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Human gait and balance are controlled by automatic processes in the central nervous system, and in sensory and proprioceptive systems. If a disturbance occurs in any of these complex structures, it may lead to balance and gait problems. Equally important are the systems controlling the upper extremity functions where reach, grasp and manipulation skills may be affected. For the neurodegenerative disease idiopathic normal pressure hydrocephalus (iNPH), balance and gait disturbances are cardinal symptoms. Motor control of the upper extremities is also affected. In clinic today, physical impairment of persons with iNPH is commonly visually assessed using subjective, course tests with ordinal scales with the risk of missing minor changes. There is a lack of objective and quantitative ways to measure motor control in daily patient care. The aim of this thesis was to develop and validate tools for objective assessment of parameters that affect motor control in persons with iNPH.

Postural stability in stance and walking was assessed using gyroscopes in patients with iNPH, healthy elderly (HE) and patients with ventriculomegaly (VM). Compared to HE, patients with iNPH had reduced postural stability and relied less on vision. iNPH patients also had a lower trunk sway velocity than VM during walking. The gyroscopic system could quantitatively assess postural deficits in iNPH, making it a potentially useful tool for diagnosis and for clinical follow-up. The differences found during gait also suggests that walking, rather than quiet stance, should be further investigated for facilitating differential diagnosis compared to other patient groups with ventriculomegaly.

The gait in patients with iNPH is according to guidelines defined as slow, shuffling with a low foot-lift, and wide based. To objectively quantify the latter two features, a system (Striton) was developed in-house to assess the increased distance between the feet and the peak heel-height at the push-off phase of the gait cycle. It was validated in experimental setups, compared to gold standard motion capture systems (MCS), on healthy elderly (HE), through test-retest and day-to-day evaluations, and in four patients with iNPH. Striton demonstrated high correlations, in step-width and in heel-height, compared with the MCS. The mean step-width in the HE was 5.2 ± 0.9 cm (mean±Standard Deviation) and the heel-height 16.7±0.6 cm. Test-retest and day-to-day variations were small, ±0.5 cm in step-width and ±1.2 cm in heel-height, and differences in the parameters were seen between HE and iNPH both before and after surgery. Thus, Striton has the potential of quantitatively assessing gait parameters in HE and iNPH in a valuable manner.