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Biomedical subjects

S Rossitti

Publications and source records attributed to S Rossitti.

25 records · Page 2Linked to original sources
PubMed1993

The transoccipital approach for transcranial Doppler ultrasonography of the vertebrobasilar circulation.

With the transoccipital paramedian approach for transcranial Doppler examination of the vertebrobasilar circulation, a complete examination of the intracranial vertebral arteries and basilar artery is possible without moving the patient from the supine position; this may be of value in intensive care conditions. Blood flow velocity and flow direction in these vessels are registered through the occipital bone at relatively more superficial levels, and identification of right and left vertebral arteries usually represents no problem.

Adult↗
PubMed1993

The extreme lateral approach to thoracic disc herniations: technique and preliminary results.

The extreme lateral approach to the thoracic disc spaces produces minimum disruption of the normal spinal anatomy, avoids retraction of the spinal cord, and preserves the intercostal neurovascular bundle. It is achieved by removal of about 5 cm of the rib which has its insertion at the disc level, if necessary associated with partial removal of the transverse process, followed by partial pediculotomy and a limited lateral rachitomy (vertebral body resection), which permits the opening of the spinal canal exclusively ventral to the intervertebral foramen. The initial results of 6 patients, operated in up to four discs at the same occasion, are promising.

Adult↗
PubMed1993

Vascular dimensions of the cerebral arteries follow the principle of minimum work.

BACKGROUND AND PURPOSE: The principle of minimum work is a parametric optimization model for the growth and adaptation of arterial trees. It establishes a balance between energy dissipation due to frictional resistance of laminar flow (shear stress) and the minimum volume of the vascular system, implying that the radius of the vessel is adjusted to the cube root of the volumetric flow. The purpose of this study is to verify whether the internal carotid artery system obeys the principle of minimum work. METHODS: Measurements of the radius of parent and branch segments of the internal carotid, anterior, and middle cerebral arteries were performed on analog angiographs chosen at random from a set classified as normal. The branch angles were measured from lateral projections in bifurcations of the anterior cerebral artery. The relation of the calibers of parent and branch vessels was analyzed. RESULTS: The area ratio of the bifurcations (N = 174) was 1.2 +/- 0.4 (mean +/- SD). The equation (r0)n = (r1)n + (r2)n was solved for n, resulting in n = 2.9 +/- 0.7 (mean +/- SD, N = 157). Optimum proportions between the radii of parent (r0) and branch (r1 and r2) vessels in the internal carotid artery system were verified in normal carotid angiographs up to four branch generations, according to the theoretical equation r0(3) = r1(3) + r2(3) (r = 0.989, N = 174). No clear correlation was found between the measured branch angles, the relative branch cross-sectional area, and the theoretical optimum angles. CONCLUSIONS: This study demonstrates that the process of branching of the internal carotid artery system obeys the principle of minimum work, as the diameter exponent approximates 3. The principle of minimum work establishes strict functional relations between volumetric flow, flow velocity, and vessel radius. This model was extended to parametric optimization of branch angles, which has proved irrelevant in terms of functional optimization. Our results corroborate this finding. Shear stress-induced endothelial mediation seems to be the regulating mechanism for the maintenance of this optimum vessel design. The magnitude of wall shear stress is the same at every point in a vascular network obeying the principle of minimum work, because the flow rate influences the shear stress proportionally to the third power of the vessel radius. This observation has implications for understanding the remodeling of the cerebral vascular network in the presence of arteriovenous malformations and for the pathogenesis of saccular aneurysms.

Blood Flow Velocity↗
PubMed1993

Optimality principles and flow orderliness at the branching points of cerebral arteries.

BACKGROUND AND PURPOSE: The cerebral arteries present an optimum blood flow/vessel radius relation. However, branch angles may vary widely in the cerebral arteries because the parametric optimization of branch angles is irrelevant in terms of energy cost. The position of the flow divider in extracranial arteries has been suggested to be optimum in flow orderliness. No data exist on the flow divider of cerebral arteries. Thus, we hypothesized that in the cerebral arteries the apex of the bifurcations, which is known to be the site of maximum hemodynamic stress in a vascular network, may normally lie in a non-optimum position relative to the dividing flow streamline in the parent vessel, leading to disturbed laminar flow and increased vessel wall shear stress at the apical region despite the optimum blood flow/vessel radius relation. The objective of this study was to test our hypothesis. METHODS: We measured the branch angles and diameters of parent and branch segments of the anterior cerebral artery system from lateral projections to minimize the measurement error on angiographs chosen at random from normal sets. The position of the apex of the bifurcations in relation to the ostium of the parent artery (gamma) and the ratio of the branch diameters (d2/d1) were compared. Optimum curves for these parameters were calculated by a mathematical model. In addition, the separation of flow streamlines according to gamma was calculated for each bifurcation and related to the division of flow required by each branch according to the optimum blood flow/vessel radius relation. RESULTS: The data points on gamma and d2/d1 and the separation of flow according to gamma and the division of flow required by the branches were found to scatter around the optimum curves. However, a trend toward the theoretical optimum is discernible. The data points are suggested to be a random sample from a normal distribution around the optimum (.40 < P < .50). CONCLUSIONS: The bifurcations of the cerebral arteries appear to be optimized to avoid increased hemodynamic stresses both globally and locally in the same manner as extracranial arteries.

Aneurysm↗
PubMed1993

[Operational manual of the reaction level scale (RLS85)].

The Reaction Level Scale (RLS85) is a range scored coma scale (8 levels) for the assessment of responsiveness in patients with acute brain disorders. Its feasibility in clinical practice and for research studies has been verified in a multicentre study and by comparison with other current coma scales. Range scoring and absence of pseudoscoring are its most significant advantages over the other current scales. An operative manual of the RLS85 in Portuguese is standardized in this text which also provides a selected bibliography on the subject.

Glasgow Coma Scale↗
PubMed1993

The anterior approach to high thoracic (T1-T2) disc herniation.

A patient with a T1-T2 disc herniation, operated on via the anterior approach, is presented. In a search of the literature we found 18 reported cases, all operated on by posterior or posterolateral approaches. The feasibility of the anterior discectomy in our case was established by preoperative magnetic resonance imaging of the upper thorax. We think that an anterior discectomy at the level of the upper thoracic spine can be easily performed in selected cases. The clinical picture of T1 root compression is described.

Adult↗