Modeling of arterial stenosis and its applications to blood diseases.

Blood flow in a stenosed tube has been modeled in the present studies. Blood flow is assumed to be represented by a couple stress fluid. Flow parameters such as velocity, resistance to flow, and shear stress distribution have been computed for different suspension concentrations (haematocrit), and for the blood diseases; polycythemia, plasma cell dyscrasias, and for Hb SS (sickle cell). The results have been compared with the case of normal blood and for other theoretical models. The importance of size effects in blood flow studies has been highlighted.

Completeness of callosotomy shown by magnetic resonance imaging in the long term.

Six individuals who had complete cerebral commissurotomy for medically intractable epilepsy participated in a magnetic resonance imaging study 20 or more years postoperatively. In all cases the completeness of callosotomy was clearly demonstrable. The status of the anterior commissure, cut in all six, could not be confirmed with the same confidence.

MR imaging of primary tumors of trigeminal nerve and Meckel's cave.

MR imaging features of 11 primary tumors of the trigeminal nerve and Meckel's cave were analyzed. The tumors consisted of two trigeminal schwannomas, five meningiomas, one lipoma, and three epidermoid tumors. The trigeminal schwannomas had homogeneously decreased signal intensity on T1-weighted images and increased signal intensity on T2-weighted images. Three of the five meningiomas had signal intensity similar to that of surrounding brain on both T1- and T2-weighted images. One meningioma had decreased signal intensity on T1-weighted images and increased signal intensity on T2-weighted images. The other had relatively low signal intensity on both T1- and T2-weighted images owing to heavy calcification demonstrated on CT. The lipoma had homogeneous signal intensity that was isointense with orbital and subcutaneous fat on both T1- and T2-weighted images. The epidermoid tumors had decreased signal intensity on T1-weighted images and markedly increased signal intensity on T2-weighted images. In addition, the epidermoids had an insinuating growth pattern and minimal mass effect. The extent of involvement in the trigeminal nerve distribution was well demonstrated in each case. Because of its multiplanar capability, exquisite anatomic detail, and characteristic tissue signal intensity, we conclude that MR is helpful in the differential diagnosis of primary tumors of the trigeminal nerve and Meckel's cave and in the evaluation of tumor involvement for preoperative planning.

Two-layered blood flow in stenosed tubes for different diseases.

A two-fluid model for blood flow through a stenosed tube has been developed. The model consists of a core (suspension of RBCs) and peripheral plasma layer. The core is assumed to be represented by a polar fluid and the plasma layer by a Newtonian fluid. The flow is assumed to be steady and laminar, and the fluids incompressible. The flow variables are computed for normal blood and for the cases of polycythemia, plasma cell dyscrasias and for Hb SS diseases. Resistance to flow has been computed for different stenosis length and for different stenosis height. Shear stress distribution along the axial distance has been computed for different stenosis height. The impact of size effects (particle size to tube diameter) on blood diseases is discussed.

Spinal subarachnoid tumor seeding from intracranial metastasis: MR findings.

We describe the magnetic resonance findings in two cases of spinal subarachnoid seeding from an intracranial metastatic lesion. Magnetic resonance imaging techniques using T1 and intermediate T1-T2 pulse sequences improve anatomical definition of the spinal cord-thecal sac and allow for optimal contrast to define metastatic deposits in the subarachnoid space. Heavily T2 weighted pulse sequences do not appear to be useful in the diagnosis of subarachnoid metastases.

Evaluation of cerebrospinal fluid rhinorrhea by metrizamide computed tomographic cisternography.

Seven interesting and instructive cases of cerebrospinal fluid rhinorrhea evaluated by metrizamide computed tomographic cisternography are presented. The rhinorrhea was spontaneous in three patients and was related to previous head trauma or surgical procedures in four patients. The anatomical site and the extent of the fistula were demonstrated precisely by directly showing metrizamide passing through the bony defect. A combination of bone dehiscence and metrizamide within the adjacent paranasal sinuses or the nasal cavity is also useful in localization. Distortion of the interhemispheric fissure, sylvian fissure, or basal sulci indicates the probability of brain herniation through the defect.

Combination chemotherapy with cyclophosphamide, vincristine, procarbazine, and prednisone (COPP) in children with brain tumors.

The chemotherapeutic combination of cyclophosphamide, vincristine, procarbazine, and prednisone (COPP) was used to treat 15 children with recurrent central nervous system tumors and seven children with newly diagnosed brainstem tumors. In patients with recurrent tumors, marginal activity was seen in various histologic types. COPP chemotherapy was clearly ineffective in patients with brainstem tumors. Toxicity consisted of mild to moderate myelosuppression and neurotoxicity.