The use of experimental studies to reveal suspected neurotoxic chemicals as occupational hazards: acute and chronic exposures to organic solvents.

The nervous system differs from many other body organs by its central control of vital functions and its low regeneration capacity. Organic solvents have, as a group, been suspected to have neurotoxic effects. Because of their similar physical properties and the fact that in industrial uses, they are often present in various mixtures, organic solvents have also been regarded, unfortunately, to induce common neurotoxic effects. However, it is evident from experimental studies using specified exposure conditions that different organic solvents have very diverse neurotoxic effects and also that the toxic mechanism may differ between acute and chronic exposure. No specific method used to describe a neurotoxic effect or single toxic response can be used for the overall occupational risk assessment of all organic solvents. Each solvent has to be considered as having its own unique toxic effects.     

Ischemic monomelic neuropathy: An under-recognized complication of hemodialysis access

During the past 3 years six episodes of ischemic monomelic neuropathy (IMN) have been identified in five patients as a complication of upper extremity dialysis grafts. All patients had long-standing insulin-dependent diabetes, peripheral neuropathy, and brachial artery graft origins, whereas 60% had peripheral vascular disease. Five episodes occurred immediately after graft placement, whereas one was due to a graft-related thromboembolus. Diagnostic delay was common with initial findings attributed to anesthesia, positioning, or surgical trauma. Electrophysiologic studies showed underlying diabetic neuropathy with severe multifocal neuropathy distal to the grafts. Digital pressure indices were reduced but there was no critical ischemia. In three cases ischemia was completely corrected with improvement in one. One patient had proximal balloon angioplasty with no improvement and of the two untreated patients, one improved slightly. Ischemic monomelic neuropathy is a rare but disabling complication of dialysis access in diabetic uremic patients. Its occurrence is unpredictable and diagnostic delay is common. Correction of ischemia is indicated but usually does not improve the neuropathy. Prevention requires further research to more accurately characterize the patients at risk.Presented at the Twelfth Annual Meeting of the Southern California Vascular Surgical Society, Coronado, Calif., September 17–19, 1993.     

Role of immune complexes in thyroid diseases

Institute of Biochemistry, Academy of Sciences of the Uzbek SSR, Tashkent. (Presented by Academician of the Academy of Medical Sciences of the USSR Yu. A. Pankov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 113, No. 2, pp. 168–170, February, 1992.     

Flunarizine induces a transient loss of tyrosine hydroxylase immunoreactivity in nigrostriatal neurons

Neurotoxic effects of flunarizine (Fz), a selective calcium channel blocker, on the nigrostriatal dopamine system was investigated. Systemic injections of Fz to mice resulted in a transient loss of tyrosine hydroxylase (TH) immunoreactive nigrostriatal neurons without cell loss. TH immunoreactivity in these neurons was greatly reduced as rapidly as one day after drug administration (regardless of dosage used) and thereafter recovered in both dose- and time-dependent manners. Such a novel neurotoxic action of Fz may constitute a morphological substrate for reversible drug-induced parkinsonian signs described in recent clinical case reports.     

Spindle activity in the waking EEG in older adults.

Sleep spindles are an EEG sign of light sleep under physiological conditions. We reported the simultaneous occurrence of sleep spindles and alpha activity in the waking EEG in 12 patients with a mean age of 59.0 years. Most of the patients were diagnosed as cerebrovascular disorders such as cerebral arteriosclerosis, transient ischemic attack and vascular dementia. The mean alpha frequency in the presence of WSA significantly decreased by 1.5 Hz. The frequency and spatial distribution of waking spindle activity were similar to those of sleep spindles. In our cases, at least the two factors of cerebrovascular involvement and older adults were considered to be primarily responsible for the intrusion of sleep spindles into wakefulness (presumably a state close to very light drowsiness) due possibly to the instability of sleep-waking cycle regulation.     

Surface anatomy scanning image by MRI in herpes simplex encephalitis]

We present surface anatomy scanning (SAS) image by weighted-summation technique using MRI images in herpes simplex encephalitis. Recently, SAS has been developed as a technique that visualizes brain surface structures. This patient was a 64-year-old male who suffered from aphasia and memory disturbance after herpes simplex encephalitis. He was transferred to our hospital for rehabilitation. Neuropsychological tests showed Wernicke's aphasia and memory impairment. SAS was performed for the purpose of analyzing these neuropsychological deficits, especially the Wernicke's aphasia. In SAS image, sulci were enhanced and gyri were easy to identify clearly. The affected structures disclosed low intensity areas in the entire left temporal lobe, including the superior temporal gyrus. It was clarified that the damage to the left superior temporal gyrus resulted in his Wernicke's aphasia. We think that SAS is very useful for cortical lesion analysis, not only in encephalitis but also in other disorders presenting higher brain dysfunctions.