Critical reviews in neurosurgery : CR最新文献

Long-term survivors of medulloblastoma do occur, even in high-risk groups. Infants and toddlers surviving past the age of 21 years can expect significant intellectual impairment if their radiation therapy was given at approximately 2 years of age. If radiation therapy is delayed or avoided, most of those who survive long term are in a regular school classroom. All of the latter had complete tumor resection. Sixty-two percent of children who received conventional radiation therapy (mean 24 Gy) developed primary hypothyroidism. Tumor markers and improved understanding of tumor biology may lead to more effective surveillance monitoring.

Cerebral arteriovenous malformations (AVMs) are thought to result from a failure of embryogenesis in the otherwise normal differentiation of primordial vascular channels into mature arteries, capillaries, and veins. Although these are essentially congenital vascular malformations, marked enlargement and/or recurrence of cerebral AVMs has been reported in the recent literature. Using MEDLINE (1966- 1998), we searched the recurrence of cerebral AVMs and analyzed all reported recurrent cases after total surgical extirpation and negative postoperative angiogram, and discussed the proposed mechanisms of the recurrence of cerebral AVMs. A thorough literature survey disclosed only 12 documented recurrent cases (9 were documented in English and 3 in Japanese), which shows the rarity of the recurrence of cerebral AVMs, although the actual rate of recurrence is not known because of the lack of routine long-term follow-up. The location of recurrent cerebral AVMs was the cerebral hemisphere, and initial presentation was hemorrhage in all cases. Recurrence occurred in patients under 20 years of age in 9 of 11 cases, which implies the propensity of recurrence of cerebral AVMs in immature brain vasculature. There are no definite proven mechanisms to explain why congenital anomalies such as cerebral AVMs recur after total extirpation, but recently two plausible mechanisms have been proposed. One is angiogenesis disregulated by vas-cular endothelial growth factor (VEGF) and the other is a new anatomical entity, 'hidden compart-ments'. Although VEGF is one of the main angiogenetic factors and its important role in fetal brain and pathological neovascularization has been reported, the synthesis of VEGF might be insufficient to explain the recurrence of cerebral AVMs because VEGF-positive staining is also found in nonrecurrent patients. Hidden compartments are angiographically unfilled compartments, in spite of an adequate examination, which may be located within, contiguous with, or relatively far from the angiographically demonstrated AVM. Although it might explain unsolved clinical phenomena such as regrowth, recurrence, and per- or postoperative unanticipated bleeding and brain swelling, the existence of hidden compartments should be proved by high-resolution radiological examinations or during operations. The presence of recurrent cerebral AVMs after complete extirpation by modern microsurgical techniques indicates that cerebral angiography in the early postoperative stage, the golden standard to assess the disappearance of cerebral AVMs, is not sufficient to eliminate the risk of hemorrhage, and careful long-term follow-up studies should be planned.

Proton magnetic resonance spectroscopy (MRS) permits in vivo determination of biochemical parameters within brain tissue, utilizing the same magnetic resonance (MR) scanner and head coil that are utilized for conventional MR imaging. This technology has been evolving and improving over the past decade, with most of the current published work based on the measurement of rather large single voxels, utilizing variable echo times, aimed at characterizing changes in brain tumors, demyelinating diseases, abscesses, and metabolic diseases. Future work will utilize multiple-voxel techniques so that volumes of tissue can be examined with smaller voxels in reasonable acquisition times, providing a greater understanding of the metabolite composition of the brain, especially as more and more metabolites are identified within the spectra.

This article critically reviews the current state of knowledge relating to outcome following decompressive surgery for lumbar spinal stenosis. Non-biased reviews of outcome are rare, follow-up times are not uniform and generally short, surgical techniques are not standardized. Rationale regarding the efficacy of concomitant spinal fusion is unconvincing. A procedure that is becoming ever more common in the neurosurgical armamentarium appears to be poorly described with respect to outcomes.

Cervical neurinomas ex-tending through the intervertebral foramen are uncommon. They raise difficult problems of surgical management. The few papers dealing with surgical technique for removal of these tumors are reviewed. The surgical approach has to be chosen from posterior, anterior, and anterolateral routes. Analysis is essentially devoted to the radicality of tumor resection, nerve root preservation, relation to the vertebral artery, and compromise of spinal stability.

Latex allergy has become a major problem in children with spina bifida, who need to undergo many major aggressive diagnostic and therapeutic procedures. Latex allergy is increasing in medical and surgical practice. Although early reports of latex allergy date from 1927, only over the last decade there has been more attention paid to latex allergy. This is due to an increasing number of reported cases of mild to fatal adverse reactions to latex. Risk groups have been identified; among these are patients undergoing multiple surgeries such as those with spina bifida. In this critical review, we aim to emphasize some aspects of the current management of surgical patients with latex allergy.

With the resurgence of interest in neurosurgical intervention for the treatment of drug-resistant Parkinson's disease, posteroventral pallidotomy (internal globus pallidus) has become a procedure widely applied by neurosurgeons. In chronic deep brain stimulation, the stimulation target is the same area as the above lesion-making point: the ventralis intermedius thalamic nucleus, subthalamic nucleus, and internal globus pallidus, since deep brain stimulation does not induce brain damage, and it is possible to control the stimulation (frequency and strength). There is also no recurrence. This procedure has the reversibility, selectivity, and adjustability that is ideal for functional neurosurgery. Such chronic stimulation therapy has thus now become an alternative to lesion-making stereotactic surgery. However, stimulation therapy directed at a particular target has more specific effects on particular symptoms of Parkinson's disease, so that an effective stimulation target needs to be selected depending on the nature of the syndrome to be improved. This article presents a review of the most recent reports on how to perform safer and more effective pallidotomy, and of recent basic and clinical reports concerning pallidal stimulation. Some answers to the question of whether or not stimulation therapy is an alternative to lesion-making surgery at the internal globus pallidus to improve parkinsonian syndrome and levodopa-induced dyskinesias are discussed.

Two management modal-ities appear to be important in treating skull base chordomas: surgery and radiation therapy. Radical resection of lesions of the distal sacrum (S3-S5) and coccyx may be curative, as total removal is often achieved. In contrast, complete resection of chordomas of the base of the skull is rarely successful because of the inability to achieve a true complete surgical resection. On the other hand, treatment of skull base chordomas by radiation therapy alone is often difficult owing to the large size of the lesion and the dose limitation imposed by the sensitivity of the adjacent structures. Local relapse is the predominant type of treatment failure of skull base chordoma. Skull base surgery and radiation therapy have significantly improved over the last 20 years. The following papers review the most significant recent analyses of therapeutic options in treating skull base chordomas. It seems that the combination of aggressive surgery followed by combined proton-photon radiation therapy offers the best chance of long-term local control to patients harboring cranial chordomas.

Female gender and cigarette smoking appear to be risk factors for the development of multiple intracranial aneurysms. An acquired nature is likely in this form. The mechanism of aneurysm formation in patients with sickle cell anemia is apparently different. These patients also present multiple aneurysms that show propensity for vertebrobasilar territory and appear at a younger age. Familial cerebral aneurysms are diagnosed once heritable connective tissue disorders have been excluded. The age of patients tends to be lower and the size of aneurysm to be smaller at the time of rupture in the familial form. These aneurysms are less frequently found in the anterior communicating artery than the sporadic aneurysms. A high incidence of asymptomatic familial aneurysms was detected in people with family histories of intracranial aneurysms studied by means of magnetic resonance angiography. Furthermore, familial aneurysms are more likely to rupture in families having members with aneurysmal subarachnoid hemorrhage (SAH) than in those without. The results of an interesting study using color "power" transcranial Doppler ultrasound in patients with aneurysmal SAH suggest that as the intracranial pressure diminished, the size of the aneurysm increased, and there was relatively little change between maximum and minimum dimensions during the cardiac cycle, i.e., the pulsatility is reduced. The use of postoperative angiography after clipping is a matter of debate. The indication more widely accepted is in large aneurysms with a wide neck, in which incomplete clipping can be suspected. Taking into account the current low risk of angiography in centers of excellence, its routine use may be recommended. Aneurysm remnants, vessel occlusion, vasospasm, and newly identified aneurysms are the main findings that were reported.