Ivo Říha

Peripheral neuroactive steroids may be as good as the steroids in the cerebrospinal fluid for the diagnostics of CNS disturbances

To compare the predictivity of the neuroactive steroids in the cerebrospinal fluid and peripheral blood for the diagnostics of CNS disturbances, eighteen unconjugated steroids were quantified in the cerebrospinal fluid (CSF) from the 3rd ventricle and 18 unconjugated steroids and 7 steroid polar conjugates were measured in the serum using GC-MS and RIA. Eight postmenopausal women (56-78 years of age) and 7 men (22-88 years of age) with hydrocephalus were enrolled in the study. The sensitivity of the method ranged from low femtogram to low picogram levels depending on the steroid fragmentation pattern. Using multivariate regression, a model for simultaneous prediction of the CSF steroids from the serum steroids was completed. Then, the penetrability of the individual steroids across the blood-brain-barrier was evaluated and the sources of various brain steroids were estimated. Our data show that a part of the steroids may be synthesized de novo in the CNS. However, substantial part of the steroid metabolites may be synthesized in the CNS from the steroid precursors or directly transported from the periphery. The CNS in situ synthesis and transport from periphery might be complementary in some cases, i.e. brain synthesis might provide minimum level of steroids, which are indispensable for the CNS functions.

Minimally invasive treatment of posterior fossa craniopharyngioma by means of navigated endoscopy.

The aim of the paper is to present an unusual case of ectopic posterior fossa craniopharyngioma after repeated surgeries for primary suprasellar tumor. The clinical condition of the patient favored minimally invasive neuroendoscopic surgery. After presurgical planning with the help of neuronavigation system a trajectory from the contralateral side through the cisterna magna was chosen. Endoscopic cyst fenestration and cyst wall resection were safely performed with an excellent outcome. The possible origin of this posterior fossa craniopharyngioma is discussed together with tumor dissemination pathways. The endoscopic contralateral approach to the tumor utilized the wide working space provided by the cisterna magna and the great versatility of the navigated neuroendoscopic approach was proven.

The Role of Anterior Nuclei of the Thalamus: A Subcortical Gate in Memory Processing: An Intracerebral Recording Study.

Objective To study the involvement of the anterior nuclei of the thalamus (ANT) as compared to the involvement of the hippocampus in the processes of encoding and recognition during visual and verbal memory tasks. Methods We studied intracerebral recordings in patients with pharmacoresistent epilepsy who underwent deep brain stimulation (DBS) of the ANT with depth electrodes implanted bilaterally in the ANT and compared the results with epilepsy surgery candidates with depth electrodes implanted bilaterally in the hippocampus. We recorded the event-related potentials (ERPs) elicited by the visual and verbal memory encoding and recognition tasks. Results P300-like potentials were recorded in the hippocampus by visual and verbal memory encoding and recognition tasks and in the ANT by the visual encoding and visual and verbal recognition tasks. No significant ERPs were recorded during the verbal encoding task in the ANT. In the visual and verbal recognition tasks, the P300-like potentials in the ANT preceded the P300-like potentials in the hippocampus. Conclusions The ANT is a structure in the memory pathway that processes memory information before the hippocampus. We suggest that the ANT has a specific role in memory processes, especially memory recognition, and that memory disturbance should be considered in patients with ANT-DBS and in patients with ANT lesions. ANT is well positioned to serve as a subcortical gate for memory processing in cortical structures.

The role of brain shift, patient age, and Parkinson's disease duration in the difference between anatomical and electrophysiological targets for subthalamic stimulation

Abstract Introduction. Although microrecording is common in subthalamic stimulation, microelectrode monitoring prolongs surgical time and may increase the risk of haemorrhagic complications. The main reason for electrophysiological mapping is the discrepancy between the calculated anatomical and final electrophysiological targets. The aim of this paper is to describe the relationship between anatomical and electrophysiological targets defined as the best electrophysiological recordings from multiple parallel electrode tracts, explaining the target discrepancy with attention paid to the role of brain shift and patient- and disease-related factors. Materials and methods. Subthalamic electrodes were stereotactically implanted in 58 patients using microrecording by means of parallel electrodes at defined distances. The relationship between the final electrode placement to its anatomical trajectory and the relationship between the definitive electrodes implanted on the right and left sides were analysed, as was the influence of patient age, Parkinsons disease duration, and late motor complications duration. Results. Final electrode placement matched the anatomical trajectory in 53.4% of patients on the right side and 43.1% of patients on the left side. Electrode positions were symmetrical in 38.3% of patients. The analysis of left and right electrode positions does not prove a statistically significant prevalence of lateral and posterior final electrode trajectories as could be expected from lateral and posterior movements of the brain caused by brain shift, although there was some tendency for a larger percentage of lateral electrodes on the left side. Age, Parkinsons disease duration, and L-DOPA effect duration were not confirmed as responsible factors. Conclusions. The difference between anatomical trajectory and final electrode placement supports the use of functional microelectrode monitoring in subthalamic deep brain stimulation. Brain shift is not the only causative factor of the difference. The possible roles of age, Parkinsons disease duration, and late motor complications duration were also not confirmed by study results.

ID 88 – Anterior thalamus in cognition: An intracerebral recording study

Objective To study the involvement of the anterior thalamic nuclei (ANT) in the cognitive processes. Methods We recorded the event-related potentials (ERPs) by visual and auditory memory encoding-recognition tasks by intracerebral recordings in patients with pharmacoresistent epilepsy who underwent the deep brain stimulation (DBS) surgery of the anterior thalamic nuclei with depth electrodes implanted bilaterally in the ANT. We compared the results with epilepsy-surgery candidates with depth electrodes implanted bilaterally in the hippocampus. Results In the ANT we recorded ERPs during the visual encoding and visual and auditory recognition tasks. No significant ERPs were recorded during the encoding phase by auditory stimuli in ANT. In hippocampus ERPs were recorded by visual and auditory memory encoding and recognition tasks. In the recognition tasks (visual and auditory) the ERPs in ANT preceded the ERPs in hippocampus. Conclusions ERPs are elicited by visual memory encoding and recognition, as well as by auditory recognition memory processes, but not by encoding auditory memory processing in the ANT. The ANT precedes the hippocampus in the memory recognition pathway. Key message ANT has a specific role in the memory processes, especially the memory recognition.