Critical reviews in neurosurgery : CR最新文献

Appropriate treatment of raised intracranial pressure (ICP) after traumatic brain injury (TBI) remains a controversial topic in neurotraumatology. Several techniques are employed clinically, which include vasopressors, osmotically active substances, hyperventilation, and decompressive surgery. This article reviews six recent papers that have examined alternative methods of treating elevated ICP. The first two papers consider a new and controversial alternative to cerebral perfusion pressure (CPP) management, which involves mild hypotension coupled with pre-capillary vasoconstriction using dihydroergotamine. The authors claim success with this treatment, and although the patient numbers are small, there is no evidence that they fare any less well than patients treated with conventional techniques. The third and fourth papers consider hypertonic saline (HTS) as a possible osmotic treatment for raised ICP. The third examines HTS given as a 23.4% bolus and found beneficial effects. The fourth examines HTS as a 1.6% constant infusion for fluid replacement and found that patients fared less well. The reason for this difference between the results for the two administration methods is unknown, although it may relate to the triggering of body homeostatic mechanisms in the case of constant infusion. The fifth paper compares glycerol and mannitol as osmotic ICP agents and found no significant differences between them. The final study reports for the first time a series of patients treated for refractory elevations in ICP with bifrontal craniectomy. They report good results, and suggest that this therapy should be formalized as a treatment option for severely elevated ICP. The pathophysiological mechanisms underlying the generation of a raised ICP belie the use of one therapy to treat all cases. Analysis of these studies demonstrates how problematic heterogeneity in the injury population can be for the assessment of possible treatments. It is clear, therefore, that effective analysis of treatments for raised ICP requires appropriate subdivision of the injured population into common pathophysiological processes and, furthermore, that the future of clinical TBI management may well require a similar stratification in order to tailor treatments for the individual patient.

The endovascular treatment of intracranial aneurysms is gaining a definite place in neurosurgery. This is particularly true for treatment using the Guglielmi detachable coil (GDC). "Endovascular treatment or direct surgery?" is a common discussion nowadays. The following papers raise some important issues with respect to this argument. This review also includes several papers that deal with posttraumatic pseudoaneurysms. One of the papers clearly suggests that endovascular treatment could also play an important role in treating pseudoaneurysms.

Numerous natural and synthetic substitutes have been proposed for dural grafting. Autografts, allografts, xenografts and nonabsorbable or absorbable polymer sheets have been used in experimental models and clinical practice. This article reviews the literature regarding the features, advantages, and related complications of different dural substitutes.

Owing to its low rate of side effects and its high efficacy, interstitial irradiation with low-activity seeds should be the first therapeutic step in small (maximal diameter 40 mm), well-circumscribed, low-grade gliomas affecting the brain stem, other midline structures, or eloquent cerebral areas. In anaplastic gliomas, a therapeutic schedule using low-activity seeds and combining interstitial irradiation with radiotherapy (reduced boost dose of 15-30 Gy) seems to be more effective than interstitial irradiation alone. Compared with interstitial irradiation with high-activity seeds, this combined irradiation schedule caused no space-occupying radiation necrosis. Thus, it can be recommended as up-front treatment in patients with small (maximal diameter <40 mm) inoperable anaplastic gliomas. The use of high-activity I-125 seeds and interstitial irradiation at comparably high dose rates, integrating a small penumbra of normal brain tissue into the treatment volume, improved survival significantly in patients with primary highly malignant gliomas. In patients with recurrent tumors, the same treatment schedule did not substantially prolong survival compared with results obtained after resection plus radiotherapy. Owing to the high frequency of space-occupying radiation necrosis (40-60%), this schedule is only applicable in surgically accessible tumors. The application of low-activity I-125 seeds (in primary glioblastomas in combination with radiotherapy, in recurrent tumors without radiotherapy) yielded a median survival comparable with conventionally treated patients. There was no need for reoperation because of radiation necrosis. Thus, this treatment schedule is useful in both operable and surgically inaccessible glioblastomas.

With the dramatic technical advances in neuroimaging, it has become possible to diagnose central nervous system (CNS) anomalies in the fetus in utero with more precise morphological analysis. A new technique, high-resolution magnetic resonance (MR) imaging using heavily T2-weighted fast spin echo sequences, has been reported to solve motion artifact of the fetus. However, it has also been recognized that the morphological fetal CNS findings detected in early development are not always the final features: occasionally they may not be determined in diagnosis and may change developmentally or chronologically during the fetal life in utero. Certain factors of the fetal chronology of CNS anomalies can cause irreversible changes during fetal life. These include: (1) significant delay in the neuronal maturation process in fetal hydrocephalus developed in clinicoembryological stage II in the Perspective Classification of Congenital Hydrocephalus (PCCH), (2) secondary neural injury in the intactly developing spinal cord above the neural placode in fetus with spina bifida aperta (myeloschisis), (3) histological "evolution" of tumors or dysgenetic CNS, and (4) deformity of the normally developed intracranial or intraspinal CNS structures. Considering the current status of fetal surgery in general and technical advances promising improved outcomes, fetal neurosurgery can also be applied in the above-mentioned progressive pathology or pathophysiology in the fetal CNS. However, since the failure of the first trial of fetal neurosurgery in the 1980s, the prerequisites have still not been clarified. In order to use advanced neurosurgery techniques in the management of fetal CNS anomalies, these prerequisites have to be established.

Subarachnoid haemorrhage (SAH) is often associated with negative cerebral angiography. Following the exclusion of other causes, a patient may be suspected of harbouring an occult intracranial aneurysm, with risk of recurrent bleeding and death. These patients are often identified on the basis of clinical presentation and computed tomography (CT) findings, and require expeditious further investigation if morbidity and mortality are to be minimized. Currently available options include repeated cerebral angiography, surgical exploration, and the newer technologies of computed tomography angiography (CTA) and magnetic resonance angiography (MRA). We review these options, based on current literature, with particular emphasis on the expanding roles of CTA and MRA. A multimodality management protocol is proposed, with decisions based on clinical urgency, patient progress and the natural history of aneurysmal SAH, particularly vasospasm and aneurysm thrombosis.

Meningiomas are rare intracranial neoplasms in the pediatric population. Most of the reports concerning these tumors have stressed some distinguishing features comparable with the adult counterpart. Besides the lower incidence, the nearly equal sex distribution, the relatively common infratentorial location and the frequent development within the ventricular system have been emphasized. A poor prognosis of pediatric meningiomas has also been claimed by authors who have suggested that this could be owing to a possibly more aggressive behavior, accounting for the huge size that these tumors have usually reached at diagnosis, the difficult surgical excision, and the higher recurrence rate. The analysis of recent series challenges the concept that pediatric meningiomas do actually bear a worse prognosis than similar tumors occurring in older patients. Improved surgical techniques have in fact resulted in higher percentages of complete tumor removal. Better histological delineation has allowed the identification of highly aggressive meningeal neoplasms, which in the past were not differentiated properly, thus contributing to the apparent higher incidence of recurrent tumors in the pediatric population. When the studies are limited to the "classical" form of meningioma, it becomes apparent that pediatric meningiomas do not behave more aggressively than meningiomas in adult patients.

The role of irradiation in the management of pituitary adenomas is not well defined. Nevertheless, patients with residual or recurrent tumours have been treated with conventional external-beam radiotherapy and more recently with high-precision stereotactic techniques of stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). We review some of the recently published articles on the efficacy and toxicity of SRS in the light of the current literature describing the results of conventional radiotherapy. While the general perception is that single-fraction SRS is more effective and less toxic than fractionated radiotherapy and in hormone-secreting tumours may produce a faster decline in elevated hormone levels, the available evidence suggests higher toxicity than seen with fractionated treatment without the reassurance of long-term tumour control. There is also no convincing evidence for more rapid reduction of elevated hormones. For the treatment of larger non-spherical pituitary adenomas, it may be appropriate to explore a potentially safer high-precision technique of fractionated conformal stereotactic radiotherapy (SCRT). In conclusion, there is currently little justification for the routine use of single-fraction SRS for the treatment of the majority of patients with benign pituitary adenomas.