[Effect of posteroventral pallidotomy on event-related P300 in Parkinson's disease]. / Efecto de la palidotomía unilateral sobre el P300 en la enfermedad de Parkinson.

BACKGROUND: Ablative procedures are still frequent for the surgical treatment of Parkinson's disease (PD). Although the P300 component has been used to assess cognitive changes induced by levodopa and deep brain stimulation (DBS), the effects caused by unilateral pallidotomy remain unknown. MATERIAL AND METHODS: P300 amplitude and latency in 10 PD patients who underwent unilateral pallidotomy with and without levodopa treatment were compared with 10 healthy controls. Measurements in patients were performed 6 months before and after surgery while only once in controls, throughout the 6-month lapse between the comparative measurements performed in patients. RESULTS: Statistical differences in P300 amplitude and latency were found between the control and PD groups (p < 0.001). On the other hand, there were no differences between the groups with the use of the levodopa treatment or surgery. DISCUSSION: Lack of statistically significant results after six months of pallidotomy or treatment with levodopa suggests an absence of cognitive impairment. Our results obtained with P300 in which safety of surgical treatment has been assessed in PD are consistent with those of other procedures, such as DBS.

Bilateral cingulotomy and anterior capsulotomy applied to patients with aggressiveness.

OBJECTIVE: To perform a preliminary study on the effects and safety of bilateral cingulotomy and anterior capsulotomy in patients with aggressive behavior. PATIENTS AND METHODS: Twenty-three psychiatric patients showing aggressive behavior refractory to conventional treatment were initially evaluated. The subjects were clinically selected using the Overt Aggression Scale (OAS) and the Global Assessment of Functioning Scale (GAF). Each case was carefully reviewed by the Ethics Committee of Mexico's General Hospital. Once selection criteria were met, stereotactic lesions were made using radiofrequency on the anterior limb of the internal capsule and supragenual cingulum. Statistical differences were evaluated with a Wilcoxon test at 6 months and at 4 years. RESULTS: Ten patients underwent surgery. Their OAS and GAF scores decreased after the procedure at the 6-month (p < 0.05) and at the 4-year (p = 0.068) follow-up. Four patients showed mild and transitory postsurgical complications (hyperphagia and somnolence). CONCLUSIONS: Bilateral anterior capsulotomy in combination with cingulotomy may reduce aggressive behavior and improve clinical evaluations. Very strict clinical and ethical evaluations were applied prior to considering patients for this treatment.

Effects of Thalamic Reticular Nucleus Electrical Stimulation in Rats in a T-maze Perseverative Behavior Model Induced by 8-OH-DPAT.

Objective. Evaluate the possible decrease of chemically induced perseverative behavior in rats after electrical stimulation at different frequencies in the thalamic reticular nucleus. Material and Methods. A total of 28 male rats were divided in four groups: control, sham, OFF stimulation, and ON stimulation (450 µsec, 1 V, 6 and 120 Hz) that underwent the administration of saline solution and 8-OH-DPAT. The animals were evaluated in a T-maze model in which three choices or more in the same branch are considered as perseverative. Intragroup analysis was done through paired T-student and intergroup analysis through an ANOVA test. Results. The numbers of perseverations mean for the control group were 1.3 before and 1.4 post saline solution injections. Sham group mean of 1.3 pre and 3.4 post 8-OH-DPAT administration; OFF stimulation group 1.1 pre and 3.3 post 8-OH-DPAT administration; and for ON stimulation 1.1 pre and 1.9 post 8-OH-DPAT administration for stimulation at low frequency (6 Hz) and 3.4 at high frequency (120 Hz). Evident intergroup statistical differences were shown (p < 0.01). Conclusions. Electrical stimulation with the low-frequency group was the only group that after manipulation with 8-OH-DPAT showed a decrease in perseverative behavior, even close to baseline.

Effects of bilateral lesions in thalamic reticular nucleus and orbitofrontal cortex in a T-maze perseverative model produced by 8-OH-DPAT in rats.

OBJECTIVE: Stereotaxic lesions of the orbitofrontal-thalamic system, specifically the thalamic reticular nucleus (TRN), could be helpful to prevent perseverative behavior in rats produced by 8-OH-DPAT. METHODS: Fifty rats were conditioned in a T-maze to measure the number of perseverations. Habituation was performed on days 1 and 2, baseline scores were obtained on day 3 and the final test was done on day 4 (chemical induction). Group I only received saline solution injection; group II was only submitted to 8-OH-DPAT; group III received pharmacological treatment with chlorimipramine (CMI) before 8-OH-DPAT administration; group IV and group V were submitted to stereotaxic bilateral lesions, one week before T-maze evaluation, in the TRN and orbitofrontal cortex (OFC), respectively and received 8-OH-DPAT administration. RESULTS: No differences between groups were found at baseline on day 3 (p<0.05). Significant differences were found between days 3 and 4 of evaluation only in group II (p<0.01) and group V (p<0.001). Differences between groups on day 4 were significant (p<0.01). CONCLUSIONS: TRN lesions were as effective as CMI administration to prevent the 8-OH-DPAT action. OFC lesions failed to prevent the perseverative behavior.