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Purpose: To introduce a new stent design and evaluate its technical properties. Methods: This stent consists of two nitinol wires partially connected to each other. After delivery through a catheter a tube-like helical stent forms within the artery. After experimental tests in flow models regarding mechanical properties, introduction and delivery technique, 15 stents were implanted into iliac, femoral, and carotid arteries of seven dogs. After 3–12 weeks angiographic follow-up stents were explanted for microscopic examination. Results: Stents with expanded diameters of 5–10 mm can be introduced through a 5 Fr catheter with 0.038 inch luminal diameter. Thrombotic vessel occlusion was observed in one iliac artery after incorrect stent placement with diameter mismatch. Fourteen of 15 stents remained patent and revealed minor intimal hyperplasia in the areas of the stent strut connection points as well as some reduction in medial thickness. Conclusion: This new stent design has a small introduction diameter which is independent of the expanded diameter. The stent’s principal characteristics may serve as a basis for further special developments.

Purpose: To evaluate the safety and efficacy of stent therapy for the treatment of residual stenoses after percutaneous transluminal angioplasty (PTA) of popliteal stenoses and occlusions. Methods: In a prospective single-center study, flexible tantalum stents were implanted in 32 popliteal arteries for the treatment of residual stenosis greater than 50% after PTA of stenoses (n = 17) or occlusions (n = 15) in the P1 (n = 16), the P2 (n = 13), or both P1 and P2 segment (n = 3). Follow-up patency was assessed by clinical examination, ankle-brachial index, and color Doppler sonography or angiography. Results: Early stent thrombosis (10 days): 1 of 32 arteries (3%). 1-year and 2-year primary patency rate (PPR): 81% ± 7.1% and 74% ± 9.1%, respectively. 1-year PPRs for subgroups: stented stenoses versus stented occlusions: 88% ± 7.8% vs 73% ± 12.0%, p = 0.12; good lower limb runoff versus poor: 84.0% ± 8.7% vs 76.0% ± 12.4; p = 0.09; P1 versus P2: 77.3% ± 9.8% vs 85.7% ± 9.4%, p = 0.38. Recurrent PTA lesions treated with stents showed higher restenosis rate than de novo lesions. Conclusion: The results of stent therapy of residual popliteal stenosis after PTA are encouraging and warrant further investigation.

To evaluate the angiographic and clinical effects of percutaneous transluminal angioplasty (PTA) of distal ostial collateral stenoses in patients with claudication and long-segment occlusion of the superficial femoral artery (SFA).In ten patients (9 men, 1 woman) with stable intermittent claudication due to chronic long-segment occlusion of the SFA a high-grade stenosis of the distal collateral ostium of the deep femoral artery to the popliteal artery were dilated. PTA was performed using popliteal artery access. Claudication distances on the treadmill and ankle-brachial pressure indices (ABI) at rest were analyzed before, 1 week, and 14 weeks after PTA.Initial technical success was obtained in all patients. There were no significant periprocedural local complications. The initial mean claudication distance on the treadmill increased significantly from 107 +/- 65 m to 306 +/- 209 m (p0.01), the maximal claudication distance from 203 +/- 128 m to 392 +/- 167 m (p0.01). The mean ABI changed slightly but significantly (0.61 +/- 0.08 vs. 0.64 +/- 0.07; p0.05). Early follow-up after 14 weeks revealed no clinical deterioration.This new technique is considered helpful in patients with well-defined claudication and long-segment occlusion of the SFA.

Evaluation of short- and extended-term results of repeated epidural/perineural injections (EDT/PRT) of corticoids in painful afflictions of the lumbar spine.Thirty-two patients who had persistent radicular or low back pain for more than 6 weeks were treated with CT-guided injection therapy. By EDT/PRT, 40 mg of triamcinolonacetonid was injected either periradicularly or by a direct intraspinal epidural method at intervals of 3 weeks. Altogether, 140 EDT/PRT were performed in 32 patients (mean 4.4, range 2-8). In nine patients partial facet joint denervation with 1-2 ml of 50% alcohol solution was combined with EDT/PRT to reduce low back pain. Before and after treatment and at follow-up (mean 9.6 months), treatment success was evaluated on a visual analog scale and by physical examination (good =50% improvement, moderate = 20%-50%, no improvement =20%).Short-term (end of therapy) good or moderate improvement was achieved in 91% of patients, extended-term (mean 9.6 months) in 56%. Regarding certain subgroups, those with disc herniations of the lumbar spine showed a better outcome with good or moderate improvement in 95% short-term and 69% extended-term than those with spinal stenosis who had 72% short-term and 28% long-term.Results indicate that CT-guided EDT/PRT in combination with partial facet joint denervation is a safe and effective outpatient treatment.

The aim of the study was to determine whether hemodynamic and functional variables are related to the angiographic extent of lower limb atherosclerosis. In 150 patients with stable intermittent claudication, the Bollinger angiogram score was compared with the resting Doppler pressure values, and the initial claudication distance (ICD) and absolute claudication distance (ACD) with treadmill exercise. The extent of lower limb atherosclerosis correlated significantly with the age of the patients and the duration of the claudication. The angiogram scores of the patients were negatively correlated with the ankle systolic blood pressure (SBP) and the ankle/brachial index (ABI). In a multiple regression analysis, ABI was the most predictive variable for the angiographic severity of disease. ICD, ACD and work on the treadmill failed to correlate with the angiogram summation score. If patients were classified into groups for those with iliac or femoropopliteal disease, a weak correlation between ACD and femoropopliteal angiogram score was found. The comparison between Doppler measurements and treadmill exercise testing showed no significant correlation between SBP/ABI of the more diseased limb and ICD. However, both SBP and ABI did correlate significantly with ACD (r = 0.16, p, 0.05 and r = 0.20, p, 0.01, respectively). In conclusion, SBP and ABI are reliable parameters for indirect assessment of the angiographic extent of lower limb atherosclerosis. In contrast, the walking capacity of claudicant patients is independent of the angiographic severity of the disease.

Purpose: Polymer-coated, dexamethasone (DXM)-releasing stents were tested in order to assess the efficacy of DXM released locally for the prevention of stent restenosis due to intimal hyperplasia. Methods: Strecker stents coated with a biodegradable membrane containing DXM were implanted percutaneously into the femoral artery in 14 dogs. The contralateral artery received a conventional non-coated stent serving as control. The drugs are eluted by degradation of the carrier membrane. Follow-up intraarterial digital subtraction angiography (DSA) was obtained at 3, 6, 9, 12, and 24 weeks with subsequent autopsy. Specimens for gross and microscopic pathology were obtained and histomorphometry was performed. Results: Four of 14 DXM-coated stents showed thrombotic occlusion within the first 3 weeks; ten DXM-coated stents remained patent. At follow-up DSA, DXM-coated stents showed a significantly wider lumen than the non-coated stents. At morphometry there was less intimal hyperplasia over DXM-coated stents than over non-coated stents (p

To present the initial results of a new percutaneously implantable catheter port system (PIPS) used for long-term intraarterial infusion therapy in patients with severe ischemic limb disease.Ten patients with deep, extended ischemic ulcerations (all 10) and osteomyelitis (6/10) of the foot received intraarterial infusions of prostaglandine E1 and antibiotics, if indicated, via a new port catheter system with the port placed subcutaneously above the groin after percutaneous introduction and the catheter tip placed into the superficial or deep femoral artery.Port implantation and repeated port access were uncomplicated. During the follow-up period (mean 11 months, range 1 week-50 months), port migration, leakage, or infection was not observed. Three catheters thrombosed and were opened by fibrinolysis with recombinant tissue plasminogen activator instilled via the port. Treatment success was achieved in 8 patients: relief from rest pain (8 patients), reduction of ulcer size (4/8), and complete healing (4/8). Limb savage rate was 80%. In 2 patients amputation could not be avoided.Selective long-term arterial infusion therapy presents a valuable therapeutic regimen for limb salvage. With the new catheter port system, repeated local intraarterial infusion is safe and simple.

To evaluate the clinical use of covered and noncovered, knitted nitinol stents in patients presenting new stent indications.Self-expandable, knitted nitinol stents were implanted in four patients for treatment of dysphagia. In two patients who had malignant strictures and had esophago-respiratory fistulae and in one patient with an esophagocutaneous fistula, polytetrafluoroethylene (PTFE)-covered stents were implanted. One patient received a noncovered stent, but a retrograde approach through a percutaneous endoscopic gastrostomy (PEG) fistula had to be chosen for recanalization of an esophageal occlusion. Two patients received stents for treatment of benign strictures.Recanalization of the stricture and stent implantation were performed under fluoroscopic control without any procedure-related morbidity or mortality. Dysphagia improved in all patients and the esophageal fistulae could be sealed off by covered stents. During a maximum follow-up of 18 months, there was no stent migration or esophageal perforation. Complications observed were stent stenosis due to food impaction (1/4) and benign stent stenosis (2/2). Most complications could be treated by the interventional radiologist.Self-expandable, covered Nitinol stents provide an option for the treatment of dysphagia combined with esophageal fistulae. In combination with interventional radiology techniques, even complex strictures are accessible. For benign strictures, the value of stent treatment has not yet been proven.

Knitted flexible tantalum stents proved to be a valuable adjunct to percutaneous transluminal angiplasty (PTA) in the case of insufficient PTA results, and their use was established in the distal aorta, the iliac, the femoro-popliteal, the renal, and the coronary arteries. Recently, long arterial occlusions were defined as new indications for primary stenting; stent indications were further extended to the subclavian, the carotid, and the splanchnic arteries. Due to higher incidence of acute and late complications after stent treatment of small diameter arteries, patients have to be selected thoroughly. Newly designed drug-releasing stents tested in animal experiments promised to be suitable to diminish the incidence of late restenosis due to intinal hyperplasia, thus providing better long-term patency.

Purpose: To present a new intravascular device for the treatment of aorto-iliac aneurysms. Methods: This new device was tested in five dogs with abdominal aortic aneurysm created experimentally by overdilation of a balloon-expandable stent with a 16 or 18 mm wide PTA balloon catheter. The design of the device is based on a self-expanding aortic stent which consists of two stretchable circular frames filled with a textile Dacron mesh membrane that is suspended horizontally into the infrarenal abdominal aorta proximally to the aneurysm. The frames are part of a preshaped double helical structure that is introduced longitudinally through a catheter in a parallel fashion and forming the desired shape at the vessel site to be occluded. Two iliac stent-grafts are introduced in a low-profile status through the membrane sealing the aneurysm sac and holding the stent-grafts in place. After stent-graft expansion, a new bifurcation located more proximally than the natural one is created. The follow-up of the dogs was performed clinically and angiographically, and specimens were evaluated histomorphologically. Results: The membrane device can be introduced through a 9 Fr vascular sheath. Technical success was achieved in four of five dogs. Nine of ten stent-grafts could be fixed securely within the membrane, thus preventing dislocation. Aneurysms were excluded immediately, and blood flow to the external iliac arteries was restored by the stent-grafts. At 6–9 months follow-up of technically successful implanted devices, there were no endoleaks, no migration, no stenoses at contact sites between the implant material and vascular wall, and no stenosis or occlusion of the stent-grafts. At microscopic evaluation, the interspace between the membranes was filled with thrombotic material, thus ensuring exclusion of the aneurysm. Conclusion: This new device was found to be flexible, low profile and useful in excluding abdominal aortic aneurysm in the experimental setting.

The purpose of this study was to assess the suitability of a percutaneously implantable catheter port system (PIPS) for repeated intraarterial locoregional chemotherapy (ILC) for cervical and endometrial carcinoma. In 30 patients with advanced, recurrent, or high-risk cervical (n = 23) or endometrial (n = 7) carcinoma, PIPS for ILC was implanted via a femoral access, the catheter localized in the infrarenal abdominal aorta. Chemotherapy was performed adjuvantly after surgery (n = 14) or neo-adjuvantly to enable surgery, or for palliation (n = 16). Port implantation, catheter placement, and repeated port puncture was uneventful in all patients. Complications included catheter dislocation (n = 1), catheter thrombosis (n = 2), subcutaneous infection (n = 1), port-bed skin atrophy (n = 1), requiring port explantation in 3 patients. At 2 years follow-up, complete remission was observed in 7/14 patients with adjuvant chemotherapy, partial remission in 3/14. Successful down-staging could be achieved in 4/8 patients with neo-adjuvant chemotherapy. The PIPS is suitable for repeated ILC which may be a valuable method for pre- and post-surgical therapy of advanced or high-risk cervical and endometrial cancer, for adjuvant chemotherapy as well as neo-adjuvantly for down-staging, or for palliation.

To examine the efficacy of the low-molecular-weight heparin, reviparin, for prevention of femoropopliteal stent restenosis.Forty-two patients who had implantation of flexible tantalum stents for the treatment of stenosis (n = 24) or occlusion (n = 18) of the femoral (n = 27) or popliteal (n = 15) arteries were included in this study protocol. An intraarterial bolus of 5000 IU heparin was given before percutaneous transluminal angioplasty (PTA), and in the case of stent implantation due to unsuccessful PTA, an additional dose of reviparin (3500 anti-factor Xa IU) was given. Postprocedurally, 10,500 anti-factor Xa IU of reviparin were administered intravenously over 24 hr, followed by 3500 anti-factor Xa IU subcutaneously twice a day for 23 days. Oral aspirin (100 mg/day) was prescribed for the long term. Follow-up criteria (maximum follow-up 37 months) were clinical symptoms, Doppler ankle arm indices, color and duplex sonography, and angiography for suspicion of restenosis.Early stent thromboses were not observed. Overall primary patency rate (PPR) was 88% +/- 6.0% (1 year) and 74% +/- 10.1% (2 years). Major hemorrhagic complications have not occurred.Reviparin administered in a high dose over a period of 24 days is a safe medication regimen and provides excellent patency rates after stent implantation.

To assess the technical success rate, complications, and effect on intraoperative blood loss of preoperative transarterial embolization of cervical spine tumors.A retrospective analysis was performed on 38 patients with tumors of the cervical spine; 69 vertebrae were affected. Polyvinyl alcohol particles, coils, gelfoam particles, either alone or in combination, were used for preoperative tumor embolization. After embolization a total of 57 corporectomies with titanium basket implantation were performed.In 36 of 38 patients, complete (n = 27) or partial (n = 9) embolization was achieved. In 23 patients one vertebral artery was completely occluded by coil placement, and in one patient the ipsilateral internal and external carotid arteries were occluded in addition. No neurological complications could be directly related to the embolization, but two postoperative brain stem infarctions occurred. The mean intraoperative blood loss was 2.4 L.Transarterial embolization of cervical spine tumors is a safe and effective procedure to facilitate extensive surgery.

Two hundred patients were treated with tantalum stents, 2 in the aortoiliac bifurcation, 114 in the iliac, and 84 in the femoropopliteal arteries. The indications for stenting were technically unsuccessful percutaneous transluminal angioplasty (PTA) due to arterial recoil, dissection (156 patients), or acute occlusions (15 patients). Long iliac artery occlusions (29 patients) were indications for primary stenting. Life-table analysis revealed a 3-year patency rate of 95% for stented iliac arteries, and a 1-year patency rate of 80% for stented femoropopliteal arteries. Restenosis of the stented femoropopliteal lumen was particularly frequent in stents placed for restenosis following prior PTA (7 of 12 patients), in stents placed into the distal superficial femoral and popliteal arteries (14 of 24 patients), and in stents positioned over a longer than 4-cm artery segment (9 of 16 patients). For the aortic bifurcation and iliac arteries, arterial stenting has proved to be a valuable adjunct to PTA; for femoropopliteal arteries, stenting should be restricted to acute arterial occlusions or severe residual stenosis following PTA.

This chapter addresses the physiology of CSF with particular emphasis upon the dynamic process of communicating hydrocephalus. Utilizing traditional morphological and physiological techniques of histological and ultrastructural analysis (Price et al., 1976; James et al., 1980; Diggs et al., 1986) correlated with autoradiography (Strecker et al., 1973, 1974), radioactive transfer measurements (James et al., 1970, 1972) and cisternography, we have documented certain associated structural and functional abnormalities in communicating hydrocephalus as well as the compensatory and repair mechanisms. Recently we have employed the modality of magnetic resonance imaging (Partain et al., 1988b, c) and its dynamic capabilities (Price et al., 1987) to further the understanding of CSF physiology as it relates to communicating hydrocephalus (Bradley et al., 1986, 1989; Davson et al., 1987).

A 16-year-old female patient with recurrent stenosis after unilateral choanal atresia that had been treated by surgery and laser therapy presented with restenosis 3 weeks after laser resection. As an alternative to repeat surgery, she was treated by balloon dilatation. Four balloon dilatations were performed (three at 4-week intervals and the last after an 8-week interval) over a 4-month period on an outpatient basis. She tolerated the treatment well without any complications. Over a follow-up period of 2 years the choana has remained completely open. The balloon dilatation described in this context here for the first time may be a good alternative to repeated operations in the treatment of recurrent choanal atresia, with minimal stress to the patient.

The central canal of the spinal cord in certain animal species has been shown to be an alternative pathway of cerebrospinal fluid flow in experimentally induced hydrocephalus. Enlargement and increased movement of cerebrospinal fluid in the central canal has been proposed as a compensatory mechanism in hydrocephalus in humans. The central canal of the spinal cord was normal in 5 dogs and 2 primates made hydrocephalic by a relatively atraumatic experimental model which simulates the human disorder to chronic communicating hydrocephalus. Dilatation of the central canal is apparently not an important compensatory alternative pathway.

After induction of communicating hydrocephalus in 5 primates and 30 dogs, auto-radiographs following a slow intraventricular infusion of 131I albumin demonstrated marked transependymal radiopharmaceutical migration in these animals to a much greater extent than in normal subjects.

In order to study the effects of the commonly employed contrast media alone and in combination with bacteria in the mediastinum, various mixtures of barium and meglamine diatrizoate (Gastrografin) with and without flora were instilled in the mediastinum of 29 domestic cats. The animals were killed for pathological studies at serial time intervals following mediastina injection. These data demonstrate that water-soluble contrast media cause no significant histological reaction. Barium causes granuloma formation but has no additional deleterious effects when mixed with flora. Barium has superior physical properties of mucosal coating and radiographic density. It should be employed as the contrast agent of choice in difficult clinical problems with regard to esophageal tears. A water-soluble contrast study of the esophagus may be utilized as the initial diagnostic procedure, but if this is normal a follow-up barium esophagram is recommended.

Die Antwort des Liquordruckes auf Erhohung der arteriellen Kohlendioxydspannung wurde bei 5 Kontrollhunden und 7 Hunden mit experimentellem kommunizierendem Hydrocephalus untersucht. Wahrend der Erhohung der arteriellen CO2-Spannung steigt beim Versuchstier mit experimentellen kommunizierenden Hydrocephalus der Liquordruck bis zu 60 mm Hg an, bei den Kontrolltieren hingegen sind nur Liquordruckanstiege bis zu 35 mm Hg nachweisbar. Daraus resultiert beim Hydrocephalus eine erhebliche Verminderung des cerebralen Perfusionsdruckes. Das Fortschreiten eines Hydrocephalus kann einerseits durch erhohten Gewebsdruck und andererseits durch begleitende Anoxie durch Minderdurchblutung wahrend spontan auftretender Liquordruckschwankungen bedingt sein.

Recent communications have related the diagnosis of small bowel intussusceptions to abnormal accumulations of the radiopharmaceutical /sup 99m/Tc pertechnetate on abdominal scans. Considering the pathophysiological alterations attendant to intussusceptions, we have attempted an experimental model to examine these changes in temporal sequence. This study was initiated to understand the etiology better and to characterize the abnormalities noted on the /sup 99m/Tc pertechnetate abdominal scans.

The movement of radioactive labelled albumin (RISA) after intraventricular or intrathecal injection from the cerebral ventricular system into the brain parenchyma has been observed in six dogs with experimental communicating hydrocephalus as well as in a control group. Autoradiography with determination of grain counts per brain-tissue unit was performed to obtain the relation of radiopharmaceutical tissue-concentration versus distance from the ependymal lining. 4 h after injection there was a significant higher tissue-concentration of RISA in the hydrocephalic than in the control group. The distribution in normal animals appears to be consistent with diffusion into the extracellular space of the brain; whereas in hydrocephalic animals intracerebral bulk flow with alteration of the cerebrospinal fluid-brain barrier is suggested.

A model designed to produce chronic communicating hydrocephalus in dogs has been developed in our laboratory. The animals tolerate the procedure well and the yield of animals with communicating hydrocephalus is high. Serial cisternograms show ventricular entry first with “clearing” and later with “stasis”. CSF pressures are initially increased, but when the ventricles become enlarged the pressure falls into the normal range. Grossly there is generalized ventricular enlargement and, on histological studies, the ependyma is flattened and denuded. Periventricular edema occurs in the white matter. Autoradiographs show transependymal movement of protein. CSF production appears to be normal despite obstruction to flow of CSF to areas where resorption is greatest. Diyersionary shunting probably produces relief of many of the neurological symptoms by providing an efficient pathway for the removal of CSF and thus by lessening edema and ventricular enlargement. A more appropriate treatment would appear to be a noninvasive method of decreasing CSF production. Only when the basic pathophysiological altrations of CSF production and absorption are understood will this be possible. We believe that this animal model affords us the opportunity of studying these mechanisms.

Quantitative autoradiography was performed in 6 dogs with chronic communicating hydrocephalus and the results compared with a normal study. Transependymal migration of labelled albumin into the enlarged periventricular extracellular space (ECS) was demonstrated. Graphic representation on probability paper of the radioactivity per unit distance from the ventricular ependyma toward the cortex suggests that diffusion is the mechanism operative in normal animals. In those with communicating hydrocephalus, the character of the graph suggests facilitated diffusion.

The response of cerebrospinal fluid (CFS) pressure to increased arterial carbon dioxide tension (Pco2) was evaluated in 5 control animals and 7 animals with experimentally induced communica

The authors describe a simple catheter technique for the production of communicating hydrocephalus by altering cerebrospinal fluid absorption in the parasagittal region. This method should prove to be of value in understanding the alterations of CSF absorption in communicating hydrocephalus.

Transfer of radioactively labelled albumin from the cerebrospinal fluid (CSF) to the blood was monitored in 15 dogs with normal cisternograms and in 8 dogs with induced communicating hydrocephalus. Blood concentration curves alone are of limited value and give less than satisfactory information about CSF distribution spaces and were corrected for albumin disappearance from the blood to other compartments. The transit time in animals with hydrocephalus was much greater than in normals and entry into the intravascular compartment was delayed. Mathematical analysis to the indicator movements appears to offer understanding about CSF compartments and transfer of molecules in different types of hydrocephalus.

There is a basic alteration in cerebrospinal fluid (CSF) movement and absorption with the development of chronic communicating hydrocephalus. The transfer of radioactive albumin from the CSF space into the blood is delayed. — Ventricular entry associated with persistence (“stasis”) of the radiopharmaceutical corresponds with the syndrome of normal pressure hydrocephalus (NPH) and in clinical improvement with CSF diversionary shunts. As demonstrated by autoradiographic investigations the concentration gradient of radioactivity from the ependymal surface to depth in the periventricular area supports the concept that transependymal migration is an important mechanism of egress of CSF from the CSF space in communicating hydrocephalus.

The cisternograms and pneumoencephalograms of 58 patients with suspected “normal pressure” hydrocephalus were correlated and the relationship of ventricular radiopharmaceutical entry and stasis to ventricular size was analyzed. It was found that radiopharmaceutical entry relates directly to ventricular size, stasis occurring only in markedly enlarged ventricles. Cerebrospinal fluid imaging alone is a highly reliable diagnostic study only if patients exhibit the characteristic cisternographic patterns of normal pressure hydrocephalus. In those who do not, pneumoencephalography and cisternography are valuable complementary studies which can also be used to identify primary cortical atrophy.

✓ The central canal of the spinal cord has been proposed as a significant compensatory alternative pathway of cerebrospinal fluid (CSF) flow in hydrocephalus. Ten dogs were made hydrocephalic by a relatively atraumatic experimental model that simulates the human circumstance of chronic communicating hydrocephalus. The central canal was studied by histopathology and compared with 10 normal control dogs. In both groups the central canal of the spinal cord was normal in size, configuration, and histological appearance. In this experimental model dilatation of the canal and increased movement of CSF does not appear to be a compensatory alternative pathway.

The common duct was ligated in 25 dogs, 5 of which served as controls. Serum bilirubin, GOT, GPT, and alkaline phosphatase were measured pre- and postoperatively. Eight days later, in 10 dogs, a longitudinal incision was made across the stenosed segment of the common bile duct, which was then widened with a Teflon® patch. In 10 other dogs, the stenosis was resected and the defect was bridged with a Teflon® prosthesis. A few days later, laboratory parameters returned to normal. Histological examination after 4 weeks showed that the Teflon® patch and Teflon® prosthesis were lined with bile duct epithelium. X-ray studies 6, 12 and 24 months after repair showed no evidence of stenosis. We conclude that it is possible to use a Teflon® graft in reconstructive common bile duct surgery.

Chronic communicating hydrocephalus was produced in adult dogs by injection of silastic into the subarachnoid space. Electron microscopy was used to verify the sequence of pathologic changes in the ventricular wall. The pathologic findings were correlated with cisternographic images and measurements of cerebrospinal fluid (CSF) pressure. Early in hydrocephalus, the CSF pressure was increased and cisternograms showed ventricular entry and clearing; the ependyma was stretched and fluid accumulated in subependymal regions. In animals with chronic hydrocephalus, the CSF pressure was normal and cisternograms disclosed radioactivity persisting in the ventricles. At this time the ependyma was severely damaged, the subependymal white matter showed enlargement of the extracellular space, and degenerative changes were present in axons and myelin sheaths.

Much is known about the mechanisms of production and absorption of cerebrospinal fluid (CSF), but there remains little general agreement regarding the specifics of these physiological phenomena.10 In this chapter, the authors will discuss CSF physiology from the bias of the diagnostic imaging studies employed in evaluating hydrocephalus and from a series of experiments utilizing animal models developed by our laboratory.29,33,38,39