Study on the pathophysiology of pallido-, spino-thalamo-cortical system in cases with intractable functional disorders

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(1) In cases with rigid-akinesia type Parkinson's disease(PD), frontal regional cerebral glucose metabolism(rCMRglu) was correlated with dopamine contents in the CSF of 3rd ventricle. Stereotactic posteroventral pallidotomy(PVP) was carried out in 13 cases with rigid-akinesia type PD with aid of depth microrecording. Before operation, a PET study has revealed low regional cerebral glucose metabolism in the prefrontal area in all the patients. Unilateral sequential opposite finger movement(SOFM) induced increase of regional cerebral blood flow(rCBF) both in the supplementary and primary motor area in the effective response groups. Electrophysiological study during the operation showed continuous high-frequency and high-amplitude spike discharges in the internal segment of globus pallidus(Gpi) in the effective response group. If the effect of nigrostriatal dysfunction was restricted in the nigro-striato-pallidal connections, characterized by overactivity in Gpi neurons, without extensive … More ly affecting the motor-related structures in the frontal cortex, we could expect to alleviate the parkinsonian symptoms, such as rigidity or bradykinesia, by pallidotomy(PVP). If, however, the dysfunction extended into the network of motor-related structures in the frontal cortex, particularly in the supplementary motor area, we could no longer expect to improve the parkinsonian symptoms.(2) Functional mapping study using PET scan and depth microrecording was carried out to elucidate the thalamocortical relation involved in tremor in cases with tremor type Parkinson's disease. In this type of PD, PET study revealed spot-shaped increased zone of rCMRglu and/or rCBF in the frontal precentral area on the side contralateral to tremor. Unilateral SOFM evoked increase of rCBF in the similar precentral area. Moreover, unilateral thumb brushing caused increase of rCBF in the postcentral area just caudal to the precentral rCBF increased zone. The cortical mapping studies revealed that rCMRglu and/or rCBF mainly increased in the primary motor cortex during the appearance of tremor. Both PET and functional MRI study showed spot-shaped high signal area (increased zone of rCBF) in the thalamic ventro-lateral area. Moreover, depth microrecording study showed rhythmic discharges synchronous with contralateral limb tremor in the similar area(=thalamic VIM : nucleus ventralis intermedius). It was postulated that both thalamic VIM and the cortical precentral area, which was functionally identified by brain mapping study, may play important roles in mediating and maintaining tremor in tremor type PD.(3) Based on the data obtained for the selective thalamotomy with aid of depth microrecording, it was postulated that functional change has occurred in the thalamic sensory nucles just rostral or bottom to original cerebrovascular lesion and in the cerebral cortex adjacent to the central sulcus in cases with thalamic pain.These changes may cause aberrant conduction of sensory signal or hypersensitivity to peripheral sensory stimulation. The therapeutic lesion created by thermo-coagulation or Gamma Knife aimed to ameliorate these abnormal functional states may relieve thalami pain.(4) A retrospective study was conducted to evaluate the effectiveness of Gamma Knife radiosurgery in the management of idiopathic trigeminal neuralgia. Radiosurgery was performed with a signal 4 mm isocenter targeted at the nerve root entry zone. Gamma Knife radiosurgery is an effective surgical attempt in the management of this intractable pain. These results also showed that peripheral sensory input may play important roles for the genesis of intractable trigeminal neuralgia. Less