Surg Radiol Anat (2010) 32:389–392

DOI 10.1007/s00276-009-0579-7

ANATOMIC BASES OF MEDICAL, RADIOLOGICAL AND SURGICAL TECHNIQUES

Endoscopic removal of a suprasellar arachnoid cyst: an anatomical study with special reference to skull base

Arnaud Dagain · Jean-François Lepeintre · Pietro Scarone · Ciprien Costache · Michel Dupuy · Stéphane Gaillard

Received: 23 May 2008 / Accepted: 7 October 2009 / Published online: 24 October 2009© Springer-Verlag 2009

AbstractBackground Suprasellar arachnoid cysts are rare entitiesin adults, representing 10% of all cysts. Endoscopic treat-ment is now preferred for this pathology, allowing a newanatomical approach to skull base structures.Objectives The aim of this study is to present the relevantanatomy of the skull base viewed during an endoscopicprocedure for a suprasellar arachnoid cyst.Method A 77-year-old man with 6 months history ofwalking disorder was referred for neurosurgical evaluation.Physical examination did not show any oculomotor orendocrine disorder. Sagittal T1-weighted MRI demon-strated a large suprasellar arachnoid cyst. The patientunderwent a ventriculocystocisternostomy without compli-cations. Postoperative neurologic examination showed aninitial improvement of walking disorders. Cerebral CT scanshowed a slight reduction in cyst dimensions.Results During the endoscopic procedure, the anatomicalview of the skull base was demonstrative. From the interiorof the cyst we were able to identify the following struc-tures: the clivus, pituitary stalk, pituitary gland, basilarartery, posterior cerebral arteries, posterior communicatingarteries, oculomotor nerves and the superior wall of cavern-ous sinus. We identiWed a slit valve mechanism in thearachnoid next to the basilar artery.Conclusion Ventriculocystocisternostomy is a useful pro-cedure in treating arachnoid cyst. Moreover, during thisprocedure, the endoscope allows for better and safer visual-ization of skull base structures.

Keywords Suprasellar arachnoid cyst · Neuroendoscopy · Neuroanatomy

Introduction

In 1831, Bright [2] published the Wrst description of anarachnoid cyst. Barlow in 1935 [1] reported the Wrst case ofsuprasellar arachnoid cyst. Some authors refer to thesecysts as prepontine arachnoid cyst [7, 12].

Suprasellar arachnoid cysts are rare entities in adults,representing 10% of all cysts, while in the pediatric popula-tion this reaches 15%. These cysts occur more often in menthan in women.

Endoscopic treatment is now the preferred mode of treat-ment, allowing a new anatomical approach to skull basestructures [4–6].

The aim of this study is to present the relevant anatomyof the skull base viewed during an endoscopic procedurefor a suprasellar arachnoid cyst.

Case report and anatomical Wndings

A 77-year-old man with 6 months history of walking dis-order was referred for neurosurgical evaluation. Thecerebral CT scan showed a triventricular hydrocephalus.Sagittal T1-weighted MRI demonstrated a large suprasel-lar arachnoid cyst which was responsible for that. Thelateral ventricles were asymmetrically dilated, the thirdventricle being totally collapsed, the pituitary stalk andthe optic chiasm were compressed (Fig. 1). Physicalexamination did not show any oculomotor or endocrinedisorder. The patient underwent a ventriculocystocister-nostomy.

A. Dagain (&) · J.-F. Lepeintre · P. Scarone · C. Costache · M. Dupuy · S. GaillardNeurosurgery Department, Hôpital FOCH, 40 avenue Worth, BP 36, 92151 Suresnes Cedex, Francee-mail: dr.adagain@gmail.com

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A rigid endoscope (Störz®) was used. A burr hole 1 cmjust in front of the coronal suture was made approximately3 cm from the midline. The endoscope was passed into thefrontal horn where the cyst membrane was seen occludingthe foramen of Monro witch was dilated. The opening of thecyst’s top wall was accomplished using a biopsy forceps.

The interior of the cyst showed: protrusion of clivus,pituitary stalk, pituitary gland, basilar artery, posterior (P1)cerebral arteries, posterior communicant artery, oculomotornerves and the superior wall of cavernous sinus. The dia-phragm sellae was seen forming the roof of the sella tur-cica. The anterior intercavernous sinus was identiWed in thediaphragm sellae in front of the pituitary stalk. The glandappeared to be concave superiorly in the area around thestalk. The infundibulum of the pituitary gland crossed theanterior space of the cyst to reach the opening of the dia-phragm sellae (Fig. 2). The third and the fourth cranial

nerve entered the dural roof of the cavernous sinus with thethird nerve in front and medial to the fourth nerve. Thethird nerve entered the cavernous sinus slightly lateral andanterior to the dorsum sellae, with the uncus of the tempo-ral lobe being lateral to it (Fig. 3). The right posterior com-municating artery was seen medial to the oculomotor nerveand was followed to the posterior cerebral artery. Threearterial branches were seen going to the hypothalamus,thalamus and internal capsule. We were able to identify aslit valve mechanism in the arachnoid next to the basilarartery. The slit opened with arterial inXow (Fig. 4). Thecyst’s lower wall was then perforated just in front of basilarartery to allow free Xow of cerebrospinal Xuid (CSF). Theremoval of the cyst did not modify the anatomical Wndingsduring the procedure.

Discussion

Arachnoid cysts are Wlled with CSF; their wall is made ofarachnoid cells [4]. They are most often located in front ofthe temporal lobe, or in the cerebellopontine angle, with thesuprasellar ones being rare in adults. The physiopathologyof these lesions remains unclear. There are three possiblemechanisms: a ball-valve mechanism, a Xuid Wltrationthrough the cystic wall due to an osmotic gradient, and asecretion of Xuid by the lining of the cyst [11]. Two diVer-ent types of suprasellar arachnoid cyst are described: a non-communicating intra-arachnoid cyst of the diencephalicmembrane of Liliequist, and a communicating cyst that is acystic dilatation of the interpeduncular cistern [8, 9, 11].These are formed in the prepontine space displacing theXoor of the third ventricle upward, the pituitary stalk andoptic chiasm upwards and forwards, and the mamillarybodies upwards and backwards.

Fig. 1 Midline sagittal MRI scan showing a large suprasellar arach-noid cyst. 1 Optic chiasm, 2 pituitary stalk, 3 mamillary body, 4 aque-duct of Sylvius, 5 arachnoid cyst

Fig. 2 Endoscopic superior views into the arachnoid cyst (left) and corresponding drawings (right). 1 Tubercullum sellae, 2 dorsum sellae, 3 pituitary stalk, 4 diaphragm sellae, pituitary gland; 5 roof of left cavernous sinus, 7 anterior intercavernous sinus, 8 left supracavernous internal carotid artery

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Suprasellar arachnoid cyst may be asymptomatic or maycause headache, optic nerve compression, endocrine dys-function or hydrocephalus [4, 9–12].

MRI is usually the examen of choice in preoperativediagnosis. Sagittal slices show the cyst, the Xoor of the thirdventricle, the aqueduct, and the position of the pituitarystalk [4, 7, 9].

DiVerential diagnosis includes cystic craniopharyngio-mas, epidermoid tumors, inXammatory cysts, and obstruc-tive hydrocephalus secondary to aqueduct stenosis.Generally, anatomical characteristics and diVerences of sig-nal on MRI allow a precise diagnosis.

DiVerent techniques have been described to relieve themass eVect of these cysts: direct craniotomy, conventionalshunting, stereotactic puncture and endoscopic fenestration[3, 7, 9, 10].

Two types of endoscopic fenestration are described inthe literature. The Wrst one is a ventriculocystostomy [3,7]. This technique consists of creating a large fenestra-

tion in one of the cyst’s wall, most often the superiorone.

The second one is a ventriculocystocysternostomy [5, 6,11]. This technique consists of creating a second fenestra-tion in the lower wall of the cyst, usually connecting to pre-pontine cistern. Flow dynamic studies suggested theventriculocystocysternostomy as the optimum treatment forthis pathology [6], even if Buxton’s experience [3] does notconWrm the need to open the Xoor of the cyst. AnatomicalWndings note the Xoor of the cyst is a vascular structure andis very diYcult to recognize it. It seems unwise to open theXoor of the cyst. The ventriculocystostomy is a safe tech-nique avoiding the risk of damage to vital structures with agood postoperative outcome [3]. We usually perform a ven-triculocystocysternostomy when there is enough distancebetween basilar artery and clivus or dorsum sellae, if not,we realize a ventriculocystostomy.

We normally use a rigid rod lens endoscope, which hassuperior optical quality if compared to a Xexible one.

Fig. 3 Endoscopic superior views into the arachnoid cyst (left) and corresponding drawings (right). 2 Dorsum sellae, 3 pituitary stalk, 4 diaphragm sellae, pituitary gland; 6 temporal lobe, 8 left supracavernous internal carotid artery, 10 posterior communicant artery (b left), 11 left optic tract, 12 third cranial nerve (b left)

Fig. 4 Endoscopic superior views into the arachnoid cyst (left) and corresponding drawings (right). 2 Dorsum sellae, 3 pituitary stalk, 4 diaphragm sellae, pituitary gland; 9 basilar artery, 10 poster-ior communicant artery, (a right), 12 third cranial nerve (a right), 13 right fourth cranial nerve, 14 slit valve of arachnoid cyst

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Until today, only three authors have described the insideaspects of an arachnoid cyst and vital structures which sur-round it, viewed during an endoscopic procedure. Buxtonet al. [3] were able to identify the basilar artery, the pituitarystalk and the mamillary bodies. Decq et al. [6] and Santam-arta et al. [11] noted the whole posterior part of the circle ofWillis, common oculomotor nerves, protrusion of the clivusand the pituitary. During our endoscopic procedure, theanatomical view of the skull base was demonstrative. Theslow but progressive increase of the cyst allowed a naturaland anatomical dissection of the suprasellar area. Anatomi-cal structures were morphologically normal but pusheddown by the cyst. The slit valve in the wall of the cyst waseasily identiWed and was located in the arachnoid cistern ofthe basilar artery, opening with the arterial inXow [11].

Conclusions

Endoscopic treatment of suprasellar arachnoid cysts byventriculocystostomy is a minimally invasive, safe andeYcacious treatment for these lesions. During thisapproach, a good view on anterior and medial cranial basecan be obtained.

References

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2. Bright R (1831) Serous cysts in the arachnoid. In: Report of med-ical cases selected with a view of illustrating the symptoms andcure of diseases by a reference to morbid anatomy; vol II: diseasesof the brain and nervous system. Langman, Rees, Orme, Brown,Green and Highley, London, pp 437–439

3. Buxton N, Vloeberghs M, Punt J (1999) Flexible neuroendoscopictreatment of suprasellar arachnoid cysts. Br J Neurosurg 13:316–318

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8. Garcia Bach M, Isamat F, Vila F (1988) Intracranial arachnoid cystin adult. Act Neurochir Suppl 42:205–209

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10. Pierre-Kahn A, Capelle L, Brauner R, Sainte Rose C, Renier D,Rappaport R, Hirsch JF (1990) Presentation and management ofsuprasellar arachnoid cyst. J Neurosurg 73:355–359

11. Santamarta D, Aguas J, Ferrer E (1995) The natural history ofarachnoid cyst: endoscopic and cine mode MRI evidence of a slitvalve mechanism. Minim Invasive Neurosurg 38:133–137

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