Tohru Shibasaki

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.

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.

Pathophysiology of Central (Thalamic) Pain: A Possible Role of the Intralaminar Nuclei in Superficial Pain

In 15 patients with central pain (thalamic pain) after stroke, CT, PET scan and intraoperative thalamic microrecordings were performed. The results are considered together to evaluate a possible role of thalamic intralaminar nuclei in the genesis of central pain, especially of superficial pain. In the non-thalamic lesion group (deep pain dominant), thalamic background neural activity (BNA) was relatively high in Vim but low in CL. Conversely, in the thalamic lesion group (superficial pain dominant), thalamic BNA was higher in CL than in Vim, and markedly decreased in VC. In this group, regional cerebral oxygen consumption (rCMRO2) was relatively maintained, and regional oxygen extraction ratio (raOEF) and the relative value of regional cerebral glucose utilization (CMRGL), compared to rCMRO2, was increased in the cerebral cortex around the central sulcus. The genesis of superficial pain is discussed.

Traumatic giant aneurysm of the external carotid artery

Because the main trunks of the external carotid artery and maxillary artery are well protected from blunt trauma and superficial penetrating wounds through their course, traumatic aneurysms on these arteries are extremely rare. A 75-year-old woman had struck her occipital region against a door but there was no trauma to the mandibuloauricular region. After 1 month, she noticed a pulsatile mass below her right auricle. At operation an aneurysm was found to be located just distal to the origin of the maxillary artery.

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.

Correlation between the Neural Noise in the Thalamus after Cerebrovascular Disease and Computerized Tomography

The case is presented of a 45-year-old man who suffered from a sudden attack of unconsciousness with right hemiplegia and later developed a spastic hemiparesis accompanied by involuntary movement of the right upper limb. CT scan revealed an old putaminal hemorrhage and almost intact thalamus, but neural noise recordings during the stereotactic thalamotomy of this case showed marked decrease of the neural activity in the thalamus suggesting some functional changes.

Pain Relief by Dorsal Root Entry Zone Lesions in Intractable Pain due to Partially Injured Tibial Nerve

Successful treatment of intractable deafferentation pain by dorsal root entry zone (DREZ) operation in a patient with chronic tibial nerve injury is presented. This 70-year-old man had a crush injury on his right foot, and intractable pain developed 2 months after ther injury. At operation, evoked potentials were directly recorded from the dorsal roots. After determining the root that presented maximum response to tibial nerve stimulations. DREZ lesions were made. The effectiveness of DREZ operation in root-intact deafferentation pain is discussed. And, the usefulness of teh directly recorded root potentials evoked by stimulation of the proximal protion of the injured nerve is emphasized.