1H MRS in acute traumatic brain injury.

The objective of this study was to demonstrate 1H MR spectroscopy (MRS) changes in cerebral metabolites after acute head trauma. Twenty-five patients (12 children, 13 adults) were examined with quantitative 1H MRS after closed head injury. Clinical grade (Glasgow Coma Scale [GCS]) and outcome (Rancho Los Amigos Medical Center Outcome Score [ROS]) were correlated with quantitative neurochemical findings.

Neural stimulation: clinical and laboratory experiences.

This is a report of some of the experiences of the author and his associates with electrical stimulation of the animal and human nervous systems. It was presented as a personal history rather than a review of recent investigations and publications concerned with safe and effective stimulation of neural tissue with the ultimate goals of developing neural prostheses. Much of the information presented herein has been published.

Hydrocephalus: overdrainage by ventricular shunts. A review and recommendations.

Selected literature review of the clinical course of patients with ventricular shunts for hydrocephalus shows that the effects of cerebrospinal fluid overdrainage are subdural hematoma, craniosynostosis, slit ventricle syndrome, and low intracranial pressure syndrome. These occur sequentially at different age groups, but approximate averages of incidence and time of occurrence after first shunt reveal an overall incidence of 10%-12% for at least one of these appearing at 6.5 years after shunting.

Development of a new implantable bio-telestimulator.

The authors describe preliminarily an implantable bio-stimulating device for stimulation of peripheral nerves and the central nervous system. The receiving unit is totally implantable. The system works on radiofrequency transcutaneous coupling across the skin.

Evaluation of electrode array material for neural prostheses.

Matrix support materials for brain surface electrodes used in neuroprosthetic applications were evaluated after chronic subdural implantation over the parietal cortex of the cat. Four types of array fabricated with Silastic, Dacron mesh, or platinum wire annuli were implanted for periods ranging from 5 weeks to 1 year. We evaluated the arrays by access resistance measurements and gross and histological observations of the tissue beneath both nonstimulated and stimulated electrodes.

Intracellular calcium deposition in brain following electrical stimulation.

The effects of electrical stimulation of the cat cerebral cortex have been evaluated by light and electron microscopy following a wide variety of stimulation parameters (QD/ph of 10 - 300 muC/cm2/ph). Platinum or rhodium disc electrode arrays were bilaterally implanted subdurally on the parietal cortex and subjected to 36-hour stimulations (9 hrs./day for 4 days).

Microsurgical cannulation of the thoracic duct in cats. Technical note.

The authors describe a new technique for the microsurgical cannulation of the thoracic duct. A small silastic tube is utilized which can be joined to a subcutaneously implanted one-way flow, CSF, Ommaya-type reservoir. Extended drainage is avoided.

Neuropathological effects of intracerebral platinum salt injections.

Multiple intracerebral injections of a mixture of platinum salts were made in 9 adult cats and the brains studied by light and electron microscopy at 5-12 days post injection. At the center of the lesions normal cortical architecture was completely replaced by edematous areas containing lipid-laden macrophages and cellular debris. The lesion periphery was characterized by perivascular edema and degenerative changes including cytoplasmic lipid inclusions and vacuolations with selective vulnerability of neurons.

Effects of electrical stimulation of brain.

The use of implantable neural prostheses activated by radiofrequency transmission requires that the materials in the device and the stimulation techniques are not injurious to neural tissue, particularly the neurons. In this report, we discuss our experiences in the search for safe stimulation techniques. Acute and chronic experiments have been performed to evaluate electrode design and materials and to observe the effects of various stimulus protocols on the blood-brain barrier and brain.

Adverse effects of electrical energy applied to the nervous system.

Neural prostheses activated by radiofrequency transmission are currently being implanted to treat a variety of clinical problems. It is essential that neither the materials used in these prostheses, particularly the electrodes, nor the stimulus parameters that are employed will cause neural damage. The experiences of investigators engaged in both the experimental laboratory and clinical studies of the effects of electrical stimulation are reported herein.

Microvascular bipolar coagulator. Technical note.

A bipolar coagulator fabricated from jeweler's forceps of various sizes is described. The unit has proved very useful in microvascular neurosurgical procedures that require high magnification.

Electrical stimulation of the brain. IV. Ultrastructural studies.

The ultrastructural response of tissues of the cat's central nervous system to chronic electrical stimulation with various parameters has been evaluated at four and a half days post stimulation. Cellular alterations included widespread cytoplasmic vacuolations, architectural derangement and disruption of plasmalemma and other membranes. Lipid inclusions and dense crystalline bodies were prominent in astrocyte-like phagocytic cells in the more severe lesions.

Electrical stimulation of the brain. III. The neural damage model.

A major concern in the use of neural prostheses is whether electrical stimualtion can cause irreversible damage to neurons. The Neural Damage Model was devised to study the problem and to provide guidlines. The cerebral cortex of cats was stimulated continuously for 36 hours with balanced, biphasic waveforms.

Electrical stimulation of the brain. II. Effects on the blood-brain barrier.

Acute and chronic studies of the effects of electrical stimulation on the blood-brain barrier (BBB) of the cat cerebral cortex are reported. The findings emphasize the importance of avoiding direct-coupled, monophasic waveforms in stimulating nervous tissue. Biphasic waveforms with balanced charges in each half-wave of the stimulating pulse can be used for up to 36 hours of continuous stimulation if the charge per phase (Q/ph) does not exceed 0.

Electrical stimulation of the brain. I. Electrodes and electrode arrays.

Investigators engaged in studying the effects of electrical stimulation on the blood-brain barrier (BBB) and brain usually find it necessary to fabricate the electrodes and electrode arrays required in their acute and chronic experiments. Techniques for fabricating spring-mounted, concentric and salt-bridge electrodes and electrode arrays are described in this report.

Electrical stimulation of the nervous system.

Twenty-seven patients with chronic pain had dorsal column stimulators implanted for pain control over a period of three years. Technical factors of electrode placement and type of unit were not found to correlate with the degree of pain relief. The preoperative psychological attitude of the patient correlated highly with the degree of pain relief and was the single most important factor in patient selection and evaluation.

Electrical stimulation of the human visual cortex; preliminary report.

A feasibility study for the development of a human visual prosthesis has led several workers to observe the effects of electrical stimulation of the human visual cortex. Experience with such stimulations of three normal-sighted patients is reported. The results confirm some of the findings of other workers, but do not show that multiple phosphenes were experienced by our patients, using strictly limited parameters of stimulation.