiencia inicial en el uso de un sistema de biopsia por vacío con guía estereotáxica digital para lesiones mamarias. Material y método Se evaluaron retrospectivamente las biopsias bajo estereotaxia mamográfica con sistema de vacío (bav) realizadas en el Centro de Imagenología Mamaria (imad) de la ciudad de Bahía Blanca desde marzo de 2016 a julio de 2017. En el período analizado, se recibieron 329 pedidos de punción, de los cuales 112 correspondieron a biopsias bajo estereotaxia mamográfica con sistema de vacío y 217 a biopsias bajo ecografía. Se realizaron 99/112 (89%) bav, no pudiéndose completar el procedimiento en 13/112 (11%) de los casos. Resultados Se obtuvieron los siguientes resultados patológicos: 20% (20/99) Maligno, 7% (7/99) Alto riesgo y 73% (72/99) Benigno. Se produjeron complicaciones leves que no requirieron ningún tipo de tratamiento posterior en el 8% de los casos: 7/99 reacción vasovagal y 1/99 dolor que dificultó el procedimiento, aunque en todos los casos se pudo finalizar el mismo. Conclusiones Se diagnosticaron lesiones malignas o de alto riesgo en el 27% de los procedimientos realizados.

Objectives To describe our initial experience with vacuum assisted breast biopsies under stereotactic guidance for non-palpable lesions. Materials and method We retrospectively review the vacuum assisted breast biopsies performed at Centro de Imagenología Mamaria (imad) between march 2016 and july 2017. 329 patients requested a breast biopsy. Of them, 112 were vacuum assisted biopsies under stereotactic guidance and 217 were ultrasound guided. We succesfully completed 99/112 (89%) of vacuum assisted biopsies, not being able to reach the target in the remaining 11%. Results The following pathological results were obtained: 20% (20/99) Malignant, 7% (7/99) High risk and 73% (72/99) Benign lesions. Minor complications, which did not require any further treatment, occurred in 8% of cases: 7/99 vasovagal reactions, 1/99 pain during the procedure. Conclusions Malignant and high-risk lesions were diagnosed in 27% of the procedures performed.

Sistema auxiliar para colocar el marco estereotactico en el craneo / Auxiliary system for positioning the stereotactic frame to the skull

En neurocirugía funcional y radioneurocirugía estereotáctica, la fijación de un marco en el cráneo, permite el establecimiento de un sistema tridimensional de coordenadas, para localizar y definir con precisión los objetivos en el cerebro. El montaje se basa en la experiencia y la percepción visual del médico, pero los resultados son subjetivos y la calibración de las coordenadas del marco con respecto al cráneo no siempre es la óptima para el desarrollo del procedimiento quirúrgico. Este estudio evalúa la eficacia y la funcionalidad de un sistema auxiliar diseñado para colocar el marco estereotáctico en el cráneo. La evaluación se realiza por medio de un estudio comparativo de dos grupos de 7 pacientes cada uno sometidos a tratamiento de radioneurocirugía. En el primer grupo no es utilizado el sistema, solo en el segundo, se tomaron 165 imágenes (IRM) en promedio por cada estudio. El empleo del sistema auxiliar disminuye la variación de la inclinación y la rotación del marco con respecto al cráneo hasta un 64%, la apreciación subjetiva del médico es sustituida por una medición objetiva, obteniéndose certidumbre al posicionar el marco sobre el cráneo. Los resultados muestran que el sistema auxiliar diseñado es eficaz y funcional.

In functional neurosurgery and stereotactic radioneurosurgery, the fixation of a frame to the skull allows the establishment of a three-dimensional coordinate system, to locate and precisely defined objectives in the brain. The montage is based on experience and visual perception the doctor, the results obtained and the calibration of the coordinates of the frame with respect to the skull is not always the optimal for developing the surgical procedure. This study evaluates the effectiveness and functionality of an auxiliary system designed to collocate the stereotactic frame to the skull. The evaluation is done by means of a comparative study of two groups of 7 patients each underwent radioneurosurgery treatment. The first group is not using the system, only in the second, were performed on average 165 images (MRI) for each study. The use of auxiliary system reduces the variation of the inclination and rotation of the frame with respect to the skull by 64%, the subjective appreciation the doctor is substituted by an objective measure, thus obtaining certainty to position the frame on the skull. The results show that the auxiliary system designed is effective and functional.

Resección endoscópica guiada por estereotaxia de un neurocitoma pineal: reporte de un caso / Guided stereotactic endoscopic resection of a pineal neurocytoma: a case report

El neurocitoma debe considerarse en el diagnóstico diferencial de los tumores pineales. La éxeresis quirúrgica total es esencial, y se puede realizar a través de diferentes abordajes: trans-cerebeloso, transcallosal, transcortical-Transventricular. La cirugía con puerto cerebral (brain port) es un abordaje quirúrgico que combina la resección endoscópica guiada por estereotaxia delesiones expansivas intraventriculares. Este proceder es una técnica mínimamente invasiva y es capaz de lograr la resección tumoral con mínimo daño al tejido nervioso. Reportamos un caso con un neurocitoma pineal, una paciente femenina de 29 años, Que debutó con hipertensión intracraneal secundaria a hidrocefalia obstructiva. Se logró la exéresis quirúrgica mediante brain port sin complicaciones. Los marcadores tumorales previos a la cirugía fueron negativos. El índice MIB-1 fue menor a un 4 por ciento y durante un año de seguimiento no se ha demostrado recidiva tumoral. La cirugía brain-port es una técnica segura para el abordaje a tumores de región pineal.

Neurocytoma should be considered in the differential diagnosis of pineal tumours. Total surgical resection is essential, through different approaches: transcortical-transventricular, transcallosal and transcerebellar. Brain port surgery is a surgical approach that combines endoscopic resection via stereotactic guide in intraventricular mass. This procedure is a minimally invasive technique and it is able to achieve tumour resection with minimal nervous tissue damage. We report a case with a pineal neurocytoma, a 29 years old female patient with symptoms of intracranial hypertension secondary to obstructive hydrocephalus. Total removal was done with brain port surgery without complications. Tumoral markers (AFP, CEA, HCG-ß) performed previously to surgery were negative. MIB-1 index was less than 4 percent and patient’s follow-up during one year after surgery didn’t show recurrence. Brain port surgery is considered as a safe technique to approach pineal region tumours.

Cerebral biopsy: comparison between frame-based stereotaxy and neuronavigation in an oncology center / Biópsia cerebral: comparação entre estereotaxia com arco e neuronavegação em um centro de oncologia

Treatment of intracranial tumoral lesions is related to its correct histological diagnostic. We present a retrospective analysis of 32 patients submitted to 36 cerebral biopsies using neuronavigation and 44 patients using frame-based stereotaxy. Mean age was 46.6 and 49.3 years old respectively. Sex distribution in both groups was 50 percent for each. Most of lesions were lobar in both groups. Diagnostic yielding was 91.7 percent and 83.4 percent, respectively (p=0.26). We found in the postoperative CT scans intracranial hemorrhages in 13.8 percent cases of the first group and 9.8 percent cases in the second. Most of them were mild post-operative hemorrages in the biopsy site. There was one death related to the procedure in each group. Astrocytomas and metastatic adenocarcinomas were the most frequent diagnosis. Diagnostic yielding and the number of postoperative hemorrhage and death were similar on both groups and the same found in the literature.

O manejo das lesões intracranianas tumorais está relacionado ao seu diagnóstico histológico adequado. Foi realizado estudo retrospectivo com 32 pacientes submetidos a 36 biópsias cerebrais por neuronavegação e 44 pacientes por estereotaxia com arco. A idade média foi 46,6 e 49,3 anos respectivamente. Nos dois grupos a distribuição por sexo foi 50 por cento para cada. A maioria das lesões biopsiadas eram lobares nos dois grupos. A positividade diagnóstica foi 91,7 por cento para neuronavegação e 83,4 por cento para a estereotaxia com arco, respectivamente (p=0,26). Identificou-se hemorragia intracraniana na TC pós-operatória em 13,8 por cento dos casos no primeiro grupo e em 9,8 por cento no segundo, a maioria de pequena monta sem provocar piora neurológica. Ocorreu uma morte relacionada ao procedimento em cada grupo. Os diagnósticos mais freqüentes foram astrocitomas e adenocarcinomas metastáticos. A positividade diagnóstica, taxas de hemorragia pós-operatória e de mortalidade foram equiparáveis estatisticamente entre os dois métodos e se assemelham com as descritas na literatura.

Stereotactic biopsies of brain lesions / Biópsia estereotáxica de lesões encefálicas

OBJECTIVE: In the majority of cases, the correct treatment of brain lesions is possible only when the histopathological diagnosis is made. Several deep-seated lesions near eloquent areas are not safely approached by the classical neurosurgical procedures. These patients can get benefit by a minimally invasive procedure. METHOD: We present a series of 176 consecutive patients submitted to stereotactic biopsies due to a great variety of brain lesions. RESULTS: Histological diagnosis found in this series: glioma in 40.1 percent of the patients, other neoplasms in 12.2 percent and infectious or inflammatory diseases in 29.1 percent. The result was inconclusive in 5.2 percent of the procedures. One patient died (0.6 percent) and two (1.2 percent) presented operative complications. The criteria, advantages and risks of the stereotactic biopsies are discussed. CONCLUSION: The efficacy of the method is adequate and morbid-mortality rates were low.

OBJETIVO: O diagnóstico anatomopatológico das lesões encefálicas é muitas vezes necessário para a instituição do tratamento adequado. Entretanto, muitas lesões localizadas profundamente no encéfalo ou em centros nervosos de grande importância funcional não podem ser acessadas sem riscos, com a aplicação dos procedimentos neurocirúrgicos habituais. MÉTODO: Apresentamos uma série de 176 doentes submetidos a biópsias estereotáxicas de lesões encefálicas. RESULTADOS: Em 40,1 por cento dos casos, o diagnóstico foi de glioma, em 12,2 por cento de outras neoplasias e em 29,1 por cento, de doenças infecciosas ou inflamatórias. O resultado foi inconclusivo em 5,2 por cento dos doentes. Um (0,6 por cento) doente faleceu e dois (1,2 por cento) apresentaram graves complicações operatórias. Os critérios de seleção, as vantagens e os riscos da biópsia estereotáxica são discutidos. CONCLUSÃO: A eficácia do método é boa e a morbimortalidade das biópsias estereotáxicas é baixa.

Even in Patients with a Small Hemorrhagic Volume, Stereotactic-Guided Evacuation of Spontaneous Intracerebral Hemorrhage Improves Functional Outcome

OBJECTIVE: The decision to adopt a conservative or surgical modality for a relatively small volume of spontaneous intracerebral hemorrhage (SICH) is difficult and often controversial, especially when consciousness is tolerable. The authors examined the results of stereotactic-guided evacuation of SICH for relatively small volumes with respect to functional outcome. METHODS: This prospective study was performed on 387 patients with SICH who underwent stereotactic-guided evacuation (n = 204, group A) or conservative treatment (n = 183, group B) during the past 8 years. The primary end-point was recovery of functional status, which was estimated using the Modified Barthel Index (MBI) and the modified Rankin Scale (mRS). RESULTS: All patients had a Glasgow coma scale (GCS) score of > or = 13 and unilateral hemiparesis of less than motor power grade 3. Group demographic characteristics and initial neurological statuses were similar. In all cases, the volume of SICH involved was < 30 cm3 and location was limited to basal ganglia and thalamus. At 6-month follow-ups, MBI was 90.9 in group A and 62.4 in group B (p < 0.05), and MRS was 1.2 in group A and 3.0 in group B (p < 0.05). Better motor function and stereotactic-guided evacuation had a significant effect on a functional recovery in regression analyses. CONCLUSION: Even in patients with a small volume of SICH, stereotactic-guided evacuation improved functional recovery in activities in daily life than conservative treatment did.

Cortical Localization of Scalp Electrodes on Three-Dimensional Brain Surface Using Frameless Stereotactic Image Guidance System

BACKGROUND: The purpose of this study was to localize the cortical regions reflected by overlying scalp electrodes. METHODS: We enrolled 10 patients with epilepsy (5 males, mean age 29.7 years old). Thin slice coronal T1 weighted MR images were obtained and then scalp EEG electrodes were placed based on an international 10-20 system. Cortical locations of scalp electrodes were determined using a real-time frameless stereotactic image guidance system, Brainsight(R). RESULTS: The locations of 19 scalp electrodes were marked on the 3D rendered cortical surface of one representative patient's MRI; Fp1 (Fp2) on the anterior pole of the middle frontal gyrus, Fz on the mid-point of the interhemispheric fissure in the frontal lobe, F3 (F4) on the mid-portion of the middle frontal gyrus, F7 (F8) on the pars triangularis of the inferior frontal gyrus, Cz on the interhemispheric fissure where a lateral precentral gyrus starts, C3 (C4) scattered around postcentral gyrus, T3 (T4) on the middle temporal gyrus, P3 (P4) on the angular gyrus, Pz on the mid-point of the interhemispheric fissure in the parietal lobe, T5 (T6) on the posterior part of the inferior temporal gyrus, and O1 (O2) on the occipital pole. CONCLUSIONS: The locations of scalp electrodes were well correlated with conventional concepts of their cortical locations. The individual differences of the scalp electrode locations may be due to the different sizes and morphologies of the brains in each of the patients. Real time cortical localization of scalp electrodes using the Frameless Stereotactic Image Guidance System may provide useful information for more accurate localization of focal cerebral activity in partial epilepsy patients.

Radiocirugía psiquiátrica con Gamma Knife

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Abstract: Today, psychosurgery is a minimally invasive and highly selective treatment performed only on some patients with severe, refractory treatment, affective, anxious, or obsessive-compulsive disorders. Recent advancements in technology and functional neuroanatomy as well as economic pressures to lower the cost of caring for the chronically ill may provide an opportunity for psychosurgery to become a more attractive option in the treatment of psychiatric disease. In recent years, the rapid adoption of computer-based techniques for surgical planning and visualization and image-guided surgery have made possible a number of impressive advances in functional neurosurgery. Magnetic resonance imaging (MRI) allows for the acquisition of highly detailed structural information of soft tissues in the brain. Minute pathological alterations can be visualized even before they are detected by other means. Stereotaxic atlases based on this information are now used to achieve an extraordinary precision in the placement of electrodes and probes and to plan the operation. Functional imaging is currently possible with special metabolic markers and MRI, as well as computerized techniques for the mathematical processing and visualization of images. Thus, non-invasive evaluation of brain function can be performed with extraordinary precision and sensitivity. Bloodless stereotaxic surgery without opening the skull (even the patient's head does not need to be shaved) is possible thanks to a revolutionary technique called radiosurgery. The destruction of nervous or vascular tissue inside the brain is achieved by projecting thin and powerful beams of ionizing radiation, which come from several angles around the patient's head. These beams produced by sources of radioactive cobalt (the "gamma knife" developed in the 60's by the Swedish neurosurgeon Lars Leksell). With this modality, radiation energy concentrates in a single small point inside the brain. Gamma Knife radiosurgery was first used in our country in 1996 to treat patients diagnosed with treatment-refractory psychiatric diseases. This treatment modality requires a multidisciplinary effort on the part of psychiatrists, neuropsychologists, neurologists, neurosurgeons and medical physicists. This should also be in accordance with the psychiatric neurosurgical protocol and ethics code of Medica Sur, as well as following the guidelines established by the National Nuclear Regulatory Commission and the Radiosurgery and Stereotaxic Radiotherapy Section of the Mexican College of Neurological Surgery. Ten patients have been treated with several procedures like cingulotomy, anterior capsulotomy, subcaudate tractotomy and limbic leukotomy in order to aid them in obsessive-compulsive disorder, major depression, pathological aggression, and Asperger and Tourette Syndromes. In this paper we disclose our experience with follow-ups ranging from six months to seven years in accordance with the most usual evaluation scales for mental disease and multiaxial evaluation framework of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). In our cases, the most common indications have been refractory obsessive-compulsive disorder (OCD), pathologic aggression and major depression after at least two years of treatment and with the involvement of at least two psychiatrists. According to the basal diagnosis, psychological tests are used by the neuropsychology specialist from our group and /or the neuropsychologists who have given medical treatment along with the psychiatrists. Six males and four females were treated with an age range of 13 to 52 years, and an average age of 28.2 years. The first patient had impulsive disorder and hetero-aggression, with a history of two bilateral prefrontal lobotomies with no stereotaxic planning and without a good response. The patient had gamma radiosurgery with bilateral anterior capsulotomy and continued his antipsychotic treatment. For two years, the patient had a good response and was able to go back to his wife and mother. After those two years, he developed a hypersexuality syndrome that led to a divorce from his wife and the patient was lost to clinical follow-up. The second patient was an adolescent with corpus callosum lipoma and hetero-aggression and compulsive syndrome refractory to medical treatment including carbamazepine levels above the therapeutic level. Three persons had to continuously watch him at home during 24 hours a day. He had a history of bilateral stereotaxic cingulotomy with thermocoagulation without a good response. Under general anesthesia, a gamma bilateral stereotaxic capsulotomy was performed. After 2 months of latency period and three years of follow-up, the hetero-aggression has been under control. Carbamazepine treatment is still used. The third patient had physical hetero-aggression towards his parents for more than seven years. He underwent gamma radiosurgery for bilateral capsulotomy and after a latency period of three months and a three year follow-up the patient has had no aggression episodes. The fourth patient had hetero-aggression since his teenage years, with a course of more than 6 years of this disorder and major depression with suicidal attempts. He had an electroconvulsive therapy session that led to a minor improvement lasting 2 months. Gamma radiosurgery was used for a limbic leukotomy in the cingula and the anterior arm of the internal capsules. His aggressiveness has significantly improved and his depression has been fluctuating under medical supervision. The patient has anxiety crisis that the patient's mother helps to control by giving him marijuana. The fifth patient had OCD of more than 10 years of course and a predominance of contamination fobias and bleeding hands because of frequent washing. She was treated with bilateral gamma capsulotomy and after two months of latency she stopped using gloves and after two years of follow-up the fobias have disappeared and has been able to work with no limitations in a company office. The sixth adolescent patient is the son of a neurosurgeon colleague and has symptoms of hetero and self-aggression, impulsivity and destructive behavior associated with mental retardation. The patient underwent a bilateral anterior capsulotomy under general anesthesia. The suggested treatment protocol was to combine the procedure with bilateral limbic leukotomy and hypothalamic procedure in a second surgical stage to control the self-aggression outbreaks. The patient had significant improvement of his impulsivity during the first two months and before the end of his minimum latency period of 6 to 8 months developed a zone of radionecrosis. He had an open cingulotomy after five months of radiosurgery in another hospital and his current clinical course is unknown. The seventh patient with Asperger and Tourette syndrome and impulsivity and hetero-aggression had a bilateral anterior gamma capsulotomy with significant improvement and after one year of follow-up he had a less severe clinical recurrence and underwent bilateral gamma cingulotomy to complete limbic leukotomy. He has early shown improvement but his follow-up is only two months. The eighth patient had schizophrenic disorder displayed as impulsivity crisis, obsessive ideas and hetero-aggression towards his family fluctuating with periods of depression. He had a limbic leukotomy and has good control of his aggression and is still under medical treatment as most of the patients are. The nineth patient in the series had major depression, suicidal attempts and chronic anxiety refractory to medical treatment. She was operated two years before and had a bilateral capsulotomy by thermocoagulation and because her clinical picture prevailed, she had bilateral anterior capsulotomy with gamma knife. In her six month follow-up, her anxiety has improved, and she has had no new major depression crisis and her follow-up neuropsychological tests are pending to be made in her home town.

Comparative Study on Frameless Stereotactic Hematoma Aspiration versus Frame-Based Stereotactic Hematoma Aspiration in Deep Seated Intracerebral Hemorrhage: A Clinical Article / 대한뇌혈관외과학회지

OBJECTIVE: We compare the frameless stereotactic hematoma aspiration (FSA) with frame-based stereotactic hematoma aspiration (FBSA) in intracerebral hemorrhage (ICH) about operative advantage and result. MATERIAL AND METHODS: Between January 2002 and December 2002, we surgically treated 30 patients presenting with spontaneous ICH at our hospital. 15 patients underwent FBSA via Codman-Roberts-Wells system and catheter placement with urokinase infusion and drainage, and 15 patients underwent FSA and catheter placement via neuronavigator with urokinase infusion and drainage. RESULTS: The amount of remaining hematoma and removal rate were from 1 to 26 and 76% in FSA and from 2 to 55 and 60.4% in FBSA. The entry point was selected within 2.03+/-0.85 cm in a frontal direction from Kocher's point and 2.86+/-0.57 cm in lateral direction from Kocher's point and the trajectory was selected toward the distal margin of hematoma along the long axis of hematoma in FSA but the entry point was restricted within Kocher's point and the trajectory was selected toward the center of the maximum axial section of hematoma in FBSA. The mean time of operative preparation was mean 61 minutes in FSA and 78 minutes in FBSA. The number of patients not required with infusion of urokinase was 10 in FSA and 7 in FBSA. The mean duration of urokinase infusion was 3.6 day in FSA and 4.1 day in FBSA. CONCLUSION: FSA is fast, simple and effective procedure. In comparison with FBSA, FSA has advantage in selecting the entry point and the trajectory for hematoma aspiration and catheter placement, and in a less time-consuming procedure.

Biopsia cerebral a mano alzada guiada por tomografía / Cerebral biopsy by a handfree procedure

Se presenta la experiencia del Servicio de Neurocirugía del Hospital Universitario San Vicente de Paúl con un procedimiento alternativo para realizar una biopsia cerebral, el cual se lleva a cabo a mano alzada y guiado por tomografía sin utilizar un marco estereotáxico. Se resalta su utilidad en los casos de lesiones supratentoriales y con tamaño mayor de 3 centímetros, en centros donde no se disponga de los métodos estereotáxicos tradicionales.

Clinical Application of Frameless Stereotaxy "Viewing Wand": Its Usefulness and Limitation

The Viewing Wand is a frameless stereotactic device to provide image-based intraoperative navigation, allowing accurate neurosurgical planning and procedures. The authors applied the frameless stereotactic device called "ISG Viewing Wand" to 30 cases of intracranial lesions and evaluated for its usefulness and limitation. The Viewing Wand was used in 3 cases in conjunction with CT and 27 cases with MRI. The actual error of this system after the registration was judged by the operating surgeon to be less than 2mm in CT or MR image. The useful registrations were possible in 25(83%) out of 30 cases. But it was not useful in 5 cases, because of movement of fiducial markers in 2 cases and head movement after registration in 3 cases. In 25 cases having useful registration, the wand was helpful to localize the lesion for designing the scalp incision and bone flap, as well as the extent of surgical resection of lesions. As a whole, the viewing wand was found to be reliable and accurate. The system is a useful navigational aid that allows a direct approach to intracranial pathology without the drawbacks of application and the limitations of a frame-based stereotactic device.

Stereotaxy in Brain Abscess

Despite a reduction in the mortality of patients with brain abscess since the introduction antibiotics and computed tomography controversy persists as to the preferred method of treatment for this condition. Twenty two patients were treated by CT or MRI guided stereotactic aspiration or excision with appropriate antibiotic therapy. Thirteen patients who were treated by aspiration recieved a total of 6 to 8 weeks of antibiotic therapy. Eight patients who were treated by excision recieved a total of 1 to 2 weeks of antibiotic therapy. One patient was managed with biopsy followed by antibiotic therapy, but due to increase in size of abscess, open craniotomy was performed. Stereotaxy is a procedure with minimal morbidity and mortality. It should be considered in patients with small, multiple, or deep-seated abscesses, in those who are poor operative candidates, and in those who have failed prior therapy. Stereotactic excision may be considered in patients with small(< 20mm) superficially located abscesses.

The electrophysiological characteristics of ventralis intermedius nucleus and its role in localizations of Vim-thalamotomy for Parkinson's disease patients / 解放军医学杂志

Objective To investigate the electrophysiological characteristics of the ventralis intermedius nucleus (Vim) in order to find an easy and safe way to confirm the target in Vim-thalamotomy. Method In microelectrode-guided selective Vim-thalamotomy for 23 Parkinson's disease patients, the background activity, amplitude and discharge frequencies of Vim were compared with its surrounding structures. The response of kinesthetic neuron and tremor cell to microstimulation was also compared. Result There were differences in backgroud activity and discharge amplitude for Vim, ventralis lateralis nucleus (VL), ventralis caudalis nucleus (VC), and internal capsule. Based on the response to active or passive movement of contralateral limb tremor cells were divided into two subgroups, which were different in localization. Contralateral tremor showed different response when the two subgroups of tremor cells were mircrostimulated. Conclusion The anterior border of Vim was easily found by microrecording. Only by combining microstimulation with microrecording could the posterior border of Vim and its interior and lateral ordination of target were identified exactly and safely. Kinesthetic neurons and tremor cells which responded to the movement of contralateral limbs should be destroyed.