ABSTRACT
We used the magnetic search coil technique to measure the horizontal cervico-ocular reflex (COR) of 8 subjects in response to transient or sinusoidal (0.1-1.0 Hz) trunk rotations while their heads were firmly immobilized. Although we were able to resolve eye rotations of < 0.05 degrees, the COR was hardly measurable (gain was always < 0.07). This finding, made with the most precise measurement technique used to date, suggests that the COR makes a negligible contribution to the stability of gaze in normal subjects during natural activities.
Subject(s)
Eye Movements , Neck Muscles/physiology , Reflex/physiology , Rotation , Adult , Humans , Male , Middle Aged , Movement , Posture , Reflex, Vestibulo-Ocular/physiology , Vestibule, Labyrinth/physiologyABSTRACT
The authors present two cases of 5-month-old children with early infantile Krabbe disease studied by CT and MR. Both infants had characteristic CT scans for the disease consisting of symmetric hyperdensity involving the cerebellum, thalami, caudate, corona radiata, and brain stem. One of the infants had a deceptively normal initial MR examination, with dramatic progression of the white-matter disease over the following 4 months.
Subject(s)
Leukodystrophy, Globoid Cell/diagnosis , Magnetic Resonance Imaging , Brain/diagnostic imaging , Brain/pathology , Female , Humans , Infant , Leukodystrophy, Globoid Cell/diagnostic imaging , Male , Tomography, X-Ray ComputedABSTRACT
We compared the reliability of asymmetry of forearm rolling (rotation of one forearm around the other in front of the torso) as a sign of unilateral cerebral dysfunction with that of other standard clinical tests. We studied 62 patients with radiologically confirmed unilateral cerebral lesions and 20 control subjects with normal imaging. Asymmetric forearm rolling was the most sensitive indicator of unilateral hemispheric disease (85%). This simple test is a useful addition to the neurologic examination.
Subject(s)
Brain Diseases/physiopathology , Forearm/physiopathology , Movement , Adult , Female , Forearm/physiology , Functional Laterality , Humans , Male , Middle AgedABSTRACT
During locomotion, the head is subject to rotational perturbations with fundamental frequencies in the range 0.5-5.0 Hz, and significant harmonics up to 20 Hz. Patients who have lost labyrinthine function complain of oscillopsia and visual impairment during locomotion. Measurements of head movements during walking and running in place in such patients indicate that head stability is similar to that in normal subjects. Therefore, head stability is mainly guaranteed by mechanical, not neurogenic, factors. On the other hand, the visual symptoms of such patients can be ascribed to instability of gaze. Thus, it seems that other mechanisms such as visual following, the cervicoocular reflex, or anticipatory eye movements cannot compensate for loss of the VOR during locomotion (though they may do so for lower-frequency or active head rotations). The indispensable role of the VOR during locomotion is probably a reflection of its short latency (16 mseconds or less in the horizontal and vertical planes), which guarantees short phase lags during high-frequency head rotations. Our results indicate that laboratory testing of patients with vestibular symptoms should employ stimuli that correspond to those occurring during locomotion.
Subject(s)
Ear, Inner/physiopathology , Reflex, Vestibulo-Ocular , Vestibule, Labyrinth/physiopathology , Aged , Aminoglycosides , Anti-Bacterial Agents/adverse effects , Arterial Occlusive Diseases/complications , Deafness/etiology , Deafness/physiopathology , Ear, Inner/physiology , Female , Head , Humans , Locomotion , Male , Middle Aged , Movement , Reference Values , Time Factors , Vestibule, Labyrinth/physiologyABSTRACT
Removal of friable asbestos-containing material can cause high levels of airborne contamination. The potential efficacy of control methods recommended by the Environmental Protection Agency (EPA) was evaluated by examination of 503 air samples obtained in 40 removal projects in a number of locations. The EPA methodology with amended water for fiber emission control was utilized on all of the observed removal projects. The projects were also considered to be well controlled and the study cannot be considered representative of common work practices. The EPA amended water methodology, when effectively utilized and administered, can provide a high degree of contamination control. Mean fiber levels in the work area in this study (1.1 f/cm3) were well below those of dry removal (38.9 f/cm3) and control by application by untreated water (28.6 f/cm3). Airborne contamination was higher during bagging debris (3.8 f/cm3) than during material removal from structural surfaces. The range of fiber levels during removal was 0.0 to 37.0 f/cm3 and fibers were detected from initial barrier construction through final cleaning. Contamination was also occasionally detected outside work area containment barriers. Air sampling produced 0.0 counts in areas of obvious contamination by settled dust and debris. Control methodologies, respiratory protection, and decontamination are discussed.
Subject(s)
Air Pollutants/analysis , Asbestos/analysis , Decontamination/methods , United States , United States Environmental Protection Agency , United States Occupational Safety and Health Administration , WaterABSTRACT
Asbestos contamination of relatively contained environments within structures can occur under many conditions and in association with various activities. Such contamination persists and can potentially expose all structure users. The more significant contamination levels are associated with disturbance of friable asbestos-containing materials, although bonded material is also capable of fiber dissemination under special conditions. Application of occupational government standards for limitation of exposure, both presently in force and proposed or recommended, indicates that levels found in some situations exceed those considered potentially carcinogenic.
