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Biomedical subjects

A Harders

Publications and source records attributed to A Harders.

At least 37 records · Page 2Linked to original sources
PubMed1999

Reconstruction of an extreme frontal and frontobasal defect by microvascular tissue transfer and a prefabricated titanium implant.

A 30-year-old man was referred to us with an extreme frontal and frontobasal defect from a motorbike accident 12 years before. Multiple attempts at frontal and frontobasal revision and reconstruction had been performed over the years, with several episodes of meningitis. Reconstruction was planned in two steps. First, a revision of the anterior skull base with mobilization of meningeal adhesions and duraplasty, removal of infected masses of polymethylmethacrylate out of the upper ethmoid sinuses, and coverage with a deepithelialized latissimus dorsi free flap were performed. In the second step 3 months later, aesthetic forehead reconstruction was achieved with a pre-fabricated individual titanium implant. The predictable result of this two-step reconstruction was very pleasing. Safe separation of the cranial cavity from the upper airways was essential, requiring free tissue transfer in this case, and is a prerequisite for any alloplastic forehead reconstruction. Timing of the two-step procedure, including the CT data acquisition; handling of soft tissues, bone, and foreign material; and construction details of the implant demonstrate the necessary complex management of this, the most difficult case of the 88 applications of the new computer aided design and manufacturing technique thus far. Even the most elaborate computer aided preparation cannot be successful without consideration of established surgical principles.

Adult↗
PubMed1999

Factors influencing shunt dependency after aneurysmal subarachnoid haemorrhage.

In this retrospective analysis of 138 patients treated for ruptured aneurysms the development of shunt dependent hydrocephalus was evaluated regarding possible predictive factors. In 15 patients (11%) ventriculo-atrial shunt was implanted due to hydrocephalus. One predictive factor was the localisation of aneurysms as patients with hydrocephalus had PcoA aneurysms in 40% compared to 20% in the group of patients without hydrocephalus and only 7% compared to 28% MCA aneurysms. An other predictive factor was the severity of the subarachnoid haemorrhage (SAH) as 7 patients out of the 15 were graded Fisher IV on admission. Furthermore, an important predictive factor was the presence of acute hydrocephalus as 13 out of the 15 patients (87%) with shunt dependent hydrocephalus had acute hydrocephalus requiring external ventricular drainage. An other possible factor was the intraoperative opening of the lamina terminalis as in 73% of the patients with shunt dependent hydrocephalus compared to 82% in the group of patients without hydrocephalus this procedure was performed during surgery. The results suggest that shunt dependency is more likely after severe SAH especially in the presence of an acute hydrocephalus and in patients with aneurysms located in the basal cisterns. Therefore treatment of the acute hydrocephalus and possible the opening of the lamina terminalis could have a positive effect on the development of shunt dependent hydrocephalus after SAH.

Adolescent↗
PubMed1998

Preoperative planning and intraoperative navigation: status quo and perspectives.

An essential step in modern microneurosurgery involves preoperative planning of procedures. For difficult lesions neuronavigation is being used in conjunction with complex and detailed radiological investigations. This article shows how these examinations are used for computerized planning of surgical steps. Although planning and navigation are still two separate entities, the combination of the two may help in neurosurgery.

Aged↗
PubMed1998

Operative approach due to results of functional magnetic resonance imaging in central brain tumors.

Since 1995 we have been investigating the localization of the cortical motor strip by functional magnetic resonance imaging (fMRI) in central brain tumor cases. Forty patients have been operated on using these data for preoperative planning. Intraoperative sensory evoked potentials (SEP) and cortical motor evoked potential (performed in 18 patients) showed a good correlation with fMRI data with the exception of two cases. Only 12.5% of cases were permanently worsened as a result of increasing postoperative pareses.

Brain Neoplasms↗
PubMed1998

[Delayed lumbar epidural hematoma. Discussion of the risk factors: hypertension, anticoagulation and spinal anesthesia].

This case report deals with the very rare complication of an intraspinal haematoma: a 70 year old male underwent anticoagulation because of supraventricular dysrhythmias followed by two transient ischaemic attacks. He accidentally received an intramuscular injection for tetanus prophylaxis and developed a deep intramuscular haematoma, which was operated upon, after normalisation of coagulation parameters, under spinal anaesthesia. No primary complication was noted. Heparin therapy was started perioperatively, on the day of the operation. Sixteen days postoperatively, the patient resumed oral anticoagulation; 3 months later he developed a progressive cauda-equina-syndrome due to an epidural haematoma at the level of L2 to L4. This could be diagnosed by magnetic resonance imaging, but not by computed tomography. Acute surgical decompression was performed. The haematoma showed various ages as suspected by the intraoperative morphology and proven by histological examination. The neurological findings improved, and 6 months after rehabilitation only slight neurological deficits remained. Hypertension, anticoagulants, and spinal anaesthesia are discussed as risk factors for this complication.

Aged↗
PubMed1997

CO2 reactivity in patients after subarachnoid haemorrhage.

CO2 reactivity was tested in patients with transcranial Doppler sonography (TCD) and endtidal CO2 measurements after an average time interval of ten months after subarachnoid haemorrhage (SAH). After deliberately changing breathing there was a significant change in endtidal CO2 and in flow velocities in all three examination groups. Comparing 27 patients with SAH and 5 patients treated for incidental aneurysms and 20 patients without cerebrovascular disease there were no significant differences in CO2 reactivity. Furthermore, there were no right to left differences. In 12 patients with vasospasm, two of them treated by percutaneous transluminal angioplasty for delayed ischaemic deficits, CO2 reactivity was normal at the time of investigation. Furthermore, normal CO2 reactivity was found in patients after SAH and surgery for ruptured aneurysms regardless of the severity of the SAH.

Adolescent↗
PubMed1997

[CAD/CAM (computer-aided design/computer-aided manufacturing) titanium implants for cranial and craniofacial defect reconstruction].

The reconstruction of craniofacial bone defects with intraoperatively modeled prosthesis restricts the choice of material and its biocompatibility and the prediction of the esthetic result. A prolonged duration of the surgical procedure and an increased stress on the patient are consequences. In contrast, modern industrial CAD/CAM-systems allow the prefabrication of titanium prosthesis: An individual computer-based 3D model of the bony defect is generated after acquisition, transfer and evaluation of helical CT data. Basing on these data the individual prosthesis-shape is designed using freeform surfaces geometries and fabricated by a numerically controlled milling machine. The conical margins of this prosthesis-geometry are generated by the borders of the defect with a minimal gap of 0.25 mm, and the surface contours by considering the non-affected neighbouring contours with a constant thickness of 1.5 mm. Individual osteosynthesis-microplates for fixation are integrated in design and manufacturing if screw-holes cannot be integrated in the thin margins of the implants. The radiological and clinical results of 17 patients after reconstruction of craniofacial bone defects with CAD/CAM titanium implants were good. Complications were not observed.

Adolescent↗
PubMed1996

[3-D-TONE magnetic resonance angiography in the detection of intracranial aneurysms compared with digital subtraction angiography. A prospective study].

PURPOSE: To evaluate the efficiency and accuracy of the optimized 3-D-MT-TONE-magnetic resonance angiography (MRA) with that of intraarterial digital subtraction angiography (DSA) in the detection of intracranial aneurysms. MATERIAL AND METHODS: From March 1994 to March 1995 30 patients with 38 aneurysms were prospectively subjected to MRA as well as to DSA. Respiratory insufficient patients were excluded from MRA. RESULTS: The aneurysm size ranged from 3-50 mm with an average size of 9 mm. Correct diagnosis was done in 33 aneurysms (86.8%) in 26 of the patients. In 4 patients (13.3%) with 5 aneurysms, the blinded readers made an incorrect diagnosis due to degradation of image quality. One (2.6%) aneurysm was falsely described via MRA as well as via DSA. The sensitivity was 86.8%. In the control group of 30 patients three aneurysms were found, therefore the specificity was 90% and we could calculate a positive predictive value of 97.1%, a negative predictive value of 84.4% and a correct diagnosis of 90.1%. CONCLUSION: Our results show that MT-TONE-MRA is a useful non-invasive technique with improved vascular detail and vascular background for detection of intracranial aneurysm. Further technical improvements are necessary for better visualisation of pathological findings in the carotid siphon, where only 60% of the aneurysms could be clearly detected.

Adult↗
PubMed1996

MRI-guided endoscopy in the brain: a feasability study.

For neuronavigation in neuroendoscopy conventional navigation systems cannot exclude tissue movements caused by loss of cerebrospinal fluid (CSF). Open MRI can serve as a real-time navigation system if special conditions of endoscopic instruments and equipment are followed. We adapted an endoscopic system to the MRI and installed a miniaturized laser guidance system to project the central transaxial and coronal planes onto the phantom. A human cadaveric model was examined with a flexible microendoscope marked with a titanium wire inside the open magnet. The procedures were guided by gradient echo sequences refreshing the image every 4.5 seconds to control position of the endoscope. Endoscopic and corresponding MRI-findings are presented. Results and technical conditions are discussed.

Artifacts↗
PubMed1996

Traumatic subarachnoid hemorrhage and its treatment with nimodipine. German tSAH Study Group.

A prospective, randomized, double-blind, placebo-controlled study of nimodipine used to treat traumatic subarachnoid hemorrhage (tSAH) was conducted in 21 German neurosurgical centers between January 1994 and April 1995. One hundred twenty-three patients with tSAH appearing on initial computerized tomography (CT) scanning were entered into the study. Requirements for inclusion included age between 16 and 70 and admission into the study within 12 hours after head injury, regardless of the patient's level of consciousness. Eligible patients received either a sequential course of intravenous and oral nimodipine or placebo treatment for 3 weeks. Patients were closely monitored using clinical neurology, computerized tomography, laboratory, and transcranial Doppler ultrasound parameters. Patients treated with nimodipine had a significantly less unfavorable outcome (death, vegetative survival, or severe disability) at 6 months than placebo-treated patients (25% vs. 46%, p = 0.02). The relative reduction in unfavorable outcome in the nimodipine-treated group was even higher (55%, p = 0.002) when only patients who complied with the protocol were considered.

Adult↗
PubMed1996

Intratumorous heterogeneity of chromosome 10 and 17 in meningiomas using non-radioactive in situ hybridization.

Contrary to classical cytogenetics non-radioactive chromosomal in situ hybridization (CISH) may be performed within 24 hours while the morphological structure of paraffin-embedded tumor material is preserved. Slides of 34 formalin fixed and paraffin-embedded meningiomas were hybridized with a biotinylate alpha-satellite DNA-probe for chromosome 10 and 17. According to the distribution of hybridization signals per nucleus we found five meningiomas with signs of trisomy 17 whereby all of them exhibited intratumorous heterogeneity. Trisomy 10 was found in five tumors. Monosomy 17 was assumed in two cases and monosomy 10 in one meningioma. As a control six meningiomas were karyotyped by G-banding. Formalin fixed and paraffin-embedded tissue of the same tumors was hybridized against chromosome X and Y. In five of six cases the result of conventional karyotyping could be confirmed by in situ hybridization. CISH of paraffin-embedded tissue is new tool for the analysis of intratumorous cytogenetical heterogeneity with potential prognostic significance.

Adult↗
PubMed1995

Gagel's granuloma (localized Langerhans cell histiocytosis) in the pituitary stalk.

A 46-year-old man with diabetes insipidus, hypothyroidism and hypocortisolism was found to have a tumor of the pituitary stalk. After transsphenoidal resection of the tumor substitution of cortisol and thyroxin was necessary. Pathological examination of the lesion revealed an extremely rare granulomatous infiltration classified as Gagel's granuloma (Langerhans' cell histiocytosis). Pre- and postoperative magnetic resonance imaging (MRI) studies, differential diagnosis and treatment of such lesions are presented.

Diabetes Insipidus↗
PubMed1995

Prefabricated prostheses for the reconstruction of skull defects.

Cranioplasties using intraoperatively modeled prostheses may fail to create harmonic contours with long-term stability. In contrast, preoperative modeling would allow more sophisticated planning of the contour and better preparation of the implant material, if a sufficiently precise model of the defect-site was available. In this respect, computer aided design and manufacturing (CAD/CAM)-techniques based on helical computed tomography (CT) data are successfully used for the prefabrication of prostheses: An individual computer-based 3-dimensional model of the bony defect is generated after acquisition, transfer and evaluation of the CT data; from this freeform surfaces geometry an individual and "idealized" prosthesis-geometry is derived and fabricated by a numerically controlled milling machine using modern industrial CAD/CAM-systems and design software. The margins of this prosthesis-geometry are generated by the borders of the defect and the surface by considering the non-affected neighbouring contours. Cranioplasties in cases of large postsurgical skull defects are presented as the first clinical applications of this new method, which also allows the use of titanium and fabrication of integrated fixation-devices.

Computer Simulation↗
PubMed1995

Reconstruction of craniofacial bone defects with individual alloplastic implants based on CAD/CAM-manipulated CT-data.

Reconstruction of craniofacial bone defects by intraoperative modelling of autogenous or alloplastic materials may cause undesirable results concerning the implant shape or the long-term maintenance of this shape. Furthermore, the use of alloplastic materials to be modelled intraoperatively may result in an inflammatory tissue response. Therefore the question is raised whether CAD/CAM-techniques may be used for the pre-operative geometric modelling of the implant based on helical computed tomography data. A numerically based 3-dimensional model of the skull defect serves as the basis for a freeform-surfaces design of the implant shape, position and thickness, using modelling tools and programmes developed for industrial CAD/CAM. The precise and individual fit of the implant results from generating its margins by the borders of the defect, whereas the implant surface is generated by the geometry of the non-affected neighbouring bone contours. The implant data run a numerically controlled milling machine to fabricate the individual implant. The reconstruction of post-traumatic defects of the forehead, of post-surgical temporal defects after intracranial haemorrhage, and of a parieto-occipital defect due to ablative tumour surgery are presented as the first clinical experiences of this new method.

Adolescent↗
PubMed1995

[Dysphagia: a neurosurgical indication for an operation?].

Ventral osteophytes of the cervical spine can be the reason for dysphagia in rare cases. We present a 67-year old man with difficulties in swallowing for three years and a ventral osteophyte at the level of C 5/6. Native X-rays of the cervical spine, CT-scan and x-ray examination with barium meal and with a barium ball was performed. In our case the most useful procedure for operative indication was the dynamic examination with the barium ball which demonstrates clearly the obstructed oesophageal passage. During operation the ventral osteophyte was resected via ventral approach to the cervical spine. Postoperatively patient's symptoms completely disappeared. Differential diagnosis and therapy are discussed.

Aged↗