Role of Intraoperative Neurophysiologic Monitoring in the Resection of Thalamic Astrocytomas.

BACKGROUND: The thalamus is a deep-seated and crucial structure for the sensorimotor system. It has been long considered a surgically inaccessible area because of the morbidity associated with surgical resections. Astrocytomas of the thalamus are usually treated with bioptic procedures followed by adjuvant treatments. Intraoperative neurophysiologic monitoring (IONM) allows safe and satisfactory resections of lobar gliomas, but few data are available for thalamic lesions. The aim of this study was to review the outcome of a small series of patients with thalamic astrocytomas that were treated with surgical resection with the aid of IONM. METHODS: Surgical resection with IONM was performed in 5 patients with thalamic astrocytomas (1 grade I, 1 grade II, 2 grade III, 1 grade IV). Two astrocytomas were in the dominant hemisphere. Preoperative and postoperative neuropsychological assessments were performed in 3 patients. IONM was tailored to the individual patient and consisted of transcranial motor evoked potential monitoring, cortical motor evoked potential monitoring, somatosensory evoked potential monitoring, direct electrical stimulation, electroencephalography, and electrocorticography. RESULTS: None of the patients experienced permanent motor deficits; 2 patients had a transient hemiparesis requiring rehabilitation; 1 patient had a transient aphasia, and 1 patient had permanent aphasia. None of the patients had intraoperative seizures, but 1 patient experienced postoperative transient status epilepticus. The extent of resection on postoperative volumetric magnetic resonance imaging was >70% in all cases. CONCLUSIONS: Surgical resection of thalamic astrocytomas appeared to be effective and relatively safe when guided by IONM. Larger series of patients are required to confirm these preliminary data.

Dysfunctional brain circuitry in obsessive-compulsive disorder: source and coherence analysis of EEG rhythms.

BACKGROUND: Morphological and functional studies suggested involvement of several cortical and subcortical circuitries in patients with obsessive-compulsive disorder (OCD). The aim of the present study was to investigate networks involved in OCD pathophysiology, using power (coupling of EEG bands, low-resolution electromagnetic tomography-LORETA) and coherence analysis in drug-naïve patients. METHOD: EEG was obtained from 37 drug-naïve patients with OCD and 37 age- and sex-matched controls. Resting EEG was recorded from 29 scalp channels. Coupling (ratio and correlation) between low and high frequencies was analyzed on Fz. For each frequency band, LORETA current density distribution, intra-hemispheric and inter-hemispheric coherence analysis were computed. RESULTS: OCD had increased current density for delta in the insula and for beta in frontal, parietal and limbic lobes. OCD also had decreased inter-hemispheric coherence and reduced coupling between delta and beta frequencies. CONCLUSIONS: In OCD, increased frontal beta is consistent with previous evidence of frontal dysfunction. Hyperactivity of insular delta sources, together with rhythms decoupling and reduced interhemispheric alpha coherence are consistent with additional involvement of cortico-subcortical functional connections. Combined use of power and coherence analysis may provide functional measures on different levels of involvement of cortico-subcortical circuits in neuropsychiatric disorders.