The authors' results show the possibility of occurrence of a TCR during manipulation of the central part of the trigeminal nerve when performing surgery in the CPA.
The ischemic penumbra has been documented in the laboratory animal as severely hypoperfused, nonfunctional, but still viable brain tissue surrounding the irreversibly damaged ischemic core. Saving the penumbra is the main target of acute stroke therapy, and is the theoretical basis behind the reperfusion concept. In experimental focal ischemia, early reperfusion has been reported to both prevent infarct growth and aggravate edema formation and hemorrhage, depending on the severity and duration of prior ischemia and the efficiency of reperfusion, whereas neuronal damage with or without enlarged infarction also may result from reperfusion (so-called reperfusion injury). Activated neutrophils contribute to vascular reperfusion damage, yet posthypoxic cellular injury occurs in the absence of inflammatory species. Protein synthesis inhibition occurs in neurons during reperfusion after ischemia, underlying the role that these pathways play in prosurvival and proapoptotic processes that may be differentially expressed in vulnerable and resistant regions of the reperfused brain tissue. Ischemia-induced decreases in the mitochondrial capacity for respiratory activity probably contribute to the ongoing impairment of energy metabolism during reperfusion and possibly also the magnitude of changes seen during ischemia. From these experimental data, the concept of single-drug intervention cannot be effective. Further experimental research is needed, especially of the study of biochemical markers of the injury process to establish the role of several drugs.
Cerebral venous occlusion represents an often underdiagnosed cause for acute or slowly progressive neurological deterioration. The underlying pathophysiological basis is not well understood, but is different from those of arterial occlusion reflecting therefore different anatomical and physiological features of the cerebral venous system. Extensive collateral circulation within the cerebral venous system allows for a significant degree of compensation in the early stages of venous occlusion. Elevated cerebral venous pressure due to cerebral venous occlusion can result in a spectrum of phenomena including a dilated venous and capillary bed, development of interstitial edema, increased cerebrospinal fluid production, decreased cerebrospinal fluid absorption and rupture of venous structures (hematoma). All of these pathophysiological changes may explain the clinical observation that cerebral venous occlusion, if promptly diagnosed and adequately managed, contains reversible alterations and need not always lead to venous infarction. The present review outlines this different pathophysiological behavior of venous compared to arterial occlusion in the cerebral vasculature; special reference is given to the effect of these changes on the therapeutic impact.
The origin of postoperative headaches after retrosigmoid vestibular schwannoma resections is not yet fully understood. Different factors may play a role in preventing or reducing headache: dural adhesions to nuchal muscles or to subcutaneous tissues and dural tension in the case of direct dural closure may explain postoperative headache from dural tension. Intradural drilling and the use of fibrin glue may be the source of aseptic meningitis as the etiology of persistent postoperative headache. Prevention of postoperative headache may include the replacement of bone flap at the end of surgery, duraplastic instead of direct dural closure, and prevention of the use of fibrin glue or extensive drilling of the posterior aspect of internal auditory canal.
The trigeminocardiac reflex (TCR) is defined as the sudden onset of parasympathetic dysrhythmia, sympathetic hypotension, apnea, or gastric hypermotility during stimulation of any of the sensory branches of the trigeminal nerve. Clinically, the TCR has been reported in all the surgical procedures in which a structure innervated by the trigeminal nerve is involved. Although, there is an abundant literature with reports of incidences and risk factors of the TCR; the physiological significance and function of this brainstem reflex has not yet been fully elucidated. In addition, there are complexities within the TCR that requires examination and clarification. There is also a growing need to discuss its cellular mechanism and functional consequences. Therefore, the current review provides an updated examination of the TCR with a particular focus on the mechanisms and diverse nature of the TCR.
Intraspinal meningiomas are slow growing benign tumors that produce indolent neurological deficits, which are often reversible following operation. It is unclear, if there is a correlation between postoperative neurological restoration and histopathological parameters. The aim of the present work was to seek for existence of such parameters. Retrospectively, we reviewed the charts of 33 patients with spinal meningiomas who were operated on from January 1980 through December 1995. Histological classification was performed according to WHO criteria. Laminoplasty or hemilaminoplasty was performed in 29 patients (88%) and suboccipital craniotomy with cervical laminoplasty in 4 patients (12%). Mean age of the 30 women (91%) and the 3 men (9%) was 63+/-20 years (range 22-88). Spinal meningiomas were of high-cervical location in 9 (27%) and of low-cervico-thoracic location in 24 (73%) patients. Tumor position was laterally in 19 (58%), posteriorly in 8 (24%) and anteriorly in 6 (18%) patients. Histological classification was psammomatous in 22 (66%), fibroblastic in 7 (22%) and meningothelial in 4 (11%) patients. Following tumor resection, neurological deficits resolved in 26 of 33 patients (79%) and worsened in 7 of 33 patients (21%) all of the latter had meningiomas of the psammomatous type. Resection of psammomatous meningiomas of the spine is associated with a less favorable neurological outcome postoperatively than resection of spinal meningiomas of other pathological subtypes. Posterior or lateral tumor position in the spinal canal, location below C4, age less than 60 years, and duration of preoperative symptoms seem to be correlated with a good outcome.
The trigemino-cardiac reflex (TCR) is clinically defined as the sudden onset of parasympathetic activity, sympathetic hypotension, apnea, or gastric hypermotility during central or peripheral stimulation of any of the sensory branches of the trigeminal nerve. Clinically, the TCR has been reported to occur during craniofacial surgery, manipulation of the trigeminal nerve/ganglion and during surgery for lesion in the cerebellopontine angle, cavernous sinus, and the pituitary fossa. Apart from the few clinical reports, the physiologic function of this brainstem reflex has not yet been fully explored. The manifestation of the TCR can vary from bradycardia and hypotension to asystole. From the experimental findings, the TCR represents an expression of a central reflex leading to rapid cerebrovascular vasodilatation generated from excitation of oxygen-sensitive neurons in the rostral ventro-lateral medulla oblongata. By this physiologic response, the systemic and cerebral circulations may be adjusted in a way that augments cerebral perfusion. This review summarizes the current state of knowledge about TCR.
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