716
KORESPONDENCE425200011157117176233283337399461523578639697752
/1202200011132
CORRESPONDENCE1260200011155117176237294344398460522585639701758813
Letter4253200973878106135175202
to6443200972670
the7313200972771112
Editor:8603200974085104131175202220
Transient10973200974062102146178197238283310
BIS14243200974363103
elevations15443200974060101140179206225270315347
during19083200974589116136180226
caloric2151320097367595140167186223
testing2391320097266698126145190236
in26443200971863
brain27243200974673112131176
death:29173200974586125152197213
artifactual3147320097396595114138178214243288327346
or35103200974471
physiological?35983200974691128161180224244289335354391430450481
29615920001114291140
|343200011126
ANESTEZIOLOGIE4268040010753112155200245290342362425467527586607650
A10988040010753
INTENZIVNÍ1172804001071978123168227276296345405426
MEDICÍNA16198040010770114174195248268328382
/20468040010732
Anest21238040010753101145179208
intenziv235080400107196794137185222241282
Med.26528040010770114164180
2025;36(4):296-2972852804001074487128172185229273296338359374418461506536574617659
/35568040010732
www.aimjournal.cz48358040010765133201214257275349367415463490539579598614654693
https://doi.org/10.36290/aim.2025.04942543009543679513916918321423665843009846921147724300951457811251549254300984383102148191234277321347386408476496542585627671689733778821
Letter4259100305135257355453575690
to1165910030595226
the1441910030595241358
Editor:18509100305142283363458589704773
Transient267491003051492683925406477258439851080
BIS38059100305140222355
elevations421091003051161903074305536487278539961103
during42511700305136275393474622745
caloric122011700305112236317442557638752
testing20221170030595217324423502649772
in28451170030574222
brain311711700305135250374456603
death:377111700305136253376470616684
artifactual4251430030512024034442351964175485599611201201
or167714300305124239
physiological?196714300305136278397504582708782907102811101223134814281544
Ceylan4251820014971133194227290360
Delice8091820014984147181213267330
M.1,116318200149101134128918300873913261820014931
Kavrut13811820014974137199244313357
Ozturk17631820014986142187257303367
N.2215418200149831152271183008739
1Department4252040071304532040012167118175223256292375425481513
of988204001215584
Anesthesiology10932040012161116167206240295346385408463487542599647
and17612040012148103160
Reanimation,19422040012154105153208231314362395418473529549
Van25122040012156102157
Training2690204001215077125149204227282338
and30492040012149104160
Research32312040012153104143194242274319374
Hospital,36262040012165121160216240273322345366
Van,40132040012156102157178
Turkey4212204001214998131178227273
2Department4252170071304562170012167118175223256292375425481513
of991217001215584
Anesthesiology10962170012161116167206240295346385408463487542599647
and17642170012148104160
Reanimation,19452170012154105153208231314362395418473529549
Antalya25162170012161116148197221268317
Training2854217001215076125148203226281338
and32132170012148103160
Research33942170012154104144194242275319374
Hospital,37892170012166121160217240273322346366
Antalya,41762170012162117149198222269318339
Turkey4536217001214998131178227273
Dear4252580010758103143169
Editor,614258001074290109137184211222
We4252720010773115
present556272001074976118151195243269
an841272001074189
unusual946272001074795142174221261280
bispectral1242272001074968100149193234264290331350
index1608272001071966115159198
(BIS)182227200107246988128151
monitoring19892720010773121169188215261288307354403
phenomenon2408272001075098142189237310354402450498
observed425286001074897131175201244287337
during778286001074996122141189238
standard1032286001073463104151200241267315
brain1363286001075076118136184
death1563286001074993132159207
testing,1787286001072769103132150198247262
which20662860010764113131171219
may23012860010774114152
carry2470286001074081107134177
clinical266328600107405977125143183224243
implications425300001071992142161180220261289307355404437
for88230000107237198
BIS1000300001074564105
interpretation112530000107186693136162212239282310352379397445494
in1639300001071967
neurocritical1725300001074893140167214255282301329348388429448
care2193300001074082108151
practice.2364300001074976118159189208248290305
During5653140010758106132150198246
a8273140010741
routine884314001072673120148166214257
evaluation1157314001074484125143190230257275322370
of1543314001074872
brain1631314001074975116135182
death,1829314001074892131158206221
722066314001074486
hours2168314001074896144169203
after238731400107416495137163
traumatic256631400107275495142214254281300339
brain425328001074976117136183
injury,62432800107196785132158201212
in852328001071966
a9353280010740
40-year-old992328001074388118158201240266291340360409
male,14173280010773114132176190
we16233280010765108
observed1747328001074898131175201244287337
a21003280010741
physiologically2157328001074998136170188235255302352370410451470488528
unexpected2701328001074895139179425342001075095136166209259
BIS705342001074665106
response.832342001072770103153202251284328343
At1196342001075379
our1297342001074896122
center,1441342001074082131157200226238
the1701342001072876120
BIS™1843342001074564105159
VISTA2023342001074666107150197
Monitor22413420010771119168186214261288
(Covidien,2550342001072474121161180229248292340356
Mansfield,4253560010770111159192217237281300349365
MA,8153560010770124141
USA)982356001075696148172
is1180356001071851
routinely1257356001072774122150169217261280320
used1603356001074881125175
for180435600107247198
neurological1928356001074893140167214233282332350391432451
monitoring24053560010774122171189217264291310358407
in2838356001071967
patients425370001074989116134176223249283
with723370001076483110157
severe895370001073376116158183225
brain1135370001074975116134180
injury.133137000107186583129154196207
Typically,1554370001074175124142181222240258296307
transient187737000107275393140172190232279305
low2197370001071966129
BIS2342370001074563103
values246037000107408099145188220
(0–10)2696370001072364111149187209
are425384001074167109
attributed55038400107416898124143192240268310359
to926384001072773
signal1016384001073351100147187206
noise1238384001074896115147191
or1445384001074874
electrode1536384001074362105146176202249299342
artifacts189438400107416798116140181222251286
and2196384001074188137
are2349384001074167110
occasionally2475384001074788126167200218266314354373391431
encountered,425398001074492132179227275302345371414464480
even924398001074485128176
in1120398001071866
patients1206398001075091118137181229256291
with1517398001076584112160
clinically169739800107405977125144184225244263303
confirmed2020398001074086135158178205279323373
brain2413398001075077118137185
death.2617398001074993134161209225
In565412001071967
this65141200107287694127
case,797412001074082115159174
corneal989412001074087114163207247266
reflexes,127441200107276993116160199242276292
deep1585412001074993137187
tracheal179141200107285496137185229269288
suctioning,2098412001073380121151170218267285333382398
and2515412001074189138
oculocephalic2672412001074889137156204425426001074083132181222241259299
maneuvers7444260010774114162207254295339365399
produced1163426001075077124174221262304354
no1537426001074897
observable1653426001074898132176202246288337357401
changes2074426001074088129177226270304
in2397426001071967
BIS.2484426001074564105121
Bilateral262542600107456483123151193220261280
caloric425440001074184104153181201243
testing695440001072973108138157207258
was9804400010766109144
then1151440001072978124174
performed1352440001075197125153202230306352403
using1783440001074883102151202
202012440001074590
mL21234400010775117
of2267440001074974
ice-cold2369440001071960104134178226247297
saline269444000107347797116166211
(0–4425454001072468118166
°C)612454001072781107
instilled747454001071968102132152172191236288
into106245400107206997145
the1234454001072979124
external1386454001074485117161188239281300
auditory1714454001074291142161190238266311
canal2052454001074184133175195
over2275454001074990135162
302465454001074590
seconds.2582454001073480123171221272306323
The425468001074292137
patient’s588468001075092120139183232259278309
head924468001074993134183
was11344680010765107141
elevated1301468001074464108149191218261312
and1639468001074290140
rotated1805468001072775102144171214265
according2096468001074182121168196244263312361
to2484468001072875
standard2585468001073463105154204245271320
protocols.425482001075077124151198239285305338354
During7994820010758107133152200250
right-sided106848200107274695143170194228246295340390
irrigation,14774820010719457292141181209227275324340
the1836482001072876120
BIS1976482001074565105
rose2101482001072673107151
abruptly2272482001074090117165215243262302
to2593482001072875
56;2687482001074487102
on2809482001074896
the425496001072876121
left,57249600107196387119135
it733496001071947
peaked806496001075095136174217267
at1099496001074169
15.119449600107448296
BIS1317496001074565105
values1449496001074082101149193227
returned170249600107267098146172221265316
to2044496001072875
baseline2145496001075091125169189207255299
(0–5)2471496001072466114157180
within2678496001076584112161179227
minutes425510001077492140188216258292
in737510001071966
both823510001075099126175
instances.1017510001071967100129170218259301335352
Importantly,565524001071991139187213243284331357375414425
no1006524001074795
neuromuscular1116524001074891138163209282328361400447465505530
blocking1662524001074968115155192212258307
agents1984524001074189132179205239
were22395240010764106132174
administered.2428524001074189161179226244275304345371413462477
The425538001074189132
patient573538001074989115133176222248
subsequently837538001073378126159202250297339386412430469
met13215380010773116143
all147953800107405876
established1571538001074275103143191210228259306349397
brain1984538001074975115133179
death2179538001074890129156202
criteria,239753800107396583110152177196235250
including2662538001071965104122168217425552001071967116
the565552001072876120
absence709552001074190124168216257299
of1032552001074872
brainstem1128552001074976118137185218247289363
reflexes,151555200107266993115159199242275291
positive1830552001075099133151179198239282
apnea2136552001074190139183223
testing,2383552001072870104133152200249265
lack2672552001071959100138
of2833552001074872
cerebral425566001074082108150199226267286
perfusion727566001074994120146195227245293341
on1084566001074896
CT1196566001075196
angiography,1308566001074188137155203252278319368417455466
and1790566001074188137
a19445660010740
predominantly2000566001075076119168216290308355395443469488528
isoelectric254456600107195199143162206247276303322362
EEG.425580001074283139156
Given607580001075675116159207
that839580001072877117144
BIS1009580001074564105
is1139580001071952
intended121658000107196793136184234278328
to1569580001072874
quantify1669580001074896137185212230254298
cortical1992580001074087114145164204245264
electrical2282580001074362106148178205224264306325
activity,2632580001074181112130171191219262273
such425594001073379118165
elevations605594001074362105144185211229276323355
are975594001074166108
paradoxical1098594001074990115156204251288306345386404
in1517594001071966
the1598594001072774117
context1731594001073985132158199238268
of2014594001074770
irreversible210059400107184470112151193219252270318337379
cessation2495594001073981113146186213231277325
of2835594001074770
intracranial42560800107196693119161201227269316335375393
function.835608001072372120160190209256305321
While11726080010774123141159203
not1392608001074896123
approved1531608001074190140167213253296346
for189460800107237097
brain2007608001075077118136184
death2207608001074993133160208
confirmation,2431608001074086135158178204277318345364411460475
BIS425622001074565105
monitoring5566220010774122171190218264291311358408
may9906220010773114153
respond1169622001072669103152201250299
to1494622001072875
extracranial1595622001074383114140182223249291339357398417
stimuli203862200107336281154202221239
through2303622001072876102149198247295
electromyographic26246220010743631071481782052524256360010773111157206232273321369387426
(EMG),867636001072464133188211224
autonomic,1107636001074087114160207255328346385400
or1523636001074774
mechanical16136360010772116156203243290308347388406
pathways.2035636001074990116164226267305338354
Caloric2405636001075191109157183202241
testing2662636001072769102130148195244
is425650001071951
a4936500010741
brainstem550650001075076118136184217246288362
evaluation,928650001074484125144191232259278326374389
and1334650001074189138
under1488650001074896145189215
typical1720650001072770120139179221240
circumstances,197665000107405985124171245277306347395436478512527
should2520650001073381129177196245
not2782650001074896123
affect42566400107416492135177207
BIS652664001074564105
which7776640010765113132172220
targets101766400107286995143188215250
cortical1287664001074087114145163204245264
signals.1571664001073352101149189208241258
We5656780010773115
propose696678001074976122172220253297
several1009678001073477118160186227246
mechanisms12716780010773117158205246293311344416449
for173667800107237097
these1849678001072875119152196
findings.206167800107244391139158205254286303
Cold2380678001075197116165
vestibular2561678001074183116145164212260279319345
stimulation42569200107346381155202221262289308356404
may8536920010773114153
activate1029692001074182112131172213241283
subtle1336692001073380130157176220
EMG15806920010742112168
activity1771692001074182112131172191219262
around2057692001074067114162210259
the2340692001072876120
forehead248369200107247299142190234274324
or2830692001074875
periorbital425706001075095121141189216266285314355374
region,825706001072770120139187236251
leading1103706001071963103153171219269
to1398706001072875
artifacts.149970600107416798117141184224255289306
Escudero1832706001074276117165214259285332
and2191706001074189138
colleagues2356706001074086106125169209259306350384
and2766706001074190139
Vivien425720001074666107127170219
et667720001074472
al.76372000107405975
reported862720001072770119168195226269319
similar1205720001073351125143162203229
findings,145872000107234391140159207256289305
where17877200010765113158184227
BIS2038720001074565105
values2167720001074182101149193226
in2417720001071967
brain-dead2507720001075077119137185213265309349398
patients3047258001075091118137181229256291
normalized3361258001074896123197238257276312355405
after378925800107416496138165
administration3976258001074191164183231249282311338379407425473522
of4521258001074872
neuromuscular4615258001074893140167214288335368409457476516543
blockade,5180258001075070118159197239289333347
implicating3047272001071992142161180220261289307355405
EMG34712720010742112169
interference365927200107196794136163190233260303351391434
[1,411227200109266983
2].421427200109477042822720010716
Cold3187286001075198118167
saline337128600107337594112160204
may35922860010774115153
also376228600107416092141
transiently392028600107275496144177195239287314333373
alter431028600107405987130156
electrode–skin4483286001074463107148178205252302346393427465485533
interface503328600107186693136162189231272314
conductivity,53642860010740871353047300001074995135165183224243271313324
particularly3387300001074990116146165205252270310336355395
in3798300001071865
critically388030000107396584112130170211229247287
ill418330000107193755
patients4254300001074990117135179226252287
with4557300001076483111158
fragile473130000107245192141159177220
skin,496830000107337090137152
generating5136300001074992140183209250277295342391
artifacts3047314001074168100119143186227258293
unrelated3367314001074997124168187228256299350
to3744314001072875
cerebral3846314001074184111154205232274294
activity.4166314001074283114133175194223266279
Hamal4471314001075899174215234
et4732314001074473
al.483131400107426177
emphasized49353140010744119169218260293312349393444
the5405314001072978122
susceptibility3047328001073481114155198248276295345365384402430473
of3547328001074872
BIS3646328001074665106
to3779328001072875
such3880328001073481122171
signal4077328001073453102151192211
distortion4314328001075068101131178205236255304353
[3].46933280010926729647873280010716
Other4829328001076191140184211
confounders5066328001074188137161209257306355400427461
include3047342001071967107126173223267
ECG3336342001074293146
pulsation,3504342001074998117149191218237285334349
subtle3875342001073481130158177221
movement,41183420010774122162206279324372399415
or4555342001074875
impedance4652342001071892141186236277325366408
fluctuations.508234200107244693134164212253280299347395428445
Myles30473560010770110129173207
and3275356001074189138
Cairo3434356001075193111138185
et3640356001074371
al.373235600107416075
reported3828356001072770119168195226269319
BIS4168356001074564105
elevation4294356001074463107147189216235283332
due4646356001074997141
to4808356001072774
unfiltered4903356001074896119139158186228255298348
cardiac5271356001074182108157175216256
signals3047370001073452102150191211244
in3317370001071968
an3411370001074190
otherwise3527370001074976125170196265284317362
isoelectric3916370001071952101146165210252282309329369
patient4312370001075092120139183232259
under4597370001074897147191218
full484237000107237392111
neuromuscular4979370001074994142168216291339372413461480521548
blockade3047384001075069118159197239288332
[4].33993840010926699334913840010716
Although3187398001075372100148196245294342
spinal3553398001073483102150191210
reflexes378739800107266993115159199242276
may40873980010773114153
persist4264398001075095121155174206235
in4523398001071967
brain-dead4614398001075077119137185213264308349398
patients,5036398001075091119137181229256291307
they5367398001072876120160
are3047412001074167110
not3179412001074896124
expected3324412001074484134179220250293343
to3688412001072875
affect378441200107416592136177207
BIS4013412001074565105
directly.414041200107496794137178208227267279
However,44414120010757105170213254297324335
muscle47984120010774121154195214258
contractions5077412001074087136163189231271302321369417450
near3047426001074995136163
BIS3238426001074666108
sensors,3373426001073480129163213241276293
triggered369342600107295676127178223250295346
peripherally,4066426001075197125145195245291318361381400441454
could4547426001074189138158209
produce4783426001075178127178227269312
misleading5123426001077594128148193234285304354404
elevations.3047440001074464109150192220239288338371388
Additionally,34624400010754103153172201220269318360379398439451
thermal3940440001072877122149225266285
stimuli425244000107346483158206225244
may45234400010775116156
provoke4706440001075078125166215254298
vasomotor5031440001074183117166241291319366394
or5452440001074876
autonomic3047454001074188117163212260334353393
reactions,3460454001072769110150180199247296329345
leading3825454001071963103152171219268
to4113454001072874
electrode4207454001074463107148178205252302346
noise4573454001074897116148193
[5,478545400109267088
6].489245400109467149614540010716
Vestibular3187468001074687121150169218266285326352
stimulation356246800107346382155203222262289308356405
may39904680010774115153
also416746800107405992140
influence433146800107196690112160204252292335
autonomic4689468001074189117163212260335353393
tone5106468001072874123167
or5296468001074875
cardiovascular53944680010741821083047482001074867114153194226266313331371397
rhythm.3460482001072674112142189262277
These3753482001074291134167210
fluctuations397948200107234592131161208248275293340388420
could4415482001073985132151199
result4630482001072668101147166193
in4839482001071965
pulsatile4920482001074997115147188215233251294
pressure5230482001074975118151183229255297
changes3047496001074087126173222265298
detectable3360496001074892119160200230270319338381
at3757496001074066
the3839496001072775118
BIS3972496001074564104
electrode.4091496001074362105145175201247296339353
Myles44604960010769107127170202
et4678496001074370
al.476449600107405874
[7]485349600109257197
emphasized49664960010743115164211251284301337379428
the5410496001072774117
vulnerability3047510001074088107154197223264313332350368396438
of3501510001074771
BIS3588510001074564104
to3708510001072873
extracerebral3798510001074382112138179219261287329378405446464
signals4278510001073451100147187206238
in4532510001071966
low-amplitude4614510001071966130158198270319338356384431480523
EEG5153510001074283138
states.5307510001073362102129171204220
BIS3187524001074565105
was33175240010765107140
designed3482524001074993126145194242286336
for384352400107237198
anesthetized3966524001074189133167196244288316335371414464
patients4455524001075091119137181229256291
with4771524001076584112160
preserved4956524001075077120153198224268311361
brain5342524001075077118137185
function.3047538001072473121162193211260309325
It3399538001071947
cannot3472538001074082130179227255
reliably375353800107277090108149199218259
differentiate403853800107496892120164190234282309328369396439
between4503538001075095123191235280328
cortical4858538001074087114145164205246266
and5150538001074189139
extracranial53165380010743831141411833047552001074067108156175215234
signals3306552001073351101149189208241
in3571552001071967
the3663552001072776120
context3807552001074187136163205245276
of4107552001074872
brain4204552001074976118136184
injury441355200107196785133159202
or4640552001074774
brain4739552001075077118137185
death4948552001074993133161209
[8].51815520010926709452745520010716
These5314552001074292136170214
limitations3047566001071937111129158199226245293341374
may34455660010773114153
lead3621566001071963103153
to3797566001072874
misinterpretation3895566001077392125143191218260287337364407435476503522570619
of4537566001074872
values,4632566001074182101148192226242
particularly4897566001075092118149168208256275315342361401
when53215660010765114158206
BIS3047580001074565105
is3172580001071952
used3243580001074881125175
outside3438580001074896124159177226271
its372858000107194782
validated3830580001074082101119168209236279329
indications.4178580001071967117135175217244263311359392409
In3187594001071967
summary,3279594001073481155228269295338350
we36545940010765109
report3788594001072770119169196227
transient404059400107285596144177195239287314
and4380594001074189138
reproducible4543594001072770120147194244291332350400419463
BIS5032594001074565105
elevations5163594001074363107147189216235283331364
in3047608001071967
a31316080010740
clinically318860800107415978126144184226245263303
and3508608001074189139
electrophysiologically3664608001074363107148178205252302351389423441489509557607626666708727745785
confirmed4466608001074087136159179205279324374
brain-dead4857608001074976118136184212264308348397
patient5271608001075092119137181229256
during3047622001074995121140188236
caloric330062200107398099146173192232
testing.3548622001072769103131150197246261
This3825622001074291109142
paradox3983622001074990116157206254291
highlights4290622001074866115162181199247295321356
an4662622001074088
interpretive476662200107196692134160210237279306325365408
limitation5190622001071937110128156196223242289337
of3047636001074872
BIS3135636001074665105
in3257636001071866
neurocritical3340636001074892139166212254280299327346386427446
care3803636001074081107150
and3969636001074189138
underscores4124636001074895145188215249289336363405439
the4579636001072876120
need4716636001074892137186
for491963600107247198
caution5033636001074082129157176224272
when53226360010764113157205
incidental3047650001071966106124173216264290331349
BIS3412650001074564104
activity3532650001074181111129170189216258
is3806650001071951
observed3873650001074897130174200243286335
in4224650001071966
this430665000107287694126
context.4448650001074086134160202241271287
We47526500010773114
encourage4882650001074391131177224250291340384
further528265000107237197128175219245
electrophysiologic3047664001074463107148178205252302351390424442490509558608626667
investigation3739664001071966106149183212231280320347366414463
to4227664001072874
clarify432766400107405999126145169212
BIS4564664001074665106
behavior4695664001075094143184223243291318
in5038664001071966
brain-dead5130664001074976118136184212264308348397
patients.3047678001075091118137181229256291308
This3187692001074292110143
article334669200107416899117158176220
complies3583692001074087161210230248292326
with3925692001076585113161
institutional410369200107186699128147175223251270318367407426
ethical4546692001074371120138178220239
standards.4801692001073463104152202242269317350366
All518469200107537290
procedures52916920010750771241652073047706001074996123166199
were32667060010765109135178
performed3464706001074994121148195222297341391
as3875706001074074
part3968706001075092118149
of4137706001074872
routine4228706001072774122150169217261
brain4509706001075077118137185
death4713706001074993134161209
assessment,4942706001074174107151185218292336384411427
and5389706001074189138
no3047720001074897
identifiable3163720001071968112161187206230250290340359403
patient3586720001075091119137181229256
data3862720001074990117158
were40407200010765108135178
included.4237720001071967108126174223267317333
CORRESPONDING485757009746100144188229269312367421475495549601
AUTHOR:1103757009749100141194250294312
1432757009518
Článek326275700984768110156198240
přijat35197570098467697119160189
redakcí:372475700982971119160201237258277
24.40177570095397589
8.412375700954055
2025;419575700953978115154166
Článek437975700984768110156198240
přijat46367570098467697119160189
k4841757009841
tisku:48987570098284983125172191
21.51057570095397585
10.52077570095397589
2025531375700953978115155
Dr.4857690095527688
Meltem590769009562102120145183249
Ceylan85676900954684120138174217
Delice,109176900955192109126162200213
ceylanmeltem93@gmail.com132276900953574109127164207272312329355393459497534591636702738755772787823865931948
Cit.39447690098476897118
zkr:407876900983678108128
Anest422476900954790130160186
intenziv44287690095165983122165198215252
Med.4698769009562102147161
2025;36(4):296-297487776900953977115154166206245266303323336376414454481516554592