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Clinical
Electrophysiology
AHandbookforNeurologists
Clinical Electrophysiology: A Handbook for Neurologists
Peter W. Kaplan and Thien Nguyen
© 2011 Peter W. Kaplan and Thien Nguyen. ISBN: 978-1-405-18529-5
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Clinical
Electrophysiology
A Handbook for Neurologists
Peter W. Kaplan, MB, FRCP
DepartmentofNeurology
TheJohnsHopkinsUniversitySchoolofMedicine&
JohnsHopkinsBayviewMedicalCenter
Baltimore,MA,USA
Thien Nguyen, MD, PhD
DepartmentofNeurology
TheJohnsHopkinsUniversitySchoolofMedicine&
TheJohnsHopkinsHospital
Baltimore,MA,USA
A John Wiley & Sons, Ltd., Publication
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Thiseditionfirstpublished2011,(cid:1)C 2011PeterW.KaplanandThienNguyen
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1 2011
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Contents
Preface,viii
Introduction,ix
Part 1: Central Nervous System Disorders
SectionA:Alteredconsciousness:confusion,deliriumandunresponsiveness;agitation
hallucinationandabnormalbehavior
1. Diffuseandfrontalfastactivity—beta,4
2. Diffuseslowactivity—theta,6
3. Diffuseslowactivity—delta,8
4. Frontalintermittentrhythmicdeltaactivity,12
5. Occipitalintermittentrhythmicdeltaactivity,14
6. Triphasicwaves,16
7. Low-voltagefastrecordwithoutdominantalphafrequencies,18
8. Alphacoma,20
9. Spindlecoma,22
10. Low-voltagesuppressedpattern,24
11. Burst/suppression,26
12. Diffuseslowing—toxicencephalopathy—baclofen,28
13. Diffuseslowing—metabolicencephalopathy—lithium,30
14. Diffuseslowing—metabolicencephalopathy—hypoglycemia,32
15. Diffuseslowing—limbicencephalopathy,34
16. Focalarrhythmic(polymorphic)deltaactivity,36
SectionB:Periodicpatternsofepileptiformdischarges,orseizures
17. Pseudoperiodiclateralizedepileptiformdischarges,40
18. Bilateralindependentpseudoperiodicepileptiformdischarges,44
19. Generalizedperiodicepileptiformdischarges,46
Part 2: Seizures
SectionA:TheDiagnosisofconfusionaleventsduetoseizures
20. Frontallobesimpleandcomplexpartialseizures,52
21. Temporallobesimpleandcomplexpartialseizures,54
22. Parietallobesimplepartialseizures,56
23. Occipitallobesimplepartialseizures,58
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vi Contents
SectionB:Statusepilepticus
24. Complexpartialstatusepilepticus—frontal,62
25. Complexpartialstatusepilepticus—temporal,64
26. Simplepartialstatusepilepticus—parietal,66
27. Simplepartialstatusepilepticu—occipital,68
28. Generalizednonconvulsivestatusepilepticus,70
Part 3: Conditions of Prolonged Unresponsiveness
SectionA:Locked-insyndrome,minimallyconsciousstate,vegetativestate,andcoma:disorders
ofconsciousnessandresponsiveness
29. Clinicaldefinitionsofimpairedresponsiveness,76
SectionB:Prolongedunresponsivestates
30. Locked-insyndrome—brainstemhemorrhage,82
31. Vegetativestate—postanoxia,84
32. Minimallyconsciousstate—afterlarge,multifocalstrokes,88
33. Catatonia—psychogenicunresponsiveness/conversiondisorder,90
34. SomatosensoryevokedpotentialPrognosisinanoxiccoma,92
35. SomatosensoryevokedpotentialPrognosisinheadtrauma,94
SectionC:EvokedPotentialsinConsultativeNeurology
36. Somatosensoryevokedpotentialsinmidbrainlesion—absentcorticalresponses,98
37. Somatosensoryevokedpotentialsindiffusecorticalanoxicinjury—absentcorticalandsubcorticalresponses,100
38. Somatosensoryevokedpotentialsinprolongedcardiacarrest—absenceofallwavesabovethebrachial
plexus,102
39. Somatosensoryevokedpotentialsafterprolongedcardiacarrest—absenceofallresponsesexcept
cervicalN9,104
40. Somatosensoryevokedpotentials—medianandtibialaftertraumaticspinalcordinjury,106
41. Visualevokedpotentialsinworseningvision,108
42. Brainstemauditoryevokedpotentials—inworseninghearing,110
Part 4: Peripheral Nervous System Disease
SectionA:weaknessand/orrespiratoryfailureinICUandontheward
43. CausesofparalysisandrespiratoryfailureintheICU,115
44. Theclinicalevaluationofneuromusculardisorders,116
45. Laboratoryevaluationofneuromusculardisorders,117
SectionB:Segmentalweaknessand/orsensoryloss
46. Evaluationofsegmentalperipheralneurologicaldisorders,120
SectionC:Respiratoryfailure/diffuseweakness
47. Amyotrophiclateralsclerosis/motorneuropathy,122
48. CriticalIllnessneuromyopathy,124
49. Brachialplexopathy,128
50. Femoralneuropathy,130
51. Sensoryneuropathy/ganglionopathy,132
52. Lumbarradiculopathy,134
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Contents vii
53. Guillain-Barre´ Syndrome—demyelinatingpolyneuropathy,136
54. Myastheniagravis—neuromuscularjunction,140
55. Myositis—irritablemyopathy,142
56. Statin-inducedmyopathy—toxicmyopathy/myalgia,146
Part 5: The Casebook of Clinical/Neurophysiology Consults
57. Occipitalblindnessandseizures—why?,150
58. Unresponsiveness—coma,vegetativestate,orlocked-instate?,152
59. Unresponsiveness—organicorpsychogenic?,154
60. Patientwithafrontalbraintumor—psychiatricdepression,paranoia,tumorgrowth,orstatus
epilepticus?,156
61. Patientwithidiopathicgeneralizedepilepsyonvalproate—Metabolicencephalopathyorstatus
epilepticus?,158
62. Unresponsiveness—psychogenic,encephalopathy,orlimbicencephalitis?,160
63. Respiratoryweakness—toxicormetabolic?,162
64. Failuretoweanfromaventilator/internalophthalmoplegia—bulbardysfunction,neuromuscular
junctionproblem,orpolyneuropathy?,166
65. Progressivesensorylossandpainfulgait—radiculopathy,toxicorinfectiousneuropathy,
ormyopathy?,170
66. Slowlyprogressivelegandarmweakness—radiculopathy,plexopathy,ALS,orCIDP/AMN?,174
67. Progressivethighpainandlegweakness—radiculopathy,vasculitis,neuropathy,oramyotrophy?,178
Index,181
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Preface
Clinical Electrophysiology was designed for residents, mental use of these tomes as they are essential to the
neurology attendings, and intensive care specialists. It understandingofclinicalneurology.
wasconceivedasabridgingtoolthatenablestheclini- The book is organized by the presenting neurologi-
calelectrophysiologicalinvestigationtobetiedinwiththe cal problem, for example, confusion, coma, abnormal
neurologicalconsultation.Thishelpsthecliniciantoorder movements, or difficulty weaning off a respirator, limb
the appropriate electrical test, understand the meaning numbness,orweakness.Withinthesetopics,theremay
of the interpretation, and then integrate these findings besomegeneraldiagnosticconsiderations,definitionsof
withtheclinicalquestiontoarriveatadiagnosis.Itmay terms,butofprincipalimportance,weprovideatestre-
furtherprovideinformationonthedifferentialdiagnosis, sultthatmaybeencountered.Forexampleinacomatose
theprognosis(wherewarranted),furtherrelevantinvesti- patient,wegiveanEEGshowinganinvariantalphafre-
gations,andsomebriefcommentsontreatment.Abrief quency pattern. There follows an interpretation of the
clinicalreferencelistisincluded. illustrated finding, differential diagnosis, prognosis, and
Inmakingthisportableaid,weplacedemphasisonthe references.Inthisway,the“vignette”startswithaclinical
inpatient clinical setting, giving the appropriate symp- problemandreachesadiagnostic,prognostic,orthera-
toms and signs, and pertinent electrophysiology results peuticend.
thatmightbefound.Thediscussionthatfollowsisspe- Becausethehandbookis“problem-oriented,”itisnot
cifictothefiguregiven.Hence,forexample,confusedpa- a comprehensive treatment of neurologic problems. It
tientsmayhaveanyofanumberofEEGfindings,butthe is briefer and covers mostly what a hospital clinician
discussionandprognosisaredirectedonlytotheonepat- might encounter on neurology consultation rounds in
ternunderdiscussion,forexample,triphasicwaves.Diag- a typical year. The last section, however, is a “case-
nosticquestions(particularlyonchronicconditions)that book,” which provides several rarer, but classic, clinico-
wouldlargelybeencounteredintheoutpatientclinic,or neurophysiologicalproblems.Thecasebookformatpro-
investigated after patients’ discharge, are not included. videsmoreclinicalinformationandleavesthereaderto
Hence,chronicneuropathies,palsies,Parkinson’sdisease, testhimorherselfasthecaseunfolds.Moreinformation
andmostgeneticconditionsareomitted.Similarly,condi- ontheelectrophysiologicalfindingscanbefoundinthe
tionswithoutelectrophysiologicrelevanciesorthosewar- respectivesectioninthehandbook.
ranting other types of tests (CT, MRI, and ultrasound) Pleaseusethebook,ifhelpful,inwordingyourconsults
are not included. Although a comprehensive tome ad- andinprovidingreferences.Dogiveusfeedbackintoany
dressingallneurologicaltestingwouldclearlybeuseful, shortcomingsandmajorareasthatwefailedtoinclude.
itwouldnotbeeasilyportable. Wehopeyoufinditausefulaide-memoireasyouaddress
For immediate relevance to neurology consults, we clinicalchallenges.
avoided general discussions of the neurological exami-
nation,diseaseentitiesandelectrophysiologyingeneral, PeterW.Kaplan,MB,FRCP
as there are a number of excellent books that address ThienNguyen,MD,PhD
theseissuesindetail.Werecommend,ofcourse,supple-
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Introduction
Wehavedesignedthishandbooktoaccompanyyouon Too often, the nature and significance of test results
yourrounds.Webelievethatthehandbookworksbestin canremainuncertain:dotheyrepresenta“redherring”?
the“middlestep”oftheneurologyconsultationprocess. Are they helpful in eliminating or confirming a particu-
Inthefirststep,historicaldataarecollectedandanex- lardiagnosisamongmany?Whatdotheytellusabout
aminationisperformedtoarriveatanopinion,possibly prognosis?
then suggesting complementary tests. If electrophysio- Standard textbooks abound to help with taking the
logicaltestsarerequested,itisatthenextstepthatthe history of a neurological complaint, performing physi-
handbookishelpfulinaddressingthesignificanceofthe cal examinations, or discussing the many disorders that
findings,thedifferentialdiagnosis,prognosis,andinpro- canbediagnosed.Othertextsmaydiscussindetailthe
vidingsomebrieftherapeuticdirections.Inthefinalstep, techniquesandinterpretationofEEG,evokedpotentials,
a concluding opinion can then be formulated. In other NCVs,andelectromyography.Thehandbookbridgesthe
cases,thehandbookcanbeusedtoreviewthemeaning gapbetweentheelectrophysiologicallaboratoryandthe
ofaparticulartestresultthathasalreadybeenreceived, bedside.
so as to be able to provide further information to the
patient’streatingphysicians.
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PART 1
Central nervous system disorders
Section A: Altered consciousness: confusion, delirium,
and unresponsiveness; agitation, hallucination,
and abnormal behavior
Thesearesomeofthe“alteredstates”thatpromptneu- fusionalstates”duetotoxic/metabolic,infectious,orictal
rology consults. Patient problems rather than specific, disturbances.
prepackaged“diagnoses”generateconsults.Hence,clin- Somedefinitionsincurrentuseareasfollows:
ical training rather than standard texts is the major
Delirium: An acute alteration in cognitive function with
source of learning the physician’s approach to manag-
impaired short-term memory, sleep cycle inversion,
ingproblem-orientedquestions.
sometimes with increased motor activity in the form
Unfortunately,thecauses(ordiagnoses)underlyinga
of agitation and tremulousness (think withdrawal or
particular complaint are legion–-consider the potential
deliriumtremens),oftenwithamnesia.
causesof“dizziness,”forexample,lowbloodpressureor
Confusion:Ageneraltermthatusuallyneedsfurtherdef-
neurilemmoma,migraineorbrainstemstroke,lowblood
inition.Often,however,itisusedtorefertoastateof
sugar or otolith disease, and multiple sclerosis or Me-
impaired language output, orientation, the ability to
niere’sdisease.
followcommandsandtoretaininformation.
Clearly the constellation of symptoms and signs (and
Altered mental status: This could subsume the above.
those absent) from the patient’s description of clinical
Also a non-specific term, which could apply to psy-
features (the syndrome) will pare down the possibilities
chosis,coma,ordementia.Italsoneedsfurtherspeci-
and direct the diagnostic evaluation and investigation.
fication.
Excellent texts are available that can address “lists” of
Encephalopathy:AGreek-derivedtermfordiffusebrain
probablealternativestoparticularcomplaints.Maybethe
dysfunction-–alsonon-specific.Butthengloballycon-
future will lie in the use of a palm-held computer into
fused patients are often perforce “nonspecifically”
which the complaint/symptom will be logged, followed
cognitivelyimpaired(aclueinitself).
by associated (or not) clinical features, resulting in the
generationofa“probabilitylist,”whichcanbeusedeven Ortheremaybeaclinicalquestionattheoutset:Isthis
whileoneisroundingonpatients. nonconvulsive status epilepticus (NCSE)? This is specific
Inthissection,weaddresscertainstatesofalteredcon- andprovableonewayortheother.Onemightconsider
sciousnessorbehaviorthatfallshortofcoma.Locked-in thevarietyofclinicalfeaturesseenwithNCSEandobtain
states,minimallyconsciousstates,akineticmutism,and anEEG.
vegetativestatesareadifferentorderof“unresponsive- So where to go? Once the probable type of higher
ness,” and are found in their own section further on. cortical disturbance has been tested, for example, with
Thoseexamplescontainedhereinvolveacuteorsubacute amini-mentalstatusexamination,moredetailedtesting
globaldiminutioninthelevelofconsciousness,vigilance, of the patient’s orientation, language, memory, ability
memory, and cognitive processing in keeping with en- to follow commands, to interpret events (the “cookie
cephalopathies(“alteredmentalstatus”)or“acutecon- thief” picture), and then a probability list of diagnoses
Clinical Electrophysiology: A Handbook for Neurologists
Peter W. Kaplan and Thien Nguyen 1
© 2011 Peter W. Kaplan and Thien Nguyen. ISBN: 978-1-405-18529-5
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2 SectionA:AlteredConsciousness
canbeproduced.Thismightincludeaconsultwiththe tiformabnormality,turnthentothesectiononseizures
following: (Part2)forfurtherelectroclinicalcorrelationsandsugges-
tions.
Possible toxic/metabolic en- The easier questions to answer are often those cen-
cephalopathy. Suggest the exclu- teredonarequestforprognosis.Inparticularinstances
sion of systemic infection in this such as after anoxia, “ball-park” answers can be pro-
patient with chronic diminished vided,orevensomehighlyexactones.Forexample,the
tolerance to the many causes prognosisinalethargicpatient3daysafterCRAcanbe
of encephalopathy (e.g. cerebral given with much support from the literature, and from
atrophy;dementia).Consideralso EEG and SSEPs (somatosensory evoked potentials). For
investigation of ictal/post-ictal thesetypesofquestionsandforthosepatientsincoma,
possibilities(withanEEG). locked-in states, and vegetative states, please refer to
Part 3 on these disorders. A brief overview on progno-
Ifinthecourseofinvestigatingalteredconsciousnessor sis and evaluation can also be found in the section on
abnormalbehaviorinapatient,theEEGrevealsanepilep- EvokedPotentialsinConsultativeNeurology.
