Resultados en el tratamiento del ictus en hospitales con y sin Unidad de Ictus / Stroke treatment outcomes in hospitals with and without Stroke Units

INTRODUCCIÓN: La capacidad organizativa en términos de recursos y circuitos asistenciales que permiten acortar el tiempo de respuesta ante un nuevo caso de ictus es clave para obtener un buen resultado. En este estudio se compararon el abordaje terapéutico y los resultados del tratamiento de centros de asistencia tradicional (equipos de ictus, sin Unidad de Ictus) y con Unidad de Ictus. MÉTODOS: Estudio de tipo prospectivo, cuasiexperimental (sin aleatorización de las unidades analizadas) para realizar comparaciones entre 2 centros con Unidad de Ictus y 4 centros con atención tradicional por Neurología, sobre una selección de indicadores consensuados para monitorizar la calidad de la atención en ictus. Participaron 225 pacientes. Además, se utilizaron cuestionarios autoadministrados para recoger la valoración del servicio y la asistencia sanitaria recibida por parte de los pacientes. RESULTADOS: Los centros con Unidad de Ictus mostraron menores tiempos de respuesta tras el inicio de los síntomas, tanto al tiempo para llegar al centro, como para el diagnóstico por imagen considerando la hora de llegada del paciente al hospital. La capacidad de respuesta para aplicar tratamiento con trombólisis intravenosa fue mayor entre los hospitales con Unidad de Ictus frente a los centros con atención tradicional por Neurología. CONCLUSIÓN: Los centros con Unidad de Ictus mostraron un mejor ajuste a los estándares de tiempos de respuesta de referencia en el ictus, calculados en el estudio Quick frente a los centros con atención tradicional por Neurología

INTRODUCTION: Organisational capacity in terms of resources and care circuits to shorten response times in new stroke cases is key to obtaining positive outcomes. This study compares therapeutic approaches and treatment outcomes between traditional care centres (with stroke teams and no stroke unit) and centres with stroke units. METHODS: We conducted a prospective, quasi-experimental study (without randomisation of the units analysed) to draw comparisons between 2 centres with stroke units and 4 centres providing traditional care through the neurology department, analysing a selection of agreed indicators for monitoring quality of stroke care. A total of 225 patients participated in the study. In addition, self-administered questionnaires were used to collect patients' evaluations of the service and healthcare received. RESULTS: Centres with stroke units showed shorter response times after symptom onset, both in the time taken to arrive at the centre and in the time elapsed from patient's arrival at the hospital to diagnostic imaging. Hospitals with stroke units had greater capacity to respond through the application of intravenous thrombolysis than centres delivering traditional neurological care. CONCLUSION: Centres with stroke units showed a better fit to the reference standards for stroke response time, as calculated in the Quick study, than centres providing traditional care through the neurology department

Stroke treatment outcomes in hospitals with and without Stroke Units. / Resultados en el tratamiento del ictus en hospitales con y sin Unidad de Ictus.

INTRODUCTION: Organisational capacity in terms of resources and care circuits to shorten response times in new stroke cases is key to obtaining positive outcomes. This study compares therapeutic approaches and treatment outcomes between traditional care centres (with stroke teams and no stroke unit) and centres with stroke units. METHODS: We conducted a prospective, quasi-experimental study (without randomisation of the units analysed) to draw comparisons between 2 centres with stroke units and 4 centres providing traditional care through the neurology department, analysing a selection of agreed indicators for monitoring quality of stroke care. A total of 225 patients participated in the study. In addition, self-administered questionnaires were used to collect patients' evaluations of the service and healthcare received. RESULTS: Centres with stroke units showed shorter response times after symptom onset, both in the time taken to arrive at the centre and in the time elapsed from patient's arrival at the hospital to diagnostic imaging. Hospitals with stroke units had greater capacity to respond through the application of intravenous thrombolysis than centres delivering traditional neurological care. CONCLUSION: Centres with stroke units showed a better fit to the reference standards for stroke response time, as calculated in the Quick study, than centres providing traditional care through the neurology department.

[Stroke-psychosis. Description of two cases]. / Psicosis ictal. Descripción de dos casos.

INTRODUCTION: The presence of neuropsychiatry symptoms (hallucinations, delusions and agitation) as stroke-related guideline symptoms, thus forming an acute psychosis of organic cause, are extremely uncommon and often correlate with strategic infarcts (caudate nucleus, striatum and thalamus). CLINICAL CASE: We report two cases of stroke-psychosis. Case 1. A 67-year-old man with sudden-onset delusions of persecution and complete recovery in three months. The brain magnetic resonance imaging (MRI) revealed infarctions in both head of the caudate nucleus and body of right caudate nucleus. Case 2. A 49-year old man with sudden-onset delusions of persecution and gustative hallucinations that disappeared in three months. The brain MRI revealed small infarction in the left thalamus. DISCUSSION: The possible vascular origin of the psychosis in both cases (sudden onset, complete recover, demonstration of acute ischemic lesion in strategic territory) and the underlying psychopathogenic mechanism (dysfunction of prefrontal cortico-subcortical circuits) is discussed.

Psicosis ictal. Descripción de dos casos / Stroke-psychosis. Description of two cases

Introducción. La presencia de manifestaciones neuropsiquiátricas (alucinaciones, ideación delirante, agitación psicomotriz) como síntomas guías de un evento vascular, configurando por tanto una psicosis aguda de causa orgánica es excepcional en la práctica clínica y obedece mayoritariamente a infartos estratégicos (caudado, estriado, tálamo).Caso clínico. Se presentan dos casos de psicosis ictal. Caso 1. Varón de 67 años de edad con ideación delirante de perjuicio de instauración brusca y remisión completa en el plazo de 3 meses. La RM cerebral demostró isquemia a nivel de ambas cabezas de núcleo caudado y cuerpo de caudado derecho. Caso 2. Varón de 49 años de edad con ideación delirante de perjuicio y alucinaciones gustativas de instauración brusca y remisión completa en 3 meses. En la RM cerebral se objetivó infarto lacunar talámico izquierdo. Discusión. Se discute el probable origen vascular de la psicosis en ambos casos (instauración brusca, recuperación completa, demostración de lesión isquémica aguda en territorio estratégico) así como el mecanismo fisiopatogénico subyacente (disfunción de los circuitos prefrontales córtico-subcorticales) (AU)

Introduction. The presence of neuropsychiatry symptoms (hallucinations, delusions and agitation) as stroke-related guideline symptoms, thus forming an acute psychosis of organic cause, are extremely uncommon and often correlate with strategic infarcts (caudate nucleus, striatum and thalamus). Clinical case. We report two cases of stroke-psychosis. Case 1. A 67 year-old man with sudden-onset delusions of persecution and complete recovery in three months. The brain magnetic resonance imaging (MRI) revealed infarctions in both head of the caudate nucleus and body of right caudate nucleus. Case 2. A 49 year-old man with sudden-onset delusions of persecution and gustative hallucinations that disappeared in three months. The brain MRI revealed small infarction in the left thalamus. Discussion. The possible vascular origin of the psychosis in both cases (sudden onset, complete recover, demonstration of acute ischemic lesion in strategic territory) and the underlying psychopathogenic mechanism (dysfunction of prefrontal cortico-subcortical circuits) is discussed (AU)

[Migraine-like headache secondary to pituitary macroadenoma]. / Seudomigraña secundaria a macroadenoma hipofisario.

INTRODUCTION: Differential diagnosis of migraine-like headache with and without aura needs to proceed with neuroimaging evaluation in order to rule out any secondary conditions. We report a patient with a 2 year history of migraine like headache with a good response to ergotics and due to pituitary macroadenoma. CLINICAL CASE: A 44 year old man with no familiar history of migraine presented to our hospital because of campimetric failure and a change of his migrainous features. The patient started with migraine without aura 2 years ago and was well treated with ergotics from the beginning. Field testing showed a bitemporal hemianopsia. Magnetic resonance imaging revealed an unknown pituitary macroadenoma. CONCLUSION: Pituitary macroadenoma must be included in the differential diagnosis of migraine headache although the presence of aura or the good response to ergotics.

Seudomigraña secundaria a macroadenoma hipofisario / Migraine-like headache secondary to pituitary macroadenoma

Introducción. El diagnóstico diferencial de la cefalea de características migrañosas con o sin aura requiere la realización de una prueba de neuroimagen para descartar un origen secundario del cuadro. Presentamos el caso de un paciente con crisis seudomigrañosas de 2 años de evolución con buena respuesta a ergóticos secundarias a macroadenoma de hipófisis. Caso clínico. Paciente varón de 44 años de edad sin antecedentes familiares de migraña que ingresa por disminución del campo visual de instauración progresiva y modificación en el patrón de su cefalea. Como antecedente destaca la presencia desde hace 2 años de una o dos crisis mensuales de cefalea de características migrañosas con respuesta a ergóticos y sin aura asociada. La campimetría objetivó una hemianopsia bitemporal. Se practicó una resonancia magnética cerebral que puso de manifiesto la existencia de un macroadenoma de hipófisis no conocido. El tratamiento neuroquirúrgico del mismo se tradujo en la desaparición de dichas crisis. Conclusión. El macroadenoma de hipófisis debe ser incluido en el diagnóstico diferencial de las crisis de migraña independientemente de la presencia de aura asociada y de la respuesta a ergóticos

Introduction. Differential diagnosis of migraine-like headache with and without aura needs to proceed with neuroimaging evaluation in order to rule out any secondary conditions. We report a patient with a 2 year history of migrainelike headache with a good response to ergotics and due to pituitary macroadenoma. Clinical case. A 44 year old man with no familiar history of migraine presented to our hospital because of campimetric failure and a change of his migrainous features. The patient started with migraine without aura 2 years ago and was well treated with ergotics from the beginning. Field testing showed a bitemporal hemianopsia. Magnetic resonance imaging revealed an unknown pituitary macroadenoma. Conclusión. Pituitary macroadenoma must be included in the differential diagnosis of migraine headache although the presence of aura or the good response to ergotics

The advantages of frameless stereotactic biopsy over frame-based biopsy.

A comparison study is presented, which examines the outcome, complications and cost of stereotactic brain biopsy performed with a frameless versus a frame-based method. The technique of frameless stereotactic biopsy has been shown previously, in both laboratory and in vivo studies, to achieve a level of accuracy at least equal to frame-based biopsy. The investigators have validated the technique in a large clinical series. The frameless and frame-based series were concurrent, comprising 76 and 79 cases, respectively. The frameless stereotactic technique involved standard needle biopsy, targeted by an image-guidance system and directed by a novel rigid adjustable instrument-holder. Frame-based biopsies were performed with the CRW and Leksell systems. There were no significant differences in the demographics, lesion site, size and pathologies between the groups. Operating theatre occupancy and anaesthetic time were both significantly shorter for the frameless series than the frame-based series (p < 0.0001). In addition, the complication rate in the frameless biopsy series was significantly lower than in the frame-based series (p = 0.018). This resulted in lower ITU bed occupancy (p = 0.02), shorter mean hospital stay (p = 0.0013) and significant cost savings (p = 0.0022) for the frameless stereotactic biopsy group, despite the greater use of more expensive MRI in these cases. This comparison study demonstrates that the superior imaging, target visualization and flexibility of the technique of frameless stereotactic biopsy translates into tangible advantages for safety, time and cost when compared with the current gold-standard of frame-based biopsy. The principles are discussed and the authors propose a definition for the term 'frameless stereotaxy'.

Frameless navigation and endoscopy.

OBJECT: Frameless computerized neuronavigation has been increasingly used in intracranial endoscopic neurosurgery. However, clear indications for the application of neuronavigation in neuroendoscopy have not yet been defined. The purpose of this study was to determine in which intracranial neuroendoscopic procedures frameless neuronavigation is necessary and really beneficial compared with a free-hand endoscopic approach. METHODS: A frameless infrared-based computerized neuronavi- gation system was used in 44 patients who underwent intracranial endoscopic procedures, including 13 third ventriculostomies, nine aqueductoplasties. eight intraventricular tumor biopsy procedures or resections, six cystocisternostomies in arachnoid cysts, five colloid cyst removals, four septostomies in multiloculated hydrocephalus, four cystoventriculostomies in intraparenchymal cysts, two aqueductal stent placements, and fenestration of one pineal cyst and one cavum veli interpositi. All interventions were successfully accomplished. In all procedures, the navigational system guided the surgeons precisely to the target. Navigational tracking was helpful in entering small ventricles, in approaching the posterior third ventricle when the foramen of Monro was narrow, and in selecting the best approach to colloid cysts. Neuronavigation was essential in some cystic lesions lacking clear landmarks, such as intraparenchymal cysts or multiloculated hydrocephalus. Neuronavigation was not necessary in standard third ventriculostomies, tumor biopsy procedures, and large sylvian arachnoid cysts, or for approaching the posterior third ventricle when the foramen of Monro was enlarged. CONCLUSIONS: Frameless neuronavigation has proven to be accurate, reliable, and extremely useful in selected intracranial neuroendoscopic procedures. Image-guided neuroendoscopy improved the accuracy of the endoscopic approach and minimized brain trauma.

Image-guided placement of eye muscle electrodes for intraoperative cranial nerve monitoring.

OBJECTIVE: Monitoring of the oculomotor system during cranial base or brainstem surgery requires extraocular intraorbital insertion of electromyography electrodes. We investigated the use of image-guidance technology for anatomically correct intraorbital electrode placement. METHODS: For neuronavigation, an optical tracking system was used in a standard fashion. Needle electrodes were inserted percutaneously into the lateral rectus, inferior rectus, and superior oblique muscle along the axis of a hand-held pointer or by means of an electrode applicator to allow direct tracking with the navigation system. Electromyographic monitoring was performed by multichannel recordings of free running or evoked activity from the selected muscles. RESULTS: We have used this method in 10 patients; 5 had cranial base tumors and 5 underwent operations for brainstem lesions. No additional instruments or resources were required compared with the routine setup, and no intraorbital structures were injured. Successful monitoring of oculomotor, trochlear, or abducent nerve function was possible in each case. CONCLUSION: This method may have the potential to increase the safety and success rate of intraoperative electro-ophthalmography during microsurgery focused on preservation of neurological function.

Operative management of third ventriculostomy in cases of thickened, non-translucent third ventricular floor: technical note.

Today, endoscopic third ventriculostomy is an established operative modality in occlusive hydrocephalus. The elemental step in third ventriculostomy is the perforation of the floor of the third ventricle. Especially with a thickened third ventricular floor, anatomical orientation can be disturbed and perforation of third ventricular floor technically difficult. The combination of a neuronavigation system with an endoscope provides interactive image-guided neuroendoscopy. Exact planning of the approach is thus possible and the ideal trajectory to the target area can be determined. We have combined interactive neuronavigation and intraoperative fluoroscopy for incorporating real-time feedback to optimize endoscopy in patients with a thickened third ventricular floor selected for third ventriculostomy.

Advanced image-guided skull base surgery.

BACKGROUND: Tumors of the skull base frequently encase or extend into normal neural and vascular structures. Preoperative planning and intraoperative identification of anatomic landmarks is especially important in complex tumors since it helps avoid or minimize surgical morbidity. METHODS: By creating a surgical plan the image guidance software offers help in the establishment of a surgical approach. During surgery, the neuronavigation system displays the location of anatomic landmarks of the skull base regardless of any erosion or displacement. RESULTS: A series of 10 patients with complex tumors in various skull base locations is reported. Osseous structures are easily identified using the CT-based image guidance since these landmarks do not shift due to CSF loss. Image fusion of CT and MRI data gives additional information on the displacement of soft tissue structures. Image fusion in a substraction mode is helpful when a tumor has invaded bony structures or when the encasement of major vessels has to be visualized. CONCLUSION: The preoperative data preparation (planning of the approach, image fusion) plays a vital role in modern neuronavigation and contributes useful information during surgery for complex skull base tumors. Such advanced neuronavigation increases the efficacy and safety of intraoperative maneuvers. Eroded and distorted anatomic landmarks are not subject to a significant amount of intraoperative shift throughout the surgical procedure.

Long latency response of the mentalis muscle following transcranial magnetic stimulation with a circular coil in normal subjects.

Short latency response (SLR), middle latency response and long latency response (LLR) are elicited in facial muscles by transcranial magnetic stimulation. Although it has been said that the LLRs are elicited by the trigeminal nerve stimulation, a trigeminofacial reflex is recorded easily in normal subjects by the electrical stimulation in orbicularis oculi muscles as a blind reflex, but a trigeminal-facial reflex recorded in orbicularis oris, namely a snout reflex, is more difficult to record in normal subjects. The aim of this study is to demonstrate the LLR of lower facial muscles (mentalis muscle) by the transcranial magnetic stimulation, using a circular coil. The transcranial magnetic stimulations were performed over parieto-occipital scalp with frequencies of random and 0.3 Hz in 11 normal subjects and the responses in the mentalis muscle were recorded. The LLR of the mentalis muscle was recorded in all 11 subjects following SLRs. The latency, duration and LLR/SLR ratio were 37.4 msec, 20.3 msec and 9.1%, respectively. The waveform of the LLR varied trial to trial showing habituation with a stimulation of 0.3 Hz. At this time the LLR of the masseter muscle was not recorded following this transmagnetic stimulation. It was suggested that the LLR of the mentalis muscle is recorded by the transcranial magnetic stimulation of the trigeminal nerve with a circular coil. The ease and reliability of their recording make it possible to apply this LLR clinically as well as a blink reflex.

Initial hyperglycemia as an indicator of severity of the ictus in poor-grade patients with spontaneous subarachnoid hemorrhage.

An association between hyperglycemia and outcome in spontaneous subarachnoid hemorrhage (SAH) has been sporadically reported. Our hypothesis was that hyperglycemia is a sign of central metabolic disturbance linked with specific appearances on computerized tomography (CT) scans reflecting different degrees of corresponding brain injury. The admission plasma glucose level, initial CT findings, and outcome after 6 months were analysed in a cohort of 99 patients with SAH in Hunt & Hess Grade IV or V. The CT scans were quantitatively assessed for subarachnoid blood, intracerebral hematoma, intraventricular hemorrhage, hydrocephalus, midline shift and compression of the perimesencephalic cisterns. These findings were combined to determine a three-point CT severity score. All patients showed elevated (>5.8 mmol/l) plasma glucose levels on admission. Mortality among 33 patients with glucose concentration below 9.0 mmol/l was 33.3%, 71.1% for the 45 patients with glucose level between 9.0 and 13.0 mmol/l, and 95.2% for the 21 patients with concentration above 13.0 mmol/l (P<0.0001). Glucose level was higher in Grade V than in Grade IV patients (mean+/-SD) (11.8+/-3.2 vs 9.8+/-2.9 mmol/l; P=0.0012). Patients with mild CT findings (n=10) had the lowest glucose level (8.9+/-1.8 mmol/l; P=0.0082), whereas patients with severe findings (n=56) had the highest glucose (11.4+/-3.5 mmol/l; P=0.011). Despite association with clinical grade and extent of CT findings, logistic multiple regression revealed the admission plasma glucose level to be an independent prognosticator of outcome. The prognostic potential of the initial plasma glucose level may be beneficial in management protocols of poor-grade SAH patients.

Relationships of virtual reality neuroendoscopic simulations to actual imaging.

Advances in computer technology have permitted virtual reality images of the ventricular system. To determine the relevance of these images we have compared virtual reality simulations of the ventricular system with endoscopic findings in three patients. The virtual fly-through can be simulated after definition of waypoints. Flight objects of interest can be viewed from all sides. Important drawbacks are that filigree structures may be missed and blood vessels cannot be distinguished clearly. However, virtual endoscopy can presently be used as a planning tool or for training and has future potential for neurosurgery.

Accuracy of true frameless stereotaxy: in vivo measurement and laboratory phantom studies. Technical note.

The authors present the results of accuracy measurements, obtained in both laboratory phantom studies and an in vivo assessment, for a technique of frameless stereotaxy. An instrument holder was developed to facilitate stereotactic guidance and enable introduction of frameless methods to traditional frame-based procedures. The accuracy of frameless stereotaxy was assessed for images acquired using 0.5-tesla or 1.5-tesla magnetic resonance (MR) imaging or 2-mm axial, 3-mm axial, or 3-mm helical computerized tomography (CT) scanning. A clinical series is reported in which biopsy samples were obtained using a frameless stereotactic procedure, and the accuracy of these procedures was assessed using postoperative MR images and image fusion. The overall mean error of phantom frameless stereotaxy was found to be 1.3 mm (standard deviation [SD] 0.6 mm). The mean error for CT-directed frameless stereotaxy was 1.1 mm (SD 0.5 mm) and that for MR image-directed procedures was 1.4 mm (SD 0.7 mm). The CT-guided frameless stereotaxy was significantly more accurate than MR image-directed stereotaxy (p = 0.0001). In addition, 2-mm axial CT-guided stereotaxy was significantly more accurate than 3-mm axial CT-guided stereotaxy (p = 0.025). In the clinical series of 21 frameless stereotactically obtained biopsies, all specimens yielded the appropriate diagnosis and no complications ensued. Early postoperative MR images were obtained in 16 of these cases and displacement of the biopsy site from the intraoperative target was determined by fusion of pre- and postoperative image data sets. The mean in vivo linear error of frameless stereotactic biopsy sampling was 2.3 mm (SD 1.9 mm). The mean in vivo Euclidean error was 4.8 mm (SD 2 mm). The implications of these accuracy measurements and of error in stereotaxy are discussed.

Interactive image-guided neuroendoscopy: development and early clinical experience.

Technical advances and pioneering surgeons have established neuroendoscopy as an accepted diagnostic and therapeutic tool. The clinical indications for endoscopy, variety of operative techniques and number of endoscopic surgeons continue to increase steadily. However, there are fundamental limits to the scope of freehand endoscopy principally governed by the need for direct vision of anatomical and pathological structures. In addition, whilst the expert neuroendoscopist is only occasionally disorientated by complex distorted anatomy, the rising number of novices are likely to be mislead relatively often. We report the integration of neuroendoscopy with an optical neuronavigation system to provide interactive image-guided neuroendoscopy. This combination both removes the constraining requirement for direct vision and provides accurate localisation to guide the surgeon during surgery. We describe the clinical application of this method to two cases where image-guided endoscopy was essential to the safe completion of the procedure.

Postimaging brain distortion: magnitude, correlates, and impact on neuronavigation.

OBJECT: This prospective study was conducted to quantify brain shifts during open cranial surgery, to determine correlations between these shifts and image characteristics, and to assess the impact of postimaging brain distortion on neuronavigation. METHODS: During 48 operations, movements of the cortex on opening, the deep tumor margin, and the cortex at completion were measured relative to the preoperative image position with the aid of an image-guidance system. Bone surface offset was used to assess system accuracy and correct for registration errors. Preoperative images were examined for the presence of edema and to determine tumor volume, midline shift, and depth of the lesion below the skin surface. Results were analyzed for all cases together and separately for four tumor groups: 13 meningiomas, 18 gliomas, 11 nonglial intraaxial lesions, and six skull base lesions. For all 48 cases the mean shift of the cortex after dural opening was 4.6 mm, shift of the deep tumor margin was 5.1 mm, and shift of the cortex at completion was 6.7 mm. Each tumor group displayed unique patterns of shift, with significantly greater shift at depth in meningiomas than gliomas (p = 0.007) and significantly less shift in skull base cases than other groups (p = 0.003). Whereas the preoperative image characteristics correlating with shift of the cortex on opening were the presence of edema and depth of the tumor below skin surface, predictors of shift at depth were the presence of edema, the lesion volume, midline shift, and magnitude of shift of the cortex on opening. CONCLUSIONS: This study quantified intraoperative brain distortion, determined the different behavior of tumors in four pathological groups, and identified preoperative predictors of shift with which the reliability of neuronavigation may be estimated.

Continuous intrathecal baclofen infusion in severe spasticity after traumatic or hypoxic brain injury.

Severe spinal spasticity has been shown to be a good indication for continuous intrathecal baclofen infusion (CIBI), but there is only limited experience with this treatment in patients with supraspinal spasticity. Eighteen patients with severe spasticity from traumatic or hypoxic brain injury were treated with CIBI. In all patients spasticity could be reduced significantly. The mean Ashworth score was reduced from 4.5 to 2.33 and the mean Spasm frequency score from 2.16 to 0.94. This reduction of spasticity led to a marked pain reduction. Nursing, perineal care and mobilization became much easier. The complication rate was low. In this series we saw one infection in the pump pocket, one epileptic seizure after a bolus application of baclofen and one spinal catheter displacement. The results are similar to those reported from series of patients with spinal spasticity and correspond to the limited experience we have so far with supraspinal spasticity patients. To prevent limb contractures CIBI should be performed as soon as the patient is in a stable clinical condition after brain injury. Further prospective clinical trials will be necessary to obtain more experience with patients suffering from supraspinal spasticity.

Clinical introduction of an adjustable rigid instrument holder for frameless stereotactic interventions.

Interactive image guidance is now in routine use for open neurosurgical procedures and has demonstrated patient benefits. However, freehand interactive guidance is not an appropriate replacement for the traditional frame-based stereotactic procedures of biopsy, electrode placement, and functional lesioning. These point-based procedures require precise target localization and direct instrument guidance to avoid collateral brain injury. To perform true frameless stereotactic procedures requires a guide that is also adjustable for positioning, lockable, and adaptable to multiple instruments. We describe such a device, which is employed for the guidance of biopsy needles, shunts, electrodes, and endoscopes during neuronavigation. The method of frameless stereotactic biopsy retrieval with an infrared-based neuronavigation system is described, clinical results are given, and further areas of application discussed.