Originalarbeiten - Ar ticles 177
Arachnoid cysts of the middle cra nial fossa K. von Wild Neurochirurgische Abte ilung Clemenshos pttal. Akadem isches Lehrkr anke nhaus der westr. wühefms-unrversüät Münster
In 18 cas es of temporal arachnoid cysts the etiology. clinical a nd radiographie ündtngs. surgical treat ment. and outcome are reviewed . Cysts of the middle erentel fossa are susceptible to trauma, which may cause bleeding either Into the cyst or lnto the subdural space. er or MRI sean s are dta gnosdc in arachnoid cysts . In cases ofintracranial mas s lesion with dis placem ent of th e midline str uctures end increas ing [e p, osteoplastic craniotomy ts performed and the medial wa ll of tbe cyst is resected down to the tentorial notch . with opening tnto the basal ciste rns . Ther e were 00 operative or postoperative complicat ions in 18 consecutive cas es. However, one boy required a cysto peritoneal shunt 3 months la ter as a result of hydrocephalus following subdural hematoma a nd two other pati ents were also subsequently shunted. Asymptomatic a raeh noid cysts are disoussed with the respect to brain function and potential risks.
Key-words Arac hnoid cyst s - Subdura l hematoma Hydr ocephalus - Peritoneal shunt - Microsurgica l tech nique - Congemtal Jestons
Introdu cnon Although recent studies ha ve evaluated new concepts of the pathogenesis. anatomieal ultrastructure, clinioal an d radiclogical manifestations of intr aarachnoid cysts, as the y are called today, the re ts an ongotng debate a s to the cho iee of their proper surgi cal treatment in re spect to the final outcome of patients in the pedtatric and ad ult age group (5, 8, 10, 12,1 5, 16. 21, 23). Since the ad vent of cranial com puterized tomography (CT). num erou s case reports have been presented. We are in a greement with most of the se a uthors that these lesion s are much more common the n previously rea lized when they are dtagnosed by chance being asym pto mati c before. According to Robinson (19, 20) arachnoid cysts account for ahout 1 % of all atra umatic intracranial mass lestons. Most of the cysts become symptomatic in ea rly ch ildhood in so far as
Neurochirurgia 35 (1992) t 77- 182 © Georg Thleme Verla g. Stuugart - Npw York
Arac hnoidalzyste n de r mittl e ren Schädelgru be Die derzeitigen diagnostisc hen und neu roch irurgischen Beha ndlungsmögliehkeiten von temp oralen Arac hnoidalzysten werden vor dem Hintergrund gesicherter pathologisch-anatomis cher Kenntnisse an typischen Beispiele n von 3 Kind ern und 15 Erwa ch senen a ufgezeigt. Hierbei verd ient Beachtung, daß diese Zysten, die etw a die Hä lfte aller intrak ra niellen Arac hnoidalzysten ausmachen, durch lan gsame Größenzunahme Ursa che lokaler Hirndruckzeichen und von Liquorzt rkulationsstörungen sein könn en. Besonders bei Kind ern besteht die Gefahr subduraler Blutungskomplikationen nach leichten Schädelhirn verletz ungen und die Möglichkeit von zerebralen Kr ampfanfällen. Schließ lich bewirken die Zyste n eine Entwicklungshemmung der verlagert en und komprimiert en Hirnlap penstru ktu ren. die sieh nach erfolgreicher Entlastun g wieder a usdehnen. Die Vorteile der mikrochirurgischen Zyst enwandresektion mit Wiederherstellung einer freien basale n Uquorzirkulation sowie die Möglichkeite n eines ventriku lo- oder zysto-peritoneale n Shunts wer den aufgrund eigener Erfahrungen und unte r Berücksi chtigung der Literatur diskuti er t.
60 % to 90 % of pe uents in mixed sories have been shown to be in the pediatric age group (I , 2, 8, 9, 14- 17). The dis tribution of arachnoid cysts in two hundred and eight collected cases of Rengachary et al. (17) was as follows . Sylvian fissure, 49 %; cerebellopo ntine angle, 11 %; supra-collicula r a rea , 10 %; the vermts. 9 %; sella r and suprasellar area. 9 %; interhemispheric fissure , 5 %; cerebral convexity, 4 %; the d ival and interpeduncular a rea. 3 % . This paper will deal exclusively with cysts ofthe mlddle cranial fossa since they consütute abo ut one ha lf of all cases and a re of major neurosur gtcal interest on account of malformatio n of the base of the skull and fronto-tempora l bone, progressive hydrocephalus syndrome , epilepsy, and are an im porta nt cause of associated hemorrhagic comp lications after minor head trauma (1, 4, 5 - 9, 11-13, 17, 18,27).
Pathology Morpho logical decades have elucidated the anato mieal ultra structure of were described for the first
studies during the last two pa thogenesis as weil as the intraarachno id cysts , which tim e by Bright (3) in 183 1.
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Sum m ary
llowever, the cause of the a rachnoid eysts in generar remains still controverstal. They are classlfled today Into two groups: - first: ccngenita l ma lform ations tptgs. 1- 8) (4.8. 11, 17 20 .2 2,25) .
- second . resulting from lnfla mmatlon , herncrrhage. tra uma , tumor (1 . 12, 24). Distin ct from these intra ar a chnoid eysts the middle -fossa pitholes and the tnt radiploic a raehnoid cysts are different pa thogenetic enuues (26) . arid are not discussed he re . The historieal rovlew shows tha t ara chnold cysts ha ve been given a vartety of designa tions, reflecting differe nt pathogenetie fac tors, for insta nce: ehronie cystic arachnoiditis. meningitis serosa ctrc umsc rtpta. eh re nie a rac hnciditis. cere bral pseudotumur, leptomemngaal cyst, or simply pnmary oth erwise idio pathic arachno id cyst (24). There is clear cvlden ce that som e arachnoid cysts do commun icate with the suba raehnoid space. This is bea utifully demonstrated by isotope cistern ogra phy end still better today wit h cont rast me dium CT ctsternog ra ph y (9) (Figs. 2 - 4). Aeeor din g to these functional studie s we call the m communicating or noncommunieating arachnoid cysts. These cysts have to be dist ingu ished from morphologica l findings like arachnotd diverüculum, ara chnoid hernia, aru chnold pouch . internalmeningoeele, and arachnoidoceie (18).
Starkman et al. (24) have demonstrated for the first tim e, by evalua ting histologica l deta ils. dtfferences in the a natomieal relationships of the idiopathic eysts from those following inflamma tory or irritative eon ditions . Therefore th ey sug gested that these pr imary eysts originate from anomalous developmental splitt ing of the araehn oid me mbrane as they are enveloped by the leptom eni nges and related to the ctste rns and the subarae hnoid spaee (Figs. 3.
K.
VOll
Wild
61. 'IoRengachary and Watanabe (17, 18) the eredit is principally du e that they were a ble to demonstrate wit h light and eleetron mtcroscopic Iindings the splitting ofthe araehnold membrane to enclose the cyst, wh ile the pia ma ter rema ins as aseparate Inta ct membra ne (Fig. 7). Moreover the cyst wa ll was rein forced with a den se collage nous layer in respo nse to high intraeystie prcssure. whic h may be suffieient 10 ca use erosion a nd expa nsion of the ealvarium. Th us. intr aarachnoid cysts are a develo pme ntal a noma ly of the subarachnoid ciste rns in the developing embryo causing a minor aberratio n in the CSF flow with in the subarac hnoid space , and resulting in an increasing divertic ulum wit hin the araehnoid me mbrane. This is why these cysts oceur nearly always in relation to an su baraehnoid ctstern . approximately half of them Involvi ng the Sylvian fissure (Figs. 1,4.6.7). Like lnte rhernispherlc cysts the Sylvia n fissu re arachnoid eysts ten d to become very large (Figs. 5. 6 ). The inte rmittently communieating type of cyst (Figs. 2. 3) may expand by progressive accumulation ofCS F secreted through cells of the cyst wall rather than by osmotically induced filtratio n or uni -direetional CSF Ilow - the latter was called "ball-valve tr a pping " by Smuh an d Smith (1976) . This mechanismus has to be ta ken into aecount wh en shunti ng procedere and resection of the cyst wa Uare discussed. The contained fluid is usua lly clear and eolorless. If the protei n content is higher than CSF. this ma y be the residue of an intracystic bemor rhage. The latter h as bee n reported by us and others even a fte r min or head tra uma , when acute or ehronie su bdural hemorrhage oecur in combination with intraarachnoid eysts mostly of the Sylvtan region (1, 5, 27). As already menuoned arachnoi d eyst of th e middle fossa themselves re present compressive elements ca using both loeal bulging and thinning of the temporal
Fig. 1 Cl scans 01 bilateral intraarachnoid
cvsts 01 the middle cranarrossa {l a, b1 in a 24 years oId man (HD 051 1641who was admitted because 01 beadaches arid ecaectc fits with tocar spike eno wave electrical octivity over the left !rontotemporal region. EpidurallCP measurement was in normal renge. Microsurgical ooeo ing 01 theleft cyst with cecorcresscn Uarge black errowl 01 the temporal lobe tsmeu black arrow, I cd). Chronic subdural hematoma frontal light due to oeccrcresson 6 weeks postoperalively (l d).
Fig. 2 Cl scans alter lumbar injection 01 suaerochnoid contrast medium lor cislemography to ovest aete CSf and cyst flu id communicalions in a 29 ys old man (HGl 200656) with healf. ache. Bulging and thinning 01 the right lemporal bOlle over the exparidl1garachnoid cyst 01 the middle lossa. Changes in mean density values (ME) 01 the cyst Iluid demonstrate patent but delayed communication 01 the cyst, although signs and symptoms of Iocal compression were present: a)and b) ME alter 12 hs 13.7 HE arid 10.2 HE; c} alter 24 hs 17.8 HE; d)alter 72 hs 10.4HE.
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178 Neurochirurgia 35 (1992)
{I,!elUochirurgia 35 (1992)
Ara chnoid cys ts of the middle cranialfossa
Fig. 3 Cl scens demonstrating a noocomnuücating iltraarachnoid cyst 01 the left middle crarsa tcssa 1 h after contrasl medium cisterrography fl a 54 yeers old female !WB 190238) admrtled beceuse of heedaches.
Clinical aspects Most of the intraaraehnotd cysts 300m 10re main asymptomatic throughout the life . How ever; the physical a nd neurological signs a nd symptoms. if they oceure. reflect their mass effect on compressed adjacent te mporal br a in structures an d on 3rd an d 6th erentel nerves be sides their elTect on CSF flow causi ng hydrocephalus. In our series, 18 patients with middle cranial rosse CYSIS (3 childre n. 15 adults i came 10 medical atte ntion an d were ope rared because of hea daches la sting for years without accompa nying ne urological deficits in all but two. Follow up er scans demonstrated increasing hydro cephalus that caused intracranial hypertension an d vomiting only in two adults. Convulsive seizures hav e bee n obs erved a s leading symptoms in three cases. l\vo boys were admltted as emergency ca ses suffertng from subdural hematoma after mild hoa d tra uma . in whom the aracbnold cysts ha d been asymp tomatic before (Fig. 8). vessels in the wall ofthe cyst (Fig. 7) pa rticularly susceptible to trau ma may be responsib le for the hem orrhage. as in patients (5.8.27). er scans ma de the definitive diagn ose of the mass lesion in aU our cases (2.9). MRI sca ns (Fig. 5) olTer superior diagnostic infor ma tion compared with er scan s by d iscriminati ng bet\licc n the CSF of true arachnoid cysts . residua l hemorrhage into or around the cyst. and the fluid of neoplastic cysts (6.81. Howe\'er in res pect to the bony structures we stiDprefer er as the diagnostic method of choice an d include contrast medium cistemography for the follow-up examinations (Figs . Z. 5. and 6).
Ag.4 Cl scens demonstrating a COOVTUlCamg Iltraaractnoid cyst 01tre left mIlkIe t rarwal fossa 2 h aftercontrast medUni csterogra~ 13 e. bl with cooseaerce 01~Il:oneal s/'IlI'll: oocedlSe13 cl 111 a 35 years oIdman (K-HH 1102S4J aaritted teceee 01
reeeecres.
Fig.5 MRI scans CTR 2.10. TE 28. Ll8.0. SP 48.6 Dr. tneoe. MJn.
sterl tl traaanial evst cf the left rridde cranial fossa with speec h disturbances and diso/acement of ee lerl'l)Ol"a1 lobe as consequence of matlormation because 01 thecontinabon with a eleeO seated Ieft fron. tomedIobasai a-v-malfonnabonof Ihe i'lsula and caputn. caudattm 111 a 47 years 0Id mal pabeft [tti 08 03#40) oMlo was adrntted because of epilepsy arid Ieftlroolotemporal headaches.
Surgicalrreatmenl. rists. and outcome Intraventri cula r and ep idural Ic r monitoring did not correspond in our series with clinical signs and symptoms of increased intra crania l pressure that was ca used by CSF disturban ces or by the mass elTect itself. es pecially in case of imp ressive hydroceph alic dilatation of the ventricular system.
The two main questions a re the indications for sur~cal treatment an d the therapeutic elTect which can be expccled . Genera lly speaki ng. it depen ds on the complaints of the patient corresponding to objective c1inical findings. whether or not surgery is indicated after the diag· nosis has been confirmed. Time an d type of appro priate
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bone (Fig. 21. eleveno n of the lesse r a nd a forward projection of the gr eater sphenoid wing. so that the middle rosse on the side of the cyst becom es wider than that on the nor ma l side (91. For eshortening er the tempora l lobe. as the cyst occupies the a nterior or the posterior temporal area, ts demonstrated by er and magneue resonace imaging (MRI) (Fig. 21. 111e tip of the temporal lobe may be abse nt although the gyrt on the adja cent part of the bra in are ncrmal while th e insula is exposed and its opercu la absent in the sense of a dysgeneti c temporal lobe (Figs. 5.61. 111e cysr may be small or terge . mostly rectan gular in horizontal Crcuts. a nd sometimes on bcth sides (Figs. 1,21. Displa cement of the frontal lobe (9) may be also present (H gs. 2, 6). Reexpansion of the brain can be observed after success ful opera tive treatme nt with decompression (Fig. 8). It is likely tha t the case in whlc h the cyst disappeared sup ports the theory of abnorma l development af the subar achnoid space as opposed to the cyst remaini ng as a conse quence of ab normal development of the temporal lohe during fetal life (Fig. 81. ücclustcn of the tento rial stn ue. tnto which the telencephaltc vein flows , has been descr ibed when the Sylvian vein is not visualize d on cerebral angiography (8. 9); the combina tion with an arue rto -ven ous rnallorm ation of the sa me regten may confirm thls thoory (Hg . 5).
179
K. von Wild
Neurochirurgia 35 (1992) Fig. 6 MRI scans
20.03.90 lTR 0.52, TE 20, SL 5, SP 5.5
01'. Thiede, Münster) demonstrating a large Ief! fronlotemporal arachnoid cyst in a 23 veers old male patent (SR 240267) who was admitted because of headacne, frontobasal psychosyndrome and speech dislurbances. Congential meucrrne tion wilh dysplasia of frontal and temporal obes. lndication tor cysto-pentoneal shunt in resoect of CSF communicalion end expansion of lhe cyst.
operative procedure have 10 be designed in the ind ividual case of the pediatri c as we il as of the adult age group (1,4, 5,8, 10 - 12. 15, 16,2 1,23,25): Ta ppin g or shunting tho cyst. fenestrati on through a burr hole or tre ph ine operring. additional peri toneal shunting or exctston ofthe cyst (partly or completely) arn reco mmende d. In dication for su rgical Intervention is obviou s in cases of acute intracranial he morrhage an d evidence of elevered ICP with hydrocephalus. In cases. how eve r; where the cyst seems asymptomatic, we have to take into account the significant risk of surgical treatment in th is vulnerable anato mical regten. even postoperative fatalJties have becn re ported in prcvious papers (4, 20). This ts why so me authors sti ll emphasize conse rvative management in patients with cysts drscovered fort ultously or those causing only mild cosmetic defects. We are in agree ment with Har sh et al. (8) who stressed the potential for hindcring the de velopment and function of adjacent brain. particu larly in chü drc n. and for cyst ruptu re with int racystic he morrhage, or s ubdural hemo rrhage leading to sudden severe neurological deterioration . This has happened in two boys of our sertes. Therefore Jfar sh et al. (8) recommended cyst-peritonea l shunting procedures in all arachnoid cysts th at exert a m ass effect. as weil as cyst-ventriculo pe ritoneal sh unting in all cases if there ts an associated ventriculomegaly.
Fig.7 Arac oooid cyst cf Ihe Ief! middle cranial fossa. Microsurgical vew ot Ihesurtace with arachnoid membrane, reinforced wilh a cense collagenous layer and vesseis in Ihe wall crossing the cyst
Fig. 8 Follow-up Cl scan of a 7 yeers-old boyccerateo uoon for a posl-traumatic subdural hydroma. al betete operaton (19 october 1984), b)after ooeration (24 april 1986), demonslrating reorecemeot of Ihe rightlemporal lobe.
Contrary to this opinion from our experience we wish to suess that CT and microsurgica l tec hniques make cys t wall resccu on without shunting a safe surgical procedure. The practice in our d inic is as folIows : In case of Sylvian cyst with intracra nial rnass effect. e. g. displacement of tem poral and frontal lobes and ofmidline structures. with CSF disturbances, osteoplastic craniotomy is indicated as it is in case of complicated middle cranlal fossa cyst with su bd ural hygroma or hematoma. The cyst ts exposed th rough a free frontote mporal bone flap (Hg. 7). After tap ping of the cys t 10 gai n ad ditional expcsure. the anterior and medial pa rt of th e wall is resected atong its attachment to the normal arachn oid and pia meter; down to the tentorial no tch, where the thickened wall of the intraarachnoid cyst and adjacent arachnoid membranes are cut. w üh opening of the suprasetlar and prepontine cisterns tF ig. 7 ). Cranial nerves are
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180
Arachnoid cysts ofthe middle cranial f ossa
There wer e no operative or severe postoperative eomplications in our 18 consecuuve cases using this teehnique. However 6 weeks alter decompression of a left temporal araeh noid eyst one male patient was readmitted beca use of a ehronic subdural hema tom at the eontralateral side where there was another temporal arae hnoid cyst. Beeause of the development of hydrocephalus three patients needed a shu nting proeedure during the follow up: one a eystoperiton eal 3 months after the evacuation of traumatte subdura l hem atoma and partial resection of the araehnoid eyst and two other patients required ventriculoperitoneal drainage. The shunü ng proeedures resulte d in the immediate improveme nt of foeal neurologteal defieits and reexpansion ofthe temporal lobe as demonstrated by CT postoperatively. We saw one translent 3rd nerve palsy lasting 3 weeks in ease of a very large eyst. Tempora l seizures disappeared in th ree patients, although the re were still foeal dysrhythm ie abno rma ltnes showing loealized slow waves or a n asymmetrie depression of the electr fcal aetivity but no further spikes and waves in the EEG. In aseries of 36 eases of supratentorial cysts in children Cnoux et al. (4) reported epileptie fits in 18 eases as weil as mental and motor retardation in 19 children when seteur es have persisted in spite of surgery in a bout 50 %! Moreover, one of these 16 ehildren developed new gran d mal selzures with worsening of her neurologieal deficit even after ventrtculo-perttoneal shunt. Although final outeome for epilepsy remains, from these and other reports. still open we do be· lieve that in patients, especially in children, open microsur l{ical reseetion ofthe medial wall ofthe araehnoid eyst is indieated in eases of focal epileptie pattern in the EEG records related to the frontotemporal cortex, even if there is no inereased intraera nial pressure. CSF-disturbanees, and no loeal brain eompression or displacement. Conclu sion Comparing our res ults with those in the literature , partial mierosurgieal exeision of the arae hnoid cyst wall and opening of the basal cisters at the tentorial nooch has proved to be an efTective and safe procedure. Reexpans ion ofthe compressed temporal lobe has been demonstrated by CT. Can surgieal eure, however. be aehieved? Loeal neurological deficits usually improve immediately after the operation. Headaehe and seizures may be diminished and can disappear, but the y may persist or increase in frequeney after deeompression . We therefore ean not predict the outeome in arachnoid cyst
Arachnoid cysts of the middle cra nial fossa K. von Wild Neurochirurgische Abte ilung Clemenshos pttal. Akadem isches Lehrkr anke nhaus der westr. wühefms-unrversüät Münster
In 18 cas es of temporal arachnoid cysts the etiology. clinical a nd radiographie ündtngs. surgical treat ment. and outcome are reviewed . Cysts of the middle erentel fossa are susceptible to trauma, which may cause bleeding either Into the cyst or lnto the subdural space. er or MRI sean s are dta gnosdc in arachnoid cysts . In cases ofintracranial mas s lesion with dis placem ent of th e midline str uctures end increas ing [e p, osteoplastic craniotomy ts performed and the medial wa ll of tbe cyst is resected down to the tentorial notch . with opening tnto the basal ciste rns . Ther e were 00 operative or postoperative complicat ions in 18 consecutive cas es. However, one boy required a cysto peritoneal shunt 3 months la ter as a result of hydrocephalus following subdural hematoma a nd two other pati ents were also subsequently shunted. Asymptomatic a raeh noid cysts are disoussed with the respect to brain function and potential risks.
Key-words Arac hnoid cyst s - Subdura l hematoma Hydr ocephalus - Peritoneal shunt - Microsurgica l tech nique - Congemtal Jestons
Introdu cnon Although recent studies ha ve evaluated new concepts of the pathogenesis. anatomieal ultrastructure, clinioal an d radiclogical manifestations of intr aarachnoid cysts, as the y are called today, the re ts an ongotng debate a s to the cho iee of their proper surgi cal treatment in re spect to the final outcome of patients in the pedtatric and ad ult age group (5, 8, 10, 12,1 5, 16. 21, 23). Since the ad vent of cranial com puterized tomography (CT). num erou s case reports have been presented. We are in a greement with most of the se a uthors that these lesion s are much more common the n previously rea lized when they are dtagnosed by chance being asym pto mati c before. According to Robinson (19, 20) arachnoid cysts account for ahout 1 % of all atra umatic intracranial mass lestons. Most of the cysts become symptomatic in ea rly ch ildhood in so far as
Neurochirurgia 35 (1992) t 77- 182 © Georg Thleme Verla g. Stuugart - Npw York
Arac hnoidalzyste n de r mittl e ren Schädelgru be Die derzeitigen diagnostisc hen und neu roch irurgischen Beha ndlungsmögliehkeiten von temp oralen Arac hnoidalzysten werden vor dem Hintergrund gesicherter pathologisch-anatomis cher Kenntnisse an typischen Beispiele n von 3 Kind ern und 15 Erwa ch senen a ufgezeigt. Hierbei verd ient Beachtung, daß diese Zysten, die etw a die Hä lfte aller intrak ra niellen Arac hnoidalzysten ausmachen, durch lan gsame Größenzunahme Ursa che lokaler Hirndruckzeichen und von Liquorzt rkulationsstörungen sein könn en. Besonders bei Kind ern besteht die Gefahr subduraler Blutungskomplikationen nach leichten Schädelhirn verletz ungen und die Möglichkeit von zerebralen Kr ampfanfällen. Schließ lich bewirken die Zyste n eine Entwicklungshemmung der verlagert en und komprimiert en Hirnlap penstru ktu ren. die sieh nach erfolgreicher Entlastun g wieder a usdehnen. Die Vorteile der mikrochirurgischen Zyst enwandresektion mit Wiederherstellung einer freien basale n Uquorzirkulation sowie die Möglichkeite n eines ventriku lo- oder zysto-peritoneale n Shunts wer den aufgrund eigener Erfahrungen und unte r Berücksi chtigung der Literatur diskuti er t.
60 % to 90 % of pe uents in mixed sories have been shown to be in the pediatric age group (I , 2, 8, 9, 14- 17). The dis tribution of arachnoid cysts in two hundred and eight collected cases of Rengachary et al. (17) was as follows . Sylvian fissure, 49 %; cerebellopo ntine angle, 11 %; supra-collicula r a rea , 10 %; the vermts. 9 %; sella r and suprasellar area. 9 %; interhemispheric fissure , 5 %; cerebral convexity, 4 %; the d ival and interpeduncular a rea. 3 % . This paper will deal exclusively with cysts ofthe mlddle cranial fossa since they consütute abo ut one ha lf of all cases and a re of major neurosur gtcal interest on account of malformatio n of the base of the skull and fronto-tempora l bone, progressive hydrocephalus syndrome , epilepsy, and are an im porta nt cause of associated hemorrhagic comp lications after minor head trauma (1, 4, 5 - 9, 11-13, 17, 18,27).
Pathology Morpho logical decades have elucidated the anato mieal ultra structure of were described for the first
studies during the last two pa thogenesis as weil as the intraarachno id cysts , which tim e by Bright (3) in 183 1.
Downloaded by: Universite Laval. Copyrighted material.
Sum m ary
llowever, the cause of the a rachnoid eysts in generar remains still controverstal. They are classlfled today Into two groups: - first: ccngenita l ma lform ations tptgs. 1- 8) (4.8. 11, 17 20 .2 2,25) .
- second . resulting from lnfla mmatlon , herncrrhage. tra uma , tumor (1 . 12, 24). Distin ct from these intra ar a chnoid eysts the middle -fossa pitholes and the tnt radiploic a raehnoid cysts are different pa thogenetic enuues (26) . arid are not discussed he re . The historieal rovlew shows tha t ara chnold cysts ha ve been given a vartety of designa tions, reflecting differe nt pathogenetie fac tors, for insta nce: ehronie cystic arachnoiditis. meningitis serosa ctrc umsc rtpta. eh re nie a rac hnciditis. cere bral pseudotumur, leptomemngaal cyst, or simply pnmary oth erwise idio pathic arachno id cyst (24). There is clear cvlden ce that som e arachnoid cysts do commun icate with the suba raehnoid space. This is bea utifully demonstrated by isotope cistern ogra phy end still better today wit h cont rast me dium CT ctsternog ra ph y (9) (Figs. 2 - 4). Aeeor din g to these functional studie s we call the m communicating or noncommunieating arachnoid cysts. These cysts have to be dist ingu ished from morphologica l findings like arachnotd diverüculum, ara chnoid hernia, aru chnold pouch . internalmeningoeele, and arachnoidoceie (18).
Starkman et al. (24) have demonstrated for the first tim e, by evalua ting histologica l deta ils. dtfferences in the a natomieal relationships of the idiopathic eysts from those following inflamma tory or irritative eon ditions . Therefore th ey sug gested that these pr imary eysts originate from anomalous developmental splitt ing of the araehn oid me mbrane as they are enveloped by the leptom eni nges and related to the ctste rns and the subarae hnoid spaee (Figs. 3.
K.
VOll
Wild
61. 'IoRengachary and Watanabe (17, 18) the eredit is principally du e that they were a ble to demonstrate wit h light and eleetron mtcroscopic Iindings the splitting ofthe araehnold membrane to enclose the cyst, wh ile the pia ma ter rema ins as aseparate Inta ct membra ne (Fig. 7). Moreover the cyst wa ll was rein forced with a den se collage nous layer in respo nse to high intraeystie prcssure. whic h may be suffieient 10 ca use erosion a nd expa nsion of the ealvarium. Th us. intr aarachnoid cysts are a develo pme ntal a noma ly of the subarachnoid ciste rns in the developing embryo causing a minor aberratio n in the CSF flow with in the subarac hnoid space , and resulting in an increasing divertic ulum wit hin the araehnoid me mbrane. This is why these cysts oceur nearly always in relation to an su baraehnoid ctstern . approximately half of them Involvi ng the Sylvian fissure (Figs. 1,4.6.7). Like lnte rhernispherlc cysts the Sylvia n fissu re arachnoid eysts ten d to become very large (Figs. 5. 6 ). The inte rmittently communieating type of cyst (Figs. 2. 3) may expand by progressive accumulation ofCS F secreted through cells of the cyst wall rather than by osmotically induced filtratio n or uni -direetional CSF Ilow - the latter was called "ball-valve tr a pping " by Smuh an d Smith (1976) . This mechanismus has to be ta ken into aecount wh en shunti ng procedere and resection of the cyst wa Uare discussed. The contained fluid is usua lly clear and eolorless. If the protei n content is higher than CSF. this ma y be the residue of an intracystic bemor rhage. The latter h as bee n reported by us and others even a fte r min or head tra uma , when acute or ehronie su bdural hemorrhage oecur in combination with intraarachnoid eysts mostly of the Sylvtan region (1, 5, 27). As already menuoned arachnoi d eyst of th e middle fossa themselves re present compressive elements ca using both loeal bulging and thinning of the temporal
Fig. 1 Cl scans 01 bilateral intraarachnoid
cvsts 01 the middle cranarrossa {l a, b1 in a 24 years oId man (HD 051 1641who was admitted because 01 beadaches arid ecaectc fits with tocar spike eno wave electrical octivity over the left !rontotemporal region. EpidurallCP measurement was in normal renge. Microsurgical ooeo ing 01 theleft cyst with cecorcresscn Uarge black errowl 01 the temporal lobe tsmeu black arrow, I cd). Chronic subdural hematoma frontal light due to oeccrcresson 6 weeks postoperalively (l d).
Fig. 2 Cl scans alter lumbar injection 01 suaerochnoid contrast medium lor cislemography to ovest aete CSf and cyst flu id communicalions in a 29 ys old man (HGl 200656) with healf. ache. Bulging and thinning 01 the right lemporal bOlle over the exparidl1garachnoid cyst 01 the middle lossa. Changes in mean density values (ME) 01 the cyst Iluid demonstrate patent but delayed communication 01 the cyst, although signs and symptoms of Iocal compression were present: a)and b) ME alter 12 hs 13.7 HE arid 10.2 HE; c} alter 24 hs 17.8 HE; d)alter 72 hs 10.4HE.
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178 Neurochirurgia 35 (1992)
{I,!elUochirurgia 35 (1992)
Ara chnoid cys ts of the middle cranialfossa
Fig. 3 Cl scens demonstrating a noocomnuücating iltraarachnoid cyst 01 the left middle crarsa tcssa 1 h after contrasl medium cisterrography fl a 54 yeers old female !WB 190238) admrtled beceuse of heedaches.
Clinical aspects Most of the intraaraehnotd cysts 300m 10re main asymptomatic throughout the life . How ever; the physical a nd neurological signs a nd symptoms. if they oceure. reflect their mass effect on compressed adjacent te mporal br a in structures an d on 3rd an d 6th erentel nerves be sides their elTect on CSF flow causi ng hydrocephalus. In our series, 18 patients with middle cranial rosse CYSIS (3 childre n. 15 adults i came 10 medical atte ntion an d were ope rared because of hea daches la sting for years without accompa nying ne urological deficits in all but two. Follow up er scans demonstrated increasing hydro cephalus that caused intracranial hypertension an d vomiting only in two adults. Convulsive seizures hav e bee n obs erved a s leading symptoms in three cases. l\vo boys were admltted as emergency ca ses suffertng from subdural hematoma after mild hoa d tra uma . in whom the aracbnold cysts ha d been asymp tomatic before (Fig. 8). vessels in the wall ofthe cyst (Fig. 7) pa rticularly susceptible to trau ma may be responsib le for the hem orrhage. as in patients (5.8.27). er scans ma de the definitive diagn ose of the mass lesion in aU our cases (2.9). MRI sca ns (Fig. 5) olTer superior diagnostic infor ma tion compared with er scan s by d iscriminati ng bet\licc n the CSF of true arachnoid cysts . residua l hemorrhage into or around the cyst. and the fluid of neoplastic cysts (6.81. Howe\'er in res pect to the bony structures we stiDprefer er as the diagnostic method of choice an d include contrast medium cistemography for the follow-up examinations (Figs . Z. 5. and 6).
Ag.4 Cl scens demonstrating a COOVTUlCamg Iltraaractnoid cyst 01tre left mIlkIe t rarwal fossa 2 h aftercontrast medUni csterogra~ 13 e. bl with cooseaerce 01~Il:oneal s/'IlI'll: oocedlSe13 cl 111 a 35 years oIdman (K-HH 1102S4J aaritted teceee 01
reeeecres.
Fig.5 MRI scans CTR 2.10. TE 28. Ll8.0. SP 48.6 Dr. tneoe. MJn.
sterl tl traaanial evst cf the left rridde cranial fossa with speec h disturbances and diso/acement of ee lerl'l)Ol"a1 lobe as consequence of matlormation because 01 thecontinabon with a eleeO seated Ieft fron. tomedIobasai a-v-malfonnabonof Ihe i'lsula and caputn. caudattm 111 a 47 years 0Id mal pabeft [tti 08 03#40) oMlo was adrntted because of epilepsy arid Ieftlroolotemporal headaches.
Surgicalrreatmenl. rists. and outcome Intraventri cula r and ep idural Ic r monitoring did not correspond in our series with clinical signs and symptoms of increased intra crania l pressure that was ca used by CSF disturban ces or by the mass elTect itself. es pecially in case of imp ressive hydroceph alic dilatation of the ventricular system.
The two main questions a re the indications for sur~cal treatment an d the therapeutic elTect which can be expccled . Genera lly speaki ng. it depen ds on the complaints of the patient corresponding to objective c1inical findings. whether or not surgery is indicated after the diag· nosis has been confirmed. Time an d type of appro priate
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bone (Fig. 21. eleveno n of the lesse r a nd a forward projection of the gr eater sphenoid wing. so that the middle rosse on the side of the cyst becom es wider than that on the nor ma l side (91. For eshortening er the tempora l lobe. as the cyst occupies the a nterior or the posterior temporal area, ts demonstrated by er and magneue resonace imaging (MRI) (Fig. 21. 111e tip of the temporal lobe may be abse nt although the gyrt on the adja cent part of the bra in are ncrmal while th e insula is exposed and its opercu la absent in the sense of a dysgeneti c temporal lobe (Figs. 5.61. 111e cysr may be small or terge . mostly rectan gular in horizontal Crcuts. a nd sometimes on bcth sides (Figs. 1,21. Displa cement of the frontal lobe (9) may be also present (H gs. 2, 6). Reexpansion of the brain can be observed after success ful opera tive treatme nt with decompression (Fig. 8). It is likely tha t the case in whlc h the cyst disappeared sup ports the theory of abnorma l development af the subar achnoid space as opposed to the cyst remaini ng as a conse quence of ab normal development of the temporal lohe during fetal life (Fig. 81. ücclustcn of the tento rial stn ue. tnto which the telencephaltc vein flows , has been descr ibed when the Sylvian vein is not visualize d on cerebral angiography (8. 9); the combina tion with an arue rto -ven ous rnallorm ation of the sa me regten may confirm thls thoory (Hg . 5).
179
K. von Wild
Neurochirurgia 35 (1992) Fig. 6 MRI scans
20.03.90 lTR 0.52, TE 20, SL 5, SP 5.5
01'. Thiede, Münster) demonstrating a large Ief! fronlotemporal arachnoid cyst in a 23 veers old male patent (SR 240267) who was admitted because of headacne, frontobasal psychosyndrome and speech dislurbances. Congential meucrrne tion wilh dysplasia of frontal and temporal obes. lndication tor cysto-pentoneal shunt in resoect of CSF communicalion end expansion of lhe cyst.
operative procedure have 10 be designed in the ind ividual case of the pediatri c as we il as of the adult age group (1,4, 5,8, 10 - 12. 15, 16,2 1,23,25): Ta ppin g or shunting tho cyst. fenestrati on through a burr hole or tre ph ine operring. additional peri toneal shunting or exctston ofthe cyst (partly or completely) arn reco mmende d. In dication for su rgical Intervention is obviou s in cases of acute intracranial he morrhage an d evidence of elevered ICP with hydrocephalus. In cases. how eve r; where the cyst seems asymptomatic, we have to take into account the significant risk of surgical treatment in th is vulnerable anato mical regten. even postoperative fatalJties have becn re ported in prcvious papers (4, 20). This ts why so me authors sti ll emphasize conse rvative management in patients with cysts drscovered fort ultously or those causing only mild cosmetic defects. We are in agree ment with Har sh et al. (8) who stressed the potential for hindcring the de velopment and function of adjacent brain. particu larly in chü drc n. and for cyst ruptu re with int racystic he morrhage, or s ubdural hemo rrhage leading to sudden severe neurological deterioration . This has happened in two boys of our sertes. Therefore Jfar sh et al. (8) recommended cyst-peritonea l shunting procedures in all arachnoid cysts th at exert a m ass effect. as weil as cyst-ventriculo pe ritoneal sh unting in all cases if there ts an associated ventriculomegaly.
Fig.7 Arac oooid cyst cf Ihe Ief! middle cranial fossa. Microsurgical vew ot Ihesurtace with arachnoid membrane, reinforced wilh a cense collagenous layer and vesseis in Ihe wall crossing the cyst
Fig. 8 Follow-up Cl scan of a 7 yeers-old boyccerateo uoon for a posl-traumatic subdural hydroma. al betete operaton (19 october 1984), b)after ooeration (24 april 1986), demonslrating reorecemeot of Ihe rightlemporal lobe.
Contrary to this opinion from our experience we wish to suess that CT and microsurgica l tec hniques make cys t wall resccu on without shunting a safe surgical procedure. The practice in our d inic is as folIows : In case of Sylvian cyst with intracra nial rnass effect. e. g. displacement of tem poral and frontal lobes and ofmidline structures. with CSF disturbances, osteoplastic craniotomy is indicated as it is in case of complicated middle cranlal fossa cyst with su bd ural hygroma or hematoma. The cyst ts exposed th rough a free frontote mporal bone flap (Hg. 7). After tap ping of the cys t 10 gai n ad ditional expcsure. the anterior and medial pa rt of th e wall is resected atong its attachment to the normal arachn oid and pia meter; down to the tentorial no tch, where the thickened wall of the intraarachnoid cyst and adjacent arachnoid membranes are cut. w üh opening of the suprasetlar and prepontine cisterns tF ig. 7 ). Cranial nerves are
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180
Arachnoid cysts ofthe middle cranial f ossa
There wer e no operative or severe postoperative eomplications in our 18 consecuuve cases using this teehnique. However 6 weeks alter decompression of a left temporal araeh noid eyst one male patient was readmitted beca use of a ehronic subdural hema tom at the eontralateral side where there was another temporal arae hnoid cyst. Beeause of the development of hydrocephalus three patients needed a shu nting proeedure during the follow up: one a eystoperiton eal 3 months after the evacuation of traumatte subdura l hem atoma and partial resection of the araehnoid eyst and two other patients required ventriculoperitoneal drainage. The shunü ng proeedures resulte d in the immediate improveme nt of foeal neurologteal defieits and reexpansion ofthe temporal lobe as demonstrated by CT postoperatively. We saw one translent 3rd nerve palsy lasting 3 weeks in ease of a very large eyst. Tempora l seizures disappeared in th ree patients, although the re were still foeal dysrhythm ie abno rma ltnes showing loealized slow waves or a n asymmetrie depression of the electr fcal aetivity but no further spikes and waves in the EEG. In aseries of 36 eases of supratentorial cysts in children Cnoux et al. (4) reported epileptie fits in 18 eases as weil as mental and motor retardation in 19 children when seteur es have persisted in spite of surgery in a bout 50 %! Moreover, one of these 16 ehildren developed new gran d mal selzures with worsening of her neurologieal deficit even after ventrtculo-perttoneal shunt. Although final outeome for epilepsy remains, from these and other reports. still open we do be· lieve that in patients, especially in children, open microsur l{ical reseetion ofthe medial wall ofthe araehnoid eyst is indieated in eases of focal epileptie pattern in the EEG records related to the frontotemporal cortex, even if there is no inereased intraera nial pressure. CSF-disturbanees, and no loeal brain eompression or displacement. Conclu sion Comparing our res ults with those in the literature , partial mierosurgieal exeision of the arae hnoid cyst wall and opening of the basal cisters at the tentorial nooch has proved to be an efTective and safe procedure. Reexpans ion ofthe compressed temporal lobe has been demonstrated by CT. Can surgieal eure, however. be aehieved? Loeal neurological deficits usually improve immediately after the operation. Headaehe and seizures may be diminished and can disappear, but the y may persist or increase in frequeney after deeompression . We therefore ean not predict the outeome in arachnoid cyst
