Cortical plasticity after hand prostheses use: Is the hypothesis of deafferented cortex "invasion" always true?

OBJECTIVE: To study motor cortex plasticity after a period of training with a new prototype of bidirectional hand prosthesis in three left trans-radial amputees, correlating these changes with the modification of Phantom Limb Pain (PLP) in the same period. METHODS: Each subject underwent a brain motor mapping with Transcranial Magnetic Stimulation (TMS) and PLP evaluation with questionnaires during a six-month training with a prototype of bidirectional hand prosthesis. RESULTS: The baseline motor maps showed in all three amputees a smaller area of muscles representation of the amputated side compared to the intact limb. After training, there was a partial reversal of the baseline asymmetry. The two subjects affected by PLP experienced a statistically significant reduction of pain. CONCLUSIONS: Two apparently opposite findings, the invasion of the "deafferented" cortex by neighbouring areas and the "persistence" of neural structures after amputation, could vary according to different target used for measurement. Our results do not support a correlation between PLP and motor cortical changes. SIGNIFICANCE: The selection of the target and of the task is essential for studies investigating motor brain plasticity. This study boosts against a direct and unique role of motor cortical changes on PLP genesis.

Characterization of multi-channel intraneural stimulation in transradial amputees.

Although peripheral nerve stimulation using intraneural electrodes has been shown to be an effective and reliable solution to restore sensory feedback after hand loss, there have been no reports on the characterization of multi-channel stimulation. A deeper understanding of how the simultaneous stimulation of multiple electrode channels affects the evoked sensations should help in improving the definition of encoding strategies for bidirectional prostheses. We characterized the sensations evoked by simultaneous stimulation of median and ulnar nerves (multi-channel configuration) in four transradial amputees who had been implanted with four TIMEs (Transverse Intrafascicular Multichannel Electrodes). The results were compared with the characterization of single-channel stimulation. The sensations were characterized in terms of location, extent, type, and intensity. Combining two or more single-channel configurations caused a linear combination of the sensation locations and types perceived with such single-channel stimulations. Interestingly, this was also true when two active sites from the same nerve were stimulated. When stimulating in multi-channel configuration, the charge needed from each electrode channel to evoke a sensation was significantly lower than the one needed in single-channel configuration (sensory facilitation). This result was also supported by electroencephalography (EEG) recordings during nerve stimulation. Somatosensory potentials evoked by multi-channel stimulation confirmed that sensations in the amputated hand were perceived by the subjects and that a perceptual sensory facilitation occurred. Our results should help the future development of more efficient bidirectional prostheses by providing guidelines for the development of more complex stimulation approaches to effectively restore multiple sensations at the same time.

Comparison of linear frequency and amplitude modulation for intraneural sensory feedback in bidirectional hand prostheses.

Recent studies have shown that direct nerve stimulation can be used to provide sensory feedback to hand amputees. The intensity of the elicited sensations can be modulated using the amplitude or frequency of the injected stimuli. However, a comprehensive comparison of the effects of these two encoding strategies on the amputees' ability to control a prosthesis has not been performed. In this paper, we assessed the performance of two trans-radial amputees controlling a myoelectric hand prosthesis while receiving grip force sensory feedback encoded using either linear modulation of amplitude (LAM) or linear modulation of frequency (LFM) of direct nerve stimulation (namely, bidirectional prostheses). Both subjects achieved similar and significantly above-chance performance when they were asked to exploit LAM or LFM in different tasks. The feedbacks allowed them to discriminate, during manipulation through the robotic hand, objects of different compliances and shapes or different placements on the prosthesis. Similar high performances were obtained when they were asked to apply different levels of force in a random order on a dynamometer using LAM or LFM. In contrast, only the LAM strategy allowed the subjects to continuously modulate the grip pressure on the dynamometer. Furthermore, when long-lasting trains of stimulation were delivered, LFM strategy generated a very fast adaptation phenomenon in the subjects, which caused them to stop perceiving the restored sensations. Both encoding approaches were perceived as very different from the touch feelings of the healthy limb (natural). These results suggest that the choice of specific sensory feedback encodings can have an effect on user performance while grasping. In addition, our results invite the development of new approaches to provide more natural sensory feelings to the users, which could be addressed by a more biomimetic strategy in the future.

The effects of a multimodal training program on burnout syndrome in gynecologic oncology nurses and on the multidisciplinary psychosocial care of gynecologic cancer patients: an Italian experience.

OBJECTIVE: In cancer care, the burden of psycho-emotional elements involved on the patient-healthcare provider relationship cannot be ignored. The aim of this work is to have an impact on the level of burnout experienced by European Institute of Oncology (IEO) gynecologic oncology nurses (N = 14) and on quality of multidisciplinary team work. METHOD: We designed a 12 session multimodal training program consisting of a 1.5 hour theoretical lesson on a specific issue related to gynecologic cancer patient care, 20 minute projection of a short film, and 1.75 hours of role-playing exercises and experiential exchanges. The Link Burnout Questionnaire (Santinello, 2007) was administered before and after the completion of the intervention. We also monitored the number of patients referred to the Psycho-oncology Service as an indicator of the efficacy of the multidisciplinary approach. RESULTS: After the completion of the program, the general level of burnout significantly diminished (p = 0.02); in particular, a significant decrease was observed in the "personal inefficacy" subscale (p = 0.01). The number of patients referred to the Psycho-oncology Service increased by 50%. SIGNIFICANCE OF RESULTS: Nurses are in the first line of those seeing patients through the entire course of the disease. For this reason, they are at a particularly high risk of developing work-related distress. Structured training programs can be a valid answer to work-related distress, and feeling part of a multidisciplinary team helps in providing patients with better psychosocial care.

Blindness in dogs with pituitary dependent hyperadrenocorticism: relationship with glucose, cortisol and triglyceride concentration and with ophthalmic blood flow.

Pituitary dependent hyperadrenocorticism (PDH) shows a high morbidity and blindness is one of its complications. Compression of the optic chiasm (OC) by the hypophysis adenoma is one of the causes. Another cause could be due to vascular and metabolic alterations of the PDH. Out of a total of 70 dogs with confirmed diagnosis of PDH, 12/70 showed blindness. In only 2/12 the OC was compromised. Electroretinography in dogs without the OC being compromised showed altered A and B wave patterns. Ophthalmological Doppler showed an alteration of the blood flow only in blind dogs without OC compression. Cortisol concentrations (Co), triglycerides (Tg) and glycaemia (G) were greater in 10 dogs with non-compressive blindness vs. dogs with conserved vision. Loss of vision correlated with the increase in these variables. Blindness in dogs with PDH would be related to changes in retinal blood flow, associated to higher Co, Tg and G concentrations.