Impact of Stimulation Frequency on Verbal Fluency Following Bilateral Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease.

OBJECTIVE: The effects of stimulation frequency on verbal fluency (VF) following subthalamic nucleus deep brain stimulation (STN-DBS) in Parkinson's disease (PD) are not well understood. The present study examines the impact stimulation frequency has on VF following bilateral STN-DBS in PD. METHODS: Prospective study of 38 consecutive patients with PD with low frequency STN-DBS (LFS) (n = 10) and high frequency STN-DBS (HFS) (n = 14), and a non-operated PD control group consisting of patients with fluctuating response to dopaminergic medication (n = 14) homogeneous in age, education, disease duration, and global cognitive function. Patients were evaluated on VF tasks (letter, semantic, action verbs, alternating). A one-way analysis of variance (ANOVA) was conducted to assess distinctions between groups. Pre- and post-surgical comparisons of fluencies were performed for operated groups. A mixed ANOVA was applied to the data to evaluate the interaction between treatment (HFS vs. LFS) and time (pre- vs. post-surgery). Strategy use (clustering and switching) was evaluated. RESULTS: Semantic and letter fluency performance revealed significant differences between HFS and LFS groups. Pre- and post-surgical comparisons revealed HFS negatively affected letter, semantic, and action fluencies, but LFS had no effect on VF. No interaction effect or main effect of treatment was found. Main effect of time was significant for semantic and action fluencies indicating a decrease in postoperative fluency performance. Patients with LFS produced larger average cluster sizes than patients with HFS. CONCLUSION: LFS may be less detrimental to VF, but these findings suggest that VF decline following STN-DBS is not caused by stimulation frequency alone.

Quantitative evaluation of oculomotor disturbances in progressive supranuclear palsy.

OBJECTIVES: To explore and quantify systematically the ocular abnormal movements present in progressive supranuclear palsy (PSP) from the early stages, to assess the ability of this standardized examination in the differential diagnosis of PSP from Parkinson's disease (PD), and to compare in more detail oculomotor disturbances between PSP variants. METHODS: Sixty-five consecutive PSP patients with <5 years of disease duration diagnosed according to MDS-PSP criteria, 25 PD patients and 25 controls comparable in age, education and disease duration were explored using a bedside battery of tests for the quantitative evaluation of oculomotor dysfunction in clinical practice. Other accepted scales were used for measurement of motor (PSPRS), cognitive (FAB) and behavioral (FBI) impairment. RESULTS: Measurement of oculomotor dysfunction significantly differentiated PSP from PD and controls (p < 0.001) and showed high accuracy in the differential diagnosis of early-to-mid stage PSP from PD. PSP-Parkinsonism and PSP-Progressive Gait Freezing phenotypes showed more preserved ocular motor function compared to PSP-Richardson Syndrome, although no differences were found between PSP subtypes in the number of square wave jerks, optokinetic nystagmus defects, degree of apraxia of eyelid opening, or presence of the "Round the Houses" sign. CONCLUSIONS: Using a bedside clinical instrument for quantifying oculomotor disturbances in PSP shows promising potential at differentiating PSP from PD, and it seems able to provide a qualitative and quantitative description of ocular motor function in parkinsonian disorders.

Cognitive and behavioral profile of progressive supranuclear palsy and its phenotypes.

BACKGROUND: Although several progressive supranuclear palsy (PSP) phenotypes have recently been described, studies identifying cognitive and neuropsychiatric differences between them are lacking. METHODS: An extensive battery of cognitive and behavioural assessments was administered to 63 PSP patients, 25 PD patients with similar sociodemographic characteristics, and 25 healthy controls. We analysed differences in phenomenology, frequency and severity of cognitive and neuropsychiatric symptoms between PSP, PD and HC, and between PSP subtypes. RESULTS: Regarding phenotypes, 64.6% met criteria for Richardson's syndrome (PSP-RS), 10.7% PSP with predominant Parkinsonism (PSP-P), 10.7% with PSP progressive gait freezing (PSP-PGF), and 10.7% PSP with predominant speech/language disorder (PSP-SL). Impairment was more severe in the PSP group than in the PD and HC groups regarding motor scores, cognitive testing and neuropsychiatric scales. Cognitive testing did not clearly differentiate between PSP phenotypes, but PSP-RS and PSP-SL appeared to have more cognitive impairment than PSP-PGF and PSP-P, mainly due to an increased impairment in frontal executive domains. Regarding neuropsychiatric disturbances, no specific behavior was more common in any of the PSP subtypes. CONCLUSION: Motor deficits delineate the phenotypes included in currently accepted MDS-PSP criteria. Cognition and behavioural disturbances are common in PSP and allow us to distinguish this disorder from other neurological diseases, but they do not differentiate between PSP phenotypes.