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Biomedical subjects

M Faist

Publications and source records attributed to M Faist.

28 records · Page 2Linked to original sources
PubMed1996

Biceps femoris tendon jerk reflexes are enhanced at the end of the swing phase in humans.

The phase-dependent modulation of the biceps femoris (BF) tendon jerk reflexes was investigated in a reduced form of walking. All subjects (12) investigated showed tendon reflexes throughout the whole step cycle but the amplitude was largest in the middle and late swing phase of the ipsilateral leg. It is concluded that the normally occurring BF burst at end swing could be due to stretch-induced activity.

Electromyography↗
PubMed1996

Modulation, probably presynaptic in origin, of monosynaptic Ia excitation during human gait.

Modulation of presynaptic inhibition of Ia afferents projecting monosynaptically to soleus motoneurones was investigated during human gait. Changes in presynaptic inhibition of Ia afferents were deduced from alterations in the amount of heteronymous soleus H-reflex facilitation evoked by a constant femoral nerve stimulation. It has been shown that this facilitation is mediated through a monosynaptic Ia pathway and that during its first 0.5 ms it is still uncontaminated by any polysynaptic effect and can be used to assess ongoing presynaptic inhibition of Ia terminals to soleus motoneurones. During gait, heteronymous facilitation was reduced with respect to its control value (rest during sitting) and modulated during the step cycle: it reached its maximum at mid-stance and decreased to near zero by the end of stance. At the same time the H-reflex amplitude was to some extent similarly modulated. It is argued that this decrease in heteronymous Ia facilitation and in H-reflex amplitude reflects an increased, ongoing presynaptic inhibition of Ia terminals projecting onto soleus motoneurones, which could be from central and/or peripheral origin. D1 inhibition, i.e. the late and long-lasting inhibition of the soleus H-reflex evoked by a train of stimuli to the common peroneal nerve, was used as another method to assess presynaptic inhibition. This D1 inhibition was decreased during gait, and it is argued that this decrease might reflect an occlusion in presynaptic pathways or increased presynaptic inhibition of pathways mediating the conditioning volley.

Adult↗
PubMed1996

Stereotactic management of lesions of the pineal region.

OBJECTIVE: The relevance of the computed tomography-guided stereotactic approach for the management of lesions of the pineal region is analyzed. METHODS: In a retrospective analysis conducted between 1985 and 1993, the risk profile, the diagnostic accuracy, and the therapeutic relevance of the stereotactic approach in 106 patients was studied. Survival analysis was used to assess the reliability of the stereotactically obtained diagnosis in terms of follow-up observation. RESULTS: A histological diagnosis was obtained in 103 of the 106 patients. In three patients, a conclusive diagnosis could not be established because of intraoperative complications. One lesion was misdiagnosed as a pineocytoma instead of a pineoblastoma. Two of the 106 patients died; 9 patients experienced perioperative morbidity. In 38 patients, the stereotactic approach was also useful for therapy. Cyst aspiration and/or internal drainage was performed in 18 patients with symptomatic cystic lesions, and radiosurgical treatment with use of interstitial 125iodine was performed in 16 patients with low-grade tumors and in 4 patients with solitary metastases. In 12 patients, the obtained tissue diagnosis was the basis for deferring additional therapy. In 43 patients with germ-cell tumors, pineoblastomas, or malignant gliomas, a stereotactic biopsy was the starting point for additional radiotherapy/chemotherapy. Open tumor resection played a minor role (five patients). CONCLUSION: The stereotactic approach to the pineal region is a relatively safe procedure in experienced hands. The diagnosis obtained by computed tomography-guided stereotactic biopsy is a valid basis for treatment decisions. Long-term follow-up observation of the benign lesions is necessary for a definite confirmation of diagnostic accuracy.

Adolescent↗
PubMed1995

Interstitial radiosurgery of low-grade gliomas.

The treatment of patients with low-grade gliomas remains a subject of controversy, especially with respect to new treatment modalities such as interstitial radiosurgery (brachytherapy), radiosurgery, and stereotactic radiotherapy. In a retrospective analysis conducted between 1979 and 1991, the authors studied the results of interstitial radiosurgery in 455 patients with low-grade gliomas (World Health Organization (WHO) Grade I+WHO Grade II) with regard to survival time, quality of life, the risk of malignant transformation, and the risk profile of the treatment concept. Interstitial radiosurgery with iodine-125 was performed using permanent (1979-1985) or temporary implants (after 1985) with low-dose rates (< or = 10 cGy/hr) and a reference dose of 60 to 100 Gy calculated to the outer rim of the tumor. The 5- and 10-year survival rates in patients with pilocytic astrocytomas (97 patients) were 84.9% and 83%, and in patients with WHO Grade II astrocytomas (250 patients) 61% and 51%, respectively. Five-year survival rates for patients with oligoastrocytomas (60 patients), oligodendrogliomas (27 patients), and gemistocytic astrocytomas (21 patients) were 49%, 50%, and 32%, respectively. In the group with WHO Grade II gliomas, young age and a good performance status were associated with a better prognosis. Unfavorable factors were midline shift, enhancement on computerized tomography (CT) scan, and tumor recurrence after previous radiotherapy or surgery. Tumor location had no influence on the prognosis (247 patients in this series had deep-seated tumors). Malignant transformation was the major cause of death. Important risk factors for malignancy were the patient's age, tumor enhancement in CT scan, and tumor recurrence after previous surgery or radiotherapy. Perioperative mortality was 0.9% and perioperative morbidity was 1.7%. Radiogenic complications were observed in 2.7% of all patients, most often in larger tumors and after using permanent implants. The authors conclude that interstitial radiosurgery represents a specific treatment modality for selected patients with unifocal circumscribed low-grade gliomas with a diameter of less than 4 cm in any location. The efficacy of this treatment lies in the same range as the best results after surgery and radiotherapy.

Adolescent↗
PubMed1994

Interstitial 125-iodine radiosurgery of low-grade gliomas of the insula of Reil.

Between 1979 and 1991 67 patients with low-grade gliomas of the insula (of Reil) were treated with 125-iodine interstitial radiosurgery. Retrospective analysis with a median follow-up of 55 months demonstrated a 5- and 10-year survival rate of 54% and 47%, respectively, for all low-grade gliomas treated and a 5- and 10-year survival rate of 57% for 49 patients with astrocytomas WHO grade II analysed separately. The median Karnofsky performance status of survivors was 90%. Malignant change was the cause of death in 85%, failure to control tumour growth in the remaining cases. Multivariate analysis with a Cox proportional hazard model identified solely the pre-operative Karnofsky performance score of 70-80 vs. 90% as a prognostic factor for outcome (p = 0.001, risk ratio 3.62), but not age, gender, tumour volume, length of disease before treatment, mode of implantation, or major vs. moderate or no shrinkage of tumour volume after interstitial radiosurgery. Thus, 125-iodine radiosurgery yielded survival rates in these deep-seated insular gliomas comparable to those reported after surgery and radiation therapy of lobar tumours. This was achieved with a low peri-operative mortality and morbidity and at low costs.

Adolescent↗
PubMed1994

A quantitative assessment of presynaptic inhibition of Ia afferents in spastics. Differences in hemiplegics and paraplegics.

Soleus H-reflex facilitation evoked by a supramaximal conditioning stimulation to the femoral nerve was investigated in 28 healthy control subjects and 35 spastic patients of whom 17 were paraplegics with bilateral spinal cord lesion and 18 were hemiplegics with unilateral cerebral lesion. Heteronymous facilitation from quadriceps to soleus was measured 0.4 ms after onset, while the monosynaptic Ia excitation is still uncontaminated by any non-monosynaptic effect and can be used to assess ongoing presynaptic inhibition on Ia terminals to soleus motor neurons. In paralegics, this heteronymous Ia facilitation was significantly larger than in control subjects (all individual results in these patients being above the mean observed in controls). This must reflect a decrease in presynaptic inhibition of Ia terminals in the paraplegics explored here. There was no correlation between this decreased presynaptic inhibition of Ia terminals and the degree of spasticity measured by Ashworth's scale. Surprisingly, the amount of heteronymous Ia facilitation in hemiplegics was the same as in normal subjects. This indicates that presynaptic inhibition of Ia terminals is unchanged in these patients and disagrees with the usual interpretation of reduced vibratory inhibition of the soleus H-reflex in hemiplegics. It is argued that this disagreement is due to the fact that vibratory inhibition of the reflex also depends on post-activation depression following repetitive synaptic transmission.

Adult↗
PubMed1992

Distribution of heteronymous Ia facilitation and recurrent inhibition in the human deltoid motor nucleus.

Distribution of heteronymous Ia facilitation and of heteronymous recurrent inhibition in motoneurones innervating the anterior part of the deltoid muscle were investigated in normal human subjects following electrical stimulation of the nerves innervating the main muscles of the upper limb. Activation of group I afferents originating from deltoid, biceps, triceps and extensor carpi radialis (ECR) muscles resulted in an early increase in firing probability of voluntarily activated motor units belonging to the anterior part of the deltoid muscle whereas activation of motor axons supplying deltoid, triceps, ECR and flexor carpi radialis (FCR) muscles resulted in an early and long-lasting decrease in firing probability. No effect was seen following activation of group I afferents and motor axons contained in the ulnar nerve. The characteristics of the early facilitation suggest that it is at least partly due to heteronymous Ia monosynaptic connections while these of the long-lasting inhibition suggest that it is at least partly due to heteronymous recurrent inhibition. Their patterns of distribution are discussed with regards to the functional role of the human deltoid.

Adult↗
PubMed1990

Amplitude modulation of the quadriceps H-reflex in the human during the early stance phase of gait.

Amplitude modulation of the quadriceps H reflex was investigated during the early part of the stance phase of gait in normal human subjects. Stability of the M wave was used to ensure constancy of the effective stimulus strength. In all subjects there was a progressive decrease in the reflex amplitude throughout the early knee flexion (yield of the knee), whereas the quadriceps EMG activity remained constant or even increased. At an equal stimulus strength and EMG level, the reflex was often larger at the onset of the stance phase of gait than during voluntary contraction, whereas it was always smaller during the knee extension following the yield of the knee. It is argued that changes in presynaptic inhibition of quadriceps Ia terminals could account for this amplitude modulation of the monosynaptic reflex during gait. The possible role of changes in the gain of the quadriceps stretch reflex during bipedal gait is discussed.

Gait↗
PubMed1990

Amplitude modulation of the human quadriceps tendon jerk reflex during gait.

Amplitude modulation of the quadriceps tendon jerk reflex was investigated during the step cycle in normal human subjects. Reflex amplitude was compared with that obtained during a control stance condition, with "equivalent" levels of EMG activity and limb position. During gait there was a progressive decrease in the reflex amplitude early in the stance phase, i.e. during yielding of the knee, and it remained reduced throughout the step cycle. This pattern of changes in reflex amplitude correlated with neither the quadriceps EMG activity nor with the knee joint movements. The behavior of the tendon reflex was similar to that described for the modulation of the quadriceps H-reflex during the early stages of the stance phase of gait. In the latter study it was argued that changes in presynaptic inhibition of quadriceps la terminals could account for the amplitude modulation. We conclude that there is no dramatic change in the gamma drive to quadriceps muscle spindles: tendon reflexes are modulated during the step cycle in much the same way as H-reflexes, in spite of the peripheral and central differences between them. Similar behavior has been described for the soleus H-reflex and Achilles tendon reflex during gait although the modulation of these reflexes followed a different pattern than that seen in the quadriceps.

Achilles Tendon↗