Normal pressure hydrocephalus (NPH) is a clinical condition resulting from an abnormal build up of cerebrospinal fluid (CSF) and ventricular enlargement in the brain. Patients often experience disturbances in gait, unitary incontinence and even dementia, although these symptoms often improve following shunt surgery. Shunt surgery helps drain the excess CSF with the help of a tube inserted into the ventricles. Apathy – the lack of motivation and goal-directed behaviour, is also another common symptom in NPH. Despite increasing concerns that apathy might represent a significant obstacle for clinical and cognitive rehabilitation, it has been rarely investigated in NPH patients. Furthermore, questions concerning the mechanisms of cognitive recovery following shunt surgery remain unresolved.
Led by Katie Peterson, a team from the Sahakian Group in the Department of Psychiatry have investigated the effectiveness of shunt surgery (after 3 – 9 months) for improvements in apathy by examining neuropsychological profiles as well as brain characteristics in 22 NPH patients. This longitudinal study, published in the British Journal of Neurosurgery, yielded two important findings that increase our current understanding of NPH.
Enlargement of the ventricles was positively correlated with severity of apathy levels. Since ventricular enlargement is commonly associated with reductions in volumes of subcortical brain regions, this finding suggests that deficits in apathy could be related to abnormalities in the caudate. The authors further hypothesized that subcortical atrophy could disrupt striatal dopamine pathways, which have been previously implicated in deficits of reward-processing and motivational levels, both of which are core characteristics of apathy.
Apathy is commonly associated with greater functional impairment, poorer quality of life, as well as a host of neuropsychiatric symptoms including depression and worsening cognitive function. In this study, the authors reported that alleviation of apathy following treatment with shunt surgery was linked to cognitive improvements. Taken together, these collective findings warrant the necessity to investigate and treat apathy alongside standard interventions for NPH.
We spoke the lead author, Katie Peterson, about the motivation and significance of the study: “We want to understand the significance of the symptom of apathy in patients with NPH, a symptom which, although commonly reported, is rarely assessed in clinics. Our results suggest that this symptom may be indicative of greater structural damage in the brain and is related in some way to functional outcome.”
On the basis of these findings, the authors plan to extend the study by furthering their investigation of brain structural changes resulting from NPH and their subsequent impact on clinical status, apathy and prognosis.