(Neuro)physiology, statistics

Question 1

ENG

Answer 1

• 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.

Question 2

Conduction velocity

Answer 2

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.

Question 3

SSEP

Answer 3

Question 4

epilepsy symptoms by territory

Answer 4

Question 5

epilepsy symptoms by location 2

Answer 5

Question 6

Status epilepticus treatment algorithm

Answer 6

Question 7

VEP

Answer 7

Question 8

BAEP

Answer 8

Question 9

SSEP

Answer 9

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

Question 10

SSEP locations

Answer 10

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

Question 11

SSEP pathology

Answer 11

Question 12

SSEP parameters

Answer 12

ENG in carpal tunnel syndrome: sensory latency > 3.7 ms is the most sensitive test

Question 13

Inhaled anasthetic and SSEP

Answer 13

Nitrousoxide(N 2 O)reducestheamplitudeandincreasesthelatencyofcorticalcom- ponentsinadose-dependentfashion[43]. Inhalationalanesthetics,suchasIsoflurane,Halothane,andEnflurane,alldecrease theamplitudeandincreasethelatencyofthecorticalresponsesinadose-dependent fashion,especiallywhentheyareadministeredwithN 2 O[43].

Question 14

IV anasthetics and SSEP

Answer 14

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].

Question 15

EffectsofAnestheticAgentsonCorticalSEPAmplitude andLatency

Answer 15

Question 16

TypicalSEPAmplitudeandLatencyValues ObtainedAfterMedianorPosteriorTibialNerveStimulation

Answer 16

Question 17

MEP vs SSEP

Answer 17

SomatosensoryEPmonitoringmeasurestheintegrityofsensorytractsonly.There- fore,selectivedamagetomotortractsmaygoundetected.Additionally,sincethe ventralanddorsalportionsofthespinearesuppliedbydifferentbloodvessels,is- chemiaaffectingthemotortractsonlywillnotbedetectedbySEPs.Thus,MEPsare usedintraoperativelytoprotectthestructuralandfunctionalintegrityofthemotor tractsinthespinalcord.

Question 18

tMEP intraoperative

Answer 18

Dependingonthesurgicalprocedure,stimulationcanbemonopolarorbipolar. Monopolarstimulationisdeliveredwithahand-heldsingle-tipstimulator,whichis usedasthecathode(negativestimulatingelectrode).Theanode(positiveelectrode) consistsofasterilesubdermalneedleplacedintoamuscleinsidetheincision.Bipo- larstimulationisdeliveredwithadoubletipelectrode,withthenegativetipplaced towardstherecordingsite. Constant-currentstimuli,eachhavingadurationof0.01msec,aredeliveredata lowrateof1or2Hztoavoidmusclefatigue.Stimulusintensityfordirectnerveor nerverootstimulationisgraduallyincreasedfrom0mAuntilanEMGresponseis seen,uptoamaximumofabout2mA[48].Forpedicleorpediclescrewstimulation, stimulusintensityisgraduallyincreaseduntilaresponseisseen,from0mAuptoa maximumofapproximately40mA[7,54].Thisprocedureisusedtominimizethe amountofcurrentdeliveredtoneuralstructures.

Question 19

iOP EEG

Answer 19

Question 20

iOP EEG ampl hz

Answer 20

Question 21

ExampleofintraoperativeEEGrecording.

Answer 21

Question 22

EffectsofAnestheticAgentsonEEGAmplitudeand FrequencyatTypicalDoses

Answer 22

Question 23

ioSEP

Answer 23

SEPsobtainedafterinadvertentocclusionoftheleftiliacartery.(a)Increased latencyanddecreasedamplitudeisseeninallresponsestoleft-legstimulation,while(b)the responsestorightlegstimulationremainunaffected.Lightcolortracescorrespondtothe baselinescollectedatthebeginningoftheoperation.

Question 24

ioSEP 2

Answer 24

SEPrecordingsobtainedaftercordinjuryduetomisplacedinstrumentation; (a)baselines;(b)normalvariationsduringthecase;and(c)cortical(peakN45)andcervical response(peakN30)disappearjustafterplacementofinstrumentation,whiletheperipheral response(peakPF)remainsunchanged.

Question 25

EEG electrode placement

Answer 25

Question 26

epilepsy EEG parts

Answer 26

Question 27

SEP elecrtodes

Answer 27

Question 28

predictive values

Answer 28

Question 29

NPV

Answer 29

Question 30

PPV

Answer 30

Question 31

sensitivity and specifity

Answer 31

Question 32

sensitivity

Answer 32

Question 33

specificity

Answer 33

Question 34

three components of the ICP waveform

Answer 34

P1 = Percussion wave 🥁
Generated by arterial pulsations at the beginning of systole.
P2 = Tidal wave 🌊
Reflects the compliance of the ventricles, responding to increased pressure of the percussion wave.
Usually P2 is ~80% as tall as P1.(28169966) If P2 > P1 this suggests poor compliance, due to concerningly elevated ICP.
P3 = Dicrotic wave 📉
Reflects aortic valve closure at the end of systole.

Normally, P1 > P2 > P3, in a descending pattern.
As ICP elevates, the brain compliance is compromised. This causes P2 to increase higher than P1. Eventually, P1 and P2 may fuse into a single wave (figure above).
Abnormal waveforms may occur before the absolute value of the ICP is elevated. This may be an early signal of an impending ICP crisis.(34618757)
Dampened waveforms may also be seen in patients with catheter occlusion, catheter malposition, air bubbles, cerebral vasospasm, or in patients with an open skull (e.g., status post craniectomy).

Question 35

high ICP waveform

Answer 35

Question 36

(?) normal lundberg waves

Answer 36

B waves:
Waves last between ~30 seconds to several minutes.
Amplitude is ~20-30 mm Hg.
Significance is unclear; often suggest impaired intracranial compliance.
C waves:
Waves last ~7-15 seconds.
Amplitude is usually <20 mm Hg.
C-waves are a component of normal physiology, due to cardiac and respiratory cycles.

Question 37

plateau wave - Lundberg A

Answer 37

Plateau waves result from a vicious cycle as shown above, which causes transient elevations in ICP.
The physiological prerequisites for plateau waves include the following:
(1) Tenuous brain perfusion.
(2) The brain is on the steep, right portion of the cerebral compliance curve (see figure below). The brain has expanded to the point where there is really no extra room to accommodate further edema. Thus, the mere dilation of cerebral vasculature is sufficient to increase the ICP.
(3) Preserved cerebral autoregulation.
Plateau waves themselves are self-limiting. Short plateau waves (e.g., ~5-15 min) pose no immediate threat, but longer pressure waves might cause neurologic insult. Regardless, the presence of pressure waves reflects a dangerous situation, where the brain has reached the limits of physiological compensation.
Plateau waves (a.k.a. pathological A waves) are transient, periodic severe elevations in ICP (up to 50-100 mm) usually lasting for ~5-30 minutes (but potentially up to two hours).(19565359) They may occur spontaneously, or may be precipitated by coughing, pain, or changes in position from lying to sitting or from sitting to standing.(26704760)
Plateau waves are often accompanied by clinical deterioration, with symptoms as listed below.(29329250) Arterial blood pressure remains roughly stable during a plateau wave, although dysautonomia can occur.

Question 38

High ICP treatment by Tier steps

Answer 38

Question 39

reasons to stop using mannitol

Answer 39

🛑 Mannitol is potentially nephrotoxic.
🛑 Mannitol often induces diuresis, which may lead to volume depletion and brain hypoperfusion. Diuresis may also promote electrolytic disarray (with hypokalemia, hypomagnesemia, and hypophosphatemia).(32440802) This risk can be mitigated by replacing the diuresed volume 1:1 with an isotonic solution (e.g., plasmalyte) for 6 hours after mannitol infusion.
🛑 Guidelines recommend monitoring the efficacy and safety of mannitol by following the serum osmolality to ensure that mannitol isn’t accumulating and thereby increasing the risk of kidney injury (e.g., an osmolality >320 mOsm and/or osmolal gap >55 mOsm suggests mannitol accumulation).(32227294) In reality, this is rarely performed properly.(32440802)
🛑 There may be a rebound elevation in ICP, due to mannitol which crosses the blood-brain barrier and eventually causes edema within damaged areas of the brain.
🛑 Meta-analysis of available studies shows that mannitol is less effective than hypertonic saline, while being associated with higher rates of kidney injury.(21242790) A Cochrane analysis found that mannitol might have detrimental effects on mortality, when compared to hypertonic saline.(32440802)
🛑 Guidelines recommend the use of hypertonic saline rather than mannitol for traumatic brain injury or intracranial hemorrhage.(32227294)

Question 40

moderately deep sedation with propofol

Answer 40

Propofol reduces brain metabolic activity, which may improve ICP and also avoid cellular hypoxemia.
For patients with ICP elevation, propofol sedation may be a sensible choice. Additionally, it may be reasonable to target a slightly deeper level of sedation than might otherwise be chosen.
Propofol has the advantage that it is easily titrated, thereby allowing for neurologic examinations to be performed intermittently. Propofol also has antiepileptic properties that will protect against seizure.

Question 41

barbiturate coma

Answer 41

The concept of a barbiturate coma is the same as that of propofol use above, with the difference that barbiturates can achieve a deeper coma. Barbiturates are ideally titrated using an EEG, to achieve a burst-suppression pattern (once a burst-suppression pattern is reached, barbiturate dose should not be increased further).(31659383)
**Pentobarbital is preferred over phenobarbital, because the half-life of pentobarbital is somewhat shorter. Nonetheless, pentobarbital still has a long half-life (15-50 hours). **Thiopental might be an attractive option here, but it’s unavailable in the United States, due to its history of being used for lethal injection.
A deep barbiturate coma has substantial side effects. Hypotension requiring vasopressor support may occur, as well as ileus. Barbiturates are **metabolized slowly, which may make it impossible to evaluate the patient’s neurological outcome for weeks. **This may lead to some very challenging situations. For example, it’s ethically impermissible to withdraw life-sustaining therapy in a patient who has been rendered comatose with pentobarbital.
⚠️ Due to inability to titrate or rapidly reverse this therapy, barbiturate coma is an intervention of last resort.

Question 42

p value

Answer 42

Question 43

Odds ratio

Answer 43

Question 44

odds ratio 2

Answer 44

Question 45

evidence level

Answer 45

Question 46

ICH scoring

Answer 46

Question 47

ASIA scoring

Answer 47

Question 48

Glasgow Outcome scale

csökken rossz

Answer 48

Question 49

mRS

növekszik rossz

Answer 49

Question 50

Koos classification

Answer 50

Question 51

Koos therapeutical cons

Answer 51

Question 52

Cholinerg

Answer 52