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.

Efficacy of antibiotic prophylaxis in clean neurosurgical operations.

Four controlled trials and one case control study have presented data supporting the efficacy of perioperative administration of antibiotics in reducing the rate of infection following clean neurosurgical procedures. Their results are, for the most part, consistent with uncontrolled studies reported since 1980. Taken together, these studies clearly and consistently demonstrate the value of perioperative antibiotic prophylaxis in clean neurosurgical operations.

Randomized clinical trials in neurosurgery.

Fifty-one randomized trials of neurosurgical topics have been identified. These have been analyzed for content, quality of reporting, and quality of statistical design and analysis. In general, there were major omissions in the reporting of critical portions of the studies, the statistical analysis was highly variable in quality, and the statistical power was low. Few, if any, major neurosurgical questions have been answered by clinical trials. This may reflect the generally low quality of these trials. To improve the quality of such trials, neurosurgeons must seek biostatistical advice in planning and conducting trials and must cooperate in multi-institutional trials to increase statistical power.

Topical antibiotic prophylaxis in neurosurgery.

Topical antibiotics have been used prophylactically in clean operations by many neurosurgeons. Many others have not used them, however. Review of the experimental literature shows that topical antibiotics will reduce the rate of wound infection in experimentally contaminated wounds. Experience in other surgical disciplines suggests that the infection rate of operations with an intrinsically high risk of infection (greater than 15%) can be reduced substantially by the use of topical antibiotics. There is no sound scientific evidence documenting the benefit of prophylactic topical antibiotics in operations with a risk of infection below 5%. Reports of the use of topical antibiotics in neurosurgery are either uncontrolled or are so fragmentary that no useful-conclusions can be drawn from them. Surgical wounds with a high risk of infection should be treated with intraoperative topical antibiotics. The routine use of topical antibiotics in clean neurosurgical procedures requires further study.

Six statistical suggestions for surgeons.

Statistical analysis has become very important in medical research. The large number and variety of statistical techniques required to appropriately handle different types of medical research make it impossible for most physicians to acquire enough statistical expertise to analyze critically the details of many reports. However, a basic understanding of certain fundamental principles of statistical analysis is vital if statistical errors and misapplications are to be identified and prevented. The basic principles underlying six common statistical errors are discussed and a guide to pertinent literature is provided so that the practicing physician without special statistical knowledge can be in a better position to understand and interpret statistical analysis in the medical literature.

The chymopapain clinical trials.

The three published randomized clinical trials of chymopapain injection vs. placebo injection for the treatment of herniated lumbar discs are reviewed. Despite some differences, the similarities in selection criteria, technique, and outcome assessment are great enough to justify pooling the results to obtain an overall assessment of chymopapain efficacy. These pooled results suggest that the odds of successful outcome (at least some improvement in symptoms after injection) are 2.6 times as great with chymopapain injection as those after placebo injection. This corresponds to a 50% greater probability of success with chymopapain than with placebo or a 23% increase in the number of patients successfully treated with chemonucleolysis over those successfully treated with placebo. The fact that data from 234 patients evaluated in randomized clinical trials could resolve a controversy over therapeutic efficacy that the uncontrolled evaluation of over 20,000 patients could not answer suggests that the current controversy over the relative efficacy of chymopapain and discectomy should be studied in the same way. The difficulties of such a study are discussed.

Systemic antibiotic prophylaxis in neurological surgery.

The clinical and experimental bases for antibiotic prophylaxis in surgery are reviewed briefly. The evidence regarding antibiotic prophylaxis in five specific neurosurgical situations (clean surgical procedures, cerebrospinal fluid shunts, external venticulostomies, basilar skull fractures, and compound skull fractures) is examined. There are no unequivocal indications for antibiotic prophylaxis in neurological surgery. Large scale randomized clinical trials will be required to settle the controversy in some of these areas.

Antibiotic prophylaxis for cerebrospinal fluid shunts: a metanalysis.

The value of antibiotic prophylaxis for clean neurosurgical procedures without the implantation of a foreign body has been conclusively demonstrated. Attempts to confirm its efficacy for cerebrospinal fluid shunt operations have produced confusing and inconclusive results. The objective of this study was to combine the results of high-quality controlled trials of antibiotic prophylaxis for cerebrospinal fluid shunt operations and to determine if there is evidence for the efficacy of this policy. Randomized clinical trials identified from presentations at national meetings and in the published literature were subjected to a metanalysis. The pooled data suggest a statistically significant effect favoring antibiotic prophylaxis (approximately a 50% reduction in infection risk when antibiotic prophylaxis is used). The effect is strongly related to the baseline infection rate when prophylaxis is not used and disappears when the baseline infection rate is at or below about 5%.

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.

Repairing holes in the head: a history of cranioplasty.

Cranioplasty is almost as ancient as trephination, yet its fascinating history has been neglected. There is strong evidence that Incan surgeons were performing cranioplasty using precious metals and gourds. Interestingly, early surgical authors, such as Hippocrates and Galen, do not discuss cranioplasty and it was not until the 16th century that cranioplasty in the form of a gold plate was mentioned by Fallopius. The first bone graft was recorded by Meekeren, who in 1668 noted that canine bone was used to repair a cranial defect in a Russian man. The next advance in cranioplasty was the experimental groundwork in bone grafting, performed in the late 19th century. The use of autografts for cranioplasty became popular in the early 20th century. The destructive nature of 20th century warfare provided an impetus to search for alternative metals and plastics to cover large cranial defects. The metallic bone substitutes have largely been replaced by modern plastics. Methyl methacrylate was introduced in 1940 and is currently the most common material used. Research in cranioplasty is now directed at improving the ability of the host to regenerate bone. As modern day trephiners, neurosurgeons should be cognizant of how the technique of repairing a hole in the head has evolved.

Anticonvulsant prophylaxis in neurological surgery.

Seizures complicate many neurosurgical diseases and, in many situations, their prevention is desirable. In an attempt to arrive at a rational approach to the purely prophylactic administration of anticonvulsants, existing data pertaining to four topics were examined: the danger posed by a single seizure, the incidence of seizures in a given disease state, the ability of anticonvulsant medication to prevent seizures, and the risks and benefits associated with pharmacological intervention. In general, where the risk of seizure exceeds 10 to 15% or where a single seizure may have disastrous consequences, anticonvulsant prophylaxis is recommended.

Acute cervical myelopathy from hereditary multiple exostoses: case report.

A case of hereditary multiple exostoses with acute cervical myelopathy, tetraplegia, and apnea is reported. Neurological complications as a result of osteochondromas in hereditary multiple exostoses are rare. The majority of osteochondromas in the cervical spine arise from the neural arch. Magnetic resonance imaging and computed tomography are invaluable in localizing the origin of the lesion and its relationship to the spinal cord. Decompressive laminectomy usually results in excellent functional recovery. Where significant dorsal spinal cord compression exists without neurological deficit, prophylactic decompression can be recommended.

Calvarial hemangioendothelioma with intracranial hemorrhage: case report.

A case of a hemangioendothelioma of the occipital bone that presented clinically as an acute epidural hematoma is reported. The literature regarding this rare bone tumor is reviewed. The treatment of choice seems to be wide surgical excision, but life-threatening hemorrhage may occur due to extreme tumor vascularity. The role of radiotherapy remains uncertain.

Optic nerve decompression for osteopetrosis in early childhood.

Visual failure in osteopetrosis may result from retinal degeneration or compression of the optic nerve in the narrowed optic canals. We report the evaluation and treatment of five children with osteopetrosis whose optic nerve dysfunction seems to have been related to the latter etiology. Evaluation of visual function was carried out by means of behavioral observation and flash visual evoked responses. Of six nerves evaluated both pre- and postoperatively, the visual evoked responses seemed to improve in four. Three nerves were serially evaluated without an operation, and one showed changes consistent with maturation. One nerve was evaluated with serial postoperative evoked potentials and showed no change. We conclude that surgical decompression of the optic nerve in patients with documented optic nerve dysfunction and osteopetrosis allows improvement in visual function and is, therefore, an important consideration in the evaluation and management of patients with this disease.

Cervical arachnoid cysts after craniocervical decompression for Chiari II malformations: report of three cases.

OBJECTIVE AND IMPORTANCE: We describe three cases in which ventrally situated cervical arachnoid cysts led to spinal cord or cervicomedullary compression after repeat craniocervical decompression for Chiari II malformations. CLINICAL PRESENTATION: All three patients underwent craniocervical decompression when their Chiari malformations became symptomatic. The first patient developed chronic vertiginous spells and headache and was treated with repeated craniocervical decompression procedures during several years. Seven months after undergoing her third decompression procedure, she developed severe dizzy spells, which were determined to be of brain stem origin. The second patient had a small, asymptomatic arachnoid cyst anterior to the brain stem discovered at age 6 years. After undergoing repeat craniocervical decompression for headaches 8 years after undergoing his first procedure, the patient developed severe neck pain and acute quadraparesis. A third patient underwent repeat craniocervical decompression at age 14 years for cranial nerve dysfunction. Postoperatively, he acutely developed paresis of extraocular movements and incoordination of the upper extremities. All three patients were found to have anteriorly situated arachnoid cysts compressing the brain stem and/or cervical spinal cord. INTERVENTION AND TECHNIQUE: Fenestration of the arachnoid cyst or drainage with cystoperitoneal shunting adequately treated acute brain stem or cervical spinal cord compression. All three patients had achieved satisfactory relief from their acute symptoms of neural compression at their follow-up examinations. CONCLUSION: An association between spinal arachnoid cysts and neural tube defects has previously been reported. However, the development of previously undetected spinal arachnoid cysts after craniocervical decompression was unexpected. We hypothesize that extensive craniocervical decompression may alter the cerebrospinal fluid pressure dynamics in such a way that the anterior subarachnoid space, previously compressed, may dilate. Occasionally, because of perimedullary arachnoiditis, the cerebrospinal fluid may become loculated and act as a mass. Direct fenestration or shunting may successfully treat this problem, and less extensive craniocervical decompression may avoid it.

Tuberous sclerosis: a review for the neurosurgeon.

The clinical, radiological, and pathological characteristics of tuberous sclerosis are reviewed. Neurosurgical intervention in the syndrome is discussed in light of two recently treated cases and a literature review.

Congenital supratentorial and infratentorial peripheral neurogenic tumor: a clinical, ultrastructural, and immunohistochemical study.

Congenital neoplasms of the central nervous system are extremely rare, although they have been well documented since the earliest reports from the mid-19th century. Medulloblastoma, other primitive neuroectodermal tumors, and various types of gliomas have comprised the majority of cases. This report describes a highly unusual infratentorial and supratentorial tumor presenting as a scalp mass in a neonate who experienced in utero distress. The supratentorial mass extended through a defect in the skull to the parietooccipital lobe, and the infratentorial aspect involved the 9th and 10th cranial nerves in the region of the cerebellopontine angle. A complex spindle cell neoplasm incorporating peripheral nerve sheath and vascular characteristics was further characterized by electron microscopy and immunohistochemistry. Based upon these studies, the tumor was interpreted as a congenital schwannoma with divergent vascular differentiation. The child has been tumor-free for approximately 2 years after the initial operative procedure.

Randomized clinical trials in the evaluation of surgical innovation.

Randomized clinical trials are widely accepted as the standard for evaluation of therapeutic innovation in many fields of medicine. The three basic components of such trials (concurrent comparison, random allocation, and objective observation) are designed to control four forms of bias (chronology bias, susceptibility bias, compliance bias, and observation bias) that may interfere with the interpretation of the results of a study. Only 2% of the articles evaluating therapeutic maneuvers published in the Journal of Neurosurgery have attempted to use concurrent controls. Only one of 863 such articles met the criteria for a randomized clinical trial. Reasons for underutilization of such trials in neurosurgery are discussed and suggestions for their wider use are offered.

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.

Antibiotic prophylaxis of postoperative neurosurgical wound infection.

In an effort to reduce the incidence of postoperative wound infection, the recently proposed regimen of intravenous vancomycin and tobramycin and streptomycin irrigating solution was used in 878 neurosurgical operations. There were eight infections, for an infection rate of 0.9%. This infection rate was compared to the rate in the previously reported series using a sequential statistical analysis. The infection rate was found to be significantly greater than that previously reported. Controlled clinical trials will be required before the efficacy of antibiotic prophylaxis in clean neurosurgical procedures can be considered proven.