Complications in ventricular cerebrospinal fluid shunting

The development of effective cerebrospinal fluid (CSF) shunts represents a landmark achievement in neurosurgery. This success, however, has been tempered by a high incidence of serious complications that accompany the diversion of CSF. This article examines the various complications of CSF shunting, including proximal, valve, and distal obstruction; infection; and other rare complications, and management of these complications.

Intracanalicular acoustic neuroma: early surgery for preservation of hearing

Diagnosis of very small acoustic neuromas has become much more common since the advent of magnetic resonance imaging. Many of the patients so diagnosed have minimal unilateral hearing loss as their only symptom. Because limited information is available on the natural history and prognosis of these lesions, the choice of treatment is controversial. The authors review their recent experience with the surgical treatment of intracanalicular acoustic neuroma. The records of 14 consecutive patients with intracanalicular acoustic neuroma were reviewed with respect to type of presentation, pre- and postoperative facial and auditory nerve function, surgical approach, and complications. Detailed results for patients operated on to preserve hearing are presented. Presenting symptoms were nearly equally divided among diminished hearing, vertigo, and tinnitus. Eleven of the 14 patients had serviceable hearing preoperatively and nine (82%) remained in this condition postoperatively. Facial nerve function was unchanged by operation in 12 patients. Seven operations were performed through the middle fossa, five through the posterior fossa, and two by the translabyrinthine approach. The probability of preserving hearing during surgical excision of intracanalicular acoustic neuroma in patients with serviceable hearing exceeds 80%. Given the relative infrequency of serious complications and the likelihood of progressive hearing loss in the untreated patient, excision of such small tumors shortly after diagnosis may offer the best chance of long-term hearing preservation.

Experimental brain stem surgery

Few models of experimental brain stem surgery exist in the literature. Often, experiments were devised in the animal laboratory after a similar surgical procedure already had been attempted on human subjects. Many of the experiments referenced in this article were performed with the goal of delineating neuroanatomic or neurophysiologic pathways, and then this information was used to develop new techniques in the clinical arena, such as BAERs. A new model for brain stem hemorrhage is presented in this article as well as a comparison of the outcomes of open surgical evacuation, stereotactic aspiration, and control animals with pontine hemorrhages.

History of brain stem surgery

The earliest surgical procedures on the brain stem parenchyma were directed at sectioning specific fiber pathways to alleviate pain. Subsequently, some tumors, abscesses, and vascular lesions that displace rather than invade the parenchyma have been successfully removed. Future advances depend on the ability to preserve and restore neural function in operated tissue.

Primary pontine hemorrhagic events. Hemorrhage or hematoma? Surgical or conservative management?

The pathophysiology of primary pontine hemorrhagic events is unclear, but the traditional classification of hemorrhage or hematoma does not have either pathologic or clinical support. Reported cases of brain stem hemorrhage suggest that patients who suffer progressive deterioration from hemorrhagic pontine lesions may benefit from surgery even if they eventually become comatose, whereas those who suddenly lose consciousness and have profound neurologic deficit probably will not survive.

Tympanic and transtympanic electrocochleography in acoustic neuroma and vestibular nerve section surgery

Eighth nerve action potential (AP) amplitudes and latencies and cochlear microphonic (CM) amplitudes were compared using tympanic and transtympanic electrocochleography (ECOG) in two patient groups. Tympanic ECOG was performed with a wick electrode placed on the tympanic membrane (TM). Transtympanic ECOG was performed with a needle electrode placed on the promontory of the anesthetized patient. Eighteen subjects were tested by tympanic ECOG as part of a preoperative assessment for either acoustic neuroma removal or transection of the vestibular portion of the eighth cranial nerve. Surgery occurred within 1 week of the preoperative evaluation. Intraoperative auditory monitoring was performed using transtympanic ECOG. Baseline recordings were compared to the preoperative tympanic ECOG data. Stimuli were condensation and rarefaction clicks and tone bursts, presented by an insert earphone. As expected, the two methods resulted in essentially identical response latencies and large amplitude differences, although the response amplitudes were extremely variable. The AP amplitude and the CM amplitude did not increase by the same factor with the transtympanic (TT) electrode compared to the tympanic electrode. On comparison of preoperative and intraoperative response amplitudes with regard to stimulus polarity, tympanic electrocochleography appears to be a useful method of gathering preliminary information on the status of the patient's auditory system. In this study, tympanic ECOG was found to have some predictive value when trying to ascertain the best intraoperative monitoring situation.

Multiloculated hydrocephalus: craniotomy and fenestration of intraventricular septations

Ten pediatric patients with multiloculated hydrocephalus caused by neonatal meningitis, ventriculitis, or intraventricular hemorrhage were surgically treated over a 14-year period (January 1, 1976, to December 31, 1990). Six patients underwent craniotomy and transcallosal fenestration of intraventricular septations followed by placement of a shunt, while the other four were treated by shunting procedures alone. Craniotomy resulted in reduction of the shunt revision rate from a median of 2.75 per year prior to fenestration to 0.25 per year following fenestration, with median observation periods of 44.5 and 27 months, respectively. This was compared to a median revision rate of 0.55 per year for patients treated with shunting procedures alone. There were no deaths in either group. Although no surgical complications were encountered, one patient did require a second fenestration procedure. The important aspects of multiloculated hydrocephalus, including pathophysiology, radiographic correlates, and treatment options, are discussed. The goal of treatment is to eliminate the need for multiple shunt revisions, minimizing the accompanying morbidity and expense. It is concluded that craniotomy and transcallosal fenestration of intraventricular septations is a successful treatment of multiloculated hydrocephalus.

Pediatric skull, skull base, and meningeal tumors

Calvarial neoplastic and non-neoplastic tumors are routinely encountered by all neurosurgeons. Benign and malignant skull base and meningeal tumors are relatively rare lesions in children. Interdisciplinary approaches to those tumors more frequently encountered in the pediatric population in these locations are discussed. Unique aspects of the diagnosis, treatment, and prognosis for infants and children are discussed.

Effects of 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP)-induced hemiparkinsonism on the kinematics of a two-dimensional, multijoint arm movement in the rhesus monkey

The effects of the selective dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) on the kinematics of two-dimensional arm movements in the primate were studied. Two rhesus monkeys were trained to move a manipulandum at various distances and directions in horizontal space from a centrally located target box. Several kinematic parameters including reaction time, and time and amplitude of peak tangential velocity were analysed. Following an extensive control evaluation period, the animals were unilaterally injected with MPTP into the internal carotid artery. The animals were restudied for up to 289 days following induction of hemiparkinsonism. Larger-amplitude movements (greater than 3.5 cm) were more severely affected than smaller amplitude movements. Both animals exhibited marked changes in the arm movements including increased time-to-peak velocity and decreased peak velocity. The degree of the kinematic changes was spatially dependent, with the decrease in velocity as well as the time-to-peak velocity being more pronounced for the larger, outward movements. Reaction time increased but showed no spatial dependency. Kinematic deficits persisted over the entire time-period studied. Also, the kinematic changes were reduced by levo-3,4 dihydroxyphenylalanine in a dose-dependent manner. Tyrosine hydroxylase immunohistochemistry documented extensive cell loss in the substantia nigra. These results show that both the timing as well as the amplitude of the velocity profiles are disrupted by MPTP consistent with the known akinesia and bradykinesia of parkinsonism. Although abnormalities were present for all directions and distances, a spatial dependency to the deficits was detected. The observation of more pronounced changes for larger, outward movements suggests a role for the basal ganglia in production of larger-amplitude movements directed away from the body.

Infections in neurologic surgery. The intraventricular use of antibiotics

Intraventricular antibiotic therapy appears to be a useful treatment modality in those CSF infections in which systemic therapy may fail. Consideration should be given to using this form of treatment when infecting organisms are only sensitive to antibiotics with poor penetration of the CSF (e.g., aminoglycosides and vancomycin) and for cases in which intravenous therapy has failed to sterilize the CSF, toxicity from systemic therapy precludes further increases in dosages, and shunts or other CSF hardware might be expected to reduce the efficacy of systemic therapy by providing a foreign body to harbor organisms. Shunts or reservoirs that are infected may be successfully sterilized with IVT therapy alone or in conjunction with systemic therapy, but this has a lower success rate than cases in which the shunt is removed. There is a wealth of clinical experience with IVT vancomycin and gentamicin that suggests that they are relatively safe. Until more data are available on other aminoglycosides and newer antibiotics, these two agents should be considered the antibiotics of choice for IVT therapy. In situations in which the organism is sensitive to both vancomycin and gentamicin, vancomycin should be used in view of the documented neurotoxicity seen with gentamicin. When gentamicin resistance occurs, amikacin and tobramycin are appropriate alternatives. The high risk of epilepsy with the penicillins and cephalosporins makes them less suited for IVT therapy, although the newer cephalosporins have some promise for IVT therapy. CNS fungal infections can be treated effectively with IVT amphotericin B but with a high risk of significant toxicity. Miconazole appears to be safer than amphotericin B but there is less clinical experience with this drug. Table 1 summarizes the dosages, indications, and toxicity of those antibiotics commonly used for intraventricular administration, which have been reported previously.

Antibiotic prophylaxis in neurosurgery. The controlled trials

Systemic antibiotics are effective in reducing the risk of infection after clean neurosurgical procedures. They are less effective in preventing shunt infection, but are strongly recommended in institutions experiencing a shunt infection rate exceeding 15%. The role for antibiotic prophylaxis using topical agents and in the prevention of meningitis associated with cerebrospinal fluid drainage is uncertain.

Esthesioneuroblastoma presenting as sudden unilateral blindness. Histopathologic confirmation of optic nerve demyelination

We report here a case of esthesioneuroblastoma an 11-year-old girl presenting as acute loss of vision with minimal evidence of orbital, nasal, or paranasal sinus disease, a rare presenting symptom for this tumor. The initial diagnosis was postviral optic neuritis, a pattern of presentation not previously reported. When vision failed to improve, magnetic resonance imaging revealed a lesion in the posterior ethmoid and sphenoid sinuses. After a biopsy, the tumor was excised through the cranium and paranasal sinuses. A mass completely surrounding the optic nerve without invasion was found. Histochemical staining suggested demyelination secondary to compression, confirming the clinical impression of optic neuritis. Anti-Leu 7 monoclonal antibody is useful in characterizing of this tumor, since other immunochemical stains can be misleading. Radiation and chemotherapy were given after the tumor was removed. Two years later, the patient has had neither recurrence nor complications.

Microsurgical management of craniopharyngiomas

A retrospective analysis of 34 patients who underwent microsurgical therapy for craniopharyngioma from 1975 to 1989, a period when CT imaging was routinely used, is presented. Mean follow-up was 6.4 years with no patients lost to follow-up. Those who underwent subtotal resection with adjuvant radiation had a significantly better recurrence-free interval compared with those who either underwent total or subtotal surgical resection only (p < 0.05 and p < 0.025). Among patients treated with surgery alone, the total resection group had a recurrence rate of 20% and those with a subtotal resection 60%. Those with subtotal resection and radiation had a 12% rate of recurrence. Endocrine and visual deficits were common after surgery. Based on this review, our results suggest that with a policy of attempted total resection where possible, subtotal removal along with adjuvant radiation, in cases where total resection was deemed unsafe, may be more effective than aggressive total resection alone as the initial management of craniopharyngioma.

Subependymoma of the cervical spinal cord. A case report of long-term survival

Subependymomas of the cervical spinal cord are relatively rare tumors. Thirteen cases have been reported in the literature with the longest reported follow-up and survival being six years. This paper describes a woman who survived for 14 years in reasonably good health after her diagnosis of cervical spinal cord intramedullary subependymoma. A review of reported cases and a discussion of subependymomas and their characteristics is included.

Elevated intracranial pressure from cerebral venous obstruction by Masson's vegetant intravascular hemangioendothelioma. Case report

The case is described of a 15-year-old girl with papilledema and visual obscurations caused by a rare lesion, Masson's vegetant intravascular hemangioendothelioma, within the venous sinus at the torcular herophili. This lesion impeded cranial venous outflow, leading to intracranial hypertension.

Relative value of diagnostic tests for small acoustic neuromas

Auditory brainstem response is now widely employed as a screening test for acoustic neuromas because it is equally sensitive when standardized against computed tomography. We have detected eight small (less than 10 mm) acoustic neuromas using gadolinium enhanced magnetic resonance imaging. In three of these cases, the auditory brainstem response was falsely negative. In contrast, 19 patients with larger tumors (greater than or equal to 10 mm) were found to have no false negative auditory brainstem responses. Auditory brainstem response appears to be less sensitive for detecting small, symptomatic acoustic neuromas.

Current treatment of Chiari malformations types I and II: A survey of the Pediatric Section of the American Association of Neurological Surgeons

The membership of the Pediatric Section of the American Association of Neurological Surgeons was surveyed with regard to attitudes in current practice in the treatment of Chiari malformations Types I and II. Ninety-six of 152 (63%) valid questionnaires were returned. The median number of malformations treated yearly by the respondents was 3 for Type I and 6 for Type II. There was substantial agreement that surgery should not be carried out on asymptomatic patients and that surgery was indicated for the treatment of brain stem dysfunction, cranial nerve dysfunction,, hydromyelia, and scoliosis associated with these malformations. There was substantial disagreement about lesser indications for surgery. The respondents also expressed dissatisfaction with the current classification of Chiari malformations. Chiari malformations are complex abnormalities, and their anatomy is being better delineated with magnetic resonance imaging. Carefully designed scientific clinical investigations are needed to improve our understanding and treatment of Chiari malformations.

Intraoperative monitoring of the facial nerve during decompressive surgery for hemifacial spasm

In 11 consecutive patients, intraoperative electromyographic (EMG) recordings were made from the facial muscles during microvascular decompression for hemifacial spasm. In one patient, recordings could not be obtained for technical reasons, and two patients had no abnormality. In the remaining eight patients, the abnormal response resolved before decompression in two, resolved immediately at the time of decompression in five, and failed to resolve in one. All patients were relieved of their hemifacial spasm. In the five patients whose abnormalities resolved at the time of decompression, there was a precise intraoperative correlation between decompression of the nerve and disappearance of the abnormal EMG response. In three cases, this was a useful guide to the need to decompress more than one vessel. These results confirm the findings of Møller and Jannetta, support the use of this technique for intraoperative monitoring of facial nerve decompression procedures, and provide strong circumstantial evidence that vascular cross-compression is an important etiological factor in hemifacial spasm.

Familial hemifacial spasm associated with arterial compression of the facial nerve. Case report

This report of an 88-year-old woman with familial hemifacial spasm includes the first published postmortem description of hemifacial spasm with cross-compression of the seventh cranial nerve root exit zone by a redundant loop of the anterior inferior cerebellar artery and associated vascular plexus. Histological examination of the seventh and eighth cranial nerve complex suggested nerve degeneration because increased numbers of corpora amylacea were present just distal to the compression concavity. There was no evidence of demyelination or gliosis of the nerve. This case suggests that vascular compression of the nerve root exit zone is an important condition in the etiology of most of these cases. This is the third reported case of familial hemifacial spasm; to date, all such patients have had left facial involvement. The family pedigree in this case suggests a pattern of autosomal-dominant inheritance with partial penetrance. The genetic basis for familial hemifacial spasm may involve anatomical variants or anomalies of the posterior circulation, since both posterior inferior cerebellar arteries were congenitally absent in this case.

Lesioning of the striatum reverses motor asymmetry in the 6-hydroxydopamine rodent model of parkinsonism

In the rat several paradigms of grafting of adrenal medulla into the striatum were studied following the induction of a parkinsonian model, using a unilateral 6-hydroxydopamine (6-OHDA) lesion of the substantia nigra. Direct autologous grafting of adrenal medulla into the caudate-putamen complex, a radiofrequency lesion of the striatum alone, and a radiofrequency lesion followed by delayed grafting of adrenal medulla were compared by analyzing rotational behavior. Direct grafting of adrenal medulla produced an overall reduction in apomorphine induced turning behavior by 43.5% when compared with controls. Radiofrequency lesioning of the striatum without graft showed the best improvement over control animals with a 92% reduction in the total number of rotations induced by apomorphine. Delayed grafting into the caudate lesion cavity also produced a dramatic reduction in motor asymmetry but did not improve the behavioral outcome over that of the lesion alone. Animals receiving only radiofrequency lesions exhibited a band of increased tyrosine hydroxylase like immunoreactivity bordering the lesion cavity. Graft survival was limited in the non-lesioned animals but appeared enhanced in the animals whose striatum was previously lesioned. Lesion location within the striatum influenced the behavioral outcome. Large reductions in apomorphine-induced rotations could result from small lesions of the dorso-lateral striatum. These findings indicate that selective destruction of the caudate-putamen complex without tissue transplantation produces a dramatic reduction in the motor asymmetry of 6-OHDA treated rats. Suggested explanations for the decrease in induced rotational behavior with radiofrequency lesions include a decrease in the number of striatal dopamine receptors following cell destruction and lesion-induced recovery of host dopaminergic afferents. Striatal damage in critical areas can reverse some of the motor behavior associated with the 6-OHDA model and needs to be considered when evaluating the effects of neural grafting in this model.

Risk of late stroke and survival following carotid endarterectomy procedures for symptomatic patients

The long-term outcome following carotid endarterectomy for neurological symptoms was analyzed using a retrospective life-table approach in 212 patients who had undergone 243 endarterectomy procedures. The postoperative follow-up period averaged 38.9 +/- 2.1 months (mean +/- standard error of the mean). The endpoints of stroke and death were evaluated in these patients. Patient groups with the preoperative symptoms of amaurosis fugax, transient ischemic attack, and prior recovered stroke were similar in terms of life-table outcome over the follow-up period. Sixty-two percent of symptomatic patients were alive and free of stroke at 5 years. The late risk of stroke (after 30 days postoperatively) averaged 1.7% per year based on a linear approximation to the hazard at each life-table interval (1.3% per year for ipsilateral stroke). The trend of late stroke risk was clearly downward, however, and could be fitted more accurately by an exponential decay function with a half-life of 33 months. Thus, the risk of stroke following carotid endarterectomy for neurological symptoms was highest in the perioperative period, slowly declined with time, and occurred predominantly ipsilateral to the procedure. The definition of a prospective medical control group remains crucial for a critical analysis of treatment modalities following the onset of premonitory neurological symptoms. In the absence of an adequate control group for this series, the calculated perioperative and postoperative stroke risk from this study was compared to data obtained from the literature on stroke risk in medically treated symptomatic patients. This uncontrolled comparison of treatment modalities suggests the combined perioperative and postoperative stroke risk associated with carotid endarterectomy to be modestly improved over medical treatment alone.