Villi arachnoidales undergoes in the course of life changes in relation to the skull
bones and sinuses. Our aim was to determine the relations of the villi arachnoidales to
the skull bone and/or sinuses from the neonatal period to adults. The investigations
were performed on collection of 50 disarticulated macerated skull bones from the newborn
to 30 years of age and on 20 skulls from individuals in the life period from 30 to 80
years of age. Villi arachnoidales produced imprints on the skull bones in the shape of
holes and/or furrows corresponding to different shape of the villi arachnoidales. These
imprints appeared very early in the period when the bony sprouts of the large skull
bones received a thin covering of compact bone, the future lamina vitrea. At that time
villi arachnoidales had no connection with the dural sinuses but with the diploe and
with the diploic veins. By agglomeration of the villi in larger and large formations,
granula meningea, Pacchionian granulations, the contact to sinuses was realized by
means of short channels. The structural changes of villi arachnoidales may produce
thrombophlebitis and hydrocephalus externus, especially in children. The fate and the
relations of the villi arachnoidales are therefore of great importance for neurologist,
neurosurgeon and otorhinolaryngologist

Ivan Vinter

Jelena Krmpotić-Nemanić

Slaven Suknaić

Zlatko Kelović

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Coll. Antropol. 27 (2003) 2: 611–616UDC 611.819:612.824Original scientific paperThe Fate of the Arachnoid Villiin HumansJelena Krmpoti}-Nemani}, Ivan Vinter, Zlatko Kelovi} and Slaven Suknai}Department of Anatomy »Drago Perovi}«, School of Medicine, University of Zagreb, Zagreb,CroatiaA B S T R A C TVilli arachnoidales undergoes in the course of life changes in relation to the skullbones and sinuses. Our aim was to determine the relations of the villi arachnoidales tothe skull bone and/or sinuses from the neonatal period to adults. The investigationswere performed on collection of 50 disarticulated macerated skull bones from the new-born to 30 years of age and on 20 skulls from individuals in the life period from 30 to 80years of age. Villi arachnoidales produced imprints on the skull bones in the shape ofholes and/or furrows corresponding to different shape of the villi arachnoidales. Theseimprints appeared very early in the period when the bony sprouts of the large skullbones received a thin covering of compact bone, the future lamina vitrea. At that timevilli arachnoidales had no connection with the dural sinuses but with the diploe andwith the diploic veins. By agglomeration of the villi in larger and large formations,granula meningea, Pacchionian granulations, the contact to sinuses was realized bymeans of short channels. The structural changes of villi arachnoidales may producethrombophlebitis and hydrocephalus externus, especially in children. The fate and therelations of the villi arachnoidales are therefore of great importance for neurologist,neurosurgeon and otorhinolaryngologist.Key words: villi arachnoidales, skull bones, arachnoidea, diploic veins, foveolaegranulares, Pacchionian granulations, hydrocephalusIntroductionArachnoid villi undergo in the courseof life changes concerning the shape, den-sity and/or agglomeration in larger for-mations, i.e. Pacchionian granulations.Pacchionian granulations produce de-fects in the skull bones forming the foveo-lae granulares. Larger agglomerations offoveolae granulares, fossae lacunares, aresaid to be localized at either side of thedural sinuses communicating with them611Received for publication October 7, 2003by short channels. The investigations re-lated to the arachnoid villi and/or Pac-chionian granulations are connected withnames of Key-Retzius1 and Weed2,3 whofound that »the major absorption of thecerebrospinal fluid in the region of thebrain is directly into the great dural ve-nous sinuses by way of villi arachnoi-dales. Villi were found to occur in all ofthe common laboratory mammals and ininfants. When hypertrophied as in adults,they were identified as the well knownPacchionian granulations. The structureof the arachnoid villus consists of a redu-plication of the meshes of the arachnoi-dea with usually a decreased size of thenetwork. The covering of the cells of thearachnoid membrane are carried into thedefect of the dural fibrous tissue so thatarachnoidal cells come to lie directly be-neath the endothelium of the great ve-nous sinuses. In most cases there is amore or less outspoken aggregation ofarachnoidal cells at the top of the villus2.«The villi in the region of the basilar si-nuses are more cellular and of a smallermesh4. Mesothelial cells are capping thevillus. Between the mesothelium and thecollagen structure there exists a net offibres5. Besides the structural villi thereexist also finger-shaped arachnoidal cell-strings which penetrate the more distantdural tissue. The shape of the villi can beegg-shaped, pear-shaped or grape-sha-ped. According to Gärtner and col.4 thePacchionian granulations appear with 18months and become tighter in the courseof life. According to Hommer6 the Pac-chionian granulations are distributed in-dependently from the sinuses over the ce-rebral surface. Rouvière7 mentions thatthe Pacchionian granulations can protru-de either into blood lakes or into thedural sinuses. On the contrary Adams8describes a direct communication of thearachnoidal granula with major dural si-nuses. Gomez-Potts9 describe »that thearachnoid granulations are protrusion ofarachnoid cells through small dural de-fects into the superior sagittal sinus ortributary veins». Ojala10 mentions thatthe villi can penetrate the spaces and thevenous spaces in the region of the middleear causing in certain cases the thrombo-phlebitis. Shukla and coll.11 mention theconnection of the dural sinuses with thediploic veins.We decided to study in human mate-rial the relations of the villi and of thePacchionian granulations to the skull bo-nes, to the dural sinuses and the diploicveins in different life periods.Material and MethodsWe investigated the first appearanceof the holes and/or furrows produced byvilli arachnoidales and/or by granulameningea in human material on our col-lection of 50 skull bones in the life periodfrom the newborn to 30 years of age. Wechecked also the localization, the depthand the shape of the foveolae granularesand fossae lacunares on 20 specimens ofthe individuals in the life period from 60to 80 years of age.ResultsThe holes and the furrows producedby villi arachnoidales were found alreadyin the human newborn i.e. in the periodwhen bony sprouts of the skull bones gotthe first covering of the future laminavitrea (Figure 1). These holes were spre-ad over the skull bones independently ofthe future dural sinuses. We gave to the-se holes the name »foveolae arachnoida-les». With agglomeration of the villi ap-peared deeper holes in the skull bones,the foveolae granulares. They appearedalready with 3 years of age (Figure 2),which is much earlier than stated in gen-eral in the literature (10 years of age)12.Neither of these formations was in thislife period related to the sinuses (Figure612J. Krmpoti}-Nemani} et al.: Arachnoid Villi, Coll. Antropol. 27 (2003) 2: 611–6163). By intensive agglomeration of the Pac-chionian granulations appeared in olderindividuals on the inner surface of theskull bones larger multilocular holes, fos-sae lacunares, most of which were situa-ted on either side of the large dural si-613J. Krmpoti}-Nemani} et al.: Arachnoid Villi, Coll. Antropol. 27 (2003) 2: 611–616Fig. 1. The squama of the frontal bone consists in the newborn of bony sprouts which display a thincovering by the future lamina vitrea. Lamina displays imprints in shape of holes and furrowscorresponding to the differently shaped villi arachnoidales.Fig. 2. Foveolae granulares on the inner surface of the squama of the frontal bone in a 3 years oldchild. They are situated far form sinuses and communicate with diploic space and diploic veins.nuses and connected with them by meansof short channels. A large number of fos-sae lacunares situated in the region of theala magna of the sphenoid bone, in the in-ferior part of the squama of the temporalbone and in the cerebellar fossae were notdirectly connected with the dural sinusesbut with diploic veins and/or venous plex-uses e.g. plexus pterygoideus.The foveolae granulares found betweenthe tegmental region and the temporalsquama are probably identical with thecases described by Ojala10. The number ofthe foveolae arachnoidales as well as ofthe foveolae granulares prevailed in thefrontal and parietal bones. The fossaelacunares were mostly localized on eitherside of the superior sagittal sinus and inthe region of the confluens sinuum. Insome cases the fossae lacunares pene-trated through the diploe to the level ofthe outer lamina vitrea or even under theperiost of the skull bones.DiscussionThe finger-shaped, pear-shaped orgrape-shaped prolongations of the ara-chnoid, villi arachnoidales produced im-prints in the shape of holes or furrowswithin the first thin layer of the internallamina vitrea of the skull bones. Theseholes and/or furrows were spread all overthe skull bones but they prevailed in thefrontal bone. The imprints of the villi aswell as the villi themselves had no con-nections with the developing sinuses. Af-ter the formation of the inner laminavitrea the villi formed agglomerations,granula meningea, which produced foveo-lae granulares. The foveolae granulareswere spread over the skull bones withoutcommunication with the dural sinuses.Foveolae granulares appeared alreadywith 3 years of age which is much earlierthan stated in the literature. Further ag-glomerations of the meningeal granulaproduced larger imprints, fossae lacuna-614J. Krmpoti}-Nemani} et al.: Arachnoid Villi, Coll. Antropol. 27 (2003) 2: 611–616Fig. 3. Foveolae granulares in a 7 years old child spread over the inner surface of the frontal bonewithout direct connection with the sinus sagittalis superior. In this life period the communicationwith the sinuses is still not realized. It will be realized in later life periods and in adults.res, which approached the big dural si-nuses realizing connections with them bymeans of short channels. The filtration ofthe liquor from the villi and from thePacchionian granulations was realized atfirst via the diploic spaces and diploicveins. The general statement that Pac-chionian granulation and/or foveolae gra-nulares are always connected with the si-nuses is not correct. The greatest numberof foveolae granulares had no connectionat all with the sinuses. Fossae lacunaresas the large recipients and the filtrationplace of the liquor approached the si-nuses especially in the region of the sinussagittalis superior and the confluens si-nuum and usually were connected withthem by means of short channels. The ap-pearance of the fossae lacunares in theregions far from the sinuses speaks in fa-vor of the fact that the subarachnoidalspaces and /or cisternae are directly con-nected with the diploic venous system13.The contact with the big dural sinusesis realized in later life periods. This con-tact might however be missing.The relation of the villi arachnoidalesand granula meningea to the dural si-nuses, diploic veins or diploic spaces areof great importance in neurology, neuro-surgery, pediatric neurosurgery and oto-rhinolaryngology.Penetration of the villi in the region ofthe middle ear can cause thrombophle-bitis. The penetration of villi and/or gra-nula meningea through the ala magna ofthe sphenoid bone can cause thrombo-phlebitis of the pterygoid plexus whichmany results in a neuralgia of the man-dibular nerve. The penetration of the villiand/or granula meningica through theskull bones may represent the way of in-fections in either direction. This is morelikely to happen in adults where the ag-glomeration of villi in large formation oc-curs more often than in children.The situation within the region of villiarachnoidales is of great importance inpediatric neurology and pediatric neuro-surgery14. Changes in the structure ofvilli may be responsible for developmentof ventricular subaracnoidal hydrocepha-lus15 or chronic hydrocephalus16.R E F E R E N C E S1. KEY, G., A. RETZIUS: Studien in der Anato-mie des Nervensystems und des Bindegewebes.(Stockholm, 1875). — 2. WEED, L. H., Am. J. Anat.,31 (1923) 191. — 3. WEED, L. H., J.. Med. Res., 31(1914) 51. — 4. GÄRTNER, J., J. PFEIFFER, H. E.SCHAEFER, W. SCHÄTZLE, J. M. SCHRÖDER: Pa-thologie, T. 4: Neuropathologie. (Springer, Berlin-Heidelberg-New-York-Tokyo, 1984). — 5. SCHWAB,M.: Beitrag zur Morphologie der Pacchionischen Gra-nulationen (Granula meningica) des Menschen. Diss(Med. Fakult., Kiel, 1949). — 6. HOMMER, H.: Ueberdie Verteilung der Pacchionian Granulationen überder Hirnoberfläche. (Inaug. Diss., Leipzig l948). — 7.ROUVIÈRE, H.: Anatomie humaine: T. 3. (Masson,Paris, 1974). — 8. ADAMS, J. H.: Greenfield’s neu-ropathology. (Edward Arnold, London-Melbourne-Auckland, 1992). — 9. GOMEZ, D. G., D. POTTS G.,Arch. Neurol., 31 (1974) 88. — 10. OJALA, L., ActaPath. Scand., 91 Suppl. (1951) 88. — 11. SHUKLA, V.,L. A. HAYMAN, K. H. TABER, J. Comp. Ass. Tomogr.,27 (2003) 98. — 12. JUDA[, M., I. KOSTOVI]: Fun-damentals of neuroscience. In Croat. (University ofZagreb, Zagreb, 1997). — 13. LANG, J., Acta Anat.,86 (1973) 267. — 14. ABRIGHT, A., J. LELAND, F.POLLACK, P. D. ADELSON: Principles and practiceof pediatric neurosurgery. (Thieme, New York-Stut-tgart, 1999). — 15. CHAZAL, J., B. IRTHUM, T. JAN-NY, Neurochirurgie, 35 (1989) 379. — 16. MESSI-COTE, E. M., M. R. DEL BIGIO, J. Neurosurg., 91(1999) 80.615J. Krmpoti}-Nemani} et al.: Arachnoid Villi, Coll. Antropol. 27 (2003) 2: 611–616J. Krmpoti}-Nemani}Department of Anatomy »Drago Perovi}«, School of Medicine, University of Zagreb,[alata 11, 10000 Zagreb, CroatiaSUDBINA ARAHNOIDALNIH RESICA U ^OVJEKAS A @ E T A KVilli arachnoidales mijenjaju u toku `ivota odnos prema kostima lubanje i sinusima.Cilj ove studije bio je odrediti odnos arahnoidalnih resica prema kostima lubanje i si-nusima u postnatalnom `ivotu. Istra`ivanja smo vr{ili na seriji od 50 rastavljenih ma-ceriranih lubanja u dobi od novoro|en~eta do 30 godine `ivota, kao i na 20 lubanjskihbaza u dobi od 30 do 80 godine `ivota. Villi arachnoidales ostavljaju na kostima lubanjeotiske u obliku rupica i brazda {to odgovara obliku arahnoidalnih resica. Ti tragovi sevide vrlo rano, u stadiju kad ko{tani pruti}i na ljudskim pokrovnim kostima lubanjepo~inju dobivati sloj kompaktne kosti koja stvara laminu vitreu. U to vrijeme villi ara-chnoidales nemaju veze sa sinusnim nego sa spongiozom, diploe, i diploi~nim venama.Kasnije spajanjem arahnoidalnih resica u ve}e i velike formacije, granula meningea,Pacchionove granulacije, dolaze najve}e skupine resica putem kratkih kanala u kon-takt sa sinusima. Stanje arahnoidalnih resica i eventualne njihove promjene mogu bitiuzrok tromboflebitisa i hidrocefalusa, osobito kod djece. Stoga je poznavanje odnosaarahnoidalnih resica i njihovih odnosa od velike va`nosti za neurologa, neurokirurga iotorinolaringologa.616J. Krmpoti}-Nemani} et al.: Arachnoid Villi, Coll. Antropol. 27 (2003) 2: 611–616

The Fate of the Arachnoid Villi in Humans

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