Biomedical subjects
Publications and source records attributed to T Pozzo.
Equilibrium is based on gaze stabilization. Clinical examinations currently test, individually the three components involved in equilibrium: vestibular, visual and proprioception. New investigations are being developed to test equilibrium dynamic conditions. After briefly reviewing vestibular physiology, under the authors discuss the various tests of vestibular function and equilibrium.
This experiment, which extends a previous investigation (Pozzo et al. 1990), was undertaken to examine how head position is controlled during natural locomotor tasks in both normal subjects (N) and patients with bilateral vestibular deficits (V). 10 normals and 7 patients were asked to perform 4 locomotor tasks: free walking (W), walking in place (WIP), running in place (R) and hopping (H). Head and body movements were recorded with a video system which allowed a computed 3 dimensional reconstruction of selected points in the sagittal plane. In order to determine the respective contribution of visual and vestibular cues in the control of head angular position, the 2 groups of subjects were tested in the light and in darkness. In darkness, the amplitude and velocity of head rotation decreased for N subjects; these parameters increased for V subjects, especially during R and H. In darkness, compared to the light condition, the mean position of a line placed on the Frankfort plane (about 20-30 degrees below the horizontal semi-circular canal plane) was tilted downward in all conditions of movement, except during H, for N subjects. In contrast, this flexion of the head was not systematic in V subjects: the Frankfort plane could be located above or below earth horizontal. In V subjects, head rotation was not found to be compensatory for head translation and the power spectrum analysis shows that head angular displacements in the sagittal plane contain mainly low frequencies (about 0.3-0.8 Hz). The respective contribution of visual and vestibular cues in the control of the orientation and the stabilization of the head in space is discussed.
Head kinematics was studied in 10 normal subjects (NS) and 7 patients (P) with bilateral vestibular deficit while they executed various locomotor tasks. The movement of the body was recorded with a video system which allowed a computer reconstruction of the motion of joint articulations and other selected points on the body in three dimensions. Analyses focus on head translation along the vertical axis and rotation in the sagittal plane. Two conditions were studied: free walking (W) and hopping (H). The subjects were tested in light and in darkness. In NS, while walking in darkness, mean head position was tilted downward. In contrast, this flexion was not systematic in P. Darkness did not significantly influence the amplitude and velocity of head angular displacement during W, but, during H the amplitude decreased by 37% for NS. During H in darkness, head stabilization decreased for P. These results suggest that head kinematics, during natural locomotor tasks, could be used to evaluate vestibular deficiencies.
Head kinematics were studied in ten normal subjects while they executed various locomotor tasks. The movement of the body was recorded with a video system which allowed a computer reconstruction of motion of joint articulations and other selected points on the body in three dimensions. Analyses focus on head translation along the vertical axis and rotation in the sagittal plane. This was done by recording the displacement of a line approximating the plane of horizontal semi-circular canals (the Frankfort plane: F-P). Four conditions were studied: free walking (W) walking in place (WIP) running in place (R) and hopping (H). In the 4 experimental conditions, amplitude and velocity of head translation along the vertical axis ranged from 1 cm to 25 cm and 0.15 m/s to 1.8 m/s. In spite of the disparities in the tasks regarding the magnitude of dynamic components, we found a significant stabilization of the F-P around the earth horizontal. Maximum amplitude of F-P rotation did not exceed 20 degrees in the 4 situations. Vertical angular velocities increased from locomotion tasks to the dynamic equilibrium task although the maximum values remained less than 140 degrees/s. Predominant frequencies of translations and rotations in all the tasks were within the range 0.4-3.5 Hz and harmonics were present up to 6-8 Hz. During walking in darkness, mean head position is tilted downward, with the F-P always below the earth horizontal. Darkness did not significantly influence the amplitude and velocity of head angular displacement during W, WIP and R, but during H the amplitude decreased by 37%. Residual head angular displacement is found to compensate for head translation during the 4 conditions. Our study emphasizes the importance of head stabilization as part of the postural control system and described as a basis for inertial guidance.
Head kinematic during various motor tasks was studied in ten subjects. The movement of the body was recorded with a video system (E.L.I.T.E.) which allows a computer reconstruction of three-dimensional motion of selected points on the body. Analysis is focused on head rotation in the horizontal and vertical planes. The results demonstrate that the amplitude and the maximum velocity do not exceed respectively 38 deg/s and 185 deg/s. However the head is intermittently stabilized and the angle of this stabilization is dependent upon the task and related to the direction of gaze. Darkness had no significant effect on head rotational velocity during walking but caused a decrease in velocity during running and hopping. The results suggest that head stabilization (1) is related to an ocular fixation point in the direction of gaze in space and (2) is probably regulated on the basis of a predictive mode of sensory motor control.
The present study attempts to clarify the relationship between eye and body positioning during an upside-down standing posture on the hands. In this posture the head was observed to be stable and the eyes were anchored to an earth-fixed target. We measured the variations of body sway when subjects displaced their gaze upward or downward from their anchoring position. They did this voluntarily under instruction, and involuntarily by means of base-down or base-up wedge prisms. Results show that the anchoring point chosen by the subjects corresponds to a perceived limit of their body sway. They suggest that vision is also used to convey the desired optimal zone for the center of gravity in cases where fine balance is required.
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In recent years the immunologic aspects of the normal and pathological ear have been studied by several authors, with particular attention given to the histopathologic aspects of the epidermis of the tympanic membranes of the outer ear canal and of the middle ear mucosa in normal physiologic as well as in inflammatory conditions. Such studies may help in giving a more precise definition to the pathogenesis and clinical behavior of middle ear cholesteatoma. In this paper we report the results of an immunohistopathologic study carried out using the immunohistochemical technique of monoclonal antibodies on cholesteatoma matrix samples taken during radical mastoidectomy or tympanoplasty. In particular, the presence of T-lymphocytes and Langerhans cells was evaluated using selective monoclonal antibodies and a relationship between the data collected and the clinical expression of the disease in each case was sought. In this study it was not possible to establish a close relationship between clinical behavior and immunohistopathological findings, which appeared rather similar in all the cases. The presence of Langerhans' cells may confirm the hypothesized role they play in phlogistic reactions and bone reabsorption due to the presence of the cholesteatoma in the middle ear. Yet, in order to evaluate their true role correctly, more detailed studies should be carried out on the spatial distribution of T-lymphocytes and Langerhans' cells in the cholesteatoma matrix as well as on their ultrastructural characteristics.
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