Biomedical subjects

H M Mehdorn

Publications and source records attributed to H M Mehdorn.

At least 37 records · Page 2Linked to original sources

PubMed2002

Clinical outcome after surgery of intracranial unruptured aneurysms: results of a series between 1991 and 2001.

The clinical results of surgery for unruptured aneurysms in the Neurosurgical Department of Kiel were analyzed to further discuss whether an operative treatment can be advised. Between 1991 and 2001, 54 unruptured aneurysms in 45 patients were operated in our department. No complications occurred in 38 patients; transient complications (slight aphasia, hemiparesis, psychiatric disorders) in 4 patients; postoperative seizures in one, epidural haematoma with the need of re-operation in one, and infection in another patient. At the time of discharge, GOS was 5 in 33 patients, 4 in 12 patients. But the slight disabilities were due to the aneurysm operation only in two patients, in the other 10 patients they were caused by pre-existing concomitant diseases. The Rankin-Scale after at least 6 months was 1 (no disability) in 31 patients (37 patients investigated); 2 (slight disability) in 5, and 3 (moderate disability) in one patient. In only one of these patients, the slight disability was caused by the aneurysm operation. During a telephone interview performed between 6 months and 7 years after the operation, all patients except two (31 patients investigated) gave a positive answer to the question, whether, in case of diagnosis of an aneurysm, they would undergo an operation again. Regarding our results, we still advocate treatment of unruptured aneurysms in patients who are in stable clinical conditions, especially in young patients and in patients with unique aneurysm configurations and aneurysm sizes approaching 10 mm.

Adolescent↗

PubMed2002

Magnetic resonance imaging-based morphometry and landmark correlation of basal ganglia nuclei.

The two principle targets for deep brain stimulation or lesioning in patients with Parkinson's disease, the subthalamic nucleus (STN) and the globus pallidus internus (GPi), reveal a high degree of individual variability which is relevant to the planning of stereotactic operations. Both nuclei can clearly be delineated in T2WI spin echo MRI which was acquired under stereotactic conditions in general anesthesia before surgery. Such images of 35 patients served for retrospective morphometric analysis of different basal ganglia nuclei (STN, GP, red nucleus, and substantia nigra) and several anatomical landmarks (anterior and posterior commissure, maximum width of third ventricle, brain length and width). The average AC-PC distance was 25.74 mm (range 21 to 29 mm) and is in agreement with previous studies. On average, the center of the STN was located 12.65 mm (+/-1.3) lateral from the midline as determined 3 mm ventral to the intercommissural plane. The average width of the third ventricle was 7.05 mm (+/-2.41). The width of the third ventricle correlated with the laterality of the STN (r(right)=.78; r(left)=.83) and GP (r(right)=.76; r(left)=.68). Although to a lesser extent, significant correlations were also observed between the laterality of the STN and brain width, improving prediction of STN laterality by multiple linear regression analysis (r(right)=.82; r(left)=.87). Similarly, the laterality of GP correlated with brain width. In addition, gender-specific differences were detected. The STN and GP was located farther lateral in males which may be due to overall brain anatomy as gender-specific differences were also observed for brain width and length and AC-PC distance. MRI-based in vivo-localization of different basal ganglia nuclei extend statistical information from common histological brain atlases which are based on a limited number of brains. The correlations observed between different basal ganglia nuclei, i.e. the STN and GPi, and anatomical landmarks may be useful for surgical planning.

Adult↗

PubMed2002

Therapeutical considerations in patients with intracranial venous angiomas.

The clinical presentation of intracranial venous angiomas are usually headache, seizures or dizziness. Very often these anomalies are found incidentally on magnetic resonance imaging (MRI). We reviewed 35 patients, which were examined in our department between 1994 and 2000. Only one patient became symptomatic with an intracranial haematoma, which was removed surgically. In three patients an associated cavernous angioma was found, which was removed successfully with preservation of the coexisting venous angioma. There is no indication in operating a venous angioma because the risk of postoperative deterioration caused by venous infarction is high. When removing cavernous angiomas the associated venous angioma has to be preserved.

Central Nervous System Neoplasms↗

PubMed2002

MRI- and skull x-ray-based approaches to evaluate the position of deep brain stimulation electrode contacts--a technical note.

Deep brain stimulation (DBS) has developed into an established therapy for the treatment of movement disorders, most commonly Parkinson's disease and tremor of different etiology. The subthalamic nucleus (STN) has evolved as the preferred target for DBS in patients with idiopathic Parkinson's disease. The principal target for DBS in tremor patients is the ventrolateral thalamus which has been explored for ablative procedures (thalamotomy) for some decades. Detailed information about the exact site of chronic stimulation, i.e. the location of the active electrode contacts, are important to map the actual subcortical structures modulating the therapeutic effects of DBS. We compared two different methods not requiring intra-operative teleradiography to determine the stereotactic coordinates of single electrode contacts, (i) correlation of pre- and post-operative MRI, and (ii) post-operative stereotactic skull x-ray. For seven patients implanted bilateral with quadripolar DBS electrodes the coordinates for each contact were determined by both approaches. This revealed for a total of 56 electrode contacts a median euclidean 3D-difference between both methods of 1.18 mm (range 0.42 to 1.93 mm). These data suggest that both approaches may be used to determine the position of single electrode contacts.

Electric Stimulation Therapy↗

PubMed2002

Technical complication in deep brain stimulation.

With a growing number of patients treated with deep brain stimulation (DBS) operations for both hardware-related complications and routine replacements of impulse generators will be performed more frequently. Failure of DBS systems have to be analyzed thoroughly as this thwarts the enormous efforts required for proper electrode implantation and operative revisions increase the morbidity associated with DBS. A female patient implanted with DBS electrodes for advanced Parkinson's disease presented with straining of the right extension lead and deteriorating gait because of electrode migration. This was due to a malpositioned set screw connector adapting the electrode lead to the extension wire which had been placed below the mastoid process. Following surgical revision with implantation of a new electrode into the STN, electrode dislocation recurred requiring another surgical revision. This was due to renewed connector migration from its parietal position into the cervical region. Straining of extension leads should be recognized as a warning sign for (imminent) electrode dislocation or lead fracture. This may just be the case with connectors located below the mastoid process or in the cervical region, a risk which appears to be increased further with reduced-length extensions. Renewed dislocation of revised extensions may be prevented by securing the position of the connector (e.g. with manipulates).

Electric Stimulation Therapy↗

PubMed2002

Continuous monitoring of cerebrovascular autoregulation: a validation study.

BACKGROUND: Continuous monitoring of dynamic cerebral autoregulation, using a moving correlation index of cerebral perfusion pressure and mean middle cerebral artery flow velocity, may be useful in patients with severe traumatic brain injury to guide treatment, and has been shown to be of prognostic value. OBJECTIVE: To compare an index of dynamic cerebral autoregulation (Mx) with an index of static cerebral autoregulation (sRoR). METHODS: Mx was validated in a prospective comparative study against sRoR, using 83 testing sessions in 17 patients with traumatic brain injury. sRoR and Mx were calculated simultaneously during pharmacologically induced blood pressure variations. RESULTS: Mx was significantly correlated with sRoR (R = -0.78, p < 0.05). Nine patients were found to have failure of cerebral autoregulation, with an sRoR value < 50%. If an Mx value of 0.3 was used as the cut off point for failure of cerebral autoregulation, this index had 100% sensitivity and 90% specificity for demonstrating failure of autoregulation compared with the sRoR. An increase in cerebral blood flow velocity correlated significantly with Mx (R = 0.73, p < 0.05) but not with cerebral perfusion pressure (R = 0.41). CONCLUSIONS: Dynamic and static cerebral autoregulation are significantly correlated in traumatic brain injury. Cerebral autoregulation can be monitored continuously, graded, and reliably assessed using a moving correlation analysis of cerebral perfusion pressure and cerebral blood flow velocity (Mx). The Mx index can be used to monitor cerebral blood flow regulation. It is useful in traumatic brain injury because it does not require any external stimulus.

Adult↗

PubMed2001

Role of potassium channels in the relaxation induced by the nitric oxide (NO) donor DEA/NO in the isolated rat basilar artery.

This study investigates whether potassium ion (K+) channels are involved in the nitric oxide (NO)-induced relaxation in segments of the isolated rat basilar artery, mounted onto a wire myograph. A high extracellular K+ concentration partly inhibited the relaxant effects of the NO donors DEA/NO and SIN-1 (3-morpholino-sydnonimine). Whereas single applications of the K+ channel inhibitors tetraethyl-ammonium (10(-3) M), glibenclamide (10(-6) M), 4-aminopyridine (10(-3) M), or BaCl(2) (5 x 10(-5) M) did not affect the responses to DEA/NO, a combination of these inhibitors reduced the effects of DEA/NO. These data suggest, that the relaxant effects of NO donors are partly mediated via activation of K+channels. Different K+ channel types seem to be involved that function in a redundant manner and compensate for each other.

4-Aminopyridine↗

PubMed2001

Effects of bilateral subthalamic nucleus stimulation on parkinsonian gait.

Gait analysis was carried out to assess the effects of L-dopa and bilateral subthalamic nucleus stimulation on gait velocity, cadence, stride length, and gait kinematics in nine patients with PD. Substantial effects of bilateral subthalamic nucleus stimulation on gait, with an increase in gait velocity and stride length comparable to that of a suprathreshold L-dopa dose, were found. Interestingly, stride length was more improved by L-dopa and cadence more by subthalamic nucleus stimulation. In two patients with freezing during the "on" period, subthalamic nucleus stimulation failed to reduce this symptom effectively.

Antiparkinson Agents↗

PubMed2001

Patient information in the light of quality assurance.

The relationship between patients and doctors has markedly changed over the last century. While until the turn of the 19th/20th century the patient was considered an object upon whom the doctor had the right to exert his art, the patient was then thought to have an integrity which the doctor could only legally injure with the consent of the patient. This was reflected in many court rulings, e.g. in Germany in 1894, requesting a doctor to inform the patient about therapy before performing surgery or even before giving medication, but also before performing invasive diagnostic procedures. The intensity of information required by law/court to be given to the patient varies also over time. Details of the implications to today's medical treatments are discussed.

Documentation↗

PubMed2001

Granular-cell tumour: a rare suprasellar mass.

Granular-cell tumour is a rare suprasellar space occupying lesion, which usually presents with visual deterioration, endocrine deficits or headache. We present two women with extraordinarily large tumours, measuring 3.8 and 4.0 cm in diameter. In both cases the tough, vascular tumour could be removed only subtotally.

Aged↗

PubMed2001

Nasopharyngeal extension of a craniopharyngioma in a 4 year old girl.

Nasopharyngeal extension of a craniopharyngioma is very rare and usually presents with headache, nasal obstruction and visual disturbances. We present a case of a 4 year old girl, who became symptomatic with visual deterioration. MRI showed a huge supra - and infrasellar cystic craniopharyngioma with extension into the sphenoid sinus. Primary treatment was a transnasal puncture of the cyst followed by a subfrontal approach with removal of the tumour preserving the chiasm and optic nerves. The visual acuity postoperatively improved while she needed hormone replacement due to panhypopituitarism. Follow-up 12 months after the operation showed no recurrence. This is the youngest patient of about 27 patients reported so far in the literature.

Brain Neoplasms↗

PubMed2001

Malignant peripheral nerve sheath tumours--report of 8 cases and review of the literature.

BACKGROUND: Though Malignant peripheral nerve sheath tumours (MPNST) are a rare entity accounting for 5-10% of soft-tissue sarcomas they are an important differential diagnosis to benign tumours of the peripheral nervous system regarding treatment and prognosis. METHOD: We present our experience with eight patients who underwent surgery for MPNST at the Department of Neurosurgery between 10/1990 and 9/1999. The median age was 37 years [range: 13-64], the male/female ratio was 1:1. Two patients suffered from Neurofibromatosis type 1. Paraffin embedded tumour specimens were immunohistochemically stained for S-100, p53 and Ki67/MIB-1. FINDINGS: The most frequent initial symptoms were local swelling and pain followed by irritation of cranial nerves and spinal ataxia. Four tumours were localised at the head & neck region, three were found in the extremities and one tumour was located on the trunk. All patients underwent surgery with curative intent, but total resection, defined by negative surgical margins, was achieved in only 3 cases. All of these developed local recurrence with a mean disease free survival time of 10.6 months. In five cases, adjuvant radiation was given. During follow up, three patients developed distant metastases located in the lung, liver and subcutaneous tissue. Five out of eight patients died during follow-up with a mean survival time of 11.6 months after diagnosis. Results of immunohistochemical staining were as followed: S-100 (7/8), p53 (7/8). The Ki67/MIB-1 proliferation index was detectable in all tumour samples, it differed from 10-30%. INTERPRETATION: MPNST is a rare and fatal diagnosis in neurosurgery with high risk of local recurrence and occurence of distant metastases. Though mulitimodal therapy including surgical resection and adjuvant radiotherapy including brachytherapy is available, the prognosis remains dismal. Modern clinical studies and the development of effective chemotherapy is needed in order to gain control of the disease.

Adolescent↗

PubMed2001

Olfactory event-related potentials in patients with brain tumors.

OBJECTIVE: The aim of the study was to determine how odor processing is altered in patients with unilateral supratentorial brain tumors. METHODS: Olfactory event-related potentials (OERPs) were evaluated in 10 patients with unilateral brain tumors of the frontal or temporal lobe in response to linalool and allylcaproate. Both odors were presented monorhinally by a constant-flow olfactometer. In addition, 20 healthy subjects were examined. While sniffing, the subjects were asked to discriminate the two odors. EEG was recorded from 7 electrode positions (Fz, Cz, Pz, F3/4, P3/4). Amplitudes and latencies of 3 peaks (N1, P2, P3) were measured. To control for effects of modality-non-specific alterations on the olfactory components acoustic event-related potentials (AERPs) were registered by use of an oddball paradigm. RESULTS: Patients with right-sided lesions showed distinct deficits in the discrimination task after stimulation of the right and left nostril. In contrast, patients with left-sided lesions only had an attenuation of correct reactions after left-sided stimulation. In the OERPs, patients with right-sided lesions showed P2- and P3-components with decreased amplitudes at parietal electrode positions. These alterations appeared after ipsi- and contralateral stimulation. Patients with left-sided lesions showed a significant effect of the side of stimulation. Their OERP-amplitudes were decreased after left-sided stimulation but not after right-sided stimulation. After right-sided olfactory stimulation a correlation between the olfactory and the acoustic ERP was seen in patients with right-sided lesions. CONCLUSIONS: Olfactory performance of the participating patients was markedly reduced. Patients with right-sided lesions showed bilateral impairment, which would support the importance of the right hemisphere in olfaction. The alteration of the topographic distribution of P2- and P3-amplitudes in patients with right-sided lesions might reflect an impairment of early and late olfactory processing steps.

Acyclic Monoterpenes↗

PubMed2001

(E)-5-(2-bromovinyl)-2'-deoxyuridine potentiates ganciclovir-mediated cytotoxicity on herpes simplex virus-thymidine kinase--expressing cells.

Tumor cells expressing the thymidine kinase gene of the herpes simplex virus (HSV-tk) are rendered highly susceptible to the cytotoxic effects of different antiherpes drugs. In an attempt to enhance cytotoxicity of this therapeutic approach in glioma and other tumor cell lines transduced with the HSV-tk gene, we evaluated tumor cell killing following co-administration of two different prodrugs metabolized by HSV-tk, (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU), and ganciclovir (GCV). In 8 of 12 cell lines investigated, addition of BVDU in concentrations showing no cytotoxic effect or only limited cytotoxicity could enhance GCV-mediated cell killing by as much as one order of magnitude. In co-cultures consisting of HSV-tk(+) (9L STK) and HSV-tk(-) (9L wild-type) cells, we also observed potentiation of GCV-mediated cytotoxicity in the presence of BVDU, suggesting strongly enhanced bystander cell killing. BVDU is thought to exert its cytotoxic effect through inhibition of thymidylate synthase activity or by incorporation into replicating DNA. Both effects could be observed in all HSV-tk--expressing cells investigated, including cell lines which did not exhibit cytotoxicity after incubation with BVDU. These findings argue against current concepts of BVDU-mediated cytotoxicity in HSV-tk--expressing cells. Taken together, our data suggest that gene therapy utilizing prodrug activating enzymes may be rendered more effective by simultaneous treatment with two different prodrugs metabolized by the same enzyme.

Animals↗

PubMed2001

Brain oedema in secretory meningiomas.

Brain oedema is usually associated with intracranial meningiomas in about 50-66%. As underlying causes, different factors like localisation, vascular supply, angiogenic growth factors and histological subtypes are discussed, and its existence is probably multifactorial. We present 11 patients with the rare subtype of secretory meningiomas. Brain oedema was observed in 82%. These tumours are localised mainly at the frontal convexity and at the sphenoid ridge. All 11 patients were female so that hormonal factors also may play a role in the production of peritumoural oedema. The postoperative outcome was good and no recurrences were seen during follow-up.

Adult↗

PubMed2001

Cerebral autoregulation testing after aneurysmal subarachnoid hemorrhage: the phase relationship between arterial blood pressure and cerebral blood flow velocity.

OBJECTIVE: Impairment of cerebral autoregulation (CA) appears to be an important cause for secondary ischemia after subarachnoid hemorrhage (SAH). It has been shown that graded CA impairment is predictive of outcome. Little is known about whether such impairment is present, what causes CA impairment, whether it precedes vasospasm, and whether it is predictive of outcome in patients with severe aneurysmal SAH. DESIGN: Prospective, controlled study. SETTING: Neurosurgical intensive care unit. PATIENTS: Twelve patients after aneurysmal subarachnoid hemorrhage, 40 controls. INTERVENTIONS: Recording of cerebral blood flow velocities and continuous measurement of arterial blood pressure at a controlled ventilatory frequency of six per minute to standardize the influence of intrathoracic pressure changes on blood pressure. MEASUREMENTS AND MAIN RESULTS: We calculated the phase shift angles (deltaphidegrees) between slow (0.1 Hz) arterial blood pressure and cerebral blood flow velocity waves measured by transcranial Doppler ultrasound in the middle cerebral artery during a) posthemorrhage days (PHD) 1-6 (early or prevasospasm phase), and b) during PHD 7-13 (late or vasospasm phase) using a 6/min ventilation protocol, and in 40 controls spontaneously ventilating at the same rate. deltaphi <30 degrees indicated lost CA. Mean flow velocities >100 cm/sec were considered vasospasm. We combined early and late measurements to assess the CA relationship with low cerebral perfusion pressure (CPP) and/or vasospasm. We assessed the Glasgow Outcome Scale (GOS) score at discharge (1 = worst, 5 = best). The admission Hunt and Hess score was 3.6 +/- 0.7. GOS scores were n = 3 (GOS 1), n = 2 (GOS 2), n = 5 (GOS 3), n = 1 (GOS 4), and n = 1 (GOS 5). In the early phase, deltaphi was 40.4 +/- 19.8 degrees (left), and 40.4 +/- 19.2 degrees (right). CPP was 69.4 +/- 10.9, intracranial pressure (ICP) was 6.7 +/- 2.8 mm Hg. In the late phase, deltaphi worsened in six patients and none improved: 32.1 +/- 21 degrees (left), and 26.9 +/- 17.2 degrees (right); CPP was 68.1 +/- 12.1, ICP was 7.5 +/- 3.7 mm Hg. CA was significantly impaired in both phases when compared with normal subjects (deltaphi: 65.7 +/- 24.5 degrees; p < .01 for early, p < .001 for late phase). In the early phase, seven of eight patients in whom autoregulation was intact had a GOS >2 at discharge and disturbed CA on at least one side was predictive of either vegetative condition at discharge or death (p < .01). In the late phase, deltaphi was no longer predictive of outcome. Spasm was present in 8 of 17 vessels (47%) in which CA was lost; no spasm was found in 25 of 28 vessels (89%) in which CA was intact (p < .01). A low CPP was present in 6 of 17 vessels (35%) in which CA was lost; a normal CPP was found in 21 of 27 vessels (78%) in which CA was intact (p > .05, NS). However, 14 of 17 vessels (82%) with lost CA showed spasm and/or low CPP while only 8 of 27 cases (30%) with intact CA had either spasm or low CPP (p < .001). CONCLUSIONS: CA can be assessed in a graded fashion in SAH patients. CA impairment precedes vasospasm; ongoing vasospasm worsens CA. CA assessment early after subarachnoid hemorrhage, within PHD 1-6, is predictive of outcome whereas late assessment is not. CA impairment is associated with cerebral vasospasm and low CPP.

Adult↗

PubMed2001

Secretory meningiomas: clinical and immunohistochemical observations.

OBJECTIVE: Secretory meningiomas are a rare histological subtype of these benign intracranial tumors. Few reports have been published regarding their tendency to develop peritumoral edema. METHODS: Between July 1994 and February 1999, 11 patients with secretory meningiomas underwent operations in the Department of Neurosurgery, University of Kiel, Kiel, Germany. The clinical notes and radiological data (computed tomographic and magnetic resonance imaging scans) were reviewed. Immunohistochemistry was used to examine the expression of carcinoembryonic antigen and epithelial membrane antigen as well as progesterone and estrogen receptors. RESULTS: Secretory meningiomas were found in 11 (5%) of 214 patients with intracranial meningiomas who were operated on in that period. All 11 patients were women. These patients' mean age was 65 years (range, 51-87 yr). The localization of these tumors was at the convexity in seven patients, at the sphenoid ridge in two patients, and in the olfactory groove and petroclival region in one patient each. Two meningiomas had no edema surrounding them, two meningiomas had a small amount of edema, two had moderate edema, and five had severe edema. No recurrences were observed during the mean follow-up period of 26 months (range, 8-65 mo). Immunohistochemically, all tumors contained pseudopsammoma bodies and reacted with epithelial membrane antigen and carcinoembryonic antigen. The MIB-1 antibody staining index showed a mean of 2% (range, 0-7%). CONCLUSION: Secretory meningiomas are rare tumors, and they are mainly localized at the frontal convexity and the sphenoid ridge. They are surrounded by more edema than usual. The preponderance of female patients with this presentation is striking. The expression of carcinoembryonic antigen and epithelial membrane antigen is a characteristic feature of secretory meningiomas. These meningiomas are also positive for progesterone receptors, which has been shown to be a good prognostic factor.

Aged↗

PubMed2001

Stroke pattern interpretation: the variability of hypertensive versus amyloid angiopathy hemorrhage.

INTRODUCTION: It is commonly felt that cerebral amyloid angiopathy (CAA) related intracerebral hemorrhage (ICH) can be distinguished from hypertension (HTN)-related ICH by certain typical features on computerized tomography (CT) and magnetic resonance imaging (MRI). The purpose of this study was to investigate the performance of clinicians who were asked to differentiate between CAA and HTN based on hemorrhage pattern interpretation and to assess the feasibility of such classification. METHODS: The admission scans from 83 patients who were admitted to our service with an acute ICH were presented to 5 clinicians in a randomized and blinded fashion (1 junior, and 1 senior neurosurgical resident, 1 attending neurosurgeon, and 2 neurosurgeon-neuroradiologists). There were no patients who received oral anticoagulants other than low-dose aspirin, or who suffered from vascular malformations or tumors. Scans from 41 patients with a histologically proven diagnosis of CAA and from 42 patients with a clear history of HTN were investigated. Hematoma evacuation was done in all CAA patients and in 59% of HTN patients (n = 25). RESULTS: The overall average classification accuracy was 66.8% (range: 62.7-69.9). For correct HTN classification it was 69.5% (range: 64.3-81), and 63.9% for CAA, respectively (range: 48.9-75.6). There were negligible differences in classification accuracy among all observers. Patients with a CAA-related ICH were significantly older than patients with a HTN-related ICH (74 vs. 66.5 years, p < 0.05). There was a significantly higher number of hematomas >30 ml in CAA (85.3%) when compared with HTN (59.5%). No basal ganglionic hemorrhage was seen in CAA, but in 40.5% in HTN. Intraventricular hemorrhage was seen in 24.4% in CAA, and in 26.2% in HTN. Two patients (4.9%) with CAA, and 7 patients with HTN (16.7%) presented with cerebellar hematomas. CONCLUSIONS: Three of 10 scans were not correctly diagnosed regardless of the examiner's level of training. This calls into question the reliability of classifying the underlying pathological condition based on hemorrhage pattern interpretation on CT or MRI. The definite diagnosis of CAA- versus HTN-related hemorrhage requires a histopathological confirmation and should not be based solely on hemorrhage pattern interpretation.

Adult↗