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OBJECTIVE: The purpose of Clinical Problem Solving articles is to present management challenges to give practicing neurosurgeons insight into how field leaders address these dilemmas. This illustration is accompanied by a brief review of the literature on the topic. PRESENTATION: The case of a 16-year-old boy presenting with headaches is presented. The patient is found to have a typical colloid cyst at the foramen of Monro. Bilateral ventriculoperitoneal shunt placement had been performed as an initial treatment of the patient before presentation. RESULTS: Surgeons experienced in open and endoscopic surgery discuss their individual approaches to colloid cysts, in the context of previous shunting, providing a varied perspective on the clinical challenges posed by these lesions. CONCLUSION: Both open and endoscopic options remain viable for excision of a colloid cyst. Each has associated potential complications, as illustrated by the current case.

The supraorbital eyebrow craniotomy is an anterolateral approach that allows the surgeon to address diverse pathology of the anterior cranial fossa, parasellar region, proximal sylvian fissure, ipsilateral circle of Willis, basal frontal lobe, and ventral brainstem. When supplemented with intracranial endoscopy, lesions of the lateral cavernous sinus, pituitary fossa, contralateral circle of Willis, and ipsilateral retroorbital space may be addressed. The goals of the approach are to treat neurosurgical lesions using a less-invasive technique, limit brain retraction and tissue trauma by exploiting anatomic corridors, offer comparable safety and efficacy relative to standard approaches, and yield a good cosmetic result.

Spontaneous ventriculocisternostomy, the spontaneous communication between the ventricular system and the subarachnoid space, is rare. The authors report a case of an infant with obstructive hydrocephalus who developed a spontaneous third ventriculocisternostomy. The infant was initially evaluated for progressive ventriculomegaly and increasing head circumference (HC). During follow-up, the patient's HC began to follow percentile lines and magnetic resonance (MR) imaging demonstrated a reduction of the hydrocephalus. Flow-sensitive phase-contrast cine MR images revealed cerebrospinal fluid (CSF) flow through the floor of the third ventricle between the tuber cinereum and the mammillary bodies connecting the ventricular system with the prepontine cistern. Although rare, clinicians should be cognizant of this phenomenon as it may eliminate the need for CSF diversion.

OBJECTIVE: Microvascular decompression may fail to relieve trigeminal neuralgia because a compressing vessel at the root entry zone may be overlooked during surgery. Alternatively, effective decompression may not always be achieved with the visualization provided by the microscope alone. We theorized that the addition of an endoscope would improve the efficacy of microvascular decompression. METHODS: We retrospectively reviewed microvascular decompression of the trigeminal nerve in 114 patients. Before closure, the endoscope was used to inspect the root entry zone. When visualization with the microscope was poor, the endoscope was used to identify an aberrant vessel and to perform or improve the subsequent decompression. RESULTS: Of 114 patients who underwent microvascular decompression, 113 successfully underwent endoscopy. In 38 patients (33%), endoscopy revealed arteries that were poorly seen (25%) or not seen at all (8%) with the microscope. At a mean follow-up period of 29 months, the pain was completely relieved in 112 patients (99.1%), all of whom were off medication. Complications included trigeminal dyses-thesias in nine patients and a wound infection, partial hearing loss, and complete hearing loss in one patient each. The overall complication rate was 9%. CONCLUSION: Endoscopy is a simple and safe adjunct to microscopic exploration of the trigeminal nerve. The markedly improved visualization increases the likelihood of identifying the offending vessel and consequently of achieving satisfactory decompression of the nerve. Thus far, the success rate has been high, and the complication profile is comparable to that of other large series.

Among the numerous complications of ventriculoatrial shunting, discontinuity and migration of a catheter fragment into the heart or pulmonary arteries is only rarely encountered. Percutaneous snare retrieval of shunt tubing from the pulmonary arteries is described in a patient presenting with signs of shunt malfunction.

The purpose of this study was to evaluate the efficacy of a minimally invasive/endoscopic approach to craniopharyngiomas (CPGs) given that the surgical aim was a complete excision of the tumor as a single stage procedure. The endoscope can be used with both a subfrontal and a transsphenoidal approach. This study is a retrospective review of 36 operative patients who were seen by one surgeon. All patients had attempted complete excision. Patients were divided into three groups according to their preoperative status. Those in group 1 had no previous treatment and fared well, although all developed postoperative diabetes insipidus. Those in group 2 had previous surgery only and also did well with repeat surgery. Those in group 3 had been treated previously with surgery and radiotherapy and, apart from a single exception, did poorly. The endoscopic, minimally invasive approach is versatile and effective in the surgical management of both first-time and repeat cases of CPG. It offers superior visualization of surrounding neurovascular structures and allows a more complete resection of tumor. It can be used for a cranial or a nasal approach to these tumors. Sadly, it failed to prevent postoperative endocrinopathy.

The management of a patient with an ependymoma is controversial. Although the necessity for a multi-disciplined approach is accepted, the exact roles for all disciplines are poorly defined.This review article examines the current status of histopathological and cytogenetic diagnosis, surgical, chemotherapeutic and radiotherapeutic treatment and future directions.

This article reviews the range of hydrodynamic disorders affecting the CSF circulation. Initially consideration is given to questions of definition and classification. A scheme for the practical, clinical analysis for the diagnosis of such disorders is then presented. The physiology and pathophysiology of the CSF circulation is reviewed, with particular emphasis on issues that remain unresolved. This provides a background to consideration of the adverse consequences of abnormal CSF hydrodynamics, again focusing on areas where further information is required. Methods of clinical investigation of CSF hydrodynamics are reviewed, followed by general considerations of treatment. Finally, each of the main, clinically important, forms of disordered CSF hydrodynamics is briefly considered, with particular emphasis, again, on areas where current knowledge is deficient. The conditions considered include hydrocephalus of various forms (childhood, adult, arrested, multi-compartment), infantile macrocephaly, arachnoid and glioependymal cysts, syringo- and hydromyelia, pseudotumour cerebri, impaired cranial venous outflow, altered CSF composition, shunt obstruction without ventricular enlargement and low-CSF-pressure states.

Applying the concept of keyhole techniques to neurosurgery has divided the neurosurgical community. This should never have happened because keyhole refers to a philosophy not a size. This philosophy stems from a desire to minimize collateral damage without compromising the intended goal of surgery. The revolution received its impetus from technological advances in pre- and intraoperative navigation, use of surgical-friendly anesthetic agents, lower profile instruments, the introduction of hemostatic agents, and better visualization. If a smaller craniotomy compromises the goal of surgery, then the approach should be re-evaluated and modified to achieve minimal collateral damage and maximal efficacy.

Cefpodoxime is an oral third-generation cephalosporin used for the treatment of acute upper-respiratory tract infections caused by susceptible bacteria in children. Although not indicated for the treatment of bacterial meningitis, it is used to treat other infections produced by organisms associated with meningitis and may obscure the result of cerebrospinal fluid (CSF) cultures in children who develop meningitis while receiving oral antibiotics if sufficient concentrations are achieved in the CSF. This study evaluated the disposition of cefpodoxime and penetration into CSF in piglets. Fifteen Landacre-Camborough cross piglets (10-20 days old) received cefpodoxime proxetil oral suspension (10 mg/kg). Repeated plasma and CSF samples were collected over 24 hours for quantitation of cefpodoxime by HPLC. Pharmacokinetic analysis was performed on both plasma and CSF data. The plasma concentration versus time data for cefpodoxime were best characterized using a one-compartment model with first-order absorption. The mean (+/- SD) pharmacokinetic parameters for Cmax, tmax, and AUC0-infinity were 23.3 +/- 12.9 mg/L, 3.9 +/- 1.4 h, and 237 +/- 129 mg/L.h, respectively. CSF/plasma ratios for AUC0-infinity demonstrated a mean cefpodoxime penetration of approximately 5%. CSF penetration of cefpodoxime was evident following a single oral dose of cefpodoxime proxetil suspension. Despite the small percentage of total cefpodoxime dose distributing into the CSF, the resultant concentrations approached or exceeded the MIC90 for many bacterial pathogens considered susceptible to cefpodoxime. Accordingly, clinicians should use caution in the interpretation of CSF cultures in patients who develop clinical signs and symptoms consistent with meningitis and who have been previously treated with cefpodoxime.

Thirty patients between the ages of 7 months and 24 years were treated surgically for symptomatic Chiari II malformation at the Arkansas Children's Hospital. All patients underwent at least bony decompression of the malformation. Assessments of the patients' conditions were made at 6 weeks and 1 year after surgery, and complications of surgery were noted. For a majority of the patients, the presenting symptoms were resolved following treatment (74% at 6 weeks and 80% at 1 year). Partial resolution occurred in several of the patients (17% at 6 weeks and 14% at 1 year). A small number remained the same at 6 weeks (6%) and at 1 year (3%), while 1 patient was worse after surgery. Ten of the patients with complete resolution in the short term required repeat surgery an average of 49 months after their original operation, after which they again attained complete resolution of their symptoms. Scales for clinical, radiographic and operative grading of the patients' conditions as mild, moderate or severe were devised, and these were employed to characterize the condition of each patient. Patients in each grading category had good results, with rates of complete symptomatic resolution ranging from 67 to 100%. Severity in each category was found to be well correlated with eventual recurrence of symptoms and need for reoperation.

The P1 midlatency auditory evoked potential was studied in patients with Parkinson's disease and compared to that in age-matched controls. Habituation of the potential was determined by using a two-click stimulus paradigm in which the stimuli were presented at 250-, 500-, and 1,000-ms interstimulus intervals. Results showed that habituation of the P1 potential had a statistically significant decrease at the 250-ms and 500-ms interstimulus intervals in patients with Parkinson's disease compared to normal controls. The degree of decreased habituation was found to increase with severity of the disease such that stage 5 patients showed greater decreases in habituation compared to stage 4, as did stage 4 compared to stage 3. These findings may be explained by the presence of a dysregulation of sensory processing, possibly by elements of the reticular activating system, including the pedunculopontine nucleus, in Parkinson's disease.

Advances in molecular biology have established that the diseases once collectively referred to as neurofibromatosis are actually genetically distinct and clinically heterogeneous conditions. This realization has led to separate definitions for neurofibromatosis (NF) type 1 and 2. Although ophthalmologic manifestations of NF1 have long been recognized, the distinguishing ocular features of NF2 have only recently received attention. We describe an inferior retinopapillary malformation with an overlying glial hamartoma in a deaf, quadriparetic patient with NF2. Magnetic resonance (MR) imaging initially showed bilateral vestibular schwannomas and a large cervical ependymoma. Over six years of follow-up, the patient developed multiple intracranial meningiomas.

Endoscopic third ventriculostomy (ETV) was performed between July 1978 and July 1995 on 69 patients with hydrocephalus and myelomeningocele. Most of the patients had been previously shunted, although in 14 patients ETV was the initial treatment. Patient selection was based on preoperative imaging studies suggesting noncommunicating hydrocephalus. Only 2 patients exhibited transient hypothalamic dysfunction with complete resolution. Patients were assessed by their clinical status, imaging characteristics, and, in some cases, formal psychometric studies. The overall success rate was 72%, although selecting only patients who have been previously shunted or who were over 6 months of age at the time of endoscopy increases this to 80%. Our results indicate that ETV is a safe and effective means of treating hydrocephalus in the older spina bifida population and offers the hope of long-term, shunt-independent life for selected patients.

Neuroendoscopy is rapidly becoming an essential part of the neurosurgeon's repertoire. Currently, very few studies have identified the complications of this new technique, yet many have warned of the steep learning curve associated with its practice. We have reviewed the last 173 neuroendoscopic procedures performed by one surgeon and identified two distinct groups of complications: those that have clinically significant sequelae and those that cause concern intraoperatively but no overt clinical problems. The 173 procedures were performed on 152 patients. Of these patients, 11 suffered significant complications (7%). Twenty-two of the procedures were complicated by intraoperative problems (13%). The incidence of insignificant complications appeared to decrease with experience, whereas that of the significant ones did not. These complications occurred in association with a wide variety of operations over a 2-year period. We conclude that neuroendoscopy is a relatively safe technique with an overall 7% complication rate and a steep learning curve, and that, with a few simple guidelines, it can be employed by all neurosurgeons for the betterment of their patients.

Technical advances in neurosurgery follow a general philosophy favouring less invasive means of managing surgical disease.We describe a patient with a symptomatic type I Chiari malformation managed by posterior fossa decompression using endoscopic tech niques. Technical considerations, including drawbacks of the proceedure, are discussed.

We have operated on 47 patients, achieving significant improvement or total shunt independence in 80% with only one major complication. We have not restricted the procedure only to those with late onset aqueduct stenosis, but rather have included 29 patients with both early and late onset aqueduct stenosis, 8 patients with associated myelomeningocoele, 7 patients with neoplastic secondary aqueduct stenosis and 3 patients with previous central nervous system (CNS) infection or hemorrhage. We believe that a procedure which carries an appreciable failure rate is acceptable if the only alternative to improve patient selection is an invasive and time-consuming investigation such as a cerebrospinal fluid (CSF) infusion study. Such a study may or may not identify those patients in whom CSF absorptive capacity is inadequate. Furthermore, this study illustrates two important principles that may improve the overall outcome of third ventriculostomy. Firstly, comprehensive preoperative structural studies will help to eliminate some of those patients anatomically unsuitable for this procedure. Secondly, an adequate period should be allowed to pass before declaring the operation unsuccessful, as head growth did not show an improved trend for several weeks in two patients. We believe that in these patients, the CSF absorptive capacity improved over that time.

During the period 1978–1988, 340 children with hydrocephalus have been controlled by the Heyer-Schulte valve with antisiphon device (ASD). No children with tumors are included. There were 99 primary insertions; 42 in infants with myelomeningocele. The mean follow up was 7 years. During this time, in the 225 children without myelomeningocele, revision of the ventricular catheter was required on 29 occasions.

Management of the obstructive hydrocephalus that accompanies tumors located in the third ventricle has traditionally involved either urgent tumor resection, with resultant ventricular decompression, or cerebrospinal fluid diversion that requires either ventriculostomy or shunt placement prior to tumor removal. Although this approach has worked well for the better part of a century, it has both short- and long-term sequelae that can possibly be avoided. Beacause a number of lesions in this area are benign or are amenable to radiotherapy, a less invasive approach to their treatment is desirable. The advances in both instrumentation and techniques of endoscopic surgery have established alternatives to the traditional treatment of third ventricular tumors and resultant hydrocephalus. The authors review the treatment of 19 patients with posterior third ventricular tumors who presented to Arkansas Children's Hospital over a 5-year period (September 1993–July 1999). In 11 patients signs and/or symptoms of hydrocephalus were demonstrated and were treated with endoscopic third ventriculostomy, additionally, a biopsy procedure, resection, or fenestration of the tumor was performed in a number of patients. Endoscopy was believed to have been of benefit in all patients, despite the eventual failure of the ventriculostomy in one patient. There were no complications in this series. The algorithm thus developed by the authors provides both a diagnostic and therapeutic pathway that may ultimately reduce the morbidity associated with the treatment of patients with posterior third ventricular lesions.

The ideal management of colloid cysts is controversial. Treatment options include shunting procedures, stereotactic cyst aspiration, open craniotomy for microsurgical removal, and endoscopic removal. Although recent literature would suggest endoscopic removal is a reasonable approach, issues of safety and efficacy have dampened the universal acceptance of this surgical modality. The author performed a retrospective anaylsis to address these controversial issues. The charts of all patients in whom endoscopic removal of colloid cysts was performed by the primary author at the University of Arkansas for Medical Sciences were reviewed. Eighteen patients underwent this procedure over the last 5 years. The mean patient age was 32 years, and the mean follow-up period was 32 months. In all patients complete tumor removal was macroscopically and radiologically confirmed, and there were no permanent deficits. Two patients suffered aseptic meningitis without long-term sequelae. There were no deaths and no incidence of tumor recurrence. The results of this series support those previously published that underscore the advantages of endoscopic removal of colloid cysts. The procedure is safe and effective. Longer follow-up review is required to address the issue of duration of tumor-free survival.

• We report a series of eight cases that show a close resemblance to, but are not identical with, pseudotumor cerebri (PTC) as normally defined. The majority of these cases are characterized by raised intracranial pressure without ventriculomegaly. They include two cases of cranial venous outflow obstruction in which clinical or radiologic abnormalities precluded the diagnosis of PTC proper (cases 1 and 2); one case of chronic meningitis in which an abnormal cerebrospinal fluid (CSF) composition precluded the diagnosis of PTC (case 3); two cases without either papilledema or a measured increase of CSF pressure, which in other respects, particularly in response to treatment, resembled PTC (cases 4 and 5); and three cases of what is thought to represent an infantile form of PTC (cases 6 through 8). The purpose of the analysis of these cases is twofold. First, it is argued that these cases throw light on the mechanism of PTC itself, supporting a concept of a disturbance of CSF circulation in this condition, and that they are themselves illuminated by considerations of typical PTC. Second, the cases are used to frame a proposed classification of the pseudotumor syndrome aimed at broadening the diagnostic criteria applied currently to PTC. It is suggested that the pseudotumor syndrome has a single underlying mechanism (disturbed CSF circulation) and that recognition of this mechanism not only clarifies the pathophysiologic processes of PTC but also has important diagnostic and therapeutic implications.

✓ A case is reported of a rare cystic schwannoma of the fourth cranial nerve which was interpreted as a probable intrinsic brain-stem lesion. The clinical approach to brain-stem tumors in terms of empirical treatment or surgical biopsy is discussed.