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.

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.

Haemodynamic changes in arteriovenous malformations induced by superselective embolization: transcranial Doppler evaluation.

To reduce the intraoperative and postoperative complications in patients who suffer intracerebral arteriovenous malformations (AVM's), the slow reduction of the shunt flow to a brain perfusion flow has been tried by the use of several methods: microsurgical techniques, selective and superselective embolization, intraoperative embolization, staged operation. The risk of re-bleeding and intraoperative oedema increases in AVM's with two or more feeders. Our policy was to exclude such AVM's by primary superselective embolization. If there was only a small residual angioma, we tried to remove this by microsurgical techniques. The haemodynamics in AVM's could be examined by measuring the blood flow velocities in the feeding arteries and in the other parts of the circle of Willis by transcranial Doppler sonography (TCD). Signs of haemodynamic effective embolization could be measured by the reduction of flow velocities. After exclusion of an AVM the velocities in the brain and feeding arteries decreased to below normal values in the first days after the operation. In the feeding arteries this was due to the fact that the arteries were enlarged so that the velocity must be decreased when there was normal volume flow. The combination of superselective angiography and microsurgical resection of the residual angioma seemed to be the best way to treat AVM's which are fed by more than two arteries and which are 3 or more cm in diameter. TCD investigations were used to measure the haemodynamic changes before and after angioma superselective embolization and microsurgical operation.

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.

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.

[Muscular work and its hyperemic phase in the patient with arteritis]. / Le travail musculaire et sa phase hyperhémique chez l'artéritique

Already users of a method of functional assessment of the muscular circulation in the patients with peripheral artery disease by Xenon 133, the authors propose a radical modification of the performance of the exercise test. A quantified exercise test leads to a new and more objective interpretation of the radio-active tracer elimination curve. This new method permits the measurement of the total quantity of blood which passed during the hyperhaemic stage and its time distribution. The aim of this test is to form an opinion on the tenacity and the efficiency of the supplementary mechanisms when there is an occlusion of the arterial axis.

[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.

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 microvascular Doppler--an intraoperative tool for the treatment of large and giant aneurysms.

One of the problems especially associated with large and giant aneurysms is the control of the patency of the parent artery and the exclusion of the aneurysm. While the exclusion can be tested by puncture (which may sometimes be problematic), the patency can only be controlled by intraoperative angiography or recently, by microvascular intraoperative Doppler. The device we use has a high resolution and is equipped with probes as small as 0.3 mm with which all visible vessels with diameters of more than 0.1 mm can be investigated. Local stenoses above a diameter reduction of 40% can be easily detected by localized accelerations and changes in the pulse curves. Our recent experience with 11 giant and 13 large aneurysms has revealed marked discrepancies between an apparently well placed clip and an obviously open vessel on the one hand, and the haemodynamic reality revealed by the Doppler on the other. We were able to decide whether the flow was undisturbed, or whether there was an haemodynamically non-effective lumen reduction due to a tight clip, or if there was severe stenosis or a total occlusion. In five cases with severely disturbed flow after clipping, we had to change our strategy: we resected the aneurysms and sutured the neck, performed an end-to-end anastomosis, coated the aneurysm, or repositioned the clips. In cases in which we did not have full view of the neck, the Doppler guided us to a proper clip position. We conclude that especially for large and giant aneurysms, the microvascular interoperative Doppler is a valuable tool.

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.

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.

[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.

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.

[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.

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.

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.

[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.

Microsurgical unilateral approaches for spinal tumour surgery: eight years' experience in 256 primary operated patients.

A series of 256 consecutive patients suffering from spinal tumours was studied with respect to the value of bilateral or unilateral surgical approaches. The case material included 152 extradural, 87 intradural, extramedullary and 17 intramedullary tumours. The cervical spinal cord was involved in 43, the thoracic in 152 and the lumbosacral region in 61 cases. Hemilaminectomy was chosen mainly for juxtamedullary tumours, while laminectomy was used for intramedullary tumours. No remarkable difference regarding the choice of approaches was found in extradural tumours. More than 60% of cervical or lumbosacral tumours were managed using unilateral procedures. A higher rate of surgical radicality but fewer complications, shorter stay in hospital and better early results were achieved using hemilaminectomy especially in patients with juxtamedullary tumours. From the observations it may be concluded that the results do not depend on the type of surgical approach but are closely related to the histology and location of tumours. Under the prerequisite of exact pre-operative definition of tumour location, unilateral approaches are advantageous for all kinds of spinal tumours especially for juxtamedullary benign tumours.