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Analysis of postural sway in patients with normal pressure hydrocephalus: effects of shunt implantation

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Poor postural balance is one of the major risk factors for falling in normal pressure hydrocephalus (NPH). Postural instability in the clinic is commonly assessed based upon force platform posturography. In this study we focused on the identification of changes in sway characteristics while standing quiet in patients with NPH before and after shunt implantation. Postural sway area and sway radius were analyzed in a group of 9 patients and 46 controls of both genders. Subject's spontaneous sway was recorded while standing quiet on a force platform for 30-60 s, with eyes open and then closed. Both analyzed sway descriptors identified between-group differences and also an effect of shunt implantation in the NPH group. Sway radius and sway area in patients exhibited very high values compared with those in the control group. Importantly, the effect of eyesight in patients was not observed before shunt implantation and reappeared after the surgical treatment. The study documents that static force platform posturography may be a reliable measure of postural control improvement due to shunt surgery.

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Published 01 January 2009
Reads 132
Language English
December 7, 2009
Eur J Med Res (2009) 14(Suppl. IV): 53-58
EUROPEAN JOURNAL OF MEDICAL RESEARCH
53
© I. Holzapfel Publishers 2009
ANALYSIS OFPOSTURALSWAY INPATIENTS WITHNORMALPRESSURE HYDROCEPHALUS: EFFECTS OFSHUNTIMPLANTATION
1 2,3 41 54 L. Czerwosz , E. Szczepek, J. W. Blaszczyk , B. Sokolowska , K. Dmitruk , K. Dudzinski , 2, 32, 3 J. Jurkiewicz, Z. Czernicki
1 2 Department ofRespiratory Research andDepartment ofNeurosurgery, Medical Research Center, Polish Academy ofSciences, Warsaw, 3 Poland; Departmentof Neurosurgery,Second Faculty ofMedicine, Warsaw Medical University, Warsaw, Poland; 4 5 Faculty for Rehabilitation, Warsaw Academy ofPhysical Education, Warsaw, Poland;Department ofPhysiology, Collegium Medicum, Nicolaus Copernicus University, Torun, Poland
Abstract Poor postural balance is one ofthe major risk factors for falling in normal pressure hydrocephalus (NPH). Postural instability in the clinic is commonly assessed based upon force platform posturography. In this study we focused on the identification ofchanges in sway characteristics while standing quiet in patients with NPH before and after shunt implantation. Pos-tural sway area and sway radius were analyzed in a group of9 patients and 46 controls ofboth genders. Subject’s spontaneous sway was recorded while stand-ing quiet on a force platform for 30-60 s, with eyes open and then closed. Both analyzed sway descriptors identified between-group differences and also an ef-fect ofshunt implantation in the NPH group. Sway radius and sway area in patients exhibited very high values compared with those in the control group. Im-portantly, the effect ofeyesight in patients was not ob-served before shunt implantation and reappeared after the surgical treatment. The study documents that stat-ic force platform posturography may be a reliable measure ofpostural control improvement due to shunt surgery. Key words:posture, sway, normal pressure hydro-cephalus INTRODUCTION Postural stability is a fundamental part ofthe entire motor activity [1]. Decline in the postural stability may result from impairment ofthe central or peripheral postural control efficiency as well as abnormalities in function ofmotor executive systems. Postural stability control involves the generation of appropriate stabilizing responses. This is done either by triggering and scaling preprogramed reactions or by continuous updating the center ofgravity (COG) po-sition in a feedback mode. The COG deviates from equilibrium and usually enlarges velocity, which is be-ing detected and signaled by sensation receptors and muscle tension receptors, receptors ofangle and linear accelerations – by a peripheral part ofthe system of balance and by the vision system that provides data re-lated to the body shifts when the field ofvision
changes. The restoration process starts when the de-flection ofthe equilibrium state exceeds some thresh-old level which can be different for everyone. The main factor which influences the threshold level is the actual state ofthe postural system. This state perma-nently changes in years but it can also change within days and even hours and minutes in among others due to fatigue. During quiet stance stabilizing torques generated at different levels ofthe body’s kinematic chain are transmitted mainly down to the base ofsupport. They are observed as a compound center offoot pressure (COP) signal. These stabilizing processes shape COP characteristics [2]. Since COP is a measure ofwhole-body dynamics, it represents the summed up effect of a number ofdifferent neuromuscular components. These components are acting at different joints [3, 4] and their characteristics are strongly dependent on the main inputs that control postural stability. These in-puts include visual, proprioceptive and vestibular sys-tems. The effectors are muscles ofthe torso and limbs [5]. Locomotion control system consists oflocomo-tion centres in the cortex, brain stem, and spinal cord (medulla). These regions obtain information (signals) from other areas ofthe brain, namely from the cere-bellum and basal ganglia. Impairments ofa central processing ofinput signals, e.g., due to ageing or re-sulting from pathology, also affect the COP character-istics. Normal pressure hydrocephalus (NPH) is a patho-logical process caused by excessive accumulation of cerebrospinal fluid in the intracranial space related to unbalanced production and absorption ofthe fluid. The syndrome ofnormal pressure hydrocephalus is usually characterized by a triad ofsymptoms: com-plaints ofgait disturbance, mild dementia and im-paired bladder control [6]. Gait and balance distur-bances are often the most pronounced symptom and the first to become apparent. The disturbances range in severity from mild imbalance to the inability to stand or walk at all. Gait is often wide-based, short-stepped, slow and shuffling, and with the whole body leaning posture. Patients with NPH may have trouble picking up their feet, making stairs and curbs difficult, which frequently results in falls. Normal pressure hy-