Stereota
Proc.of the Amer. Soc.Stereotacticand Functional Neurosurgery,Durham, N.C. 1983
Appl. Neurophysiol.46: 160-166(1983)
StereotacticRadiofrequencyLesionMaking
,l
E.R. Cosman,B.S. Nashold,P. Bedenbaugh
Instituteof Technology,Cambridge,Mass.,
Departmentof Physics,Massachusetts
USA; Departmentof Neurosurgery,Duke University Medical Center,Durham,
N.C., USA
i
I
Key Words. Lesion. Stereotacticsurgery' Radiofrequency'Electrode
Abstract.The physicalprinciples of radiofrequency(RF) lesion making in stereotactic neurosurgeryare summarized.Empirical data are given on the relationship beCurrentlyacceptedrangesoflesioningpartweenlesionsizeand lesioningparameters.
AdvancedRF lesionelectrode
ametersfor selectedstereotacticproceduresare discussed.
designsaredescribedwhich improve the capabilitiesto reachand confirm targets.
Backgroundto RadiofrequencyLesionMaking
Of the many techniqueswhich have been applied for localized
therapeuticdestructionof nervoustissue,the radiofrequency(RF) lesion method has emergedas the most effectiveand widely used.The
reasonsfor the successof this method are the following: (a) excellent
circumscriptionof the lesionvolume;(b)excellentcontrol of the lesion
processusing temperaturemonitoring to quantify the lesionsize,prevent boiling, charring,and sticking,as well as to producedifferential
destructionof neural tissue;(c) excellenttarget localization using stimulation, impedancemonitoring, and recording,and (d) versatilityof
RF electrodeconfigurationsto optimizelesionsizeand adaptto intracranial,spinal,and peripheralnervelesioning.
The Principlesof the RF Lesion
i
Fig. l.
li
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I
the 'active
on thes
between
trolytes
whichp
givenby
perature
pattern,
blood
tionsto
fig.1).wi
tissue
is
distance
44-45"C
tem
ous100
thetip di
aretissue,
age.
30-60s.
The principle of RF heatingis illustratedin figure l. The RF voltageproducedby the generatoris impressedbetweenthe exposedtip of
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StereotacticRadiofrequency Lesion Making
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INSULATED SHAFT
ll
Fig. 1. Electromechanicar
dissipationand enlargementoflesion size.
the 'active' lesion electrodeand the dispersiveelectrode(i.e.,
a ger-pad
on the shoulder),which causesan electricfield pattern
rineg
to form
1r
betweenthe electrodes,which in turn drives the ions
in the tissueelec_
trolytes back and forth at the RF. It is this ionic
current densityi: d
which producesmorecular friction and thus tissue
heating-ui,t. ,u,.
given by j2/ o, where o is the tissueconductivity.
The equilibrium temperature distribution near the active electrode
dependson the E field
pattern, o, the tissuethermal conductivity,
and heat convection from
blood flow. It can be calculated theoretically for
simplified assumptions to predict the isotherm patterns near the
tip (iashed lines in
fig' l)' within the 44-45t isotherm and at higher
t"rprrutu..s, brain
tissueispermanentrykilled, and this definesthe lesion
volumeIl].
Figure 2 illustratesschematicallytemperaturedistributions
versus
distancefrom the electrodetip for two tip iemperatures
Tl and T2.The
.C
44-45 radius increaseswith tip temperature
up to a maximum when
the tip reaches100'c, the boiling po1nt.rhus
ty monitorin;the tip
temperature' one can gaugethe lesion sizeas well
as avoid thJdangerous 100"c limit. Factorswhich most strongly determine
lesion sizeare
the tip dimensionsand the tip temperature.of
much lessimportance
are tissueresistance,thermal conductivity, or resion
current and voltage.Also, lesion sizereachesequilibrium ior a given
tip temperaturein
30-60 s. The most consistentlesion sizesare achieved
by t"tiirrg the lesion come to equilibrium-for a given tip temperature
in the range of
0-30 s, rather than increasingtheiize by increasing
the lesiontime.
162
Cosman/Nashold/Bedenbaueh
Stereo
U S IN (
Virllal
Tip Tompo.atura
PROC.
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t
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THALAM
Permanonl
Lasid
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t
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Zom ot R.v.r6ibility
C IN G U L
F
37.O
Eody TamparaluaG
Distam. trm Elrct.od.
(arbltJ.ry unit. )
Tlp
Fig. 2. Tissuetemperatureversusdistancefrom electrode.
F i g . 3 I.
Empirically DeterminedLesionParameters
With theseguidelines,empirical data on RF lesion size versustip
size and temperaturefrom human stereotaxyare useful. Though such
clinical data are rare, figure 3 showssomegatheredfrom severalstereotactic neurosurgeons.Changesin lesion sizemay occur within weeks
after surgery,so the sizesin figure 3 are probably lower limits. Figure 4
shows examplesof two of theselesions [2, 3]. Note that in the caseof
the cingulum lesions,some spreadof the lesion toward the ventricle is
seen,possibly indicating a lower impedancepathway through the CSF.
No marked differential spreadto the white matter is noted, as has been
discussedin the literature. Some preferential heating of either gray or
white matter is expecteddependingon the relative position of the electrode in each.Recently,we have studiedthis questionfor lesionsin animals, and shall report on it elsewhere.
Figure 5 showsthe range of parametersusedby severalstereotactic
surgeonswho have considerableexperiencewith the respectiveprocedures. For thalamotomies,this suggestssome variation in lesion sizes
produced. The 1.6-mmtip diameter by 5- to 7-mm length seemsa bit
large.We recommenda l.l- to 1.6-mmtip diameterand 4- to 5-mm tip
length as a norm. The cingulotomy and hypophysectomyparameters
B.
Fig.4.I
StereotacticRadiofrequencyLesionMaking
r63
U S I N G :R A O I O N I C ST Y P E T M E L E C T R O D E S
ELECTRODE
P R o c ._ . I i ? _ - _ T E M er M E
OIAM. LENGTH
("c)
(MMl
THALAM, I.I
t
t,?
372
360
3
65
CINGUL, I.6
rr
lA
lo
80-90
"
1.6
ro
80
L E S I O Ns I z E
AB
(MM)
,ir1[
(sEc)
2YR
t20
?4
60
5M
60
6M
ro
t o -t 2
6M
ro
t2
88
--r
*
DraM
0 .Fr r P
Fig.3. Postmortemlesionsizesversusheatingparameters.
4
of
is
been
yor
I
elecan-
5rd vanlricle
+l4mm.
slzes
a bit
tip
Fig.4. RF lesionsin thethalamusand cineulum
t64
Cosman/Nashold/Bedenbaush
S S F U L T H A L A M O T O M YP A R A M E T E R S
T Y P E R A D I O N I C ST M E L E C T R O D E S
Stereota
SUCCESSFULCINGULOTOMYPARAMETERS
TYPE:
R A D I O N I C ST M
ELECTRODES
NASHOLD
TIP DIMS,
DIAM. LENGTH
(itM)
3
5
3
5
4
5
5
7
3
,.i
1.2
1.4
t.6
t.6
1.6
<.1
TEMP.
(.C )
70
75
65
65
75
70
TIME
( S E C ).
rp DrMs. rEMp. rrME
DIAM. LENGTH
(MM)
t?o
l?o
?.1
('c)
4,4
ro
80
TEMP
('C )
--
T I M E STAGED
(SEC.) L E S I O N
22OAPART
AND AT
2 LEVELS
80
to
I/4 MM
68
ZERVAS
S I D E- T I P P E O
ELECTRODE
STRAIGHT
TIP
2.t
7
|
LCE LEVIN ELECTRODE
S U C C E S S F U LH Y P O P H Y S E C T O M
PY
ARAMETERS
D I A M .L E N G T H
(MM)
60
S U C C E S S F U LC O R D O T O M YP A R A M E T E R S
60
TIP OIMS.
I
60
75
65
70
;naEr
782602r
AVEFAGE PARAMETERS
1,47
ilt?&?
(sEc) *o ?,1'fi1
r20
20 GA.
\wEr--
t
lF--N
tr
tsT
75c,30SEc.
?nd
80 c ,30 sEc.
3rd
85 C ,30 SEC.
2MM
T R I G E M I N A LT R A C T O T O M I E S
I/2 MM
BEGINWITH
t.oa
an qFa
I8 GA,
B IL A T E R A L ,
2 LESTONS,
5 M M A P A R TD R E Z L E S I O N S
I/4 MM
B E G I NW I T H
75'c
, 30 SEC
Fig.5. Successfully
usedlesionparameters.
We
sertion
both on
are probablylesscritical.Somesurgeonsprefersideoutlet-tippedelectrodesfor theseproceduresto achievelarger,axially asymmetriclesion
volumes.The recenttechnicaladvanceof fine gaugecordotomy thermocoupleelectrodesbrings all the advantagesof safetyand control to
lesionmaking in the smallstructuresof the cord.
It is notableherethat thereare unpredictablevariableswhich can
affect lesion size and shape.Low impedanceCSF cisternscan draw
heat away from neighboringtissues,and largeblood vesselscan carry
heat away, cooling tissuenearby.Overall,however,consistencyof results from RF lesioningin the brain using acceptedparametershas
beenexcellent.
inglsti
tional
trode
electrode
ample,ei
(lower
mors,
precisely
insulated
located
the
brain.
StereotacticRadiofrequencyLesionMaking
165
NASHOLO - COSMAN
RIT{G ELECTROOE
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RECOROIXG/ Z
STIXULATING
RING
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RECORO
STIMULATE
STIITJLATE/
LESIOT
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STIMULATE
Fig.6. Improved electrodedesign.
Improved ElectrodeDesigns
We are presentlydevelopingRF electrodeswhich, with a singleinsertion tract, will permit the recording, stimulating, and lesion making
both on and off electrodeaxis. At the top of figure 6, a simple recordinglstimulating ring is located proximal to the lesion tip of a conventional straight electrode.Below that is an universal stereotacticelectrode system comprising an universal insulated cannula and many
electrode and biopsy deviceswhich can be passedthrough it. For example, either a straight or off-axis stimulating and recording probe
(lower figure) may be used to probe the brain for neural targets,tumors, and so on. Then, a RF probe may be insertedto createa lesion
preoiselyat the point of interest.The off-axis lesion probe may have an
insulated surfaceexcept for the very tip, in which a thermal sensoris
located for preciselesion control. Such systemsshould greatly expand
the possibilitiesin stereotaxywhile posing minimal intrusion into the
brain.
Cosman/Nashold/ Bedenbaugh
r66
References
lesiongenerationin neuroCosman,B.J.;Cosman,E.R.:Guide to radiofrequency
surgery.RadionicsProcedure
TechniqueSeriesMonographs(1974).
Fager, C.: Surgical treatment of involuntary movement disorders.Lahey Clinic
Foundation Bill. 22: 79-83 (1973).
Hurt, R.W.; Ballantine, H.T.: Stereotaxicanterior cingulate lesionsfor persistent
pain.Clin. Neurosurg.21: 334-351(1973).
Proc.oftheA
Appl.Neuro
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Anton
Buffalo
usedto
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procedures
An
greeof a
deep
neuroabl
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awake
the drug
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while
ing fi
erly,
Prof. E.R. Cosman,Massachusetts
Instituteof Technology,
Bldg.58-014,Cambridge,MA 02139(USA)
ableto
ditions
@le83s
0302-211