✓ Persistent hemiballismus after stroke is often difficult to treat. The ballistic movement is sometimes so violent that progressive exhaustion results. The authors report two such cases, which were successfully treated by chronic thalamic stimulation. The lesions responsible for the ballistic movement in these patients were located near the subthalamic nucleus and in the putamen, respectively. The thalamic nucleus ventrolateralis and nucleus ventralis intermedius were stimulated with 0.2 to 0.3 msec pulses at 50 to 150 Hz and 4 to 7 V continuously during the day. Several weeks later, complete control of the hemiballismus was achieved during stimulation. The improvement was clearly not attributable to spontaneous recovery, because ballistic movement reappeared after termination of the stimulation. The stimulation has remained effective for more than 16 months in both cases without any serious complications. Chronic thalamic stimulation appears to be useful for controlling persistent hemiballismus, as it is for other involuntary movement disorders.
Report of two cases
Takashi Tsubokawa, Yoichi Katayama and Takamitsu Yamamoto
Yoichi Katayama, Takashi Tsubokawa, Tsuyoshi Maeda and Takamitsu Yamamoto
✓ In order to determine adequate therapeutic approaches for cavernous malformations of the third ventricle, the authors reviewed a series of five such malformations managed at their institution and nine others reported in the literature. Four subgroups were identified in terms of the site of origin and could be characterized by different clinical manifestations: visual field defects and endocrine function deficits in patients with malformations in the suprachiasmatic region (six cases); symptoms caused by hydrocephalus in those with malformations in the foramen of Monro region (five cases); and deficits of short-term memory in those with malformations in the lateral wall (two cases) or of the floor of the third ventricle (one case). Unlike cavernous malformations at other locations, malformations of the third ventricle frequently demonstrated rapid growth (43%) and mass effects (71%). The surgical or autopsy findings suggested that the growth was attributable to repeated intralesional hemorrhages. Extralesional hemorrhage was also not uncommon, occurring in 29% of patients. Such tendencies require the adoption of a more aggressive approach to this particular group of cavernous malformations as compared to those in other locations. The risks of regrowth and extralesional hemorrhage appear to be reduced only by complete excision. The surgical approaches adopted should be aimed at providing the best access to the site where the malformation has arisen. The translamina terminalis approach for cavernous malformations in the suprachiasmatic region, the transventricular or transcallosal interfornicial approaches for those in the foramen of Monro region and the transvelum interpositum approach for those in the lateral wall or the floor of the third ventricle appear to be appropriate. In order to select the adequate surgical approach, precise diagnosis of the site of origin is crucial. In addition to neuroimaging techniques, the patient's initial symptoms provide valuable information.
Takashi Tsubokawa, Yoichi Katayama, Takamitsu Yamamoto, Teruyasu Hirayama and Seigou Koyama
✓ Analysis of the authors' experience over the last 10 years has indicated that excellent pain control has rarely been obtained by thalamic relay nucleus stimulation in patients with thalamic pain. In the present study, 11 patients with thalamic pain were treated by chronic stimulation of the precentral gyrus. In eight patients (73%), the stimulation system was internalized since excellent pain control was achieved during a 1-week test period of precentral gyrus stimulation. In contrast, no clear effect was noted or the original pain was even exacerbated by postcentral gyrus stimulation. The effect of precentral stimulation was unchanged in five patients (45%) for follow-up periods of more than 2 years. In the remaining three patients, the effect decreased gradually over several months. This outcome was significantly better than that obtained in an earlier series tested by the authors with thalamic relay nucleus stimulation (p < 0.05). The pain inhibition usually occurred at intensities below the threshold for production of muscle contraction (pulse duration 0.1 to 0.5 msec, intensity 3 to 8 V). When good pain inhibition was achieved, the patients reported a slight tingling or mild vibration sensation during stimulation projected in the same area of distribution as their pain.
The authors discuss the possibility that, in deafferentation pain, sensory neurons below the level of deafferentation cannot exert their normal inhibitory influences toward deafferented nociceptive neurons because of the development of aberrant connections. Thus, while stimulation of the first- to third-order sensory neurons at the level of the thalamic relay nucleus or below cannot bring about good pain inhibition in patients with thalamic pain, activation of hypothetical fourth-order sensory neurons through precentral stimulation may be able to inhibit deafferented nociceptive neurons within the cortex. None of the patients developed either observable or electroencephalographic seizure activity.