Stand-Alone Percutaneous Pedicle Screw Lumbar Fixation to Indirectly Decompress the Neural Elements in Spinal Stenosis: A Radiographic Assessment Case Series.

BACKGROUND: The ideal surgical treatment of lumbar canal stenosis remains controversial. Although decompressive open surgery has been widely used with good clinical outcome, minimally invasive indirect decompression techniques have been developed to avoid the complications associated with open approaches. The purpose of this study was to evaluate the radiologic outcome and safety of the indirect decompression achieved with stand-alone percutaneous pedicle screw fixation in the surgical treatment of lumbar degenerative pathologies. METHODS: Twenty-eight patients presenting with spinal degenerative diseases including concomitant central and/or lateral stenosis were treated with stand-alone percutaneous pedicle screw fixation. Radiographic measurements were made on axial and sagittal magnetic resonance (MR) images, performed before surgery and after a mean follow-up period of 25.2 months. Measurements included spinal canal and foraminal areas, and anteroposterior canal diameter. RESULTS: Percutaneous screw fixation was performed in 35 spinal levels. Measurements on the follow-up MR images showed statistically significant increase in the cross-sectional area of the spinal canal and the neural foramen, from a mean of 88.22 and 61.05 mm2 preoperatively to 141.52 and 92.18 mm2 at final follow-up, respectively. The sagittal central canal diameter increased from a mean of 4.9 to 9.1 mm at final follow-up. Visual analog scale (VAS) pain score and Oswestry Disability Index (ODI) both improved significantly after surgery (p < 0.0001). CONCLUSION: Stand-alone percutaneous pedicle screw fixation is a safe and effective technique for indirect decompression of the spinal canal and neural foramina in lumbar degenerative diseases. This minimally invasive technique may provide the necessary decompression in cases of common degenerative lumbar disorders with ligamentous stenosis.

Prognostic scoring system for surgical treatment of intramedullary spinal cord metastases.

Although rare, intramedullary spinal cord metastases (ISCMs) are on the rise, most likely due to prolonged survival and improved outcomes as a result of the advances in cancer treatment for cancer patients. While the management of these lesions remains controversial, surgery for ISCM has recently been advocated for selected patients. We performed a retrospective analysis on 30 patients who were surgically treated for intramedullary spinal cord metastases in order to determine a preoperative prognostic scoring system to guide patient selection for surgical interventions. The scoring system was designed to decide between surgery or other therapeutic procedures. The five parameters selected and employed in the assessment system were: 1) patient's general condition, 2) age, 3) primary site of the cancer, 4) number of other extramedullary metastases and 5) severity of neurologic symptoms. Prognosis could not be predicted from a single parameter. These five factors were added together to give a prognostic score between 1 and 10. The average survival period of patients with a prognostic score between 1 and 3 points was 3 months; 11 patients with a score of 4 and 5 points had a mean survival of 7.63 months, while patients with a prognostic score between 6 and 10 was 14.8 months. According to our prognostic scoring system for surgical treatment of ISCM, surgery should be performed in those patients who score above 6 points, while radiotherapy/chemotherapy or palliative care is recommended for those who score between 1 and 3 points. A prognostic score of 4 and 5 represents a grey area where surgeons must use their judgment on whether to intervene either medically or surgically. This scoring system could facilitate decision-making in the management of patients with intramedullary spinal cord metastases.

Use of tissue sealant patch (TachoSil) in the management of cerebrospinal fluid leaks after anterior cervical spine discectomy and fusion.

PURPOSE: The purpose of this study was to evaluate a fast, sutureless technique to repair anterior cervical dural tears. Anterior cervical discectomy and fusion (ACDF) is a commonly performed procedure for the treatment of cervical degenerative diseases. Although uncommon, incidental durotomy with cerebrospinal fluid (CSF) leak during ACDF is a potentially serious complication. Yet, its technical management for the prevention of CSF leak is controversial. METHODS: Between September 2012 and June 2018 we encountered seven cases (2 female/5 male) presenting with intraoperative CSF leaks secondary to incidental dural tears during ACDF surgery. All the cases were surgically treated using a topical fibrin sealant patch (TachoSil) with high adesive strength and fibrin glue (Tisseel). Intraoperative source of leakage, time to leakage control, quantity of Sealant Sponge used and postoperative complications were evaluated. RESULTS: Dural tears were tipically the result of dissection of adherent posterior longitudinal ligament and/or calcified disc from the cervical dural sac to allow full decompression of the spinal cord. Effective repair of dural tear defined as cessation of CSF leak after topical sealant agents application was achieved no later than one minute in all cases. Evident clinical and/or radiological postoperative CSF leak was used to determine the patient's postoperative result. Postoperative CSF leak was not evident during a minimum 6 months follow up. CONCLUSIONS: In the present study, we have reported our experience with a new sealing technique to manage CSF leaks from iatrogenic cervical dural lacerations. Tachosil tissue sealant patch is a rapid sutureless technique that may help in repairing introperatively incidental dural tears, thus reducing the risk of postoperative CSF leaks. To our knowledge, this is the first series to report the use of Tachosil adhesive sealant patch for the treatment of incidental dural tears during anterior cervical discectomy.

Ultrasound-guided Percutaneous Laser Disc Decompression (PLDD) with Fluoroscopic Validation for the Treatment of Cervical Disc Herniation: Technical Note.

OBJECTIVE: Percutaneous laser disc decompression (PLDD) has been regarded as an effective alternative for the treatment of cervical soft disc herniations. Repeated X-Ray scanning is essential when performing this technique. DESIGN: Technical note. METHODS: We present a new method for the treatment of cervical disc herniation using ultrasound to guide the needle entry to the cervical disc, to avoid excess of radiation exposure during the surgical procedure. We evaluated the efficacy of this cervical approach. We retrospectively reviewed the clinical data of 14 cases who underwent a PLDD under ultrasound guidance for the treatment of contained cervical disc herniation using a 1,470 Nm diode laser. The lower cervical discs (C5-C6 and C6-C7) were the most affected sites, accounting for 78.6% of surgical discs. A significant NRS reduction between baseline and 1 month (P = .0002) and between baseline and 12 months (P = .0007) was observed. CONCLUSIONS: Our results support the conclusion that ultrasound guided PLDD with fluoroscopic validation is a minimally invasive technique for patients affected by herniated cervical discs, but proper choice of patients is critical. This approach should not be performed except after adequate training under close supervision of surgeons experienced in this procedure and in interventional US.

Percutaneous Laser Disc Decompression (PLDD) for the Treatment of Contained Lumbar Disc Herniation.

Lumbar disc herniation is a common cause of back and radicular leg pain. A bulging annulus and contained herniated disc can compress a nearby exiting root as it enters the neuroforamen and may cause pain and neurological symptoms. Percutaneous laser disc decompression (PLDD) has been regarded as an effective alternative to microdiscectomy for the treatment of contained lumbar disc herniations. However, there is no consensus regarding the type of laser to use, the ideal wavelength, or the energy applied. The ideal laser irradiation should have a high water absorption coefficient and low tissue pervasion, to limit thermal injury. The 1470 nm wavelength of the diode laser is absorbed by water 40 times more effectively than the 980 nm wavelength. We conducted this study to evaluate the efficacy and safety of PLDD using a 1470 nm diode laser. We retrospectively reviewed the clinical data of 27 patients with radicular pain who underwent PLDD for the treatment of contained lumbar disc herniation during a 12-month period. The 1470 nm diode laser produces smaller local lesions, but greater tissue variations around the nucleus pulposus. This higher affinity for water lessens the formation of a carbonization zone, which results in less thermal injury of the adjacent nervous tissue. According to the MacNab criteria, 85.2% of the cases were improved at 6-month follow-up. Pain decreased from VAS 8.1 preoperatively to VAS 3.1 postoperatively. There is no consensus in the international literature regarding the ideal wavelength. Our results support the conclusion that PLDD using a 1470 nm diode laser is a safe and effective minimally invasive technique for patients with radicular pain affected by contained herniated lumbar discs.

Surgical treatment of solitary intradural extramedullary spinal cord metastases from solid cancers of non-neurogenic origin. A multicenter study.

PURPOSE: Intradural extramedullary spinal metastases (IESM) represent an extremely rare manifestation of systemic cancer. We evaluated the surgical indications, complications and outcome in a series of 43 patients with solitary intradural extramedullary metastases originating from solid cancer of non-neurogenic origin. METHODS: Patients' age, histopathological diagnoses of primary cancer, tumor size, spinal location, and extramedullary tumor dissemination were collected. Preoperative functional status, pre- and post-operative neurological status, extent of the tumor resection were also analyzed. RESULTS: The majority of IEMS occurred in the thoracic area, with the most common presenting symptoms ranging from motor (76.7%) to sensory (72%) deficits. Gross total resection was achieved in 55.8% of cases, while In 44.2% of patients a subtotal resection was performed due to strong adherence between the tumor and neural tissue. After surgery, 72.1% of patients exhibited improvement of symptoms in terms of pain relief and partial recovery of motor and/or sensory deficits, while neurologic functional status was severely affected postoperatively in 3 patients. CONCLUSION: Although there was no statistical significance between the different parameters and overall survival, KPS and the presence of other metastases were the strongest prognostic factors for overall survival and postoperative neurologic outcome.

Functional recovery following resection of large Tarlov cyst malformation: a multicentre longitudinal cohort study.

OBJECTIVE: The authors report their experience with 44 consecutive patients who underwent cyst fenestration and wall repair or cerebrospinal fluid communication closure for the management of sacral Tarlov cysts. METHODS: The procedure was performed on 32 women and 12 men with a mean age of 42 years. Clinical complaints in all patients included lumbar-sacral aching, sphincter dysfunction perineal pain, and sexual intercourse pain. The patients' symptoms had developed within a mean time period of 45 months. Five patients had a previous cyst puncture. In all patients, the cyst was exposed through a sacral laminectomy. In 30 patients, the cyst was partially resected its wall repaired, and in the remaining patients, the cyst was fenestrated, and the cerebrospinal fluid communication was located and tamponaded. Thirty-seven patients had intraoperative EMG monitoring. While the perineal pain, urinary, or sexual dysfunction improved in all patients, eleven patients reported lasting pain control following surgery. The cyst was reduced in all resected cases and seven of 14 patients with CSF tamponade. The mean length of the follow-up period was 57 months. CONCLUSIONS: Either cyst repair or CSF tamponade can be sufficient for alleviating symptoms in patients with Tarlov cyst. Advice should be given to patients regarding expectations for pain improvement after surgery.

Surgical treatment of intramedullary spinal cord metastases: functional outcome and complications-a multicenter study.

Intramedullary spinal cord metastasis (ISCM) is a rare event in the course of advanced malignancy. Management of these lesions remains controversial. Recently, surgery for ISCM has been advocated for selected patients. We performed a retrospective analysis of the clinical course, complications, and outcome of 30 patients surgically treated for ISCM. Patients' age, histopathological diagnoses of primary cancer, tumor size, spinal location, and extramedullary tumor dissemination were collected. Preoperative functional status, pre- and postoperative neurological status, and extent of the tumor resection were also analyzed. Predominant tumor location was thoracic, followed by cervical and conus medullaris. Lung cancer constituted the majority of primary malignancies. In 9 cases, one of the indications for spinal surgery was to obtain a histopathological diagnosis. On admission, all patients presented with neurological symptoms suggestive of myelopathy. After surgery, 18 patients exhibited improvement of symptoms in terms of pain relief and partial recovery of motor and/or sensory deficits; 6 patients were unchanged, while 6 patients exhibited postoperative deterioration. Median survival time after surgery was 9.9 months. Age > 70 years old, presence of systemic metastases, preoperative neurological non functional status, and lung cancer as primary tumor were all factors associated with a worse survival prognosis. This study did not show a clear survival difference between gross total and subtotal ISCM tumor resection. Patients who underwent gross total resection had a worse functional outcome with respect to patients with only partial resection. Gross total resection with low morbidity must be the surgical target, but when not possible, subtotal resection and adjuvant therapy are a valid therapeutic option.

Flow ventricular catheters for shunted hydrocephalus: initial clinical results.

BACKGROUND: The non-homogenous flow of the cerebrospinal fluid within the ventricular catheter is one of the causative factors in shunt obstructions during the treatment of hydrocephalus. Previously, we studied the flow in ventricular catheters under the steady and pulsatile boundary conditions by means of computational fluid dynamics (CFD) in three-dimensional paradigms. Subsequently, several catheter designs with homogeneous flow patterns were developed out of which one prototype was chosen after a validation study. OBJECTIVE: To test the effectiveness of the flow ventricular catheter in a prospective, multicenter, comparative study. METHODS: Eligible centers were three pediatric hospitals: two with sole adult practice and one a mixed pediatric-adult. Standard silicone material was used to develop a parametric catheter model with homogenous flow characteristics. The flow catheters were inserted in pediatric (n = 30) and adult (n = 10) patients with all types of hydrocephalus. Simultaneously, regular ventricular catheters were inserted in another 43 control patients in the participating centers. Catheter positioning was standardized according to the Schaumann and Thomale classification. RESULTS: All ventricular catheters had a cephalad grade I or II positioning, and caudally, its extension had a peritoneal location. Programmable valves were utilized in 70% and antisiphon devices in 20% of the cases. Regular differential pressure valves were utilized in the remaining. No case of flow catheter obstruction was identified during a mean follow-up period of 2 years at the time of this writing. There were four catheter obstructions in the control cohort, all pediatric cases, during the first year. Shunt infections occurred in two cases in the control group, while there was one recurrent case of adult ventriculitis in the flow catheter group. CONCLUSIONS: This prototype model represents the next generation of ventricular catheters with a homogeneous flow pattern. The flow catheter can be inserted safely in hydrocephalic patients, and this preliminary prospective comparative study showed a possible obstruction-free functionality.

Oblique Lateral Retroperitoneal Lumbar Pre-Psoas Approach for Vertebrectomy in Cancer Patients: Surgical Technique.

Due to the longer survival of cancer patients secondary to improved systemic treatments, there has been a recent increase in the incidence of spinal metastases. Metastatic disease involves the anterior vertebral body in 80% of cases. Progressive osseous invasion may result in pathologic vertebral fractures and neural structure compression. Surgical indications are spinal cord and cauda equina compression or spinal instability in patients with an expected survival of at least 6 months. Tumor resection and spine reconstruction in the lumbar region are technically demanding. Several approaches have recently been developed to access the lumbar spine: anterior lumbar approach (ALIF), lateral and extreme lateral transpsoas lumbar approach (LLIF, XLIF, DLIF), and oblique retroperitoneal lumbar pre-psoas approach (OLIF). Each technique has its advantages and drawbacks. OLIF is an emerging procedure that has progressively been used by spine surgeons. The retroperitoneal space allows direct access to the vertebra, thus avoiding injury to the paraspinal muscles, psoas muscle, and lumbar plexus. Between 2005 and 2017, 14 patients underwent somatectomy and spinal reconstruction using an oblique retroperitoneal lumbar pre-psoas approach at our institution. All were affected by lumbar vertebral metastases from solid and hematological tumors, and all presented a Tokuhashi score ≥ 12. L3 vertebral body was involved in 7 cases, L1 was involved in 3, L2 was involved in 2, and L4 was involved in 2. All patients underwent a lateral retroperitoneal approach to achieve vertebrectomy and spinal reconstruction with a cage. Spinal fixation was completed with pedicle screws and rods in 4 cases. No neurological worsening was noted except in one patient who presented a transitory deficit of the left ileopsoas muscle. The oblique retroperitoneal lumbar pre-psoas approach may be a valuable and feasible technique that is potentially able to significantly reduce tissue trauma in patients while still making it possible to achieve corpectomy and solid reconstruction of lumbar vertebral bodies. To our knowledge, this is the first reported series of patients with lumbar spinal metastases treated with the oblique retroperitoneal lumbar pre-psoas approach.

Minimally invasive spinal fixation in an aging population with osteoporosis: clinical and radiological outcomes and safety of expandable screws versus fenestrated screws augmented with polymethylmethacrylate.

OBJECTIVE: The goal of this study was to compare the clinical and radiological outcomes between fenestrated pedicle screws augmented with cement and expandable pedicle screws in percutaneous vertebral fixation surgical procedures for the treatment of degenerative and traumatic spinal diseases in aging patients with osteoporosis. METHODS: This was a prospective, single-center study. Twenty patients each in the expandable and cement-augmented screw groups were recruited. Clinical outcomes included visual analog scale (VAS), Oswestry Disability Index (ODI), and satisfaction rates. Radiographic outcomes comprised radiological measurements on the vertebral motion segment of the treated levels. Intraoperative data including complications were collected. All patients completed the clinical and radiological outcomes. Outcomes were compared preoperatively and postoperatively. RESULTS: An average shorter operative time was found in procedures in which expandable screws were used versus those in which cement-augmented screws were used (p < 0.001). No differences resulted in perioperative blood loss between the 2 groups. VAS and ODI scores were significantly improved in both groups after surgery. There was no significant difference between the 2 groups with respect to baseline VAS or ODI scores. The satisfaction rate of both groups was more than 85%. Radiographic outcomes also showed no significant difference in segment stability between the 2 groups. No major complications after surgery were seen. There were 4 cases (20%) of approach-related complications, all in fenestrated screw procedures in which asymptomatic cement extravasations were observed. In 1 case the authors detected a radiologically evident osteolysis around a cement-augmented screw 36 months after surgery. In another case they identified a minor loosening of an expandable screw causing local back discomfort at the 3-year follow-up. CONCLUSIONS: Expandable pedicle screws and polymethylmethacrylate augmentation of fenestrated screws are both safe and effective techniques to increase the pullout strength of screws placed in osteoporotic spine. In this series, clinical and radiological outcomes were equivalent between the 2 groups. To the authors' knowledge, this is the first report comparing the cement augmentation technique versus expandable screws in the treatment of aging patients with osteoporosis.

A Proposed Intention-to-Treat Anatomical Classification of Spinal Dural Tears.

To clarify outcomes and develop a novel classification according to CSF fistula in a selective cohort with intraoperative spinal dural tear, we examined 72 consecutive patients who underwent spinal dural repair after microdiscectomy (n=42) or lumbar spinal decompression (n=30). Group 1 consisted of 25 patients with Type I (mild) dural tear who were treated with either tissue-glue-coated collagen sponge or fibrin glue. Group 2 consisted of 26 patients with Type II (moderate) dural tear who were treated with both tissue-glue-coated collagen sponge and fibrin glue. Group 3 consisted of 21 patients with Type III (severe) dural tear who were treated with polypropylene suture along with tissue-glue-coated collagen sponge and/or fibrin glue. Evident postoperative internal or external CSF leak was used to determine the patient's postoperative result. Postoperative internal or external CSF leak was not evident during a minimum 1-year follow-up in Group 1. In contrast, internal CSF leak was evident in both Groups 2 (n=3) and 3 (n=3) during the same follow-up. No external CSF leak was noted in any of the patients. Three patients underwent re-do spinal surgery for CSF leak repair. Patients in all groups satisfactorily avoided CSF leak. According to the intraoperative findings of a distinct dural tear, patients can be treated adequately with a specific surgical technique.

Step-by-step Illustration of the Cranial Bifrontal Approach.

Based on experience with several hundreds of adult and pediatric patients in whom the cranial bifrontal approach was used to achieve different surgical objectives, this paper describes this approach in a step-by-step manner with illustrations. This is a basic approach to the anterior cranial fossa that enables the preservation of most bridging veins. The bifrontal approach, whether basal, interhemispheric, or both, allows a wider bilateral operative field with better orientation and views of important neural structures and perforating arteries, without needing to be combined with other approaches. The following description should be regarded as a basic technique to arrive at a definite location within the anterior cranial compartment and beyond, rather than as rigid steps that must be followed rigorously. These illustrations are intended to present essential principles of a standard bifrontal approach. Since the same principles can be followed for every bifrontal approach, this technique along with the surgical results can be constantly improved.

Evaluation and management of small dural tears in primary lumbar spinal decompression and discectomy surgery.

Incidental dural tear is one of the most common intraoperative complications in lumbar spine surgery. Yet, its technical management for the prevention of CSF leak is controversial. The technique of managing dural tears depends on the location of the dural tears as well on the length and anatomical characteristics of the dural tear. We propose an anatomical classification for small (less than one cm) dural tears and report on the outcome of managing these dural tears types using different technique for different type. 62 patients underwent spinal dural repair after microdiscectomy or lumbar spinal decompression. Group 1 consisted of 20 patients, with Type I or mild dural tear who had tissue-glue coated collagen sponge or fibrin glue application. Group 2 comprised 21 patients with Type II or moderate dural tear who had both tissue-glue coated collagen sponge and fibrin glue application. Group 3 comprised 21 patients with Type III or severe dural tear who had polypropylene suture and tissue-glue coated collagen sponge and/or fibrin glue application. Evident postoperative CSF leak was used to determine the patient's postoperative result. Postoperative CSF leak was not evident during a minimum 1 year follow up in group 1. Internal CSF leak was evident in group 2 (n = 3) and group 3 (n = 3) during same follow up. Three patients underwent re-do spinal surgery for CSF leak repair. We recommend different management technique depending on the type of tear. For type I, we recommend the use of tissue-glue coated collagen sponge or fibrin glue application, without dural suturing.

Incidence of thromboembolic events after use of gelatin-thrombin-based hemostatic matrix during intracranial tumor surgery.

Association between the use of hemostatic agents made from collagen/gelatin mixed with thrombin and thromboembolic events in patients undergoing tumor resection has been suggested. This study evaluates the relationship between flowable hemostatic matrix and deep vein thrombosis in a large cohort of patients treated for brain tumor removal. The authors conducted a retrospective, multicenter, clinical review of all craniotomies for tumor removal performed between 2013 and 2014. Patients were classified in three groups: group I (flowable gelatin hemostatic matrix with thrombin), group II (gelatin hemostatic without thrombin), and group III (classical hemostatic). A total of 932 patients were selected: tumor pathology included 441 gliomas, 296 meningiomas, and 195 metastases. Thromboembolic events were identified in 4.7% of patients in which gelatin matrix with thrombin was applied, in 8.4% of patients with gelatin matrix without thrombin, and in 3.6% of cases with classical methods of hemostasis. Patients with venous thromboembolism had an increased proportion of high-grade gliomas (7.2%). Patients receiving a greater dose than 10 ml gelatin hemostatic had a higher rate of thromboembolic events. Intracranial hematoma requiring reintervention occurred in 19 cases: 4.5% of cases of group III, while reoperation was performed in 1.3 and 1.6% of patients in which gelatin matrix with or without thrombin was applied. Gelatin matrix hemostat is an efficacious tool for neurosurgeons in cases of difficult intraoperative bleeding during cranial tumor surgery. This study may help to identify those patients at high risk for developing thromboembolism and to treat them accordingly.

Biosurgical Hemostatic Agents in Neurosurgical Intracranial Procedures.

Intraoperative hemostasis during neurosurgical procedures is one of the most important aspects of intracranial surgery. Hemostasis is mandatory to keep a clean operative field and to prevent blood loss and postoperative hemorrhage. In neurosurgical practice, biosurgical hemostatic agents have proved to be extremely useful to complete the more classic use of electrocoagulation. During recent years, many biosurgical topical hemostatic agents were created. Although routinely used during neurosurgical procedures, there is still a great deal of confusion concerning optimal use of these products, because of the wide range of products, as absorbable topical agents, antifibrinolytics agents, fibrin sealants and hemostatic matrix, which perform their hemostatic action in different ways. The choice of the hemostatic agent and the strategy for local hemostasis are correlated with the neurosurgical approach, the source of bleeding, and the neurosurgeon's practice. In this study, the authors review all the different sources of bleeding during intracranial surgical approaches and analyze how to best choose the right topical hemostatic agent to stop bleeding, from the beginning of the surgical approach to the end of the extradural hemostasis after dural closure, along all the steps of the neurosurgical procedure.

Influence of the hole geometry on the flow distribution in ventricular catheters for hydrocephalus.

BACKGROUND: Hydrocephalus is a medical condition consisting of an abnormal accumulation of cerebrospinal fluid within the brain. A catheter is inserted in one of the brain ventricles and then connected to an external valve to drain the excess of cerebrospinal fluid. The main drawback of this technique is that, over time, the ventricular catheter ends up getting blocked by the cells and macromolecules present in the cerebrospinal fluid. A crucial factor influencing this obstruction is a non-uniform flow pattern through the catheter, since it facilitates adhesion of suspended particles to the walls. In this paper we focus on the effects that tilted holes as well as conical holes have on the flow distribution and shear stress. METHODS: We have carried out 3D computational simulations to study the effect of the hole geometry on the cerebrospinal fluid flow through ventricular catheters. All the simulations were done with the OpenFOAM® toolbox. In particular, three different groups of models were investigated by varying (i) the tilt angles of the holes, (ii) the inner and outer diameters of the holes, and (iii) the distances between the so-called hole segments. RESULTS: The replacement of cylindrical holes by conical holes was found to have a strong influence on the flow distribution and to lower slightly the shear stress. Tilted holes did not involve flow distribution changes when the hole segments are sufficiently separated, but the mean shear stress was certainly reduced. CONCLUSIONS: The authors present new results about the behavior of the fluid flow through ventricular catheters. These results complete earlier work on this topic by adding the influence of the hole geometry. The overall objective pursued by this research is to provide guidelines to improve existing commercially available ventricular catheters.

Parametric study of ventricular catheters for hydrocephalus.

BACKGROUND: To drain the excess of cerebrospinal fluid in a hydrocephalus patient, a catheter is inserted into one of the brain ventricles and then connected to a valve. This so-called ventricular catheter is a standard-size, flexible tubing with a number of holes placed symmetrically around several transversal sections or "drainage segments". Three-dimensional computational dynamics shows that most of the fluid volume flows through the drainage segment closest to the valve. This fact raises the likelihood that those holes and then the lumen get clogged by the cells and macromolecules present in the cerebrospinal fluid, provoking malfunction of the whole system. In order to better understand the flow pattern, we have carried out a parametric study via numerical models of ventricular catheters. METHODS: The parameters chosen are the number of drainage segments, the distances between them, the number and diameter of the holes on each segment, as well as their relative angular position. RESULTS: These parameters were found to have a direct consequence on the flow distribution and shear stress of the catheter. As a consequence, we formulate general principles for ventricular catheter design. CONCLUSIONS: These principles can help develop new catheters with homogeneous flow patterns, thus possibly extending their lifetime.