Valentina Chiesa

Movement-related modulation of neural activity in human basal ganglia and its L-DOPA dependency: recordings from deep brain stimulation electrodes in patients with Parkinson's disease.

Abstract. Through electrodes implanted for deep brain stimulation in three patients (5 sides) with Parkinsons disease, we recorded the electrical activity from the human basal ganglia before, during and after voluntary contralateral finger movements, before and after L-DOPA. We analysed the movement-related spectral changes in the electroencephalographic signal from the subthalamic nucleus (STN) and from the internal globus pallidus (GPi). Before, during and after voluntary movements, signals arising from the human basal ganglia contained two main frequencies: a high β (around 26 Hz), and a low β (around 18 Hz). The high β (around 26 Hz) power decreased in the STN and GPi, whereas the low β (around 18 Hz) power decrease was consistently found only in the GPi. Both frequencies changed their power with a specific temporal modulation related to the different movement phases. L-DOPA specifically and selectively influenced the spectral power changes in these two signal bands.

Anatomo-clinical correlation of intraoperative stimulation-induced side-effects during HF-DBS of the subthalamic nucleus

Abstract. The efficacy of deep brain stimulation of the subthalamic nucleus (STN) is dependent on the accuracy of targeting. In order to reduce the number of passes and, consequently, the duration of surgery and risk of bleeding, we have set up a new method based on direct magnetic resonance imaging (MRI) localisation of the STN. This procedure allows a short duration of the neurophysiological session (one or two initial tracks). Whenever a supplementary track is needed, the stimulation-induced side effects are analysed to choose from one of the remaining holes in Bens gun. A good knowledge of anatomical structures surrounding the STN is mandatory to relate side effects to the actual position of the track. In our series of 11 patients (22 sides, 37 tracks), the most common and reproducible side effects were those characterised by motor, sensorial, oculomotor and vegetative signs and symptoms. Moreover, the therapeutic window (distance between the current intensity needed to obtain the best clinical effect and the intensity capable to induce side effects) predicted clinical efficacy in the long-term, and contributed to the choice of which among the examined tracks had to be implanted with the chronic macroelectrode.

Apraxia is not associated to a disproportionate naming impairment for manipulable objects

The relevance of gesture knowledge for the semantic representation of manipulable objects was investigated in a series of 15 patients with a focal left-hemisphere lesion. The patients were classified according to the presence/absence of ideomotor and ideational apraxia. We investigated picture naming and word-picture matching (pointing to a picture on verbal command) with stimuli including items from three categories: manipulable objects, non-manipulable objects, and animals. The analysis was performed at group level and at single-patient level. Nine patients were affected by ideational apraxia and nine by ideomotor apraxia: two cases presented ideomotor but not ideational apraxia, and two cases presented the opposite dissociation. Patients affected by ideational apraxia were more severely impaired in all tasks, but did not show a disproportionate impairment with the category of manipulable objects in contrast to the other categories. The presence of ideomotor apraxia did not cause a greater impairment in any task or category. Finally, we observed a patient with ideational apraxia who performed flawlessly in naming and word-picture matching for all the stimuli, including manipulable objects. In conclusion, we did not find a relationship between ideational apraxia and a disproportionate impairment of the semantic knowledge of manipulable objects.

Visualisation of the subthalamic nucleus: a multiple sequential image fusion (MuSIF) technique for direct stereotaxic localisation and postoperative control

Abstract. A novel multiple, sequential image fusion (MuSIF) procedure merging stereotaxic CT with frameless magnetic resonance imaging (MRI) is used since June 2000 to visualise and directly localise the subthalamic nucleus (STN) on T2 images. In 13 consecutive Parkinsons cases, intraoperative recording and stimulation verified bilateral electrode implantation guided by fused T2 images. In 85% of sides, final implantation opted for visualised target track. Implanted electrode position on postoperative T2 images matched planned target. Clinical follow-up reproduces literatures best results. This MuSIF technique, effective for direct STN targeting, has practical advantages: MRI can be performed regardless of surgery time; regular MR scanning to correct real image distortion is unneeded; and the need for multiple localising tracks is reduced by enabling us to account for each patients STN anatomy.

Epilepsy in TSC: Certain etiology does not mean certain prognosis

Prevalence and long‐term outcome of epilepsy in tuberous sclerosis complex (TSC) is reported to be variable, and the reasons for this variability are still controversial.

Patients with epilepsy and patients with psychogenic non-epileptic seizures: Video-EEG, clinical and neuropsychological evaluation

PURPOSE The incidence of psychogenic non-epileptic seizures (PNES) is 4.9/100,000/year and it is estimated that about 20-30% of patients referred to tertiary care epilepsy centers for refractory seizures have both epilepsy and PNES. The purpose of our study is to evaluate psychiatric disorders and neuropsychological functions among patients with PNES, patients with epilepsy associated with PNES and patients with epilepsy. METHODS We evaluated 66 consecutive in-patients with video-EEG recordings: 21 patients with epilepsy, 22 patients with PNES and 10 patients with epilepsy associated with PNES; 13 patients were excluded (8 because of mental retardation and 5 because they did not present seizures or PNES during the recording period). RESULTS All patients with PNES had a psychiatric diagnosis (100%) vs. 52% of patients with epilepsy. Cluster B personality disorders were more common in patients with PNES. We observed fewer mood and anxiety disorders in patients with PNES compared with those with epilepsy. We did not find statistically significant differences in neuropsychological profiles among the 3 patient groups. CONCLUSION This study can help to contribute to a better understanding of the impact of PNES manifestations, in addition to the occurrence of seizures, in order to provide patients with more appropriate clinical, psychological and social care.

The subthalamic nucleus in Parkinson's disease: Power spectral density analysis of neural intraoperative signals

Abstract.To test a new tool for the neurophysiological identification of the human subthalamic nucleus (STN) during stereotactic surgery for the implantation of deep-brain-stimulation (DBS) electrodes, we analysed off-line the intraoperative signals recorded from patients with Parkinson’s disease. We estimated the power spectral density (PSD) along each penetration track (8 patients, 13 sides) and determined the spatial correlation of the PSD with the target location estimated from neuroimaging procedures (“anatomical target”), and with the final target location derived from standard intraoperative neurophysiological procedures for STN localization (“clinical target”). At each step we recorded the ‘on-line’ signal for 120 seconds; because the PSD was estimated by calculating the periodogram for 6-second epochs of neural signal, we had 20 epochs at each step. When the electrode track crossed the STN, the PSD in the 0.25-2.5 kHz band increased, peaking on average <0.5 mm cranial to the clinical target and 1.00±1.51 mm caudal to the anatomical target. When the track was outside the nucleus, the PSD remained unchanged. Even on recordings with low signal-tonoise ratio, off-line PSD analysis of neural signals showed a good correspondence with the target indicated by the surgical team. On-line intraoperative estimation of the PSD may be a simple, reliable, rapid and complementary approach to electrophysiological monitoring during STN surgery for Parkinson’s disease.

Subthalamic somatosensory evoked potentials in Parkinson's disease.

Deep brain stimulation (DBS) of subthalamic nucleus (STN) is an effective treatment for advanced Parkinsons disease. It also provides an opportunity to record neural activity from the human basal ganglia. In this study, to investigate the involvement of the human STN in sensory functions, we recorded somatosensory evoked potentials (SEPs) elicited by contralateral median‐nerve stimulation, from STN electrodes implanted for DBS in patients with Parkinsons disease. We suggest that the STN N18 component of SEPs in Parkinsons disease is a mainly local field potential elicited by muscle afferent input to the nucleus.

Age-related gender differences in reporting ictal fear: analysis of case histories and review of the literature.

To determine if there are age or gender‐related differences in reporting fear as a symptom of epileptic seizure, all clinical charts of patients evaluated at the “C. Munari – Epilepsy Surgery Center” of Milan from 1990 to June 2005 were analyzed, looking for patients with ictal fear. Among the 2,530 clinical charts examined (1,330 male and 1,200 female), 265 patients were found with ictal fear (100 men, 165 women). The gender difference in reporting ictal fear was not so marked in the pediatric age group (98 girls, 74 boys), whereas in adult patients the difference was significant (158 women, 83 men). Interestingly, more men than women (14:3) had ictal fear during childhood that disappeared during adulthood. The literature review confirmed that ictal fear is significantly more common in women, though there is no gender difference in the pediatric age group.

Focal epilepsies in adult patients attending two epilepsy centers: classification of drug-resistance, assessment of risk factors, and usefulness of "new" antiepileptic drugs

Purpose:  To classify the grade of antiepileptic drug (AED) resistance in a cohort of patients with focal epilepsies, to recognize the risk factors for AED resistance, and to estimate the helpfulness of “new‐generation” AEDs.