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Editorial

Anterior third ventriculostomy: an endoscopic variation on a theme

Mark M. Souweidane

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Gerrit Fischer, Jana Rediker and Joachim Oertel

OBJECTIVE

The quality of surgical treatment of intracranial aneurysms is determined by complete aneurysm occlusion while preserving blood flow in the parent, branching, and perforating arteries. For a few years, there has been a nearly noninvasive and cost-effective technique for intraoperative flow evaluation: microscope-integrated indocyanine green videoangiography (mICG-VA). This method allows for real-time information about blood flow in the aneurysm and the involved vessels, but its limitations are seen in the evaluation of structures located in the depth of the surgical field, especially through small craniotomies. To compensate for these drawbacks, an endoscope-integrated ICG-VA (eICG-VA) was developed. The objective of the present study was to assess the use of eICG-VA in comparison with mICG-VA for intraoperative blood flow evaluation.

METHODS

In the period between January 2011 and January 2015, 216 patients with a total of 248 intracranial saccular aneurysms were surgically treated in the Department of Neurosurgery of Saarland University Medical Center in Homburg/Saar, Germany. During 95 surgeries in 88 patients with a total of 108 aneurysms, intraoperative evaluation was performed with both eICG-VA and mICG-VA. After clipping, evaluation of complete aneurysm occlusion and flow in the parent, branching, and perforating arteries was performed using both methods. Intraoperative applicability of each technique was compared with the other and with postoperative digital subtraction angiography as a standard evaluation technique.

RESULTS

Evaluation of completeness of aneurysm occlusion and of flow in the parent, branching, and perforating arteries was more successful with eICG-VA than with mICG-VA, especially for aneurysm neck assessment (88.9% vs 69.4%). For 63.9% of the aneurysms (n = 69), both methods were equivalent, but in 30.6% of the cases (n = 33), the eICG-VA provided better results for evaluating the post-clipping situation. In 4.6% of these aneurysms (n = 5), the information given by the additional endoscope considerably changed the surgical procedure. Thus, one residual aneurysm (0.9%), two neck remnants (1.9%), and two branch occlusions (1.9%) could be prevented. Nevertheless, two incomplete aneurysm occlusions (1.9%) and six neck remnants (5.6%) were revealed by postoperative digital subtraction angiography.

CONCLUSIONS

Endoscope-integrated ICG-VA seems to be an improvement that might increase the quality of aneurysm surgery by providing additional information. It offers higher illumination, magnification, and an extended viewing angle. Its main advantage is its ability to assess deep-seated aneurysms, especially through small craniotomies, but further studies are required.

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Juergen Piek, Joachim Oertel and Michael Robert Gaab

Object. Waterjet dissection represents a new minimally traumatic surgical method for dissection that can be used in various parenchymal organs, in which it allows highly precise parenchymal dissection while preserving blood vessels, resulting in reduced intraoperative blood loss. This study was performed to investigate the clinical application of this new technique in neurosurgical procedures, such as brain tumor resection and epilepsy surgery.

Methods. Thirty-four patients with gliomas (Grades II–IV), cerebral metastases, temporal lobe epilepsy, or cerebellar hemangioblastomas, and one patient with internal carotid artery (ICA) stenosis were treated surgically with the aid of the waterjet. Resection was performed using waterjet dissection in combination with conventional neurosurgical procedures. Intraoperatively, the waterjet was easy to handle, and no complications due to the device were observed. Dissection of tissue was possible for all pathological conditions, and pressures between 3 and 45 bars were used. In gliomas, metastases, epilepsy surgery, and hemangioblastoma, the tissue was dissected at pressures between 3 and 17 bars, which preserved blood vessels. Dissection of meningiomas and the ICA stenosis required higher pressures (between 20 and 45 bars); with these pressures, blood vessels were also dissected.

Conclusions. These results indicate that the waterjet dissection procedure can be used intraoperatively without complications. This device appears to be particularly suitable for the dissection of highly vascularized gliomas or normal brain tissue, in which tissue dissection with sparing of blood vessels can be achieved. To prove that this is a useful addition to the neurosurgical armamentarium, reduction of blood loss or postoperative brain edema compared with conventional methods should be demonstrated in future studies.

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Christoph Tschan, Michael Robert Gaab, Joachim Kurt Krauss and Joachim Oertel

Object

Waterjet dissection has been shown to protect intracerebral vessels, but no experience exists in applying this modality to the cranial nerves. To evaluate its potential, the authors examined waterjet dissection of the vestibulocochlear nerve in rats.

Methods

Lateral suboccipital craniectomy and microsurgical preparation of the vestibulocochlear nerve were performed in 42 rats. Water pressures of 2–10 bar were applied, and the effect was microscopically evaluated. Auditory brainstem responses (ABRs) were used to define nerve function compared with preoperative values and the healthy contralateral side. The final anatomical preparation documented the morphological and histological effects of waterjet pressure on the nerve.

Results

In using up to 6 bar, the cochlear nerve was preserved in all cases. Eight bar moderately damaged the nerve surface. A 10-bar jet markedly damaged or even completely dissected the nerve. Time course analysis of the ABR demonstrated complete functional nerve preservation up to 6 bar after 6 weeks in all rats. Waterjet dissection with 8 bar was associated with a 60% recovery of ABR. In the 10-bar group, no recovery was seen.

Conclusions

Microsurgical dissection of cranial nerves is possible using waterjet dissection while preserving both morphology and function. The aforementioned jet pressures are known to be effective in neurosurgical treatment of tumors. Thus, waterjet dissection may be useful in skull base surgery including dissection of cranial nerves from tumors. Further studies on this subject are encouraged.

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Joachim Oertel, Joachim Kurt Krauss and Michael Robert Gaab

Neuroendoscopic techniques are often considered inapplicable to lesion resection because most lesions are too large for effective endoscopic resection in an appropriate time frame. To evaluate the potential of ultrasonic aspiration in neuroendoscopic procedures, the authors developed a new handpiece for endoscopic application. The instrument was subsequently tested in 10 cadaveric pig brains and applied in 5 clinical cases. In the pig brain, a precise and accurate aspiration of ventricular ependyma and brain parenchyma was obtained. Clinically, the device was applied in 3 patients with obstructive hydrocephalus, and via an endonasal transsphenoidal approach in 2 patients with pituitary macroadenomas. In all cases, the lesion was effectively aspirated without complications. Ultrasonic aspiration can be applied safely and successfully in selected endoscopic procedures. The use of this technique could expand the indications for endoscopic approaches to include intraventricular lesions and in minimally invasive transsphenoidal endonasal approaches.

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Sonja Vulcu, Leonie Eickele, Giuseppe Cinalli, Wolfgang Wagner and Joachim Oertel

OBJECT

Endoscopic third ventriculostomy (ETV) is the procedure of choice in the treatment of obstructive hydrocephalus. The excellent clinical and radiological success rates are well known. Nevertheless, very few papers have addressed the very long term outcomes of the procedure in very large series. The authors present a large case series of 113 patients who underwent 126 ETVs, and they highlight the initial postoperative outcome after 3 months and long-term follow-up with an average of 7 years.

METHODS

All patients who underwent ETV at the Department of Neurosurgery, Mainz University Hospital, between 1993 and 1999 were evaluated. Obstructive hydrocephalus was the causative pathology in all cases.

RESULTS

The initial clinical success rate was 82% and decreased slightly to 78% during long-term follow-up. Long-term success was analyzed using Kaplan-Meier curves. Overall, ETV failed in 31 patients. These patients underwent a second ETV or shunt treatment. A positive impact on long-term success was seen for age older than 6 months, and for obstruction due to cysts or benign aqueductal stenosis. The complication rate was 9% with 5 intraoperative and 5 postoperative events.

CONCLUSIONS

The high clinical success rate in short-term and long-term follow-up confirms ETV’s status as the gold standard for the treatment of obstructive hydrocephalus, especially for distinct pathologies. The patient’s age and underlying pathology may influence the outcome. These factors should be considered carefully preoperatively by the surgeon.

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Joachim M. K. Oertel, Yvonne Mondorf and Michael R. Gaab

Obstructive hydrocephalus due to giant basilar artery (BA) aneurysm is a rare finding, and endoscopic treatment has not been reported. Here the authors present their experience with endoscopic third ventriculostomy (ETV) in obstructive hydrocephalus due to giant BA aneurysm. Between December 2000 and March 2007, 3 patients (2 men and 1 woman; age range 32–80 years) underwent an ETV for the treatment of obstructive hydrocephalus caused by a giant BA aneurysm. All 3 patients presented with cephalgia, nausea, vomiting, and a variable decrease in consciousness. An obstructive hydrocephalus caused by a giant BA aneurysm was found in each case as the underlying pathological entity. Intraoperatively, a narrowing of the third ventricle by upward displacement of the tegmentum was found in all 3 patients. A standard ETV was performed and included an inspection of the prepontine cisterns. The endoscopic treatment was successful in all patients with respect to clinical signs and radiological ventricular enlargement. No complications were observed. In all, the endoscopic ventriculostomy was proven to be a successful treatment option in obstructive hydrocephalus even if it is caused by untreated giant BA aneurysm.

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Henry W. S. Schroeder, Joachim Oertel and Michael R. Gaab

Object. Epidermoid tumors located in the cerebellopontine angle (CPA) are challenging lesions because they grow along the subarachnoid spaces around delicate neurovascular structures and often extend into the middle cranial fossa. The purpose of this study was to determine the value of endoscopic assistance in the microsurgical resection of these lesions, in which total removal is the therapy of choice.

Methods. Eight patients harboring an epidermoid tumor of the CPA were treated using an endoscope-assisted microsurgical technique. A retrosigmoid suboccipital approach was used in five patients and a pterional transsylvian approach was chosen in the other three. In four patients the lesion was resected microsurgically and the endoscope was used repeatedly to verify complete tumor removal, whereas most of the tumor mass was removed with the aid of an operating microscope in the other four. Tumor parts extending into other cranial compartments that were not visible through the microscope were removed under endoscopic view by using rigid rod-lens scopes with 30 and 70° angles of view.

All epidermoids were completely evacuated and the membranes were widely resected. Large tumors occupying both the middle and posterior cranial fossa were removed through a single small opening without enlarging the craniotomy. Permanent hearing loss and permanent hypacusis were observed in one patient each. One patient with facial and one with abducent nerve palsy recovered within 6 and 4 months, respectively. A transient weakness of the chewing muscles was encountered in one patient. Postoperative magnetic resonance imaging revealed no residual tumor in any patient. To date no recurrences have been observed (follow up range 12–98 months).

Conclusions. The endoscope-assisted microsurgical technique enables safe removal even when tumor parts are not visible in a straight line. Tumor extensions into adjacent cranial compartments can be removed with the same approach without retracting neurovascular structures or enlarging the craniotomy.

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Christoph A. Tschan, Elvis J. Hermann, Wolfgang Wagner, Joachim K. Krauss and Joachim M. K. Oertel

Object

Waterjet dissection has been shown to separate tissues of different resistance, with preservation of blood vessels. In cranioplasty, separation of subcutaneous tissue and dura mater is often difficult to achieve because the various tissue layers strongly adhere to each other after decompressive craniotomy. In the present study, the potential advantages and drawbacks of the waterjet technique in cranioplasty after craniectomy and duraplasty are addressed.

Methods

The waterjet effect on fresh human cadaveric dura mater specimens as well as on several dural repair patches was tested in vitro under standardized conditions, with waterjet pressures up to 80 bar. Subsequently, 8 pediatric patients (5 boys, 3 girls; mean age 9.9 years, range 1.2–16.7 years) who had been subjected to decompressive craniectomy (7 with duraplasty including bovine pericardium as a dural substitute, 1 without duraplasty in congenital craniosynostosis) underwent waterjet cranioplasty. The waterjet was used to separate the galea and the dura mater. The technique was applied tangentially between the dura and the galea, with different pressure levels up to 50 bar.

Results

In vitro, fresh cadaveric human dura mater as well as 2 different dural repair substitutes showed a very high resistance to waterjet dissection up to 80 bar. The human dura and the various substitutes were dissected only after long-lasting exposure to the waterjet. Human dura was perforated at pressures of 60 bar and higher. Bovine pericardium dural substitute was perforated at pressures of 55 bar and higher. Artificial nonabsorbable polyesterurethane dural substitute was dissected at pressures of 60 bar and higher. In the clinical setting, the waterjet was able to separate galea and dura with minimal bleeding. No blood transfusion was required. Dissection of scarred tissue was possible by a waterjet of 40 bar pressure. Tissue layers were stretched and separated by the waterjet dissection, and a very reliable hemostasis resulted. This resulted in an effective reduction of bleeding, with < 60 ml blood loss in 7 of the 8 cases. Neither a dural tear nor a perforation of any duraplasty occurred during operative preparation. There were no operative or postoperative complications.

Conclusions

The experimental and clinical data show that waterjet separation of dura mater, dural substitute, and galea can be performed with a high level of safety to avoid dural tears. The waterjet dissection stretches tissue layers, which results in a reliable hemostasis effect. This potentially results in an effective reduction of surgical blood loss, which should be the focus of further studies.

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Gerrit Fischer, Axel Stadie, Eike Schwandt, Joachim Gawehn, Stephan Boor, Juergen Marx and Joachim Oertel

Object

The aim of the authors in this study was to introduce a minimally invasive superficial temporal artery to middle cerebral artery (STA-MCA) bypass surgery by the preselection of appropriate donor and recipient branches in a 3D virtual reality setting based on 3-T MR angiography data.

Methods

An STA-MCA anastomosis was performed in each of 5 patients. Before surgery, 3-T MR imaging was performed with 3D magnetization-prepared rapid acquisition gradient echo sequences, and a high-resolution CT 3D dataset was obtained. Image fusion and the construction of a 3D virtual reality model of each patient were completed.

Results

In the 3D virtual reality setting, the skin surface, skull surface, and extra- and intracranial arteries as well as the cortical brain surface could be displayed in detail. The surgical approach was successfully visualized in virtual reality. The anatomical relationship of structures of interest could be evaluated based on different values of translucency in all cases. The closest point of the appropriate donor branch of the STA and the most suitable recipient M3 or M4 segment could be calculated with high accuracy preoperatively and determined as the center point of the following minicraniotomy. Localization of the craniotomy and the skin incision on top of the STA branch was calculated with the system, and these data were transferred onto the patient's skin before surgery. In all cases the preselected arteries could be found intraoperatively in exact agreement with the preoperative planning data. Successful extracranial-intracranial bypass surgery was achieved without stereotactic neuronavigation via a preselected minimally invasive approach in all cases. Subsequent enlargement of the craniotomy was not necessary. Perioperative complications were not observed. All bypasses remained patent on follow-up.

Conclusions

With the application of a 3D virtual reality planning system, the extent of skin incision and tissue trauma as well as the size of the bone flap was minimal. The closest point of the appropriate donor branch of the STA and the most suitable recipient M3 or M4 segment could be preoperatively determined with high accuracy so that the STA-MCA bypass could be safely and effectively performed through an optimally located minicraniotomy with a mean diameter of 22 mm without the need for stereotactic guidance.