Abstract
Functional Neurological Symptom Disorder (FNSD) is a condition which produces symptoms that superficially resemble those associated with neurological damage or disease, but where such structural changes do not exist. FNSD is associated with high levels of disability and financial burden.
An innovative interdisciplinary rehabilitation approach for individuals with FNSD – Nocebo-Hypothesis Cognitive Behavioural Therapy (NH-CBT) — combines psychoeducation and behavioural experiments (physical movement with distraction and video feedback), with ongoing reference to an aetiological model of FNSD throughout the treatment. Unlike other existing treatments, NH-CBT can be applied to both functional motor symptoms (weakness, tremor, fixed dystonia, balance difficulties) and non-epileptic seizures (NES), two sub-types of FNSD that are typically studied separately and treated differently.
This thesis comprises two main studies, with the first preceded by a trial protocol. Study 1 is a parallel group randomized controlled trial comparing the efficacy of NH-CBT with an active control condition (supportive counselling and physical therapy) in treating a range of functional motor symptoms (e.g. weakness, tremor, balance and/or gait difficulties, tics), both after an eight week treatment period and at follow up eight weeks later. The primary outcome measured was physical functioning. Study 2 is a small consecutive case series investigating the potential effectiveness of NH-CBT in treating non-epileptic seizures (NES) over a 12 week period, with a six month follow-up period. The primary outcome measure was seizure frequency. Qualitative interviews were employed in both studies to explore participants’ experiences of treatment.
The results for Study 1 showed no difference between NH-CBT and the active control treatment on the primary outcome of physical functioning, with both groups showing medium to large improvements (effect sizes - NH-CBT: d = 1.02; active control: d = 0.77). However, the NH-CBT group showed significantly greater improvements on two observer-rated secondary measures, related to reduction of functional motor symptoms (F(2,74) = 5.44; p = .003) and mobility (F(2,74) = 5.32; p= .004). There was also a significantly greater proportion of NH-CBT participants post-treatment who stopped treatment early due to full recovery of functional motor symptoms (85% vs 47% of controls; χ2 (1,39) = 6.21, p= .013). The median treatment time to achieve these outcomes for the NH-CBT group was short (9.1 hours).
In Study 2, seven out of the ten participants became seizure free at least two weeks before their post-treatment assessment, and stayed seizure-free for at least five months. Six of those seven remained seizure free at six month follow-up. Two of the other three participants dropped out of treatment early; the other had nocturnal seizures only so could not participate in the majority of the treatment. Reduction in seizure frequency was statistically significant across the whole sample.
Overall, this thesis presents evidence to support the notion that NH-CBT is potentially effective in treating all common forms of FNSD. As NH-CBT is based on predictive coding aetiological models of FNSD, then the evidence also supports such models. The promising outcomes achieved despite minimal (and usually absent) therapeutic input regarding emotions in NH-CBT further corroborates the idea that they might be best conceptualised as predisposing factors and/or co-morbidities, and not core aetiological factors. In terms of clinical implications, NH-CBT is inexpensive to deliver and may not require extensive clinician training. It appears well suited to delivery within the context of neurorehabilitation services.
Limitations of the findings include the nature of the local population which the participants were taken from (more ethnically homogenous and with higher levels of tertiary education than national averages). More importantly, the sample sizes for the two studies were small, therefore these promising findings should be followed up in larger trials.