Removal Of Posterior Fossa Tumors Research Articles

Effect of endoscopic third ventriculostomy on the prevention of hydrocephalus and the need for shunting in patients undergoing surgery for posterior fossa masses, a comparative study

BackgroundDue to the compressive effect of the brain masses, hydrocephalus treatment is mainly achieved by shunting and discharge of fluid. However, some reports have shown the potential adverse effects of this method and its potential contraindications that result in focusing on preventive approaches like endoscopic third ventriculostomy (ETV). Hence, in the present study, the authors undertook a study to examine the hypothesis that preoperative ETV could reduce the likelihood of hydrocephalus and the need for shunting in patients undergoing surgery for posterior fossa tumors. MethodsIn the current cross-sectional study, 40 consecutive patients were scheduled for surgery to remove posterior fossa masses using ETV preoperatively (n = 23) or were considered as the controls with no preoperative ETV (n = 17). Afterward, these patients were followed up for 2 months after surgery regarding hydrocephalus and the need for shunt insertion. The postoperative change in the ventricular-cranial ratio (VCR) was also compared in 2 groups. ResultsOf 23 patients in the ETV group, none required postoperative shunting due to the lack of evidence supporting hydrocephalus; however, 7 patients were found to require shunting in the non-ETV group. Notably, the value of VCR significantly reduced in both groups with no significant difference. ConclusionETV protocol before the surgical removal of posterior fossa tumors can effectively reduce the rate of postoperative hydrocephalus, decreasing the need for postoperative shunting.

Cerebro-Cerebellar Networks in Migraine Symptoms and Headache.

The cerebellum is associated with the biology of migraine in a variety of ways. Clinically, symptoms such as fatigue, motor weakness, vertigo, dizziness, difficulty concentrating and finding words, nausea, and visual disturbances are common in different types of migraine. The neural basis of these symptoms is complex, not completely known, and likely involve activation of both specific and shared circuits throughout the brain. Posterior circulation stroke, or neurosurgical removal of posterior fossa tumors, as well as anatomical tract tracing in animals, provided the first insights to theorize about cerebellar functions. Nowadays, with the addition of functional imaging, much progress has been done on cerebellar structure and function in health and disease, and, as a consequence, the theories refined. Accordingly, the cerebellum may be useful but not necessary for the execution of motor, sensory or cognitive tasks, but, rather, would participate as an efficiency facilitator of neurologic functions by improving speed and skill in performance of tasks produced by the cerebral area to which it is reciprocally connected. At the subcortical level, critical regions in these processes are the basal ganglia and thalamic nuclei. Altogether, a modulatory role of the cerebellum over multiple brain regions appears compelling, mainly by considering the complexity of its reciprocal connections to common neural networks involved in motor, vestibular, cognitive, affective, sensory, and autonomic processing—all functions affected at different phases and degrees across the migraine spectrum. Despite the many associations between cerebellum and migraine, it is not known whether this structure contributes to migraine initiation, symptoms generation or headache. Specific cerebellar dysfunction via genetically driven excitatory/inhibitory imbalances, oligemia and/or increased risk to white matter lesions has been proposed as a critical contributor to migraine pathogenesis. Therefore, given that neural projections and functions of many brainstem, midbrain and forebrain areas are shared between the cerebellum and migraine trigeminovascular pathways, this review will provide a synopsis on cerebellar structure and function, its role in trigeminal pain, and an updated overview of relevant clinical and preclinical literature on the potential role of cerebellar networks in migraine pathophysiology.

Making the “inoperable” tumors “operable”: Harvey Cushing's contributions to the surgery of posterior fossa tumors

Harvey Cushing played a pivotal role in establishing neurosurgery as a distinct surgical discipline. One of his most important contributions was defining the surgical removal of posterior fossa tumors. Compulsive preoperative evaluation followed by meticulous surgical technique as well as incorporation of maneuvers such as ventricular puncture and electrocautery further advanced resection of tumors in this region. Herein, the authors review Cushing's contributions to posterior fossa surgery.

Fronto-cerebellar fiber tractography in pediatric patients following posterior fossa tumor surgery

Fronto-cerebellar association fibers (FCF) are involved in neurocognitive regulatory circuitry. This may also be relevant for cerebellar mutism syndrome (CMS) as a complication following posterior fossa tumor removal in children. In the present study, we investigated FCF by diffusion tensor imaging in affected children and controls. Diffusion-weighted MR imaging at 3 T (GE) allowed tractography of FCF using a fiber tracking algorithm software (Brainlab 2.6) in 29 patients after posterior fossa tumor removal and in 10 healthy peers. Fiber tract volumes were assessed and fiber signals were evaluated in a semiquantitative manner along the anatomical course. Volumes of FCF revealed significant diminished values in pediatric patients with symptoms of CMS (19.3 ± 11.7 cm(3)) when compared with patients without symptoms of CMS (26.9 ± 11.9 cm(3)) and with healthy peers (36.5 ± 13.82 cm(3)). In medulloblastoma patients, the volume of FCF was also significantly reduced in patients with symptoms of CMS despite having the same antitumor therapy. In semiquantitative analysis of the fiber tract signals, differences were observed in the superior cerebellar peduncles and midline cerebellar structures in patients with symptoms of CMS. Using DTI, which allows the visualization of fronto-cerebellar fiber tracts, lower FCF tract volumes and diminished fiber signal intensities at the level of the superior cerebellar peduncles and in midline cerebellar structures were identified in patients with postoperative symptoms of CMS. Our study refers to the role of a neural circuitry between frontal lobes and the cerebellum being involved in neurocognitive impairment after posterior fossa tumor treatment in children.

Persistent trigeminal neuralgia after removal of contralateral posterior cranial fossa tumor. report of two cases.

BACKGROUND Contralateral trigeminal neuralgia as a false localizing sign in patients with posterior cranial fossa tumors is rare. Persistent contralateral trigeminal neuralgia after removal of the posterior fossa expanding lesion with microsurgical exploration of the affected trigeminal nerve root has been described in only a few reports. Displacement of the brainstem and the trigeminal nerve root, arachnoid adhesions, and vascular compression of the nerve root entry zone have been reported as causes of persistent contralateral trigeminal neuralgia. METHODS One patient developed transformation of the contralateral constant burning facial pain into trigeminal neuralgia after removal of a posterior fossa meningioma. A typical right-sided tic douloureux in our second patient did not disappear after removal of a left acoustic neurinoma. CT scan revealed brainstem displacement to the side of trigeminal neuralgia. Microsurgical exploration in both cases demonstrated the squeezed and distorted trigeminal nerve root and displaced brain stem with no vascular involvement. Both patients underwent partial trigeminal rhizotomy for pain control. RESULTS Complete disappearance of the trigeminal neuralgia was evident in both cases with postoperative facial sensory loss. The postoperative course in the first case was uneventful; the second patient died from purulent meningoencephalitis. CONCLUSION Persistent contralateral trigeminal neuralgia after removal of a posterior fossa tumor is caused by distortion of the fifth nerve root by the displaced brainstem. Partial trigeminal rhizotomy can be performed for alleviation of facial neuralgic pain in cases without neurovascular compression.

A modified lateral decubitus position for surgical approaches to midline posterior fossa lesions: technical note.

Although a number of operative positions have been described for approaching midline posterior fossa tumors, all have potential disadvantages and complications. We describe a modified lateral decubitus position for the removal of posterior fossa tumors. The position allows blood and cerebrospinal fluid to drain from the operative wound and provides a straight-on view of the posterior fossa contents. It also allows the surgeon to sit comfortably during tumor removal, thereby reducing operator fatigue. We have found this to be a reliable and valuable approach for posterior fossa pathology.

Intraoperative electrophysiological monitoring of the facial nerve: Is it standard of practice?

(Editorial Comment: This report details the results of a poll of facial nerve surgeons and clearly shows that routine facial nerve monitoring is not currently a standard of practice in the United States.) Iatrogenic injury to the facial (VII] nerve is the most feared complication of routine otologic surgery. Therefore, it would seem logical to recommend the use of any adjunctive technique that might reduce the incidence of intraoperative facial nerve injury. Intraoperative electrophysiological monitoring of the facial nerve has been used clinically for more than 10 years and is widely accepted as a useful adjunctive modality for many neurotologic procedures, especially those that involve removal of posterior fossa tumors. There have now been a number of articles that report compelling statistical data that show improved postoperative facial nerve function when the facial nerve is monitored during such procedures.lm3 Some surgeons are also using the intraoperative electrophysiological facial nerve monitoring in more routine otologic procedures such as tympanomastoid surgery, stapedectomy, and tympanoplasty. In both written and oral presentations, a few of these surgeons have strongly advocated the use of intraoperative monitoring as a routine adjunct to such otologic procedures.4*5 These recommendations are made on pragmatic grounds or based on anecdotal experiences. The effectiveness of monitoring in such cases has not been supported on the basis of objective statistical data. We do not use intraoperative electrophysiological monitoring for most of our routine otologic procedures. We do not believe it would be helpful and, in fact, suspect that it could be counterproductive. We are concerned that routine electrophysiological facial nerve monitoring may become regarded as the “standard of care” before confirming its efficacy with objective studies and without the consent of the otoiogic community at large. In an attempt to determine the sense of the otologic community with respect to this issue, we surveyed the membership of the American Neurotology Society and the American Otologic Society. It was our belief that most of the members of these two organizations dedicated much of their clinical time to the management of otologic problems and the performance of otologic operations. Moreover, we suspect that members of these two societies represent a fair cross-section of surgeons whose primary interest is otologic surgery.

Impairment of neuropsychological functions in children with medulloblastomas and astrocytomas in the posterior fossa.

Neuropsychological impairment after removal of posterior fossa tumors is a recurrent issue in child neuropsychology and neurosurgery. The aim of this study was to assess verbal and performance intelligence, as well as immediate and sustained attention, in children with medulloblastoma or astrocytoma operated on for total removal of the lesion. Surgical treatment of medulloblastoma was always followed by chemoradiotherapy. Siblings of both tumor groups (without a history of neurological disease, even suspected) were examined as controls. The results were as follows: the cognitive performances were significantly poorer than the controls in both groups; the children with medulloblastoma scored below normal. Attention deficits were present in both groups as well when the usual clinical tests were used. When assessed by means of computerized methodology, the same function was normal. Considering that both groups of children underwent the same surgical treatment and all had hydrocephalus, the severe intellectual impairment reported only in patients with medulloblastoma can be ascribed to chemoradiotherapy. In contrast, the attention deficits present in both groups could be ascribed to the proximity of lesions to the ascending activating system. Malfunctioning of the activating system seems to be bypassed by the computerized administration of stimuli, which supplies motivation and kindles attention.

Cervical spinal deformity following craniotomy and upper cervical laminectomy for posterior fossa tumors in children

Spinal deformity is not usually regarded as a potential complication of posterior fossa tumor resection. After cervical subluxation had been recognized in 2 children following removal of posterior fossa tumors, a review was carried out to determine the incidence of this complication. Of the 72 children who had undergone resection of a posterior fossa tumor, 4 patients, including the original 2, developed a cervical spinal deformity. Factors that predisposed to this complication included laminectomy of C2 or lower, local wound complications and possibly post-operative neck weakness. It is important to be aware that cervical subluxation can occur after resection of posterior fossa tumors, when laminectomy extending below C1 has been performed. Patients at risk should be followed closely.

Postsurgical Disappearance of Dementia without Increased Cerebral Blood Flow in Hydrocephalic Patients

Cerebral blood flow (CBF) was measured in four elderly hydrocephalic patients with dementia with the use of the 133-Xe inhalation method. The patients had no signs and symptoms of increased intracranial pressure. They all had a triad of normal pressure hydrocephalus (NPH) except one patient, who lacked incontinence. Dementia, evaluated with the dementia rating scale by Hasegawa, decreased markedly after shunting procedures in two patients and after removal of posterior fossa tumors in the other two patients. The average hemispheric CBF was subnormal in three patients, and within normal range in the fourth patient before operation. It did not increase when dementia disappeared within 7 to 21 days postoperatively. The mean CBF was 41.4 ml/100 g/min before operation, and 40.8 ml/100 g/min after operation when dementia disappeared. The cerebral circulation time (CCT) was measured by the dynamic computed tomography (CT) in three of them. The mean CCT was prolonged before operation, 13.0 sec, and returned to normal range, 7.5 sec, when dementia abated after operation. This reduction and normalization of CCT reflect an improvement in the microcirculation within the brain. The results of this study demonstrate that disappearance of dementia following surgical intervention in hydrocephalic patients, possibly including those with NPH, is not always accompanied or preceded by an increase in CBF as measured by the conventional method. However, the postoperative disappearance of dementia is accompanied by an improvement in microcirculation which can be measured by the dynamic CT.