The history of the neurosurgical engine.

The opening of the skull of a living human being dates back to early civilization. The procedure may have been performed as early as the Neolithic period. Surgeons have continued to search for a better, easier, quicker, and safer method to open the skull. Today, most neurosurgeons are well acquainted with the surgical drill; however, few are familiar with the development of this instrument from its beginnings in dentistry to its use in modern neurosurgery. As cerebral localization advanced in the late 19th century, so, too, did the demands for better techniques for entering the cranial cavity and exposing more extensive areas of the brain. Mechanical devices began to appear in operating theaters throughout the world. Despite the enthusiasm of its inventors, the surgical engine was used by but a few pioneer cranial surgeons. The use of a surgical engine in the operating room has become commonplace. Its presence continues to demand respect. There is no doubt that this instrument has helped advance neurosurgery. Its development and refinement are rich in history and closely parallel the development of modern neurosurgery.

Positron emission tomography in the detection of malignant degeneration of low-grade gliomas.

The management of low-grade gliomas represents a challenge to the physician as a significant proportion may undergo malignant degeneration to a high-grade tumor. We present the positron emission tomography (PET) scans, using [18F] fluorodeoxyglucose (FDG), of 12 patients who have histological and/or clinical evidence of malignant degeneration of a low-grade glioma. Each scan displays a focal area of hypermetabolism similar to that of malignant gliomas which arise de novo. Three patients also underwent PET scanning prior to malignant degeneration. When the initial scan is compared with the postmalignant degeneration study, a difference in tumoral glucose uptake can be recognized. A region previously shown to be hypometabolic develops focal hypermetabolism as malignant changes evolve. This study displays the utility of FDG-PET in the evaluation of malignant degeneration of low-grade gliomas. The knowledge that a neoplasm has altered its biological behavior may influence subsequent therapeutic options. If these findings can be confirmed in larger series and by other investigators, it is possible that FDG-PET may be adopted as one of the diagnostic tools for guiding the management of low-grade gliomas.

Updated assessment and current classification of spinal meningeal cysts.

The classification of spinal meningeal cysts (MC's) in the literature is indistinct, confusing, and in certain categories histologically misleading. Based on a series of 22 cases, the authors propose a classification comprising three categories: spinal extradural MC's without spinal nerve root fibers (Type I); spinal extradural MC's with spinal nerve root fibers (Type II); and spinal intradural MC's (Type III). Although water-soluble myelography may disclose a filling defect for all three categories, computerized tomographic myelography (CTM) is essential to reveal communication between the cyst and the subarachnoid space. Communication demonstrated by CTM allows accurate diagnosis of a spinal MC and rules out other mass lesions. Magnetic resonance imaging appears useful as an initial study to identify an intraspinal cystic mass. Final characterization is based on operative inspection and histological examination for all three categories.

MR imaging of thoracic disk herniations.

Magnetic resonance (MR) is of value in imaging intervertebral disk disease. We present the MR findings in two patients with thoracic disk herniations who required surgical intervention. The advantages of MR over CT myelography are ease of obtaining sagittal sections, rapid assessment of the entire thoracic spine, and a high rate of patient acceptance related to the noninvasive nature of MR and lack of morbidity and complications. For these reasons, we currently rely, almost exclusively, on MR for evaluating thoracic disk disease.

Glucose utilization by intracranial meningiomas as an index of tumor aggressivity and probability of recurrence: a PET study.

Seventeen patients with intracranial meningiomas were studied with positron emission tomography and fluorine-18-2-fluorodeoxyglucose (PET-FDG) to assess the glucose utilization of these tumors. Four meningiomas followed for 3-5 years after PET-FDG and surgery showed no evidence of recurrence. These tumors had significantly lower glucose utilization rates (1.9 mg/dl/min +/- 1.0) than 11 recurrent or regrowing meningiomas (4.5 mg/dl/min +/- 1.96) (P less than .01). The glucose metabolic rates of meningiomas correlated with tumor growth, as estimated from changes in tumor size on repeated computed tomographic scans. Histopathologically, a syncytial (atypical) meningioma had the highest glucose utilization rate, followed by a papillary meningioma and an angioblastic meningioma. Individual transitional and syncytial (typical) meningiomas showed marked differences in glucose metabolism despite similar microscopic appearance. Glucose utilization rate appears to be at least as reliable as histologic classification and other proposed criteria for predicting the behavior and recurrence of intracranial meningiomas.

Treatment of delayed radiation necrosis of the brain. A clinical observation.

The authors report two cases of delayed radiation necrosis of the brain. In these cases a dramatic clinical and computerized tomographic improvement was noted after the institution of anticoagulant therapy. Based on a review of the literature, a possible causal mechanism is suggested. It was believed from both the clinical observation and the literature review that the anticoagulant agents had a direct effect upon the improvement in these patients. Laboratory data are needed to determine the role of anticoagulant therapy in the treatment of delayed radiation necrosis of the brain.

The cutting-edge microvascular needle. A scanning electron microscopic study.

The authors have compared the vascular endothelial damage caused by blunt-tipped microvascular needles as reported previously with that of sharp cutting-edged needles of comparable size. The same four distinct vascular lesions were found with cutting-edged needles as with the blunt-tipped needles. Even though one experimenter made all of the lesions, and all of the tissue was handled in the same fashion, there was much variation in the extent of the intimal damage. Overall, cutting-edged needles produced slightly less intimal tearing and platelet aggregation than blunt-tipped needles, but the difference was not striking.

Work in progress: [18F] fluorodeoxyglucose and positron emission tomography in the evaluation of radiation necrosis of the brain.

Five patients who had undergone radiation therapy for cerebral tumors and whose conditions were deteriorating were examined by means of positron emission tomography (PET) with [18F] fluorodeoxyglucose. All five cases had similar clinical and computed tomographic findings. Using the PET technique the two cases of radiation necrosis were distinguished from the three recurrent tumors. In the two cases of radiation necrosis the rate of glucose utilization in the lesion was markedly reduced compared with the normal brain parenchyma. In the recurrent gliomas, however, the glucose metabolic rate was elevated. All five diagnoses were confirmed by biopsy or autopsy.

Multiple abscesses of the brain. Case report.

A case of multiple brain abscesses is presented. The patient was treated with systemic antibiotics; one of the lesions acutely increased in size, became life-threatening, and was surgically removed. The patient continued with antibiotic treatment, and the remaining brain abscesses completely disappeared. Recent followup review almost 2 years after diagnosis demonstrated no evidence of recurrence.

Effects of progressive hypoxia on long tract neural conduction in the spinal cord.

In this experiment, the vulnerability of long tract neural conduction in the spinal cord to progressive hypoxia was studied. The physiological integrity of nonsynaptic spinal cord conduction was monitored with the spinal evoked response (SER). Focal spinal cord blood flow was measured with the hydrogen clearance method. Progressive hypoxia was created by progressively increasing the amount of nitrogen in the inspired gas mixture. The SER was seen to fail only after extended periods of severe hypoxia. Multisynaptic cerebral condition monitored by the cerebral evoked response (CER) seemed more sensitive in the three animals in which both SER and CER were recorded. Spinal cord blood flow (SCBF) was not affected by progressive hypoxia until the PO2 was below 40 torr, and then the SCBF rose dramatically with further progression of the hypoxia.

Scanning electron micrographic study of vascular lesions caused by microvascular needles and suture.

The authors studied the damage to blood vessels 1 to 2 mm in diameter caused by the most commonly used types of microvascular needle. Excluding variables introduced by anastomosis, the study focused specifically on lesions attributable only to the needle and suture. Scanning electron microscopy revealed four distinct types of lesion. A theory is proposed to explain the mechanisms whereby these lesions were produced, and a needle design is recommended that may aid in minimizing vascular trauma.

Relative vulnerability of the brain and spinal cord to ischemia.

In this experiment CER and SER were monitored as blood flow was progressively lowered by lowering the systemic arterial pressure below the lower limits of autoregulation (bleeding). Blood flow in the brain and dorsal column of the spinal cord was monitored and recorded with the hydrogen clearance method. Long tract neural conduction in the spinal cord appeared quite refractory to the effects of ischemia and disappeared only after 8--18 min of essentially absolute ischemia. The CER was more sensitive to the effects of ischemia, disappearing first in one animal and returning later in all of the animals. The SER returned in all animals after re-infusion of the blood and re-establishment of the blood flow even after a 13--23 min period of absolute ischemia and a 5 min period of electrical silence.

Cardiac arrhythmias accompanying acute compression of the spinal cord.

This study was undertaken to determine the cardiovascular response to compression of the spinal cord and to determine the autonomic mechanisms involved. The electrocardiogram and arterial blood pressure were recorded in anesthetized monkeys during inflation of a balloon catheter in the epidural space of the mid-thoracic region. Acute spinal cord compression resulted in a wide variety of severe cardiac arrhythmias and acute hypertension. The arrhythmias were found to result from hyperactivity of both the sympathetic and parasympathetic divisions of the autonomic nervous system.

Experimental acute balloon compression of the spinal cord. Factors affecting disappearance and return of the spinal evoked response.

Acute balloon compression of the thoracic spinal cord for 15, 7, 5, 3, and 1 minute in monkeys caused immediate disappearance of the spinal evoked response and complete focal ischemia of the compressed segment in all animals. Only the animals in the 1-minute group, however, demonstrated return of the evoked response. These data, coupled with data from previous experiments of slow balloon compression of the spinal cord and spinal cord ischemia, suggest that the major pathological substrate for neural dysfunction after balloon compression of the spinal cord, be it acute or slow, is physical injury of the neural membrane, irrespective of blood flow changes. These findings also suggest that the ability of that membrane to recover is related to rapidity and length of time of compression. Focal changes in blood flow do not appear to be significant in this mechanism.