CA2106008A1 - Micturitional assist device - Google Patents

Abstract

Cuff electrodes (40a, 40b) are surgically implanted around S3 sacral ventral root nerve trunks (16a, 16b). The sacral ventral roots have smaller diameter nerve fibers (20a, 20b) which convey action potentials to cause detrusor activation to contract the bladder (10) and larger diameter nerve fibers (18a, 18b) which carry action potentials for causing contraction of a urethral sphincter (12) to block the flow of urine from the bladder. A current source (50) causes current pulses (52) between such electrical contacts (46, 48) and a central electrical contact (44). The current pulses have an appropriate amplitude and waveform to initiate action potentials adjacent the central contact and to block the propagation of action potential adjacent the end electrodes along the larger diameter nerve fibers (which have fewer nodes between the contacts) but not the smaller diameter nerve fibers (which have more nodes between the electrodes). In this manner, action potentials are electrically excited to propagate at least downstream on the smaller diameter nerve fibers causing contraction of the bladder. Concurrently, blocking action potentials are allowed to propagate upstream on at least the larger diameter nerve fibers, collision blocking naturally occurring action potentials propagating downstream. The transmission of action potentials downstream on the larger diameter nerve fibers is blocked by the current pulses allowing the urinary sphincter to relax.

Description

SE~-:C-~3 F~ : 2~ F~ H~P~ F~X hO, 2:~4~.~o~ P.u~

_ W09~ P~/US92101951 ~ .
210~00 RITI~N~ A~Ie~

~c~groun~ ~ the InYe~io~
The pr~ent inv~ion relate~ ~o the ~rl of sel~c~ive nerre stimulation. The in~en~ion f~nds pa~ticular applicat ion in oon;~n~tion with ~rin~tlon ~ontrol and will ~e des-ribed with part.i~ular reference ~here~o. I~ is to be appreciat~d th~t the ~nvention is also appl~cable to ~ontrol systems for fecal incontinPnce, penile erection, and other~.
~ he ~g~ns lnvQlve~ ln ~la~er, ~owel, And sexual function receive much o~ their c~ntr~ ia th~ s~cond, third, 10 an~ f~urth sacral ne~v~s (s~ S3, and ~). While one lev~i of roo-s usually pr~dominat~ for a pa~ticular ~unat~on, there ls c~nside~ble overlap. For exa~ple, ohe S3 sa~ral nerve i5 the ~nain ~timulus for both }:laddc~ ~nd :cectal wall c~ntraction, Bladder and re~tal wall both receive some oor.trol ~l~o fr~ and/o~ S2 sacral nerves. spnlnc~ers are prob~bly mainly inner~a~e~ hy 5," aIthough ~h~ ~r~thr,31 sph~.~cter ~as significant c~ntr~bu~ions from 53. Hence, th~r~ l~ di~iculty in ~pplying n~tific~l stimulus to con~ ct th~ ~ladder without con~racting t~e ~rethral c,phi:~c~er and to contr~t ~ rec~um without c~ntra~ing the anal sphincter.
The external uretnral sphlnc~er receives sti~-1lation o~ th~ saeral v~ntral roots to ca~ç~ contraotion to b~iDc~ urine flow. ~o dis~harge the bladder, in a healthy pe~ n, ~hQ ~ladd~r detr~or ~u3cle~ are contracted ~o ~xpel urinl~ simul~aneously wi~h relaxir.g the urethral sphinct~r to ' SEP -O ~ FR ;~ 25 ~.' SHRRPE FPX N~ "4:'.86~ P,O5 ! -~ WO 92/1~.~6~ PCT/US92~1951 .

2~6008 all~w th~ passage o~ ~ne urine. The contractio~ of th~
blaclder is al~io controll~d by ~h~ 6alcral ~entral root~. ~ore speclrically~ contra~tion o~ ~he bladder detru~or ~u~cles is ca~ l by ~:mall~r diameter 63 ner~ nd contrcLction of the ~ret:hr~l sphincter is controlled by larger di~m~ter S~ ner~es whic~h Are interrnixed ln the same roots.
Previously, electrical sti~ulation has been ~p~ d to contr~l the bladder an~ ~owel, ~e previou~ attempts have focl.o.ed on ~hree techniques: ~irect ~timul~tion o~ the lo d~trusor mussle~ a~tlvatlon of the det~u~or by sti~.ulat on o ~he conus ~edullaris, and acti~ation of the d~tru30r by sacral root ~r nerve sti~ulation with extensive dor~al rhiz~to~ A11 -hr~3 of t~eEIe me~hG~I~ su~f~r ~ror~ th~: 6~me pro~lem. They all çause contracticn o~ the ~la~der to ex~el U~inQ ~oncurr~ntly with aontr~c~ion of the er.ternal urethr~l sphincte~ biocking urine ~low. The rhizoto~y technique also reGul~ in the 1~ of erecti~n ~or Lhe male. I~ wo~lld ~e advantag~ous i~ ~ontr~ction OI the sphinc~er could ~8 sel~cti~ely blocked.
2C Techniques that are availabl4 :f~or blocking n~
impul~es are ~lscusse~, for example, ln ItA Technique ~or Co'lision Bloc~ of ~er~phsral ~e~vo: S~ngle ~tlmulatior.
Analysisl~, van ~en ~onert and Morti~e~, IEEE ~ransacti3ns on Bi~medic~l Engine~ring, Vol. ~ 2a, No. 5, M~y lssl, pa~es 373-378 an~ ~Generation o~ Unidirection~lly Propag~ted Action Poten~ial~ in a Periph~rAl Nerve by Bri2f s~lmu~ an ~en Honert and ~orti~er, S~ience, Vol. 20~, D6camber 1979, pages 1311~1312. w~th th~ v~n den Honer~ an~ ~ortimer tecnnlques, a n~!r~e impulse or ~o~ion pOteht' al i5 gener~t4d which ~r~ls toward th~ br~ln. ~hen the ar~ificlally generated nerve i~pulse ~eet~ motor im~pul6:~ trav~ ng fro~ th~
bral~, tne motor impulse is collision bl~ked. That is, the a~ti~ ially ~n~ratod action pote~ti~L1 a~hc.el~ thP ~ tor ~c~ n potential. I~ Ohe wer~ to apply the ~an den Hone~t , ~ :

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~EP-:0-33 FR: '.! 26 F~v ~H~R~E F~X NO. 2'.624'!~86 P.06 WO 9~ 366 PC:r~usg2~t~s : ' _ 3 and Mortlmer ~echniques, it could be used to caUSe con~Urrent relaxaticn of bot~ the ~ dde~ c~nt~lc~in~ muscle . ar~d the Ure1:~al spnincter. Agaln, the ~ladder contracting ~u~clos and tha urot~r~l ~phin~ter ~:re op2ra~1~g at cro~s purposes.
h teshni~ue ~or fa~igu~ resi~ant flexin~ of ~sclo~ of 13bc,r~tory ~ni~l~, particularly rellne ~lnd leg m~scles~ is desçribed in ~A Method for Attai~ing Natu~al Rhor~itment Ord~!r ~n ~rtificially ActlVated ~USCl~SI~ Zi-Ping Fang and ~.
~honlas ~rti~er, X~E Nin~h Annu~l ConfeEe~C~ D r the lG ~ngi.neering in ~ed~cine and Biology socie-ty, 1987. By way of backgr~und, applyi~g a~ ele~ cnl potenti~l ~or current~ o~
an 3ppropriate amplitude along the len~th o~ ~ nerv2 cau~es an acti~n ~ot~ntlal t~ propag~t~ in ~oth directiDr~ rom ~he s~lmulus site. In th~ van deh Honert and ~ortimer technique, a c~un~Q~-c~rre~t 19 ~pplied ~n ~nly one sl~e of the electrode, Which Counter-curren~ 's of a su~fici~nt ~agnitude tc ~lock prop~gation or the ~tion po~ential in that dirsctior. fro~ the excitatioh sit~. In ~h~ ~ng and ~orti~er ~ech~iq~e, the coun~er-curren~ is regulated to block lar~e diam~ter nerve Siber~ while p~r~i _ing the actio~ potenti~ls on th~ small dla~eter fibers to propagate pas~ the end c~ the eleccrod2. ~h~ ac~ion po~en~ propa~ti~g on ~he unbll~c~ed small dia~eter fibers ~ause ~lexing af the hind le~
~usc:L~ with propo~tion~t~ly les~ force an~ less fatigue.
The present in~ention contemplates a now and i~proved ~eGhniq~e for dlfferentlatlng action po~entials dest.ined ~or different organs.

Bum~ry o~ Inve~ n In accordance w~h one a~pect o~ the ~resent l~verltion, a t~ohnique i3 proYided ~r di~ferent~atlng a~on~
actic,n poten~ials ~ravellin~ alon~ a com~on nervQ bn.Si~l~
whic~, ar~ destined fo~ di~fexent end organs.
. I~ accordance with o~e aspect o ~he pracant inver.~ion, ~tion p~tentials are genera~e~ on nerve fibers :- - . ~
,, ~

S~-'0-93 F~ ? ~ SH~.RP~: F~X IIO. 2:824''~o P,07 - ~ WO 92/1~;366 PC~r/US9~ t 6~8 co~neo~d with botn the f irE;t ~nd s cond end organs . The acti~n ~otential~ ~rav~llin~ ~O onç of the ~nd ~r~ans ~re ~l o -ke~, In acc~d~nc~ wl~h elno~ ~r ~peot o the present invl~ntlon, ~n electrode is plar~ed aro~ind ~he n~rve ~undle.
Ele,~trical ~ur~ont~ are app'~ i~d to the electro~e sU~h th~t ~ct:Lon po~ential~ ar~ ~enerate~ ~.nd ~craYel fro~ ~he el~c~rod~
on ~ e nerv~ f iber~ ns~ d wi~h a selectaPle on~ of t~e end organs.
l~ In accord~nce wl~h ~nother asp~ct o~ the pre~nt 1 ~v~ntion, 2 lnet~od. ~f cc~ntr~ in~ ~laddar dra,ni~g i~
p~ dcd. Action po~en~ials are initia~d on ~ ner~re bl;r.dle ~hich ln~lu~a~ nerVe f i~e~5 ~ lr.~ ~ do~ru~r mu~ole~ ~sld to t.he ure~h~al spl~lncter. ~.ction pot:en~ials ar~ caus~d to 15 emar~a~e ~ro~ ~he ~l~ctrod~ up~4r~m ~o~rd ~he ~pin~l cord on at least t~e nerve fibers dest~ned for the urethral sphincte~
muscle for ~olli~ion ~locking 40~ior; potentials cor~ing from ~e splnal cor~ such that the urethra' iphincter is al1 o~,d ~o relax. C~ urr~ntly, ~c~ion pc~ntlals are produced ~0 flowing downstrea~ on th~ nerv~ ers c~nnect4d w'th ~ch~
d4truso~ ~uscle~ but not on the ner~e fibe~S connected wi~h t~.e uré~hral sphinct~r.
One advantaye c~ the pre~ent ir,~ention is that i-enables ac~ion potentials tc, bo o~at~d ~loc~ ely ~n 2s pcr~iohs ~f a nerv~ ~undle.
Another a~v~t~gq of the p-e~en~ in~renti~n is ~at ~ ~ ~.nable~ action po~e~ials to be trar.smitte~ along .~
sukg~ou~ of n~r~ ib~r~ with~n ~ ~ndle, which ~u~group is conne~ted Wit~; a ~irs~ end ~rgan or m~sc'~a to th~ ~xcl~l~ior Gf~ n~r.~e ~iber~ assb~at:ed Wlth anotrler en~ organ.
Another advan~ag~ of the p~4~3rlt inv~rtiGr~ hel~
it enables ~he bladd~r to be drained without operating ~e~rllSor ahd sphln~ter muscles a'c cro3~ purposee.
S~ ill rurther advar,taqes of ~he pre3ent in~irention will beco~e apparent fr~m thsa followi~g d~t~ d descriptlOn.

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SEP-'0-93 FR' 11 ~7 FRV SU~RP~ F~X NO. 2 6~4.:666 P.Oa WO 92/1i366 ~ 9~019~1 2 ~ 0 ~

ri~ Deg~::rlptlot~ o~ the Dr~wln~
The in~r~ntion ~ay take ln form in ~:~rlou5 parts 2~n;1 ~rr~.nge~en~s of parts, and in variou~ skeps and arrangement~
of steps. ~e dra~Lng~: a~e only fo~ p~pos~3s o~ lllustrating ~he invention and ar~ not ~o be corlstrue~ s limiting it.-FICU~E 1 i ~ a ~i~gra~mna~ic illustration illustra~in~ ~he placement of elec~.~odes f~r c:on~rol of the bladd~ at~d othor or~ns i FIGUP~E 2 ~S ~ pers~e~tiv~ V14W ~ str~' in.
lo ~ ~ctrod~3 ac~n~rtlct~ on ~
:~IGURE 3 i~ a dQtail~d, ~ro~ cc~i~nal illus~tion oS or~e o~ the electrodes of ~IG~JRE l; and, ~IGURE 4 is a ~r~phi~ ~epre~entn~ion of blocXing ~hre;,hc~ld versus ~i~er diameter.

1~ De~alled De~ripl:lo~ or ~he Pr~f~ im~
Wit:h r~f~renc~e to ~IGURE 1, v~3:ious ~ower abdominal or~ans are corltr;~lled by action poter~t;ials that tra~r~l . ron~
the brain, through the :spinal corâ, an~ through sacral ventl al roots to the e~d org2n~. ~or~ ~pc~cif~cally, acti~n ~0 po~entiA1~ tr vel~ng along the S2~ S3, and S4 ~acral ventral roots control penile ~ection, ~l~dder evncuatior., and d~ ~c.atlon .
Loo~cing ~irct to bl~dder evacuation, the bl~e~ lV
and uret~r~l sphinc~r ~2 a~ o~troll~d by ~ction potentials traveling ~rom th~ apihal cord 1~5 prir~arlly on z left-~igh~
symme~ric pair o~ 53 s~ral ven~ral roots lfia, l~b.
~he vent~al roots l 6a, 161:~ are bundle~ o~ nervP
~bers includin~ larger dl~m~t~ ~Lb~r~ a~a, lab ~nd sm~ller diameter fiber~ a~a, 25b. The l~rg~r diameter fibers Connect 3 0 betwaen the spirlal c~rd 1~ and ~h~ ~ethr~l sphlncter 1~ .
As~ion potentials ~lowing ~long the larger diameter ne~t~
~iber~ caus~ th~ ur~thral :~phin~ter ~v ~ontract, ~locXing thl3 oUtlet from the bla~der 10. In a healthy persc~r~, th~ ~r~in ~EP-:0-83 F~ ' 28 ~ .qRPE F~X ~O. 2:624 ;~8~ a . W09~115.3~6 PCT~US92/01~1 2 1 ~

oauC.e~ a regular stre~ or act1on poten~ial~ fl owin~ along the larger di~m~cer fiber~ 18~, ~sb ~o keep ~he ur~th~al ~phin~ter ~o~traCte~, When the bladder is to be e~pti~d, the flo~ o~ action p~tential~ thro~gh 'he larger di~meter n~e ~ber~ is stop~ed ailowin~ ~he sphlncter to relax.
~h~ ~all~r nerv~ fibers 20~, aob connect bet~een ~he ~-pinal cord and th~ ~la~der, ~articularly the detr~s~r le l~y~r whi~h cau~es th~ ~adder to c~tra~t. I~ a nealthy person, khe s~al~er diameter ~ibers usually car~y n~
acti~ p~enti~ls until the per~on desires ~,o e~a~uate 'he blad~er. To evacUate the bladder, action pot~nti~ r~ ~ant al~3 the sm~ller dia~eter ne~ve fibers 20a, 20~ concurrer.tly with the sto~ping of sending ac:~ion p~t~antiala along the l~rg,~r dia~!e~er n~rve ~ibers 18a, i8b. This causes the uret]l~al s~hlnc~er ~o rblax and allow ~he ~ladder ~ let tG
o~en ~oncurren~ly with detrusor contracting to expel urine.
Analog~u~ly, th~ S~ ~n~ S; s~cr~l v~nt~a' roots i~cl~de ~undl~s ~2a, 2l~ 3f large diameter nerve ~i~e~ Z4a, 2~b and ~ r dia~e~r nerv~ ~ibe~s ~a, z6b. ~h~ l~rge z~ diam~3ter nerve fibers control an anal s~hin~ter muscl4 2~ and thQ ~all ~ etcr f~ers 26a, 2~ con~rol mus~les which c~us~ con~raction around the rectal canal ~0. ~facation is acco~plished ~y concurrentl~ ~erminatlng tha supply of action pc~erltials to the sphinctor ~8 allowing lt to rel~x whil~
~Ym~lier âia~eter n~rve ~ibers 26~, 26b c~y action poterltials to th~ mu6cl~ whloh CAU3C the rect~ al ~0 ~o ccntract.
~nal3go~1y~ the S2 ven~r~l root~ ln~lu~e ~u~dles ~f nerve ~i~ers 32a, 32b for controllin~ penilo ~ction.
Spi~l cQrd ln~uries and various other ~edieal sor.dit'~ns c~n cau~e a 105~ ~f ~on~rol o~ ~he~ org~n~. Tc rein~ti~ute t~ls control, a cufe electr~de ~0, is mounted surrounding each ~ r ~ha ~pprcpriata ~c. al ~entxal roots.
T~.e C~f~ elec~rodes are G~nrigu-e~ r;:r artificially exci~ing :

$~.?-'~0-33 FR: I'. 2~ F~Y SH~RPE F~X N0. 2~624"66~ D, 0 WO ~2/t~3~6 2 ~ ~ ~ O ~ v~9z~ol9~l ~ 7 ~
a~t:Lon poten~ s on the ~mall ~iameter ~Rrve ~ihers w~ile blocXin~ n~urall~ oc:~urring ~ction potenti~ rom travellng do~n~t:r~anl on the larger ~ia~neter ne~ves. SE~eclficaliY, eleotrodes 40a . 40b arf~ implanted 8urroundin~ the S3 ~oots 5~.6, l~b l:O exci e ac~ion potentials which ~ctivat* th~
detrusor whil~ blooking the trans~ission of action potentials on large di,~mP~er ne~ve fibe~s 1~ b to allow the sp~incter 1~ to relax. Analogou~ly, electrodes 40~, ~oa are 3urg~ally implanted ,~round the S~, roo~ 22a, 1~Elec~rod~3a ~Oe, ~o~ a~ lmplante~ around th~ S~ r~t~ to control penile erection.
With partlcular reXerenc2 ~o 1~I~U~ 3S 2 anc~ 3, RE~Ch of the electrode.s is ~ tripo~ ~r el~:t~o~;le. P~e~era~ly~ the ele~xr~de is a self-cu~ling spiral alçc~rode ~hat i~ }~ia~ed 15to c~lrl around t~e ~eleate~ t analogs:u~ co the electro~e illustra~ed in U.S. P~tent No. 4,602,62~. ~h~ cu~ elec~rode 40 ha~ ~n in~ulator layer ~2 ~ha~ i s biased to curl around the ~ssociated ~.erve root. In i~s cc~ d confiqu~ation, the layer 42 haG an internal dlametar ve~r close to that of the 20dlam~ter o~ th~ nerve root. For axampl~ c~ nerve rcot or trunk of ab~u~ l.cl ~m ~lameter, ~n inn~r cuff diameter of l.o s pre~erred . Preferably, t~e cuff wraps l. 3 - 2 ti~nes ~r~uncl ~he ner~e to pre~ en~ current leaXage while havi~g sufficiently faw wrap~ t~at it i~ s~lll easy to lnstall.
~5The ~u~ electrode ir.c ludes a central s~ lating conta~t ~ n up~tre~m end c~ntact 4 6 toward the spinal cord, and a downstrea~ ~nd colltac~ ~.8 towarcl the controlled organ. ~ac~h c~n~act sur~ac~ i5 de~in~d ~y a ~hin, ~pre~l~rably about 0~5 ~ idci ~trip o~ oonducti~e ~ilm, ~.g~
3~plati)~m, irid~um oxl~e, titanium oxide, or the like. In thQ
coilec~ configur2~ion, e~ch g~ip ~orzn~ an ~nllular electrical contac:t surrounding the nerve root.
The spacing ~tween t}.~ ahnular electrode rings is 5el~ct.ed in accordance wi~h t:he relati-~e siz~ f the ne~e ~, . . , .; :

SEP-'.0-93 FR; !! 29 F~v SHR?~PE F~ NO. 2l624~66 p .

WO 9~ ~/US~ 951 . ~.

fi~rs. The spacing is ~elected ~uch that there ar~3 about 4 nodes ~ r tha l~rg~r dia~etsr :~lbers betwoen each palr o~
ele~rode rin~s. The ~.nterno~.al length i~ g~nerally a~ou~
100 tim~ th~ er dinme~cr. ~or exa~ple, a zo ~Lm diame~er ~ibex h~s ~n inter"ode l~ngth of a~out 2 mm. Anz~l~gou~ly, a 10 ~ iber has ~n internodal length or about 1 mm. In th~
preferred embodiment, ~he cuf4 ~lectrode ic a~out 20 ~UT long wi~h the ~lectro~ s spacQd about 8 m~n apart. ActiDn poten~ials ~r~ ,gate fr~-m no~a ~o nod~. Wheh A nod~ iis 0 ~nome~thrlly depolarlzea with an electric21 stimulus, an a~ti,~n Doten~ial ~t~rts propagating bC)th up~r~n~n and down.~e~m" ~en a node ~ ~; subjec~ to a su~fi~ient hyp~:~polarlza~ n, it cannot pas~ an ~otion pote~tial and the action potential dies out or is blo~::ked.
~n th~ pre~erred ~ di~ent, a cu~rE~nt source ~0 appl:le~ a ;~[uasi-tr~pezoidal shapad stimulus ~urr~nt pl~i5C~ 5~;
betwo~n the a~ntrr~l elec~rical c:ontact ~ and the two ~nd contaots 46 and 48 . ~he pu1s63 has a suffiaient ~nFl ' tude at it~: e~ing ~dge to ~epolarlze tne nodes of bot~ l~rge and 2 0 smal], diameter nen~e fibers (depolari2~ from the resti;~g 0tAte: by nbou~ -25 mY ~Cross the ma~braneD o~ the nod~s) ~nd initi ate action potentlal~ propa~atir~g ~idlr~c~i4n~
th~re~lang The ourrent pulse has a ~lat plat~au S~ on the order of 300-5D0 ,~5 that hypQrpolarizes ~he node~; of the nerve rlbers in the region of elec~rodes ~laced at the ends ~f th~ cl:ff, 4~, ~B. ~e ~mpli'cude c~ the curr~nt pulse is sele~ted such that ~ hyper~olarlziny ;~otential c)f ab~ut 55 mv rn~re ne~tive th~n the res~ ing po~entlal i~ ~rea'ced across the n~des cf tha lar~er dia~.at~r ~er~Je fibe~ on ~rhioh aotion potenti~l5 ~re to b~ ~loc~e~l. A s~naller magnitu~e potentlal ~ s G~eated acroe~s the n~de~ ~ th~ all~r diamet~r ~er~re fibe- on whl~n ac~ion potentials ~ill be permi~ted to p~ss.
It will ~2 notQd that 1~66 electrlc~l c~r~nt is reqllired to ' low@r the putential at the nodes of t~.e laryer diameter fiber ' than at tho ~c~de~ o t:he smalle~ ~3meter riber ~zc~use , ~ ~
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:. : ; ; .
:.. ...

~EP-' 0_9? FR '' ~0 F~V SH~RPE F~X .~iO. 2 62~ 6î~ ?. :~
wo 92/t~36~ 2 ~ /VS~2t~l9~1 - _ 9 _ spacing nodas i6 g~eater for large di~mete~ nerve ~ibers than small di~ q~er ~ibers. The a~npli~udo of the pl~teau ls ad j~lsta~ o 6eloct which ~lla~e~ers of nerV~ f ibers ~111 be 21yperpolari~ed to a 3~lockin~ l~v~l. R~ ing ~he pl~te~il am~1 itud~ in~rc;!lses the hype~polarization t~ blo~k pro~re~sively S~naller dianlater nerve ribers. An ~xp~ner~ti~lly d~cayi~g ~ai 1 ~6 p~es~ents the anodal b~çaak pheno~nenon. Variabl~a r~ci~or elem~nts 5~ and ~0 are ihclude~ create an asymmetrical current di~:tribu' ion ~h~t woull perlnit act~c~n potenti~l~ to ~e bloc~ced in one direc~ion ~Ut h3t ~nb other (e. g. allowed to pas~ in the upst~a~
dire~:tion but ~loakod f~m travelling dowr~stream ~t the dc~wn!itream electro~e because ~he cuxran~ i~ high~r at ~ne downstream ~l~atrode.
FIGURE 4 i llustrate~ th~ r~lation3~1p betwPen the nerv~ f ib~3r d i~me~r and ~he r~ nimum current frcm tn~
bloc~ g current ~ou:~ce ~ n~c~æ~ry to block ~he movement ol ~cticn po~cen~lals Ln the ner~te ~ bers with dlf~er~nt dia~meters. ~or exampl~, a blocking curren~ Or a~out 0.325 ~r~
block~ I he rlow of action potentials in ne~e ib~r~ naYing a diarr,eter o~ a~out 10 ~m e3r larger. Analogously, ~IGURE 4 descrlb~s the ~lo~king current tc~ upplied ~or ~tll~r diameters bQtween which one ~y r*ish to di3crimin~te.
In the pref er~d em~adim~nt, thc ~xcitati~n pulse ~5 5~ ~ro~ current source 5~ }las z~ ~ufficient magni~dQ to ~Xcite action potentisl in n~rve~ of all sizes present i-.~ the b~nd 1~ G~ roo~. As with the ~locking potentia~, the a~o~nt cu~rent neces~ary ~o ~xoit~ tion poten~lals is higher in ~m~lle.r dla~e~er fi~er~ than irA 1 arger dia~2~ter fi~ers.
Thlls, by aporopriat~l~ sizihg the eX~itation c~lrreht ~ulse~
a~~ar. porentials ~an be selecti~ely g~n~rated ~nly in ~rve flber~ gr6~at~ th~n ~I selected, cerrespGndir.g diameter. ~hi~
~e~hnlque may ~ind apPlication in ~ndir~g 3ign~Ll3 unly to ~ne ur~thral E:phincter ~O contract t~e sphincter whils al' ~wing .

S~-P - Q-q~ FR: I 3~ SH~RDE F:iX ~0. ~ v tj ~ p W~ 9~ JS92101~1 21~0~8 -- lo --the bladde~ ~etru~o~ mu~cl~ relAx wh~n ~hP bladdor ls no~
to ~ emptle~, ~lra4trode~ 4GC, ~Od on the 54 ver~tral r~ot are conrrolied analogous~.y to cau5e a~ion p~4ntiala ~n th~
sr~ ;;r n~r~e ~ibcr6 ~ the appro~riat~ di~meter ~ or e,Cciti.~lg ~h~ ron~acti~g musculature while b' oc~ing action }:oten~ial3 o;~ ~he lar~r diame~er nerlJe fibers to relax t~;e external ~h~nct~r to c~u5e defecaticn. El aotr~des ~4O ~ 4~ are cont;-~le~ t~ r~lax ar~erial control ~nus~l~s.
This tehniqua r~y be used to ~iff~ntlate ~m.ong orher. vrgans ar ~nuscle groups. The inven~ion may ind ap~l:.cation in col~junctic)r. with ~ther ~oto~ or sensory ner~6!s. For ~xample, by FassinS~ ac~ion po-en~ials on diff~rent s~z~ nerv~ fibe~s o~ the auditory ner~,0, di~ferer~t tones _an ~e c,o~murlicated to the kra.. n. Anal~s~ou~ly, o~ns~
i n~rma~ion 2~ay ~ ir.put inta the br~ln by select~vel~i exciting a.,~ion potentials in other a~ar~nt nar~ fibe~s of c t~d ~iar~et~r ranges .
The in~ention h~s ~een de~cri~d with re~erence to 2c ~he ~r~ re~ e~odiment. ~b~io~:sly, ~difications and ~lterationa will occur ~o ot:n~r6 upon readlrlg ar,d un~erstz~nding ~ne precedl~g ~e~ailed des~ri~ion. It is ~ nten~ed that t~e invention be c~s~rued as inclu~lng ~ll suc:h ~l~era~cior.5 and ~c)di~ication~ insofar as they - ~Ime 2$ withLn the ~:ope o~ th~ np~ended ~laiI!ls or the equivalents there~

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Claims (13)

Having thus described the preferred embodiment, the invention is now claimed to be:

1. A method of controlling bladder discharge in which detrusor activation for contracting the bladder is controlled by action potentials passing along smaller diameter nerve fibers of a sacral root and in which contraction of a urethral sphincter for closing an outlet from the bladder is caused by action potentials passing along larger diameter nerve fibers of the sacral root, the method of controlling bladder discharge comprising:
electrically exciting action potentials on at least the smaller diameter nerve fibers, whereby the detrusor is activated to cause contraction of the bladder;
concurrently blocking action potentials from passing along the larger diameter nerve fibers, whereby the urethral sphincter is permitted to relax.

2. The method as set forth in claim 1 wherein the step of exciting action potentials includes exciting action potentials on both the larger and smaller diameter nerve fibers concurrently at an excitation location;
and the blocking step includes blocking action potentials on the larger diameter nerve fibers propagating downstream from the excitation location.

3. The method as set forth in claim 2 wherein the action potential exciting step further includes:
exciting action potentials that propagate both upstream and downstream from the excitation location on both the larger and smaller diameter nerve fibers such that the excited action potentials traveling upstream collision block any naturally occurring action potentials travelling downstream from the spinal cord and those travelling downstream, from the excitation location, on the larger diameter nerve fibers are blocked at the downstream electrode.

4. The method as set forth in claim 2 further including:
surgically implanting around the sacral root a cuff electrode which has a central electrical contact, an upstream end electrical contact upstream from the central contact, and a downstream end electrical contact downstream from the central contact toward the detrusor and the urinary sphincter;
wherein the excitation step includes applying a stimulus current pulse between the end and central electrical contacts and the blocking step includes holding the applied stimulus pulse long enough to block passage of the action potential on larger fibers at the end contacts.

5. The method as set forth in claim 4 further including selectively adjusting an amplitude of the current pulse for selectively adjusting a diameter of nerve fibers along which the propagation of action potentials is blocked.

6. The method as set forth in claim 5 further including:
implanting a second electrode on another sacral root which has larger diameter nerve fibers connected with an anal sphincter muscle and smaller diameter fibers connected with musculature for contracting a rectal canal during defecation, the second electrode having at least a second central electrical contact, a second upstream end electrical contact, and a second downstream end electrical contact;
applying an electrical current pulse between the end and central electrical contacts which excites action potentials in both the large and small diameter nerve fibers of the another sacral root and which selectively block action potentials on the larger diameter nerve fibers of the another sacral root, whereby the blocking of action potentials on the larger diameter nerve fibers causes the anal sphincter muscle to relax and action potentials passing along the smaller diameter nerve fibers cause contraction of the rectal canal.

7. The method as set forth in claim 6 further including:
implanting a third electrode on a third sacral root which controls penile erections, the third electrode including at least two electrical contacts;
selectively applying a current pulse between the two electrical contacts to induce action potentials to propagate along the third sacral root, which induced action potentials cause a penile erection.

8. The method of selectively, concurrently exciting and block the the excitation of first and second end organs which are controlled by small and large diameter nerve fibers, respectively, of a common nerve trunk, the method comprising:
electrically exciting action potentials on at least the smaller diameter nerve fibers;
concurrently blocking action potentials from passing along the larger diameter nerve fibers toward the second end organ.

9. The method as set forth in claim 8 wherein the step of electrically exciting action potentials includes exciting action potentials on both the larger and smaller diameter nerve fibers concurrently at an excitation location; and the blocking step includes blocking action potentials on only the larger diameter nerve fibers from propagating downstream from the excitation location.

10. The method as set forth in claim 9 wherein the action potential exciting step further includes exciting action potentials that propagate both upstream and downstream on both the large and small diameter nerve fibers such that the electrically excited action potentials traveling upstream collision block naturally occurring action potentials travelling downstream from the spinal cord and those travelling downstream on the larger diameter nerve fibers are blocking at the downstream electrode.

11. The method as set forth in claim 9 further including:
surgically implanting a cuff electrode around the nerve trunk which electrode has a central electrical contact, an upstream and electrical contact upstream from the central contact, and a downstream end electrical contact;
wherein the excitation step includes applying a current pulse between the end contacts and central electrical contacts and the blocking step includes continuing to apply current pulse between the end contacts and central electrical contacts for a sufficient duration to hold internodes of the large diameter nerve fibers hyperpolarized until all action potentials initiated on the larger diameter nerve fibers by initially applying the current pulse are blocked.

12. The method as set forth in claim 11 further including selectively adjusting an amplitude of the current pulse for selectively adjusting a diameter of nerve fibers along which the propagation of action potentials is blocked.

13. An electrical system for selectively generating action potentials in smaller diameter nerve fibers of a common nerve trunk which smaller diameter fibers control a first organ and suppressing action potentials in large diameter nerve fibers of the nerve trunk which control a second organ, the electrical system comprising:
a cuff electrode which has a central electrical contact, an upstream end electrical contact, and a downstream end electrical contact, the cuff electrode being implantable in a tubular configuration surrounding the common nerve trunk with the upstream electrode located upstream from the central electrode and the downstream electrode located downstream toward the first and second organs from the central electrode;
a current source connected between the end electrical connectors and the central electrical connector for selectively applying guasi-trapezoidal shaped current pulses having a generally flat plateau and an exponentially decaying tail, which have an amplitude which initiates action potentials on the larger and smaller diameter nerve fibers adjacent the central electrode and which blocks the propagation of action potentials on the larger diameter nerve fibers adjacent at least the downstream electrode without blocking the action potential on the smaller diameter nerve fibers.