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PubMed1990

A model for the mechanism of optic nerve sheath fenestration.

The mechanism by which optic nerve sheath fenestration relieves papilledema associated with increased intracranial pressure has not been clearly defined. A model was constructed to determine if the induction of fluid flow along the nerve sheath and through the fenestration could account for a reduction in pressure around the optic nerve, as might be expected according to Bernoulli's equation of fluid dynamics. The model states that as the velocity of a fluid increases, the pressure it exerts decreases. The model simulated fluid spaces corresponding to the intracranial vault, chiasm, and optic nerves. The unfenestrated model showed direct transmission of elevated intracranial pressure to the nerves, consistent with the production of papilledema. When one nerve was fenestrated, fluid flow along the nerve was initiated and pressure in that nerve sheath dropped substantially. In addition, pressure in the unfenestrated sheath dropped due to fluid communication across the chiasm. These lower intrasheath pressures were consistent with the bilateral resolution of papilledema after unilateral fenestration. The reduced intrasheath pressures persisted even when the intracranial pressure was again elevated to pathologic levels as long as active fluid flow continued along the nerve sheaths. Thus, induction of cerebrospinal fluid flow along the optic nerve sheath by fenestration appears to locally reduce the pressure around the optic nerve, in spite of persistently elevated intracranial pressure. This is in accordance with what would be predicted by Bernoulli's equation.

Cerebrospinal Fluid↗

PubMed1992

Neuroimaging of the optic nerve after fenestration for management of pseudotumor cerebri.

The mechanisms by which optic nerve-sheath fenestration is effective remain speculative. Possibilities include surgical production of a cerebrospinal fluid filtration outlet or scarring in the subarachnoid space around the nerve in the vicinity of the fenestration site, with shifting of the pressure gradient from the nerve head to the retrobulbar portion. Two patients who underwent successful optic nerve-sheath fenestration developed a cystlike structure contiguous to the fenestration site, apparently in direct communication with the optic nerve sheaths. This was shown on magnetic resonance imaging (one patient) and orbital echography (both patients). These previously unreported observations may support the hypothesis that fenestration works by creating a filtration apparatus that controls the intravaginal pressure in the subarachnoid space surrounding the orbital segment of the optic nerve.

Adult↗

PubMed2003

Duration of patency of laser-assisted tympanic membrane fenestration.

BACKGROUND: Laser-assisted tympanic membrane fenestration (LTMF) provides intermediate-duration middle ear ventilation, which benefits selected children with acute otitis media (AOM) and otitis media with effusion (OME). OBJECTIVE: To evaluate clinical and technical factors that may affect duration of LTMF patency. DESIGN: Prospective clinical cohort effectiveness trial. SETTING: Four tertiary care children's hospitals. PATIENTS: Volunteer sample of 251 children (430 ears) followed up at 1, 2, 3, 4, 8, and 12 weeks; time to fenestration closure was evaluable in 201 ears, and assessment of cure at study conclusion was evaluable in 128 ears. INTERVENTIONS: Laser-assisted tympanic membrane fenestration for prospectively defined AOM or OME. The surgeon determined spot size, wattage, and concurrent adenoidectomy based on clinical judgment. MAIN OUTCOME MEASURES: Cure of AOM/OME with effusion at 90 days and duration of LTMF patency relative to spot size (1.8-2.8 mm), fenestration location on tympanic membrane, power (7-22 W), concurrent adenoidectomy, age, diagnosis (AOM vs OME), type of effusion, and preoperative tympanogram characteristics. Results are based on the number of ears that could be evaluated at each data collection interval. RESULTS: Fenestrations remained patent for 2 to 4 weeks (mean = 2.52, median = 2.0, SD = 1.4, n = 201); 97.4% were closed at 6-week follow-up. Spot sizes of 2.4 and 2.6 mm had a higher rate of patency than 2.0-mm spot size at 3 weeks following LTMF. Cure at 90 days was related to duration of patency for all patients combined and for patients treated for AOM and OME, but not for those undergoing adjunctive adenoidectomy. Cure at 90 days was related to larger spot size for all patients combined and those treated for AOM. Other investigated factors did not achieve statistical significance. CONCLUSIONS: Spot size of 2.4 mm or greater results in improved duration of LTMF patency, persisting for up to 3 weeks after LTMF, especially for treatment of AOM. Increased duration of LTMF patency correlates with greater incidence of cure of middle ear effusion at 90 days. Additional investigation is indicated to determine optimum spot size and optimum duration of patency for disease- severity-adjusted populations.

Acute Disease↗

PubMed1990

Fenestration revisited. A safe and effective procedure for descending aortic dissection.

Although it was initially performed in 1935, aortic fenestration has been infrequently employed and reported in recent years. We have continued to use fenestration for descending aortic dissection with complicating organ ischemia (lower-extremity ischemia, renal ischemia, and paraplegia). Our technique involves complete transection of the infrarenal abdominal aorta, removal of a generous intimal flap proximally, and reconstitution of layers distally. We report our experience with 12 patients, all of whom survived the operative procedure. Nine patients were discharged from the hospital, and with a mean follow-up of 6.8 years, 7 are still alive. Fenestration immediately restored organ perfusion in all but 1 of the patients, and no patient died of late rupture. We recommend fenestration for descending aortic dissection in patients presenting with organ ischemia. Fenestration is not recommended for acute dissection with rupture or for chronic enlarging dissection.

Adult↗

PubMed1988

Basal lamina fenestrations in the human colon: transmission and scanning electron microscope study.

Basal lamina at the interface between colonic epithelial cells and the lamina propria was exposed by incubating colonic specimens in 1% boric acid solutions. Examination of this epithelial-stromal interface by scanning electron microscopy (SEM) showed a smooth, slightly undulating basal lamina covering crypts and luminal surfaces. The basal lamina on the luminal surfaces had numerous round or ovoid fenestrations, most measuring 2.5-4.0 microns. These were continuous with channels in the collagen fiber network of the lamina propria. Except very near the surface, no fenestrations were found in the basal lamina lining the crypts. Transmission electron microscopy (TEM) of serial thin sections of colonic mucosa without the epithelial cells removed showed only a few actual basal lamina fenestrations. Rarely, epithelial cell processes extended into the lamina propria through the basal lamina. Most of the fenestrations seen by SEM appeared to correspond spatially by TEM to foci of close contact between the basal lamina and underlying fibroblastic cell processes. At these sites the basal lamina and fibroblastic cell process might be removed along with the overlying epithelial cells during processing with boric acid. These data support functional differences in epithelial-stromal interaction between cell populations lining the luminal surface and those making up the crypt lining and pericryptal fibroblast sheath. The TEM findings demonstrate that the human colonic basal lamina is not absolutely continuous and that the development of basal lamina fenestrations and epithelial cell processes extending into the lamina propria is not pathognomonic of neoplastic transformation and stromal invasion.

Colon↗

PubMed1996

Laparoscopic fenestration in polycystic liver disease.

Sixteen laparoscopic cyst fenestrations for symptomatic adult polycystic liver disease (APLD) were performed in 13 women, including four patients who had had previous attempts at treatment (percutaneous sclerotherapy in two and fenestration via a laparotomy in two). The median number of cysts deroofed was 32 (range 18-58) during the 13 primary procedures. There was no in-hospital death. Postoperative transient ascites occurred in six patients. After operation 11 patients experienced immediate relief of symptoms but during a median follow-up of 26 (range 6-49) months, eight of these patients developed recurrent symptoms. Two patients underwent three repeat laparoscopic fenestrations, at which time perihepatic adhesions were rare and no complication occurred. Because repeat procedures may be performed, laparoscopic fenestration appears to be useful for the treatment of symptomatic APLD. However, it is less effective than fenestration at open surgery or liver resection and should be employed only in patients with predominantly large cysts.

Adult↗

PubMedDate not supplied

Alterations in endothelial fenestrations in liver sinusoids of baboons fed alcohol: a scanning electron microscopic study.

The effects of chronic alcohol consumption on the ultrastructure of endothelial fenestrations in liver sinusoids were studied by scanning electron microscopy in surgical liver biopsies of 16 baboons pair-fed with nutritionally adequate diets containing alcohol or isocaloric carbohydrate for up to 112 months. Alcohol consumption for 4 to 24 months resulted in a decreased number of fenestrations (1.4 per micron 2 of the endothelial surface vs. 3.3 in pair-fed controls; p less than 0.01) and an increase in their geometric mean diameter (115.6 vs. 82.3 nm in controls; p less than 0.001). After 61 to 112 months of alcohol feeding, the number of fenestrations was 1.9 (vs. 4.6 in controls; p less than 0.005) and the fenestration diameter was 91.8 nm (vs. 76.7 nm in controls; p less than 0.01). The fractional areas occupied by the fenestrations on the endothelial surface of the sinusoids in baboons fed alcohol for 4 to 24 and 61 to 112 months were calculated to be 84 and 58% of their respective controls. The alterations in the sinusoidal endothelium revealed in this study are most likely associated with a disturbance in the exchanges between the sinusoidal blood stream and the liver parenchyma and may thereby contribute to alcohol-induced liver injury.

Alcoholism↗

PubMed2006

Optic nerve sheath fenestration with endoscopic accessory instruments versus the free electron laser (FEL).

BACKGROUND AND OBJECTIVE: The free electron laser (FEL) can efficiently produce an optic nerve sheath fenestration using an endoscopic approach. To develop a surgical protocol, this study compared effectiveness of available accessory endoscopic instruments to endoscopic FEL delivery effectiveness in producing optic nerve sheath fenestrations. STUDY DESIGN/MATERIALS AND METHODS: An endoscope was used to perform optic nerve sheath fenestrations on goat optic nerves. Accessory endoscopic instruments and glass-hollow waveguides (250 and 320 microm in diameter) were inserted into the instrument channel for comparison. FEL energy (6.45 microm, 30 Hz) was delivered to the tissue through the waveguides and histological analysis was performed. RESULTS: The endoscopic instruments alone were unable to incise the optic nerve sheath. The FEL successfully incised the sheath and the biopsy forceps extricated the circular flap. CONCLUSIONS: Endoscopic optic nerve sheath fenestration using FEL energy followed by biopsy forceps for sheath extrication produced good results, thereby creating a feasible protocol for optic nerve sheath fenestration.

Animals↗

PubMed1985

Fenestrations of the basal lamina of intestinal villi of the rat. Scanning and transmission electron microscopy.

Fenestrations of the basal lamina of rat intestinal villi were revealed by scanning electron microscopy after removal of the overlying epithelial cells by osmic acid maceration. These fenestrations are circular to oval in shape and are 0.5 micron to 5 microns in diameter. They are richly distributed at a density of 1-2 X 10(4)/mm2 in the upper two thirds of the villi, except at the very tips. Roughly 500 fenestrations are found on each side of an average sized tongue-shaped villus. Transmission electron-microscopic observations showed that these fenestrations were passages for migrating cells of the immune system such as lymphocytes, eosinophils and macrophages. Protrusions from the basal parts of epithelial cells were also observed passing through these fenestrations. These findings are discussed with respect to their immunological implications and to the passage of nutrients.

Animals↗

PubMed1986

The cell surface of a restrictive fenestrated endothelium. II. Dynamics of cationic ferritin binding and the identification of heparin and heparan sulfate domains on the choriocapillaris.

The location and chemical composition of anionic sites on the endothelium of the choriocapillaris was investigated with cationic ferritin and enzyme digestion techniques. Cationic ferritin administered intravenously initially labeled essentially all fenestral diaphragms. Within 30 min after injection, no diaphragms remained labeled, but they could be relabeled by a second cationic ferritin injection. Following perfusion of cationic ferritin, the entire luminal front of the endothelium was labeled: the plasmalemma and fenestral, vesicle, and channel diaphragms. Perfusion of neuraminidase or chondroitinase did not affect subsequent cationic ferritin binding. In contrast, heparitinase removed anionic sites on all structures except fenestral diaphragms. Cationic ferritin did not mark the endothelium following heparinase digestion. All sites were cleaved with pronase E. These results indicate that heparin is the anionic moiety on fenestral diaphragms while the glycocalices of the plasmalemma and vesicle and channel diaphragms are rich in a heparan sulfate proteoglycan. Furthermore, since the heparan sulfate localized to these structures was digested by both heparinase and heparitinase, it is in a form similar to heparin. These findings demonstrate that the endothelium of the choriocapillaris bears cell-surface anionic components that are different than those described for fenestrated endothelia lining other vascular beds.

Animals↗

PubMedDate not supplied

Fenestration in extracardiac conduits in children after modified Fontan operation by implantation of stent grafts.

Three patients (ages 3, 5, and 8 years) with various forms of functionally univentricular heart lesions received a total cavopulmonary connection with an extracardiac conduit as a final reconstructive procedure. Failure of the Fontan circulation occurred immediately after surgery because of spontaneous closure of surgical fenestrations in two children and absent fenestration in one. As an emergency procedure, in all patients the conduit was perforated by transcatheter intervention in order to create a connection to the anatomical right atrium. Following balloon dilatation of the perforated conduit, in all three patients covered stent grafts were placed in the newly created defect to attain a reliable communication. Patency of the fenestration was demonstrated by angiogram and any leakage was ruled out. Cardiac output improved and severe pleural effusion and ascites subsided. Right-to-left shunt could be demonstrated by echocardiography at follow-up after 7 months (median) in all three patients. Oxygen saturation remained stable between 85 and 90%. These preliminary results suggest that stent graft fenestration can serve as a valuable tool in failing Fontan circulation, particularly in patients with an extracardiac conduit. Covered stents have the potential to reduce the acute risk of bleeding and they help to prevent early spontaneous closure of the newly created fenestration.

Blood Vessel Prosthesis Implantation↗

PubMed2001

Laparoscopic fenestration of posttransplant lymphoceles.

BACKGROUND: A lymphocele is a common finding after renal transplantation and occurs in up to 20% of patients. The majority of patients are asymptomatic. However, once a lymphocele has become symptomatic (e.g., through transplant dysfunction) this condition has to be treated. We report our 9-year experience with laparoscopic lymphocele fenestration and discuss the current management options for posttransplant lymphoceles. METHODS: Since 1993, 19 patients (11 males and 8 females; median age 56 years, range 22-68 years) of a total of 31 patients with a symptomatic posttransplant lymphocele have undergone laparoscopic fenestration of their lymphocele at a median of 66 days (range, 19-111 days) following successful renal transplantation in our department. As a first-line treatment, a percutaneous pigtail drainage catheter was inserted in all patients. In case of failure in resolving the fluid collection, the next step included sclerotherapy by instillation of tetracycline or ethanol into the lymphocele cavity in some cases. In patients with a persistent lymphocele, a laparoscopic lymphocele fenestration via a transabdominal approach was undertaken to achieve adequate drainage. RESULTS: Primary laparoscopic lymphocele fenestration was successful in all except two patients, who required a conversion. The median operating time was 36 min (range, 20-70 min). Following the procedure, renal transplant function remained stable or returned to individually normal levels in all patients. Median duration of hospital stay was 4 days (range, 1-13 days). At median follow-up of 27 months, all patients were alive with a functioning transplant. CONCLUSIONS: Laparoscopic lymphocele fenestration is reserved for patients in whom temporary drainage with or without sclerotherapy failed to resolve the fluid collection. In these cases the laparoscopic approach offers obvious technical and clinical advantages compared to open operative techniques.

Adult↗

PubMed2003

Risk for laparoscopic fenestration of liver cysts.

BACKGROUND: Laparoscopic fenestration is considered the best treatment for symptomatic simple liver cysts. Conversely, the laparoscopic approach for the management of hydatid simple liver cysts is not widely accepted because of the risk for severe complications. Despite improvement in imaging techniques, the probability of preoperatively mistaking a hydatid liver cyst for a simple liver cyst remains about 5%. Therefore, laparoscopic fenestration, planned for a liver cyst could be performed unintentionally for an undiagnosed hydatid liver cyst. METHODS: From January 2000 to January 2001, 15 patients with a diagnosis of liver cyst underwent laparoscopy for fenestration. In all cases preoperative serologic and imaging assessment had excluded hydatid liver cyst. To further exclude hydatid liver cyst, preliminary aspiration of the cyst with assessment of cystic fluid characteristics was performed. RESULTS: In two patients with presumedly simple liver cyst, hydatid liver cyst was diagnosed instead at laparoscopy by aspiration of cystic fluid. The procedure was converted to laparotomy with subtotal pericystectomy. CONCLUSIONS: The risk of misdiagnosing a hydatid liver cyst for a simple liver cyst, especially in the presence of a solitary cyst, should be considered before laparoscopic fenestration is performed. Intraoperative aspiration of cyst fluid before fenestration can minimize this risk, thus avoiding severe intraoperative and late complications.

Adult↗

PubMed2006

The effects of fenestration of the interpeduncular cistern membrane arousted to the opening of lamina terminalis in patients with ruptured ACoA aneurysms: a prospective, comparative study.

BACKGROUND: The incidence of chronic hydrocephalus requiring shunt placement is a well-known and common complication of aneurysmal subarachnoid hemorrhage (aSAH). It was suggested that fenestration of the lamina terminalis (LT) during microsurgery for aSAH may be associated with a reduced rate of shunt-dependent chronic hydrocephalus (SDCH). We analyzed that, fenestrations of the LT and Liliequist membrane (LM) would reduce rate of SDCH and improve rate of favorable outcome. METHODS: 145 patients who were analyzed in the study were treated in our department with ruptured anterior communicating artery (ACoA) aneurysms. We compared the rate of shunting and clinical outcome in patients in whom only fenestration of the LT (Group 1) was performed with that in patients in whom fenestrations of both the LT and LM (Group 2) were performed. RESULTS: Chronic hydrocephalus requiring shunting amounted to 9.8% (7 patients) in Group 1 and 4% (3 patients) in Group 2 (p=0.203). Also, there were no differences in the rate of shunt dependent hydrocephalus between the two groups in patients with Fisher's CT grades 3 (p=0.343) and 4 (p=0.667), and HH grades 4 (p=0.306) and 5 (p=0.361). Favorable clinical outcomes were observed with rates of 74.6% in Group 1 and 79.7% in Group 2 (p=0.693). Also there were no differences in the rates of favorable clinical outcome between the two groups in patients with Fisher's CT grades 3-4, HH grades 4-5. CONCLUSIONS: Our study shows that fenestration of the LM coupled with the opening of the LT reduced-relatively-the incidence of SDCH; this however was not significant. This positive effect was particularly noticeable in patients in whom a cisternal "overflow" was observed at surgery when opening the LM. This corresponded to cases with ventricular dilatation and a IVth ventricle with clots.

Adult↗

PubMed1983

The use of ligament efficiency to model fenestrations in the internal elastic lamina of cerebral arteries. I--modelling scheme.

The spatial geometry of fenestrations (windows) in the internal elastic lamina from human cerebral arteries is being characterized by a single parameter termed 'ligament efficiency', which is a ratio of the solid band of material to the centre-to-centre spacing between two or more holes. As a result, the apparent random distribution of fenestrations with variable diameters may be represented as a uniform array of holes with a single diameter. The actual arrangement of fenestrations from three separate tissue specimens were replicated in thin latex sheets by transposing the image of the fenestrations from photomicrographs obtained with the scanning electron microscope. In a similar manner, the uniform array of holes with an equivalent ligament efficiency are modelled in latex sheets. The tensile (stress-strain) properties of the latex sheets representing the replication and model configurations were comparable for all three specimens, even though their individual ligament efficiencies were different. The close similarity between the elastic characteristics for the two configurations, verifies the application of ligament efficiency to represent the spatial geometry of a perforated material such as the fenestrated internal elastic lamina.

Biomechanical Phenomena↗

PubMed1995

Cardiac catheterization and test occlusion of the interatrial communication after the fenestrated Fontan operation.

OBJECTIVES: Our objective was to determine whether catheterization data obtained after a fenestrated Fontan operation influenced patient management or predicted functional status. BACKGROUND: Cardiac catheterization after a fenestrated Fontan operation is undertaken to identify residual lesions and to observe the patient's response to test occlusion of the baffle fenestration. METHODS: Sixty patients undergoing both a fenestrated Fontan operation before July 1991 and a postoperative catheterization before March 1992 were included in the study. Catheterization data were collected according to a test occlusion protocol; these data were reviewed, and the patient's clinical status at follow-up was ascertained. RESULTS: Test occlusion resulted in a significant increase in systemic venous pressure, arterial oxygen saturation and arteriovenous difference in oxygen content (p < 0.0001). After test occlusion, systemic venous pressure was 40% higher and systemic venous saturation 23% lower among patients with an unfavorable versus a favorable response to test occlusion, although differences between the two groups were subtle or inapparent in the baseline state. Branch pulmonary artery stenosis (identified and balloon dilated in 6 patients) and grade 2 or 3 aortopulmonary collateral vessels (identified and coil embolized in 20) were associated with elevation in systemic venous pressure (p < 0.01). After an average of 2 years of follow-up, there were no deaths, and 50 (83%) of 60 patients were in New York Heart Association functional class I. The only postoperative characteristic significantly associated with being in functional class I at follow-up was a systemic venous pressure < 17 mm Hg. CONCLUSIONS: Cardiac catheterization with test occlusion of the interatrial communication provides useful information after a fenestrated Fontan operation. Conditions associated with elevated systemic venous pressure should be sought and treated, and the response of systemic venous pressure to test occlusion should be considered when deciding whether to close an interatrial communication.

Cardiac Catheterization↗

PubMed2005

Endothelial vesiculo-vacuolar organelles, pockets and multi-layered fenestrated lamellae in the capillaries of the mouse carotid body.

Fenestrated capillaries represent the basic structural unit in the carotid body. They mediate a characteristic hyperpermeability state in this organ. Endothelial fenestrae and plasmalemmal vesicles are of particular importance in this respect. The present electron microscopic study of the capillaries of the mouse carotid body demonstrates prominent endothelial cell structures that are suggested to be closely related to endothelial fenestrae and plasmalemmal vesicles. These structures include: (1) Vesiculo-vacuolar organelles formed by fusion and intercommunication of vesicles and vacuoles of variable dimensions. (2) Pockets in the form of fenestrated membrane-bound vacuoles that communicate either with the capillary lumen, pericapillary space or both via multiple apertures or fenestrae. (3) Multi-layered fenestrated Lamellae where the endothelial cytoplasm is divided into multiple attenuated sheets provided with several fenestrae. The latter two structures are preferentially located in the thick perinuclear region of the endothelial cell. Their fenestrae are always distributed in linear series and show close similarity to the usual chains of fenestrae in the attenuated periphery of the endothelial cells. The individual apertures of the fenestrated vacuoles and multi-layered fenestrated lamellae are closely similar to the stomata of fully opened plasmalemmal vesicles suggesting a relationship between them. Morphological and morphometrical analysis of a series of fenestrae belonging to these structures revealed that they are identical to the usual chains of fenestrae in the attenuated periphery of the endothelial cells.

Animals↗

PubMed2004

Treatment of short-necked infrarenal aortic aneurysms with fenestrated stent-grafts: short-term results.

INTRODUCTION: A proximal neck of 15 mm length is usually required to allow endovascular repair of abdominal aortic aneurysms (EVAR). Many patients have been refused EVAR due to a short neck. By customising fenestrated grafts to the patients' anatomy, we can offer an endovascular solution, especially for patients who are unsuitable for open repair. METHODS: Eighteen patients were selected for fenestrated stent-grafting if they presented with an abdominal aneurysm of at least 55 mm in diameter, a short neck (less than 15 mm), plus contra-indications for open repair (cardiopulmonary impairment or a hostile abdomen). The stent-graft used was a customised fenestrated model based on the Cook Zenith composite system. We used additional stents to ensure apposition of the fenestrations with the side branches. RESULTS: All endovascular procedures were successful. Out of the 46 targeted side branches (10 superior mesenteric arteries, 36 renal arteries), 45 were patent at the end of the procedure. One accessory renal artery became occluded by the stent-graft. There was one possible proximal type I endoleak, which later proved to be a type II endoleak. There was no mortality, but complications occurred in six patients: two cardiac complications, three urinary complications and one occlusion of a renal artery. At follow-up (mean 9.4 months, range 1-18), there were no additional renal complications and all the remaining targeted vessels stayed patent. DISCUSSION: By customizing fenestrated stent-grafts, it is possible to position the first covered stent completely inside the proximal neck, thus achieving a more stable position. The additional side-stents may also contribute to a better fixation. This technique may become a valuable alternative for patients who are at high risk from open surgery.

Aged↗