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Biomedical subjects

M Maschke

Publications and source records attributed to M Maschke.

At least 37 records · Page 2Linked to original sources
PubMed2003

Cerebellar responses evoked by nociceptive leg withdrawal reflex as revealed by event-related FMRI.

The aim of the present study was to examine nociceptive leg withdrawal reflex-related areas in the human cerebellum using event-related functional brain imaging (fMRI). Knowledge about cerebellar areas involved in unconditioned limb withdrawal reflex control has some relevance in understanding data of limb withdrawal reflex conditioning studies. Sixteen healthy adult subjects participated. Nociceptive leg withdrawal reflexes were evoked by electrical stimulation of the left tibial nerve behind the medial malleolus. An event-related fMRI paradigm was applied with a total of 30 stimuli being delivered pseudorandomly during 500 consecutive MR scans. Surface electromyographic (EMG) recordings were performed from the left anterior tibial muscle. Only trials with significant reflex EMG activity were used as active events in fMRI statistical analysis. The specified contrasts compared the active event condition with rest. Leg withdrawal reflex-related areas were located within the vermis, paravermis, and lateral posterior cerebellar hemispheres bilaterally. Vermal and paravermal areas in lobules III/IV in the anterior lobe and in lobule VIII in the posterior lobe agree with the cerebellar representation of climbing and mossy fiber hindlimb afferents and voluntary leg movements. They are likely related to efferent modulation of the leg withdrawal reflex and/or sensory processing of afferent inputs from the reflex and/or the noxious stimulus. Additional activation within vermal lobule VI and hemispheral lobules VI/Crus I may be related to other pain-related processes (e.g., facial grimacing, fear, and startlelike reactions).

Adult↗
PubMed2003

Comparison of eyeblink conditioning in patients with superior and posterior inferior cerebellar lesions.

The aim of the present study was to compare eyeblink conditioning in cerebellar patients with lesions including the territory of the superior cerebellar artery (SCA) and in patients with lesions restricted to the territory of the posterior inferior cerebellar artery (PICA). The cerebellar areas known to be most critical in eyeblink conditioning based on animal data (i.e. Larsell lobule H VI and interposed nucleus) are commonly supplied by the SCA. Eyeblink conditioning was expected to be impaired in SCA, but not in PICA patients. A total of 27 cerebellar patients and 25 age-matched controls were tested. Cerebellar lesions were primarily unilateral (n = 20). Most patients suffered from ischaemic infarctions of the SCA (n = 11) or the PICA (n = 13). The other patients presented with cerebellar tumours (n = 2) and cerebellar agenesis (n = 1). The extent of the cortical lesion (i.e. which lobuli were affected) and possible involvement of the cerebellar nuclei was determined by 3D-MRI. As expected, the ability to acquire classically conditioned eyeblink responses was significantly reduced in the group of all cerebellar patients compared with the controls. In the patients with unilateral cerebellar lesions, conditioning deficits were present ipsilaterally. In SCA patients with lesions including hemispheral lobules VI and Crus I, eyeblink conditioning was significantly reduced on the affected side compared with the unaffected side. No significant difference between the affected and unaffected sides was present in patients with lesions restricted to the common PICA territory (i.e. Crus II and below). Conditioning deficits were neither significantly different in SCA patients with pure cortical lesions compared with SCA patients with additional nuclear impairment nor in SCA patients with unilateral lesions compared with SCA patients with bilateral lesions. To summarize, unilateral cortical lesions of the superior cerebellum appear to be sufficient to reduce eyeblink conditioning in humans significantly.

Adult↗
PubMed2002

Classical conditioning of postural reflexes.

Unexpected external perturbations of body equilibrium elicit compensatory postural reflexes. The reflex patterns change only minimally, even after repetitive perturbations. This study addressed the question of whether classical conditioning can alter the reflex patterns. In the first session 27 healthy subjects were tested when standing on an unexpectedly tilting platform. Electromyographic (EMG) activity from different leg muscles and the vertical ground forces, from which the centre of vertical pressure (CVP) was computed, were recorded. In a subsequent session subjects were tested using the classical conditioning paradigm with the tilting platform as the unconditioned stimulus (US) and a prior auditory signal as the conditioning stimulus (CS). The decay of the unconditioned response (UR) observed in the first session was similar and small in all subjects. During conditioning, 22% of the subjects established conditioned responses (CR) in all muscles recorded (strategy 1). UR amplitudes of the anterior tibialis (TA) decayed more than in the first session. The resulting CVP excursions were similar to those observed in US-alone trials. The remaining subjects exhibited CR only in the gastrocnemius muscle but developed a substantial decay of UR, resulting in very small CVP excursions (strategy 2). Our data suggest that processing of US-preceding conditioning stimulus leads to different strategies in the control of postural adjustment with assumed underlying associative and non-associative plastic processes.

Adult↗
PubMed2002

MRI atlas of the human cerebellar nuclei.

The differential role of the cerebellar cortex and nuclei has rarely been addressed in human lesion and functional brain imaging studies. One important reason is the difficulty of defining the localization of the cerebellar nuclei and extent of possible lesions based on CT or MR scans. The present MRI investigation was specifically designed to study the anatomy of the deep cerebellar nuclei. In both basal ganglia and cerebellar nuclei of healthy human subjects the amount of iron is high compared to the rest of the brain. Clusters of iron are paramagnetic and, therefore, tend to cause local inhomogenities in a magnetic field. The iron-induced susceptibility artefacts were used to visualize the cerebellar nuclei as hypointensities on MR images. A three-dimensional atlas of the dentate (D), interposed (I), and fastigial (F) nuclei is presented in standard proportional stereotaxic space coordinates based on findings in a healthy 26-year-old female. A three-dimensional axial volume of the cerebellum was acquired using a T1-weighted fast low-angle shot (FLASH) sequence on a Siemens Sonata 1.5 Tesla MR. To increase the signal to noise ratio the sequence was acquired 5 times and averaged. Each volume was registered, resampled to 1.00 x 1.00 x 1.00-mm3 voxel size and spatially normalized into a standard proportional stereotaxic space (the MNI-space) using SPM99. Localization of cerebellar nuclei were confirmed by comparison with postmortem MRI and histological microsections of another brain.

Adult↗
PubMed2002

Progressive multifocal leukoencephalopathy limited to the brain stem.

Progressive multifocal leukoencephalopathy (PML) is a subacute demyelinating slow-virus encephalitis caused by the JC polyomavirus in 2-5% of patients with AIDS. MRI typically shows multiple lesions in the cerebral hemispheres. We present a rare case of rapidly evolving and lethal PML with a severe bulbar syndrome and spastic tetraparesis in a patient with AIDS. MRI showed high-signal lesions on T2-weighted images confined to the brain stem, extending from the medulla oblongata to the midbrain. JC virus polymerase chain reaction in cerebrospinal fluid was positive, and neuropathology showed the findings of PML. This case was also notable because of the rapid progression despite improved immune status with antiretroviral therapy.

AIDS-Related Opportunistic Infections↗
PubMed2002

Posterior reversible encephalopathy syndrome due to severe hypercalcemia.

Posterior reversible encephalopathy syndrome (PRES) is a leukoencephalopathy clinically characterized by headache, altered mental status, visual loss and seizures. Neuroimaging demonstrates symmetrical posterior cortical and subcortical lesions. The exact pathophysiology is unknown but there is a strong association with immunosuppressants and hypertension. We report two cases of PRES in normotensive patients with severe hypercalcemia as the only identifiable cause. Possible pathophysiological mechanisms are discussed.

Aged↗
PubMed2002

Motor deficits cannot explain impaired cognitive associative learning in cerebellar patients.

There is a strong evidence that the cerebellum is involved in associative motor learning. The exact role of the cerebellum in motor learning, and whether it is involved in cognitive learning processes too, are still controversially discussed topics. A common problem of assessing cognitive capabilities of cerebellar patients is the existence of additional motor demands in all cognitive tests. Even if the patients are able to cope well with the motor requirements of the task, their performance could still involve compensating strategies which cost them more attentional resources than the normal controls. To investigate such interaction effects of cognitive and motor demands in cerebellar patients, we conducted a cognitive associative learning paradigm and varied systematically the motor demands and the cognitive requirements of the task. Nine patients with isolated cerebellar disease and nine matched healthy controls had to learn the association between pairs of color squares, presented centrally on a computer monitor together with a left or right answer button. In the simple motor condition, the answer button had to be pressed once and in the difficult condition three times. We measured the decision times and evaluated the correctly named associations after the test was completed. The cerebellar subjects showed a learning deficit, compared to the normal controls. However, this deficit was independent of the motor difficulty of the task. The cerebellum seems to contribute to motor-independent processes, which are generally involved in associative learning.

Adult↗
PubMed2002

Fear conditioned changes of heart rate in patients with medial cerebellar lesions.

Fear conditioned changes of heart rate and skin conductance responses were investigated in patients with medial cerebellar lesions. A classical conditioning paradigm with a tone as the conditioned stimulus (CS) and an electrical shock as the unconditioned stimulus (US) was tested on five patients with medial cerebellar lesions due to surgery for astrocytoma and five controls. The CS preceded the US by 5900 ms and coterminated with the US. Changes in heart rate and skin conductance responses were obtained as measures for autonomic fear responses. Effects of conditioning were quantified by comparison of the habituation and extinction phases. Controls, but not cerebellar patients, showed a significant decrease of heart rate during fear conditioning. However, there were no significant fear conditioned changes in electrodermal responses in either group. In summary, the medial cerebellum seems to be involved in fear-conditioned bradycardia in humans.

Adolescent↗
PubMed2001

Analysis of microsatellite polymorphism in red deer, roe deer, and fallow deer -- possible employment in forensic applications.

DNA microsatellites play a major role in population genetics, linkage mapping, and parentage studies of mammals. In addition, they may be used for forensic purposes, if an individual identification of a specific animal is necessary. Therefore, we tested a variety of microsatellite polymorphism derived from reindeer (Rangifer tarandus) by PCR and sequencing analysis for use in red deer (Cervus elaphus), roe deer (Capreolus capreolus) and fallow deer (Dama dama). Twelve of these microsatellites were selected for further analysis. In all these microsatellite polymorphism short tandem repeats could be detected for one or all three species as shown by sequencing analysis. In red deer, more than two alleles were found in eight microsatellites, in roe deer more than two alleles could be demonstrated in seven microsatellites, whereas in fallow deer more than two alleles were found in only two microsatellite polymorphism. A comparison of sequences of PCR products from the three deer species with the sequences of reindeer revealed several differences between the four species. In six microsatellites -- selected because or their reliability in PCR and because of their polymorphic character -- we established a sequenced allelic ladder and give population data of all three species from 82 deer of the Northeast region of Germany (Vorpommern). Our results show the possibility to use microsatellite polymorphism in the identification of deer in forensic applications like poaching.

Alleles↗
PubMed2001

Cerebral aspergillosis: comparison of radiological and neuropathologic findings in patients with bone marrow transplantation.

Thirty-six lesions in six patients who died from cerebral Aspergillus infection after bone marrow transplantation (BMT) were studied with regard to signal intensity, contrast enhancement, size, and location. The diagnosis was confirmed in all cases by autopsy. Retrospective correlation of histopathological and radiological findings was possible for 14 lesions. Most of the lesions (22/36) had isointense to low signal intensity on T2-weighted images (T2WI). Histopathologically, hemorrhagic necrosis was determined in three of them. Areas of high signal intensity on T1-weighted images (T1WI) were related to gross hemorrhage. Two infarctions showed intravascular accumulation of fungal hyphae with secondary thrombosis of the vessel. The remaining 12 lesions had high signal intensity on T2WI and low on T1WI. Histopathologically, four were infectious and four were unspecific demyelinated lesions. In conclusion, cerebral aspergillosis typically presented with large lesions showing isointense to low signal intensity on T2WI that could have areas of high signal on T1WI. Contrast enhancement was only visible in 15 lesions, and the predominant locations were the subcortical white matter, the cerebellum, and the basal ganglia. Small lesions with high signal on T2WI and low signal on T1WI could not necessarily be related to Aspergillus infection.

Adolescent↗
PubMed2000

A possible role of the human cerebellum in conditioning of the jaw-opening reflex.

The role of the human cerebellum in classical conditioning of the jaw-opening reflex was investigated using positron emission tomography (PET) in healthy subjects. The jaw-opening reflex was elicited by electrical stimulation of the right corner of the mouth (unconditioned stimulus, US). The conditioned stimulus was a tone preceding the US and coterminating with the US. Changes of regional cerebral blood flow (rCBF) were correlated with the rate of conditioning per PET scan. Conditioning effects were present in one third of all subjects. In these subjects, a significant increase of rCBF in the ipsilateral, intermediate cerebellum was shown during ongoing conditioning. Thus, the intermediate cerebellum appears to be involved in classical conditioning of the jaw-opening reflex in humans.

Adult↗
PubMed2000

Involvement of the human medial cerebellum in long-term habituation of the acoustic startle response.

Animal studies have shown an involvement of the cerebellar vermis in long-term habituation of the acoustic startle response, but not in short-term habituation. The aim of the present study was to investigate whether short-term and long-term habituation of the acoustic startle response are impaired in patients with medial cerebellar lesions. Five patients with midline cerebellar lesions due to surgery for astrocytoma and ten healthy, age- and sex-matched subjects were studied. Subjects received 40 acoustic startle stimuli each day on five successive days. Peak amplitudes of the startle response recorded at the orbicularis oculi and the sternomastoid muscles were obtained. Data were analyzed for response decrement within the training session of one day (short-term habituation) and for a decrease in the startle response across the five training days (long-term habituation). Short- and long-term habituation of the startle response recorded at the sternomastoid muscles could be achieved in controls and in cerebellar patients. However, long-term habituation of the blink component of the acoustic startle response recorded at the orbicularis oculi muscles was significantly impaired in patients with cerebellar lesions compared with control subjects, whereas short-term habituation was preserved in both groups. The present findings suggest that the medial cerebellum is involved in long-term habituation of the blink component of the startle response in humans.

Adolescent↗
PubMed2000

MRI of intracranial toxoplasmosis after bone marrow transplantation.

Toxoplasma encephalitis was confirmed by biopsy in three patients with bone marrow (BMT) or peripheral blood stem-cell transplantation (PBSCT). All had MRI before antimicrobial therapy. The intensity of contrast enhancement was very variable. One patient had one large, moderately enhancing cerebral lesion and several smaller almost nonenhancing lesions. The second had small nodular and haemorrhagic lesions without any enhancement. The third had late cerebral toxoplasmosis and showed multiple lesions with marked contrast enhancement. The moderate or absent contrast enhancement in the two patients in the early phase of cerebral toxoplasmosis may be related to a poor immunological response, with a low white blood cell count in at least one patient. Both received higher doses of prednisone than the patient with late infection, leading to a reduced inflammatory response. In patients with a low leukocyte count and/or high doses of immunosuppressive therapy, typical contrast enhancement may be absent.

Adult↗
PubMed2000

Fear conditioned potentiation of the acoustic blink reflex in patients with cerebellar lesions.

OBJECTIVE: To investigate whether the human cerebellum takes part in fear conditioned potentiation of the acoustic blink reflex. METHODS: A group of 10 cerebellar patients (eight patients with lesions involving the medial cerebellum, two patients with circumscribed lesions of the cerebellar hemispheres) was compared with a group of 16 age and sex matched healthy control subjects. The fear conditioned potentiation paradigm consisted of three phases. During the first, habituation phase subjects received 20 successive acoustic blink stimuli. In the subsequent fear conditioning phase, subjects passed through 20 paired presentations of the unconditioned fear stimulus (US; an electric shock) and the conditioned stimulus (CS; a light). Thereafter, subjects underwent the potentiation phase, which consisted of a pseudorandom order of 12 trials of the acoustic blink stimulus alone, 12 acoustic blink stimuli paired with the conditioned stimulus, and six conditioned stimuli paired with the unconditioned stimulus. The EMG of the acoustic blink reflex was recorded at the orbicularis oculi muscles. The potentiation effect was determined as the difference in normalised peak amplitude of the blink reflex evoked by pairs of CS and acoustic blink stimuli and evoked by the acoustic stimulus alone. RESULTS: In the habituation phase, short term habituation of the acoustic blink reflex was preserved in all cerebellar patients. However, in the potentiation phase, the potentiation effect of the blink reflex was significantly reduced in patients with medial cerebellar lesions compared with the controls (mean (SD) potentiation effect (%), patients: -6.4 (15.3), controls: 21.6 (35.6)), but was within normal limits in the two patients with lateral lesions. CONCLUSIONS: The present findings suggest that the human medial cerebellum is involved in associative learning of non-specific aversive reactions-that is, the fear conditioned potentiation of the acoustic blink reflex.

Adolescent↗
PubMed2000

Incidence and prevalence of neurological disorders associated with HIV since the introduction of highly active antiretroviral therapy (HAART).

OBJECTIVE: To determine the change of incidence and prevalence of neurological disorders caused by the human immunodeficiency virus (HIV) and opportunistic infections in HIV positive patients under treatment since the introduction of highly active antiretroviral therapy (HAART). METHODS: The data of all HIV infected patients were retrospectively analysed, who were examined in the HIV outpatients clinic of the neurological department of the University Clinic Essen between 1995 and 1998 (n=563, total number of visits=735). Data from identified patients were divided into two groups according to the time of examination from 1995 to 1996 (334 visits) and from 1997 to 1998 (401 visits). The incidence and prevalence of neurological disorders were statistically compared between both time intervals. RESULTS: Significantly more patients received HAART in 1997-8 (p<0. 001) and mean CD4+ cell count was significantly higher in 1997-8 (p<0.001). The prevalence of HIV associated dementia and HIV associated polyneuropathy were significantly lower in 1997-8 (both: p=0.02) and the incidence of toxoplasma encephalitis decreased from 5.7% in 1995-6 to 2.2% in 1997-8 (p=0.015). Based on the small number of patients significant changes in HIV associated myopathy, progressive multifocal leukoencephalopathy, cryptoccocal meningitis, and cytomegalovirus-encephalitis could not be detected. CONCLUSION: The prevalence of the most frequent HIV associated neurological disorders and incidence of toxoplasma encephalitis decreased since the introduction of HAART. This may be due to the improvement of immunostatus by HAART as demonstrated by the higher CD4+ cell count in the later time interval. Direct antiretroviral effects within the nervous system may be considered causative as well. The prevalence and incidence of HIV associated neurological disorders and opportunistic CNS infections decreased after introduction of HAART.

Adult↗
PubMed1999

Opportunistic CNS infection after bone marrow transplantation.

We retrospectively identified opportunistic CNS infections in 655 patients who had undergone allogeneic, syngeneic or autologous BMT or PBSCT between 1990 and 1997. Twenty-seven patients (4%) developed CNS infections. All CNS infections occurred in allogeneic BMT or PBSCT patients. The most common CNS infections were toxoplasma encephalitis (74%) and cerebral aspergillosis (18%). Furthermore, we identified one patient with candida encephalitis and one patient with viral encephalitis. Overall mortality of patients with opportunistic CNS infection was 67%. There were two different groups of toxoplasma encephalitis with a different appearance on MR imaging. The first group showed edema, but no gadolinium enhancement, whereas the second group exhibited typical MRI appearances with the exception of frequent hemorrhagic transformation. The first group had a significant shorter latency between BMT and onset of CNS infection (mean 45 days vs 180 days, P = 0.02), a significant higher daily dose of corticosteroids as treatment for graft-versus-host disease (GVHD) (P = 0.01), more severe GVHD and a higher mortality (71% vs 36%). This study shows that the most common CNS infections in our patient population are toxoplasma encephalitis and cerebral aspergillosis, that there are two distinct subgroups of toxoplasma encephalitis and that CNS infections occur after allogeneic BMT only.

Adolescent↗
PubMed1999

Treatment of alcohol withdrawal syndrome with gabapentin.

Four in-patients with moderate alcohol-withdrawal syndromes benefited from treatment with gabapentin administered in an add-on fashion to clomethiazole. In comparison with the amount of clomethiazole required as estimated using a specially developed score during previous detoxifications of these patients at our hospital, gabapentin (400 mg q.i.d.) clearly reduced the amount of clomethiazole needed now Gabapentin, an anticonvulsant with favorable pharmacokinetic properties and tolerability, and with no known risk of dependence, may therefore be a useful new drug in the treatment of alcohol withdrawal. We believe that the potential value of gabapentin in alcohol withdrawal deserves further controlled studies.

Acetates↗