Kiyoaki Tanaka

Methionine positron emission tomography for differentiation of recurrent brain tumor and radiation necrosis after stereotactic radiosurgery--in malignant glioma.

ObjectFollowing stereotactic radiosurgery (SRS), we examined how to differentiate radiation necrosis from recurrent malignant glioma using positron emission tomography (PET) with11C-methionine (Met).MethodsMet-PET scans were obtained from 11 adult cases of recurrent malignant glioma or radiation injury, suspected on the basis of magnetic resonance images (MRI). Patients had previously been treated with SRS after primary treatment. PET images were obtained as a static scan of 10 minutes performed 20 minutes after injection of Met. We defined two visual grades (e.g., positive or negative Met accumulation). On Met-PET scans, the portion of the tumor with the highest accumulation was selected as the region of interest (ROI), tumor-versus-normal ratio (TN) was defined as the ratio of average radioisotope counts per pixel in the tumor (T), divided by average counts per pixel in normal gray matter (N). The standardized uptake value (SUV) was calculated over the same tumor ROI. Met-PET scan accuracy was evaluated by correlating findings with subsequent histological analysis (8 cases) or, in cases without surgery or biopsy, by the subsequent clinical course and MR findings (3 cases).ResultsHistological examinations in 8 cases showed viable glioma cells with necrosis in 6 cases, and necrosis without viable tumor cells in 2 cases. Three other cases were considered to have radiation necrosis because they exhibited stable neurological symptoms with no sign of massive enlargement of the lesion on follow-up MR after 5 months. Mean TN was 1.31 in the radiation necrosis group (5 cases) and 1.87 in the tumor recurrence group (6 cases). Mean SUV was 1.81 in the necrosis group and 2.44 in the recurrence group. There were no statistically significant differences between the recurrence and necrosis groups in TN or SUV. Furthermore, we made a 2 x 2 factorial cross table (accumulation or no accumulation, recurrence or necrosis). From this result, the Met-PET sensitivity, specificity, and accuracy in detecting tumor recurrence were determined to be 100%, 60%, and 82% respectively. In a false positive-case, glial fibrillary acidic protein (GFAP) immunostaining showed a positive finding.ConclusionThere were no significant differences between recurrent malignant glioma and radiation necrosis following SRS in Met-PET. However, this study shows Met-PET has a sensitivity and accuracy for differentiating between recurrent glioma and necrosis, and presents important information for developing treatment strategies against post radiation reactions.

Effects of electrical stimulation on intracranial pressure and systemic arterial blood pressure in cats. Part II: Stimulation of cerebral cortex and hypothalamus.

This experimental work was carried out to examine whether activation of autonomic cortical and hypothalamic areas by electrical stimulation is related to changes in the intracranial pressure (ICP) in cats anaesthetized lightly with sodium pentobarbital. Electrical stimulation was performed using a concentric electrode with a train of electrical pulses (pulse duration, 0.4 ms; frequency, 40 Hz; intensity, 50-400 microA). Stimulation of sites in the anterior cingulate gyrus produced a rise in ICP associated with a fall in systemic arterial blood pressure (BP) or with no change in BP. Stimulation of sites in the anterior hypothalamus produced a fall in BP with an increase in ICP. Stimulation of sites in the area extending from the anterior hypothalamus to the posterior hypothalamus produced rises in BP and ICP. These observations suggest that activation of autonomic cortical and hypothalamic areas is involved in changes in ICP.

Direct Observation of Autonomic Nerve Activity in Experimental Acute Brain Swelling

Increase in intracranial pressure (ICP) produces changes in blood pressure (BP) and heart rate that are ascribed to alterations of autonomic nerve activity (Cushing 1901). We have reported that the renal nerve activity, which represents sympathetic vasomotor activity, increased when the ICP was raised, associated with a rise in BP (Tanaka et al. 1976; Nakamura et al. 1980). In the present study we made direct and simultaneous observation of the cardiac vagal and the cervical sympathetic nerve activities in the increased ICP, using the epidural balloon compression model.

Pressure Wave-Like Changes in ICP Produced by Electric Stimulation of the Brainstem, Hypothalamus and Cerebral Cortex in Cats

Initiation of intracranial pressure waves is often associated with changes in vital signs such as respiration and systemic arterial blood pressure (BP). The observations suggest that the brainstem (Furuse et al. 1982), hypothalamic and autonomic cortical areas, which are known to control or modify BP and respiration (Folkow et al. 1965, Goadsby et al. 1983), have an intimate relationship to a change in intracranial pressure (ICP). This experimental work attempts to demonstrate that activation of the neurones by electric stimulation in the brain induces a change in ICP similar to spontaneous pressure waves.

A Microstructural Study of Oedema Resolution

The infusion model was used to investigate the resolution mechanism of vasogenic brain oedema. HRP dissolved in autoserum was infused into the white matter of cats. The infused protein in the oedema fluid seemed not only to be absorbed by pinocytosis or phagocytosis, as has been reported previously, but also to be quickly washed out via the perivascular space of the post-capillary venules. Smaller molecules such as HRP moved faster than serum albumin in these spaces after the infusion pump was turned off. Rapid flow of extracellular fluid via the perivascular space may play an important role on the resolution process of vasogenic brain oedema by accelerating diffusion.

Effect of Steroids on the Resolution Process of Edema

The mechanism of the action of steroids on brain edema is not fully understood despite its long history. Recently it has been reported that the beneficial effect of steroids might be attributed to inhibition of edema spread or acceleration of edema resorption (Matsuoka, Hossmann 1981; Hossmann et al. 1983; Fenstermacher et al. 1984; Hartmann et al. 1984). Almost all experimental models of edema must involve the formation process and the resolution process of edema which can not be separated from each other experimentally. Using the direct infusion model of edema, the only model in which one can separate these two processes, the question of whether the effect of steroids is exerted on the resolution process was investigated.

Intracranial Pressure on Pre- and Post-Shunt Surgery in Patients with Normal Pressure Hydrocephalus (NPH)

Although shunt surgery is a generally accepted way of treating patients with NPH, there are only a few papers (Symon and Dorsch 1975) which report the changes in ICP after shunt. Without knowledge concerning ICP changes after shunt, we are apt to consider that the closing pressure of the shunt system which was installed was not low enough or that the patient was not a good candidate for the shunt surgery when it was not effective. In order to supplement the basic data, not only ICP changes but also changes in pressure volume index (PVI), outflow resistance (Rout) and the profile of B-waves after shunt were investigated.

A Microstructural Study of Spinal Cord Edema

The experimental spinal cord edema was produced in a cat by the infusion method of Marmarou. Horseradish peroxidase (HRP) dissolved in autoserum of a cat was used as a tracer. After laminectomy, a 30-gauge needle was inserted into the intumescentia cervicalis. A total amount of 20 microliters of a tracer was infused at a rate of 10 microliters/hr. The structural features were studied immediately and 3 days after infusion. Immediately after infusion, HRP was noted in the infused white and gray matters. Though the perivascular space in the white matter at the infused site was widely distended and filled with HRP, the space in the gray matter was not distended but filled with HRP. HRP which was observed along vessels led to the surface of the spinal cord. Swelling of astrocyte was not observed. Three days after infusion, the extracellular space and the perivascular space in the infused white matter were still expanded but were not filled with HRP. The fine structural features were similar to the findings as seen in Marmarous infusion type of brain edema. Using this model, it seems to be feasible to study the resolution process of spinal cord edema.

The Effect of Experimental Spinal Cord Edema on the Spinal Evoked Potential

Experimental spinal cord edema was successfully produced in the cat intumescentia cervicalis by the infusion method of Marmarou. The water content around the infusion site significantly increased to 75.9% from the normal value of 69.8% of white matter in the lateral column, with the infusion of 20 microliters of autoserum. The edema was observed for a length of ca.20 mm, spreading mainly longitudinally in the lateral column. The spinal evoked potential was measured four times on the course of infusion and the N1 peak latency at the end of infusion did not show any significant difference compared to the value before infusion. This model may contribute to basic understanding of pathophysiology of spinal cord edema by changing the nature and the volume of infusate, and the location of infusion, according to the experimental purpose.

A case of a vascular anomaly with peculiar venous drainage

Introduction Venous abnormalities are often seen in vascular malformations and SturgeJWeber syndrome [14] . For example, lack of superficial cortical veins, nonfilling of the dural sinuses, and enlargement of the deep veins may be observed in Sturge-Weber syn~ drome [2-4]. Cerebral venous occlusion or maldevelopment have been suggested as possible pathogeneses [2-4]. We present a rare case of a venous anomaly exhibiting an abnormal venous drainage pattern and discuss its possible aetiology in relation to the embryological development of the falcine sinus and associated vascular structures.