Biomedical subjects

L L Baker

Publications and source records attributed to L L Baker.

46 records · Page 3Linked to original sources

PubMed1984

Characterization of synaptic potentials in hindlimb extensor motoneurons during L-DOPA-induced fictive locomotion in acute and chronic spinal cats.

Intracellular recordings were carried out in extensor hindlimb motoneurons during L-DOPA-induced fictive locomotion from acute and chronically spinalized cats. It was demonstrated that motoneurons in chronic animals exhibited irregularly occurring, high frequency discharges within a given burst of a spike train, and sporadic membrane potential depolarizations and hyperpolarizations correlated with extensor and flexor nerve filament activity, respectively, during the locomotor cycle. In contrast, motoneurons recorded from acute cats demonstrated smooth membrane potential fluctuation and regularly occurring low frequency spike discharges. These results indicate that the pharmacologically activated central pattern generator (CPG) for locomotion in young adult chronic cats spinalized at two weeks of age produces disorganized locomotor-like patterns in the absence of sensory feedback. It is suggested that the above-mentioned characteristics of membrane potential fluctuations and spike discharges are not due to alterations in the motoneuron membrane properties, but instead are due to changes in the inputs to the motoneurons.

Animals↗

PubMed1984

L-dopa-induced locomotor-like activity in ankle flexor and extensor nerves of chronic and acute spinal cats.

The ability of L-DOPA and nialamide to produce locomotor-like rhythmic discharges (fictive locomotion) in hind limb nerves of acute and chronically spinalized and paralyzed cats was examined. Ankle flexor and extensor nerves of chronic cats exhibited pharmacologically induced alternate bursts of activity that had significantly shorter cycle times and burst durations than those produced in ankle flexor and extensor nerves of acutely prepared cats. Furthermore, prior to pharmacologic activation, both ankle flexor and extensor nerves of chronic preparations frequently exhibited spontaneous alternate bursts of activity. Neuronal discharges from nerves of chronic preparations, both prior to and after pharmacologic activation, exhibited much greater variability in both cycle time and burst duration compared with those observed in acute preparations.

Action Potentials↗

PubMed1984

Functional test for the hemiparetic upper extremity.

A test, called the Functional Test, that evaluates the integrated function of the total upper extremity of an adult hemiparetic patient has been developed. It was used with 82 patients admitted to Rancho Los Amigos Hospital for stroke rehabilitation, together with a battery of six objective test measures. Sequential testing by two examiners demonstrated that the test had interrater reliability. The Functional Test score accounted for 87 percent of the variation in the scores achieved by the patients on the six separate objective measures. This tool integrates the information from these objective assessments and appears to be a valid measure of functional use of the hemiparetic upper extremity. The test can be administered in approximately 30 minutes, can be used in different treatment settings, and provides an accurate and immediate assessment of upper extremity capabilities.

Adult↗

PubMed1983

Neuromuscular electrical stimulation for the head-injured patient.

Recent research has shown that electrical stimulation is effective in treatment programs designed to maintain or gain range of motion, to facilitate voluntary motor control, and to strengthen muscles weakened by disuse. All of these treatment goals are relevant to the head-injured patient who frequently demonstrates profound disuse atrophy, joint contractures with excessive muscle tone, and decreased voluntary motor capabilities. As the cognitive status of the head-injured patient improves, electrical stimulation can be incorporated into traditional treatment programs to enhance their effectiveness. This article discusses using neuromuscular electrical stimulation with programs aimed at managing contractures, reducing spasticity, and facilitating voluntary motion. The limitations of electrical stimulation in the head-injured patient population are addressed.

Adult↗

PubMed1979

Electrical stimulation of wrist and fingers for hemiplegic patients.

Passive cyclical electrical stimulation was applied during a four-week treatment program to the wrist and finger extensors of 16 hemiplegic patients with flexor spasticity. The study noted the effects of this treatment on the patients' sensation; spasticity; passive range of motion of the wrist, metacarpophalangeal, and proximal interphalangeal joints; and strength in the wrist extensor muscles. Patients were divided into chronic and subacute groups. Both groups received electrical stimulation for three half-hour periods a day, seven days a week, as a substitute for all other range-of-motion techniques. Flexion contractures were prevented in the subacute group of patients at the wrist, metacarpophalangeal, and proximal interphalangeal joints. A statistically and clinically significant increase in wrist extension range occurred in the chronic group that had wrist flexion contractures before the electrical stimulation. Increased extension was noted at the metacarpophalangeal and proximal interphalangeal joints of patients in the chronic group. Those patients with some voluntary wrist extension before the treatment began were able to increase their extension strength during stimulation. No changes in skin sensation were noted and only a general trend in decreasing spasticity was apparent.

Adult↗

PubMed1979

Positional feedback and electrical stimulation: an automated treatment for the hemiplegic wrist.

Positional feedback (PF) and electrical stimulation were combined in a new treatment modality for facilitating wrist extension in stroke patients. Thirty adult hemiparetic patients lacking normal voluntary wrist extension were randomly placed in control and study groups. The control group received conventional therapy while the study group received positional feedback stimulation training (PFST) in addition to conventional treatment. At the end of the 4-week program, study patients showed a 280% increase in isometric extension torque when the wrist was positioned in 30 degrees of extension and 70% increase when positioned in 30 degrees of flexion. Control patients showed no significant changes in torque. Study patients made an average 200% gain in selective range of motion over their starting levels while controls made only a 50% increase. Treatment using automated PFST equipment allows controlled repetitive isotonic exercise and facilitation of wrist extension without continuous one-on-one therapist/patient supervision.

Automation↗

PubMedDate not supplied

Effect of electrical stimulation waveform on healing of ulcers in human beings with spinal cord injury.

Various electrical stimulation waveforms have been used to enhance wound healing, with little consideration for potential differences in their physiologic effect. The present study evaluated the effect of stimulation waveform and electrode placement on wound healing. Eighty patients with spinal cord injury and one or more pressure ulcers were treated. A total of 185 ulcers received 45 minutes of stimulation daily. Each ulcer was subjected to one of four treatment protocols: asymmetric biphasic waveform, symmetric biphasic waveform, microcurrent stim-ulation, or a sham control protocol. Electrodes were placed outside the wounds, over intact skin and surrounding the area of the ulcer. Data were categorized by ulcers which healed during the protocol and those which did not. Analysis of the "good response" ulcers (n = 104) showed significantly better healing rates for those receiving stimulation with the asymmetric biphasic waveform, compared with the control and microcurrent groups. Mean healing rates from the present study were similar to previously reported measures. The waveforms studied possessed minimal polar capabilities, and the electrodes were placed outside the wound. These data show that electrical stimulation clearly enhanced healing of pressure ulcers in a significant number of individuals with spinal cord injury; the physiologic implications of these findings relative to the mechanism(s) by which electrical stimulation enhances wound healing are discussed. However, extrapolation of these results to patients with other types of wounds must await further study.

Journal Article↗

PubMedDate not supplied

Effect of electrical stimulation on foot skin perfusion in persons with or at risk for diabetic foot ulcers.

The failure of foot wounds to heal results in 54,000 people with diabetes having to undergo extremity amputations annually. Therefore, treatment is needed to speed healing in people with diabetes in order to reduce the need for amputation. This study tested the effect of high-voltage pulsed current on foot blood flow in human beings who are at risk for diabetic foot ulcers. Neuropathy, vascular disease, Wagner Class, glucose, gender, ethnicity, and age were measured. A sample of 132 subjects was tested using a repeated-measures design. A baseline transcutaneous oxygen level was obtained; stimulation was applied, and transcutaneous oxygen measurements were recorded at 30- and 60- minute time intervals. The grouped foot transcutaneous oxygen levels decreased (F = 5.66, p =. 0039) following electrical stimulation. Analysis of variance (Scheffe, p <.05) showed that initial transcutaneous oxygen was significantly higher than subsequent readings. However, oxygen response was distributed bimodally: 35 (27%) subjects showed increased transcutaneous oxygen (mean 14.8 mm Hg), and 97 (73%) experienced a decreased transcutaneous oxygen reading (mean 12.2 mm Hg). Logistic regression analysis did not explain these differences. Although this treatment appears to increase blood flow in a subset of patients, further study is needed to identify probable mechanisms for this response.

Adult↗

PubMedDate not supplied

The large temporal horn: MR analysis in developmental brain anomalies versus hydrocephalus.

PURPOSE: To utilize MR to delineate the morphologic abnormalities of the temporal horn and adjacent structures in patients with congenital brain anomalies and to differentiate these findings from the temporal horn alterations in obstructive hydrocephalus. PATIENTS AND METHODS: Thirty-six patients were included in this retrospective study, including eight with agenesis of the corpus callosum (ACC), four with lissencephaly (lis), four with lobar holoprosencephaly (holo), as well as 20 with isolated obstructive hydrocephalus due to tumor (17 patients) or aqueductal stenosis (three patients). Twenty patients with normal scans were included as controls. RESULTS: Coronal plane image analysis showed that 75% of patients with brain anomalies had enlargement of the temporal horns, most prominently involving the inferolateral aspects of the ventricle (8/8 ACC, 4/4 lis, 0/4 holo). Hippocampal formations were small in 62% (6/8 ACC, 3/4 lis, 1/4 holo). An abnormal, vertical orientation (incomplete inversion) of the hippocampal formations was observed in 82% (8/8 ACC, 4/4 lis, 1/4 holo). Focal thinning of the white matter lateral to the temporal horn was seen in 50% (8/8 ACC, 0/4 lis, 0/4 holo). All patients with isolated obstructive hydrocephalus showed enlargement of the temporal horns, most pronounced in the superior-lateral region. Hippocampal formations showed normal, horizontal orientation (complete inversion) and were of normal size in 17 of 20 patients; the only exceptions included patients with severe hydrocephalus where the hippocampi were flattened along the inferior margin of the temporal horn. Temporal lobe white matter was normal in the 17 patients with mild or moderate hydrocephalus: diffuse white matter thinning inferolaterally was observed in the three patients with severe hydrocephalus. Distinct differences were present in the morphology of the temporal horn and surrounding brain in congenital brain disorders compared with those in patients with hydrocephalic. The anomalous brains showed enlargement as a result of incomplete development, and the hydrocephalic brains showed enlargement as a result of increased intraventricular pressure. CONCLUSION: Temporal horn enlargement in lissencephaly and agenesis of the corpus callosum should not be misinterpreted as hydrocephalus. Analysis of temporal lobe morphology will allow differentiation if doubt exists.

Adolescent↗

PubMedDate not supplied

Hemangiomas and vascular malformations of the head and neck: MR characterization.

PURPOSE: To characterize the MR appearance of the common hemangioma of infancy as well as low- and high-flow vascular malformations of the head and neck. PATIENTS AND METHODS: Twenty patients with vascular lesions of the head and neck proved either by pathology, angiography, and/or unequivocal clinical diagnosis were included. Vascular lesions included 15 low-flow lesions (four hemangiomas, 10 venous malformations, one lymphatic malformation), and five high-flow lesions (three arteriovenous malformations (AVMs) and two invasive combined malformations). All patients had MR studies (generally 1.5 T using routine T1- and T2-weighted spin-echo sequences). Nine had postgadolinium, gradient recalled-echo, CT, and/or angiographic studies. FINDINGS: Deep hemangiomas and venous malformations demonstrate intermediate signal in T1-weighted images, heterogeneous high signal on T2-weighted images, and prominent enhancement. Involuting hemangiomas show focal areas of high signal intensity on T1-weighted images due to fatty replacement. Venous malformations may demonstrate venous lakes seen as homogeneous regions of high signal intensity on T2-weighted images and phleboliths seen as low signal foci. The one patient with lymphatic malformation showed a large multicystic submandibular mass with large hemorrhage-fluid levels. Features of high-flow lesions (AVMs) include serpiginous signal voids, absence of a dominant mass, and intraosseous extension with decreased marrow signal on T1-weighted images. Invasive combined vascular malformations showed serpiginous flow voids and infiltrative solid masses. Low-flow lesions (hemangiomas, venous, and lymphatic malformations) demonstrate distinct MR findings allowing their differentiation from high-flow lesions (AVMs). Deep hemangiomas and venous malformations appear as solid masses and may look identical. Venous lakes and phleboliths are features of venous malformations which, when present, may help in diagnosis. Combined vascular malformations share features of both low- and high-flow malformations. CONCLUSION: MR is useful in delineating the extent of disease and differentiating low- and high-flow vascular lesions.

Adolescent↗