Microsurgical anatomy of the dorsal cervical nerve roots and the cervical dorsal root ganglion/ventral root complexes.

BACKGROUND: It is known that a "dissociated motor loss" of the deltoid muscle can occur with disconcerting frequency after cervical spine surgery. The etiology of this entity is in question. We conducted an anatomic study to identify anatomic factors that might predispose C5 to injury. METHODS: We studied 128 dorsal cervical nerves and root ganglion/ventral root complexes in 10 adult cadavers. At each cervical level the following data were recorded: number of rootlets, range of width of rootlets, length of DREZ, cranial angles of the superior and inferior rootlets with the spinal cord, length of the superior and inferior rootlets, dimensions of the foramina, dimensions of the dorsal root, dimensions of the dorsal root ganglion (DRG)/ventral root (VR) complex, and the blood supply to the DRG. The histology at the site of compression was also examined. Statistical analysis was conducted using the single factor-repeated measures analysis of variance. RESULTS: We found that, 1) the C5 superior dorsal rootlets angle less inferiorly from the cervical cord than the other dorsal cervical roots (p=0.001), 2) the majority of the DRG/VR complexes from C3 to C6 were compressed by the vertebral artery (73%), 3) the C5 DRG/VR complex was compressed to the greatest extent (77.6%, p=0.3519), and 4) the ganglionic artery was more frequent at C4, C5, and C6. CONCLUSION: To our knowledge, the second finding has not been reported previously. The first and third findings may help explain why C5 is more vulnerable to injury.

Histologic effects of collagen-filled interlocking detachable coils in the ablation of experimental aneurysms in swine.

PURPOSE: To assess the histologic changes produced by platinum microcoils with an inner core of cross-linked bovine collagen in experimentally induced aneurysms in swine, and to assess the feasibility of the system for the delivery of the collagen. METHODS: Bilateral pouch aneurysms were created in the side wall of the common carotid artery in seven barnyard pigs. Eight aneurysms were treated with coils designed with an interlocking detachment mechanism: in four of these, the coils had an inner core of collagen; in the other four, the platinum microcoils had a similar design but without the collagen mandrel. The packing density of the coils within the aneurysm was approximately the same for both types of coils. The other six aneurysms were left untreated and served as controls. Angiograms were obtained at the time of treatment (2 weeks after the aneurysms were created) and at 1, 4, and 8 weeks after treatment. All animals were killed 8 weeks after the treatment (10 weeks after the aneurysms were created). Arteries and aneurysms were resected en bloc and fixed for histopathologic study. RESULTS: The interlocking detachment mechanism worked well. Little difference was noted between the two types of coils in their ability to effect complete aneurysmal thrombosis (three of four aneurysms treated with collagen-core coils and two of four aneurysms treated with conventional coils). The collagen-core coils stimulated new collagen formation in areas proximal to the coils, and more fibroblasts were noted near the collagen-core coils than near the conventional coils. CONCLUSION: Local fibroblast proliferation and collagen production were stimulated by heterologous cross-linked collagen embedded in micro-coils in this experimental model. Such biologic stimulation holds promise for improving the endovascular cure rate of aneurysms in humans.

The microsurgical anatomy of the superior hypophyseal artery.

Interest in the anatomy of the proximal segment of the intracranial internal carotid artery has been kindled by the recognition that there are multiple potential sites of aneurysm formation in this region. These various aneurysm locations have characteristic hemodynamic and clinical features as well as surgical considerations. Recently recognized as a distinct clinical and anatomical entity are aneurysms that are hemodynamically related to the superior hypophyseal artery. Although aneurysms arising in proximity to the superior hypophyseal artery are not rare, the anatomy of this vessel arising from the medial or posteromedial aspect of the proximal internal carotid artery is poorly understood. We performed a cadaveric microsurgical anatomical study of 20 internal carotid arteries between the ophthalmic and posterior communicating arteries to develop a better understanding of the anatomical relationships of the superior hypophyseal artery. There were an average of 1.8 superior hypophyseal arteries arising from each carotid artery with an average diameter of 0.22 mm. The origin of the superior hypophyseal arteries was within 5 mm of the ophthalmic artery origin in 85% of the specimens. There were two distinct patterns of superior hypophyseal artery anatomy. In 42%, a large, dominant superior hypophyseal artery branched like a candelabra with smaller branches to the pituitary stalk, optic nerve, and chiasm. The average diameter of the larger branches was 0.3 mm. In the absence of a large dominant branch, two or three medial vessels were found. In one specimen, an incidental aneurysm was discovered at the origin of the superior hypophyseal artery on the medial aspect of the internal carotid artery at the origin of a large candelabra-like branch.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of myocardial infarct size by poloxamer 188 and mannitol in a canine model.

Poloxamer 188 has been reported to inhibit thrombosis, decrease whole blood viscosity, and improve perfusion of damaged tissue. Mannitol has free radical scavenging capabilities that might contribute to myocardial salvage after ischemia. Because these agents appear to work in different ways, we studied their cardioprotective properties when they were used separately and in combination. After 75 minutes of left anterior descending coronary artery (LAD) occlusion, dogs received poloxamer 188 (48 mg/kg), mannitol (0.5 gm/kg), or both intravenously during an additional 15 minutes of LAD occlusion and for 45 minutes of reperfusion, whereas control dogs received an equal volume of saline solution. After surgery the animals were maintained for 24 hours and then killed. Areas of myocardial infarction (MI) and risk of infarction (R) were calculated by means of planimetric analysis of slices of myocardium stained with 1.5% triphenyltetrazolium and 0.5% Evans blue dye. The ratio of MI/R (mean +/- standard error of the mean) were: control, 25.6 +/- 1.8% (n = 10); poloxamer 188, 12.7 +/- 2.0% (n = 10); mannitol, 10.6 +/- 2.5% (n = 11); and poloxamer 188 plus mannitol, 8.0 +/- 4.1% (n = 10). Measurement of microvascular blood flow indicated a similar 86% to 91% reduction of blood flow to the area at risk in all treatment groups. Consequently both poloxamer 188 and mannitol appear to increase salvage of ischemic myocardium and a combination of the two may be more effective than either agent alone.