Clinical evaluation of the marginal fit of cast crowns--validation of the silicone replica method.

Replication of the space between a tooth and its cast crown, using a light-body silicone supported by a heavy-body silicone, is a recognized technique to evaluate the quality of a restoration. This study validates a similar method that is of great clinical and experimental interest. Whatever the type of silicone used, comparison is possible between different technical procedures of crown elaboration (type of impression, type of material, method of spacing, etc.). If an appropriate silicone is used, the cement space may be reproduced and its thickness measured, whatever the localization (cervical, axial, occlusal).

The computer-assisted localizer, a navigational help in microneurosurgery.

The computer-assisted-localizer (CAL) achieves a direct linkage between preoperative radiological images and individual intraoperative anatomical findings. Experiences with our system demonstrate that CAL improves the intraoperative orientation and facilitates the neurosurgical procedure. The system described here consists of a mechanical articulated robot arm with six degrees of freedom and a three-dimensional image processor. After calibration, the displayed image dynamically pointed out the exact intraoperative localization in three perpendicular sectional views. Meanwhile, CAL was successfully used in 73 selected microneurosurgical procedures.

Frameless neuronavigation in modern neurosurgery.

A fundamental effort in neurosurgery is to reduce surgical trauma. Microneurosurgical technique combined with precise localization of lesions, can minimize the invasiveness of neurosurgical procedures. This report summarizes the utility of frameless neuronavigator systems and examines their value in reducing operative invasiveness. The basic principle of neuronavigation is the virtual linkage between digitized neuroradiological data and real anatomical structures, allowing an excellent three-dimensional orientation by real-time graphic-anatomic interaction. As frameless graphic interactive neuronavigation is developed further, these devices should become an important component of the modern microneurosurgical armamentarium and reduce surgical morbidity.

Computer-assisted image-guided surgery in pediatric skull-base procedures.

Skull-base surgery is characterized by the variety of important neural and vascular structures within a narrow operating field. Although preoperative imaging by computed tomography (CT) and magnetic resonance imaging (MRI) and the use of microsurgical techniques have improved intraoperative orientation, a large number of complications still are caused by localization problems. Especially in pediatric skull-base surgery, maximum localization accuracy during surgery is required. The authors developed a localizing system based on tomographic imaging (such as CT or MRI) to achieve safer surgery by providing highly accurate location information. The preliminary successful experience in the use of the Aachen computer-assisted surgery device for pediatric skull-base surgery (14 cases) is presented. Indication include juvenile angiofibroma of the nasopharynx, infectious and tumorous diseases of the paranasal sinuses, orbital tumors, foreign bodies, and intracranial abscess formation.

Preoperative localization of the central sulcus by dipole source analysis of early somatosensory evoked potentials and three-dimensional magnetic resonance imaging.

Surgery of lesions within or close to the central area of the brain always carries the risk of iatrogenic motor or sensory deficits. Functional localization by means of intraoperative direct stimulation of the motor area or by recording somatosensory evoked potentials (SSEP's) from the surface of the somatosensory cortex is believed to reduce the operative risk. The authors introduce the combination of dipole source analysis of scalp-recorded SSEP's with three-dimensional (3-D) magnetic resonance (MR) imaging as a tool for preoperative localization of the central sulcus. This provides information on both functional and structural localization for preoperative planning. Four repeated measurements of right and left median nerve SSEP's were obtained from 20 subjects. Dipole source analysis showed a retest reliability of the 3-D localization error of 2.9 +/- 2.0 mm. Compared to the MR evaluation, dipole source analysis was found to mark the central sulcus within 3 mm for 15 conditions (subjects x side of stimulation), while the 3-D MR measurement was accurate to within 6 mm for 10 conditions and 9 mm for 14 conditions. Dipole locations were confirmed in six patients who underwent surgery of the central region. With respect to this application, dipole source analysis combined with 3-D MR imaging appears to be a valuable tool for preoperative functional localization. The accuracy in localization will be further improved when realistic head models become available that can take into account individual head geometry. Further development of the proposed new method holds promise that evoked potentials and electroencephalography will gain greater use in presurgical functional localization.

Pterional/Lateral approach to orbital tumors.

The purpose of this article is to detail our experience with an approach to primary pathologic conditions involving the orbit. In 27 patients these included tumors of the lacrimal gland, lymphangiomas, neurinomas, meningiomas, and various cysts of the orbit. Access to these lesions was gained by a lateral pterional approach with osteoclastic or osteoplastic removal of the lateral bony wall/roof of the orbit, and by entering adnexal contents following elevation of the lateral rectus muscle. This approach allowed for complete tumor removal in all patients. The specifics of this approach will be discussed and associated orbital complications will be detailed.

[Nosocomial infections in a neurosurgical intensive care unit]. / Nosokomiale Infektionen in einer Neurochirurgischen Intensivstation.

The occurrence of nosocomial infections in 1017 consecutive patients seen in a neurosurgical intensive care unit (ICU), over a period of 18 months is reported. The frequency of infections is low, which may possibly be due partly to the short stay in the ICU. Close interdisciplinary cooperation is stressed as an important factor in limiting infections. BACKGROUND. The aim of this study was to analyse the nosocomial infections in a neurosurgical intensive care unit over a period of 18 months, emphasizing localization and cause of infection, in order to adapt treatment and to take preventive measures. From 15% to 27% of patients treated in ICUs acquire nosocomial infections. In Germany this means 500,000-800,000 patients a year, and the annual costs related to nosocomial infections are estimated at 1.7 billion Deutschmarks. PATIENTS AND METHODS. In all, 1017 consecutive patients were evaluated. The patients were divided into two groups, depending on the duration of treatment in the ICU: Patients who remained for less than 48 h (1017 patients) Patients who were treated for a period exceeding 48 h (314 patients) The evaluation was performed retrospectively from the medical documentation. Criteria for registration are those of the Centers for Disease Control (Atlanta 1988). When more than one infection was diagnosed, each was considered as a new infection, regardless of the bacteria involved. Among the 314 patients who were in the ICU for more than 48 h a total of 114 nosocomial infections were recorded. The frequency of infection referred to all patients treated during that time (n = 1017) was 11.2%, while the frequency among those who were treated for longer than 48 h was 36.3%. Most infections (38.6%) affected the respiratory tract, followed by infections of the urinary tract. Of the bacteria determined 56.7% were gram-negative. In this group E. coli was the most frequently found (29.8%). In the group of gram-positive bacteria, S. aureus was diagnosed in 56.3% of cases. Twelve (16%) of the infected patients died and lethality referred to all patients was 8.6%. DISCUSSION. Compared with other studies, this study revealed a low the infection rate, at 11.2%. This can be explained partly by the short stay in this ICU (mean 3.7 days) and partly by the retrospective method of registration and the particular medical characteristics of neurosurgical patients. The well-known general risk factors for infection, such as age, mechanical ventilation, continuous catheterization of the bladder, and long duration of stay, are also found in neurosurgical ICUs. It is quite difficult to determine to what extent nosocomial infections prolong the treatment necessitated by the primary neurosurgical disease. We were not able to extrapolate the influence of immunosuppressant treatment on the appearance of nosocomial infections, as almost all patients in this study were receiving steroids. This study underlines the necessity of interdisciplinary cooperation between neurosurgeons, anaesthesiologists, microbiologists and nurses in neurosurgical ICUs, where most patients staying longer than 48 h are immunosuppressed and ventilated and thereby particularly at risk of nosocomial infections.

Frameless stereotactic drainage of intracranial abscesses.

Our preliminary experience is presented in the use of the Aachen Computer-Assisted Surgery device for frameless stereotactic puncture and drainage of intracranial abscesses through a 2.1-mm twist-drill hole. The apparatus and technique are described, along with the results of its use in 2 patients. Intraoperatively the semiactive system presents a schematic display of the drainage probe projected into a 3D model of the situs on the monitor screen corresponding to the instrument's position. As the surgeon directs the probe into the abscess the corresponding section is displayed. Thereby drainage is easily achieved under visual control.

[A new procedure for removal of foreign bodies in the area of the head]. / Ein neues Verfahren zur Entfernung von Fremdköpern im Kopfbereich.

Identification and extraction of penetrating cranial foreign bodies can cause problems in some cases. Small fragments localized deep in the orbit or cerebrum can be especially hard to detect. Severe bleeding and traumatized anatomy can make orientation difficult. We used a new localizing device, computer-assisted surgery (CAS), to good effect in six such cases. CAS is a localizing technique designed to assist the head surgeon during surgery, providing real-time position information. The method is based upon a three-dimensional volume model of the patient's skull generated by preceding computed tomography imaging procedures (CT or MRI). Intraoperative correlation of a 3D-model and the patient's skull allows for real-time position display of a surgical instrument on the monitor screen. Thereby the surgeon is able to localize even small foreign bodies without extensive exploration. In the case of multiple foreign bodies the surgeon calls up a simple documentation facility recording which of the visible fragments have already been extracted. We successfully used the system for extraction of orbital foreign bodies in four and intracerebral foreign bodies in two cases. In a 4-year-old child with gunshot injury the bullet was located in the precentral region and was easily extracted with the CAS system. In a 21-year-old man 39 glass fragments were extracted from the left orbit. In a 36-year-old man a bone fragment was dislocated to the apex of the orbit directly under the optic nerve. Location and extraction were achieved without damage to the orbital structures with the help of the CAS system.

Correlation between clinical, angiographic and transcranial Doppler sonographic findings in patients with moyamoya disease.

Nine patients with Moyamoya disease were followed by the authors between 1982 and 1991. The patients were investigated with transcranial Doppler sonography (TCD), angiography and clinically. Two patients were treated conservatively. Bilateral extra-intracranial (EC-IC) anastomosis was performed in 4 patients; in 2 patients bypass surgery was performed unilaterally. One patient with an aneurysm of the carotid artery presented a subarachnoidal haemorrhage. There was a good correlation between TCD and angiographical findings in all patients. In four patients indication for bypass surgery was established by TCD. All patients who underwent EC-IC bypass surgery improved clinically; the symptoms disappeared in three patients and improved markedly in two patients. Transcranial Doppler sonography is proven to be a reliable atraumatic tool in diagnosis, indication for treatment and postoperative follow-up in patients with moyamoya disease.

Dural arteriovenous malformations at the base of the anterior cranial fossa: report of nine cases.

Nine men with dural arteriovenous malformations (DAVM) at the base of the anterior cranial fossa are described. Four patients had intracerebral haemorrhage and four had seizures, associated with haemorrhage in two. In three cases the fistula was an incidental finding. In five cases the diagnosis could be made before angiography, on the basis of CT findings. Angiographically, venous drainage was always seen into ascending cortical veins. Five cases demonstrated drainage via the olfactory vein into the basal vein of Rosenthal; in four this way was the principal route of drainage. Five patients underwent surgery, the therapy of choice. One fistula closed spontaneously after angiography. Two patients refused treatment and one was not treated because of his poor general condition. Because arterial supply was usually bilateral, from small branches of the ophthalmic artery, embolisation seemed to be more dangerous. Compared to dural fistulae in other locations the DAVM of the anterior cranial fossa have a higher risk of complications and should be treated even if asymptomatic at the time of diagnosis.

Bilateral chronic subdural haematomas following traumatic cerebrospinal fluid leakage into the thoracic epidural space.

This report describes a patient who developed bilateral chronic subdural haematomas after a stab injury to the thoracic meninges causing prolonged cerebrospinal fluid leakage into the epidural space. Diagnostic findings and therapeutic management are presented and possible pathogenic mechanisms are discussed. This case suggests that patients who have symptoms or signs of increased intracranial pressure after a penetrating spinal injury should be studied for subdural haematoma.

[Orbital decompression by pterional approach in dysthyroid orbitopathies]. / La décompression de l'orbite par voie ptérionale dans les orbitopathies dysthyroïdiennes.

The etiology of the endocrine orbitopathy is still unknown and thereby their treatment remains symptomatic. The surgical decompression is achieved in resecting lateral wall, roof and partly bottom of the orbit. We treated 23 eyes in 14 patients and in only one patient the decompression obtained with this method was insufficient. This patient underwent additionally transantral transethmoidal decompression. One patient had a complete loss of vision after surgery probably due to direct lesion of the optic nerve. The decompression of the orbit is indicated in fast progressive endocrine orbitopathies with impairment of the visual function.

Experience with the infratentorial supracerebellar approach in lesions of the quadrigeminal region, posterior third ventricle, culmen cerebelli, and cerebellar peduncle.

We report about our experience with the infratentorial supracerebellar approach in 23 patients operated on for lesions located in the posterior part of the third ventricle, quadrigeminal plate, culmen cerebelli and cerebellar peduncle. Three patients had transient worsening of their deficits immediately after surgery. Three patients developed haemorrhages postoperatively requiring surgical evacuation. One of them died. None of the patients developed specific complications which could without any doubt be attributed to the approach. We concluded that in combination with intra-operative CSF drainage and the sitting position the infratentorial supracerebellar approach allows safe access to lesions situated in an area limited by the posterior part of the third ventricle, the fastigium level and both cerebellar peduncles.

Computer assisted localizer for planning of surgery and intra-operative orientation.

There is discrepancy between the exact representation of anatomical structures and tumours in the CT or MRI scan and the more or less accurate intra-operative localisation methods based mostly upon landmarks of the skull and extracerebral space and visible abnormalities of the cerebral surface. To overcome these problems of exact intra-operative localisation a Computer Assisted Localizer (CAL) is presented which allows precise intra-operative orientation without these aids. It consists of a mechanically articulated arm with six degrees of freedom with a high precision digital incremental and an image processor for 3 D data of the head. MRI and/or CT investigation is done pre-operatively with four reference markers fixed on the patient's head. They are visible on the CT or MRI slices and are used as reference points during surgery for adjustment of the device. The co-ordinates of the digitalizer arm tip are projected into the corresponding axial, sagittal and coronal CT slices so that the system simultaneously presents three orthogonal multiplanar CT reconstructions with a reticule indicating the position of the tip of the arm. As the surgeon directs the arm to the region of interest the corresponding CT slices are displayed on the monitor at a rate of 20 slices/sec determined by the motion of the arm. The accuracy of measurement of the device itself lies within 1 mm. The accuracy is somewhat reduced however by the thickness of CT or MRI slices (routinely 2 mm slices were taken) and by deviations of the reference markers on the skin surface which amount up to 3 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Limits of the transoral approach in craniospinal malformations.

Over a 15-year period, 15 patients with craniospinal malformations were operated on using the transoral route. Ten patients had basilar impression and five had atlantoaxial dislocation; nine patients had associated lesions. Patients treated with reposition and dorsal fusion recovered well without ventral decompression. We found that transoral odontoidectomy is suitable as a primary decompressing measure only in ventral compression or nondislocated atlantoaxial conditions.

Successful treatment of a haemangioblastoma in a 95 year-old patient. Case report.

Haemangioblastomas located in the posterior fossa have rarely been described in patients older than 60 years of age. The authors report a case of a 95 year-old man who presented with an obstructive hydrocephalus secondary to a posterior fossa tumour. Computed tomography and angiography suggested intracerebellar metastasis. Despite the advanced age of the patient and his poor general condition, surgery was performed with the patient in a supine position. A haemiangioblastoma was found and completely removed. The postoperative course was without complications. This case demonstrates that the combination of modern anaesthesia, supine operating position, and the use of microsurgical techniques allow successful operations on the posterior fossa even in very old patients.

[Gingival thickening with a submerged connective tissue graft]. / Proposition d'épaississement gingival par greffe de tissu conjonctif enfoui.

Gingival thickness is a clinical characteristic which should be given more consideration in evaluating muco-gingival problems. It is proposed that thick gingiva prevents gingival recession and is of particular significance when fixed prosthesis is being employed. The technique outlined includes a connective graft from the lamina propria of the palatal mucosa into the gingival connective tissue. A case report documents the technique.

[Biomechanical behavior of the pulpectomized tooth]. / Comportement biomécanique de la dent dépulpée.

No accurate information is in fact available regarding the biomechanical properties of devitalized teeth. The time frame seems to be a more significant factor than nature of the pulpectomy itself, as far as the risk of fracture is concerned. The use of a pivot or other form of root anchorage does not seem to play a determining role in the long-term reliability of restorations. Partial restorations can be substituted for full coronoperipheral reconstruction insofar as they protect the cusps. Each clinical situation must be matched with the appropriate reconstruction.