Thalamic abscess: a stereotactically treatable lesion

A 69-year-old man developed abdominal pain, fever, shaking chills and acute hemiplegia. Computed tomography (CT) scanning demonstrated a hematoma within a thalamic space-occupying lesion having the radiological characteristics of a malignant glioma. Low-grade fever and leukocytosis persisted and follow-up CT scanning showed ring enhancement of the thalamic lesion and ependymitis suggesting a cerebral abscess. Stereotactic aspiration achieved drainage of the abscess and relief of mass effect and provided pus from which a causative organism was identified and treated with appropriate antibiotics. Contrast-enhanced CT scan should be obtained in cases of hemorrhage within mass lesions and tissue diagnosis should be achieved even in deep brain regions, as this can be accomplished safely using stereotactic techniques.     

The Clinical Study of Stereotactic Microsurgery

The objective of this study is to investigate the operative methods and therapeutic effects of stereotactic-guided microsurgical resection of hypertensive cerebral hemorrhage lesions in functional region. 18 cases of intracranial lesions (diameter 1.5–3 cm) were studied using a Leksell-G stereotactic system. Guided by the CT or MR, a small incision was made and the skull was opened with an annular drill. Electrophysiological stimulation was applied along the non-functional areas. 100 patients with cerebral hemorrhage were randomized into two groups of 50 cases each. One of the groups was treated using microsurgery, while the other group was treated using stereotactic technique. A comparative study was carried out between the two treatment methods for hypertensive intracerebral hemorrhage using the recent (1 month) and long-term (6 months) treatment. Using a Leksell-G system for precise positioning of microsurgery, 100 % of the lesion was fully removed. Neurological function was well protected without mortality or neurological deficiency. The use of stereotactic microsurgery for hypertensive intracerebral hemorrhage is successful compared with traditional methods. There is a significant clinical effect on the recovery of neurological function in patients. Stereotactic microsurgical resection of the lesion along with Ribbon treatment of hypertensive cerebral hemorrhage is an accurate, minimally invasive, safe, and effective surgical method.     

New CT-guided stereotactic apparatus and clinical experience with intracerebral hematomas

The conventional Sugita stereotactic frame has been improved to perform CT-guided stereotactic surgery both in the CT and operating rooms. The development of our instrument and the software of the scanners' computer are presented. Newly designed equipment produced almost no artifacts on the CT image. Using the improved stereotactic frame, we have operated upon 44 intracerebral hematomas in the CT room. More than 80% of the cases had satisfactory results. Two complications were encountered, and 1 patient died from pneumonia. Our initial experience of the pre- and postoperative cerebral blood flow measurement with 133Xe inhalation method and single photon emission CT is described.     

MRI contribution to the stereotactic management of cerebral tumours

Of 67 patients with cerebral tumours studied by MRI, 60 underwent stereotactic biopsy for histological diagnosis. The data from MRI were compared with those obtained from the CT scan with regard to the pathological diagnosis. The tumoural nature and extent of a lesion were better revealed by MRI. The single or multiple localization of the process was also seen better by MRI. Moreover, the sagittal-plane views shown by MRI provide much more accurate target placement and probe guiding for an orthogonal stereotactic approach. Finally, a post-biopsy MRI can show the biopsy site in relation to the tumour better.     

Stereotactic CT scanning for the biopsy of intracranial lesions and functional neurosurgery

This report describes a system for incorporation of stereotactic CT scanning data, stereotactic arteriographic data and a computer-generated stereotactic atlas into a three-dimensional matrix utilizing an operating room computer. 86 patients have undergone computer-assisted stereotactic biopsies of intracranial lesions without mortality or neurologic morbidity. Neuroablative and neuroaugmentative procedures have been performed on 5 patients using the CT stereotactic atlas with good correlation with target points determined by ventriculography and microelectrode recording.     

Late considerations in the treatment of low-grade malignancy cerebral tumors with iodine-125 brachytherapy

The authors report their series of 45 patients harboring inoperable, low-grade cerebral neoplasms, treated in the past 6 years with 125I stereotactic brachytherapy. The majority of these tumors were grade I and II astrocytomas and oligodendrogliomas (82.2%). A 2.6- to 6-year follow-up shows good results in 65.6% with reduction or disappearance of the lesions on CT images and good social reentry. Nine patients (23.7%) died prior to follow-up. Young patients (less than 40 years) responded well to interstitial radiotherapy, while patients over 40 with the same histological findings of low-grade tumors responded poorly to this type of treatment. Diffuse infiltrating cortico-subcortical tumors, optochiasmatic gliomas, hypothalamic and lower brainstem neoplasms do not respond satisfactorily to 125I radioisotope implantations.     

Stereotactic neurosurgery and computerized tomographic scanning

The marriage of computerized tomographic (CT) scanning and stereotactic surgery opens up new technical possibilities, as it becomes feasible to introduce a probe into any lesion which is identified on a CT scan. The various CT stereotactic techniques are reviewed, and generally involve four variations. The head holder of a standard stereotactic apparatus can be adapted to the CT scanner to interdigitate the coordinates of both devices in a known relationship. Second, some types of CT scanners allow the visualization of the vertical coordinate. Third, a stereotactic microdrive can be incorporated into the scanner. Finally, a simple aiming device can be attached to the patient's head and repeated scans taken as the probe is advanced to the target. Various authors have reported the use of techniques for biopsy, aspiration of cysts or hematomas, insertion of radioisotopes, or as an adjunct to open surgery.     

Experience using two CT-guided stereotactic biopsy methods

15 patients had intracranial CT-guided stereotactic biopsies. Biopsies were performed either with a Riechert-Mundinger stereotactic frame modified for use in the CT or by using the CT scan to establish the relationship of the intracranial lesion to identifiable bony landmarks, and subsequently performing the biopsy in a standard stereotactic frame. Both systems provided safe and accurate methods for obtaining intracranial tissue.     

CT Perfusion Imaging as an Early Biomarker of Differential Response to Stereotactic Radiosurgery in C6 Rat Gliomas

Background

The therapeutic efficacy of stereotactic radiosurgery for glioblastoma is not well understood, and there needs to be an effective biomarker to identify patients who might benefit from this treatment. This study investigated the efficacy of computed tomography (CT) perfusion imaging as an early imaging biomarker of response to stereotactic radiosurgery in a malignant rat glioma model.

Methods

Rats with orthotopic C6 glioma tumors received either mock irradiation (controls, N = 8) or stereotactic radiosurgery (N = 25, 12 Gy in one fraction) delivered by Helical Tomotherapy. Twelve irradiated animals were sacrificed four days after stereotactic radiosurgery to assess acute CT perfusion and histological changes, and 13 irradiated animals were used to study survival. Irradiated animals with survival >15 days were designated as responders while those with survival ≤15 days were non-responders. Longitudinal CT perfusion imaging was performed at baseline and regularly for eight weeks post-baseline.

Results

Early signs of radiation-induced injury were observed on histology. There was an overall survival benefit following stereotactic radiosurgery when compared to the controls (log-rank P<0.04). Responders to stereotactic radiosurgery showed lower relative blood volume (rBV), and permeability-surface area (PS) product on day 7 post-stereotactic radiosurgery when compared to controls and non-responders (P<0.05). rBV and PS on day 7 showed correlations with overall survival (P<0.05), and were predictive of survival with 92% accuracy.

Conclusions

Response to stereotactic radiosurgery was heterogeneous, and early selection of responders and non-responders was possible using CT perfusion imaging. Validation of CT perfusion indices for response assessment is necessary before clinical implementation.     

X-ray and magnetic resonance stereotaxy for functional and nonfunctional neurosurgery

By means of new plastic stereotactic ring and head fixers, stereotactic procedures can be combined with MRI, with stereotactic coordinates obtained from the MRI images. The method was rechecked against CT stereotaxy and shows a good correspondence of the target coordinates. With MRI stereotaxy, structures near bony regions will be more accessible than with CT stereotaxy. Moreover, the MRI procedure seems to have advantages for functional therapy without the necessity of contrast ventriculography.     

CT follow-up and clinical outcome in severe traumatic brain injury patients

Determining a patient's prognosis after severe traumatic brain injury remains difficult and complex. The purpose of the present study was following up patients with severe traumatic brain injury by correlating their clinical outcome and sequential computer tomography (CT) findings. We investigated 51 patients who survived the first year following an accident. All patients underwent successive CT examinations within a maximum period of 2 years. The patients' outcomes depended on the underlying brain damage and are presented by the Glasgow Outcome Scale. Based on the investigated data we concluded that the worst outcomes were experienced by patients with initial massive cerebral edema, extensive subdural hematoma and intraventricular hemorrhage, followed by stroke as subacute CT finding and cerebral atrophy as chronic finding visible at follow-up CT scans. The majority of lesions identified by CT scan were found in the frontal lobes, basal ganglia, and temporal lobes. We suggest that CT examination still represents a simple and useful tool in attempting to predict the clinical outcome in patients with severe traumatic brain injury.     

A new apparatus for CT-guided stereotactic surgery

Combining whole-body CT scan with a stereotactic system, the authors have developed and applied clinically an apparatus which readily provides intraoperative CT images, making it possible to confirm the location of the target point and ascertain the intraoperative environment. It takes about 9 s to obtain a CT image. Our purpose is to make stereotactic surgery, a kind of blind surgery, as safe and reliable as a visualized procedure by intraoperative CT scanning. By the method, in which there is very little invasion under local anesthesia, evacuation of deep-seated intracerebral hematomas as well as brain abscesses and also biopsy or brachytherapy of brain tumors in the brain can be done with safety and reliability.     

Stereotactic biopsy for deep-seated intracerebral lesions. Correlation between computer tomography, positron emission tomography and electrophysiological activity

In 16 cases of stereotactic deep brain biopsy, a correlative study was made by computer tomography, positron emission tomography, and electrophysiological depth recording. This multimodal study is shown to be of great value in stereotactic biopsy of deep-seated cerebral lesions.     

Transcranial Doppler ultrasonography: stereotactically guided examinations using magnetic resonance angiography]

The accurate localization of specific intracranial blood vessels is a major difficulty with transcranial Doppler sonography (TCD). It was the purpose of this study to develop a system enabling stereotactic navigation during a TCD examination on the basis of high-resolution three-dimensional magnetic resonance angiographic (MRA) data. During TCD, the examiner is provided--on a computer screen--with a projected view of the respective intracranial vessel anatomy. With the aid of an optoelectronic localization system, the spatial orientation and localization of the US probe is determined in real time, and correlated with the patient's MRA data using a dedicated stereotactic mask. Subsequently, the US beam and the points of insonation are displayed on the screen overlaid on the vessel anatomy. In this way the examiner gains real time control of the localization of the respective intracranial vessel insonated. Points of insonation can be stored and recalled for follow-up examinations. In addition to the successful verification of the system, it was shown that, in comparison with conventional TCD, stereotactic navigation distinctly improves the reproducibility of repeat TCD examinations.     

Role of computerized transverse axial tomography on stereotactic surgery of the diencephalon. A preliminary report of 67 cases.

67 cases of various functional disorders of the diencephalon were examined by EMI scanner. The patients were composed of 38 cases of parkinsonism, 7 cases of thalamic syndrome, 6 cases of choreoathetoid movement, 2 cases of dystonia, 11 cases of involuntary movement of unknown etiology and 1 case of torticollis, tic, and ballismus, respectively. In parkinsonism, 79% showed diffuse cerebral atrophy, 5% had focal low density in the substantia nigra and the thalamus, whereas 16% remained normal. Pre- and postoperative assessment with CT scan was briefly discussed with reference to stereotactic surgery of the diencephalon.     

Stereotactic interstitial brachytherapy--current concepts and concerns in twenty patients

Recent advances in imaging and stereotactic techniques have resulted in wider application of interstitial brachytherapy (IBT) for brain tumors. The advantages of brachytherapy alone or in combination with teletherapy have been detailed, and may be responsible for increasing survival time. We report the preliminary results of 20 patients who underwent CT stereotactic IBT for malignant brain tumors. Despite both old and recent evidence about the efficacy of IBT, concerns remain about the proper grade neoplasm, the target, the dose, and the timing for treatment. Current usage of IBT should be limited to centers with both stereotactic and radiotherapeutic expertise, and where the risks and benefits are being investigated.     

Computer tomography-controlled stereotactic surgery

In computed tomography (CT)-controlled stereotactic surgery, the coordinate system of the CT scanner is applied to determine the target depth and direction as well as for readjustment of final probe direction. This method can be used for all types of stereotactic surgery for the brain.     

Real-time cortical cerebral blood flow follow-up in conscious,freely moving rats by laser Doppler flowmetry

This article describes a laser Doppler flowmetry (LDF) system that enables repeated measurements and thereby long-term followup of cortical cerebral blood flow (CBF) in awake and freely moving rats. The system consists of a specially designed flow probe adapter, a flow probe connector, and a LDF flow probe, which may thereby rotate through its own axis. During the experiment, the flow adapter is permanently mounted onto the rat's skull bone. A thin layer of skull bone is left intact at the site for cortical CBF measurements. The probe connector and the flow probe may be repeatedly detached and remounted to the adapter, which allows for cortical cerebral blood flow recording from exactly the same anatomical location. The laser Doppler flowmetry system enables stable cortical CBF recordings in the conscious rat while it moves freely in a bowl cage.     

Technique of stereotactic biopsy of two cranial target employing spherical coordinates to define a single trajectory

A 'spherical coordinate system' has been developed to allow either stereotactic biopsy of two intracranial lesions using a single predetermined trajectory or biopsy of a single lesion through an existing burr hole. By means of the Gildenberg technique, the CT coordinates of the targets (or target and burr hole) are obtained. These are employed in three simple trigonometric equations to give three coordinates-two angles for the probe carrier (theta and alpha) and the radius (T) of a sphere, defined by one target as the center and the other target on the surface. These can be utilized in the Todd-Wells stereotactic frame. This system was evaluated using hollow skulls and crossed 30-gauge wire for phantom targets. The system was tried on ten different target combinations, and eight successful trajectories were obtained to within 3 mm. Two target combinations were inaccessible because of technical limitations of the Todd-Wells frame. This 'spherical coordinate system' can decrease the time to localize multiple targets as well as minimize the number of passes.     

Reproducibility of repeated mountings of a noninvasive CT/MRI stereoadapter

The reproducibility of a noninvasive computed tomography (CT)/magnetic resonance imaging stereoadapter was tested on 12 healthy volunteers. The adapter was easy to mount and detach without discomfort. Two repeated mountings of the adapter showed a good reproducibility in relation to the scalp. When extrapolated to a hypothetical target in the right thalamus, the mean differences between the two mountings were 0.07 mm in the lateral, 0.16 mm in the anteroposterior and 0.17 mm in the height coordinates. This high degree of reproducibility seems to permit a safe CT-guided functional stereotaxis, where the preoperative CT scanning can take place on one day and the surgery may be performed on any other suitable day.