ARACHNOID GRANULATIO N AFFECTE D B Y SUBARACHNOID HEMORRHAG E

R.P. CHOPAR D * , R.C . BRANCALHA O ** , M.H . MIRANDA-NET O *** , W. BIAZOTT O ***

SUMMARY — Th e purpos e o f thi s stud y was t o investigat e usin g ligh t microscop y th e fibro -cellular component s o f arachnoi d granulation s affecte d b y mil d an d sever e subarachnoi d he -morrage. Th e erythrocyte s wer e i n th e channel s delimitate d b y collagenou s an d elasti c bun -dles an d arachnoi d cells , showin g thei r tortuou s an d intercommunicatin g ro w fro m th e pedicl e to th e fibrou s capsule . Th e cor e portio n o f th e pedicl e an d th e cente r represente d a principa l route t o th e bul k outflo w o f cerebrospina l flui d an d erythrocytes . I n th e sever e hemorrhage , the fibrocellula r component s ar e desorganized , increasin g th e extracellula r channels . W e coul d see arachnoi d granulation s withou t erythrocytes , whic h cell s showe d bi g roun d nucleou s sug -gesting thei r transformatio n int o phagocyti c cells .

KEY WORDS : arachnoi d granulation , subarachnoi d hemorrhage , cerebrospina l fluid .

Estudo da s componente s fibroso s da s granulaçõe s aracnóide s n a presenç a d e hemorragi a sub -aracnóide.

RESUMO — Po r microscopi a óptic a fora m estudado s o s componente s fibroso s da s granulaçõe s aracnóides d e indivíduo s acometido s po r hemorragi a subaracnóid e d e tip o moderad o o u severo . Os eritrocito s estava m presente s no s canai s delimitado s po r feixe s d e fibra s elásticas , colágena s e célula s aracnóides . O s canai s tortuoso s e intercomunicante s era m observado s desd e o pedí -culo at é a cápsul a fibros a d a granulaçã o aracnóide . O principa l trajet o do s eritrocito s e d o líquido céfalo-raquidian o ocorri a n o interio r d o pedícul o e centr o d a granulaçã o aracnóide . N a hemorragia severa , o s componente s fibro-musculare s estava m desorganizado s e o s canai s extra -celulares aumentados . A presenç a d e célula s co m grande s núcleos , observad a n o materia l he -morrágico, é sugestiv a d e transformaçõe s da s célula s aracnóide s e m célula s fagocitárias , par a promover a digestã o intracelula r do s eritrocitos .

PALAVRAS-CHAVE: granulaçã o aracnóide , hemorragi a subaracnóide , líquid o cefalorra -quidiano.

Many author s hav e bee n studyin g th e cerebrospina l flui d (CSF) transpor t through arachnoi d granulation . Tw o hypothese s hav e gaine d specia l attention . The firs t accept s th e existenc e o f ope n channel s o f communicatio n between sub-aracnoid space an d superior sagittal sinus , acros s granulation , attributin g t o thi s structuce valvula r functio n 1,6,7,10,15,16,19-21,25,27,29-31. Th e second , denie s th e exis -tence o f ope n channel s o f communicatio n between subarachnoi d space an d supe-rior sagitta l sinu s an d attribute s a proces s o f filtratio n fo r th e CS F absorp-tion 2,4,11,22-24,26,28. The possibilities of existence of both mechanisms of CSF trans-port ar e also accepte d 8,9,12,13,18,32,33.

Some authors use erythrocytes as a natural tracer of CS F in the granulation affected b y subarachnoid hemorrhage. Som e o f the m 2-4,22-24 affir m tha t erythro-cytes cros s i n a n altere d for m fo r th e venou s system ; other s 1.17,25,29-31 sa y tha t erythrocytes cros s t o unaltere d for m an d som e other s sa y tha t erythrocyte s d o

* Departament o d e Anatomia , Institut o d e Ciência s Biológica s (ICB) , Universidad e d e Sã o Paulo (USP) ; * * UNIOESTE, Cascavel , Paraná ; ** * Universidad e Estadua l d e Maringá , Para -ná. Aceite : 30-março-1993 .

Dr. Renat o P . Chopar d — Departamento d e Anatomi a - Faculdad e d e Medicina , US P - Av . Dr. Arnaldo 45 5 - 01246-00 0 Sã o Paul o S P - Brasil .

not cros s 1M4 t o th e venou s system . Th e present stud y wa s undertake n to inves -tigate th e morphofunctiona l structur e o f huma n arachnoi d granulatio n affecte d by sever e an d mil d subarachnoi d hemorrhag e providin g a comparativ e analysis , and als o contributing for the informatio n on the mechanism and functional value of thes e importan t anatomica l structures .

MATERIAL AN D METHO D

The materia l was obtaine d postmorte m fro m 8 subject s o f bot h sexe s wit h ag e rangin g from 2 0 t o 6 0 years old . Thes e subject s comprise d 4 case s o f smal l meningea l vessel s ruptur e with mil d subarachnoi d hemorrhag e notice d throug h CS F analysis , an d 4 case s wit h ruptur e of aneurysm s o f basila r arter y wit h sever e subarachnoi d hemorrhage . Followin g dissectio n the piece s wer e fixe d i n 10 % formalin durin g 9 6 hours . Group s o f granulatio n wer e remove d for histologica l study , embedde d i n paraffi n an d seria l vertica l an d horizonta l section s wer e made a t ? an d 20^ m an d staine d wit h Aza n an d hematoxylin-eosin . Th e section s o f th e selec -ted area s wer e examine d wit h a Wil d M 2 0 photomicroscope .

RESULTS

Fibrous component s

In th e materia l o f th e subject s wit h mil d subarachnoi d hemorrhag e i t was observe d tha t there wer e erythrocyte s insid e collagenou s meshwor k (Fig . 1 ) i n al l extensio n o f arachnoi d granulation, particularl y i n th e cente r (Fig . 2) . I n sever e hemorrhage , th e collagenou s fiber s in th e cor e cente r o f th e granulatio n suffere d desestructuration , increasin g th e spac e i n th e channels (Fi g 3) .

Cellular component s The arachnoi d cells , wit h roun d an d pavimentou s nucleous , ar e o n fibrou s component s

and throug h thei r cytoplasmati c proces s for m channel s wit h erythrocyte s insid e organize d i n tortuous ro w i n th e cor e regio n o f th e pedicl e an d center . I n thi s sam e materia l w e ca n find granulatio n withou t erythrocytes , an d w e ca n se e cell s wit h bi g roun d nucleou s (Fig . 4) .

In sever e hemorrhag e th e collagenou s an d elasti c bundles , i n th e cente r o f arachnoi d granulation, suffe r desestructuratio n widenin g th e cannallicula r space i n th e channel s an d re -ducing th e densit y o f fibrou s components . W e ca n se e erythrocyte s agglutinatio n an d th e breaking o f th e continuit y betwee n nearb y arachnoi d cells .

COMMENTS

Fibrous components

The presenc e o f erythocyte s insid e collagenou s networ k o f th e arachnoi d granulation an d fibrou s capsul e (figs.land2 ) allow s detaile d analysi s o f th e

tortous channel s existenc e betwee n collagenou s bundle s an d undoubtedl y sho w the intercommunicatio n o f thes e channel s fro m th e pedicl e t o fibrou s capsule ; this conditio n reveal s th e permeabilit y o f thes e channels . Accordin g to th e dat a our research provided this could lead erythrocytes direc t fo r the superio r sagitta l sinus. I t i s possibl e tha t i n th e sever e hemorrhag e (fig . 3) th e presenc e o f grea t amount o f erythrocyte s provok e excessiv e increas e o f th e CS P viscosity ; thi s would difficul t th e absorptio n process accordin g t o Davso n et al. 1(>, causin g ele -vation o f subarachnoi d space pressur e wit h consequen t desestructuratio n o f col -lagenous bundles , agglutination an d désintégration o f erythrocytes , an d i t woul d block u p th e channel s an d interrup t th e drainage . Perhaps , thi s situatio n wa s found by many authors 2-4,11,14,22-24 tha t den y the passag e o f erythrocyte s o f sub -arachnoid space fo r th e superio r sagitta l sinus .

In conformit y wit h Mirand a Net o e t al. 18, th e associatio n betwee n collage -nous and elastic bundle s forms a dynamic organization tha t answer s t o differen t functional states . Unde r these condition s th e distensio n an d retraction o f elasti c bundles would provoke change i n collagenou s network , an d this woul d limi t th e excessive extensio n o f elasti c bundle s preventin g it s desestructuration .

In sever e hemorrhage , the CS P viscosity an d agglutinatio n o f erythrocyte s would difficul t th e absorptio n process, causin g elevatio n o f pressur e tha t result s in excessive distensio n o f elasti c an d collagenous bundle s unti l thei r ruptur e and desestructuration; sinc e th e arachnoi d cell s ar e fibrou s components , the y pas s through simila r process.

Cellular components Our result s revea l th e wa y trave s b y erythrocyte s int o extracellula r spac e

of arachnoi d granulation , reachin g th e fusio n regio n an d t o cluste r i n fibrou s capsule. Thi s i s a stron g indicatio n o f th e passag e o f erythrocyte s an d CSF through th e granulatio n reachin g th e venou s system , i n accor d t o othe r stud y reports 1,9,12,13,17,25,27,29-31,33.

The presenc e o f cell s wit h larg e ova l roun d nucleou s observe d i n hemor-rhage materia l (Fig . 4) coul d be relate d t o th e transformatio n o f arachnoi d cells in phagocyti c cell s tha t promov e th e intracellula r digestio n o f erythrocyte s i n arachnoid granulation 2-4,14,22-24. Nevertheless , w e do not agre e with author s that report thi s for m a s th e onl y on e fo r eliminatin g erythrocytes . W e agree wit h Yamashima 33, an d therefore w e believ e tha t th e phagocytos e an d direc t passag e of erythrocyte s from arachnoid granulation to the superio r sagittal sinu s al l toge-ther ar e responsibl e fo r CS F clearance. Anothe r poin t i s tha t th e passag e o f erythrocytes b y passiv e mechanis m throug h extracellula r spac e i s a n immediate mechanism tha t start s a s soo n a s erythrocyte s reac h th e granulation , whil e th e transformation o f arachnoi d cells int o phagocyti c cell s i s a mechanis m « a poste-riori» tha t require s time for th e cell s transformation.

The grea t concentratio n o f erythrocyte s i n th e cor e regio n o f pedicl e an d center o f granulatio n (Fig . 4) woul d sugges t a preferentia l rout e i n directio n t o the apica l regio n o f granulation , reachin g th e fusio n regio n an d las t t o th e venous system .

Conclusions

1. I n th e sever e subarachnoi d hemorrhag e occur s agglutinatio n o f erythrocyte s into arachnoi d granulation , wit h consequen t desestructuratio n o f fibrocellula r components. 2. Th e core regio n o f pedicl e an d center o f arachnoi d granulation woul d repre-sent a principa l rout e of th e bulk outflo w o f CS F and erythrocytes. 3. Th e disposition o f erythrocyte s i n line int o th e granulatio n sinc e pedicl e until fibrous capsul e shows a n architecture compatibl e with the existence o f continou s channels, formin g functiona l channel s fo r exi t o f th e CSF.

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