Walter J. Levy

Chiari Malformation Presenting in Adults: A Surgical Experience in 127 Cases

We reviewed 127 patients who were operated upon for adult presentation Chiari malformation and made six conclusions: (a) The clinical examination remains crucial in the diagnosis. (b) The surgical anatomy is highly varied. (c) Syrinxes can be missed on preoperative contrast studies. (d) By a conservative grading system, we determined that 46% of the patients improved during long term follow-up. One-quarter deteriorated over the long run in spite of any treatment. (e) The overall results did not differ whether the treatment was plugging of the central canal plus decompression or decompression alone. (f) In patients with progression, plugging of the central canal obtained superior results. A review of the literature shows that the natural history of this complex disease process has not been established. This history is needed to identify the course of what may be several important factors that lead to the pathological condition in this disease.

Motor Evoked Potentials from Transcranial Stimulation of the Motor Cortex in Humans

Electrical testing of central nervous system pathways is assuming increasing importance in clinical medicine. However, there is no direct monitor of the motor system. We previously reported using a motor evoked potential created by direct excitation of the spinal cord, placing a stimulating electrode over the corticospinal tract area. To produce a less invasive test, we now use direct transcranial stimulation of the motor cortex through the scalp or direct stimulation of the motor cortex itself during operation. A descending signal can be recorded over the spinal cord and in the peripheral nerves where no retrograde sensory signals should be able to descend. This motor cortex stimulation produces contralateral limb movements and selective activation of the peripheral nerves of a limb. The characteristics of this signal are similar to those described in the neurophysiological literature for a descending motor signal. With a depth electrode, it was found that the signal was strongest in the spinal cord near the corticospinal tracts and in the anterior horn cell area. A set of lesioning studies showed that most of the signal travels in the area of the corticospinal tract, with some traveling in the ventral portion of the spinal cord, perhaps in the anterior corticospinal tract. Section of the pyramid essentially abolishes the signal, but lesioning of the red nucleus does not. This test offers an electrical assessment of the motor system that can be useful in experimental work on spinal cord and brain function. It has potential clinical applicability in humans.

Spinal Neurofibromas: A Report of 66 Cases and a Comparison with Meningiomas

A series of 66 spinal cord neurofibromas was analyzed for history, signs, surgical approach, and outcome. The tumors presented primarily with sensory symptoms. Plain films were abnormal in 1/2 of cases and 1/2 had a complete block. They were primarily intradural, and primarily thoracic. A conservative exam system was used for follow-up and 85% with pain had complete relief; 50% with motor loss had normal motor function, and 88% had normal sensation who had prior sensory loss. In comparison to meningiomas, the principal differences were that neurofibromas had an even sex distribution, a lower incidence of cord signs and symptoms, more frequent findings on plain x-rays, and higher cerebrospinal fluid protein. Surgical outcome was similar. Sacrifice of the involved root during removal usually did not produce a deficit. The series is compared with a similar series of meningiomas from the same institution over the same time period.

Needle biopsy of intrancranial lesions guided by computerized tomography.

Biopsies can be performed directly with computerized tomography (CT) head scanners with some difficulty. The small scanning orifice does not allow enough room for needle placement; therefore, biopsy is difficult. In contrast, the scanning orifice of the CT body scanner is large enough to permit biopsies without hindrance. Over 300 CT-guided abdominal biopsy procedures have been performed at the Cleveland Clinic Foundation. We are reporting the technique and the results of 14 CT-guided brain biopsies. There were no complications in the series and an accurate diagnosis was made for 13 of the 14 patients.

Primary Malignant Nerve Sheath Tumor of the Gasserian Ganglion: A Report of Two Cases

Primary tumors of the gasserian ganglion are usually benign, and secondary tumors are malignant. We report two cases of a malignant primary tumor of the gasserian ganglion, bringing the total in the world literature to five. The presentation, etiological features, and treatment of these cases are reviewed, together with a review of the literature. Preoperative differentiation from a benign tumor is not possible with certainty. A combination of operation and radiation therapy seems to be the best treatment at present.

Signal-processing characteristics of differential-interference-contrast microscopy

A mathematical model based on the methods of Fourier optics is presented as a description of the signalprocessing characteristics of differential-interference-contrast microscopy. A computerized simulation of this signal processing is described, and some images of abstract objects generated by this simulation are presented. This model and its simulation have implications on the feasibility of image restoration with superresolution by way of differential-interference-contrast microscopy under the classical constraints of finite object size and non-negativity. Such implications are discussed, and the encouraging results of a study into such feasibility are shown.

Encouraging surgical results in walking patients with epidural metastases

The management of epidural metastases is in a state of controversy between combined surgical and radiation treatment and treatment by radiation alone. Review of the literature shows that one group, patients who are ambulatory before treatment, have been studied rarely. We analyzed our last 15 years of experience at the Cleveland Clinic and found 39 patients who were ambulatory preoperatively; 84% of these walked during the short term follow-up and 93% of the 1-year survivors walked. These data suggest that surgery has an important role in the management of ambulatory patients.

Unusual problems for the physician in managing a hospital patient who received a malicious insulin overdose.

A patient recovering normally from a biopsy and subtotal removal of a malignant brain tumor became severely hypoglycemic on the ward and died. The differential diagnosis eliminated disease as a possible cause, and medication error on the floor was also ruled out. Deliberate administration of a massive dose of insulin intravenously seemed to be the only alternative. A careful investigation supported the likelihood of a criminal act. The patients wife came under suspicion and was subsequently arrested, charged with murder, and convicted. This sequence of events created three problems that fell outside of our normal professional training and experience as physicians. First, we were slow to suspect foul play in our search for an unusual cause. Second, the steps taken to protect the patient against further risk without denying reasonable rights to family or arousing the suspects suspicions needed strengthening. Third, even though the occurrence of these events in a hospital allowed an unusual degree of evidence documenting the allegations to be accumulated, key parts of the evidence could not be used. The routine hospital handling of laboratory tests critical to support of the accusations was not sufficient to meet the demands of the legal system, which has its own criteria. We discuss the issues in managing these problems.

Comparison of laser and radiofrequency dorsal root entry zone lesions in cats

Dorsal root entry zone lesions are effective in the control of intractable pain in several types of spinal cord injuries. Traditionally, these lesions have been made with the radiofrequency technique. This is effective, but has the drawback of being laborious, and there is a significant incidence of permanent weakness. We have evaluated the carbon dioxide laser, hoping that it would be both faster and more controlled, thereby offering the chance to lower the complication rate. In comparing a parallel series of radiofrequency and laser dorsal root entry zone lesions along the cats spinal cord, we observed that the radiofrequency lesion was larger. In addition, it had 3 times more variability in its size than the laser lesion. We attribute this in part to the nature of the laser in making a very precise and reproducible lesion. Second, the extremely brief pulse of the laser, a fraction of a second, means that movement of the spinal cord from respiration and heartbeat and movement of the surgical instrument from the surgeons hand become far less important in inducing lesion variability. We also studied for 2 months a series of chronic cats; there were no complications due to the laser. This work suggests that the laser is a useful instrument for dorsal root entry zone lesions, but requires more precise aiming and focusing.

Nonpyramidal motor activation produced by stimulation of the cerebellum, direct or transcranial: a cerebellar evoked potential.

There is a need to monitor the functional status of the motor pathways well enough to predict the state of that function during operations and in injured or diseased patients. We previously reported that a motor evoked potential (MEP) can be produced by direct or transcranial stimulation of the motor cortex in both cats and humans. This signal descends through both the dorsolateral and ventral spinal cord and is primarily localized in the pyramidal tracts, producing a peripheral nerve signal and an electromyogram (EMG) response. It is more sensitive to injury than the somatosensory evoked potential (SEP). We report here that one can stimulate the cerebellar cortex, either directly or transcranially, and produce a descending signal in the spinal cord that has different characteristics from the MEP. The cerebellar evoked potential (CEP), located in the dorsolateral and the ventral cord, has an earlier latency and a faster conduction velocity than the MEP. It is predominantly ipsilateral with some contralateral components and also produces EMG responses. In the peripheral nerves, the CEP often produces a pattern of several waves that is different from the one or two predominant contralateral waves of the MEP. The CEP is not diminished by pyramidotomy. It arises from two sites on the cerebellar cortex, medial and lateral. The pathways activated may be the vestibulospinal, rubrospinal, reticulospinal, and fastigiospinal systems. This test seems to offer a monitor of selected motor pathways in the spinal cord largely separate from and complementary to the MEP. The ventral pathways activated probably include those demonstrated to be most essential to basic ambulation after spinal cord injury in primates. Also of importance, one type of evoked potential can facilitate another, which provides additional diagnostic tests. The CEP should be of investigative and clinical value.