Image directed stereotactic surgery for brain stem lesions

Use of intra-operative stimulation of brainstem lesion target sites for frameless stereotactic biopsies

INTRODUCTION

Frameless stereotactic navigation is used to direct the trajectory and biopsy site of target lesions. We report on a novel intra-operative stimulating (IOS) probe that is integrated into a commercially available stereotactic biopsy needle with the rationale that stimulation of the intended biopsy site should predict functional tissue thus preventing inadvertent biopsy of eloquent tissue.

METHODS

Patients undergoing brainstem biopsies for atypical lesions were offered the additional stimulation procedure. The IOS probe was used to deliver stimulation in an attempt to determine the proximity of eloquent tissue. Once the desired location of the biopsy needle was achieved, the IOS probe was inserted down the centre of the biopsy needle and the stimulus applied. If no action potential was recorded, biopsies from four quadrants of the lesion were taken. If however a compound action potential was recorded, a new target was selected.

RESULTS

Nine patients had the biopsy and stimulation procedure performed. The median age was 36 months. A minimum of 8 samples were obtained from each patient. Biopsy material was adequate to obtain a diagnosis in all 9 patients. In 2 cases use of the device influenced the insertion trajectory or biopsy site. No patients experienced any complications directly attributable to either the biopsy procedure or application of the stimulation.

CONCLUSIONS

Use of the IOS probe for intra-operative stimulation of the intended brainstem biopsy site was found to be safe and feasible. The addition of stimulation using the IOS probe can be done with minimal change in workflow.

Safety and efficacy of brainstem biopsy in children and young adults

OBJECTIVE

Biopsies of brainstem lesions are performed to establish a diagnosis in the setting of an atypical clinical or radiological presentation, or to facilitate molecular studies. A better understanding of the safety and diagnostic yield of brainstem biopsies would help guide appropriate patient selection.

METHODS

All patients who underwent biopsy of a brainstem lesion during the period from January 2011 to June 2019 were reviewed. Demographic, radiological, surgical, and outcome data were collected.

RESULTS

A total of 58 patients underwent 65 brainstem biopsies during the study period. Overall, the median age was 7.6 years (IQR 3.9-14.2 years). Twenty-two of the 65 biopsies (34%) were open, 42 (65%) were stereotactic, and 1 was endoscopic. In 3 cases (5%), a ventriculoperitoneal shunt was placed, and in 9 cases (14%), a posterior fossa decompression was performed during the same operative session as the biopsy. An intraoperative MRI (iMRI) was performed in 28 cases (43%). In 3 of these cases (11%), the biopsy was off target and additional samples were obtained during the same procedure. New neurological deficits were noted in 5 cases (8%), including sensory deficits, ophthalmoparesis/nystagmus, facial weakness, and hearing loss; these deficits persisted in 2 cases and were transient in 3 cases. A pseudomeningocele occurred in 1 patient; no patients developed a CSF leak or infection. In 8 cases (13%) an additional procedure was needed to obtain a diagnosis.

CONCLUSIONS

Brainstem biopsies are safe and effective. Target selection and approach should be a collaborative effort. iMRI can be used to assess biopsy accuracy in real time, thereby allowing any adjustment if necessary.

Validation of a magnetic resonance imaging guided stereotactic access to the ovine brainstem

Background

Anatomical differences between humans and domestic mammals preclude the use of reported stereotactic approaches to the brainstem in animals. In animals, brainstem biopsies are required both for histopathological diagnosis of neurological disorders and for research purposes. Sheep are used as a translational model for various types of brain disease and therefore a species-specific approach needs to be developed. The aim of the present study was to establish a minimally invasive, accurate and reproducible stereotactic approach to the brainstem of sheep, using the magnetic resonance imaging guided Brainsight^TM frameless stereotactic system.

Results

A transoccipital transcerebellar approach with an entry point in the occipital bone above the vermis between the transverse sinus and the external occipital protuberance was chosen. This approach provided access to the target site in all heads. The overall mean needle placement error was 1.85 ± 1.22 mm.

Conclusions

The developed transoccipital transcerebellar route is short, provides accurate access to the ovine caudal cranial fossa and is a promising approach to be further assessed in live animals.

Stereotactic biopsy of brainstem lesions: Techniques, efficacy, safety, and disease variation between adults and children: A single institutional series and review

BACKGROUND

Stereotactic biopsy of brainstem lesions have been performed with varying indications, with most of the literature reporting on children.

MATERIALS AND METHODS

The present study retrospectively analyzed all cases that underwent stereotactic biopsy for brainstem lesion in both adult and pediatric population between 1994 and 2009 in a single tertiary neurosurgical center. The clinical and radiological features, technique of the procedure, morbidity, diagnostic accuracy, spectrum of diagnosis, and variations in adult and pediatric population were analyzed.

RESULTS

Eighty-two patients were included in the study. Computed tomography (CT) was used as guidance in 73 (38 children and 35 adults) patients and magnetic resonance imaging (MRI) in 9 (3 children and 6 adults). The biopsy was performed in a procedure room under local anesthesia in most adults, while children required sedation. Glioblastoma comprised 29.3% of all pathologies in children, compared with only 4.9% of the pathologies in adult population (P = 0.007). Tuberculosis was the next major diagnosis (9.8%). In 12 patients, initial biopsy was inconclusive. Following a repeat biopsy in 5 of these patients, a diagnosis was possible for 75/82 (91.5%) patients by STB. The location of the target, the choice of entry, the radiological characteristic of the lesion, enhancement pattern, and age group did not significantly correlate with the occurrence of inconclusive biopsy. Permanent complications occurred in two patients (2.4%). There was no mortality in this series.

CONCLUSION

Stereotactic biopsy has an important role in brainstem lesions, more significantly in adults, due to wider pathological spectrum. It can be performed safely under local anesthesia through a twist drill craniostomy in most of the adults.

Feasibility, safety, and indications for surgical biopsy of intrinsic brainstem tumors in children

PURPOSE

Diffuse intrinsic pontine gliomas (DIPGs) are rapidly progressive and aggressive tumors that usually arise in children. Their anatomic location makes gross total surgical resection impossible, and fewer than 10% of patients survive more than 2 years after diagnosis. Often, these lesions are treated based on imaging characteristics alone. However, despite aggressive chemotherapy and radiation treatments available, prognosis remains poor. There is therefore a need for new therapies directed by biologic profiling. This necessitates a tissue diagnosis and, therefore, surgical biopsy. We have reviewed the results of biopsy for DIPGs in children at a single institution and compared our results to those available in the literature to elucidate the utility of biopsy for DIPGs.

METHODS

A historical cohort study was performed using medical records of patients under the age of 18 who underwent surgical biopsy of a DIPG at a single institution.

RESULTS

Nine patients were included, four males and five females. Age at presentation ranged from 8 months to 10 years (average 5.7 years). Pathologic diagnoses included five high grade (WHO grade III or IV) gliomas and four low grade (WHO grade II) astrocytomas. There were no intraoperative complications, and only one patient developed a new postoperative neurologic deficit.

CONCLUSIONS

Stereotactic biopsy of DIPGs is essential to obtain a pathologic diagnosis and is associated with low morbidity. This technique is important to elucidate biological characteristics of these tumors in order to direct multidisciplinary treatment plans possibly involving chemotherapy, radiation therapy, or other future clinical trial interventions for children with DIPGs.

Pitfalls in precision stereotactic surgery

Precision is the ultimate aim of stereotactic technique. Demands on stereotactic precision reach a pinnacle in stereotactic functional neurosurgery. Pitfalls are best avoided by possessing in-depth knowledge of the techniques employed and the equipment used. The engineering principles of arc-centered stereotactic frames maximize surgical precision at the target, irrespective of the surgical trajectory, and provide the greatest degree of surgical precision in current clinical practice. Stereotactic magnetic resonance imaging (MRI) provides a method of visualizing intracranial structures and fiducial markers on the same image without introducing significant errors during an image fusion process. Although image distortion may potentially limit the utility of stereotactic MRI, near-complete distortion correction can be reliably achieved with modern machines. Precision is dependent on minimizing errors at every step of the stereotactic procedure. These steps are considered in turn and include frame application, image acquisition, image manipulation, surgical planning of target and trajectory, patient positioning and the surgical procedure itself. Audit is essential to monitor and improve performance in clinical practice. The level of stereotactic precision is best analyzed by routine postoperative stereotactic MRI. This allows the stereotactic and anatomical location of the intervention to be compared with the anatomy and coordinates of the intended target, avoiding significant image fusion errors.

Stereotactic biopsy for brainstem tumors in pediatric patients

OBJECTIVE

Our aim is to describe clinical and paraclinical features in patients who underwent stereotactic-guided biopsy for brainstem tumors.

METHODS

A study of case series was made by reviewing the records of patients who underwent stereotactic biopsy for brainstem tumors.

RESULTS

Stereotactic biopsy for brainstem tumors was performed (between 2000 and 2008) in 20 children (11 girls, and 9 boys), mean age 7.95 +/- 3.12 years at the time of diagnosis. The mean time from onset of symptoms to diagnosis was 6.59 +/- 13.58 months (0.50-60 months). The most frequent symptoms and signs at onset were related to disturbance of cerebellar function and cranial nerve nuclei. Location was pontomesencephalic (35%), pontine (30%), pontomedullar (25%), and in the whole brainstem (10%). The most common type of image was intrinsic-diffused (55%). The histopathology was anaplastic astrocytoma (30%), followed by fibrillary and pilocytic types (25% each), low-grade astrocytoma (5%), high-grade astrocytoma (5%), and normal tissue (10%). Mild complications were observed in only two cases.

CONCLUSIONS

Stereotactic biopsy done for clarifiying a diagnostic imaging in brainstem tumors is important in obtaining a definitive diagnosis with a low rate of complications.

Diffuse brainstem gliomas in children: should we or shouldn't we biopsy?

The decision to biopsy diffuse pontine gliomas in children remains controversial. There have been many publications over the last 30 years aiming to address this issue. The prognosis for these patients remains extremely poor regardless of treatment and many authors advocate that biopsy carries significant risk for little or no clinical benefit. However, with an increasing knowledge of tumour biology and genetics there is the potential for specific treatments tailored for individual tumours based on their biological or genetic characteristics. The progress of such science in the first instance requires histological diagnosis as part of well conducted clinical trials, then, when treatments have been developed, biopsy samples will be needed to identify the tumours that may respond to such treatments. The authors believe that there is an increasing need for performing a biopsy of these lesions.

Stereotactic biopsy of brain stem masses: decision analysis and literature review

BACKGROUND

Adult brain stem tumors are rare, and diverse pathology can be found in this location. Stereotactic biopsy of lesions in the brain stem has been performed since the 1960s with high diagnostic and low complication rates. Advances in imaging technology have raised questions regarding the utility of biopsy. We perform decision analysis to aid clinicians in their approach to management of adult brain stem lesions.

METHODS

A structured literature search revealed 20 publications with 457 patients who had undergone brain stem lesion biopsy. These publications were reviewed to determine diagnostic rates and the incidence of complications. Standard decision analytic techniques were applied to the case of a virtual adult patient with a lesion in the brain stem.

RESULTS

A 1-way sensitivity analysis revealed the likelihood that the preoperative diagnosis was correct and the rate at which incorrect treatment was based on faulty empirical diagnosis as the 2 factors with the greatest effects on patient outcome. The diagnostic rate and complication rate of biopsy, within the ranges reported in the literature, had lesser effects. A threshold analysis was constructed to compare outcomes from stereotactic biopsy vs empiric therapy for a brain stem lesion. The probability that the preoperative diagnosis is correct is plotted vs the probability that empirical treatment based on an incorrect diagnosis will have adverse effect.

CONCLUSIONS

Management of lesions in the adult brain stem requires careful consideration of multiple preoperative factors including clinical and radiographic diagnostic certainty, consequences of empiric therapy, and the surgeon's complication rate.

Stereotactic biopsies of focal brainstem lesions

BACKGROUND

Stereotactic biopsies of the brainstem (SBB) are a selected group of stereotactic operations owing to the lower incidence of brainstem lesions requiring biopsy, the greater complexity, and the higher risks of these procedures. Usually, the lower the lesion in the brainstem, the greater the risks involved. The approach of the different target locations by distinct routes, transcerebral and transcerebellar, is still a matter of debate. Moreover, pure medullary lesions are seldom biopsied, whereas diffuse brainstem lesions, typical of children's brainstem gliomas and rather frequent in most published series, depend less and less on the histopathological confirmation for treatment. In this study, the authors present their own experience on SBB aiming to discuss mainly their indications, approach routes choice, and procedure techniques.

METHODS

The authors reviewed a series of 30 SBB (27 adults and 3 children) out of 450 stereotactic biopsies of the central nervous system performed for the last 10 years. All cases but one presented as focal brainstem masses, 19 mainly in the pons and 10 in the midbrain. Eleven lesions (10 in the midbrain and one midbrain-pontine) were approached by a transfrontal route. All the others were approached by a suboccipital transcerebellar route.

RESULTS

Twenty-six (87%) out of the 28 cases (93%) where a positive histopathological result was obtained had a specific diagnosis: 18 tumors (14 astrocytomas, 2 primary brain lymphomas, 1 oligodendroglioma, and 1 ganglioglioma), 2 toxoplasmosis, 2 sarcoidosis, 1 aspergillus abscess, 1 vasculitis, 1 acute inflammatory demyelinating disease, and 1 progressive multifocal leucoencephalopathy. Four nontumoral lesions arose in patients with AIDS. Morbidity was restricted to 2 cases consisting of transient cranial nerve deficits.

CONCLUSIONS

Stereotactic biopsies are specially useful for the diagnosis of focal brainstem lesions. Midbrain and midline lesions should be approached through the cerebrum, whereas most of the pontine lesions through the cerebellum. Overall, this procedure should be performed with "functional-like" precision and require some technical refinements to reach maximal accuracy with minimal morbidity.

Stereotactically-guided biopsies of brainstem tumors

INTRODUCTION

More than 10 years ago, the goal of our work had been to obtain a tissue sample of infiltrating lesions of the brainstem that had been diagnosed using computerized axial tomography (CAT). At that time, biopsies were believed to be indispensable when starting treatment of tumors. With time our objectives changed. Biopsies remained necessary, since until 1 year before the writing of this article we had not had the benefits of magnetic resonance imaging (MRI) at our Hospital. We also decided that carrying out sound statistics, confirmed by biopsies, was in itself a good procedure, especially in a country in which, to date, no serial studies of brainstem tumors had been undertaken.

METHODS

We analyzed all of the patients diagnosed with posterior fossa tumors between March 1989 and March 2002 at the Hospital Infantil de México Federico Gómez (HIM). A preoperative TAC of the cranium was performed on every patient. Stereotactically-guided biopsies during tomography allowed precise control of penetration. Material obtained was sent to the Department of Pathology for analysis.

RESULTS

Fifty patients were diagnosed with infiltrating tumors of the brainstem: 30 cases of low-grade astrocytomas, 13 cases of high-grade astrocytomas, 2 cases of primitive neuroectodermic tumors, 2 cases of rhabdoid tumors, 1 case of ependymoma, and 2 patients had non-specified tumors. The most frequent symptoms and signs were ataxia and disturbances of the cranial nerves. There was no mortality caused by penetration, and follow-up studies of more than 5 years were carried out.

DISCUSSION

The results from our series were similar to those in the literature. In our case, follow-up studies were undertaken for longer periods. In the first section of our work, we suggest the need for stereotactic biopsies in order to arrive at a precise diagnosis in environments in which MRI may be unavailable.

CONCLUSION

At present, presumptive diagnosis of infiltrating brainstem lesions may be adequately undertaken with imaging methods, such as MRI. However, we believe that a stereotactically-guided biopsy provides an accurate method for diagnosing lesions of the brainstem. In our case, this procedure has been carried out entirely in the tomography room, without any complications of disease or mortality.

The stereotactic volumetric information: its role in two-step resection of brainstem and thalamic giant tumor. Report of three cases and technical note

BACKGROUND

A compact intracerebral tumoral lesion is usually considered to be completely resectable. Nevertheless, radical resection of a huge lesion located in a critical area may damage the surrounding compressed brain tissue. In cases with a good prognosis, a two-step removal appears to be a safer strategy.

METHODS

In three cases, two with huge brain stem lesions and one with a thalamic lesion, a two-step volumetric stereotactic resection was planned. This strategy allowed us to evaluate the amount of tumor to be removed during the first procedure and to have, during the second operation, an exact definition of the reduced mass with regard to the scar tissue and postoperative adhesions. Furthermore, we avoided significant shifting of the cerebral structures during both procedures.

RESULTS

There was a very good final recovery in the cases with brain stem lesions and a minimal deficit in the patient with the thalamic lesion. The patient with a mesencephalic lesion remained comatose for almost 2 days after the first procedure, confirming our fears about too radical a one-step resection.

CONCLUSIONS

We think that by using current techniques, it is possible to remove a well circumscribed lesion regardless of its position. This is probably easier with giant lesions where a safe trajectory can be planned. In these cases, with lesions located in very critical areas but with a good prognosis, a two-step resection appears to be a good option.

A brainstem stereotactic atlas in a three-dimensional magnetic resonance imaging navigation system: first experiences with atlas-to-patient registration

OBJECT

The authors describe a computer-resident digital representation of a stereotactic atlas of the human brainstem, its semiautomated registration to sagittal fast low-angle shot three-dimensional (3-D) magnetic resonance (MR) imaging data sets in 27 healthy volunteers and 24 neurosurgical patients, and an analysis of the subsequent transforms needed to refine the initial registration.

METHODS

Contour drawings from the atlas, which offer the 70th percentile of variation of anatomical structures, were interpolated into an isotropic 3-D representation. Initial atlas-to-patient registration was based on the fastigium/ventricular floor plane reference system. The quality of the fit was evaluated using superimposition of the atlas and MR images. If necessary, the atlas was tailored to the individual anatomy by using additional transforms. On average, the atlas had to be stretched by 2 to 6% in the three directions of space. Scale factors varied over a broad range from -8 to +19% and the benefit of visual interactive control of the atlas-to-patient registration was evident. Analysis of distances within the pons measured in the midsagittal MR imaging slices and the required scale factors revealed significant correlations that may be used to reduce the amount of user interaction in the coregistration substantially. In 70.6% of the cases, the atlas had to be shifted in a cranial direction along the brainstem axis (in 25.5% of cases 3-4 mm, in 45.1% of cases 1-2 mm). This was due to a more caudal position of the fastigium cerebelli on the MR images compared with the atlas.

CONCLUSIONS

This observation, in conjunction with the variability of the height of the fourth ventricle in our MR imaging data (range 6.1-15.2 mm, mean 10.1 mm, standard deviation 1.8 mm) calls into question the role of the fastigium cerebelli as an anatomical landmark for localization within the brainstem.

Primary intracranial germinoma involving the midbrain

To our knowledge, this is the first reported case of a germinoma involving the midbrain without the demonstrable coexistence of any common midline tumors. A 27-year-old man was referred to our institution for evaluation and treatment of diplopia persisting for 5 years. Magnetic resonance imaging (MRI) showed the mass in the midbrain to be of iso intensity on T1-weighted images, and of high intensity on T2-weighted images with homogeneous enhancement. MRI-guided stereotactic biopsy was performed, and the histologic diagnosis was germinoma. Following biopsy, external beam radiotherapy of 50 Gy (whole brain 30 Gy: local 20 Gy) was performed. At the time of discharge, the patient's neurological symptoms had resolved. Follow-up MRI revealed disappearance of the tumor. These findings suggest the diagnostic value of magnetic resonance image-guided stereotactic biopsy in the differential diagnosis of adult brainstem lesions, which should now include germinoma.

MR-guided procedures using contemporaneous imaging frameless stereotaxis in an open-configuration system

Frameless MR-guided procedures have had limited application using conventional closed magnets, due largely to the technical difficulties involved. As a result of in-room MR image-monitoring capabilities, new open-design magnets now allow frameless stereotaxis using contemporaneous imaging to guide more invasive procedures. We evaluate our clinical experience with this new technique. An open-design 0.2 T magnet (Siemens OPEN) combined with an in-room monitor was used for 33 frameless MR-guided procedures (aspiration cytology, biopsy, and/or treatment) in a variety of locations in the head, neck, spine, brain, pelvis, and abdomen. Success of the procedure was based on the ability to accurately position the instrument in the target region to allow biopsy and/or treatment. The open-design magnet allowed the physician to directly access the patient for frameless stereotaxis as the procedure was performed. The in-room monitor provided contemporaneous imaging feedback during the procedure for successful placement of the instrument in the target region. Twenty-eight biopsy and five treatment procedures were performed. In all cases the technique resulted in successful placement of the instrument within the target tissue to complete the procedure. MR-guided procedures using contemporaneous imaging frameless stereotaxis are possible in an open-design magnet with in-room image monitoring and offer exciting possibilities for further development.

[Brain stem metastasis revealing bronchopulmonary cancer: 2 cases]

INTRODUCTION

Brainstem metastasis is a very rare revealing feature of lung carcinoma.

EXEGESIS

We report two cases of brainstem metastasis revealing lung carcinoma. In the first case, diagnosis was made on stereotaxic biopsy. In the second, the biopsy was not necessary as lung lesion was observed on thoracic CT-scan. Diagnosis of metastasis is difficult when a brainstem tumor occurs.

CONCLUSION

Stereotaxic biopsy is an interesting tool to distinguish between primary lesion and metastasis, but only when diagnosis work-up of primary cancer is negative.

Stereotactic brachytherapy for a cystic metastatic brain tumor in the midbrain. Case report

The authors report a rare case of a cystic metastasis in the midbrain that was successfully treated by brachytherapy following stereotactic biopsy and aspiration of the intratumoral cyst. Stereotactic aspiration of cystic lesions can lead to clinical improvement and brachytherapy prevents cyst recurrence. A 46-year-old man was referred to the authors' institution with a 2-month history of a left hemisensory disturbance and a 1-month history of progressive hemiparesis. Magnetic resonance (MR) imaging revealed a ring-enhancing cystic mass in the midbrain. On the basis of this imaging study, a differential diagnosis that included brainstem abscess, glioma, and metastatic tumor was made. Magnetic resonance imaging-guided stereotactic biopsy and aspiration of the intratumoral cyst were performed, yielding 5 ml of yellowish-white fluid. Histological examination provided a diagnosis of adenocarcinoma. During the surgery, a catheter through which brachytherapy would be delivered was inserted at a predetermined target. The patient's left hemiparesis and sensory disturbance were markedly improved and brachytherapy was begun 2 days postoperatively. Three radioactive isotopes composed of iridium-192 were implanted to irradiate the tumor tissue. The total dose at the tumor periphery was 30 Gy, which was administered over 100 hours. External-beam radiotherapy (20 Gy) was added after completion of the brachytherapy. At discharge from the hospital, the patient was alert and all his neurological symptoms had resolved. Follow-up MR imaging revealed stabilization of the cyst and no recurrence of the tumor. The patient is alive and well 18 months following the brachytherapy. This case suggests that brachytherapy can delay cyst recurrence, suppress tumor growth, and prolong survival in patients with cystic brainstem metastasis.

Stereotactic localization with magnetic resonance imaging: a phantom study to compare the accuracy obtained using two-dimensional and three-dimensional data acquisitions

OBJECTIVE

To compare the accuracy of stereotactic localization using magnetic resonance imaging (Siemens 1.5-T Magnetom; Siemens, Erlangen, Germany) with two-dimensional and three-dimensional data acquisition techniques.

METHODS

A phantom study was performed in which the coordinates of an array of rods were determined from images in both two-dimensional and three-dimensional studies and compared with measured values in a series of transverse, coronal, and sagittal images.

RESULTS

The results demonstrated a distinct advantage in using three-dimensional acquisition; an error greater than 2 mm was identified in only 0.8% of the imaged volume, compared with 12% of the imaged volume in the two-dimensional study.

CONCLUSION

The results indicated that more accurate stereotactic localization is achieved with a three-dimensional acquisition.

A phantom study to assess the accuracy of stereotactic localization, using T1-weighted magnetic resonance imaging with the Leksell stereotactic system

This phantom study assesses the accuracy of stereotactic localization using the Leksell G frame (Elekta Instruments AB, Stockholm, Sweden) with T1-weighted magnetic resonance imaging (Siemens 1.5 T Magnetom; Erlangen, Germany). The coordinates of an array of solid perspex rods were determined and compared with measured values in a series of transverse, coronal, and sagittal images. The maximum absolute errors observed (X = 2.7 mm, Y = 7.0 mm, Z = 8.0 mm) were discouraging. However, the more reasonable mean errors (X = 0.4 mm, Y = 0.7 mm, Z = 1.3 mm) reflect considerable variation in accuracy throughout the volume assessed and limitation of maximum errors to specific areas. We present details of the spatial variation and discuss possible mechanisms for improving accuracy. The overall results are of direct relevance only to the scanner used. These results are, however, an indication of the need to approach with caution stereotactic localization using magnetic resonance imaging and to emphasize the requirement for quality assurance and for a comprehensive study of the scanner's characteristics.

Results and expectations with image-integrated brainstem stereotactic biopsy

BACKGROUND

The histologic diagnosis of an intrinsic brainstem tumor remains problematic due to controversies in methods of biopsy. Despite the widespread use of biopsy techniques, stereotactic brain stem biopsy has received limited attention due to potential morbidity and limited sample size.

METHODS

To evaluate the safety and efficacy of brain stem stereotactic biopsy using a dedicated computed tomography (CT)-stereotactic operating room suite, we reviewed our outcomes in 40 consecutive patients over a 13-year interval. This study included patients with midbrain lesions (n = 20), pontine lesions (n = 18), and medullary lesions (n = 2). Midline lesions were approached via a coronal, transthalamic trajectory; lateral brain stem lesions usually were approached via a transcerebellar route.

RESULTS

A histologic diagnosis was achieved in 38 patients (95%). All patients had an immediate, intraoperative, postbiopsy CT scan to check for hemorrhage (none occurred). Morbidity was limited to one patient (2.5%) who developed a transient diplopia; there was no mortality.

CONCLUSIONS

Stereotactic biopsy for intrinsic brain stem lesions proved as safe and effective as biopsy in the supratentorial compartment. Using high-resolution stereotactic imaging, an appropriate intraparenchymal trajectory, limited sampling, and specific neuropathologic tests, stereotactic techniques within the brain stem were performed with low risk and high accuracy. Biopsy results facilitated specific management strategies for each patient.

Stereotactic biopsy of brainstem mass lesions

BACKGROUND

Appropriate therapy of brainstem lesions is guided by accurate diagnosis. Because the majority of brainstem lesions are not amenable to surgical resection, stereotactic biopsy is an attractive method of obtaining pathological tissue.

METHODS

We reviewed the medical records of all patients who underwent stereotactic biopsy of brainstem mass lesions at our institution by the senior author (WAF) over a 10-year period ending in December 1993.

RESULTS

Twenty-four patients ranging in age from 3 to 68 years underwent stereotactic biopsy of brainstem mass lesions at our institution by the senior author (WAF) over a 10-year period ending in December 1993.

RESULTS

Twenty-four patients ranging in age from 3 to 68 years underwent stereotactic biopsy of mass lesions of the brainstem. Sixteen lesions were located primarily in the pons, 7 in the midbrain, and 1 in the medulla. Twenty-two of the biopsies were approached transfrontally and two were approached via the suboccipital transcerebellar route. Pathological diagnosis was made in 23 of the 24 patients. The histologic diagnosis was astrocytoma in 16 patients, metastasis in 3, lymphoma in 1, germinoma in 1, chordoma in 1, progressive multifocal leukencephalopathy in 1, and was nondiagnostic in 1. Complications included 1 case of increased hemiparesis, 1 case of obstructive hydrocephalus, and 1 death. Six patients were less than 20 years of age and in each of these patients the preoperative diagnosis was astrocytoma. In all of these patients the pathology revealed astrocytoma. In the adult patients the pathology was more varied, with 7 of the 18 patients having tumors or pathology other than astrocytoma.

CONCLUSIONS

The data suggest that, in adult patients, brainstem lesions are of varied pathology and stereotactic biopsy can provide adequate tissue for diagnosis. The data also suggest that the diagnosis of brainstem glioma in children can often be made without submitting the patient to the risk of surgery.

Stereotactic biopsy for intrinsic lesions of the medulla through the long-axis of the brainstem: technical considerations

The authors report the technique and results for stereotactic biopsy of intrinsic lesions of the medulla oblongata through the long-axis of the brainstem. Multi-planar stereotactic magnetic resonance imaging and/or reformatted computed tomography imaging is used for coordinate determination and trajectory selection and facilitates a completely intra-axial pathway through critical neural tissue. Two patients with small, solitary, enhancing lesions of the medulla had stereotactic sampling via this approach performed under local anesthesia. There was no morbidity and in both the patients a histologic diagnosis of lymphoma was obtained. We believe that with high-resolution, multi-planar stereotactic imaging, small lesions in the medulla can safely be biopsied, avoiding the need for either posterior fossa craniectomy and open biopsy, or for empiric management.