Biomedical subjects
Publications and source records attributed to R G Quisling.
The anatomy and angiographic appearance of the great horizontal fissure is seen on most vertebral angiograms of excellent quality and is best shown on the lateral and AP (transfacial) projections. Identification of the fissure may provide an additional angiographic landmark for precise localization of peripherally situated masses, either within or adjacent to the cerebellum.
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Until recently all callosal lipomas were grouped together. However, these lipomas can be clearly separated into two groups having different morphologies and associated brain anomalies. One group consists of anteriorly situated round or cylinder-shaped lipomas, termed tubulonodular. These lipomas are generally greater than 2 cm in diameter and have a high incidence of corpus callosum dysgenesis, frontal lobe anomalies, and frontal encephaloceles. The second group comprises thin, posteriorly situated lipomas curving around the splenium and are termed curvilinear. The curvilinear lipomas are generally associated with a normal corpus callosum and otherwise have a low incidence of associated anomalies. When anomalies do occur, they tend to be less severe than with the tubulonodular lipomas. We present four cases of curvilinear lipomas and review similar cases in the literature to explain why lipomas of the callosal region have such a variety of associated anomalies and morphologies. Our findings support the idea that both groups of lipomas develop in the region of the origin of the corpus callosum but form at different times during gestation, with the tubulonodular ones forming earlier and thus being associated with more severe cerebral anomalies.
Traditionally, the decussation for the pyramids has been the designated marker for the cervicomedullary junction. With Chiari malformations abnormal caudal migration of posterior fossa structures occurs, resulting invariably in a low position of the caudal poles of the cerebellar tonsils (i.e. tonsillar heterotopia) and a low position of the cervicomedullary junction. Since there is considerable variability in normal caudal tonsillar position and because the pyramidal decussations are difficult to image, diagnostic confusion may exist when the cerebellar tonsils reside in an intermediately low position. This study utilized anatomic specimens to establish the normal morphologic relationship between the position of the obex/nucleus gracilis (O/NG) and the pyramidal decussations; the former consistently lies 5-6 mm rostral to the latter. Having established that anatomic relationship, the O/NG position was then used to assess the cervicomedullary junction position in a radioanatomic survey of normal brain MR examinations. This analysis established a mean O/NG position 10-12 mm above the plane of the foramen magnum. The O/NG position was then evaluated in patients with low tonsillar position. This analysis revealed, as expected, that patients with Chiari II malformation exhibited tonsillar and O/NG positions well below the plane of the foramen magnum. It also distinguished between two additional groups of patients with less florid MR findings. These include patients who exhibit minimally low cerebellar tonsils but essentially normal O/NG position; these patients should be considered normal expressing only minor variation of tonsillar position. The remaining patients exhibit evidence of both intermediately low tonsillar and low O/NG positions, suggesting an underlying anomaly of both tonsil and brainstem development.(ABSTRACT TRUNCATED AT 250 WORDS)
Tandem arteriosclerotic lesions of the carotid sinus and siphon increase the risks of carotid endarterectomy; when the siphon is severely stenotic, a microvascular bypass may be the preferable procedure. Two patients, each with severe siphon stenosis and significant sinus lesions, however, were subjected to carotid endarterectomy as their initial surgical procedure. The postoperative arteriogram showed resolution of the siphon stenosis in both patients. The identification of an associated extracranial lesion, or the presence of a lesion located more distal in the siphon than atheroma usually occur, should alert the surgeon that the intracranial obstruction may be due to embolism. In patients with these tandem lesions, therefore, a repeat arteriogram, performed several weeks after endarterectomy of sufficient medial treatment interval, may show resolution of the intracranial lesion, and may avoid an unnecessary bypass procedure.
Venous pressures were measured within the vein of Galen aneurysm/straight sinus complex in 15 patients with Galenic arteriovenous fistulae and vein of Galen aneurysms. Pressures exceeded normal (less than 5 cm of H2O) in each instance, ranging between 9 and 55 cm of H2O. Measured values exceeding 20 cm of H2O were associated with an increased occurrence of brain calcification. Mean venous pressures were relatively higher in the patients with thalamic arteriovenous malformations, and relatively lower in patients with true vein of Galen fistulae and choroidal type malformations. A pressure gradient across the straight sinus was measured in one patient and suspected in three others when disproportionate dilatation of the vein of Galen occurred in the presence of a small or normal-sized straight sinus. No clear relationship existed between levels of venous pressure elevation and degree of ventriculomegaly. Refractory heart failure occurred only in neonates with choroidal type fistulae and no apparent venous outflow obstruction. It is likely that the degree of venous pressure elevation reflects the hemodynamic significance of arteriovenous shunt, provided it is interpreted in context with the current clinical status and the angioarchitecture of the Galenic fistula. Such data may assist in the timing of embolotherapy. Patients with lower venous pressure are not likely to develop brain calcification or seizures, and therefore can tolerate transtorcular embolotherapy staged at wider intervals.
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The treatment of carotid-cavernous fistulae with intravascular, detachable latex balloons has become an accepted method. However, the histologic changes associated with such balloon embolization in a high-flow fistula state have not been described. This study evaluated the microscopic findings in a series of 12 rats studied over a 3-month period using an aortocaval fistula model. Small latex balloons were introduced into the venae cavae of rats in whom aortocaval fistulae had been surgically created 3 weeks earlier. The histopathologic changes associated with treatment of these fistulae were examined at 1, 2, 4, 6, 8, and 12 weeks. These changes can be characterized by an acute phase with thrombus formation and acute inflammation, followed by intermediate (or subacute) and chronic phases with diminishing inflammation and progressively increasing fibrosis of the fistula site. The latex balloon became encased by the fibrotic reaction but remained nonadherent and was easily removed at every study interval. No abscess formation or persistent vasculitis was apparent, and foreign-body giant cell reaction was minimal. Closure of the high-flow fistula site required the balloon to remain inflated for at least 7-9 days.
An animal model for a high-flow, aorta-to-vena cava fistula has been developed using microsurgical techniques in the rat. This model provides a means for histopathologic and angiographic evaluation of the natural evolution of major vessel, artery to vein fistulae. Data obtained from such a model may have relevance to the successful treatment of high-flow, head and neck fistulae using detachable intraarterial occlusive balloons. This microsurgical technique is unique, since it requires no intervening sutures or graft material that would alter the histopathologic process. After a series of such aortocaval fistulae were created, serial histologic and angiographic features were elucidated for intervals between 1 day and 6 months. Three stages of evolution are noted including: an initial hemorrhagic dissection phase; a subacute phase where organization of the thrombus and actual formation of a fistulous tract occurs; and a chronic phase characterized by pseudoaneurysm formation, arterialization of the vena cava, and proximal vasodilatation of the aorta.
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Polyvinyl alcohol (PVA) foam particles have been used with success in both experimental and clinical embolization of vascular lesions. Cellular response to PVA has been well documented outside, but not within, the central nervous system. This study was directed specifically at the cellular response to PVA in rat brain vasculature. By using small numbers of microparticles, an effort was made to define the response to PVA alone, rather than associated occlusions or infarctions. It was determined that PVA elicited no significant inflammatory response in the embolized vessels nor in the surrounding tissue. The isolated fragments did not appear to alter the blood-brain barrier. The PVA microemboli were extremely adherent to vascular endothelium, lodging in vessels of larger diameter and in relatively high-flow locations without actually wedging within the vessel lumen. On the basis of this analysis, it was determined that PVA foam has properties suitable for an intracerebral vascular embolic agent.
PURPOSE AND METHODS: To assess its vascular effects and safety, we used sodium methohexital (Brevital)--an ultrashort-acting barbiturate--as the provocative intraarterial agent in a series of 30 patients with arteriovenous malformations at a 1% concentration and at doses of less than 5 mg per injection. Digital vascular imaging was performed just prior to and just after the injections. RESULTS: No angiographic or clinical evidence of apparent vasospasm occurred in the trial population (66 vascular pedicle injections in 30 patients). When functional tissue was perfused with 1-6 mg of the 1% Brevital solution, evidence of altered neurologic status became immediately apparent, but cleared within 2 minutes in all cases. None of the patients experienced either prolongation of the induced clinical symptoms or seizures to suggest any adverse effects related to either crystallization of the Brevital or the effects of injecting an alkaline solution in the cerebral circulation. CONCLUSION: Though the full effects of methohexital in the cerebral circulation remain to be elucidated, existing reports suggest it is a safe provocative agent for use prior to embolotherapy for brain arteriovenous malformations.
Primary intracranial germ cell neoplasms are rare tumors and constitute a heterogeneous group. We have reviewed 32 cases, over a 21-year period, from the University of Florida. The cases include 22 germinomas, 6 mixed germ cell tumors, and 4 teratomas. The clinical presentations in these cases were more closely related to the location of the tumor, that is, pineal or suprasellar, rather than the histologic subtype. Neuroimaging evaluation was useful in distinguishing between germinomas, teratomas, and other mixed germ cell tumors (MGCTs), primarily by evaluation of cystic versus solid lesions (teratoma versus germinoma), contents of cysts (teratoma versus MGCT), and infiltrative nature of the tumors (MGCT), although cytologic-histopathologic confirmation remains necessary. Germinomas responded favorably to radiation therapy with survival periods of over 16 years; MGCTs were treated with combination chemotherapy and radiation, with a markedly poorer prognosis. This study underlines the critical significance of histopathologic evaluation of the tumor in determining therapeutic interventions as well as prognosis.
Retrorectal cyst-hamartoma, an uncommon lesion, arises from hindgut embryonic remnants and may be associated with sacral anomalies. Such a lesion is presacral, multicystic, and lined with glandular or transitional epithelium. Malignant transformation of these lesions has been reported. We describe the clinical, pathologic, and imaging findings in an infant.