A procedure for preparing a multielectrode lead for intracerebral recordings

A PROCEDURE FOR PREPARING FOR INTRACEREBRAL

A MULTIELECTRODE RECORDINGS 1

LEAD

GIAN EMILIO CHATRIAN, M . D . , CLETUS S. POLLACK a n d MAGNUS C. PETERSEN, M . D .

Rochester State Hospital, Rochester, Minn. (Received for publication : July 31, 1958) Tile feat/tres of n multieleetrode lead used for iutraeerebral recordings in h u m a n p a t i e n t s have been described in a previous article (Chatri:m, Dodge, P e t e r s e n and Bickford, in course of publication). The present note deals with the procedure followed "~t tile ]~ochester State IIospital in preparing such leads.

WIRE

AND

WINDING

MACIIINE

A c c o r d i n g to the previous description, our depth leads are made of 7 or 13 strands of t y p e 316 2, 40 (77.5 /,, 0.01)31 in.) or 42-gauge (62.5 tz, I).0025 in.) stainless steel wire a covered b v quadruple formvar insulation.4 The wlrious s t r a n d s which compose tlle lead are wound t o g e t h e r in a s h a f t lty means of a w i n d i n g machine 5 (fig. 1) which consists of an alunfinum base 91.4 em. long (36 i l l . ) , 15.2 era. wide (6 in.) and 2.5 era. high (1 in.). A t the r i g h t end of this base is m o u n t e d an AC operated g e a r m o t o r 6 (A)7 which drives a b r a s s w i n d i n g a r m (B) t h r o u g h the redaction gear. The r o t a t o r y speed of this a r m is 400 r.p.m. The n u m b e r of revolutimls d u r i n g a given lleriod of time is indicated by a counter (C). The winding a r m is provided, left to right, with a strqml lock ( I ) ) , a s t r a n d s e p a r a t i n g edge ( E l with 3:~ slots, and a s t r a n d s u p p o r t i n g b a r I F ) with two (.entr'd vertical g u i d i n g pins directed respectively tipw a r d and d o w n w a r d ( G ) . On tit(,' :fluminum base below the g u i d i n g arm is a cutting guide ( I I ) represented b v a white phenolic plastic sheet. T h i r t e e u black lines (;.5 lnnt. apart, nlnnl)ered from right to left, are etched on this guide l.,rl)endicular to the w i n d i n g arm. At the left cml of tile metallic base a sliding board (l') is ntmmted. This consists of an a h n n i n u m plate which slides in a track ( J ) 4.8 era. (1~. in.) :d)ove the bast,. On this plate are m o u n t e d two side b r a s s rails ( K ) across which an a h u n i n m n s t r a n d s u p p o r t bar (I.i may be moved and secured b v means 1 T h i s study ,,*as suI/porled lit Dart by a r e s e a r c h g r a n t iroln lhe M i n n e s o t a D e l l a r t m e n t of Put)lie W e l f a r e . 2 T h e type 316 s t a i n l e s s steel is a c h r o m i u m (16-.18 p e r c e n t ) , n i c k e l (10-14 pe r c e n t ) , nmlybdenuni (2 a per c e n t ) s t a i n l e s s steel which is p a r t i c u l a r l y r e s i s t a n t to a t t a c k by InoSt chenli('a Is. 3 Slllll)lied to Iis by tile ] ) r i v e r H a r r i s Co., H a r r i s o n , New Jersey, 4 T he f o r n w a r is a t h e r n I o p l a s t i e ( s y n t h e t i c ) e na me l. 5 M a n u f a e t u r e d by the A r k a y Co., R o c h e s t e r , M i n n e s o t a . Its design is a m o d i f i c a t i o n of an e a r l i e r o r i g i n a l model b u i l t by tilt' En~rineering Section of tile Mayo Clinic. 6 .'~Ialnlfa(:tllre(l by Gle a se n Avery, Inc., ~,ullnrr:, New Yorl<, 7 Tills and oilier le tte r s llSed a r e tlle ol/es on the figln'e.

of a thumbscrew. At tile center of the b a r are two vertical pins ( M ) , 1 ram. a p a r t . A locking plate I N ) nla v be secured over them hv llleHllS o f a t l l l l n l l l screw. Oil the a l u m i n u m plate, between the two side rails, a c u t t i n g guide (()) made of white phenolic p]astie is mounted. T h i r t e e n black lines, 1 cm. a p a r t and n u m b e r e d f r o m left to right, are etched oil this guide perpendicular to the side rails. The spaces between the black lines gre divided into halves by red lines. At the left extremity of the cutting guide is an aluminunt s t r a n d Selmrating edge (1'~ with 13 numbered slots. Three s t r a n d locks ( Q , Q: nnd Q:) are m o u n t e d near tile edge of the cuttin~ }auide. The machine is completed with a sliding beard hick (11) represented by a pin whieh mqy lie i rlscrted into a hole going t h r o u g h both the sliding board :,nd its track, thus locking the liimrd in place. A s p r i n g (St keeps the sliding bot, rd under adequate tension during tile winding operation when the lock (R~ is remow.d. M A K I N ( { T I I E 1 ) E I ' T I [ LJ:LkDS qThe procedure followe,l for maliin~ our multielectrode depth legtds nmy be described as consisting of seven steps: (1! thro;,din~ and ~xin,iing ~1,' w i r , : (2; cutting the s t r a n d s , t the h,ft end of the m a e h h m ; (3) wimling the s t r a n d s at the loft end of the machine: t-t) m:lking t h , ternlinal coil; (5") c u t t i n g qnd s t r i p p i n g the s t r a n d s :d the riizht end of t h e m a e h i n e : (6} testing 1t., firdshc,I h,,,Is,:~L,I (7~ coding 1h¢, finished lemls. St~']* f. Tl~r¢~at/i~lfl a , d lI'indhl.e? lkc 71"ire. l"irst tile caps of tilt" lot, ks Q,, Qe and I) :lt'e rcmove,I :dong with plato N. Then tin' sliding ],~ar,[ [ is secured with pin ]{. The bar 1, is fix~,d by nli,:lns of its thnnd)screw in the position required l,v the n n m l w r of s t r a n d s in the lead. \Vhel~ :1 scven strand lead is desired, tile b a r L is secured in :1 position in which tile left edge eorrespond~ 1o lira' 1~1 ~,f the cutting ~o'ui,h,. \Vhetl :~ ]:gstran,l electrode i~ ~xante,], bar I~ is fixed at the rila'ht extremity el! the ~'ui,le. The loose end of the wire frmn the :gupldy spool is secured to lock Q,; then 1he wirl. is lmsso,[ through a series el' points, nanwly: slot 1 .,ff o,lge l ' ; the space between lthls M; tlw upper pin (; of tile winding arm (side nearest the o p e r a t o r ) : slot I of edge E : slot of lock D; slot 13 of edge E: low
M U I , T I E L E C T R O D E I~EAD FOR I N T R A C E R E B R A L R E C O R D I N G S lock Q~. At this point the wire is back to the left side of the machine where the procedure was initiated. This procedure is repeated in the same manner utilizing each time the outermost available slots of edges E and P so that the center of both the strandseparating edges is gradually approached. When the correct n u m b e r of strands is reached (seven or 13), the wire coming f r o m slot 4 or 7 of edge P is secured to lock D. A t the end of this procedure the cap of lock Q2 is replaced and also the plate N is screwed to b a r L. I t will be noticed t h a t the lock Q3 has not been used in this procedure. Some operators, particularly if left-handed, m a y find it easier to s t a r t the t h r e a d i n g operation front this point. The pin lock R is removed so t h a t only the tension of the s p r i n g S h o h l s t h e s t r a n d s taut. Then the m o t o r A is switched on by means of a foot switch "~ud allowed to run for :~i)proximately 110 revohltions iudic:tted by t h , ~,om~ter (L As :~ result ef this operation the

359

strand) is brought back and taped to bar L to be used later for making the terminal coil (step 41. The stripping process of the renlaining strands is then started with plate N tightly in place. This procedure removes the formvar insulation from the ends of the strands for a length of approximately 1 Innl. This is done by dipping vertically the end of e:~eh s t r a n d separately in a liquid solvent ( s t r i p v a r ~-) placed tit a small container 1 ram. in depth. A f t e r the s t r a n d is removed front the liquid, the solvent is qllowed to remain on the wire until the coating disintegrates. Then the solvent and coating are wiped o f f with a soft pat)or. I t will be f o u n d t h a t tile insula;ion at the end of the s t r a n d has been completely removed leaving a clean shiny surf'tce. ]?he h a t e d ex':renlity of each strand provides electricM cont:wt wLth t h , b r a i n tissue a n d r e p r e s e n t s [11l electrode. Slop 3. JVittcli?u! the StraJtdx at l / , L e f t E~ld of tlw 31achi,~'. While all the s t r , nds ~Lt the h~ft end

Fig. 1 Winding l]laehitle. See text for explallat]iin of letters. s t r a m l s iil'e ~.vot|lHl tightly in a smooth s h a f t between the l,ins G~ and G~ ttnd the pins M~ and ~{,,. F r o m these points they diver~'e and reach the correspondiug edges E and P. SIcp 2. Ci~li/Iq mid S t r i p p M g the Stra)tds at ttl~ L ~ f t E~td of the Machine. A f t e r the winding, the s t r a n d s are cut at the left end of the nlaehine with a small p a i r of scissors. The s t r a n d ne:~rest tile oper.~tor is cut closely to lock Q~. The next s t r a n d nearest the o p e r a t o r is cut in correspondence to lille I of the c u t t i n g / u i d e O. The renmining str:mds :~re cut in correspondence to lines 2, 3 and so forth, preeeeding f r o m left to right, so t h a t their ends will be 1 ('m. a p a r t . I f a smaller i n t e r w d is desired, the red lines on the c u t t i n g guitle O lnlty be ase,l in conjunction with the 1)l'lck lira's to give 0.5 cnl. spacing. When the cutting is complete at the left end of the nmchine, the s t r a n d n e a r e s t the o p e r a t o r (the longest

of tile ulachine are hchl under tension with one haml to avoid t w i s t i n g and kinking, tht~ l,late N is removed with the other hand. The motor is then st',rt(.d "~g:fin :lml the loose emls of the s t r ' m d s are ~lfi,led by the o p e r M o r ' s fingers so t h a t they :~re smoothly wouml to complete the solid shaft. St~'p ~. M~d,:il~(] the Tcrmi~al ('oil. The sh:lft ~hen is cl'mtped to b a r L hy me:ms of p1;ite N in such a m a n n e r tlmt the end of the m~xt to the loni2,est s t r a n d is :Lt lhe h!ft edge of b~r I~ ~nd the longest s t r a n d pr{}trudes f r o m it. The longest sl r:lnd is stri])ped of insulation froul tlw end to 2.7 era. frolu the h,ft edge of the b:lr. The lmred extremity of this str:lnd is wr:lpl}ed h}osely with 12 t u r n s :H'oand "l stilet, 0.51; Hill[. ill di:mmter, held perl)endicul:lr t(, it. Then, while tile operator hohls the loose (,lid [if the 1 Sullplied by Walseo Electronics Corporation, Los Angeles, Calif.

360

O . E . C H A T R I A N , C. S. P O L L A C K and M. C. P E T E R S E N

strand w i t h one hand, w i t h the other the stilet is t w i s t e d clockwise t o w a r d tile bar L; t w i s t i n g is stopped w h e n tile stilet is 0.9 em. froin the t)ar. These distances are i n d i c a t e d on our m a c h i n e b y a m a r k e d strip of tape on the cutting guide. D u r i n g this ol(eration , p r o p e r m a u e u v e r i n g of the stile( and adequ:lte tension of the wire produce a tight, closely wound u n i f o r m eoil l about 1 ram. in length. The stilet is then rotated "dmut 911 degrees so t h a t the coil and stile( lie paralhd to the lead. A t this I/oint it will be m>tieed t h a t the lower cud of the coil is a p p r o x i m a t e l y 1 era. f r o m the upper electrode and that it inchides about 1 to 2 mul. of b a r e d wire. Finally the stilet is ('emoved, and the excess wire f r o m tile eoil is cut ander a n m g n i f y i u g ghiss w i t h the aecilracy lleOesspin.q the £'tra~ds ~t file Right E , d of the Machine. Next the ends of the s t r a n d s on the right end of the machine are cut by following guide 1I. The s t r a u d nearest the operator is cut in correspondence with liue 1. the next nearest in eorrcslmmlence with line 2, and so on, proceeding from right to left. Therefore, the ends of the various s t r a n d s will be 0.65 era. "(part, an,l the s t r a n d t h a t is the hnigest ;it the left of the w i u d i n g machine is also the longest at the r i g h t cud of the machine, while the (tilt! which is the shortest at one end is also the shortest at tilt, other. The d i f f e r e n t lengths of the strands will ln'ovide ideutifieation of them when they are inlph/nted w i t h i n the brain. A f t e r the strands el( the r i g h t end o f the lliaehiue are cut, t h e i r ends are stripltod w i t h s t r i p v a r f o r ;illproxiliilltoly 1.3 Clll. (0.5 i n . ) . This olid (if the strand will lie utilized for eouneetiou with the wire~ eonling frgin receptacles. Stcll 6. 7'~slin:l the' Fi,iMl+'d L~ay accidental damage ta tile insulation during llreparation of the le.tds. The loose ends of the s t r a n d s of each lead are connected to clip t e r m i n a l s of a selector switch which is in series with a neon light. The AC line volt'lge (117 volts) is used as the test voltage. The lend is left in the opeu air so t h a t no conduction c a n eecur b e t w e e n elee(redes. I f u short exists between strands, this d o s e s the circuit whieh eauses the neon l i g h t to glow. The lead is therefore discarded. The wet test measures the intereleetrode impedance in it 0.9 per cent solution of s o d i u m chloride. The loose ends of the strands of each lead are connected to the clip t e r m i n a l s of a selector switch. :By means of this switch :t t e s t i n g current is passed be1 T h i s coil is n o t u s e d a s a n i n d u c t o r b u t a s for the process of lead implantation into tho brain.

a

device

tween a d j a c e n t electrodes. The current is represented I>y the short hi-phasic uonpol'u'izing pulses described by Lilly und associates ( 1955 ) and nlodified by H u g h e s and Mazurowski (1958) using a repetition rate of 180 pulse pairs per second. Voltage and current (voltage drop across a l(i(t-ohnl resistor) are m o n i t m e d on a singh, beam eathode-ray oscillograph (Tektronix type 532 with type 53/54 C dual tl'llge plug-iu pre:tm plifier). The current is kept eollstant by malmal adjustlnent (usaally 11) ]xA from baseline lo positive or uegatiw, peak) so t h a t only the vollage varies iu relation with the impedance vahles. With our electrodes this usually measures betweetl 4 and 12 kiloohms. Wheu qn impedance higher than 15 kih>ohms is found, the lead is discarded. 5't¢'ll 7. Co
DEPTH

I,EADS

For recording purposes the s t r a n d s of each leqd, whose bared lower tips represent the eleetrodes, m u s t be connected at their upper extremities to some simple devices providing rapid connection to, and disconneclion from, the i n p u t of tim E E G machine. This operation may be done before or a f t e r tile implantation of the leads in the
MUI~TIELECTRODE LEAD FOR INTRACEREBRAL T h e r e f o r e , two steps n m s t be described for the proccdure of c o n n e c t i n g tile d e p t h l e a d s : (1) w i r i n g t h e reeepta,'les, a n d (2) c o n n e c t i n g the receptacle wires to the s t r a n d s of the d e p t h leads. Wiring the tl(~ceptaeles. W h e n the sevcwelectrode leads Imvc been h n p l a n t e d , t h e y are c o n n e c t e d to 21c o n t a c t m i n i a t u r e receptacles.1 T h e 21 c o n t a c t s are divided into three g r o u p s following t h e l e t t e r i n g code p r i n t e d on t h e reccptable. I n each g r o u p the cont a e t s arc n u m b e r e d f r o m 1 to 7. T h e corr(,sponding I)ins are soldered to s t r a n d e d silver wires covered by colored plastic i n s u l a t i o n 2 following t h e R E T M A 3 ('clot code. The loose ends of t h e wires in each g r o u p of scrim wires are c u t at d i f f e r e n t l e n g t h s , a b o u t (/.65 era. a p a r t , to m a t c h t h e l e n g t h of t h e v a r i o u s s t r a n d s of the lead to be c o n n e c t e d to t h e m . I n other words, t h e l o n g e s t wire of the g r o u p is connected to the s h o r t e s t s t r a n d of t h e lead, a n d the s h o r t e s t to t h e longest. T h e p l a s t i c i n s u l a t i o n is removed for a b o u t 8 ram. (1,/a in.) ; the silver s t r a n d s are t w i s t e d t i g h t l y , a n d th(qt t i n n e d w i t h radio solder. Co~necting the tleeeptacle Wires to the Stra*~d.~ of lhe Depth L(,ads. T h e leads e m e r g i n g front the p a t i e n t ' s b a n d a g e are i d e n t i f i e d b y m e a n s of t h e i r color code. F o l l o w i n g this, the s t r a n d s of eaeh h,ad are connected to t h e m a t c h i n g wires of tim receptacles by w r a p p i n g the b a r e d end of the s t r a n d a r o u n d t h e t i n n e d end of the silver wire. A soldcrless t e r m i n a l 4 2.1 ram. (0.082 in.) inside d i a m e t e r , covered by plastic i n s u l a t i o n , f r o m which t h e t c r m i n a l l u g h a s been r(?moved, is :inserted over this t w i s t e d connection a n d c l a m p e d t i g h t l y w i t h pliers. T h e connections bet w e e n the s t r a n d s of each lead a n d the c o r r e s p o n d i n g receptacle wires are f i n a l l y t a p e d t o g e t h e r with plastic electrical tape. T h r e e seven-electrode leads will b,~ connected in t h i s w a y to the same 21-contact receptacle. I Supplied by W i n c h e s t e r Electronics, Inc., N o r w a l k , Conn. 2 Supplied by G r a s s I n s t r m n e n t Co., Cambridge, Mass. 3 Radio Electronics Television M a n u f a c t u r e r s ' Associa| loll.

4 ~qllpplicd

by A m e r i c a n P a m e o r ,

Inc., H a v e r t o w n ,

Penn.

361

RECORI)INGS

T h e receptacles are l e f t in t h e b a n d a g e t~s h)ng as the leads are l e f t w i t h i n t h e b r a i n tissue. W h e n a r e c o r d i n g is desired, t h e receptacles "(re connected to the c o r r e s p o n d i n g 21-contact m i n i a t u r e p l u g s 5 at one end of a cable which at the other end est:d~lishes eonneeti()n with a r o c t H l l g l l l a r s e h ~ c t o r 6 ill tlll'lI COllm~eted to the i n l m t of the E E G machine. W h e n a recording in tile o p e r a t i u g room is desired, C;leh

sevell-elcetrode

]olld

is

conneltte([

to

"1 ~ e v e n -

c o n t a c t m i n i a t u r e receptacle preci,ding the el)(,u~tion. Tile various leads with their reeept:~eles a n d a cable extension arc "mtochlve!l. T h i s will provide dirt, or connection with the i n p u t cable of the EE(I m a c h i n e in the o p e r a t i n g room. W h e n 13-ch~ctrode leads are used, 26 emltacL tl/ilti a t u r e receptacles a n d p l u g s arc utilized following a procedure similar to the one described for the sevenelectrode leads. F o r r e c o r d i n g s in t h e o p e r ' t t i n g room, 14-contact m i n i a t u r e receptacles a n d t d u g s m a y tie llSe(|.

SUMMARY The p r o c e d u r e s followed at the R o c h e s t e r S t a t e H o s p i t a l for n m k i n g a n d properly connectiJ~g t h e m u i r | e l e c t r o d e ]cads used in p a t i e n t s for i n t r a c e r c b r M r e c o r d i n g s have been described in this note. REFERENCES (~HATRIAN', G . E . ,

DODGE, ~1-. V . ,

JR.,

})ETERSEN,

~[.

C. a n d BIC~:F.ORD, R. G. A multiclectrode lead for intr:tecrebral recordings. ( I n press.) IIUGHFS, J. R. a n d MAZUROWSKI, J. A. E x p l o r a t o r y studies on the p a r a s a g i t t a l mesial cortex of conscious u n a n e s t h e t i z e d eats. EEG Clin. Ycurophyxiol., 1958, JO: 363. LILLY, J. C., HUGHES, J. R., ALVO~D, E. C., .]l~. :rod (}AIA(IN, T. W. B r i e f n o n i n j u r i o u s electric w,qvef o r m for s t i m u l a t i o n of t h e brain. S(:ie~tc~, 1955, 12] : 468-469. 5 Sul)p!icd by Wim.hester Eleetronic~. Inc.. Norxxalk. Conn. 6 Made by (;ilson Medical Electronics, ?dad|sen. Wi:<

Rcfcr~nec: ('HATRIAN, G. E., POLLACK, @. S. a n d PETERSEN, M. C. A procedure for p r e p a r i n g a multiek!ctrode h'ad for i n t r a c e r e b r a l recordings, EEG Clin. Neurophysiol., 1959, 11: 358-361.

O