Acute changes in blood pressure following vascular diseases in the brain stem

The relationship of the type of acute change in blood pressure to the site of the brain lesion, following cerebral hemorrhage and infarction, were studied in 108 patients in whom autopsy was performed. No significant changes in blood pressure were observed in cases with lesions localized rostral to the midbrain and in the medulla oblongata. The pressor response characteristic in primary pontine lesions, either hemorrhage or infarction, also was demonstrated in the cerebral hemorrhage with fourth ventricular and pontine extension. Blood pressure elevation was more marked with tegmental pontine lesions than when the lesion was in the basilar pons. Extension of the lesion into neighboring portions of the pons did not cause further change in blood pressure. The present results seem to suggest a positive role of the caudal brain stem, especially the pons, in the blood pressure elevation following the cerebrovascular accidents.

Further definition of the subthalamic target for arrest of tremor

✓ During stereotaxic procedures for the treatment of tremor, the simple introduction of a 1-mm diameter electrode in the subthalamus may arrest the tremor on the contralateral side. Placement of the electrodes in relation to the ventricular system and intercommissural (AC-PC) line was studied radiologically in 88 cases operated on. The proximity of the medial lemniscus and pyramidal fibers was assessed by means of electrical monopolar stimulation. A proportional reduction of the AC-PC line was made in all cases by dividing it in 10 equal parts. The resultant 10ths were squared to divide the areas above and below the line. The place where the tremor was arrested corresponded to a small area that extended just in front of the area of sensory responses and medial to the area of motor responses. It seemed to have a topographical organization, as the tremor could be selectively arrested in the arm or the leg. Analysis of results on anatomical grounds showed the area in question corresponded to the prelemniscal radiations that extend caudally as far as the mesencephalic tegmentum and end at the level of the AC-PC line.