Pang D, Altschuler E
Division of Pediatric Neurosurgery, University of California, Davis, Sacramento.
Neurosurgery. 1994 Oct;35(4):643-55; discussion 655-6. doi: 10.1227/00006123-199410000-00010.
Most shunt-dependent hydrocephalic patients present with predictable symptoms of headache and mental status changes when their cerebrospinal fluid shunts malfunction. Their intracranial pressure (ICP) is usually high, and they usually respond to routine shunt revision. This report describes 12 shunted patients who were admitted with the full-blown hydrocephalic syndrome but with low to low-normal ICP. All 12 patients had been maintained previously on medium-pressure shunts. Their symptoms included headache, lethargy, obtundation, and cranial neuropathies. At peak symptoms, their ventricular sizes were large (ventricular/biparietal ratio of 0.35 to 0.45) in six and massive (ventricular/biparietal ratio > 0.45) in six and their ICPs ranged from 2.2 to 6.6 mm Hg, with a mean of 4.4 +/- 1.3 mm Hg (+/- standard deviation), i.e., below or well within the pressure range of their shunts. The pressure volume index of three patients at peak symptoms ranged from 39.2 to 48.5 ml, with a mean of 43.9 +/- 4.6 ml, which represents a 190% increase from the predicted normal value. Seven patients failed to improve with multiple shunt revisions, including the use of low-pressure valves. In 11 patients, symptoms and ventriculomegaly were not reversed except with prolonged external ventricular drainage at subzero pressures (mean external ventricular drainage nadir pressure of -5.7 +/- 3.6 mm Hg, for a mean period of 22.2 days). During external ventricular drainage treatment, symptoms correlated only with ventricular size and not with ICP. All 11 were subsequently treated successfully with a new medium- or low-pressure shunt. One patient was treated successfully with prolonged shunt pumping. We postulate that: 1) the development of this low-pressure hydrocephalic state is related to alteration of the viscoelastic modulus of the brain, secondary to expulsion of extracellular water from the brain parenchyma, and to structural changes in brain tissues due to prolonged overstretching; 2) certain patients are susceptible to developing low-pressure hydrocephalic state because of an innate low brain elasticity due to bioatrophic changes; 3) low-pressure hydrocephalic state symptoms are due not to pressure changes but to brain tissue distortion and cortical ischemia secondary to severe ventricular distortion and elevated radial compressive stresses within the brain; and 4) treatment must be directed toward allowing the entry of water into the brain parenchyma and the restoration of baseline brain viscoelasticity.
大多数依赖分流术的脑积水患者在其脑脊液分流装置发生故障时会出现可预测的头痛和精神状态改变症状。他们的颅内压（ICP）通常较高，且通常对常规的分流装置修复有反应。本报告描述了12例因典型脑积水综合征入院但ICP低至正常低限的分流患者。所有12例患者此前均使用中压分流装置维持治疗。他们的症状包括头痛、嗜睡、意识模糊和颅神经病变。在症状高峰期，6例患者的脑室大小较大（脑室/双顶骨径比为0.35至0.45），6例患者的脑室巨大（脑室/双顶骨径比>0.45），他们的ICP范围为2.2至mmHg，平均为4.4±1.3 mmHg（±标准差），即低于或处于其分流装置的压力范围内。3例患者在症状高峰期的压力容量指数范围为39.2至48.5 ml，平均为43.9±4.6 ml，这比预测的正常值增加了190%。7例患者经多次分流装置修复，包括使用低压阀门，病情仍未改善。11例患者的症状和脑室扩大除了在零下压力下进行长时间的外部脑室引流（平均外部脑室引流最低点压力为-5.7±3.6 mmHg，平均持续22.2天）外均未得到改善。在外部脑室引流治疗期间，症状仅与脑室大小相关，而与ICP无关。所有11例患者随后均通过新的中压或低压分流装置成功治疗。1例患者通过长时间的分流泵浦成功治疗。我们推测：1）这种低压脑积水状态的发展与脑实质细胞外水分排出继发的脑粘弹性模量改变以及长时间过度拉伸导致的脑组织结构变化有关；2）某些患者由于生物萎缩性改变导致先天性脑弹性低，易发生低压脑积水状态；3）低压脑积水状态的症状不是由于压力变化，而是由于严重的脑室变形和脑内径向压缩应力升高继发的脑组织扭曲和皮质缺血；4）治疗必须旨在使水分进入脑实质并恢复基线脑粘弹性。
