Cerebral oxygenation assessed by near-infrared spectroscopy in the sitting and prone positions during posterior fossa surgery: a prospective, randomized clinical study

Abstract Objectives: Sitting position (SP) or prone position (PP) are used for posterior fossa surgery. The SP induced reduction in cerebral blood flow and cerebral oxygen saturation (rSO2) has been shown in shoulder surgeries, but there is not enough data in intracranial tumor surgery. Studies showed that PP is safe in terms of cerebral oxygen saturation in patients undergoing spinal surgery. Our hypothesis is that the SP may improve cerebral oxygenation in the patients with intracranial pathologies due to reduction in intracranial pressure. Therefore, we compared the effects of the SP and PP on rSO2 in patients undergoing posterior fossa tumor surgery. Methods: Data were collected patients undergoing posterior fossa surgery, 20 patients in SP compared to 21 patients in PP. The rSO2 was assessed using INVOS monitor. Heart rate (HR), mean arterial pressure (MAP), EtCO2, BIS, and bilateral rSO2 were recorded preoperatively, and at 5, 8, and 11 minutes after the intubation and every 3 minutes after patient positioning until the initial surgical incision. Results: Cerebral oxygenation slowly reduced in both the sitting and prone position patients following the positioning (p < 0.002), without any difference between the groups. The HR and MAP were lower in the sitting SP after positioning compared to the PP. Conclusion: Neurosurgery in the SP and PP is associated with slight reduction in cerebral oxygenation. We speculate that if we rise the lower limit of MAP, we might have showed the beneficial effect of the SP on rSO2.

Intellectual aspects of cognitive performance in children after treatment for medulloblastoma and astrocytoma

The present study investigated the relationship between posterior fossa tumors (astrocytoma and medulloblastoma) and their respective treatments and cognitive performance in Brazilian children by measuring Intelligence Quotient (IQ). Twenty children were enrolled in the study, of whom 13 were diagnosed with astrocytoma (average age at evaluation, 10.2 years; eight girls and five boys) and seven were diagnosed with medulloblastoma (average age at evaluation, 9.2 years; five girls and two boys). The first subgroup underwent exclusively tumor resection surgery, and the second subgroup underwent surgery, chemotherapy (Vincristine, Cisplatine, and Carmustine), and radiotherapy (total dose, 54 Gy). The inclusion criteria for the clinical group were normal social and emotional behavior before the diagnosis and motor and visual performance not excessively deteriorated after surgery. All participants were submitted to the Wechsler Intelligence Scale for Children - third version, and their scores were related to standard norms established for Brazilian children and compared with regard to the diagnosis subgroups and treatment modalities. Statistically significant differences were identified between the two diagnosis subgroups in Performance IQ and Processing Speed scores. The medulloblastoma subgroup presented poorer performance in all domains compared with the astrocytoma subgroup. Time interval between diagnosis and neuropsychological evaluation also had a significant effect on Processing Speed and Freedom from Distractibility in the medulloblastoma subgroup. These results provide empirical evidence of a possible significant effect of radiotherapy exposure on processing speed and global intellectual capacity

Hemifacial Spasm Caused by a Huge Tentorial Meningioma

A rare case of hemifacial spasm caused by an ipsilateral tentorial meningioma is described. Magnetic resonance imaging showed a huge tumor in the right cerebellar hemisphere, distant to the cerebello-pontine cistern. The facial-vestibulocochlear nerve complex was stretched by the shift of the brainstem and the right cerebello-pontine cistern was effaced. After removing the tumor, the hemifacial spasm resolved completely. We review our case with the pertinent literature regarding the etiological mechanism.

Congenital Cerebellar Mixed Germ Cell Tumor Presenting with Hemorrhage in a Newborn

We report here on a neonate with congenital cerebellar mixed germ cell tumor, and this initially presented as cerebellar hemorrhage. Postnatal cranial ultrasonography revealed an echogenic cerebellar mass that exhibited the signal characteristics of hemorrhage rather than tumor on MR images. The short-term follow-up images also suggested a resolving cerebellar hemorrhage. One month later, the neonate developed vomiting. A second set of MR images demonstrated an enlarged mass that exhibited changed signal intensity at the same site, which suggested a neoplasm. Histological examination after the surgical resection revealed a mixed germ cell tumor.

Syringomyelia Associated with Posterior Fossa Tumor: Case Report

The authors describe three patients of syringomyelia associated with posterior fossa tumor. The lesions were diagnosed by magnetic resonance imaging. Total removal of tumor without decompression of foramen magnum was done and regression of syringomyelia and improvement of symptoms were demonstrated. It is suggested that the blockage of cerebrospinal fluid flow at the foramen magnum by tonsilar herniation may play an important role in syrinx formation.

Therapeutic Results of Posterior Fossa Tumors with Hydrocephalus

OBJECTIVE: This study is designed to identify the clinical characteristics and the optimal treatment modality of hydrocephalus in posterior fossa tumors. METHODS: The authors reviewed 154 infratentorial tumor patients. Age, sex, clinical symptoms, types of treatment, and surgical results of posterior fossa tumor patients with hydrocephalus were analyzed, retros-pectively. Factors which might predict the need for external ventricular drainage(EVD) or ventriculo-peritoneal shunt were analyzed statistically. RESULTS: Hydrocephalus was noted in 86 cases(56%), and it was associated with medulloblastoma in 16 cases(89%), hemangioblastoma in 12(63%) and brain stem glioma in three(33%). The surgical results of the posterior fossa tumors with hydrocephalus were poorer than those without hydrocephalus(p<0.05). A large tumor(p<0.05) and an incomplete removal(p<0.05) were factors predicting the need for EVD or shunt. Complications of intraoperative EVD or shunt developed in four cases. They were infection, he-morrhage at puncture site, and obstruction. Five patients in whom intraoperative EVD or shunt had not been performed developed a fatal hydrocephalic attack at immediate postoperative period, and the pos-toperative computed tomography scan revealed intraventricular hemorrhages in three cases cerebellar swellings in two cases. CONCLUSION: Intraoperative EVD or shunt is a safe, effective treatment modality especially in large size tumor and/or incomplete tumor resection. Intraventricular hemorrhages or cerebellar swellings during immediate postoperative period might cause fatal hydrocephalic attack, therefore EVD or shunt might be recommended in selected cases.

Review of the posterior fossa tumor with hydrocephalus in 41 cases in the Neuro Surgical Department of Cho Ray hospital

This is a retrospective study on 41 cases with hydrocephalus caused by posterior fossa tumors treated at neurosurgery Dep., Cho Ray hospital from 1993 to 1995. All child patients entering the study had the intracranial pressure syndrome and evidence clinical, paraclinical symptoms. 18/41 cases had cerebellar symptoms (50%). 27 cases had the pathological results after tumor removal in which 20 cases were medulloblastoma (74.04%). The percentage of patients becoming worse postoperatively was still high: 7/27 cases (25.92%). To enhance the quality of treatment, it is necessary to make the diagnosis early and treat the patients actively.

Transient Mutism following Resection of 4th Ventricle Choroid Plexus Papilloma in a 6-Year-Old Girl

Transient mutism has ben known as a rare complication following a posterior fossa approach to cerebellar tumors, although its pathophysiology remains unclear. Cerebellar mutism may be defined as a transient mutism occurring after a posterior fossa tumor approach in children with unimpaired consciousness, unimpaired symbolic functions, no detectable deficit of cranial nerves or peripheral organs of speech, and no lesions of long pathways in the course of the cranial nerves at the level of the brain stem. Forty two cases in children, and only two cases in adults have been found in the literature. We report a case of transient mutism with oropharyngeal apraxia after total excision of 4th ventricle choroids plexus papilloma in a 6-year-old girl. Postoperatively, the patient became mute and refused food intake without disturbance of consciousness, or lower cranial nerve function. Computed tomography(CT) and magnetic resonance image(MRI) demonstrated no abnormal findings except the surgical lesion in the posterior fossa. The mutism lasted for 3 weeks, but she gradually became fluent. The mechanism of "cerebellar mutism" is briefly discussed with literature review.

Histopathological Analysis of Posterior Fossa Tumor

The posterior fossa, containing roughly 6ne fourth of the intracranial contents, is the site of about 30-35% of the intracranial tumors. The incidence of primary tumors in the posterior fossa is quite different from that of the cerebivm. We analysed 124 cases of posterior fossa tumor, over a 10 year period, to understand the status of posterior fossa tumor and its histologic characteristics. Medulloblastoma was most common(37cases, 29.8%), followed by astrocytoma, hemangiobla-stoma, ependymoma, meningioma, metastatic tumor, arteriovenous malformation and choroid plexus papilloma in descending order of frequency. Tumors were found most frequently between the ages of two and ten years(28.2%) and sixty seven(54.0%) cases were diagnosed before the age of fifteen. The ratio of male to female was 60 : 64. Astrocytoma revealed a characteristic juvenile pilocytic type and a microcystic change. Hemangioblastoma showed higher frequency(17.7%) than previous reports and the origin of tumor cells is still equivocal. Other tumors revealed the same histologic features as other intracranial tumors.

Mutism after Posterior Fossa Tumor Surgery in a Child: Case Report

The authors experienced a case of mutism developed after the posterior fossa tumor surgery in a child. Mutism is a symptom mainly developed by supratentorial lesion in organic form. The possible pathogenesis of mutism after posterior fossa tumor surgery is discussed with a review of 18 additional previously reported cases.