Научно-практический журнал «Нейрохирургия и неврология детского возраста» (Pediatric Neurosurgery and Neurology), 2011, 2(28), 30-52

The Use of Endoscopic Technique in Surgical Interventions for Isolated Fourth Ventricle

Petraki VL, Simernitsky B.P., Asadov R.N.

Medical Center for Children with Craniofacial Malformations and Congenital Nervous Diseases,

Moscow, Russia

Abstract

Thirty six children aged from 20 days to 7 years were operated on the isolated Fourth ventricle

using endoscopic techniques during 2001 - 2010 period. The majority of them (66%) were infants.

Two types of surgery were performed. The first type dealt with cases of complete obliteration of

aqueductus cerebri. The paraaqueductal outflow of CSF was formed by fistulae between cisterna

ambiens and the Third or lateral ventricle, and between cisterna ambiens and the Fourth ventricle.

When oral parts of the Fourth ventricle protrude into tentorial incisure, and roof of the Fourth

ventricle become a thin “membrane” adherent to a similar thin wall of a lateral or the Third

ventricle, a fistula was made between a lateral and the Fourth ventricle and between the Third and

the Fourth ventricles. The operation was supplemented by perforation of the floor of the Third

ventricle and foramen Magendie plasty to improve CSF outflow to subarachnoidal space. The

second type of surgery was aimed at restoration of physiological CSF-circulation with plasty and

stenting of aqueductus, foramen Magendie and craniovertebral junction combined with endoscopic

Third-ventriculocisternostomy (ETV).

CSF outflow from the Fourth ventricle was restored after surgery in 35 children (94% cases).

Stable compensation of hydrocephalus without any other manipulations was achieved in 5 cases. In

31 cases it required additional shunting.

CONCLUSIONS: In children (and especially in infants) endoscopic restoration of CSF

circulation is a method of choice in treatment of the isolated Fourth ventricle. It is achieved by

elimination of occlusion between cerebral ventricles (aqueductoplasty, interventriculostomy) and

simultaneous restoration of CSF flow into subarachnoid space (plasty of foramina Magendie and

Luschka, craniovertebral junction, Third-ventriculocisternostomy, and Third-Fourth

ventriculocisternostomy). Use of endoscopic technique in implantation of panventriculoperitoneal

shunt allows to perform surgery without stereotactic and navigation devices. Forced dilatation of

slit lateral and the Third ventricles after shunting gives opportunity for aqueductoplasty and

aqueductal stenting in the isolated Fourth ventricle.

Key words: isolated Fourth ventricle, endoscopic aqueductoplasty, aqueductal stent,

interventriculostomy, panventriculoperitonal shunt, Third-Fourth-ventriculocisternostomy, foramen

Luschka plasty, foramen Magendie plasty, cisternoventriculoperitoneal shunt,

ventriculosubarachnoidal stent.

The isolated (or entrapped) Fourth ventricle (IFV) is a form of multilevel obstructive

hydrocephalus. It has the most severe clinical course and difficult to treat. The isolated Fourth

ventricle is characterized by combination of closure of foramina Luschka and Magendie and

acqueductal occlusion. These occlusions result from acute or chronic inflammation of arachnoidea

and ependima accompanied by adhesion and periventricular edema in physiological diminutions of

CSF pathways [ 2 ]. They also may be caused by mechanical factors such as intraventricular

hemorrhage (IVH), functional acqueductal occlusion, repeated revisions of CSF shunts and cerebral

malformations. Occlusion hydrocephalus is complicated by IFV syndrome in 5-43% cases [ 2, 5, 9,

20, 29, 34 ].

There are many different surgical techniques for treatment of TFV. Most frequently performed

are suboccipital craniotomy with dissection of cerebellar vermis or adhesions blocking foramen

Magendie, endoscopic aqueductoplasty or aqueductal stenting [ 1, 4, 9, 10, 11, 13, 16, 17, 21, 26,

31, 32, 33, 35 ], intreventriculostomia [ 7, 10, 27, 32 ], isolated or combined shunting of lateral

ventricles and the Fourth ventricle [ 12, 14, 18, 19, 30 ] and combination of the above mentioned

interventions [ 4, 16, 18 ]. The risk of postoperative complications substantially increases in

newborns and infants.

The aim of our paper is to demonstrate possibility of radical intervention in different types

of IFV in newborns and infants using neuroendoscopy.

Material and methods

Thirty six children (age from 20 days to 7 years) with IFV were operated on with

neuroendoscopic technique during 10-year period (from 2001 to 2010). Twenty seven children

(75%) were preterm babies born at 27-37 week of gestation. In 11 cases endoscopic interventions

were primary and in 14 cases they were performed after earlier implanted VP-shunts. In 11 cases

endoscopy procedures and shunting were done simultaneously. In 12 children IFV was formed after

intraventricular hemorrhages. In 14 cases TFV was caused by infection of CSF spaces after IVH (5

cases) or neonatal sepsis (9 cases). Table 1 presents distribution of cases by age and etiology.

Twenty four operated on children were infants (66 %).

Table 1

Etiology

Age

Total<1 mo. 1-3 mo. 3 - 6 mo. 6-12 mo. >1

yr.

IVH III-IV grade 3 4 4 1 - 12

Meningitis and ventriculitis 3 1 3 2 5 14

Functional aqueductal

occlusion

- 1 1 7 9

Dandy-Walker syndrome - - 1 - - 1

Total 6 6 8 4 12 36

Variants of endoscopic interventions

Neuroendoscopic interventions were performed only by supratentorial approach using rigid

endoscopes “Richard Wolf” (external diameter 3,5 mm) and “Karl Storz” (external diameter 3 mm).

We considered two types of surgical intervention related to structural changes in CSF pathways:

either creation of paraaqueductal anastomosis (type I) or restoration of aqueductal patency (type II)

- aqueductoplasty (see Table 2).

Table 2

Distribution of children according to age and types of surgical interventions

Types of surgery

Age

Total<1 mo. 1-3 mo. 3 - 6 mo. 6 - 12 mo. > 1 yr.

Paraaqueductal

anastomosis (Type I)

- 2 4 1 1 8

Aqueductoplasty (Type II) 6 4 4 3 11 28

Total 6 6 8 4 12 36

Surgery of paraaqueductal anastomosis (type I). This type of surgery was aimed at

circumvention of totally long length occluded aqueduct by creation of direct CSF passage from the

Third or a lateral ventricle into the Fourth ventricle. When oral parts of the Fourth ventricle

protrude into tentorial incisure, and roof of the Fourth ventricle becomes a thin “membrane”

adherent to a similar thin wall of a lateral or the Third ventricle, it is possible to dissect or puncture

these “membranes” via empty cisterna ambiens and form a fistula between ventricles. In 3 children

a fistula was made between a lateral and the Fourth ventricle (Latero-Fourth-interventriculostomy –

see Fig.1) and in 2 cases it was performed between the Third and the Fourth ventricles (Third-

Fourth-interventriculostomy – see Fig.2). At the same time we restored CSF drainage into

interpeduncular cistern (Third-ventricolocisternostomy) and cisterna magna (foramen Magendie

plasty).

A B C

Fig.1. Endoscopic Lateral-Fourth-interventriculostomy.

A. A sketch of surgery.

B. Endoscopic view of supratentorial protrusion of upper wall of the Fourth ventricle as seen

from a lateral ventricle cavity.

C. Endoscopic view of an artificial fistula between a lateral and the Fourth ventricle

(indicated by arrow).

A B

Fig.2. Endoscopic Third-Fourth interventriculostomy.

A. MRI before surgery. Planned trajectory of the endoscope is indicated by arrow;

B. MRI after formation of artificial fistula between the Third and the Fourth ventricles. The

Fourth ventricle is shrunken.

In 3 cases surgical technique had some peculiarities when there was cisterna ambiens’ cavity

between ventricles (i.e. between the Third and the Fourth ventricles or a lateral and the Fourth

ventricle).

Surgical technique of Endoscopic Third-Fourth-ventriculocisternostomy. The endoscope is

introduced into cavity of the Third ventricle via frontal horn of a lateral ventricle (1 case). Posterior

wall of the Third ventricle is perforated at the level of subpineal inversion (posterior Third-

ventriculocisternostomy) and the endoscope reaches cisterna ambiens. Arachnoid bands inside the

cistern are dissected. Dorsal surface of lamina quadrigemina is an anatomical landmark of cisterna

ambiens. Roof of the Fourth ventricle is seen distally. It is presented as a thin and dome-shaped

deformed upper velum cerebelli. Velum is pointwise coagulated and perforated along midline. Then

the newly formed fistula to the Fourth ventricle is enlarged to the size of the endoscope diameter

(proximal Fourth-ventriculocisternostomy). Fluctuation of stoma margins and turbulent CSF flow

indicates fistula functioning.

At the same time we perform foramen Magendie plasty. The endoscope is inserted into the

dilated Fourth ventricle along midline and a surgeon inspects the ventricle cavity. The endoscope is

aimed at projection of foramen Magendie. Its obstructing membrane is perforated, and diameter of

resulting stoma is enlarged up to 5-7 mm (distal Fourth-ventriculocisternostomy or foramen

Magendie plasty). Then the endoscope is introduced in cisterna magna which is being inspected.

Finally it is feasible to perform standard Third-ventriculostomy which gives additional

possibilities for outflow of ventricular CSF into subarachnoid space. Fig. 3 provides an outline of

main stages of surgical intervention, and Fig.4 presents MRI of its result.

Occlusion

Fig.3. Main stages of endoscopic Third-Fourth ventriculocisternostomy.

Arrow 1 indicates posterior Third-ventriculocisternostomy (via recessus subpinealis to

cisterna ambiens). Arrow 2 indicates proximal Fourth-ventriculocisternostomy (from cisterna

ambiens via upper velum cerebelli in the Fourth ventricle cavity).

A B

Fig.4. Endoscopic Third-Fourth-ventriculocisternostomy.

A. MRI before surgery. Main planned stages of surgery are indicated by arrows: posterior

Third-ventriculocisternostomy (dotted arrow), proximal Fourth-ventriculocisternostomy (white

arrow), and plasty of foramen Magendie (black arrow);

B. MRI after surgery: perforation of the floor of the Third ventricle (white arrow) and

restoration of foramen Magendie (black arrow).

Surgical technique of Endoscopic Lateral-Fourth-ventriculocisternostomy. The

endoscope is introduced into anterior horn of a lateral ventricle by frontal approach and oriented

towards midline (2 cases). Medial wall of posterior horn of a lateral ventricle is perforated in

projection of cisterna ambiens with subsequent revision of this cistern. After main anatomical

landmarks (lamina quadrigemina, roof of the Fourth ventricle) are determined we perforate upper

cerebellar velum and formed a fistula to the Fourth ventricle. The fistula is enlarged to the size of

the endoscope diameter.

At the same time we perform foramen Magendie plasty thus connecting Fourth ventricle to

cisterna magna and restored CSF drainage into interpeduncular cistern (Third-

ventricolocisternostomy).

It should be mentioned that in our experience vital functions remained stable during surgery.

Surgery for restoration of aqueductal patency (type II). It was aimed at consecutive

restoration of pathways of CSF circulation by eliminating occlusion of aqueductus, foramen

Magendie and cranio-vertebral junction. Endoscopic aqueductoplasty was performed in cases of

membrane occlusion or aqueductal stenosis. A membrane which occluded aqueductus was

perforated and a newly created stoma was dilated until aqueductus was fully patent. In case of

stenosis aqueductus was widened first by bougienage and pendular movements of the endoscope’s

working instrument (1 mm diameter electrode), and then in similar fashion by the endoscope’s

corpus. By the end of the procedure aqueductal lumen could usually be dilated up to 4 – 4,5 mm,

and the endoscope might be inserted into the Fourth ventricle with minimal diversion from midline

(Fig.5).

A B

C D

E F

Fig.5. Endoscopic aqueductoplasty.

A. MRI before surgery. Planned trajectory of the endoscope is indicated by arrow;

B-F – endoscopic images: B – membrane aqueductal occlusion; C – the endoscope’s

working instrument (an electrode) in projection of membrane is indicated by arrow; D –view after

membrane perforation; E –dilatation of entrance hole and aqueductus; F – restored aqueductus after

its bouginage.

In 25 children aqueductoplasty was combined with endoscopic Third-ventriculocisternostomy

(ETV) to provide CSF leakage into subarachnoid space (Fig.6). It should be noted that in ETV in

case of the entrapped Fourth ventricle basal cisterns might be difficult to explore due to their

compression by displaced brainstem. That is why exploration of basal cisterns was performed in

final stage of surgery after the Fourth ventricle had been drained and cisterns decompressed.

A B

Fig.6. Combination of aqueductoplasty and Third-ventriculocisternostomy.

A. MRI before surgery. Planned trajectories of the endoscope are indicated by arrows:

aqueductoplasty is shown by black arrow, and Third-ventriculocisternostomy – by white arrow;

B. MRI after surgery. Perforation of the Third ventricle floor is indicated by white arrow and

restored aqueductus – by black arrow.

In 15 children we performed plasty of foramen Magendie in order to restore CSF leakage from

the Fourth ventricle into cisterna magna after aqueductoplasty (Fig.7).

A B

C D

E F

Fig.7. Endoscopic plasty of foramen Magendie.

A. Fourth ventricle and hemosiderosis near foramen Magendie (arrow);

B. Decollement of foramen Magendie (two arrows);

C. Revision of cisterna magna (arrow);

D. Brainstem vessels (arrow);

E. Revision of craniovertebral junction and decollement (arrow);

F. Free outlet from Fourth ventricle (arrow) at final stage of surgery.

In one case foramina Magendie and Luschka were obstructed after septic ventriculitis in

combination with numerous adhesions in aqueductal lumen and the Fourth ventricle. Restoration of

CSF outflow was achieved in this case by combination of aqueductoplasty and decollement (Fig.8).

A B

Fig.8. Combination of aqueductoplasty and decollement in the Fourth ventricle.

A. MRI before surgery. Multiple adhesions of aqueductus and the Fourth ventricle (arrow);

B. MRI after surgery. Aqueductus is patent (arrow) and volume of the Fourth ventricle is

reduced.

In another case it was impossible to open foramen Magendie which was obliterated by

adhesions to brainstem. But CSF outflow from the Fourth ventricle was restored after opening of

membrane adhesion which obstructed left foramen Luschka – foramen Luschka plasty (Fig.9).

A B

C D

Fig.9. Endoscopic plasty of foramen Luschka.

A and B: MRI before surgery;

C and D: MRI after surgery. Arrows indicate perforation of left foramen Luschka.

For prevention of aqueductal reocclusion an autonomous stent was inserted in 15 cases. It was a

silicon catheter with perforated walls in projection of the Fourth, the Third and a lateral ventricles.

Its length was prior calculated using MRI, CT or neurosonography. It amounted to a distance from

dura mater at the point of immersion to a lower third of the Fourth ventricle. The stent was

introduced into a lateral ventricle parallel to the endoscope which navigated the stent through the

Third ventricle and aqueductus into the Fourth ventricle. Proximal end of the catheter was fixed by

angular clips to burr hole margin or to dura mater in case of big open fontanelle (Fig.10, Fig.11).

A B

C D

Fig.10. Aqueductal stenting.

A. MRI before surgery: adhesive occlusion of aqueductus (arrow) and the entrapped Fourth

ventricle;

B. MRI after surgery. Longitudinal position of stent (arrow) inside the Fourth ventricle

along brainstem;

C. CT after surgery. Stent position (arrow) in ventricular system;

D. Relation of stent (arrows) to cranial structures (3D CT-reconstruction).

A B

C D

Fig.11 Aqueductal stenting. Endoscopic views.

A. Aqueductus as seen from the Third ventricle;

B. Stent (arrow) is navigated through aqueductus;

C. Stent position (arrow) inside the Fourth ventricle;

D. Stent position (arrow) in a lateral ventricle.

Aqueductal stent was used as ventricular catheter of a VP shunt in 7 cases when the Fourth

ventricle foramina were closed. After the catheter was navigated through aqueduct by the above

mentioned technique its distal end was connected with contour valve (Delta, “Medtronic”) and

peritoneal catheter. Thus combination of aqueductoplasty and aqueductal stenting with CSF

shunting enabled simultaneous draining of all cerebral ventricles by a singular shunting system –

panventriculoperitonal shunt (PVP-shunt) in the entrapped Fourth ventricle. Fig.12 presents the

results of such surgery.

A B

C D

Fig.12. Panventriculoperitoneal shunt (PVP- shunt).

A. MRI before surgery. The isolated Fourth ventricle (arrow);

B. MRI after surgery. Position of ventricular catheter (arrow) in ventricular system and

contraction of the Fourth ventricle;

C. CT after surgery. Midline position of ventricular catheter (arrow) in the Fourth

ventricle;

D. 3D CT reconstruction of PVP-shunt. Ventricular catheter is indicated by arrow.

PVP-shunting might be modified. In one case we inserted ventricular catheter into the Fourth

ventricle directly from a lateral ventricle after Lateral-Fourth-ventriculocisternostomy and in

another case – after Lateral-Fourth-interventriculostomy.

Similarly we inserted autonomous catheters between a lateral and the Fourth ventricle. Thus we

achieved sufficient internal decompression of the Fourth ventricle which enabled us to avoid

modification of previously implanted standard shunt systems or from implantation of an additional

VP-shunt from the Fourth ventricle (Fig.13).

A B

Fig.13. Endoscopic lateral Fourth-ventriculocisternostomy and implantation of

autonomous catheter (MRI after surgery).

A. Fistula between a lateral and the Fourth ventricle (arrow);

B. Catheter between a lateral and the Fourth ventricle (arrow).

It should be noted that both in paraaqueductal catheter implantations and in aqueductal stenting

catheters and stents are placed longitudinally to brain stem.

Within type II surgery there was ventriculosubarachnoid stenting in 9 patients - that is insertion

of one stent throughout foramen Monroe, aqueductus, foramen Magendie and craniovertebral

junction. Prevalence of adhesive process both in diminutions of ventricular system and in basal

subarachnoid space determines an increased risk of reocclusion after endoscopic intervention which

provokes adhesive process. Ventriculosubarachnoid stenting was aimed at preventing reocclusion at

different levels, and at preventing functional stenosis and obliteration of CSF pathways due to

contraction of ventricular system after shunting. In this procedure endoscopic aqueductoplasty,

plasty of foramen Magendie followed by revision of craniovertebral junction and dissection of

adhesions were the first stage of surgery. Then the stent was introduced into aqueductus and

navigated through Fourth ventricle. Its distal end was placed in cisterna magna (1 case) or

subarachnoid space of cervical part of spinal cord (8 cases) at C2-C7 levels (Fig.14 and Fig.15).

A B

C D

Fig.14. Ventriculosubarachnoidal stenting.

A. MRI before surgery. Status of ventricular system;

B. MRI after surgery. Shrinkage of cerebral ventricles;

C-D. CT (C) and 3D CT-reconstruction (D) after surgery. Distal end of the stent is

located at C3 level (arrows).

A B

C D

E F

G H

Fig.15. Ventriculosubarachnoidal stenting. Endoscopic views.

A. Decollement (arrow) of foramen Magendie;

B. Cavity of cisterna magna (arrow);

C. Margin of foramen magnum (arrow);

D. Adhesions (arrow) in craniovertebral junction;

E. Revision and decollement (arrow) in craniovertebral junction;

F. End of the catheter (arrow) at foramen magnum margin;

G. Navigation of the catheter to dorsal spinal space with working instrument (arrow) of

the endoscope;

H. Stent position (arrow) in craniovertebral junction at the end of surgery.

There were no significant reactions from structures at the floor of the Fourth ventricle during

ventriculosubarachnoidal stenting and after surgery. Postoperative MRI confirmed correct position

of stent in the Fourth ventricle and in spinal canal as well as absence of compression of brain stem

and cervical part of spinal cord (Fig.16).

A B

C D

Fig.16. Stent position in spinal canal after endoscopic ventriculosubarachnoidal stenting.

A. MRI after surgery. The stent is located along brainstem (white arrow);

B. Enlarged MRI after surgery which demonstrates craniovertebral junction and the

stent;

C. Relation of the stent (white arrow) to spinal cord (black arrow) in spinal canal on

MRI;

D. Position of distal end of the stent (yellow arrow) in spinal canal on craniospinal CT.

When calculating length of the catheter in spinal subarachnoid space we assumed that during

child’s growth a distal end of the catheter should stay in spinal canal outside the zone of adhesions.

We believe that the catheter should be plunged into spinal subarachnoid space as low as possible

but not lower than C6-C7 level (3 cases). In a newborn the length of cervical part of the stent from

foramen magnum to C7 level is 3, 5 cm.

In 2 children ventriculosubarachnoid stent was used as part of a shunting system. This enabled

to drain CSF into peritoneal cavity from ventricles and cerebral cisterns simultaneously – cisterno-

ventriculo-peritoneal shunt (CVP-shunt). Such shunt is shown at Fig.17.

A B

Fig.17. Cisternoventriculoperitoneal shunt on CT.

A. Position of ventricular catheter of a shunt (arrow) in craniocervical space;

B. Distal end of a ventricular catheter is located at C7 level (arrow).

Characteristics of endoscopic intervention at combination of the entrapped Fourth ventricle

and the slit Third and lateral ventricles.

In 4 children routine VP-shunting of tetraventricular occlusion hydrocephalus resulted into

contraction of lateral and the Third ventricles to a slit-like shape and functional aqueductal

occlusion with formation of IFV. The size of supratentorial portion of ventricular system prevented

the use of endoscopic technique for decompression of the Fourth ventricle. In 3 cases lateral and the

Third ventricles were dilated by transformation of peritoneal shunt catheter into external drainage

with gradual reduction of CSF outflow. Within 1-3 weeks lateral and the Third ventricles became

wide enough for endoscopic plasty and aqueductal stenting with simultaneous ETV as described

above (Fig.18).

I. A B

II. C D

III. E F

Fig.18. Ventricular system after VP-shunting on MRI.

A. Slit lateral ventricles (arrows);

B. The isolated Fourth ventricle (arrow);

C. Dilatation of lateral ventricles ( arrows) 16 days after transformation of a VP-shunt

and controlled intraventricular hypertension;

D. The Fourth ventricle maintain the same size (arrow);

E. Normal lateral ventricles (arrows) after aqueductal stenting with autonomous stent

and restoration of functioning of VP-shunt;

F. Autonomous stent of aqueductus (black arrow), the normal Fourth ventricle (white

arrow).

There was forced dilatation of ventricles during surgery in one case with lateral ventricles 15

mm wide and the Third ventricle – 5 mm wide. After the endoscope was inserted into a lateral

ventricle the latter was moderately dilated due to constant intraventricular infusion of normal saline

under increased pressure (400 mm H2O). This was sufficient for endoscopic procedures. Narrowed

foramen Monroe (functional stenosis after shunting) was dilated by bougienage movements of the

electrode and endoscope corpus. While infusion was continuing we passed the endoscope into the

Third ventricle and performed aqueductoplasty and aqueductal stenting combined with ITV

(Fig.19).

A B

C D

E F

Fig.19. Dilatation of ventricles by infusion technique on MRI.

A. Slit lateral ventricles (arrows) after VP-shunting;

B. Functional occlusion of foramina Monroe (arrow);

C. The isolated Fourth ventricle (arrow);

D. Intraoperative dilatation of lateral ventricles (arrows) by infusion technique;

E. Patent foramen Monroe (arrow) after its endoscopic plasty;

F. Autonomous stent of aqueductus (black arrow) and diminution of the Fourth

ventricle (white arrow).

Inspection of ventricular system at final stage of the surgery did not reveal macroscopic signs of

brain damage along trajectory of our intervention. This case demonstrates that intraventricular

infusion of normal saline under controlled pressure is an effective and sufficiently safe method of

ventricular dilatation during surgery. Its use allows excluding manipulations upon shunting system

and reducing preoperative period and total length of hospitalization.

In 3 cases aqueductal autonomous stent had to be removed after 1-2,5 months after surgery

(infection in CSF space -1, stent displacement-1, pleocitosis -1). Follow-up exam showed patent

and functioning aqueductus in all cases (Fig.20).

A

1 2 3

B

1 2 3

Fig.20. Restoration of aqueductal patency after its temporal stenting.

A. Postinflammatory occlusion of the Fourth ventricle’s foramina;

B. Posthemorrhagic occlusions of the Fourth ventricle’s foramina.

1. The isolated Fourth ventricle (arrows);

2. Aqueductal stenting (arrows);

3. Restoration of aqueductal patency after stent removal (arrows).

Results

CSF outflow from the Fourth ventricle was restored after surgery in 35 children (94% cases). It

was accompanied by reduction of neurological signs of compression of posterior fossa structures. In

one case there was slow progression of the Fourth ventricle enlargement due to reocclusion of

stoma between a lateral and the Fourth ventricle which required second surgery: suboccipital

craniotomy, foremen Magendie revision with removal of adhesions and implantation drainage

between the Fourth ventricle and cisterna magna. In 5 cases there was stable compensation of

hydrocephalus after endoscopic interventions due to restoration of physiological CSF resorption

which allowed avoiding implantation of a VP-shunt at final stage of treatment. Treatment results are

presented in Table 3.

Table 3

Results of surgical correction of the entrapped Fourth ventricle

Age Type of surgery OutcomeI II Hydrocephalus

compensation (without shunt)

Hydrocephalus stabilization(with VP-shunt)

0-1 months

- 6 1 5

1-3 months

2 4 4 2

3-6 months

4 4 - 8

6-12 months

1 3 - 4

1-6 years 1 11 - 12Total 8 28 5 31

Complications occurred in 5 cases (14, 4%): ventriculitis (1 case), stent displacement (1 case),

and transitory (2-7days) oculomotor impairments (3 cases). It should be noted that vital functions

were normal during surgery in most cases (33 patients). There was no perioperative mortality. Four

children died in remote postoperative period from causes unrelated to our intervention.

Discussion

Our study is dedicated to possibilities of radical treatment of the isolated Fourth ventricle which

is one of the most difficult types of multilevel occlusion hydrocephalus. Most cases (66%) were

newborns and infants.

Traditional methods of normalization of CSF circulation in case of the entrapped Fourth

ventricle are mostly aimed at elimination of just one level of occlusion or creation of alternative

outflow of CSF outside CSF space (e.g. VP-shunting). However routine VP-shunting of lateral

ventricles in case of the isolated Fourth ventricle is not effective unless the latter is previously

connected to supratentorial parts of ventricular system. Combined shunting of lateral and the Fourth

ventricles with two separate shunting systems or Y-shaped connection of two ventricular catheters

of one shunt is feasible. Although such interventions are less traumatic than direct suboccipital

craniotomy they are often (up to 50%) coupled with different complications which result to shunt

dysfunction and its repeated revisions [ 32 ], as well as with brainstem injury during implantation of

ventricular catheter in the Fourth ventricle [ 6, 8, 15, 30, 32 ]. Shrinkage of the Fourth ventricle

after surgery causes a risk of contact of ventricular catheter with brainstem because the former is

located inside the ventricle cavity at acute or even right angle towards brainstem.

Restoration of intracerebral CSF circulation by direct removal of occlusion is an alternative to

combined VP-shunting of a lateral and the Fourth ventricles. It includes the above mentioned

suboccipital craniotomy and interventriculostomy, endoscopic plasty and stenting of aqueductus

and foramen Magendie, as well as combination of these techniques.

Indications for endoscopic interventriculostomias between the Fourth and lateral or the Third

ventricles are limited. They are performed when aqueductoplasty is impossible and ventricles are

significantly enlarged after chronic hydrocephalus. Walls of ventricles are coming in close contact

and become thin which enables to perform fistula between the Fourth and the Third or lateral

ventricles by dissection or puncture of a separating “membrane” [ 10, 27, 32 ].

Aqueductoplasty as well as interventriculostomy are more effective than the Fourth ventricle

shunting and less traumatic than suboccipital craniotomy [ 10, 32 ]. However there are possibilities

of acqueductal reocclusion (20%) and development of oculomotor disorders [ 27, 32 ].

Occlusion hydrocephalus is prevalent in infants. CSF spaces are usually blocked at aqueductus,

the Fourth ventricle outlets, craniovertebral junction and basal cisterns due to adhesions [ 28 ].

Endoscopic interventions might irritate the existing adhesive process both in ventricular stenoses

and in basal subarachnoid space which increase a high risk of reocclusion. To prevent this

complication we combined endoscopic aqueductoplasty and stenting, and supplemented

interventriculostomias by implantation of the catheter between ventricles. It is important to note that

during postoperative reduction of the Fourth ventricle the stent remains located parallel to

brainstem. It eliminates the risk of irritation of brainstem structures. Fixation of stent or catheter

position in ventricular system and prevention of their migration is an important condition of

successful surgery. It is achieved by fixation of the stent or the catheter to cranial bone or dura

mater as well as to the shunt pump. In the last case the stent functions as a ventricular catheter of a

panventricular shunt and allows draining all cerebral ventricles evenly. Interestingly, in case of

panventricular shunting a ventricle shrinks similar to separate implantation of aqueductal stent and

standard VP-shunting. It should be noted that endoscopic stenting did not require stereotactic or

navigation equipment [ 34 ]. In all cases of stenting we managed to restore CSF outflow from the

Fourth ventricle.

The result was positive even in case of temporal stenting with subsequent stent removal. In 3

cases aqueductal stenting during 1 - 2,5 months was sufficient for a stable restoration of aqueductal

patency.

Aqueductal stenting was always combined with ITV in cases when we could not open

outlet foramina of the isolated Fourth ventricle. This enabled to divert CSF into subarachnoid

space and thus fully restore CSF circulation.

According to our experience and published literature aqueductoplasty is possible only in case of

membrane occlusion or “short” aqueductal stenosis [ 21, 25, 27 ]. In case of extensive aqueductal

obliteration the problem of isolated Fourth ventricle might be solved by interventriculostomy or

communication between the Fourth ventricle and the Third or lateral ventricles in circumvention of

aqueduct via cisterna ambiens. This could be done with or without implantation of catheters. In one

case we performed paraaqueductal Third-Fourth ventriculocisternostomia: in circumvention of

aqueduct we perforated posterior wall of the Third ventricle and connected it with cisterna ambiens,

then we perforated of upper velum cerebelli and penetrated into the Fourth ventricle. Combination

of two procedures provided communication between the Third and the Fourth ventricles and

cisterna ambiens. Occlusion of caudal parts of the Fourth ventricle was removed by resection of a

membrane in foramen Magendie and outing to cisterna magna.

Similarly in 2 cases we performed communication between the Fourth and lateral ventricles and

cisterna ambiens with simultaneous implantation of autonomous (1) or ventriclar (1) shunt catheter

in order to prevent obliteration of created stomae. Thus we provided internal decompression of the

Fourth ventricle without its extracranial shunting.

In direct surgery of the Fourth ventricle with suboccipital craniotomy the occlusion is removed

by dissection of adhesions which obliterate foramen Magendie or by dissection of vermis cerebelli

[ 7, 35 ]. Some authors recommend completing this intervention by implantation of the catheter

between the Fourth ventricle and spinal subarachnoid space [ 7 ]. This technique allows placing the

catheter along midline of the Fourth ventricle which reduces a risk of brainstem damage. The

surgery restores physiological CSF circulation. It does not require use of valve devices and presents

a justified alternative to a “classical” ventriculoperitoneal shunting of the Fourth ventricle. However

this surgery is traumatic which is a serious obstacle to its use in newborns (especially in premature

neonates) and infants. Our technique of endoscopic perforating ventriculosubaracnoidal stenting of

CSF system is much more conservative. In our opinion, there are two basic advantages of our

method of stenting of CSF system. First, it restores CSF circulation inside ventricular system and

simultaneously allows CSF outflow into subarachnoid space. Second, traumatic suboccipital

craniotomy is unnecessary which makes possible to use our method in newborns and infants.

The efficacy of the proposed method of perforating ventriculosubaracnoidal stenting is not yet

proven. However it should be noted that we achieved compensation of hydrocephalus without

additional VP-shunting in 2 children out of 6 who underwent ventriculosubarachnoidal stenting.

There was reduction of cavities of the Third and lateral ventricles to slit ventricles,

diminution of foramen Magendie, aqueductal occlusion and formation of the isolated Fourth

ventricle in 4 children after VP-shunting for tetraventricular obstructive hydrocephalus.

Similar changes in ventricular system after shunting procedures are reported by other authors

[ 2, 3, 22, 23, 24, 32 ].

In such cases we used a method of controlled forced enlargement of lateral and the Third

ventricles in order to eliminate occlusions. This enables us to use endoscopic technique for restoring

communication between all compartments of ventricular system and achieve normal functioning of

a VP-shunt. There were two options for ventricles’ enlargement. First, a peritoneal catheter of a

previously implanted and functioning VP-shunt was removed from peritoneal cavity and connected

to a system of external drainage [ 3, 32 ]. This created resistance to CSF within the system which

contributed to gradual collection of CSF inside ventricles and their enlargement. After occlusion

was eliminated the surgery ended by restoration of VP-shunt.

Second option was used when the width of lateral ventricles was sufficient for insertion of the

endoscope. There was single-step forced dilatation of ventricles by filling them with normal saline

under endoscopic control. This option allowed reducing time for preparation for surgery and

preserve previously implanted VP-shunt.

In general we can assert that our technique of endoscopic plasty and stenting of obstructed CSF

pathways at different levels (from foramen Monroe to craniovertebral junction) and catheterization

of the artificial Fourth ventricle fistulae provides long-lasting effect of our minimally-invasive

intervention.

There are several advantages of surgical tactics. First, there is one supratentorial approach via

fontanelle or a burr-hole. Second, it can be combined with other endoscopic procedures. Third,

endoscopic control allows performing surgery without navigation and stereotactic equipment.

Fourth, the stent (catheter) is placed at midline of the Fourth ventricle along brainstem and

maintains such location after reduction of the ventricle volume in remote postoperation period

which allows avoiding injury of brainstem structures by the catheter. Fifth, in case there is a need

for extracranial CSF drainage we can use the stent (catheter) as a ventricular catheter of VP-shunt or

as an external drainage thus providing CSF outflow both from ventricles and subarachnoid space.

Conclusions:

1. In children (and especially in infants) endoscopic intervention is a method of choice in treatment

of the isolated Fourth ventricle.

2. Restoration of physiological CSF circulation is a priority in the isolated Fourth ventricle. It is

achieved by elimination of occlusion between cerebral ventricles (aqueductoplasty,

interventriculostomy) and simultaneous restoration of CSF flow into subarachnoid space (plasty of

foramina Magendie and Luschka, craniovertebral junction, Third- ventriculocisternostomy, and

Third-Fourth ventriculocisternostomy).

3. The technique of forced aqueductal enlargement does not induce irreversible neurological deficit.

This technique is essential for success of our surgical approaches.

4. Endoscopic aqueductal stenting and catheterization of artificial fistulae of the Fourth ventricle

prevents reocclusions and provides optimal position of a stent or a catheter in relation to brainstem

in the Fourth ventricle cavity.

5. Craniovertebral junction and foramina Luschka are accessible targets in endoscopic surgery for

the entrapped Fourth ventricle in children of all ages.

6. The use of endoscopic technique in implantation of panventriculoperitoneal shunt which equally

drains all cerebral ventricles allows to perform surgery without stereotactic and navigation devices.

7. In case of impaired CSF resorption ventriculosubarachnoidal stenting which provides

communication between all CSF spaces is concluded by implantation of a system for extracranial

drainage. Unlike routine VP-shunting for occlusion hydrocephalus this allows to evacuate CSF both

from ventricular system and subarachnoid space.

8. Formation of paraaqueductal pathway from the Fourth ventricle to cisterna ambiens by

endoscopic approach via the Third or a lateral ventricle is one of options for draining of the Fourth

ventricle into subarachnoidal space in case of intractable aqueductal occlusion.

9. Forced dilatation of the slit lateral and Third ventricles after shunting for occlusion

hydrocephalus gives opportunity for aqueductoplasty and aqueductal stenting in the isolated Fourth

ventricle.

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Research and Practice Center for Children with Craniofacial Malforvations and Congenital Nervous System Diseases. 

(119620, Moscow, Aviatorov str., 38)

Email: boris.simernitski@gmail.com