Naomi Mutsuga

A newly designed nerve monitor for microneurosurgery: Bipolar constant current nerve stimulator and movement detector with a pressure sensor

SummaryThe authors describe a newly designed nerve monitor which is useful for numerous microneurosurgical procedures. Standard bipolar forceps are used to apply constant current stimulation. Muscle contraction evoked by the stimulation is detected by a small discshaped pressure sensor taped to the overlying skin. The responses are monitored both quantitatively on a liquid crystal display and qualitatively through an on-off auditory signal. Surgery can proceed without interruption. This apparatus can safely and reliably monitor the facial nerve, nerves involved in eye movements, lower cranial nerves and spinal nerves. This portable system weighs only 1.8 kg and can easily be used by a neurosurgeon.

Regional distribution of dopamine and norepinephrine in canine cerebral arteries — effect of pre- or postganglionic sympathetic denervation

The regional distribution of dopamine (DA) and norepinephrine (NE) was investigated in dog cerebral arteries using high performance liquid chromatography with electrochemical detection. The distribution patterns of these two amines differed and there was a wide fluctuation in the ratio between the amounts of DA and NE. The ratios of DA to NE in the anterior cerebral artery and the anterior inferior cerebellar artery were 2-4 times higher than in the basilar or middle cerebral arteries, thereby suggesting that DA plays a role other than that of precursor of NE. The concentrations of both amines following pre- or postganglionic sympathetic denervation (superior cervical ganglion) were investigated. After preganglionic denervation (decentralization), neither amine showed significant changes in concentration. Postganglionic denervation one week prior to sacrifice resulted in a reduction in the concentrations of both amines; however, decrease in the former was less. These results suggest that the origin of dopamine in the cerebral arteries differs from that of the sympathetic nerves, via the superior cervical ganglion.