Miroslav Vukić

NEW EXPERIMENTAL MODEL OF ACUTE AQUEDUCTAL BLOCKAGE IN CATS : EFFECTS ON CEREBROSPINAL FLUID PRESSURE AND THE SIZE OF BRAIN VENTRICLES

It is generally assumed that cerebrospinal fluid (CSF) is secreted in the brain ventricles, and so after an acute blockage of the aqueduct of Sylvius an increase in the ventricular CSF pressure and dilation of isolated ventricles may be expected. We have tested this hypothesis in cats. After blocking the aqueduct, we measured the CSF pressure in both isolated ventricles and the cisterna magna, and performed radiographic monitoring of the cross-sectional area of the lateral ventricle. The complete aqueductal blockage was achieved by implanting a plastic cannula into the aqueduct of Sylvius through a small tunnel in the vermis of the cerebellum in the chloralose-anesthetized cats. After the reconstitution of the occipital bone, the CSF pressure was measured in the isolated ventricles via a plastic cannula implanted in the aqueduct of Sylvius and in the cisterna magna via a stainless steel cannula. During the following 2 h, the CSF pressures in the isolated ventricles and cisterna magna were identical to those in control conditions. We also monitored the ventricular cross-sectional area by means of radiography for 2 h after the aqueductal blockage and failed to observe any significant changes. When mock CSF was infused into isolated ventricles to imitate the CSF secretion, the gradient of pressure between the ventricle and cisterna magna developed, and disappeared as soon as the infusion was terminated. However, when mock CSF was infused into the cisterna magna at various rates, the resulting increased subarachnoid CSF pressure was accurately transmitted across the brain parenchyma into the CSF of isolated ventricles. The lack of the increase in the CSF pressure and ventricular dilation during 2 h of aqueductal blockage suggests that aqueductal obstruction by itself does not lead to development of hypertensive acute hydrocephalus in cats.

The formation and circulation of cerebrospinal fluid inside the cat brain ventricles: a fact or an illusion?

Formation and circulation of cerebrospinal fluid (CSF) have been studied in the isolated brain ventricles of anesthetized cats by a new approach and under direct observation. A plastic cannula was introduced into the aqueduct of Sylvius through the vermis cerebelli and the outflow of CSF from the cannula was used as the CSF formation and circulation index. During the 60 min of observation at a physiological CSF pressure not a single drop of CSF escaped out of the end of the cannula. This indicates that CSF net formation and circulation inside the brain ventricles, proposed by classical hypothesis regarding CSF dynamics, should be at least re-evaluated.

Effect of osmolarity on CSF volume during ventriculo-aqueductal and ventriculo-cisternal perfusions in cats.

The effect of cerebrospinal fluid (CSF) osmolarity on the CSF volume has been studied on different CSF/brain tissue contact areas. It has been shown, on anesthetized cats under normal CSF pressure, that the perfusion of CSF system (12.96 μl/min) by hyperosmolar CSF (400 mOsml/l) leads to significantly higher outflow volume (μl/min) during ventriculo-cisternal perfusion (29.36 ± 1.17 and 33.50 ± 2.78) than the ventriculo-aqueductal perfusion (19.58 ± 1.57 and 22.10 ± 2.31) in experimental period of 30 or 60 min. Both of these hyperosmolar perfusions resulted in significantly higher outflow volume than the perfusions by isoosmolar artificial CSF (12.86 ± 0.96 and 13.58 ± 1.64). These results suggest that the volume of the CSF depends on both the CSF osmolarity and the size of the contact area between CSF system and surrounding tissue exposed to hyperosmolar CSF. However, all of these facts imply that the control of the CSF volume is not in accordance with the classical hypothesis of cerebrospinal fluid hydrodynamic. According to this hypothesis, the CSF volume should be regulated by active formation of CSF (secretion) inside the brain ventricles and passive CSF absorption outside of the brain. Obtained results correspond to the new hypothesis which claims that the volume of CSF depends on the gradients of hydrostatic and osmotic forces between the blood on one side and extracellular fluid and CSF on the other. The CSF exchange between the entire CSF system and the surrounding tissue should, therefore, be determined by (patho)physiological conditions that predominate within those compartments.

Cervical Disc Replacement With Discover Versus Fusion In A Single Level Cervical Disc Disease: A Prospective Single Center Randomized Trial With A Minimum Two-Year Follow - Up.

Study Design: Prospective randomized study. Objective: To compare the clinical outcome after Discover arthroplasty versus anterior cervical discectomy and fusion (ACDF) in patients treated for symptomatic single-level cervical disk disease. Summary of Background Data: ACDF is still the gold standard for surgical treatment of cervical spine degenerative disk disease. However, results of many studies suggest that it may cause degenerative changes at levels immediately above and below the fusion, known as adjacent segment degenerative disease. Cervical arthroplasty has recently been introduced as an alternative to standard procedure of ACDF. It showed decreased surgical morbidity, decreased complications from postoperative immobilization, and an earlier return to previous level of function. Materials and Methods: A total of 105 consecutive patients with single-level cervical disk disease, producing radiculopathy and/or myelopathy were randomly divided into groups to undergo ACDF or Discover arthroplasty. All patients were evaluated with preoperative and postoperative serial radiographic studies and clinically, using Neck Disability Index, Visual Analog Scale and neurological status at 3, 6, 12, and 24 months. Results: The results of our study indicate that cervical arthroplasty using Discover Artificial Cervical Disc provides favorable clinical and radiologic outcomes in a follow-up period of 24 months. There has been significant improvement in clinical parameters, Visual Analog Scale and Neck Disability Index, at 3, 6, 12, and 24 months in arthroplasty group comparing to control group. Conclusion: The Discover artificial cervical disc replacement offers favorable outcome compared with ACDF for a single-level cervical disk disease at short-term and long-term follow-up.

Spinal contribution to CSF pressure lowering effect of mannitol in cats.

OBJECTIVES After application of hyperosmolar mannitol the cerebrospinal (CSF) pressure is usually lowered within 30 min but this effect cannot be explained either by changes in intracranial blood volume and flow or by changes in brain volume. We assume that this effect of mannitol my be consequence of CSF volume decrease primarily in the spinal CSF due to high compliance of the spinal dura. METHODS To explore such a possibility we planned to separate spinal and cerebral CSF. In chloralose anaesthetized cats dorsal laminectomy of C2 vertebrae was performed and a plastic semi ring was positioned extradurally separating cranial and spinal CSF. CSF pressures were recorded via cannulas positioned in lateral ventricle and lumbar subarachnoid space at L3 vertebrae, respectively. RESULTS After intravenous bolus of 20% mannitol (0.5 or 1.0 g/kg/ 3 min) in control animals without cervical stenosis, the fall of both ventricular and lumbar CSF pressures was equal over time. At 15 min after mannitol application in cats with cervical stenosis an slight increase of ventricular and a fall of lumbar CSF pressures were observed, while at 30 min a gradient of these pressures of 5.5 and 7 cm H2O at lower and higher dose of mannitol, respectively, were registered. However, after removal of cervical stenosis these gradients disappeared. CONCLUSION The observed changes of CSF pressures in spinal and intracranial space indicate that spinal subarachnoid space contributes a great deal to overall fall of CSF pressure and volume in the early period after mannitol application probably due to high compliance of the spinal dura.

The investigation of cerebrospinal fluid formation by ventriculo-aqueductal perfusion method in cats

OBJECTIVES The perfusion of cerebrospinal fluid (CSF) spaces by artificial CSF (aCSF) containing an indicator, is an indirect method used to calculate CSF formation. To evaluate this method, we have developed a ventriculo-aqueductal perfusion method, which enables a direct measurement of CSF formation in the ventricles. METHODS In chloralose anaesthetized cats, the aqueduct of Sylvius was cannulated so that the outflow end of the plastic cannula was positioned extracranially. Both lateral ventricles were also cannulated, with one cannula for infusion of aCSF containing blue dextrane and the other for measurement of CSF pressure. RESULTS During ventriculo-aqueductal perfusion (direct method) under physiological CSF pressure, the outflow rate from aqueductal cannula did not differ significantly from the inflow rate, i.e. no CSF formation was observed. When the indirect method based on dilution of blue dextran in the outflowing perfusate was used, the formation of approximately 5 microl/min of CSF was obtained. CONCLUSION Results of the direct method indicate that net CSF formation inside brain ventricles does not exist. The opposite results obtained by the indirect method questions this method as a reliable study of CSF formation.

Giant cavernoma of the skull and skeletal-extraskeletal angiomatosis associated with paraproteinemia

Skeletal-extraskeletal angiomatosis is defined as a benign vascular proliferation affecting the medullar cavity of the bone and at least one other type of tissue, including skin, subcutaneous tissue, viscera, muscle, or synovium, and which does not spread to avascular tissue such as cartilage. Primary hemangiomas/cavernous hemangiomas (cavernomas) are exceedingly rare in the skull, accounting for 0.2% of all osseous neoplasms and are usually located in frontal and parietal bones. The authors present the case of a 66-year-old man who was admitted with right-side hemiparesis. MRI revealed a destructive bone lesion of the left frontal bone. Digital subtraction angiography of the brain did not reveal pathological vascularization, but a minor submucous hemangioma was seen in the nasal airway. Urine test for Bence-Jones proteins was positive for IgG λ light chain. Bone marrow aspiration and CSF analysis revealed no evidence of systemic myelomatosis suggesting a monoclonal gammopathy of undetermined significance. A highly vascular tumor was surgically removed. The histopathology verified cavernous hemangioma of the skull and the nasal submucous hemangioma. We discuss the diagnostic procedure, possible pathophysiological mechanisms and treatment implementation. It is possible that immunoglobulins from monoclonal gammopathies have an etiologic role in the development of the bone and skin changes in older patients, as an acquired condition, by producing a vascular injury that could lead to the multiple hemangiomas in skeletal-extraskeletal angiomatosis. To prevent misdiagnosis with lesions of other origins, multiple lesions of the head must be resected and histopathologically verified. In conclusion, to the best of our knowledge, this is the first case of giant cavernous hemangioma of the skull associated with paraproteinemia and skeletalextraskeletal angiomatosis limited to the head.

Predictors of functional outcome after spinal ependymoma resection

Aim: Spinal ependymomas are among the most common intramedullary neoplasms in both adults and children. While surgical resection is the golden treatment standard, the role chemotherapy and radiotherapy have in patients with spinal ependymomas remains unclear. The aim of this study is to determine the predictors of functional outcome following spinal ependymoma resection to single out patients that may require adjuvant therapy. Methods: We conducted a retrospective study on patients that underwent spinal ependymoma resection in our institution in a 10-year period. Magnetic resonance imaging of the spine was used to set the diagnosis of an intradural/intramedullary neoplasm. All patients underwent either gross tumor resection or tumor mass reduction. Histological diagnosis and histopathological grading of spinal ependymoma were done for all collected samples. Patients’ general and neurological examination were performed early after the surgery (within the 1st week) and in a 6-month follow-up. Results: A total of 51 intradural and intramedullary ependymoma resection surgeries on 43 patients were performed. There were slightly more male patients (57%) and the average patient age was 41 years. About 76.5% of patients presented with a tumor affecting one vertebrae level, while 23.5% presented with tumors expanding over two or more spinal regions. Gross tumor resection was achieved in 80% of cases, while 25% of procedures were performed on a recurring ependymomas. Most of the tumors (57%) were classified as G2 histological grade, while 8% were anaplastic ependymomas. In 80% of cases, early postoperative patient status was either better or equivalent to the preoperative one, while in a 6-month follow-up, up to 60% of cases showed a significant improvement over the preoperative status. Different demographic and clinical parameters were not proven to be predictors of postsurgical patient outcome including age, gender, and initial neurological presentation. Interestingly, most tumor characteristics were also not associated with postoperative functional outcome (histological grade, number of vertebrae levels affected, whether it is a primary or recurrent tumor). Even the scope of surgical procedure did not affect the functional outcome. The spinal region affected by the tumor was proven to be a predictor of early postoperative outcome (ρ= 0.346, P = 0.033), with lumbar spine being associated with the best outcomes. As expected, the scope of the surgery and whether gross tumor resection or tumor mass reduction was performed were the only significant predictors of tumor recurrence (ρ= 0.391, P = 0.005). Conclusions: Spinal ependymoma resection is an efficient procedure that improves the patient outcomes. Spinal region affected by the tumor is likely to be the most important predictor of functional outcome, while the procedure scope seems to be the most important predictor of tumor recurrence.

Intracranial Epidural Haematoma following Surgical Removal of a Giant Lumbosacral Schwannoma: A Case Report and Literature Review

Postoperative intracranial epidural haematoma (EDH) is an extremely rare complication following spinal surgery, with only a handful of cases described in the literature. We report the case of a 16-year-old girl who underwent a successful subtotal resection of a giant lumbosacral schwannoma (L2-S2 level). Recovery from general anaesthesia was uneventful; however, her neurological status deteriorated rapidly within 24 h after surgery. A head computed tomography scan revealed a large right frontoparietal EDH with midline shift. An immediate frontotemporoparietal osteoplastic craniotomy and evacuation of the EDH were performed. At 1 year postoperatively, the patient regained full neurological recovery with no radiological signs of growth of the residual tumour.

Combined Endovascular and Surgical Treatment of Spinal Dural Arteriovenous Fistulas

Introduction Type I spinal dural arteriovenous fistulas (SDAVFs) are the most common form of spinal vascular malformations. Even so, they are rare and still underdiagnosed. They are low-flow vascular shunts fed by radicular arteries in patients who most often present with myelopathy. Left untreated, they can lead to progressive neurological decline and considerate morbidity. We present our experiences and results in combined endovascular and surgical treatment of such lesions. Material and Methods We conducted a retrospective review of data from 14 adult patients with the diagnosis of SDAVFs who underwent treatment at University Hospital Center Rebro Zagreb between January 2012 and June 2014. We compared complication rates, recurrence rates and data on clinical and imaging follow up in these patients. Results 12 out of 14 patients underwent endovascular embolization (Onyx was used in 1 patients and NBCA in 11 patients) as the first line therapy. Two patients underwent surgical ligation as initial therapeutic modality. Patients in both groups showed significant improvement in clinical status after treatment (using the Aminoff-Logue Scale score). One patient in endovascular group developed spinal infarction due to accidental embolization of posterior spinal artery. Six patients in embolization group had recurrence of fistula during the course of follow up requiring surgical ligation. Two patients in surgical group had recurrence of fistula during the course of follow- up and were reoperated. Conclusion Despite most fistulas are amenable to endovascular embolization, microsurgical obliteration is the treatment of choice in specific anatomic situations and usually the only solution in recurrent cases. A combined approach offers the best results after careful selection of patients based on imaging.