An intra-operative feature-based classification of microelectrode recordings to support the subthalamic nucleus functional identification during deep brain stimulation surgery.

Objective. The subthalamic nucleus (STN) is the most selected target for the placement of the Deep Brain Stimulation (DBS) electrode to treat Parkinson's disease. Its identification is a delicate and challenging task which is based on the interpretation of the STN functional activity acquired through microelectrode recordings (MERs). Aim of this work is to explore the potentiality of a set of 25 features to build a classification model for the discrimination of MER signals belonging to the STN.Approach.We explored the use of different sets of spike-dependent and spike-independent features in combination with an ensemble trees classification algorithm on a dataset composed of 13 patients receiving bilateral DBS. We compared results from six subsets of features and two dataset conditions (with and without standardization) using performance metrics on a leave-one-patient-out validation schema.Main results.We obtained statistically better results (i.e. higher accuracyp-value = 0.003) on the RAW dataset than on the standardized one, where the selection of seven features using a minimum redundancy maximum relevance algorithm provided a mean accuracy of 94.1%, comparable with the use of the full set of features. In the same conditions, the spike-dependent features provided the lowest accuracy (86.8%), while a power density-based index was shown to be a good indicator of STN activity (92.3%).Significance.Results suggest that a small and simple set of features can be used for an efficient classification of MERs to implement an intraoperative support for clinical decision during DBS surgery.

Characterization of Microelectrode Recordings for the Subthalamic Nucleus identification in Parkinson's disease.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for Parkinson's disease, when the pharmacological approach has no more effect. DBS efficacy strongly depends on the accurate localization of the STN and the adequate positioning of the stimulation electrode during DBS stereotactic surgery. During this procedure, the analysis of microelectrode recordings (MER) is fundamental to assess the correct localization. Therefore, in this work, we explore different signal feature types for the characterization of the MER signals associated to STN from NON-STN structures. We extracted a set of spike-dependent (action potential domain) and spike-independent features in the time and frequency domain to evaluate their usefulness in distinguishing the STN from other structures. We discuss the results from a physiological and methodological point of view, showing the superiority of features having a direct electrophysiological interpretation.Clinical Relevance- The identification of a simple, clinically interpretable, and powerful set of features for the STN localization would support the clinical positioning of the DBS electrode, improving the treatment outcome.

Allodynia in different forms of migraine.

About 60% of patients complain of cutaneous allodynia during migraine episodes, often in the periorbitary region of the pain side. Pre-clinical studies have shown that the underlying mechanism is sensitisation of primary nociceptors and central trigeminovascular neurons and that patients have a lower pain threshold for mechanical stimulation compared to controls. The objective of this study was to determine the prevalence of allodynia during headache attacks in different forms of migraine. The subjects were 221 outpatients consecutively evaluated in the Headache Center of the L. Sacco Hospital in Milan: 114 had only attacks of migraine without aura (MO), 63 had also attacks with aura (MA) and 44 patients with chronic migraine with and without drug overuse (CM). Presence of head allodynia was investigated by a semistructured interview. Statistical analysis was performed by chi square test with Bonferroni correction for multiple comparisons. Forty-seven out of 114 MO patients (41.2%) complained of allodynia during headache episodes, 41 out of 63 MA patients (65.0%), and 29 out of 44 CM patients (65.9%). A higher frequency of allodynia in MA and CM with respect to MO patients was observed (p<0.01 at chi square test). Allodynia was a common complaint in migraineurs, being present in more than 40% patients of each group. A higher frequency was observed in MA and in CM patients. This observation may suggest that both frequency of attacks and presence of aura episodes may contribute to induce changes in neuronal activation threshold thought to sustain allodynia.

Frontotemporal dementia.

Frontotemporal dementia is a clinicopathological syndrome caused by progressive degeneration of the frontal lobes, anterior temporal lobes or both. A wide spectrum of cognitive, psychological and behavioural symptoms has been reported, with early disturbance of personality and social conduct, impairment of executive functions and language, while memory and visuo-spatial skills are usually preserved. Published criteria can lead to a good accuracy in the antemortem diagnosis of frontotemporal dementia with a sensitivity of 85% and a specificity of 99%. Treatment rests on the management of behavioural disturbances.