Leonard I. Malis

Prevention of neurosurgical infection by intraoperative antibiotics.

For the past 5 years at Mount Sinai Hospital, an intraoperative prophylactic antibiotic regime consisting of intramuscular gentamicin or tobramycin, intravenous vancomycin, and streptomycin irrigating solution, with no preoperative or post operative antibiotics, has provided complete protection against operative infections in neurological surgery. There have been 1732 major clean operative cases with no instance of operative infection and no complication due to the antibiotics.

New Trends in Microsurgery and Applied Technology

I shall begin with a bit of the history before going on to what is new. Actually, Professor Yasargil and I did a bit of discussing since we speak together on the same topic and decided on how to divide it up. Since I am older than he is, I took the history.

Instrumentation for Microvascular Neurosurgery

In the macrosurgical field it has been a tradition to develop instruments empirically, almost as an art form. These instruments have then been modified by their users over a period of time, with some being improved and some devalued. A number pass through this process of evolutionary development and become universally accepted. Such an instrument is the Leksell rongeur, for which I developed a special affection more than 20 years ago. It is a virtually perfect hand tool, combining all the attributes of adaptive engineering plus a unique artistic grace.

Titanium Mesh and Acrylic Cranioplasty

Since June 1985 100 cranioplasties have been carried out using titanium mesh and acrylic. There have been no complications and no infections. Titanium mesh is virtually radiolucent. Titanium is nonmagnetic and is the most biocompatible metal known.

Application of phase spectral analysis for brain stem auditory evoked potential detection in normal subjects and patients with posterior fossa tumors.

A statistical test of the brain stem auditory-evoked potential (BAEP) detection is presented. The data were collected by averaging groups of 200 sweeps in order to obtain a set of group averages. The synchrony measure (SM), which represents the degree of reproducibility for group averages, is used as a statistical measure and is calculated from the phase variance for selected Fourier components of the group averages. The sensitivity of the test was demonstrated on 375 normal BAEPs with different stimulus intensities (45, 60, 75 dB SL) from both the ipsilateral and contralateral recordings, and on 82 BAEP recordings in the absence of stimulus. In all 375 cases of normal BAEPs the SM exceeds the threshold level while in the absence of stimulation the SM was below the threshold level. The clinical usefulness of the test was demonstrated on 22 patients with tumors of the posterior fossa. The absence of the BAEP was detected in 21 patients. In 12 out of 13 patients with lateralized tumors (acoustic neuromas), absence of the BAEP was noted for stimulation of the affected ear.

Computed tomography of intraspinal and paraspinal neoplasms.

Computed tomography (CT) has been used in the evaluation of 36 spinal neoplasms. Eleven of the 19 intraspinal and all of the 17 paraspinal tumors showed positive CT images. Computed tomography is of diagnostic value particularly in detecting calcified meningiomas. lipomas, and neurofi-bromas with bony changes. The size of the paraspinal tumors and the degree of bone destruction can be precisely demonstrated by CT.

An electrophysiological study of the superior colliculus and visual cortex

Abstract In cats anesthetized with Nembutal, simultaneous recording of evoked potentials from superior colliculus and visual cortex to single light flashes gave mean onset latencies of 36.5 msec in the former and 27 msec in the latter. Onset latency to electric stimulation of optic nerve was 8 msec in colliculus and over 1 msec in cortex. Since similar latency differences were obtained from colliculus and cortex.to both retinal (photic) and postretinal (electric) stimulation, latency differences were attributed to slower conduction in the retinocollicular pathway. The thresholds were higher in superior colliculus than visual cortex to light flashes of short duration or low intensity, or electric pulses applied to the optic nerves. Simultaneously recorded collicular and cortical evoked potentials differed from each other in shape, duration, and several other respects. With microelectrodes, three functionally differentiated layers of the superior colliculus were distinguished: a dorsal layer in which evoked potentials and single units responding to optic stimuli were obtained; an intermediate layer in which evoked potentials of unchanged amplitude, but no driven units, were recorded; and a ventral layer in which evoked potentials were greatly reduced, and where only “spontaneously” discharging units were found. The optically driven units were classified as those firing with short latency, with long latency, to light-on only, to light-on and light-off, and those inhibited by photic or optic nerve stimuli.

Compression of Spinal Cord and Cauda Equina in Achondroplastic Dwarfs

THE PURPOSE of this report is to draw attention to the neurologic abnormalities in achondroplastic dwarfs caused by protruding intervertebral disks compressing the spinal cord and cauda equina. Our recent experience in observing and treating an achondroplastic girl, 15 years of age with symptoms of a progressive myeloradiculopathy in the upper lumbar region of the spine, will be described. The only other child reported in t h i s category was noted briefly by Spillanel who mentioned Poynton’s patient, a boy of 1.5 who began to develop signs of spastic paraplegia at age 13. The clinical findings are reviewed and the results of myelographic examination of the entire spinal canal illustrated in detail. The pathologic anatomy as it relates to disturbances in neurologic function is summarized in order to provide a more comprehensive understanding of the problem. Therapeutic measures are limited, and surgical decompression is the only effective treatment if camed out early in the course of the disease before irreversible changes occur.

Intracarotid dehydrocholate infusion: a new method for prolonged reversible blood-brain barrier disruption.

An animal model for prolonged reversible blood-brain barrier (BBB) disruption has been developed. The external carotid arteries of Osborn-Mendel rats were catheterized in a retrograde manner. Varying concentrations of sodium dehydrocholate were infused into the internal carotid artery by this technique. BBB disruption was evaluated qualitatively by the appearance in the infused hemisphere of the systemically administered dyes Evans blue and sodium fluorescein and quantitatively by the ratio of counts of the technetium-labeled chelate of diethylenetriaminepentaacetic acid (99mTc-DTPA) in the infused to the noninfused hemisphere. The ability of sodium dehydrocholate to disrupt the BBB was documented with all three markers. As the concentration of the infused dehydrocholate was increased, both the incidence and the degree of BBB disruption increased. Reversibility of BBB disruption was evaluated by the administration of sodium fluorescein and 99mTc-DTPA at varying times after BBB disruption. Depending on the concentration of the infused sodium dehydrocholate, altered BBB permeability can be maintained for over 3 days. This new model of prolonged reversible BBB disruption deserves further investigation both for basic studies of the BBB and for therapeutic studies of drug delivery into the central nervous system.

The Myelography Examination of the Foramen Magnum

The clinical diagnosis of benign tumors in the region of the foramen magnum is often extremely difficult (2, 5, 8). Even if such a lesion is suspected, a satisfactory diagnosis may not be possible without roentgenologic evidence. In the presence of extradural malignant lesions, bone changes are generally detectable. The benign intradural tumors usually show no alterations on regular x-ray films, though a small proportion may exhibit thinning of one side of the arch of the atlas or ballooning of a cervical intervertebral foramen. Since these lesions may produce severe neurologic damage before complete spinal block appears, an accurate and safe method of confirming the diagnosis at an early stage has been a primary need. This appears to have been met by the development of the myelographic technic. Myelographic examination of the foramen magnum presents some special difficulties as well as special requirements. In this region lesions are easily missed; yet even minor changes can be readily appreciated with a...