Murielle U. Ferraye

Pedunculopontine Nucleus Area Oscillations during Stance, Stepping and Freezing in Parkinson’s Disease

The pedunculopontine area (PPNa) including the pedunculopontine and cuneiform nuclei, belongs to the mesencephalic locomotor region. Little is known about the oscillatory mechanisms underlying the function of this region in postural and gait control. We examined the modulations of the oscillatory activity of the PPNa and cortex during stepping, a surrogate of gait, and stance in seven Parkinson’s disease patients who received bilateral PPNa implantation for disabling freezing of gait (FOG). In the days following the surgery, we recorded behavioural data together with the local field potentials of the PPNa during sitting, standing and stepping-in-place, under two dopaminergic medication conditions (OFF and ON levodopa). Our results showed that OFF levodopa, all subjects had FOG during step-in-place trials, while ON levodopa, stepping was effective (mean duration of FOG decreasing from 61.7±36.1% to 7.3±10.1% of trial duration). ON levodopa, there was an increase in PPNa alpha (5–12 Hz) oscillatory activity and a decrease in beta (13–35 Hz) and gamma (65–90 Hz) bands activity. PPNa activity was not modulated during quiet standing and sitting. Our results confirm the role of the PPNa in the regulation of gait and suggest that, in Parkinson disease, gait difficulties could be related to an imbalance between low and higher frequencies.

Using motor imagery to study the neural substrates of dynamic balance.

This study examines the cerebral structures involved in dynamic balance using a motor imagery (MI) protocol. We recorded cerebral activity with functional magnetic resonance imaging while subjects imagined swaying on a balance board along the sagittal plane to point a laser at target pairs of different sizes (small, large). We used a matched visual imagery (VI) control task and recorded imagery durations during scanning. MI and VI durations were differentially influenced by the sway accuracy requirement, indicating that MI of balance is sensitive to the increased motor control necessary to point at a smaller target. Compared to VI, MI of dynamic balance recruited additional cortical and subcortical portions of the motor system, including frontal cortex, basal ganglia, cerebellum and mesencephalic locomotor region, the latter showing increased effective connectivity with the supplementary motor area. The regions involved in MI of dynamic balance were spatially distinct but contiguous to those involved in MI of gait (Bakker et al., 2008; Snijders et al., 2011; Crémers et al., 2012), in a pattern consistent with existing somatotopic maps of the trunk (for balance) and legs (for gait). These findings validate a novel, quantitative approach for studying the neural control of balance in humans. This approach extends previous reports on MI of static stance (Jahn et al., 2004, 2008), and opens the way for studying gait and balance impairments in patients with neurodegenerative disorders.

The Practicalities of Assessing Freezing of Gait

Background: Freezing of gait (FOG) is a mysterious, complex and debilitating phenomenon in Parkinson’s disease. Adequate assessment is a pre-requisite for managing FOG, as well as for assigning participants in FOG research. The episodic nature of FOG, as well as its multiple clinical expressions make its assessment challenging. Objective: To highlight the available assessment tools and to provide practical, experience-based recommendations for reliable assessment of FOG. Methods: We reviewed FOG assessment from history taking, questionnaires, lab and home-based measurements and examined how these methods account for presence and severity of FOG, their limits and advantages. The practicalities for their use in clinical and research practice are highlighted. Results: According to the available assessment tools severity of FOG is marked by one or a combination of multiple clinical expressions including frequency, duration, triggering circumstances, response to levodopa, association with falls and fear of falling, or need for assistance to avoid falls. Conclusions: To date, a unique methodological tool that encompasses the entire complexity of FOG is lacking. Combining methods should give a better picture of FOG severity, in accordance with the precise clinical or research context. Further development of any future assessment tool requires understanding and thorough analysis of the specific clinical expressions of FOG.

Visual cueing using laser shoes reduces freezing of gait in Parkinson's patients at home: Laser Shoes For Freezing at Home

Freezing of gait (FOG) in Parkinson’s disease (PD) is common and debilitating. Although the evidence for cueing efficacy is encouraging, it remains difficult to translate cueing strategies into an efficient visual cueing device for use in patients’ home environments, allowing them to benefit from a safer gait in everyday life and prevent falls and related injuries. Laser shoes might offer such a home-based cueing device, and a recent laboratory study showed reduced FOG severity. Here we assess the effectiveness of laser shoes at home in a pilot study. A total of 21 PD patients with severe FOG completed 3 consecutive conditions: week 1 = wearing laser shoes, but without cueing (“without cueing”); week 2 = wearing laser shoes, with cueing (“with cueing”); week 3 = without laser shoes (“follow-up”). Outcomes were assessed at the end of each week. The primary outcome was FOG severity (New FOG Questionnaire [NFOGQ]). The relation with cognitive status was explored by correlating the NFOGQ results with the Frontal Assessment Battery. Exploratory secondary outcomes included quality of life (Parkinson’s Disease Questionnaire-39), self-reported falls and near falls, number of self-reported FOG episodes, and perceived efficacy. An activity monitor objectively measured relative locomotion duration. FOG severity improved significantly (NFOGQ: 20.35 ± 5.00 without cueing vs 18.12 ± 5.44 with cueing, P = .036; Fig. 1A). There was no correlation with the Frontal Assessment Battery. Furthermore, the NFOGQ did not differ between with cueing and follow-up (P = .235), perhaps suggesting a possible carryover, although the difference between without cueing and followup was nonsignificant (P = .156). Secondary outcomes show a reduction of self-reported falls (41%), near falls (58%; Fig. 1B), and FOG episodes (31%) with cueing. The reduction in near falls continued during the follow-up week. Although the overall number of falls decreased with cueing, the number of individuals who fell actually increased, from 3 at baseline to 5 with cueing, and similarly in the follow-up week. These results were paralleled by positive subjective experiences on the efficacy of laser shoes. The Parkinson’s Disease Questionnaire-39 and relative locomotion duration did not differ across conditions. The findings from this pilot study, although preliminary, suggest that laser shoes have potential as a mobile visual cueing device to reduce FOG and risk of falls in PD patients within their home situations and that improvements may last beyond their punctual use. Using laser shoes for 1 week perhaps boosted the participants’ confidence, but the carry-over might also represent a training effect. However, a significant difference between without cueing and follow-up is missing, hence we cannot make any firm statements about the possible existence of carry-over effects. The reduction in FOG severity did not lead to an increase in net locomotion time, perhaps because physical performance and physical activity represent associated but separate domains of physical function. It is also possible that longer lasting use of laser shoes is needed to change the a patient’s walking habits, and future studies should evaluate this. Finally, laser shoes induced falls in some individuals, possibly because the patients gained too much confidence or were too distracted and ended up falling. We acknowledge that placebo effects might partially explain the effects seen in the present open-label study, and further work should include passive or active control interventions. Moreover, new studies should investigate the added value of laser shoes relative to other cueing techniques. Finally, longer training periods and prolonged follow-ups are needed to better document the long-term efficacy and to further study possible learning and retention effects.