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Biomedical subjects

M Mehdorn

Publications and source records attributed to M Mehdorn.

10 recordsLinked to original sources
PubMed2001

Children's spatial behavior is differentially affected after traumatic brain injury.

Spatial behavior in 20 children with severe traumatic brain injury (TBI) and 20 healthy controls was investigated using the Kiel Locomotor Maze. Children had to remember defined locations in an experimental chamber with completely controlled intra- and extra-maze cues until learning criterion was reached. In a second experiment, spatial orientation strategies were assessed. Children with TBI were shown to be impaired in spatial learning and spatial memory. Spatial orientation was found to be deficient even in cases where spatial learning and memory proved to be unimpaired, especially in tasks that demanded the use of relational place strategies. Children who suffered a TBI at an early age proved to be more severely impaired in spatial learning and orientation than older children.

Brain Injuries↗
PubMed1999

Analysis of gait in cervical myelopathy.

Gait disorders are a frequent symptom of cervical spondylotic myelopathy (CSM). Twelve patients with CSM underwent gait analysis before and after decompressive surgery. They were assessed on a walkway and a treadmill and compared with a healthy matched control group. The following features were observed in the CSM group before surgery: significantly reduced gait velocity and step length (P<0. 05), prolonged double support, increased step width, and reduced ankle joint extension during treadmill walking. Knee and hip kinematics did not differ from controls. Two months after surgery, spatio-temporal parameters had moved towards normal values, velocity, step length and cadence had increased significantly, and there was reduction of step width during treadmill walking, indicating improved equilibrium. Gait analysis is an objective tool to document functional recovery after decompressive surgery in CSM.

Cervical Vertebrae↗
PubMed1998

Development of spatial memory and spatial orientation in preschoolers and primary school children.

The present study addresses the question of what kind of information children use when orientating in new environments, if given proximal and distal landmarks, and how spatial memory develops in the investigated age groups. Ten 5-year-old, ten 7-year-old and ten 10-year-old children were presented with the 'Kiel Locomotor Maze', containing features of the Radial Arm Maze and the Morris Water Maze, in order to assess spatial memory and orientation. Children had to learn to approach baited locations only. Task difficulty was equated with respect to the children's age. Training was given until the children reached criterion. During testing, the maze configuration and response requirements were systematically altered, including response rotation, cue rotation, cue deletion and response rotation with cue deletion in order to assess the spatial strategies used by the children. During training and testing, working-memory errors (WM), reference-memory errors (RM) and working-reference memory errors (WR) were recorded. As expected, no difference between age groups appeared during training, thus confirming comparable task difficulty across age groups. During testing, age groups differed significantly with regard to the orientation strategy used. The 5-year-olds were bound to a cue strategy, orientating towards local, proximal cues. The 10-year-olds mastered all tasks, thus displaying a place strategy, being able to use distal cues for orientation, and were even able to do so after being rotated 180 degrees. The 7-year-olds proved to be at an age of transition: five of them were bound to a cue strategy, five children were able to adopt a place strategy. The differences in the orientation strategies used by children of different age groups was reflected by the sum of errors they made, also by RM. WM were found to be rare, especially in older children. We conclude that preschoolers use a cue strategy, that the development of place strategies occurs during primary school age and seems to be complete by the age of 10 years.

Age Factors↗
PubMed1997

Remote memory in patients with acute brain injuries.

Remote memory was investigated in an unselected sample of 26 patients with either unilateral tumours in the temporal lobes or traumatic brain injuries. Six patients underwent excisions within the left temporal lobe, and nine patients were operated on within the right temporal lobe. In both groups, patients with excisions including and sparing the hippocampal formation were studied. Their performance was compared to that of 11 patients with moderate to severe head trauma and to a normative sample of 214 healthy controls. Remote memory was assessed using a famous events test with items of extremely low salience that had been proven to be of low difficulty for those old enough at the time of the event's actuality. The results show severely disturbed retrograde memory functions in the left temporal tumour group. These patients achieved similar scores to patients with severe traumatic brain injury. Right hemispheric patients showed a pattern of results comparable to that of healthy controls. The strongest effects were in the free recall part of the test. In most of the patients, no graded memory loss was observable. No consistent association to recent memory function could be identified. Since most of the remote memory test items used denoted famous names which were cued by rich semantic information, the type of deficit seen may be best understood in terms of a specific dysfunction of the semantic stores containing information about famous proper names.

Adult↗
PubMed1988

Cerebrovascular reserve capacity (CRC) in carotid artery disease: a routine test in selection for surgical treatment?

An increase of arterial carbon dioxide (CO2) partial pressure induces an increase of cerebral blood flow by dilatation of the resistance vessels. By the Transcranial Doppler sonographic technique (TCD) blood flow velocity as a correlate of flow volume can be measured within the great basal intracranial arteries. We investigated 8 patients with an internal carotid artery occlusion or high-grade stenosis and 5 cerebrovascular diseased patients without extracranial stenosis. 12 healthy volunteers and patients without vascular disease served as the control group. Blood flow velocities in the middle cerebral arteries were evaluated before and after 5 minutes of breathing a 5% CO2 gas mixture. In a prestudy the end tidal pCO2 was monitored during this procedure. As a result of the close parallelity of pCO2 increase in the prestudy group we planned to standardize the CO2 reactivity tests without consideration of the individual pCO2 values. The CO2 inhalation provoked a flow velocity increase of at least 20% in the control subjects (47.1 +/- 17.3%). The vascular diseased without extracranial stenosis responded with 34.8 +/- 17.4% (minimum: 23.5%, n. s.). The CO2 reactivity in cases of occlusion or greater than 50% stenosis was significantly decreased (p less than 0.001) both when considering only the affected sides (12.4 +/- 7.5%, maximum: 20%) and when including the non affected sides (22.6 +/- 15.0%). It is concluded that the CO2 reactivity test is a simple and valid method to evaluate the cerebrovascular reserve capacity in any case of uncertainty about the benefits of surgical treatment of a carotid stenosis. In future this technique might become one fundamental argument beside others in selecting adequate treatment.

Arterial Occlusive Diseases↗
PubMed1988

Diagnostic problems and operative treatment of pituitary microadenomas.

Over an average observation period of 53 months 26 patients with endocrinological active microadenoma of the hypophysis (12 M. Cushing, 14 acromegaly) were retrospectively examined. Only in 11 cases did the CT-examination demonstrate intrasellar tumour expansion. Both the problems of and the criteria for CT-diagnosis of microadenoma were demonstrated. In 22 cases (84%) the microsurgical transsphenoidal exstirpation of the adenoma led to an adequate reduction in both ACTH and HGH. No postoperative deterioration of the other hypophysial functions was seen. It could be further demonstrated that where the surgical therapy failed local radiation therapy with high voltage radiation of the hypophysis region led to a reduction of the abnormal hormone secretion. The comparism of our results with those reported in the literature led us to suggest a combined therapy concept in which the indication for operative, conservative and radiation therapy is delineated.

Acromegaly↗
PubMed1980

Chronic reversible cerebral ischemia: evaluation of a new baboon model.

The authors describe their experience with a baboon model of reversible cerebral ischemia. Middle cerebral artery occlusion was achieved by external compression with an implantable, inflatable balloon cuff in awake, unanesthetized baboons. Selective cerebral angiography confirmed consistent, reliable occlusion. Computed tomography demonstrated early density changes after ischemia, which were reversible with reperfusion. Neurological evaluation demonstrated a "recruitment response" of increasingly persistent deficit with repeated occlusion. Permanent deficits were noted after extensive angiography during periods of occlusion. This was accompanied by the dropout of small vessels in the middle cerebral artery distribution. The results of pathological examinations were consistent with the clinical examinations. No gross or microscopic changes were noted after repeated occlusions that caused deficits like those of transient ischemic attacks. Consistent infarctions were noted in animals with permanent deficits after permanent occlusion or after repeated occlusion and extensive angiography.

Animals↗