Transendoscopic ultrasound in ventricular lesions.

BACKGROUND: After transendoscopic sonocatheters had been tested in the laboratory for imaging characteristics and practicability, clinical application was studied with special reference to imaging and navigation capabilities, practicability, safety, and preliminary indications. METHODS: Intraoperative ENS images prepared during surgery on 75 selected patients between 1996 and 2005 were examined. There were 35 female and 40 male patients, and their mean age was 42 years (range, 2-69 years). Within this series, there were 28 cases of ventricular lesions (ventricular hematomas, tumors, and colloid cyst included, 35 cases) with different diagnosis. In most cases, Aloka sono equipment (Aloka Deutschland, Düsseldorf, Germany) was used because equipment supplied by this company had yielded superior imaging results in the laboratory. This work with patients differed from the laboratory work in that 2 sizes (diameters) of catheters were used: 6-F catheters for block-shaft endoscopes and 8-F for hollow-shaft endoscopes. RESULTS: Imaging: In clinical use, the sonocatheter has superior imaging and navigation abilities to those seen in anatomical laboratory work. Real-time and online characteristics represent changes such as shifting, pulsation, CSF flow, blood flow, and changes in size and form of structures. When confronted with clinical problems, this technique still has some limitations such as short penetration depth of 3-cm radius and lack of scanning anterior to the endoscope. Navigation: The scan is radial 360 degrees and in an orthogonal plane to the axis of the endoscope. At the tip of the endoscope it delivers an image that looks geometrically like a "brain radar." Because of its real-time characteristic, ENS has a navigation capacity that markedly differs from usual neuronavigation, but is intuitively usable. Endoneurosonography was applied in 8 hydrocephali, 3 colloid cysts, 5 intraventricular hematomas, 1 septostomy, 11 ETVs, 2 cystostomies, 4 multiple cysts, and 1 tumor biopsy cases. Three illustrative cases are presented. CONCLUSION: Endoneurosonography is a tool for intraoperative real-time and online high-resolution imaging, and neuronavigation of endoscopes with a working channel at least 2 mm in diameter; it also has application in a wide variety of ventricular lesions. Endoneurosonography is limited by short penetration depth and not scanning ahead to the endoscope anteriorly.

Endoneurosonography: technique and equipment, anatomy and imaging, and clinical application.

OBJECTIVE: To evaluate the usefulness of transendoscopic ultrasound in neurosurgery, we studied two new sonoprobes measuring 6 and 8 French in diameter in 20 fresh specimens. The application and indication are discussed in the first clinical series of 75 patients. METHODS: Sonocatheters (ALOKA, Meerbusch, Germany) 1.9 mm (6 French) and 2.4 mm (8 French) in diameter were introduced into the working channel of an endoscope. The preparations were done in nonfixed skulls in a surgical simulation-setting laboratory. Based on these experiences with imaging possibilities, intraoperative transendoscopic ultrasound was applied in 75 patients and a variety of lesions. It was used for imaging (41 patients), targeting (18 patients), and neuronavigation (16 patients) in neuroendoscopy. RESULTS: The sonoprobe adds a transverse scan at the tip of the probe to the anterior endoscopic view. This axial scan to the longitudinal axis of the endoscope is geometrically comparable with radar scanning. Three probes working with 10, 15, and 20 MHz were used, resulting in a short penetration with a radius of 3 cm. The orthogonal scanning plane had limitations, which were documented. We observed precise imaging of well known anatomic structures and, moreover, achieved an additional dimension in endoscopy. The axial scan presents the anatomic landmarks like a map at the tip of the endoscope where the endoscope is represented as a spot. The real-time imaging and representation of the tip of the endoscope showed a capacity for navigation. This preclinical study rectified clinical application. The real-time imaging of this technique showed the ability of the navigation of endoscopes to detect more overall movements, such as blood flow or change of ventricle size during endoscopy. The primary benefit in this first clinical series was witnessed in difficult endoscopy cases and complex lesions, but benefit was also observed in cases in which vision through the endoscope alone was obscured. The main limitation was the result of little penetration depth and lack of anterior scanning. CONCLUSION: Application of transendoscopic ultrasound is appropriate in neurosurgery. Training is necessary to understand the imaging and the geometry of scans because this technique does not scan along the axis of the endoscope. Further development to overcome the current limits of this technique and more clinical experience are needed.

Endo-neuro-sonography: first clinical series (52 cases).

OBJECTIVE: A sono catheter for transendoscopic imaging was applied in neurosurgery for the first time in 52 patients with a broad variety of lesions. METHODS: A transendoscopic sono catheter (Aloka Deutschland GmbH, Düsseldorf, Germany) with a diameter of 1.9 mm (6F) was used and introduced into the working canal of an endoscope. The image produced by the probe is a 360 degrees scan ("brain radar") displayed on a monitor, on which some parameters can be varied to get the best view of the different anatomical structures. RESULTS: In 39 patients intraoperative imaging was the main reason for investigation and in 13 patients neuronavigation was the focus of interest. In 18 cases of tumor resection control targeting a visualized remnant was necessary. There are limitations and artifacts, which should reveal themselves in laboratory and clinical experience. CONCLUSION: In this small series, endo-neuro-sonography proved to make neuroendoscopy safer and easier by online and real-time imaging with high resolution.

Postmortem inspection for neurosurgery: a training model for endoscopic dissection technique.

In 63 specimens, 74 aneurysms, and five other lesions, postmortem microsurgical and endoscopic inspection (PMI) was done. This work not only allowed for safe pathoanatomic findings, but moreover showed characteristics of a training method developed according to a model with clear standards. PMI gives training in: 1. Understanding of pathoanatomic topography and syntopy. 2. Analysis of imaging findings. 3. Analysis of approaches (approach planning). 4. Paraendoscopic methods (video surgery). 5. Clipping training. 6. Analyzing the ergonomy of the setting and instrumentation. In the series presented, aneurysms were the focus of attention. Postmortem inspection trains nearly all manipulative and cognitive abilities necessary for operative management of this difficult lesion. The acceptance and applicability of this method for resident training must be evaluated in the future.