✓ Spontaneous dissection of the internal carotid arteries, including those dissections resulting in total occlusion, may be a spontaneously reversible process. A patient who had angiographic evidence of bilateral complete internal carotid artery occlusions of different ages of onset illustrates this process. This case suggests certain considerations regarding the pathogenesis of these dissections.
Joseph F. Cusick and David Daniels
Joseph F. Cusick, Senichiro Komacki and Hongyung Choi
✓ The authors report a case in which glioblastoma multiforme was intimately associated with a surgical anastomosis of the superficial temporal artery to a branch of the middle cerebral artery.
Joseph F. Cusick, Khang-Cheng Ho and Jay F. Schamberg
✓ Subarachnoid hemorrhage is a frequent finding in patients who have incurred neurological complications following chymopapain chemonucleolysis, but the basis for this occurrence remains controversial. The authors report the clinical and postmortem findings in a 42-year-old man who died 5 days after chemonucleolysis at the L4–5 and L5–S1 disc spaces. The predominant histological abnormality was a severe inflammatory arteritis of a medium-sized artery at the upper cervical level with disruption of the vessel wall. The potential causative role of chymopapain in this situation and the correlation of a vascular basis for many of the complications found after inadvertent intrathecal chymopapain injection are discussed.
Paul D. Dernbach, Joel B. Myklebust and Joseph F. Cusick
✓ Artery-to-artery microvascular anastomosis (MVA) has become an established therapeutic alternative for patients with giant intracranial aneurysms and other forms of cerebrovascular disease. Many patients afflicted with cerebrovascular disease also suffer from hypertension. To evaluate the effect of hypertension on healing of small arteries following MVA, 36 spontaneously hypertensive rats were subjected to end-to-side MVA of their common carotid arteries. At specific times after surgery the rats were sacrificed; the anastomotic site was removed and examined with light microscopy and scanning electron microscopy. All MVA's were patent, and there was no evidence of thrombus formation or stenosis at the operative site in any group. Also, there was no difference between the spontaneously hypertensive rats and the control normotensive rat group in the rate of endothelial coverage of the MVA. The presence of hypertension appears to have no effect on healing of small arteries in the rat.
Joseph F. Cusick, James J. Ackmann and Sanford J. Larson
✓ The role of the dentate ligaments in the pathogenesis of myelopathy secondary to disease conditions that alter the normal biomechanics of the spinal canal was studied in 14 dogs. The effects of posterior cord elevation on somatosensory evoked potentials (SSEP's) and tension requirements were compared before and after dentate ligament section in acute experiments. At levels of posterior elevation usually within the confines of the canine canal, the dentate ligaments were the most significant element increasing tension requirements and SSEP alterations. Human cadaver studies also showed an approximate 50% reduction of force after dentatotomy. These findings suggest that after dentate ligament section the applied tension is distributed over a longer segment of the cord with a reduction in tension and disruption of axonal conduction at the level at which the force was applied.
Joseph F. Cusick, Narayan Yoganandan, Frank A. Pintar and John M. Reinartz
✓ Compromise of the functional integrity of the posterior lumbar ligaments and facet joints is a common occurrence after repeated lumbar operative procedures. To evaluate the biomechanical effects of sequential surgical alterations, this investigation analyzed bilateral facetectomies (medial, total, and total with posterior ligament section) in three segments of human cadaveric lumbar spines under increasing compression-flexion. These iatrogenic alterations, designed to replicate common methods of surgical exposure, were created at the lower intervertebral joint (L4–5) while the upper joint (L3–4) remained intact. Overall strength characteristics in the physiological range of 400 N and 600 N demonstrated significant differences (p < 0.05) in applied compressions for all preparations compared to the intact specimen. Comparison of sequential surgeries, however, did not demonstrate this tendency. Significant changes in the movement of the spinous processes at the upper (unaltered) level occurred only after posterior ligament section, whereas the lower (altered) level showed markedly increasing distraction of both the facets and the spinous processes with sequential operations. Sectioning of the supraspinous/interspinous ligament and associated fascial attachments resulted in a marked transfer of motion to the altered level. This was manifested by the increased anterior displacement of the centrode at the lower level associated with probable posterior migration of the centrode at the upper level. These data suggest that the effects of progressive surgical alterations of the lumbar facet joints are controllable in a preparation undergoing acute compression-flexion loads until the supraspinous/interspinous ligaments, with associated residual tendinous, midline muscle, and fascial attachments, are violated.
Joseph F. Cusick, Joel Myklebust, Mark Zyvoloski, Anthony Sances Jr., Chris Houterman and Sanford J. Larson
✓ Experiments were performed to assess the effects of vertebral column distraction on evoked potential responses from multiple recording sites along the conducting pathway in the monkey, and on concurrent blood flows, measured with the radioactive microsphere technique, along the axis of the central nervous system. Linear distractive loads were applied until the amplitude of the evoked response was significantly reduced. In four monkeys, the loads (100 to 150 lb) were sustained, whereas in two monkeys the forces (80 to 110 lb) were relaxed. The earliest response changes were most marked in recordings dependent upon the integrity of the upper cervical dorsal columns or brain stem-lemniscal pathway. The responses returned to control levels with load relaxation, but maintenance of the tractive load produced generalized and progressive response attenuation. At selected periods of significant changes in the evoked potential response, blood flow remained stable except for the late onset of regional ischemia in the middle cervical through upper thoracic spinal cord levels in the animals undergoing sustained loads. These findings indicate that brain-stem or spinal cord dysfunction occurring with both acute and gradual elongation of the spinal canal are the result of excess tensile stress acting on fiber tracts, and the delayed onset of spinal cord ischemia is the probable result of a similar mechanical process acting upon intrinsic spinal cord blood vessels.
Joseph F. Cusick, Khang-Cheng Ho, Thad C. Hagen and Larry E. Kun
✓ Granular-cell pituicytomas of the neurohypophysis have a controversial histogenesis and oncological behavior. The occurrence of such a tumor in a patient whose father and daughter had endocrine neoplasms suggests a neuroectodermal origin for these tumors. Although all of the conditions considered in this report are unusual clinical entities, their correlation offers considerations in understanding the importance of genetic factors in tumor development.
Joseph F. Cusick, Joel Myklebust, Sanford J. Larson and Anthony Sances Jr.
✓ Summated responses evoked by peripheral nerve stimulation were recorded from electrodes located in the epidural and subdural spaces anterior and posterior to the monkey spinal cord. Segmental microsurgical resection of the dorsal columns both at the thoracic and cervical levels resulted in total obliteration of the response recorded rostral to these lesions. Isolated segmental dorsal column preservation did not significantly alter response latency or wave form recorded at the rostral electrodes. Bilateral cervical dorsolateral column resection also resulted in no discernible alterations of these responses. These data indicate that spinal evoked potentials recorded from levels rostral to their root entry zones arise almost exclusively from the dorsal columns.