:Acta
Acta Neurochir (Wien) (1992) 119:68-73
N6urochlrurgica 9 Springer-Verlag1992 Printed in Austria
Endoscopic Treatment of Suprasellar Arachnoid Cysts J. Caemaert 1, J. Abdullah 1, L. Calliauw 1, D. Carton 2, C. Dhooge 2, and R. van Coster 2 ~Department of Neurosurgery and 2Department of Pediatry, University Hospital, Ghent, Belgium
Summary Four cases of large suprasellar arachnoid cysts in children are described. The authors propose a large fenestration into the lateral ventricles and into the basal cisterns as the treatment of choice. A specific multipurpose cerebral endoscope has been designed by the first author. The endoscopic technique with different instruments and with the use of a laser is illustrated. Results and complications are discussed.
Keywords." Suprasellar cysts; cerebral endoscopy; Nd-Yag laser; hydrocephalus. Introduction Large suprasellar arachnoid cysts as the cause of hydrocephalus in children were seldom diagnosed in the past. Since the use of CT and M R I imaging they are being recognized with increasing frequency 2' 6, 9, 13, 15, 21, 25. A typical Mickey-Mouse appearance is described according to the location, shape and CT-attenuation patterns. In most cases a very pronounced
dilatation of the lateral ventricles is present. A large oval or round cystic formation (Fig. 1) is seen at the site of the third ventriclc which itself is displaced posteriorly and sometimes remains discernible on M R I as a small cleft. Various open surgical methods have been proposed, consisting mainly of subfrontal, subtemporal or transcallosal approaches to the cyst 1' 11,16-18, 20. Ventriculoatrial or ventriculo-peritoneal shunts have also been inserted, in the main with unsatisfactory results. Pierre K a h n presents an excellent review of clinical and paraclinical aspects 18. He reports treatment of four patients under endoscopic control with m o n o p o l a r coagulation to perforate the cyst. We prefer to perform a large fenestration of the wail of the cyst towards the lateral ventricle and towards the basal cisterns using the laser. Our endoscopic method and the results are described in this paper.
Fig. I. a) Axial, b) sagittal, c) coronal MRI of large suprasellar arachnoid cysts
J. C a e m a e r t et al.: E n d o s c o p i c T r e a t m e n t of Suprasellar A r a c h n o i d Cysts
Clinical Material and Methods
69
T a b l e 1. Clinical Findings in 4 Patients with Suprasellar Arachnoid
Cysts F o u r children p r e s e n t e d w i t h progressive clinical d e t e r i o r a t i o n due to p r o n o u n c e d h y d r o c e p h a l u s c a u s e d by a large suprasellar a r a c h n o i d cyst. The clinical picture is s u m m a r i z e d in T a b l e 1. T w o boys and two girls were t r e a t e d between D e c e m b e r 88 a n d F e b r u a r y 92. The ages were: 3.5, 9.5, 4.5, a n d 18 years. H e a d a c h e a n d inatt e n t i o n were s y m p t o m s c o m m o n to all of them. The m o s t characteristic n e u r o l o g i c a l signs were d y s m e t r i a a n d h e a d b o b b i n g a l t h o u g h the latter s y m p t o m is described in the l i t e r a t u r e in o n l y 10%; it is due to c o m p r e s s i o n of the d o r s o m e d i a l nucleus o f the t h a l a m u s 3' 7, I2, 22
Operative Technique Endoscopic neurosurgery should, according to our experience, always be carried out under general anaesthesia because, when done under local anaesthesia, severe vomiting invariably occurs due to the rinsing of the ventricles with normal saline. Even at low pressures, rapid changes in ICP always cause disturbing vomiting. A multipurpose endoscope has been designed by the first author 5. The instrument was realized by Wolf, Belgium (Drongen), and Wolf, Germany (Knitlingen), and nowadays the fourth prototype is in use (Fig. 2). There are four channels in the long rigid shaft which permit looking, working and rinsing at the same time. A small videocamera is attached to the ocular of the optic element and the surgeon works looking on the video monitor screen.
Pat. 1
Pat. 2
Sex
V.D.H.W. F
D.V.M.S.S. M M
V.S. F
Age at p r e s e n t a t i o n
18
9.5
4.5
3.5
H e a d circumference > P97 Headache
+ +
+ + +
+ +
P50 +
Vomiting Muscular weakness Inattention
+ + +
. +
-
+
Seizures Mental Retardation
+ +
Headbobbing Intention tremor Dysmetry
Patient
Pat. 3 Pat. 4
General symptoms
.
.
. +
+
-
-
-
+ + +
+ + +
+ +
+ + -
+ + +
+ +
-
-
Neurological findings
Ophthalmological examination Altered vision P a r a l y s i s of u p w a r d gaze Optic atrophy Endocrine dysfunction
Three children underwent stereotactically guided endoscopic exploration, the fourth exploration was done free-hand. Through a coronal burr-hole the endoscope was introduced into the right lateral ventricle. This
Fig. 2. a) C e r e b r a l endoscope, b) several i n s t r u m e n t s can be i n t r o d u c e d a t the s a m e time t h r o u g h two or three o f the four c h a n n e l s
70
J. Caemaert etal.: EndoscopicTreatment of SupraseUar Arachnoid Cysts a) Simple perforation of the cyst membrane by means of a blunt Fogarty balloon catheter is impossible. It slides tangentially and does not permit perforation. This is the reason why shunting procedures often fail. b) A stiff polyurethane catheter with a sharpened tip permits penetration. The floppy waving movement of the membrane proves that tension of the cyst has been relieved, but we felt that this manoeuvre produced too great a danger of bleeding.
Fig. 3. Cyst wall with small blood vessels on the bluish dome allowed visualisation of the grey- or bluish translucent cyst-wall, which resembles thickened arachnoid (Fig. 3). Numerous small blood vessels are often visible in the wall of the cyst. A more or less avascular area is selected for the fenestration. We successively tried different perforation techniques:
c) Therefore, bipolar coagulation of the wall (Fig. 4 a) and perforation with the Fogarty catheter has been tried. During coagulation some shrinkage of the membrane can be seen. A balloon catheter is inserted through the cyst-wall. Then it is inflated and retracted in order to enlarge the opening (Fig. 4 b). It may be inflated either within or through the first opening and then retracted. Sometimes the vascular pattern on the opposite inner wall of the cyst can be very different from that of the outer wall. Bleeding from small blood vessels is easily controlled
Fig.4. a) Bipolar coagulation of the cyst wall, b) serial inflation and retraction of balloon catheter, c) 6ram opening made by Fogarthy balloon catheter, d) hypophysisand surrounding structures at the anterior floor of the cyst
J. Caemaert et al.: Endoscopic Treatment of Suprasellar Arachnoid Cysts
by bipolar coagulation. The original perforation can be enlarged (Fig. 4 c) by several introductions and inflations of the balloon catheter. Introducing the endoscope in the cyst and looking in a downward direction, we have a very unusual view of the suprasellar region. The inferior side of the hypothalamus, the hypophyseal stalk, the pink plate of the hypophysis and the large vessels of the circle of Willis can be seen (Fig. 4 d). Behind the posterior clinoid processes, the basilar artery is the landmark towards the depth of the clivus where the deepest membrane of the cyst is now perforated towards the prepontine cisterns. d) More recently we used a Nd-Yag laser (MBB Medilas 4060) in the fibertome mode with feedback control over the temperature of the probe tip for cutting and coagulation. This allows a very safe, easy and rapid fenestration of the cyst walls. Only the vessels need to be coagulated (Fig. 5 a) after which the cutting probe is used to make a large hole (Fig. 5 b). To avoid the resected membrane falling into the ventricle with the risk of aqueduct obstruction, the last attachment of the resected piece is finally avulsed by a grasping forceps. An important detail is that the head should always be positioned in such a way that the burr hole is the highest point. In this position the air that entered the ventricle during the procedure can escape when rinsing the ventricles with normal saline.
71
Before the use of the laser we were not able to obtain parts of the cyst walls large enough for microscopic examination. Now we are grasping the cut-out membrane and it showed in case four a single membrane consisting of laminated collagen bundles. The outer surface was composed of mesothelial baseline cells covering normal arachnoid. Our biopsies are taken from the roof of these cysts. A study on cerebral subarachnoid cysts 14'23 showed that the roof of the cysts consists largely of laminated collagen bundles with elasten and reticulin fibres. At the junction of the roof and the wall of the cysts this membrane divides into two layers, an outer layer covers the cortical surface in continuity with the arachnoid membrane and the inner layer is passing centrally to make the wall and floor of the cysts. The arachnoid and pia mater cover the base of the cysts. Small blood vessels are present between the cysts and cortex. More glial cells are seen on histopathological examination where the cysts compress the cortex. These cysts can also be intraarachnoid cysts when they are totally enclosed by arachnoid membrane without pia mater. Neuro-epithelial cysts or ependymal cysts are paraventricular cysts lined with ependyma. Systematic examination of membranes will be performed in future cases.
Results
Pathology Already during the endoscopy we could see that there are different pathological types. Sometimes for example the hypophysis and surrounding circle of Willis arteries are entirely naked and sometimes they are covered by a very thin milky white membrane.
The four children were able to be discharged from the hospital 2 days after the intervention. They showed a marked improvement of their clinical status; the head bobbing, tremor and dysmetria had disappeared completely. In one girl the mental retardation and the hormonal disturbances remained unchanged.
Fig. 5. a) Laser coagulation of blood vessels on the cyst wall, b) cutting out with the laser of a rounded window in the membrane
72
J. Caemaert et al.: Endoscopic Treatment of Suprasellar Arachnoid Cysts
Fig. 6. Reductionof cyst volumeand hydrocephalusin two cases. (a, b) Pre-operatively,(c, d) five months after the operation Check CT-scans five months after the operation showed marked reduction in size of the cyst (Fig. 6) and the re-expansion of the thalamic region. We also noticed a reduction of the hydrocephalus without slit ventricle syndrome or subdural collections as may be seen after ventriculo-atrial or peritoneal shunting with overdrainage. In case four a second endoscopic intervention was necessary on the contralateral side, after 5 months, because on a check CT-scan we noted a re-expansion of the cyst volume after an initial marked reduction; the child was still in a good clinical condition. After this second intervention the cyst remained reduced. To date none of these children have needed an extracranial shunting procedure. The follow-up periods were respectively 36, 20, 20 and 7 months (2 months for the second operation in case 4). A longer period is necessary to prove the long term success of the method. In the future, dynamic M R I studies will be done to prove the restoration of normal flow of the CSF through the ventricle, the cyst and the basal cisterns. There was no operative mortality. The morbidity was limited to one epileptic attack in one child, six hours after the intervention; there was full recovery. Prophylactic antibiotics have always been given for 24 hours (amoxicilline trihydrate and potassium-clavulanate). Discussion
Pathogenesis Different hypotheses have been proposed concerning the genesis of arachnoid cysts4' 10, 11, 13, 24. One of them is the existence of a slit valve mechanism, a!though
nobody has ever seen such a valve. In a parasellar cyst we detected such a slit-valve in a membrane through which the oculomotor nerve and branches of the middle cerebral artery were discernable. This cleft opens at each inspiration and closes at expiration. By means of the balloon catheter and the grasping forceps we have destroyed this slit valve so that the cerebrospinal fluid could flow freely from the basal cisterns around the circle of Willis and vice versa. We now prefer a combination of this method with the use of a cutting laser, so that excessive traction on these membranes can be avoided. Following the clivus of Blumenbach in another case a slit-valve like structure was detected in a membrane surrounding the basilar artery. This opens and closes rapidly with arterial pulsations and might be related to the mechanism of the cyst enlargement 24. This structure was also opened widely.
Operative Technique Endoscopic laser fenestration of the wall of large suprasellar arachnoid or ependymal cysts has been an efficient treatment in four children. Treatment with ordinary ventriculo-atrial or peritoneal shunting is nearly always inefficient, even when a ventricular drain is inserted bilaterally. The cyst itself remains distended and continuing damage to the thalamic, hypothalamohypophyseal and optic structures occurs. Some surgeons proposed stereotactic insertion of a ventricular catheter into the cyst, connected as a supplement to the ventricular drainage. This logical solution however is fraught with difficulties and failures. The wall of these cysts is often quite tough and the catheters tend to deviate tangentially without penetration.
J. Caemaert etal.: Endoscopic Treatment of Suprasellar Arachnoid Cysts W e therefore prefer to open the cyst widely b y a n endoscopic fenestration in the wall into the lateral ventricle. This c o m m u n i c a t i o n should be as large as possible (10-15 m m ) to p r e v e n t secondary closing. A n o t h e r very i m p o r t a n t m e a s u r e to p r e v e n t recurrence of the d i l a t a t i o n is to m a k e at least two openings in the wall, one into the lateral ventricle, the other one into the basal p r e p o n t i n e cisterns. T h u s we establish a c o n s t a n t C S F flow t h r o u g h the cyst. The walls become floppy a n d instead of the oval or r o u n d distention, a tent-like structure r e m a i n s a n d the c o m p r e s s i o n o n the surr o u n d i n g structures disappears. Since the cause o f the h y d r o c e p h a l u s is treated, n o further d r a i n a g e is needed in those cases where the resorptive capacities have rem a i n e d intact. W h e n these capacities are d i s t u r b e d a s h u n t i n g procedure will be necessary b u t prior to shunting a fenestration of the cyst should be carried out. The technique was c o n s t a n t l y developing till at last the c o a g u l a t i n g a n d cutting laser p r o v e d to be the safest a n d easiest tool.
References I. Albright L (1981) Treatment of Bobble-Head Doll syndrome by transcallosal cystectomy. Neurosurgery 8:593-595 2. Banna M (1974) Arachnoid cysts in the hypophyseal area. Clin Radio1 25:323-326 3. Benton JW, Nellhaus G, Huttenlocher PR, et al (1966) The bobble-head doll syndrome. Report of a unique truncal tremor associated with third ventricular cyst and hydrocephalus in children. Neurology 16:725-729 4. Binitie O, Williams B, Case CP (1984) A suprasellar subarachnoid pouch: aetiological considerations. J Neurot Neurosurg Psychiatry 47:1066-1074 5. Caemaert J, Abdullah J, Calliauw L (1992) Reflections on techniques and instrumentation in endoscopic neurosurgery. Reporting MIN II Marburg. Acta Neurochir (Wien) [Suppl] (submitted) 6. Danziger J, Bloch S (1974) Suprasellar arachnoid pouches. Br J Radioi 47:448-451 7. Ferry PC, Feldman V, Kerber C (1974) The bobble-head syndrome due to a basal arachnoid cyst. Neurology 24:394 8. Gentry LR, Smoker WR, Turski PA, etal (1986) Suprasellar arachnoid cysts. CT recognition. AJNR 7:79-86
73
9. Gonzalez CA, Villarejo FJ, Blazquez MG, etal (1982) Suprasellar arachnoid cysts in children. Report of three cases. Acta Neurochir (Wien) 60:281-296 I0. Harrison MJG (1971) Cerebral arachnoid cysts in children. J Neurol Ncurosurg Psychiatry 34:316-323 11. Hoffman HJ, Hendrick EB, Humphreys RP, et al (1982) Investigation and management of suprasellar arachnoid cysts. J Neurosurg 57:597-602 12. Jensen JP, Pendl G, Goerke W (1978) Head bobbing in a patient with a cyst of the third ventricle. Childs Brain 4: 235-24l 13. Kasdon DL, Douglas EA, Broughan MF (1977) Suprasellar arachnoid cyst diagnosed preoperatively by computerized tomographic scanning. Surg Neurol 7:299-303 14. Krawchenko J, Collins GH (1979) Pathology of an arachnoid cyst. Case report. J Neurosurg 50:224-228 15. Leo JS, Pinto RS, Hulvat GF, etal (1979) Computed tomography of arachnoid cysts. Radiology 130:675-680 16. Murali R, Epstein F (1979) Diagnosis and treatment of suprasellar arachnoid cyst. Report of three cases. J Neurosurg 50: 515-518 17. Obenchain TG, Becker DP (1972) Head bobbing associated with a cyst of the third ventricle. Case report. J Neurosurg 37: 457459 18. Pierre-Kahn A, etal (1990) Presentation and management of suprasellar arachnoid cyst. Review of 20 cases. J Neurosurg 73: 355-359 19. Powers SK (1992) Fenestration of intraventricular cysts using a flexible, steerable endoscope. Acta Neurochir (Wien) [Suppl] 54:42-46 20. Raimondi AJ, Shimoji T, Gutierrez FA (1980) Suprasetlar cysts: surgical treatment and results. Childs Brain 7:57-72 21. Ring BA, Waddington M (1966) Primary araehnoid cysts of the sella turcica. AJR 98:611-615 22. Russo RH, Kindt GW (1974) A neuroanatomical basis for the Bobble-head doll syndrome. J Neurol 41:720-723 23. Starkman SP, Brown TC, Linell LA (1958) Cerebral arachnoid cysts. J Neuropathol Exp Neurol 17:484-500 24. Williams B, Guthkelch AN (1974) Why do central arachnoid pouches expand? J Neurol Neurosurg Psychiatry 37:1085--1092 25. Wirt TC, Hester RW (1977) Suprasellar arachnoid cyst. Surg Neurol 9:322 26. Zamorano L, Chavantes C, Dujovny M, Malik G, Ausman J (1992) Stereotactic endoscopic interventions in cystic and intraventricular brain lesions. Acta Neurochir (Wien) [Suppl] 54: 69-76 Correspondence and Reprints: Dr. J. Caemaert, Department of Neurosurgery, University Hospital, De Pintelaan 185, B-9000Ghent, Belgium.
Acta Neurochir (Wien) (1992) 119:68-73
N6urochlrurgica 9 Springer-Verlag1992 Printed in Austria
Endoscopic Treatment of Suprasellar Arachnoid Cysts J. Caemaert 1, J. Abdullah 1, L. Calliauw 1, D. Carton 2, C. Dhooge 2, and R. van Coster 2 ~Department of Neurosurgery and 2Department of Pediatry, University Hospital, Ghent, Belgium
Summary Four cases of large suprasellar arachnoid cysts in children are described. The authors propose a large fenestration into the lateral ventricles and into the basal cisterns as the treatment of choice. A specific multipurpose cerebral endoscope has been designed by the first author. The endoscopic technique with different instruments and with the use of a laser is illustrated. Results and complications are discussed.
Keywords." Suprasellar cysts; cerebral endoscopy; Nd-Yag laser; hydrocephalus. Introduction Large suprasellar arachnoid cysts as the cause of hydrocephalus in children were seldom diagnosed in the past. Since the use of CT and M R I imaging they are being recognized with increasing frequency 2' 6, 9, 13, 15, 21, 25. A typical Mickey-Mouse appearance is described according to the location, shape and CT-attenuation patterns. In most cases a very pronounced
dilatation of the lateral ventricles is present. A large oval or round cystic formation (Fig. 1) is seen at the site of the third ventriclc which itself is displaced posteriorly and sometimes remains discernible on M R I as a small cleft. Various open surgical methods have been proposed, consisting mainly of subfrontal, subtemporal or transcallosal approaches to the cyst 1' 11,16-18, 20. Ventriculoatrial or ventriculo-peritoneal shunts have also been inserted, in the main with unsatisfactory results. Pierre K a h n presents an excellent review of clinical and paraclinical aspects 18. He reports treatment of four patients under endoscopic control with m o n o p o l a r coagulation to perforate the cyst. We prefer to perform a large fenestration of the wail of the cyst towards the lateral ventricle and towards the basal cisterns using the laser. Our endoscopic method and the results are described in this paper.
Fig. I. a) Axial, b) sagittal, c) coronal MRI of large suprasellar arachnoid cysts
J. C a e m a e r t et al.: E n d o s c o p i c T r e a t m e n t of Suprasellar A r a c h n o i d Cysts
Clinical Material and Methods
69
T a b l e 1. Clinical Findings in 4 Patients with Suprasellar Arachnoid
Cysts F o u r children p r e s e n t e d w i t h progressive clinical d e t e r i o r a t i o n due to p r o n o u n c e d h y d r o c e p h a l u s c a u s e d by a large suprasellar a r a c h n o i d cyst. The clinical picture is s u m m a r i z e d in T a b l e 1. T w o boys and two girls were t r e a t e d between D e c e m b e r 88 a n d F e b r u a r y 92. The ages were: 3.5, 9.5, 4.5, a n d 18 years. H e a d a c h e a n d inatt e n t i o n were s y m p t o m s c o m m o n to all of them. The m o s t characteristic n e u r o l o g i c a l signs were d y s m e t r i a a n d h e a d b o b b i n g a l t h o u g h the latter s y m p t o m is described in the l i t e r a t u r e in o n l y 10%; it is due to c o m p r e s s i o n of the d o r s o m e d i a l nucleus o f the t h a l a m u s 3' 7, I2, 22
Operative Technique Endoscopic neurosurgery should, according to our experience, always be carried out under general anaesthesia because, when done under local anaesthesia, severe vomiting invariably occurs due to the rinsing of the ventricles with normal saline. Even at low pressures, rapid changes in ICP always cause disturbing vomiting. A multipurpose endoscope has been designed by the first author 5. The instrument was realized by Wolf, Belgium (Drongen), and Wolf, Germany (Knitlingen), and nowadays the fourth prototype is in use (Fig. 2). There are four channels in the long rigid shaft which permit looking, working and rinsing at the same time. A small videocamera is attached to the ocular of the optic element and the surgeon works looking on the video monitor screen.
Pat. 1
Pat. 2
Sex
V.D.H.W. F
D.V.M.S.S. M M
V.S. F
Age at p r e s e n t a t i o n
18
9.5
4.5
3.5
H e a d circumference > P97 Headache
+ +
+ + +
+ +
P50 +
Vomiting Muscular weakness Inattention
+ + +
. +
-
+
Seizures Mental Retardation
+ +
Headbobbing Intention tremor Dysmetry
Patient
Pat. 3 Pat. 4
General symptoms
.
.
. +
+
-
-
-
+ + +
+ + +
+ +
+ + -
+ + +
+ +
-
-
Neurological findings
Ophthalmological examination Altered vision P a r a l y s i s of u p w a r d gaze Optic atrophy Endocrine dysfunction
Three children underwent stereotactically guided endoscopic exploration, the fourth exploration was done free-hand. Through a coronal burr-hole the endoscope was introduced into the right lateral ventricle. This
Fig. 2. a) C e r e b r a l endoscope, b) several i n s t r u m e n t s can be i n t r o d u c e d a t the s a m e time t h r o u g h two or three o f the four c h a n n e l s
70
J. Caemaert etal.: EndoscopicTreatment of SupraseUar Arachnoid Cysts a) Simple perforation of the cyst membrane by means of a blunt Fogarty balloon catheter is impossible. It slides tangentially and does not permit perforation. This is the reason why shunting procedures often fail. b) A stiff polyurethane catheter with a sharpened tip permits penetration. The floppy waving movement of the membrane proves that tension of the cyst has been relieved, but we felt that this manoeuvre produced too great a danger of bleeding.
Fig. 3. Cyst wall with small blood vessels on the bluish dome allowed visualisation of the grey- or bluish translucent cyst-wall, which resembles thickened arachnoid (Fig. 3). Numerous small blood vessels are often visible in the wall of the cyst. A more or less avascular area is selected for the fenestration. We successively tried different perforation techniques:
c) Therefore, bipolar coagulation of the wall (Fig. 4 a) and perforation with the Fogarty catheter has been tried. During coagulation some shrinkage of the membrane can be seen. A balloon catheter is inserted through the cyst-wall. Then it is inflated and retracted in order to enlarge the opening (Fig. 4 b). It may be inflated either within or through the first opening and then retracted. Sometimes the vascular pattern on the opposite inner wall of the cyst can be very different from that of the outer wall. Bleeding from small blood vessels is easily controlled
Fig.4. a) Bipolar coagulation of the cyst wall, b) serial inflation and retraction of balloon catheter, c) 6ram opening made by Fogarthy balloon catheter, d) hypophysisand surrounding structures at the anterior floor of the cyst
J. Caemaert et al.: Endoscopic Treatment of Suprasellar Arachnoid Cysts
by bipolar coagulation. The original perforation can be enlarged (Fig. 4 c) by several introductions and inflations of the balloon catheter. Introducing the endoscope in the cyst and looking in a downward direction, we have a very unusual view of the suprasellar region. The inferior side of the hypothalamus, the hypophyseal stalk, the pink plate of the hypophysis and the large vessels of the circle of Willis can be seen (Fig. 4 d). Behind the posterior clinoid processes, the basilar artery is the landmark towards the depth of the clivus where the deepest membrane of the cyst is now perforated towards the prepontine cisterns. d) More recently we used a Nd-Yag laser (MBB Medilas 4060) in the fibertome mode with feedback control over the temperature of the probe tip for cutting and coagulation. This allows a very safe, easy and rapid fenestration of the cyst walls. Only the vessels need to be coagulated (Fig. 5 a) after which the cutting probe is used to make a large hole (Fig. 5 b). To avoid the resected membrane falling into the ventricle with the risk of aqueduct obstruction, the last attachment of the resected piece is finally avulsed by a grasping forceps. An important detail is that the head should always be positioned in such a way that the burr hole is the highest point. In this position the air that entered the ventricle during the procedure can escape when rinsing the ventricles with normal saline.
71
Before the use of the laser we were not able to obtain parts of the cyst walls large enough for microscopic examination. Now we are grasping the cut-out membrane and it showed in case four a single membrane consisting of laminated collagen bundles. The outer surface was composed of mesothelial baseline cells covering normal arachnoid. Our biopsies are taken from the roof of these cysts. A study on cerebral subarachnoid cysts 14'23 showed that the roof of the cysts consists largely of laminated collagen bundles with elasten and reticulin fibres. At the junction of the roof and the wall of the cysts this membrane divides into two layers, an outer layer covers the cortical surface in continuity with the arachnoid membrane and the inner layer is passing centrally to make the wall and floor of the cysts. The arachnoid and pia mater cover the base of the cysts. Small blood vessels are present between the cysts and cortex. More glial cells are seen on histopathological examination where the cysts compress the cortex. These cysts can also be intraarachnoid cysts when they are totally enclosed by arachnoid membrane without pia mater. Neuro-epithelial cysts or ependymal cysts are paraventricular cysts lined with ependyma. Systematic examination of membranes will be performed in future cases.
Results
Pathology Already during the endoscopy we could see that there are different pathological types. Sometimes for example the hypophysis and surrounding circle of Willis arteries are entirely naked and sometimes they are covered by a very thin milky white membrane.
The four children were able to be discharged from the hospital 2 days after the intervention. They showed a marked improvement of their clinical status; the head bobbing, tremor and dysmetria had disappeared completely. In one girl the mental retardation and the hormonal disturbances remained unchanged.
Fig. 5. a) Laser coagulation of blood vessels on the cyst wall, b) cutting out with the laser of a rounded window in the membrane
72
J. Caemaert et al.: Endoscopic Treatment of Suprasellar Arachnoid Cysts
Fig. 6. Reductionof cyst volumeand hydrocephalusin two cases. (a, b) Pre-operatively,(c, d) five months after the operation Check CT-scans five months after the operation showed marked reduction in size of the cyst (Fig. 6) and the re-expansion of the thalamic region. We also noticed a reduction of the hydrocephalus without slit ventricle syndrome or subdural collections as may be seen after ventriculo-atrial or peritoneal shunting with overdrainage. In case four a second endoscopic intervention was necessary on the contralateral side, after 5 months, because on a check CT-scan we noted a re-expansion of the cyst volume after an initial marked reduction; the child was still in a good clinical condition. After this second intervention the cyst remained reduced. To date none of these children have needed an extracranial shunting procedure. The follow-up periods were respectively 36, 20, 20 and 7 months (2 months for the second operation in case 4). A longer period is necessary to prove the long term success of the method. In the future, dynamic M R I studies will be done to prove the restoration of normal flow of the CSF through the ventricle, the cyst and the basal cisterns. There was no operative mortality. The morbidity was limited to one epileptic attack in one child, six hours after the intervention; there was full recovery. Prophylactic antibiotics have always been given for 24 hours (amoxicilline trihydrate and potassium-clavulanate). Discussion
Pathogenesis Different hypotheses have been proposed concerning the genesis of arachnoid cysts4' 10, 11, 13, 24. One of them is the existence of a slit valve mechanism, a!though
nobody has ever seen such a valve. In a parasellar cyst we detected such a slit-valve in a membrane through which the oculomotor nerve and branches of the middle cerebral artery were discernable. This cleft opens at each inspiration and closes at expiration. By means of the balloon catheter and the grasping forceps we have destroyed this slit valve so that the cerebrospinal fluid could flow freely from the basal cisterns around the circle of Willis and vice versa. We now prefer a combination of this method with the use of a cutting laser, so that excessive traction on these membranes can be avoided. Following the clivus of Blumenbach in another case a slit-valve like structure was detected in a membrane surrounding the basilar artery. This opens and closes rapidly with arterial pulsations and might be related to the mechanism of the cyst enlargement 24. This structure was also opened widely.
Operative Technique Endoscopic laser fenestration of the wall of large suprasellar arachnoid or ependymal cysts has been an efficient treatment in four children. Treatment with ordinary ventriculo-atrial or peritoneal shunting is nearly always inefficient, even when a ventricular drain is inserted bilaterally. The cyst itself remains distended and continuing damage to the thalamic, hypothalamohypophyseal and optic structures occurs. Some surgeons proposed stereotactic insertion of a ventricular catheter into the cyst, connected as a supplement to the ventricular drainage. This logical solution however is fraught with difficulties and failures. The wall of these cysts is often quite tough and the catheters tend to deviate tangentially without penetration.
J. Caemaert etal.: Endoscopic Treatment of Suprasellar Arachnoid Cysts W e therefore prefer to open the cyst widely b y a n endoscopic fenestration in the wall into the lateral ventricle. This c o m m u n i c a t i o n should be as large as possible (10-15 m m ) to p r e v e n t secondary closing. A n o t h e r very i m p o r t a n t m e a s u r e to p r e v e n t recurrence of the d i l a t a t i o n is to m a k e at least two openings in the wall, one into the lateral ventricle, the other one into the basal p r e p o n t i n e cisterns. T h u s we establish a c o n s t a n t C S F flow t h r o u g h the cyst. The walls become floppy a n d instead of the oval or r o u n d distention, a tent-like structure r e m a i n s a n d the c o m p r e s s i o n o n the surr o u n d i n g structures disappears. Since the cause o f the h y d r o c e p h a l u s is treated, n o further d r a i n a g e is needed in those cases where the resorptive capacities have rem a i n e d intact. W h e n these capacities are d i s t u r b e d a s h u n t i n g procedure will be necessary b u t prior to shunting a fenestration of the cyst should be carried out. The technique was c o n s t a n t l y developing till at last the c o a g u l a t i n g a n d cutting laser p r o v e d to be the safest a n d easiest tool.
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