(Neuro)physiology, statistics Flashcards
ENG
- Nerve Conduction Studies (NCV) involve three types: motor, sensory, and mixed.
- Motor and sensory studies are most commonly ordered for clinical diagnosis.
- Motor studies stimulate at both proximal (S2) and distal (S1) sites, recording muscle depolarization.
- Distal latency measures time from stimulus to initial muscle depolarization.
- Amplitude reflects the number of intact axons participating in depolarization.
- Duration indicates the duration of the electrical impulse.
- Conduction velocity is influenced by nerve diameter, myelination, and temperature.
- Sensory studies only require stimulation at one site, assessing nerve function without muscle involvement.
- Sensory studies calculate conduction velocity to measure nerve function.
- Onset latency and amplitude are key metrics in sensory studies.
- Sensory studies are valuable in conditions like carpal tunnel syndrome.
- Temperature control is crucial for accurate NCV recordings.
Conduction velocity
Conduction velocity refers to the speed at which an electrical impulse travels along a nerve fiber. In the context of Nerve Conduction Studies (NCV), it is a measure of how quickly nerve impulses propagate along a nerve. Conduction velocity is influenced by various factors such as the diameter of the nerve, the presence of myelin sheath (which speeds up conduction), and temperature. In motor studies, conduction velocity is calculated by dividing the distance between the stimulation sites by the difference in latency between the proximal and distal sites. In sensory studies, conduction velocity is similarly calculated to assess nerve function, typically without muscle involvement. It is an important parameter in diagnosing nerve disorders and assessing nerve health.
SSEP
epilepsy symptoms by territory
epilepsy symptoms by location 2
Status epilepticus treatment algorithm
VEP
BAEP
SSEP
Somatosensory evoked potential (SSEP)- hátsó kötél pálya integritása
* Kevert idegek stimulálása- Ia izomrostok és a II típusú afferens rostok is ingerlésre kerülnek
Generátorok:
Felső végtag (N. medianus):
N9- Erb pont
N11-N13 komplexum- nyaki gerincvelő hátsó szarvi neuronjaink postsynapticus aktivitása
P14- ncl. cuneatus és a thalamus közt generálódik (felső agytörzs)
N20- első corticalis válasz, Broadman 3b area, P22- area precentralis
SSEP locations
Schematic representation of median nerve’s somatosensory evoked potentials (SSEP) responses localizations on brain MRI (a) and typical examples of their normal wave forms as well as recording electrodes montages (b). SSEP elicited by electric stimulation (15 mA) of median nerve at the wrist: N9, N13 and P14, respectively, the brachial plexus, cervical spinal cord, and cervico-medullary (subcortical) responses. N20 and P25 are responses of the primary sensory cortex. N9–N13 inter-peak latencies (IPL) represent a proximal peripheral nerve conduction time, and P14–N20 IPL the intracranial conduction time (ICCT). Recording and reference electrodes were placed at Cv7 (7th cervical vertebra)—Fz: for the N13 cervical spinal cord response and Cz-cSh (contralateral shoulder): for the subcortical far-field potential: P14. The cortical components, N20 and P25 were recorded at the contralateral C3′ or C4′ positions (2 cm behind C3 or C4) according to the international 10–20 system. Two sets of 500 sweeps were averaged
SSEP pathology
SSEP parameters
Inhaled anasthetic and SSEP
Nitrousoxide(N 2 O)reducestheamplitudeandincreasesthelatencyofcorticalcom- ponentsinadose-dependentfashion[43]. Inhalationalanesthetics,suchasIsoflurane,Halothane,andEnflurane,alldecrease theamplitudeandincreasethelatencyofthecorticalresponsesinadose-dependent fashion,especiallywhentheyareadministeredwithN 2 O[43].
IV anasthetics and SSEP
IntravenousAgents PropofoldoesnotaffectthesubcorticalN13component,butitincreasesthelatencyby approximately10%oftheearlycorticalcomponentswithoutaffectingtheiramplitude. Latercorticalcomponentsusuallydisappear[43]. Benzodiazepines(e.g.,Diazepam,Midazolam)reducetheamplitudeofcortical SEPwaves[42]. Barbiturates(e.g.,Thiopental,Methohexital)increaseSEPlatencyinadose- dependentfashion,withaslightamplitudedecrease[43]. EtomidatehasasurprisingeffectonthecorticalSEPamplitude,whichcanbe augmentedbyasmuchas200–600%[43].However,italsoincreasesSEPlatencies. KetaminealsoincreasesSEPamplitudeandlatency[43,21]. Opiates,suchasMorphine,andsyntheticnarcotics,suchasFentanyl,Alfentanil, andSufentanil,causeaslightincreaseinSEPlatencywithoutaffectingtheampli- tude[42].
EffectsofAnestheticAgentsonCorticalSEPAmplitude andLatency
TypicalSEPAmplitudeandLatencyValues ObtainedAfterMedianorPosteriorTibialNerveStimulation
iOP EEG
iOP EEG ampl hz
ExampleofintraoperativeEEGrecording.
EffectsofAnestheticAgentsonEEGAmplitudeand FrequencyatTypicalDoses
ioSEP
SEPsobtainedafterinadvertentocclusionoftheleftiliacartery.(a)Increased latencyanddecreasedamplitudeisseeninallresponsestoleft-legstimulation,while(b)the responsestorightlegstimulationremainunaffected.Lightcolortracescorrespondtothe baselinescollectedatthebeginningoftheoperation.
ioSEP 2
SEPrecordingsobtainedaftercordinjuryduetomisplacedinstrumentation; (a)baselines;(b)normalvariationsduringthecase;and(c)cortical(peakN45)andcervical response(peakN30)disappearjustafterplacementofinstrumentation,whiletheperipheral response(peakPF)remainsunchanged.
EEG electrode placement
epilepsy EEG parts
SEP elecrtodes
predictive values
NPV
PPV
sensitivity and specifity
sensitivity
specificity
