Assessing discharge periodicity in mountain catchments using classified environmental conditions(Tatra Mountains, Poland)

The periodicity of a river expressed in cycles of various lengths(monthly, seasonal,multiannual) is a result of climatic factors and overlapping environmental conditions within its catchment. In uncontrolled or poorly surveyed catchments, it is very difficult to determine the duration of a stream’s hydrological activity. This is especially relevant for catchments with complicated water circulation in karstic rocks. The present study concerns the small catchment of the Str??yski Potok river located in the area of the Tatra National Park, in the Western Tatras. The observation period covered the 2015 hydrological year, which differed hydrologically from average conditions. This study aims to develop a simple method to explain the processes shaping the mountain stream discharge periodicity. The research employed periodic field observations linked with climatic and non-climatic factors. Environmental conditions were assessed as four classes reflecting their influence on appearance or disappearance of mountain stream water. Class boundaries were the values of quartiles. The degree of correspondence between environmental factors and stream field observations was described via the Index DC(Degree Correspondence Index) approach.Complete correspondence(Index DC =0) was found in 23% catchments, a weak relationship between conditions favouring discharge and actual condition(Index DC=-1, +1) was noted within 11 catchments,while in 9 catchments, no such relationship was found(Index DC =-2, +2). The obtained results indicate a correspondence or lack thereof between the environmental potential of the catchment and its discharge periodicity. The discrepancies between the assessment of the influence of climatic and nonclimatic factors and the data collected during field observations provide a basis for more detailed studies.Continuation of these studies based on the proposed classifications will allow for a more complete explanation of water disappearance in river channels and the determination of their short-and long-term discharge periodicity.

Ictal-interictal continuum:a review of recent advancements

Continuous electroencephalogram(cEEG)has become an indispensable technique in the management of critically ill patients for early detection and treatment of non-convulsive seizures(NCS)and non-convulsive status epilepticus(NCSE).It has also brought about a renaissance in a wide range of rhythmic and periodic patterns with heterogeneous frequency and morphology.These patterns share the rhythmic and sharp appearances of electrographic seizures,but often lack the necessary frequency,spatiotemporal evolution and clinical accompaniments to meet the definitive criteria for ictal patterns.They may be associated with cerebral metabolic crisis and neuronal injury,therefore not clearly interictal either,but lie along an intervening spectrum referred to as ictal-interictal continuum(IIC).Generally speaking,rhythmic and periodic patterns are categorized as interictal patterns when occurring at a rate of<1Hz,and are categorized as NCS and NCSE when occurring at a rate of>2.5 Hz with spatiotemporal evolution.As such,IIC commonly includes the rhythmic and periodic patterns occurring at a rate of 1–2.5 Hz without spatiotemporal evolution and clinical correlates.Currently there are no evidence-based guidelines on when and if to treat patients with IIC patterns,and particularly how aggressively to treat,presenting a challenging electrophysiological and clinical conundrum.In practice,a diagnostic trial with preferably a non-sedative anti-seizure medication(ASM)can be considered with the end point being both clinical and electrographic improvement.When available and necessary,correlation of IIC with biomarkers of neuronal injury,such as neuronal specific enolase(NSE),neuroimaging,depth electrode recording,cerebral microdialysis and oxygen measurement,can be assessed for the consideration of ASM treatment.Here we review the recent advancements in their clinical significance,risk stratification and treatment algorithm.

Continuous video electroencephalogram for herpes simplex encephalitis:a case report and literature review

Background:Electroencephalogram(EEG)is an important tool for the diagnosis of herpes simplex virus encephalitis(HSE).However,the diagnosis of non-convulsive status epilepticus(NCSE)in HSE is challenging without the help of continuous video EEG(CVEEG),and whether EEG is a predictor of outcome remains controversial.Case presentation:A 63-year-old woman presented with a 5 day history of fever,coma and seizures.Results of EEG,magnetic resonance imaging and polymerase chain reaction(PCR)in cerebrospinal fluid(CSF)were suggestive of herpes simplex encephalitis-1(HSE-1).Preliminary EEG showed periodic discharges at the prefrontal and temporal lobes,which were particularly synchronized with intermittent lip smacking movements,and the discharges were terminated by diazepam.After 2-week treatment with acyclovir,high-dose hormone pulse therapy and high-dose immunoglobulin therapy,the CSF was improved,but the patient’s consciousness became worsen,consistent with the diffuse slow waves in the delta range and low voltage of EEG activity.In the following 1 month,the patient had non-responsiveness to pain and sound as shown by CVEEG with diffuse slow waves.Sometimes paroxysmal very slow waves(0.5–1 Hz)were synchronized with intermittent paroxysmal eye movements,pupil abnormality,and sweating in the frontal area.After 2 months of treatment,the EEG abnormalities improved to have alpha rhythm.Conclusion:The CVEEG not only helps identify NCSE but can also be used to monitor HSE progression.