Surgical treatment of osteophytes and calcified discs of the cervical spine.

There are many options available for the surgical treatment of cervical spondylotic radiculopathy and cervical spondylotic myelopathy, with advantages and disadvantages to each. We have presented our approach to this clinical syndrome and the surgical techniques we prefer for each of its variants. Good, objective scientific data based on randomized, prospective clinical studies comparing the various surgical alternatives are lacking. The information that exists does not clearly favor any one single approach or operative option. It is critical to remember that each surgeon's experience and skill with a given technique have a profound impact on outcome. Contemporary spine surgeons should be well-versed in multiple operative techniques and should choose an appropriate approach for each individual patient based on that patient's clinical presentation and higher unique anatomy and pathologic condition, modified by the surgeon's personal experience.

Delayed hearing loss after neurovascular decompression.

We report two unusual cases of delayed hearing loss after neurovascular decompression of structures within the cerebellopontine angle. In the first case, the patient noted a unilateral hearing loss 3 weeks after undergoing vascular decompression of the trigeminal nerve for tic douloureux. This gradually improved over an 18-month period. In the second case, the patient awoke on the 4th day after vascular decompression of the facial nerve for hemifacial spasm with a bilateral hearing loss that has remained unchanged after the onset. These are examples of delayed acoustic dysfunction occurring with a shift in surgically freed vessels and may have been induced by newly directed neurovascular compression or distortion.

Anterior cervical fusion and Caspar plate stabilization for cervical trauma.

A technique for anterior cervical iliac graft fusion with standardized, commercially available screw and plate fixation (Caspar plating) has been developed. The step-by-step procedure, as well as the instruments designed to facilitate the procedure, are described in this report. Sixty cases of cervical trauma (fractures, subluxations, ligamentous instability, or a combination of these problems) were treated with Caspar plating. All patients obtained fusion, and stability was achieved immediately after surgery without external stabilization. No unusual surgical complications occurred, and the most dreaded complication of dural penetration by drilling or screw placement was not observed. This report details the neurological presentation, anatomical lesions, surgical therapy, and outcome of these patients. Caspar plating combines the advantage of an anterior surgical approach with immediate postoperative stabilization without external stabilization. This advantage persists even in the presence of posterior ligamentous instability. The technique is an important addition to the surgical treatment of cervical trauma.

Microvascular anastomosis in spontaneously hypertensive and stroke-prone rats.

Carotid end-to-end microvascular anastomoses (MVA) were performed in 100 rats [50 spontaneously hypertensive (SHR); 30 spontaneously hypertensive stroke-prone (SHR-SP); and 20 normotensive controls (WKY)]. Animals were sacrificed at various intervals from immediately after anastomosis to 60 days after surgery, and vascular healing was studied with the scanning electron microscope. In this manner vascular healing in normotensive rats (WKY) could be compared with that in hypertensive rats (SHR and SHR-SP) with vascular disease. Results of this study suggest that vascular healing in hypertensive rats is delayed when compared with normotensive controls. Furthermore, suture material was occasionally incompletely endothelialized in hypertensive animals as long as 60 days after surgery and served as a potential source of emboli. Additionally, an increased susceptibility of hypertensive endothelium (SHR and SHR-SP) to clamp and needle injury was apparent. In spite of this, there was a 100% patency rate of all anastomoses performed, indicating that patency, per se, is unaffected by hypertensive vasculopathy.

Ossification of the posterior longitudinal ligament in Caucasians: diagnosis and surgical intervention.

Six cases of ossification of the posterior longitudinal ligament (OPLL) in Caucasians have been diagnosed during a 2-year period at Walter Reed Army Medical Center. Five cases were in men and one was in a woman. Three cases presented as myelopathy and three as radiculopathy. Diagnosis was best confirmed with computer-assisted tomography. All six cases were treated surgically via an anterior approach, microsurgical resection of the OPLL, and autograft fusion. Patients with radiculopathy had immediate pain relief after operation. Those with myelopathy required vertebrectomy and regained strength after operation. All patients improved with operation. OPLL is not a rare condition in Caucasians. With diagnosis and proper surgical intervention, prognosis for improvement is good.

Morphological studies of human arteriovenous malformations. Effects of isobutyl 2-cyanoacrylate embolization.

Ten patients with symptomatic arteriovenous malformations (AVM's) underwent embolization with isobutyl 2-cyanoacrylate (Bucrylate) delivered via a mini-balloon catheter according to the protocol of George and Pevsner. These patients underwent surgical removal of their embolized AVM, and surgical specimens were evaluated by light and scanning electron microscopy. Ten other patients with AVM's underwent surgical resection without prior embolization, and these surgical specimens were evaluated in a similar manner. Results from this study indicate that Bucrylate incites an inflammatory response characterized by foreign-body giant cells. This reaction was present as early as 3 weeks after embolization and persisted in specimens resected almost 1 year after the last embolization. No such reaction was observed in unembolized AVM's. Both light and scanning electron microscopy demonstrated a lattice structure of the Bucrylate embolus within the AVM vessels. These studies also demonstrated micro-channels within the Bucrylate embolus and the presence of what appears to be normal red blood cells within the latticework of the embolus. Vascular endothelium not in direct contact with the Bucrylate embolus retains a normal morphology as revealed by scanning electron microscopy.

Spasmus nutans as a presenting sign of an arachnoid cyst.

Spasmus nutans, usually believed to be a benign entity, is a disorder of young children consisting of nystagmus, head nodding and an anomalous head position of unknown etiology. We present a patient with spasmus nutans who proved to have a large arachnoid cyst. When the cyst was shunted the nystagmus lessened. Recent studies suggest that the head nodding and anomalous head position are adaptive mechanisms that compensate for the nystagmus and not pathological in themselves. Therefore, spasmus nutans is not a triad of findings, but an acquired nystagmus with associated adaptive responses. Because spasmus nutans implies a benign entity composed of three requisite components, we feel it is an inaccurate term that should be abandoned. A better designation would be acquired nystagmus of infancy, which would not imply a benign etiology.

The structure of the mammalian area postrema.

The area postrema in mammals other than rodents and lagomorphs is a bilateral mound of gelatinous-appearing tissue that protrudes into the caudal fourth ventricle on either side of the obex. In rodents and lagomorphs it is a single midline structure at the apex of the calamus scriptorius. The vasculature is derived mainly from the posterior inferior cerebellar arteries and consists mainly of sinusoidal capillaries. It appears to constitute a portal system, at least in the rat. Many of the capillaries are fenestrated, and many large perivascular spaces with both vascular and parenchymal basal laminae are present. The cell population is composed of flattened ependymal cells exhibiting microvilli, and of small neurons, normal astrocytes, glialoid cells, and a very few oligodendroglia. Mast cells are occasionally present. The glialoid cells appear to be the predominant cell type and exhibit great numbers of vascular podia. Axodendritic synapses are numerous and axosomatic synapses are occasionally seen in the parenchyma. Synaptic vesicles are mainly of the clear-cored type but large dense-cored vesicles are commonly observed in some axon terminals.

Effects of aging on the structural and permeability characteristics of cerebrovasculature in normotensive and hypertensive strains of rats.

This study demonstrates that markedly different patterns of age-related changes in blood pressure and body weight occur among normotensive Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats and spontaneously hypertensive rats (SHR). In addition, a variety of age-related structural alterations occurred in the walls of arterioles, capillaries, and venules of the frontal cortex. These changes include: (1) an increase in the thickness of the vascular wall by deposits of collagen and basal lamina which, in some cases, extended into the surrounding neuropil; (2) the presence of a flocculent material in the adventitia of intracerebral arterioles; (3) vesicular inclusions in perivascular macrophages, pericytes and smooth muscle cells which were labelled with i.v. administered horseradish peroxidase (HRP); (4) fragmentation of smooth muscle cells; and (5) accumulation of lipofuscin-like pigments in perivascular glial processes. The hypertensive rats exhibited these changes, but they were more advanced and more widely distributed throughout the cerebral cortex. The aged hypertensive rats occasionally had large bundles of 10 nm diameter, intermediate filaments in the endothelial cells. Whereas no change in blood-brain barrier permeability to HRP was observed in the aged normotensive rats, all age groups of the hypertensive rats exhibited increased permeability to HRP in the initial segment of penetrating arterioles in laminae I and II of the cerebral cortex.

Effects of systemic administration of 6-hydroxydopamine on the circumventricular organs in nonhuman primates. I. Area postrema.

6-Hydroxydopamine (6-OH-DA) has been shown to produce degenerative changes in noradrenergic nerve terminals and preterminals in the CNS following intracisternal, intraventricular or direct injection into the brain parenchyma. Systemic injection of 6-OH-DA is known to result in degenerative changes in noradrenergic terminals in the peripheral nervous system. However, only a few studies have been carried out on the effects of systemic injections of 6-OH-DA on noradrenergic terminals in the CNS. In the present study cynomolgus and squirrel monkeys were injected intravenously on two successive days with total doses of 350 mg/kg and 150 mg/kg of 6-OH-DA, respectively, and sacrificed at 2 and 24 h following the second injection. Degenerative changes in the area postrema (AP) neurons in all injected animals were characterized by a generalized increase in electron density of cytoplasmic elements in axonal terminals and preterminals. Multilamellar bodies, clusters of clear and dense core vesicles, increased numbers of secondary lysosomes, and an increase in the number of glycogen increased markedly in injected animals, but no other glial alterations were observed. The number of mast cells in the AP was greater in injected than in noninjected animals, both in the perivascular spaces (PVS) and in parenchymal locations. Cell processes in the PVS were occasionally observed to contain electron dense bodies, and degenerative changes were seen in supraependymal processes in some injected animals.

Ultrastructure of the feline area postrema.

The morphology of the feline area posterma (AP), a circumventricular organ, has been studied by scanning (SEM) and transmission electron microscopy (TEM). In SEM preparations the boundary of the AP was sharply delineated by the absence of kinocilia. Microvilli were numerous and seemed to be concentrated at the junction between ependymal cells, imparting a polygonal surface pattern superimposed on cell boundaries. Some cell processes were present on the AP surface, but no supra-ependymal cell bodies could be seen over the AP proper. In TEM preparations the AP was characterized by blood vessels with distinct perivascular spaces. These spaces contained fibroblasts and collagen, and were limited by basal laminae. Capillary endothelial cells were typically fenestrated and contained numerous pinocytotic vesicles. Bulbous ending of attenuated cellular processes terminated on the external basal laminae of AP vasculture. Some of these endings could be traced to the cells covering the ventricular surface of the AP. These cells demonstrated several features co-mon to ependymal cells which have been identified as tanycytes. The presence of small neurons frequently seen in groups of three or four confirm previous light microscopic studies. Synapses predominantly of the axodendritic variety were observed, and both dense cored and clear cored vesicles were present on the same ending. Myelinated and unmyelinated axons were a consistent finding in the AP with the former being more abundant in the lateral margins of the AP and in the region of the area subpostrema. The chemoreceptive function of the AP has been widely accepted; however, studies indicate that it is not possible to distinguish species possessing an emetic reflex on the basis of ultrastructural morphology. The possibility that the AP serves functions in addition to emetic chemoreception is considered.

The ultrastructural morphology of the squirrel monkey area postrema.

Examination of the squirrel monkey (Saimiri sciureus) area postrema (AP) revealed this circumventricular organ to be primarily composed of two types of glial cells and a single type of neuronal element. No pattern of neuronal arrangement could be discerned, however, this cell type was frequently observed in close relation to the perivascular spaces. The neuronal elements, although slightly larger than the glial cells, were characteristically less electron dense. The neurons routinely displayed an infolded nuclear membrane, a single nucleolus and the normal complement of subcellular organelles. Synaptic terminals were numerous, and both axo-somatic and axo-dendritic varieties were observed with the latter being more numerous. Both clear-cored and dense-cored vesicles could be observed in the same ending. Unmyelinated neuronal processes were the predominant type within the interior of the AP, although myelinated processes were also regularly present. Non-neuronal elements with the AP resembled CNS astrocytes and were as numerous as the neuronal elements. This cell type appeared to envelope completely the vasculature and separated the parenchyma from the perivascular spaces. The ventricular surface of the AP was covered by modified ependyma which lacked kinocilia but frequently demonstrated microvillar projections. Opposed ependymal cell membranes showed interdigitations, and zonula adherens-type cell junctions connected the ependymal cells near the ventricular lumen. Two types of bulbous projections were observed in the ventricular lumen close to the ependymal surface. The most characteristic feature of the AP, however, was its vascularity. Perivascular spaces surrounding fenestrated capillaries contained fibroblasts and collagen. The vascular endothelium routinely demonstrated pinocytotic activity, and the basal lamina was prominent.