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Biomedical subjects

A Lindner

Publications and source records attributed to A Lindner.

At least 19 recordsLinked to original sources
PubMed2002

Brainstem infarctions with normal MRI.

Most studies on brainstem infarctions included only patients with lesions documented by CT or MRI. The aim of this study was to analyse the clinical symptomatology in patients with the classical signs of brainstem infarcts and normal MRI results. Frequencies of MR-positive and negative infarctions should be analysed according to their location. In a series of 30 consecutive patients with acute clinical symptoms of ischemic brainstem lesions and persistence of the symptomatology for more than 10 days, 8 patients had normal MRI. In these patients the location of the lesion was established by clinical and electrophysiological criteria. The lesions in the 8 patients with normal MRI were situated in medulla oblongata (n=3), in pons (n = 2), and in midbrain (n = 3). In each of these patients the clinical symptoms corresponded to one of the classical alternating syndromes, which are pathognomic for brainstem infarctions (1 Wallenberg, 1 Avellis, 1 Jackson, 2 Millard-Gubler, and 3 Weber). The clinical course of the infarctions with normal MRI was favourable, the symptoms disappeared within few weeks. Our study proved that the clinical diagnosis of brainstem infarction, particularly in lesions of midbrain and caudal tegmentum pontis, can not be excluded by normal MRI.

Aged↗
PubMed2002

Effects of repeated biopsying on muscle tissue in horses.

The collection of muscle samples in horses to estimate their performance potential, adaptations to training and diagnosis of exertional myopathies is of increasing interest. This study was designed to examine whether repeated biopsying of the gluteus medius muscle at 7 week intervals alters morphology and muscle fibre variables in the sampling area. The gluteus had been biopsied 3 times previously, each biopsy separated by a 7 week interval. Seven weeks after the last biopsy, this study was initiated. Percutaneous needle biopsies were taken from left and right muscles at 2 depths (2 and 6 cm) and at 2 sites for each depth (22 and 25 cm from the tuber coxae) of 7 mature Thoroughbreds. The 22 cm site was located close (2 cm caudal) to an area of the muscle that had been biopsied previously. The 25 cm site was 5 cm apart from this area. A total of 52 samples were available for histology, electron microscopy and immunohistochemistry. The latter was used to study percentages, sizes and capillaries of muscle fibre types. Most muscle samples collected (75%) had normal morphology, but the remaining 25% showed signs of muscle repair. In some circumstances, they showed regenerative signs of complete muscle repair, while in others ineffective muscle repair (scar formation) was evident. Nevertheless, sufficient normal tissue was always available for measuring routine muscle variables. Samples collected 3 cm laterally apart showed large differences with regard to muscle fibre type variables examined. These results show that repeated muscle samples in intervals of 7 weeks do not have effects that would impair evaluation of muscle fibre variables for diagnosis of effectivity of conditioning programmes. Furthermore, they emphasise that the only way of keeping variations through sample collection technique small is to standardise all biopsying techniques accurately.

Animals↗
PubMed2001

Optimizing visual motion perception during eye movements.

We usually perceive a stationary, stable world and we are able to correctly estimate the direction of heading from optic flow despite coherent visual motion induced by eye movements. This astonishing example of perceptual invariance results from a comparison of visual information with internal reference signals predicting the visual consequences of an eye movement. Here we demonstrate that the reference signal predicting the consequences of smooth-pursuit eye movements is continuously calibrated on the basis of direction-selective interactions between the pursuit motor command and the rotational flow induced by the eye movement, thereby minimizing imperfections of the reference signal and guaranteeing an ecologically optimal interpretation of visual motion.

Chi-Square Distribution↗
PubMed2001

Cortical substrates of perceptual stability during eye movements.

We are usually unaware of retinal image motion resulting from our own movement. For instance, during slow-tracking eye movements, the world around us remains perceptually stable despite the retinal image slip induced by the eye movement. This example of perceptual invariance is achieved by subtracting an internal reference signal, reflecting the eye movement, from the retinal motion signal. If the two cancel each other, visual structures, which do not move, will also be perceived as nonmoving. If, however, the reference signal is too small or too large, a false eye-movement-induced motion of the external world will be perceived. We have exploited our ability to manipulate the size of the reference signal in an attempt to reveal the structures in visual cortex, encoding the perception of self-induced visual motion rather than the retinal motion signal. Using EEG and lately also MEG recordings in human subjects and single-unit recordings in monkeys, we have been able to show that our ability to perceive the world as stationary despite eye-movement-induced retinal image slip is based on "late" parts of the cortical hierarchy of motion processing, sparing the early stages up to cortical area MT and, among others, involving cortex at the junction between the parietal and temporal lobes close to the parieto-insular-vestibular cortex. Lesions of this network in humans render the visual system unable to compensate for the visual consequences of eye movements, giving rise to severe dizziness, whenever the eyes move smoothly.

Animals↗
PubMed2001

Cancellation of self-induced retinal image motion during smooth pursuit eye movements.

When our eyes are tracking a target that is moving in front of a structured background, global motion of equal speed is induced in the opposite direction. This effect has been termed reafference, which, astonishingly, does not significantly affect the execution of such pursuit eye movements. Employing brief and unexpected injections of full-field motion during ongoing human smooth pursuit, we demonstrate that the sensitivity for full-field motion is reduced strongly in the direction opposite to the eye movement, i.e. the direction of reafferent background motion. Our experiments further characterize this asymmetry in visual motion processing and provide a preliminary explanation for the accuracy of the pursuit system despite self-induced motion.

Adult↗
PubMed2001

[Correlation of clinical and magnetic resonance imaging findings in patients with brainstem infarction].

The aim of this study was the comparison of clinical and neurological findings in 30 patients presenting with ischemic brainstem lesions. These were localized in the midbrain in 4 cases, in the medulla in 12 cases and in the pons in 11 cases, while the remaining three patients demonstrated combined lesions. Symptoms were lesions of the pyramidal tract in 77% of cases, vertigo in 57% of cases, speech disturbances in 40% of cases and gait ataxia in 37% of cases. Cranial nerve lesions were evident in 87% of patients, while 33% of patients demonstrated a Horner syndrome. Brainstem lesions were diagnosed in 22 (73%) of patients on magnetic resonance imaging, while all 30 patients had clinical signs suggestive of brainstem lesions. We conclude that neuroradiological studies can provide helpful information regarding patients with brainstem lesions, but by no means replace exact neurological examination.

Adult↗
PubMed2001

Factors affecting tube dwelling time after percutaneous nephrolithotomy.

BACKGROUND AND PURPOSE: Little is known about the impact of nephrostomy tubes on morbidity and quality of life. PATIENTS AND METHODS: The tube dwelling time and the factors influencing it were determined in 165 patients undergoing percutaneous nephrolithotomy (PCNL). RESULTS: The mean tube dwelling time was 21+/-30 days. The duration of tube drainage after PCNL was 13+/-17 days. Most of this time was preoperative when the tube was inserted for urgent reasons--obstruction or sepsis (31+/-33 days). On multivariate analysis, the number of secondary PCNLs and postoperative complications were the most significant factors affecting tube dwelling time. Age correlated with intubation time but did not reach statistical significance (P < 0.09). Neither the stone's side and type nor the patient's sex had a significant influence. CONCLUSIONS: A significant factor affecting the duration of tube drainage is preoperative medical evaluation and patient preparation, and these steps should be completed expeditiously in order to minimize the time to PCNL. Completion of PCNL in one session should shorten the postoperative intubation time.

Adult↗
PubMed2001

The impact of prostate biopsy on patient well-being: a prospective study of pain, anxiety and erectile dysfunction.

PURPOSE: We prospectively studied the impact of transrectal ultrasound guided prostate biopsy on patient well-being. MATERIALS AND METHODS: We enrolled 211 consecutive men who underwent a total of 218 biopsy events in a questionnaire based survey focusing on pain, anxiety and erectile dysfunction risk factors. Surveys were administered before, and immediately, 1 week and 1 month after biopsy. Quantitative information on the intensity of symptoms and signs was obtained using a uniform grading system. RESULTS: Intraoperative pain considered severe in 20% of the biopsy events was associated with pain in the first 24 hours postoperatively, leading to analgesic use in 10%. Inflammatory infiltrate in the biopsy core and younger patient age correlated with persistent pain on days 2 and 7 after biopsy, respectively. Preoperative anxiety was reported in 64% of biopsy events and predictive of intraoperative pain. Anxiety peaked before result disclosure. Erectile dysfunction attributed to anxiety in anticipation of biopsy was reported in 7% of cases. At days 7 and 30, 15% of previously potent patients reported erectile dysfunction. CONCLUSIONS: The impact of prostate biopsy on patient well-being begins while waiting for the scheduled procedure. Shortening the anticipation period before results are disclosed and administering pre-biopsy anxiety decreasing measures may benefit patients. Analgesic therapy is recommended in younger patients, those reporting moderate to severe intraoperative pain and those with known prostatic inflammatory infiltrate. The risk of acute erectile dysfunction should be discussed cautiously with patients who are potent before biopsy.

Adult↗
PubMed2001

The impact of prostate biopsy on patient well-being: a prospective study of voiding impairment.

PURPOSE: We studied the possible association of transrectal ultrasound guided prostate biopsy with voiding impairment. MATERIALS AND METHODS: A total of 211 consecutive patients were prospectively enrolled. International Prostate Symptom Score (I-PSS), subjective voiding complaints and retention were recorded in 3 personal interviews before biopsy, and on postoperative days 7 and 30. RESULTS: Of the 204 patients who voided via the urethra at biopsy 52 (25%) reported subjective voiding impairment on postoperative day 7, including 12% who defined difficult voiding as mild-1 to 2 points on a 0 to 5 scale, 8% as moderate-3/5 and 5% as severe-4 to 5/5. In 5 of the latter cases (2.5%) acute urinary retention necessitated urethral catheter insertion. Transition zone volume, which was 42 ml. or larger in all patients in urinary retention, was the only independent variable associated with patient report of subjective difficult voiding and acute urinary retention during week 1 after biopsy (p = 0.03). Baseline I-PSS greater than 20 points indicated a risk of an acute transient increase in I-PSS on postoperative day 7. CONCLUSIONS: Transient voiding impairment may be precipitated by ultrasound guided prostate biopsy. To decrease this morbidity appropriate evaluation and possible treatment for bladder outlet obstruction are justified in patients with a larger transition zone and in those with preoperative baseline I-PSS greater than 20 points.

Adult↗
PubMed2001

Cryosurgical ablation for prostate cancer: preliminary results of a new advanced technique.

BACKGROUND: Cryosurgery is a minimally invasive treatment option for prostate cancer. OBJECTIVES: To report on the first series of cryosurgical ablation for prostate cancer performed in Israel. METHODS: Cryosurgical ablation of the prostate was undertaken in 12 patients aged 53-72 diagnosed with adenocarcinoma of the prostate. The procedures were performed percutaneously and were monitored by real-time trans-rectal ultrasound. The CRYOHIT machine applying Argon gas was used with standard or ultra-thin cryoprobes. The average follow-up was 12.8 months postsurgery (range 1-24 months). RESULTS: No rectal or urethral injuries occurred and all patients were discharged from hospital within 24-48 hours. The duration of suprapubic drainage was 14 days in 10 patients and prolonged in 2. Early complications included penoscrotal edema in four patients, perineal hematoma in three, hemorrhoids in two and epidydimitis in one. Long-term complications included extensive prostatic sloughing in one patient and a perineal fistula in another, both of whom required prolonged suprapubic drainage. Minimal stress incontinence was noted in two patients for the first 8 weeks after surgery. None of the patients has yet regained spontaneous potency. A prostate-specific antigen nadir of less than 0.5 ng/ml was achieved in eight patients and an undetectable PSA level below 0.1 ng/ml in five patients. CONCLUSION: Cryoablation for prostate cancer is safe and feasible, and the preliminary results are encouraging. Further study is needed to elucidate the efficacy of the procedure.

Adenocarcinoma↗
PubMed2000

Viscous fingering in a yield stress fluid

We study the Saffman-Taylor or viscous fingering instability in yield stress fluids. The theory for yield stress fluids shows that the dispersion equation of the instability is similar to that for Newtonian fluids; however, the capillary number governing the instability now contains the yield stress. Experiments using gels and foams reveal very branched fingers in the gel. The results are in excellent agreement with theory for the gel, with, in addition, a crossover from yield stress dominated to viscous behavior. The results for foams are very different due to the existence of wall slip.

Journal Article↗
PubMed2000

[Erythema palmare hereditarium ("red palms")].

We report a woman with erythema palmare hereditarium, an anomaly not documented so far in the German literature. It is characterized by a bright erythema of the palms, usually persistent since birth. It is transmitted in an autosomal-recessive mode and has a benign course. In our patient it was possible to trace the palmar erythema over three generations.

Adult↗