颅内压低频分析

目的：临床和基础研究发现,颅内压存在波动,本工作通过动物实验模拟颅高压并研究颅内压的波动。实验方法：14条犬安置硬膜外球囊并注液制成颅高压模型,通过改变球囊内液体量来改变颅高压程度和颅内容积,由压力传感器持续记录相应压力。结果：对颅内压、腰区脑脊液压分别进行FFT分析,发现都存在一个约为0．2Hz的波动,该频率既不是心率(3Hz左右)也不是呼吸频率(0．4Hz),记为M波。分析表明：1)正常情况下,M波并不出现;2)实验开始阶段,不出现M波,当颅内压超过一定压力水平时,M波出现。随后的药物干预实验显示,采用迷走神经阻断药阿托品能明显抑制M波,而交感神经阻断药心得安效果不明显,初步说明M波与脑血管的某些调节机制有关。     

Management of intracranial metastases.

Of 223 patients with intracranial metastases, 161 underwent removal of a presumed solitary lesion and 29 were treated by burr-hole biopsy. Results of radical surgery were better than those of biopsy alone in terms of survival. Quality and duration of survival were poorer in patients who had infratentorial metastases removed than in those who underwent surgery for supratentorial metastases. In this second group only patients with breast cancer benefited from surgery, though a few women with bronchial carcinoma also did well. The interval removal of a primary tumour and development of intracranial symptoms did not influence outcome. Evidence of a previous primary tumour should not lead to the assumption that intracranial symptoms are caused by a metastasis.     

Pulsatile flow effects on the hemodynamics of intracranial aneurysms

High-resolution numerical simulations are carried out to systematically investigate the effect of the incoming flow waveform on the hemodynamics and wall shear stress patterns of an anatomic sidewall intracranial aneurysm model. Various wave forms are constructed by appropriately scaling a typical human waveform such that the waveform maximum and time-averaged Reynolds numbers, the Womersley number (α), and the pulsatility index (PI) are systematically varied within the human physiologic range. We show that the waveform PI is the key parameter that governs the vortex dynamics across the aneurysm neck and the flow patterns within the dome. At low PI, the flow in the dome is similar to a driven cavity flow and is characterized by a quasi-stationary shear layer that delineates the parent artery flow from the recirculating flow within the dome. At high PI, on the other hand, the flow is dominated by vortex ring formation, transport across the neck, and impingement and breakdown at the distal wall of the aneurysm dome. We further show that the spatial and temporal characteristics of the wall shear stress field on the aneurysm dome are strongly correlated with the vortex dynamics across the neck. We finally argue that the ratio between the characteristic time scale of transport by the mean flow across the neck and the time scale of vortex ring formation can be used to predict for a given sidewall aneurysm model the critical value of the waveform PI for which the hemodynamics will transition from the cavity mode to the vortex ring mode.     

Primary intracranial epidermoid carcinoma

The cytologic findings in the cerebrospinal fluid in a case of primary intracranial epidermoid carcinoma are presented. The presence of a few squamous cells showing hyaline cytoplasm compatible with keratinization suggested the possible nature of the tomographically observed lesion. These tumors may arise in congenital epidermoid cysts at the base of the brain. Because of their location and meningeal spread, such tumors may cause severe symptoms and death despite a minute size, as illustrated by this case.     

Estradiol lowers intracranial self-stimulation thresholds and enhances cocaine facilitation of intracranial self-stimulation in rats

Women initiate cocaine use at a younger age and have more complications (e.g., higher rates of major or minor depression) related to cocaine use than men. It has been proposed that estrogens play an important role in these sex differences. The addictive potential of psychoactive drugs can be measured in rats via a rewarding intracranial self-stimulation (ICSS) procedure. The rate-independent method of ICSS allows researchers to assess the “pure” rewarding effect of cocaine without influence of nonspecific motor reactions. The present study aimed to estimate effects of estradiol and a combination of estradiol and cocaine on ICSS in ovariectomized female rats. 17-β-estradiol (5 μg/animal/day, 2 days) produced a long-lasting gradual lowering of the thresholds for ICSS. The ability of estradiol to decrease thresholds for ICSS has never been shown previously. Combination of 17-β-estradiol and cocaine (5.0 mg/kg, 5 days) produced a greater effect on ICSS thresholds than the effect of either compound alone. No tolerance or sensitization to cocaine developed during the study. Present findings suggest estradiol increases sensitivity of the brain reward system in rats, which may have an important implication in understanding sex differences in cocaine effects.