Shuji Sakata

Aneurysm of the posterior cerebral artery: report of eleven cases--surgical approaches and procedures.

Eleven cases of an aneurysm of the posterior cerebral artery are reported. All 11 aneurysms were saccular, and 3 were either giant or large. The aneurysms arose from the P1 segment in three patients, the P1-P2 junction in three patients, the P2 segment in three patients, and from the P3 segment in two patients. In all, 10 patients underwent surgery. All P1 and P1-P2 junction aneurysms were treated with the pterional approach. Three P2 and two P3 aneurysms were managed by the subtemporal approach. Two small aneurysms in the series were treated by coating the aneurysmal dome, two by clipping the afferent artery, and all other saccular type aneurysms were treated by clipping the aneurysmal neck. Seven patients had either an excellent or good outcome; two had poor results; and one patient died. The operative approaches and procedures are also discussed in relation to the anatomy of posterior cerebral artery aneurysms.

Aneurysm of the Posterior Cerebral Artery

Eleven cases of an aneurysm of the posterior cerebral artery are reported. All 11 aneurysms were saccular, and 3 were either giant or large. The aneurysms arose from the P1 segment in three patients, the P1-P2 junction in three patients, the P2 segment in three patients, and from the P3 segment in two patients. In all, 10 patients underwent surgery. All P1 and P1-P2 junction aneurysms were treated with the pterional approach. Three P2 and two P3 aneurysms were managed by the subtemporal approach. Two small aneurysms in the series were treated by coating the aneurysmal dome, two by clipping the afferent artery, and all other saccular type aneurysms were treated by clipping the aneurysmal neck. Seven patients had either an excellent or good outcome; two had poor results; and one patient died. The operative approaches and procedures are also discussed in relation to the anatomy of posterior cerebral artery aneurysms.

Effects of thalamic parafascicular stimulation on the periaqueductal gray and adjacent reticular formation neurons. A possible contribution to pain control mechanisms

To investigate the mechanism of analgesic effect of electrical stimulation of the thalamic parafascicular nucleus (Pf), we studied modulations of neuronal activities in the periaqueductal gray (PAG) and the adjacent reticular formation (RF) in response to Pf electrical and peripheral noxious stimulations in the rat. Extracellular single unit activities were recorded from 129 neurons in the PAG and adjacent RF under light halothane anesthesia. Pf stimulation caused neuronal responses in approximately 80% of the PAG and adjacent RF neurons, and noxious stimulation in 75%, with predominant excitatory responses to either stimulation. When the responses to the two stimuli were tested in the same neurons (n = 69), 91% responding to noxious stimuli also responded to Pf stimuli, again with predominant excitatory responses to either stimulation. The PAG and adjacent RF neurons that were verified antidromically to project to the nucleus raphe magnus (NRM), showed a similar pattern of response (n = 20). These results suggest that a sizeable population of neurons in the PAG and adjacent RF receives excitatory effects from the Pf and noxious afferents, and that part of these neurons projects to the NRM, which inhibits the dorsal horn cells of the spinal cord (the descending pain suppression system). Thus, part of the mechanism of the analgesic effects of Pf stimulation is due to activation of the descending pain suppression system by exciting the PAG and adjacent RF neurons. A possible role of noxious afferents on the negative feedback to pain mediation through this descending system also has to be considered.

Intracranial pial single-channel arteriovenous fistula presenting with significant brain edema

The authors report a rare case of pial single-channel arteriovenous fistula presenting with significant brain edema. A 51-year-old woman was admitted with a 5-day history of headache and nausea, followed by consciousness disturbance. Computed tomography showed cerebellar swelling with obstructive hydrocephalus. Magnetic resonance imaging revealed extensive vasogenic edema in the cerebellum bilaterally. Angiography demonstrated 2 different arteriovenous shunts (AVSs) at peripheral branches of the right anterior inferior cerebellar artery. One was located on the suboccipital surface. It drained through a dilated inferior vermian vein and emptied retrogradely into the contralateral cerebellar veins with marked stagnation. Focal stenosis of the dilated draining vein was present. The other AVS was located on the petrosal surface, which had a slow flow with no angiographic evidence of venous congestion. Given that the latter was believed to be asymptomatic, the former AVS was excised, and histological examination revealed that the lesion consisted of a direct communication of multiple arterial feeding vessels with a single vein, consistent with a diagnosis of pial single-channel arteriovenous fistula. The restriction of venous drainage presumably caused venous hypertension, leading to the brain edema and neurological symptoms.

Striatal dysfunction in Rolling mouse Nagoya: an electrophysiological study

To elucidate the neuronal mechanism of the motor disturbances of the Rolling mouse Nagoya (rolling, genotype rol/rol), an experimental neurologic mutant mouse, we studied the physiological characteristics of neurons of the globus pallidus (GP) in rolling, comparing them with those of the behaviorally normal heterozygotes (+/rol) and normal controls (+/+). Forty-nine units in rolling, 41 in heterozygotes and 48 in controls were recorded under urethane anesthesia. The group mean of the interspike interval (ISI) of the spontaneous unit discharges was significantly shorter in rolling (42.2 +/- 2.6 msec, mean +/- SEM) than that of controls and of heterozygotes (55.4 +/- 2.4 msec, P < 0.001 and 50.4 +/- 2.6 msec, P < 0.05, respectively), indicating a significantly higher rate of spontaneous unit activity in the GP of rolling. In the controls and heterozygotes, about 60% of the GP neurons responded to striatal (ST) electrical stimulation with a predominantly inhibitory response, whereas a significantly smaller number of the GP neurons (22%, P < 0.001) exhibited inhibitory responses in rolling. The positive field potentials recorded in the GP evoked by ST stimulation were significantly smaller in amplitude in rolling (1.04 +/- 0.10 mV, mean +/- SEM) than that of the controls and heterozygotes (1.78 +/- 0.15 mV, P < 0.001 and 1.97 +/- 0.17 mV, P < 0.001, respectively). These results are in agreement with our previously reported findings of increased glucose metabolism and reduced concentration of GABA in the GP and substantia nigra pars reticula (SNr) in rolling.(ABSTRACT TRUNCATED AT 250 WORDS)