Gait Characteristics, Physical Activity and Subjective Outcome after Shunt Surgery in Normal Pressure Hydrocephalus

Abstract: Background  Idiopathic normal pressure hydrocephalus (iNPH) is a common but under-diagnosed disease among the elderly. The condition is characterised by gait disturbance, postural instability, cognitive decline and incontinence, caused by accumulated cerebrospinal fluid within the central nerve system. The treatment is a shunt insertion to divert excess fluid. Few studies have described the detailed gait in INPH, there is a lack of research about physical activity, and patient-reported outcomes after shunt surgery are sparsely described.  The overall aim of this thesis was to increase the knowledge of the gait pattern, the level of physical activity, and to evaluate the effect of a physical exercise programme in iNPH. Another aim was to evaluate the patient’s self-experienced outcome after surgery.  Methods and results, study I In total 127 patients were randomised to either a supervised 12-week high-intensity exercise programme or to standard care after shunt surgery. Evaluation was performed with the iNPH scale and goal attainment after the intervention and after six months. There was low compliance to the exercise programme and no differences between the groups could be detected according to the iNPH scale at any of the follow-ups. Patients with high attendance rate achieved their set goals to a higher extent than the control group at the post intervention follow-up. Methods and results, study II In total 109 patients from the population in study I, were evaluated with an actigraphy recording of physical activity variables for seven days before and three- and six months after shunt surgery. In addition, physical performance was evaluated with the 10-meter walk test, the 6-minute walk test and 30 s chair stand test. The patients walked faster with improved results on the walking tests postoperatively. Improvement in the 30 s chair stand test was interpreted as improved postural control. The physical activity intensity was not affected by surgery. The patients had very low energy expenditure and were to a large extent sedentary, before and after shunt surgery. The exercise intervention had no effect on physical activity or the physical performance tests.   Methods and results, study III In total 47 patients were included to a gait analysis with an inertial sensor system. Additionally, the patients were assessed with the Timed Up and Go test and the iNPH scale, pre- and three months postoperatively and in relation with 42 older healthy individuals. The patients walked with shorter strides, decreased velocity, increased time in stance and with decreased joint angles, especially in the ankle joint. The gait pattern im-proved after shunt surgery, but outcome on all variables were still worse compared to the healthy individuals, except for step hight that was normalised. Shunt surgery had no effect on stride length variability.   Methods and results, study IV  In total 58 patients rated their experienced changes three months after shunt surgery. The subjective outcome was analysed in relation to objective clinical outcomes (the iNPH scale) and questionnaires regarding, sense of coherence, quality of life, anxiety and depression. Clinical outcome and the questionnaires were evaluated before and three months after shunt surgery and in relation to 42 older healthy individuals. The patients reported most frequently some degree of positive changes after surgery. The subjective outcomes in overall experience, gait and continence correlated moderately with the corresponding objective outcomes, but there were not correlations within the cognition and balance areas. Depression and quality of life improved after surgery, but the result was still lower than for healthy individuals. There was no correlation between the patients´ sense of coherence and the subjective outcome.  Conclusion   Shunt surgery contributes to improved walking patterns, improved physical functions, reduced signs of depression and increased quality of life, but patients with iNPH are still more affected than healthy elderly. The patients report most frequently positive changes, but not total recovery after shunt surgery. Despite improvements within several areas the physical activity level is very low, both before and after the shunt operation. A postoperative high-intensity physical training program had no additional effect, which is explained by the fact that few patients completed the program. Patients with iNPH probably need guidance to additional improvement and to increase physical activity through meaningful activities after shunt surgery. Further research is needed to evaluate interventions that address the specific iNPH impairments.