Satoru Horikoshi

Pathophysiology of central (thalamic) pain: combined change of sensory thalamus with cerebral cortex around central sulcus.

In 13 patients with central (thalamic) pain after stroke, CT, MRI, PET scan and intraoperative thalamic microrecordings were performed. Electrophysiological studies showed that irregular burst discharges were often encountered in the posterolateral thalamus. The more often the irregular burst discharges were encountered, the greater the decrease of sensory response in the posterolateral thalamus. Metabolic studies showed that regional cerebral glucose metabolism decreased in both the posterolateral thalamus and in the cortical postcentral area on the lesioned side in all cases. In the thalamic lesion cases in which many irregular burst discharges were found in the posterolateral thalamus, regional cerebral glucose metabolism and the relative value of glucose to oxygen metabolism increased in the cortical precentral area on the lesioned side. It was suggested that decreased activity with abnormal burst discharge in the posterolateral (sensory) thalamus associated with changes in cortical activity adjacent to the central sulcus might be related to the genesis of central (thalamic) pain. It is emphasized that cortical activity decreased in the postcentral area, but often increased in the precentral area.

Ossification of the cervical ligamentum flavum

A case of a 61-year-old man with ossification of the cervical ligamentum flavum is reported. The ossification was located on the left side of C3-4. The symptoms improved with laminectomy and resection. Ossification of the ligamentum flavum usually occurs in the lower thoracic spine, and is rare in the cervical region. Including the present one, only eight cases have been reported to our knowledge. The clinical features and pathogenesis are discussed.

The Possible Role of the Cerebral Cortex Adjacent to the Central Sulcus for the Genesis of Central (Thalamic) Pain—a Metabolic Study

In nine patients with central (thalamic) pain after stroke, X-CT, MRI, PET scan and intraoperative thalamic microrecordings were performed. The PET studies made use of Sokoloffs method with 18FDG and a steady-state method with C15O2-15O2. CT scan and MRI revealed definite thalamic damage (Th) in 3 cases, putaminal damage (Put) in 3 cases, combined damage (Th + Put) in one case, and cortical (parietal) damage in 2 cases. In patients with a subcortical lesion, the greater the severity of superficial pain, the higher was the relative value of regional cerebral glucose metabolism (rCMRGlu) as compared to oxygen metabolism (rCMRO2) in the cerebral cortex around the central sulcus on the damaged side. Also, in a case with combined (Th + Put) lesion, regional oxygen extraction ratio (rOEF) was increased in this area. Moreover, in another case, central pain disappeared after a small subcortical haemorrhage in the same structure. In all patients including those with a cortical lesion, rCMRGlu was decreased in the postero-lateral (sensory) thalamus on the invalued side. The possible role of the cerebral cortex around the central sulcus for the genesis of central pain is discussed.

Assessment of malignancy of glioma by positron emission tomography with 18F-fluorodeoxyglucose and single photon emission computed tomography with thallium-201 chloride

Abstract The histological diagnosis and proliferative potential measured by bromodeoxyuridine (BrdU) labelling index (LI) were corelated with preoperative CT and contrast-enhanced, MRI, 18F-flurodeoxyglucose positron emission tomography (PET) and 201T1 single photon emission computed tomography (SPECT) in 43 patients with various grades of glioma. 201T1 SPECT had slightly higher sensitivity to tumours with BrdU LI N 5 % (showing 10/10) than 18F-FDG PET (7/8 tumours). 18F-FDG PET was better for identifying tumours of BrdU LI < 1 % (13/15) than 201T1 SPECT (13/22). Accumulation of 201T1 in the tumour was slightly different from contrast enhancement on CT and/or MRI, and gave “false-postive” results in some low-grade gliomas. However, 201T1 SPECT, which is available in many hospitals and may cost less, provided useful information to supplement that from CT and MRI.

General activation of cerebral metabolism with speech: a PET study

We report the pattern of metabolic activation of the brain associated with speech, using 15O positron emission tomography (PET) in normal volunteers, as well as patients with or without language deficit. 15 trials were performed on 13 subjects. Regional oxygen metabolism with the subjects at rest was compared to that during a speech-from-memory task. As expected, there was strong activation of Brocas area and the medial left temporal lobe, corresponding to the motor speech and memory aspects of the task. In addition, both cerebellar hemispheres and pre-motor areas, as well as the right frontal operculum, supplementary motor area and right parietal lobe were active. This technique provided insight into the mechanism of aphasia in two subjects, even in one whose traditional language areas were structurally and metabolically intact at rest. We conclude that this practical activation technique may be useful not only in studying the physiology of normal brain, but also in understanding functional responses to disease.

Parkinsonian Rigidity, Dopa-Induced Dyskinesia and Chorea - Dynamic Studies on the Basal Ganglia-Thalamocortical Motor Circuit Using PET Scan and Depth Microrecording

Regional cerebral glucose metabolism (rCMRGlu-18FDG) was measured in 6 cases with rigid type Parkinsons disease (PD) (2 cases with dopa-induced dyskinesia = DID), 6 cases with chorea (Ch), 5 cases with essential tremor (EssT) and 2 cases with normal subjects (N). The effects of L-Dopa on rCMRGlu was studied in 3 cases with PD. With the aid of depth microrecording study, stereotactic pallidotomy was performed in all cases with PD. Thalamotomy was performed in 3 cases with Ch. In the EssT and N group, the metabolic pattern was high in the frontal cortex (FCx) but low in the lenticular nucleus (LN). In contrast, all cases with a rigid type PD showed lower rCMRGlu in FCx (premotor, prefrontal area). However, 4 out of 6 cases were higher in LN than the control group. Administration of L-Dopa shifted rCMRGlu toward the normal pattern in this group. Five out of 6 cases with Ch represented higher rCMRGlu in FCx (3 focal, 2 diffuse) but lower in LN. Moreover, when DID occurred, it showed almost the same pattern as in Ch. Electrophysiological studies showed high background neuronal activity (BNA) in the medial segment of the globus pallidus (GP) but low BNA in the lateral segment of the GP in the rigid type of PD. In cases with Ch, irregular burst discharges were often encountered in ventro-oral thalamus. From these results, the on-going changes of basal ganglia-thalamocortical motor circuit in cases with a rigid type PD, DID and Ch are discussed. The underlying mechanisms of Parkinsonian rigidity was considered to contrast with those of DID and Ch within the same motor circuit.

Positron emission tomography with 4-[18F]fluoro-L-m-tyrosine in MPTP-induced hemiparkinsonian monkeys

PET imaging studies with 4-[18F]fluoro-L-m-tyrosine (FMT) in normal macaca monkeys showed selective accumulations of radioactivity in the striatum with time. In monkeys rendered hemiparkinsonian by intracarotid infusion of l-methyl-4-phenyl-l,2,3,6-tetrahydropyridine (MPTP), FMT uptake was eliminated in the lesioned striatum. FMT-PET studies were able to detect dopaminergic terminals in both normal and hemiparkinsonian monkeys, and clearly showed a reduction in aromatic L-amino acid decarboxylase (AAAD) activities in the MPTP-lesioned striatum. These results show that FMT is promising as a PET tracer for the evaluation of central dopaminergic systems in parkinsonism.

Calcified astrocytoma of the amygdalo-hippocampal region in children.

Three pediatric cases of temporal lobe seizure due to calcified glioma of amygdalo-hippocampal region are described. Computed tomography and magnetic resonance imaging showed dense calcification with no postcontrast enhancement in the amygdalo-hippocampal region. Positron emission tomography showed low oxygen metabolism, low glucose metabolism, hypermetabolism of amino acids, and low regional cerebral blood flow in the tumors. Single photon emission computed tomography showed a high accumulation of201Tl chloride and123I-isopropyl iodoamphetamine in one tumor, but otherwise low radioisotope uptake. These studies indicated lowgrade malignancies. The patients were treated by partial tumor removal and radiotherapy. Histological examination of the tumor specimens showed astrocytoma with interstitial calcification. One patient died due to tumor recurrence, while the others are doing well with minimal seizure. We recommended temporal lobectomy in similar cases to achieve complete remission.

Visualization of Dopamine Nerve Terminals in Monkey by Positron Emission Tomography Using 4-[18F]Fluoro-L-m-Tyrosine

4-[18F]Fluoro-L-m-tyrosine (FMT) is an L-Dopa analog that essentially follows the L-Dopa metabolic pathway, but without 3-O-methylation or extensive peripheral metabolism. As such, FMT may serve as a useful probe of striatal dopaminergic function with positron emission tomography (PET). FMT was synthesized, as previously described by Perlmutter et al. [Appl Radiat Isot 1990;41:801-807]. Scanning was undertaken with the SHR2000 positron tomograph (image spatial resolution, 3.5 x 4.5 x 6.5 mm). Two Macaca monkeys were anesthetized with ketamine (10 mg/kg) and pentobarbital (20 mg/kg). FMT was administered intravenously (5-6 mCi; specific activity 1-2 Ci/mmol) following carbidopa pretreatment (5 mg/kg i.v., 60 min before FMT administration). Dynamic image acquisition was done for 2 h immediately after tracer injection. This emission acquisition involved twelve 2-min frames followed by nine 4-min frames, and six 10-min images. Arterial blood samples were collected according to a schedule for assay of plasma [18F] radioactivity. Specific uptake of FMT in aromatic L-amino-acid-decarboxylase-rich areas of the monkey striatum was observed with PET imaging. The striatum-to-cerebellum ratio of the accumulation increased over time to 3.0 at 2 h. These results show the promise of FMT as a PET tracer in evaluating the CNS dopaminergic system.

Malignancy of Glioma Estimated by PET-18F-FDG, PET-11C-Methionine, and SPECT-201Thallium

The detection of malignancy in glioma by histological studies and by the bromodeoxyuridine labeling index (BUdR-LI) have been well documented [1]. Increased glucose and amino acid uptake in glioma measured by positron emission tomography (PET) with fluorine-18-fluorodeoxyglucose (FDG) [2] and with carbon-11-methionine (Met) [3] have been reported capable of identifying the malignant grade of lesions. Single photon emission CT (SPECT) with 201-thalium chloride (Tl) is also valuable for determining the grade of malignancy [4]. A method of predicting malignancy preoperatively could alert the operating surgeon to the extent of tumor removal that will be required.