Rey. Argent. Neuroc. 2004, 18 (S2): 10

ENDOSCOPIC TREATMENT OF POSTERIOR FOSSA
ARACHNOID CYSTS
Yusuf Ersahin
Division of Pediatric Neurosurgery Ege University Faculty of Medicine Izmir,Turkey

ABSTRACT
Objectives. The aim of this paper is to present the results of endoscopic intervention in
retrocerebellar arachnoid cysts.
Material and methods. The patients with posterior fossa arachnoid cysts in which
neuroendoscopic intervention had been done between 2000 and 2004 were retrospectiyely reviewed. Age, gender, presenting symptoms and signs, radiologicalfindings andprevious modes of treatment were evaluated. A rigid neuroendoscope was used in ahl
procedures.
Results. There were 6 boys and 3 girls who ranged in age from 1 month to 16 years(mean 29.9 months). Endoscopic cystfenestration was successful in 7 of 9 patients. Of
the 4 patients who had been previously shunted, 3 became shunt free.
Conclusion. Endoscopic cysto-cistemostomy should be the first step in the managementof posterior fossa arachnoid cyst in the institutions where neuroendoscopy is routinelypracticed.
Key words: neuroendoscopy, arachnoid cyst. posterior cranialfossa

INTRODUCTION
Arachnoid cysts are usually developmental lesions, which may occur wherever cerebrospinal
fluid (CSF) and arachnoid membranes are present. There are different opinions on the management of intracranial arachnoid cysts in terms ofboth the surgical indications and the mode ofsurgical intervention. The aim of this paper is topresent the results of endoscopic intervention in
retrocerebellar arachnoid cysts.
MATERIAL AND METHODS
The patients with posterior fossa arachnoid
cysts in which a neuroendoscopic intervention

Correspondencia: Division of Pediatric Neurosurgery, Ege
University Faculty of Medicine Bornova, Izmir 35100 Turkey
E-mail: ersahin@med .ege . edu.tr

had been done between 2000 and 2004 wereretrospectively reviewed. The patients with quadrigeminal plate, cerebello-pontine angle and clival arachnoid cysts were excluded. Age, gender,
presenting symptoms and signs, radiological findings and previous modes of treatment were evaluated. A rigid neuroendoscope was used in ahl
procedures.
When the patient's symptoms and signs have
improved and the patient has not needed further surgeries such as shunting or open surgery, the endoscopic intervention was considered as successful.
The diagnosis of arachnoid cyst was made bymagnetic resonance imaging (MRI) in ahl patients. Patients had a computed tomography(CT) within several hours after endoscopic surgery to rule out complications. Postoperative
T2-weighted MRI was done to show signal voids
through opening between the cisterna magna
and cyst (Fig. 1).

VOL 18, 2004

11

POSTERIOR FOSSA ARACHNOID CYSTS

Fig. 1. A. Preoperative TIweighetd sagittal MRI
showing retrocerebellar arachnoid cyst. B. Note theflowvoid (arrow) through cystocisternostomy on postoperative T2-weighted sagittal
MRI.

TechniqueMl patients were operated on under generalanesthesia in prone position. A vertical paramedian skin incision, 3-4 cm in length is done in thesuboccipital region. The side in which the arachnoid cyst is larger was used. A very small
craniotomy (1.5 cm x 2 cm) below the transverse
sinus is performed, since a small burr hole does
hinder the rigid neuroendoscope from moving
obliquely and accessing the cisterna magna. Thedura is linearly incised and zero degree straightforward rigid neuroendoscope (Karl Storz, Tutlingen, Germany and Channel Neuroendoscope,Medtronic, Minneapolis, MN) is inserted into thecyst after the cyst is punctured. A cysto-cisternostomy is performed between the cyst and cisterna magna. The lower cranial nerves and thespinal cord are visualized (Fig. 2). At the end of
the procedure the dural incision is either primarily sutured or grafted with a collagen matrix(DuraGen, Integra LifeSciences Corporation, New
Jersey, U.S.A.)
RESULTS

Fig. 2. (A. Endoscopic photograph showing the cerebellar
hemispheres and inferior border of the cyst. B. Bipolar
coagulation of the inferior wall of the cyst. C. Balboa
dilatation of the fenestration. D. Fenestration of theinferior cyst wall (cysto-cisternostomy). E. Visualizationof the lower cranial nerves and the spinal cord by therigid neuroendoscope.

Nine patients with posterior fossa arachnoid
cyst underwent an endoscopic procedure. Sixboys and 3 girls ranged in age from 1 month to16 years (mean 29.9 months) (Table 1). In 3
patients, posterior fossa cyst was diagnosed byultrasound before birth. Five patients were delivered by cesarean section and 4 had a normal
vaginal delivery.
Macrocrania was the most common presenting symptom and sign. Ml patients had a noncommunicating hydrocephalus. Four patients
who had been previously shunted at another12Y. ERSAHIN

REV. ARGENT. NEUROC.

Table 1: Summary of the patients with retrocerebellar arachnoid cysts.
Complications

Case

GenderAge

Symptoms
and signs

Previous
treatment

Endoscopic
procedure

1

Boy

16 y.

Headache, vomiting,papilledema

VP shunt

Cystocisternostomy

Successful2Girl

4.5 m.

Macrocrania

CystocisternostomySuccessful

3Boy

3 m.

Macrocrania, bulging
fontanelle

Cystocisternostomy

4Boylm.

Macrocrania

Cystocisternostomy

5Boy

2 m.

Macrocrania, bulging fontanelle

6Boy

4 y.

Somnolence, ataxia
and opisthotonus

7Boy

13 m.

Bulging fontanelle andpsychomotor retardation

8Girl

1.5 m.

Macrocrania

9*Girl

4.5 m.

Macrocrania andvomiting

CP shunt

CP shunt

VP shunt

Cystocisternostomy

Subcutaneous
CSF collection

OutcomeFailedCP shunt
Successful

CSF fistula

Failed open ssurgery-Cpshunt

Cystocisternostomy

Successful

Cysto-Successful

Cystocisternostomy

SuccessfulCystocisternostomy*

Subcutaneous
CSF collection

Successful

VP: ventriculo-peritoneal, CP: cysto-peritoneal, *: repeat endoscopic procedure.

hospital, presented with headache, vomiting or
symptoms of intracranial hypertension at thetime of shunt malfunction. Ventriculo-peritoneal (VP) shunt and cysto-peritoneal (CP) shunt
had been inserted in 2 and 2 patients, respectively. In one of the patients, we had to reinsert
a CP shunt, following both endoscopic fenestration and cyst excision by open surgery. When
this patient had been on external drainage before open surgery, more than 750 ml CSF per day
were excreted to the drainage bag.
A repeat endoscopic fenestration was performed in one of the patients almost 2 years after
the initial endoscopic intervention. Of the 4patients with shunts, 3 became shunt free.
Endoscopic cyst fenestration was successful in
7 of 9 patients. Postoperative subcutaneous
CSF collection and fistula occurred in two andone patient, respectively. Two of the 3 patientswith complication did not benefit from endoscopic cyst fenestration. A reduction in cyst size invarying degrees and a signal void through fenestration between the cisterna magna and cyst
were shown on the postoperative MRI scans of
the 7 patients (Fig. 3). In 2 patients, there was nochange in cyst volume and ventricular dilatation increased and a CP shunt was inserted. The
follow-up ranged from 3 to 51 months (mean26.4 months).

Fig. 3. A. Preoperative Tl-weighted MRI scans showing
a retrocerebellar arachnoid cyst. B. Postoperatíve
showing a reduction in the cyst volume and some
expansion of the cerebellar hemispheres.

POSTERIOR FOSSA ARACHNOID CYSTS

VOL 18, 2004

DISCUSSION
Arachnoid cysts are occasionally encounteredin the posterior fossa. Infratentorial arachnoid
cysts may be retrocerebellar, supravermian (supracollicular) or in the cerebellopontine anglel'2.
However, we included only retrocerebellar arachnoid cyst in this series. Megacisterna magna,
Dandy-Walker syndrome, cerebellar hypoplasia,
hydrocephalus in the presence of a non-spaceoccupying retrocerebellar CSF collection, dermoid
or epidermoid cysts, cystic cerebellar astrocytoma
and cerebellar hemangioblastoma should be taken
into consideration in differential diagnosis1 .
Galassi et al6 reported that posterior fossa arachnoid cysts affect males more than females andmay become symptomatic at any age and a historyof a difficult or traumatic delivery was present inhalf of the cases. Six of the nine children were malein our series and ahl presented with hydrocephalus in their infancy. There were eight female andfour male patients in the series of Samii et al7. No
sex difference has been reported by others3. Posterior fossa cyst was diagnosed prenatally in 3 of
the 9 patients and five patients were delivered bycesarean section and 4 had a normal vaginaldelivery.
Endoscopic treatment of arachnoid cysts has
been infrequently reported 8-14. Endoscopic treatment of midline supratentorial arachnoid cysts
such as suprasellar arachnoid cyst has been
accepted as a choice of treatment by most of theneurosurgeons8,10,14-17. However, the experienceon the endoscopic treatment of arachnoid cysts inthe posterior fossa is limited. Schroeder et all4
performed endoscopic cysto-cistemostomy in 2
patients with posterior fossa arachnoid cysts andthe clinical improvement and cyst reduction wereachieved in both patients. Hopf and Perneczky10
endoscopic neurosurgery in 2 and endoscopeassisted microneurosurgery in 1 patient with retrocerebellar arachnoid cysts. Of 3 patients, 2
improved clinically although cyst reduction wasdetermined in only one patient. However, theyreported that the best success rates were achievedin patients with intraventricular cysts (89%) andposterior fossa arachnoid cysts (78%) including
quadrigeminal, cerebellopontine angle, supra andretrocerebellar cysts. Choi et al8 carried out cystocisternostomy in 5 arachnoid cysts in the posterior fossa and cyst reduction was achieved in 3.
They did not find any case of reclosure of thefenestration site in any of the patients who underwent successful endoscopic procedure without

13

hemorrhage or infection in a series of 36 patientswith congenital arachnoid cysts. They also thinkthat reclosure of the fenestration site may berelated to hemorrhage or infection8.
In the series of 7 patients with arachnoid cysts
reported by Kim'1 , the cerebellar arachnoid cyst
disappeared following endoscopic fenestration.
Gangemi et al9 reported a successful result in 2
patients with posterior fossa arachnoid cyst inwhich endoscopic cyst fenestration and endoscope-assisted microneurosurgery had been done. A
32-year-old with an arachnoid cyst of the posterior fossa manifesting as cervical syringomyelic
myelopathy improved following endoscopic cyst
fenestration. The inferior wall of the cyst was
disturbing CSF pulsatile movement between theintraspinal and intracranial subarachnoid spaces12. The symptoms and signs of intracranial
hypertension were relieved by endoscopic cystfenestration in 7 of the nine patients with aretrocerebellar arachnoid cyst in our series. Oneof the patients had a repeat endoscopic cystocistemostomy. This patient had had shunt infection before the first endoscopic procedure wasdone. The other patient in whom the endoscopic
cyst fenestration failed had been previously shunted. He had CSF fistula through the skin incision
after the endoscopic cyst fenestration and an
external drain was inserted in the cyst because ofinfection. The daily amount of CSF, drained in thedrainage bag was greater than 750 ml. Althougha cyst excision was performed by craniotomy, heneeded a CP shunt. CSF production by enclosed
ectopic choroid plexus is one of the mechanismsof cyst growth1839. Such a mechanism may account for a high rate of CSF production in ourpatient.
No major complication following endoscopic
surgery in posterior fossa arachnoid cysts has
been reported8-12,14. The complications of open
surgery are more frequent and severe20-22. However, open surgery and radical removal of thearachnoid cyst in the posterior fossa can be safeand effective in experienced hands3'7. Shunt surgery has no mortality and very low complication
rate. A marked reduction in cyst size is almost
always seen on CT or MRI after shunting21,23.
Shunt dependency and complications are inevitable in the long term24.
The number of the cases who underwent endoscopic cyst fenestration is small. We need tohave a larger number of patients to prove theeffectiveness of endoscopic intervention in posterior fossa arachnoid cysts. However, the results of14Y. ERSAHIN

endoscopic surgeries reported in the literature sofar are promising. Endoscopic cysto-cistemostomy should be the first step in the managementof posterior fossa arachnoid cyst in the institutions where neuroendoscopy is routinely practiced.
References
1. Boltshauser E, Martin F, Altermatt S: Outcome inchildren with space-occupying posterior fossa arachnoid cysts. Neuropaediatrics 2002; 33: 118-21.
2. Naidich TP, McLone DG, Radkowski MA. Intracranial arachnoid cysts. Pediatr Neurosci 1985-86;
12: 112-22.
3. Erdincler P, Kaynar MY, Bozkus H, Ciplak N.
Posterior fossa arachnoid cysts. Br J Neurosurg
1999; 13: 10-17.
4. Gosalakkal JA: Intracranial arachnoid cysts inchildren: A review of pathogenesis, clinical features, and management. Pediatr Neurol 2002; 26:93-8.
5. Rock JP, Zimmerman R, Bell WO, Fraser RAR:
Arachnoid cysts of the posterior fossa. Neurosurgery 1986; 18: 176-9.
6. Galassi E, Tognetti F, Frank F, Fagioli L, Nasi MT,Gaist G. Infratentorial arachnoid cysts. J Neurosurg 1985; 63: 210-7.
7. Samii M, Carvalho GA, Schuhmann MU, Matthies
C: Arachnoid cysts of the posterior fossa. Surg
Neurol 1999; 51: 376-82.
8. Choi JU, Kim DS, Huh R: Endoscopic approach toarachnoid cyst. Childs Nerv Syst 1999; 15: 28591.
9. Gangemi M, Maiuri F, Colella G, Sardo L: Endoscopic surgery for large posterior fossa arachnoid cysts.
Minim Invasive Neurosurg 2001; 44: 21-4.
10. Hopf NJ, Perneczky A: Endoscopic neurosurgery
and endoscope-assisted microneurosurgery for thetreatment of intracranial cysts. Neurosurgery 1998;
43: 1330-6.
11. Kim M-H: The role of endoscopic fenestration procedures for cerebral arachnoid cysts. J Korean
Med Sci 1999; 443-7.
12. Nomura S, Akimura T, Imoto H, Nishizaki T, Suzuki M: Endoscopic fenestration of posterior fossaarachnoid cyst for the treatment of presyrinx mye-REV. ARGENT. NEUROC.

lopathy-case report. Neurol Med Chir (Tokyo)
2002; 42. 452-4.
13. Schónherr B, Wolf O, Meier U: Endoscopy of intracranial cyst in the adult patient. Minim Invasive
Neurosurg 2002; 45: 181-4.
14. Schroeder HW, Gaab MR, Niendorf WR: Neuroendoscopic approach to arachnoid cysts. J Neurosurg 1996; 85: 293-8.
15. Caemert J, Abdullah J, Calliauw L, Carton D,Dhooge C, van Coster R. Endoscopic treatment ofsuprasellar arachnoid cysts. Acta Neurochir (Wien)
1992; 119: 68-73.
16. Decq P, Brugiéres P, Le Guerinel C, Djindjian M,Kéravel Y, Nguyen J-P: Percutaneous endoscopic
treatment of suprasellar arachnoid cysts: ventriculocystostomy or ventriculocystocistemostomy? Technical note. J Neurosurg 1996; 84 :696-701.
17. Kirollos RW, Javadpour M, May P, Mallucci C:
Endoscopic treatment of suprasellar and thirdventricle-related arachnoid cysts. Child's Nerv
Syst 2001; 17: 713-8.
18. Iglesias JR, Sanjuanbenito L, Martinez-Cubells J,Lousa M, Redondo C: Intracerebral arachnoidal
cyst containing choroid plexus. Case report. Acta
Neurochir (Wien) 1981; 58: 229-34.
19. Schuhmann MU, Tatagiba M, Hader C, Brandis A,Samii M: Ectopic choroid plexus within a juvenile
arachnoid cyst of the cerebellopontine angle: causeof cyst formation or reason of cyst growth. Pediatr
Neurosurg 2000; 32: 73-6.
20. Aoki N, Sakai T: Intraoperative subdural hematoma in a patient with arachnoid cysts in the middle
cranial fossa. Child's Nerv Syst 1990; 6: 44-6.
21. Ciricillo SF, Cogen PH, Harsh GR, Edwards MSB:
Intracranial arachnoid cysts in children. A comparison of the effect of fenestration and shunting. JNeurosurg 1991; 74: 230-5.
22. Stein SC: Intracranial developmental cysts in children. treatment by cystoperitoneal shunting. Neurosurgery 1980; 8: 647-50.
23. McBride LA, Winston KR, Freeman JE: Cystoventricular Shunting of Intracranial Arachnoid Cysts.
Pediatr Neurosurg 2003; 39: 323-9.
24. Kim S-K, Cho B-K, Chung Y-N, Kim H-S, Wang KC: Shunt dependency in shunted Arachnoid cyst:a reason to avoid shunting. Pediatr Neurosurg
2002; 37: 178-85.

RESUMEN
Objetivo. Presentar los resultados del tratamiento endoscópico de los quistes aracnoideos de la fosa posterior.
Material y método. Se revisan las historias de pacientes
tratados entre los años 2000 y 2004 evaluando edad,sexo, hallazgos radiológicos y tratamiento previo. En
todos los procedimientos se utilizó un endoscopio rígido.
Resultados. Encontramos 6 niños y 3 niñas (edadpromedio 29,9 meses) La fenestración endoscópica delos quistes fue útil en 7 de los 9 pacientes. De los 4pacientes a los que se había implantado válvulas previamente, 3 no requirieron derivación.
Conclusión. El tratamiento endoscópico de los quistes
aracnoideos de la fosa posterior debe ser el de primera
opción en las instituciones que hagan esta práctica derutina.
Palabras clave: fosa posterior, neuroendoscopia, quiste aracnoideo