Fourth ventricle outlet obstruction

Fourth ventricle outlet obstruction

The fourth ventricle outlet obstruction (FVOO) is a rare but well-established cause of obstructive tetra-ventricular hydrocephalus, characterizing with dilatation or large cerebrospinal fluid collection of the foramen of Magendie and foramen of Luschka.

Hydrocephalus is classified as noncommunicating and communicating based on whether all ventricular and subarachnoid spaces are communicating. Although the diagnosis between the two different states is crucial, it is difficult in certain conditions. In particular, communicating hydrocephalus and noncommunicating hydrocephalus owing to fourth ventricle outlet obstruction are highly misdiagnosed.

In FVOO, cerebrospinal fluid (CSF) is blocked at the fourth ventricle outlets by a membranous structure in the absence of any additional obstructive organic pathologies. Various terms for referring to FVOO have been used in previous reports, such as fourth ventricle/ventricular outlet obstruction 1) 2) 3) 4), fourth ventricular outflow obstruction 5), membranous obstruction of the fourth ventricle outlet 6) , obstruction of Magendie’s and Luschka’s foramina 7) , obstruction of fourth ventricular exit8) and primary obstruction of the fourth ventricle outlets 9). Far distal obstructive hydrocephalus is a term that includes Dandy Walker or Arnold Chiari malformation, membranous obstruction or fourth ventricle and intercisternal external obstruction of the CSF 10).


The etiology and pathogenesis of FVOO are unclear, although some cases present with a history of meningitis or intraventricular hemorrhage.

In children, it is usually the consequence of posterior cerebral fossa malformations; while in adult, the occlusion is rather acquired than congenital, mostly linked to an inflammatory process, intraventricular hemorrhagehead traumabrain tumors or Arnold-Chiari malformation. However, idiopathic FVOO is extremely rare, and only 6 such cases have been reported in the English literature.

Bai et al., described an extraordinarily rare case of idiopathic FVOO in a 15-year-old patient successfully treated with direct microsurgical excision of the obstruction membrane. Furthermore, the clinical characteristics and treatment for this rare disease were investigated and reviewed 11).


CT ventriculography in infants, and CT cisternography in elder children, may assist to differentiate between FVOO and communicating hydrocephalus. The importance of these tests is for children with MRI suggestive of FVOO related hydrocephalus, but with no clear demonstration of the obstruction site. The implication of this differentiation may be for deciding between treatment of hydrocephalus with a ventriculoperitoneal shunt or with an endoscopic third ventriculostomy 12).


Third ventricle-fourth ventriculostomy is by far the most frequently used technique for cannulation of the aqueduct in a trapped fourth ventricle. In reported cases of , they have introduced a silicone tube stent from below after accessing the fourth ventricle through a small suboccipital craniectomy, ascending it on the aqueduct in order to reach the third ventricle. Management of this infrequently isolated fourth ventricle, but communicated with the rest of ventricular system, remains a challenge for neurosurgeons. Lack of knowledge of the pathophysiology makes it difficult to treat a problem that we do not understand 13).

ETV is a viable option for treatment of patients with FVOO. The high failure rate in infants younger than 6 months of age suggests that ventriculoperitoneal shunting is a favorable option in this age group, rather than ETV. Isolated fourth ventricle is uncommon after ETV in hydrocephalus attributable to FVOO 14).

Suehiro et al., reported the use of neuroendoscopic third ventriculostomy to treat successfully both hydrocephalus and syringomyelia associated with fourth ventricle outlet obstruction. A 27-year-old woman presented with dizziness, headache, and nausea. Magnetic resonance (MR) imaging demonstrated dilation of all ventricles, downward displacement of the third ventricular floor, obliteration of the retrocerebellar cerebrospinal fluid (CSF) space, funnellike enlargement of the entrance of the central canal in the fourth ventricle, and syringomyelia involving mainly the cervical spinal cord. Cine-MR imaging indicated patency of the aqueduct and an absent CSF flow signal in the area of the cistema magna, which indicated obstruction of the outlets of the fourth ventricle. Although results of radioisotope cisternography indicated failure of CSF absorption, neuroendoscopic third ventriculostomy completely resolved all symptoms as well as the ventricular and spinal cord abnormalities evident on MR images. Neuroendoscopic third ventriculostomy is an important option for treating hydrocephalus in patients with fourth ventricle outlet obstruction15).

Case series

Three patients who were 21, 53, and 68 years of age presented with either headaches (isolated or associated with raised intracranial pressure) or vertigo, or a combination of gait disorders, sphincter disorders, and disorders of higher functions. In each case, magnetic resonance (MR) imaging demonstrated hydrocephalus involving the four ventricles (mean transverse diameter of third ventricle 14.15 mm; mean sagittal diameter of fourth ventricle 23.13 mm; and mean ventricular volume 123.92 ml) with no signs of a Chiari Type I malformation (normal posterior fossa dimensions, no herniation of cerebellar tonsils). The diagnosis of obstruction was confirmed using ventriculography (in two patients) and/or MR flow images (in two patients). All patients presented with marked dilation of the foramen of Luschka that herniated into the cisterna pontis. All patients were treated using ETV. No complications were observed. All three patients became asymptomatic during the weeks following the surgical procedure and remained stable at a mean follow-up interval of 36 months. Postoperative MR images demonstrated regression of the hydrocephalus (mean transverse diameter of third ventricle 7.01 mm; mean sagittal diameter of fourth ventricle 16.6 mm; and mean ventricular volume 79.95 ml), resolution of dilation of the foramen of Luschka, and good patency of the ventriculostomy (flow sequences). These results confirm the existence of hydrocephalus caused by idiopathic fourth ventricle outflow obstruction without an associated Chiari Type I malformation, and the efficacy of ETV for this rare indication 16).

Case reports

Duran D, Hadzipasic M, Kahle KT. Mystery Case: Acute hydrocephalus caused by radiographically occult fourth ventricular outlet obstruction. Neurology. 2017 Jan 31;88(5):e36-e37. doi: 10.1212/WNL.0000000000003555. PubMed PMID: 28138085 17).

A 66-year-old woman with gait disturbance and incontinence caused by hydrocephalus underwent ventriculoperitoneal shunt surgery. After 9 months, her fourth ventricle became enlarged and could not be controlled by lowering the shunt pressure. Magnetic resonance imaging (MRI) demonstrated obstruction at the foramen of Magendie, foramina of Luschka, and the cerebral aqueduct. Endoscopic surgery for aqueduct plasty with third ventriculostomy was planned. Because the aqueduct was observed to open spontaneously, only the standard third ventriculostomy was performed. When MRI findings were reviewed retrospectively, an unnatural space was observed between the lower cranial nerves and cerebellar hemisphere that grew along with the fourth ventricular enlargement. This space was determined by MRI cisternography to be the cystic membrane ballooning out from the foramen of Luschka. The primary hydrocephalus likely resulted from fourth ventricle outlet obstruction.

Enlargement of the whole ventricular system with an expanded space between the lower cranial nerves and cerebellar hemisphere can be caused by fourth ventricle outlet obstruction. In such cases, preoperative evaluation of anatomic architecture and cerebrospinal fluid obstruction using MRI cisternography is essential and leads to a successful endoscopic strategy 18).

A 3-year old boy without any remarkable medical history presented with a headache and vomiting. Computed tomography (CT) images, which had incidentally been taken 2 years previously due to a minor head injury, showed no abnormality. Magnetic resonance imaging on admission showed tetra-ventricular hydrocephalus associated with the dilatation of the fourth ventricle outlets, without any obstructive lesions. However, CT ventriculography, involving contrast medium injection through a ventricular catheter, suggested mechanical obstruction of the cerebrospinal fluid (CSF) at the fourth ventricle outlets. Thus, the patient was diagnosed with FVOO and ETV was performed; the hydrocephalus was subsequently resolved. Although hydrocephalus recurred 1 year postoperatively, re-ETV for the highly stenosed fenestration successfully resolved this condition.

ETV should be considered for FVOO treatment, particularly in idiopathic cases without CSF malabsorption 19).

A 15-year-old girl with amenorrhea and a several-week history of headache. After the diagnosis of membranous obstruction of the foramen of Magendie suggested by MRI, suboccipital craniotomy for removal of the membrane was carried out. The patient made an excellent postoperative recovery, and postoperative phase-contrast MRI demonstrated patent cerebrospinal fluid (CSF) pathways at the level of the foramina of Magendie and Luschka. We believe that this case is of interest because of the unequivocal evidence on MRI studies of the occlusion of the foramen of Magendie preoperatively, and because of the dramatic postoperative MRI findings demonstrating the effectiveness of the surgical procedure both in terms of ventricular size and CSF flow characterization 20).


1) , 13)

Ferrer E, de Notaris M. Third ventriculostomy and fourth ventricle outlets obstruction. World Neurosurg. 2013 Feb;79(2 Suppl):S20.e9-13. doi: 10.1016/j.wneu.2012.02.017. Epub 2012 Feb 10. Review. PubMed PMID: 22381846.
2) , 14)

Mohanty A, Biswas A, Satish S, Vollmer DG. Efficacy of endoscopic third ventriculostomy in fourth ventricular outlet obstruction. Neurosurgery. 2008 Nov;63(5):905-13; discussion 913-4. doi: 10.1227/01.NEU.0000333262.38548.E1. PubMed PMID: 19005381.
3) , 12)

Roth J, Ben-Sira L, Udayakumaran S, Constantini S. Contrast ventriculo-cisternography: an auxiliary test for suspected fourth ventricular outlet obstruction. Childs Nerv Syst. 2012 Mar;28(3):453-9. doi: 10.1007/s00381-011-1639-y. Epub 2011 Nov 29. PubMed PMID: 22124573.
4) , 15)

Suehiro T, Inamura T, Natori Y, Sasaki M, Fukui M. Successful neuroendoscopic third ventriculostomy for hydrocephalus and syringomyelia associated with fourth ventricle outlet obstruction. Case report. J Neurosurg. 2000 Aug;93(2):326-9. PubMed PMID: 10930021.
5) , 16)

Karachi C, Le Guérinel C, Brugières P, Melon E, Decq P. Hydrocephalus due to idiopathic stenosis of the foramina of Magendie and Luschka. Report of three cases. J Neurosurg. 2003 Apr;98(4):897-902. PubMed PMID: 12691419.
6) , 20)

Huang YC, Chang CN, Chuang HL, Scott RM. Membranous obstruction of the fourth ventricle outlet. A case report. Pediatr Neurosurg. 2001 Jul;35(1):43-7. Review. PubMed PMID: 11490191.

Carpentier A, Brunelle F, Philippon J, Clemenceau S. Obstruction of Magendie’s and Luschka’s foramina. Cine-MRI, aetiology and pathogenesis. Acta Neurochir (Wien). 2001;143(5):517-21; discussion 521-2. PubMed PMID: 11482704.

Choi JU, Kim DS, Kim SH. Endoscopic surgery for obstructive hydrocephalus. Yonsei Med J. 1999 Dec;40(6):600-7. PubMed PMID: 10661039.

Longatti P, Fiorindi A, Martinuzzi A, Feletti A. Primary obstruction of the fourth ventricle outlets: neuroendoscopic approach and anatomic description. Neurosurgery. 2009 Dec;65(6):1078-85; discussion 1085-6. doi: 10.1227/01.NEU.0000360133.29217.44. PubMed PMID: 19934967.

Oertel JM, Mondorf Y, Schroeder HW, Gaab MR. Endoscopic diagnosis and treatment of far distal obstructive hydrocephalus. Acta Neurochir (Wien). 2010 Feb;152(2):229-40. doi: 10.1007/s00701-009-0494-z. Epub 2009 Aug 26. PubMed PMID: 19707715.

Bai J, Yu Q, Sun X, Xiao H, Wang K, Sun F, Sui Q. Hydrocephalus Due to Idiopathic Fourth Ventricle Outflow Obstruction. J Craniofac Surg. 2019 Mar 6. doi: 10.1097/SCS.0000000000005314. [Epub ahead of print] PubMed PMID: 30865115.

Duran D, Hadzipasic M, Kahle KT. Mystery Case: Acute hydrocephalus caused by radiographically occult fourth ventricular outlet obstruction. Neurology. 2017 Jan 31;88(5):e36-e37. doi: 10.1212/WNL.0000000000003555. PubMed PMID: 28138085.

Shimoda Y, Murakami K, Narita N, Tominaga T. Fourth Ventricle Outlet Obstruction with Expanding Space on the Surface of Cerebellum. World Neurosurg. 2017 Apr;100:711.e1-711.e5. doi: 10.1016/j.wneu.2017.01.088. Epub 2017 Jan 31. PubMed PMID: 28153613.

Ishi Y, Asaoka K, Kobayashi H, Motegi H, Sugiyama T, Yokoyama Y, Echizenya S, Itamoto K. Idiopathic fourth ventricle outlet obstruction successfully treated by endoscopic third ventriculostomy: a case report. Springerplus. 2015 Sep 30;4:565. doi: 10.1186/s40064-015-1368-x. eCollection 2015. PubMed PMID: 26543700; PubMed Central PMCID: PMC4627988.

Atlas of Endoscopic Neurosurgery of the Third Ventricle: Basic Principles for Ventricular Approaches and Essential Intraoperative Anatomy

Atlas of Endoscopic Neurosurgery of the Third Ventricle: Basic Principles for Ventricular Approaches and Essential Intraoperative Anatomy

Atlas of Endoscopic Neurosurgery of the Third Ventricle: Basic Principles for Ventricular Approaches and Essential Intraoperative Anatomy

By Roberto Alexandre Dezena

List Price: $199.00
This book describes in practical terms the endoscopic neurosurgery of the third ventricle and surrounding structures, emphasizing aspects of intraoperative endoscopic anatomy and ventricular approaches for main diseases, complemented by CT / MRI images. It is divided in two parts: Part I describes the evolution of the description of the ventricular system and traditional ventricular anatomy, besides the endoscopic neurosurgery evolution and current concepts, with images and schematic drawings, while Part II presents a collection of intraoperative images of endoscopic procedures, focusing in anatomy and main pathologies, complemented by schemes of the surgical approaches and CT / MRI images.
The Atlas of Endoscopic Neurosurgery of the Third Ventricle offers a revealing guide to the subject, addressing the needs of medical students, neuroscientists, neurologists and especially neurosurgeons.

Product Details

  • Original language: English
  • Number of items: 1
  • Dimensions: 11.41″ h x .88″ w x 8.51″ l,
  • Binding: Hardcover
  • 271 pages

About the Author

Roberto Alexandre Dezena: MD from the Federal University of Triângulo Mineiro, Uberaba, Brazil (2003), completed his residency training in Neurosurgery at Santa Casa de Misericórdia de Ribeirão Preto, Brazil (2009), achieved his PhD in Neurosurgery at Ribeirão Preto Medical School of University of São Paulo, Brazil (2011), and his Postdoctoral Fellowship at Federal University of Triângulo Mineiro, Uberaba, Brazil (2014). In Brazil, is Full Member of Brazilian Society of Neurosurgery (SBN) and Brazilian Academy of Neurosurgery (ABNc). Internationally, is Fellow of World Federation of Neurosurgical Societes (WFNS), Active Member of both International Society for Pediatric Neurosurgery (ISPN) and International Federation of Neuroendoscopy (IFNE), and Full Member of both Latin American Federation of Neurosurgery Societes (FLANC) and Latin American Group of Studies in Neuroendoscopy (GLEN). Fellow of University of Tübingen, Germany, and University of Hiroshima, Japan. Currently is Chief of Division of Neurosurgery at Clinics Hospital, Neurosurgery Residency Director, and Professor of Postgraduate Program in Health Sciences and Postgraduate Program in Applied Biosciences, all in Federal University of Triângulo Mineiro, Uberaba, Brazil. Main neurosurgical areas in vascular and neuro-oncology microneurosurgery, endoscopic neurosurgery, pediatric neurosurgery, spinal surgery and neurotrauma. Main research areas in endoscopic neurosurgery, pediatric neurosurgery, neurotrauma, experimental cerebral ischemia and basic neurosciences. Editorial Board Member of International Journal of Anesthesiology Research (Phaps), Journal of Neurology and Stroke (Medcrave), EC Neurology (EC), and International Journal of Pediatrics and Children Health (Savvy). Reviewer of several online international scientific journals, highlighting World Neurosurgery (WFNS), Neurological Research (Maney) and Journal of Neurosurgical Sciences (Minerva).

Update: Fourth ventricle hydrocephalus

Synonyms: Entrapped fourth ventricle; Isolated fourth ventricle.
Udayakumaran and Panikar reiterate that a Fourth ventricle hydrocephalus or trapped fourth ventricle (TFV) is a functional concept with imaging being at most only corroboratory 1).
In adults, Ferrer and de Notaris call this condition the functional trapped fourth ventricle because in none of there cases they have found physical obstruction of CSF flow 2).


Fourth ventricle hydrocephalus, or a “trapped” fourth ventricle is a rare and uncommon entity which has been observed as a complication after intraventricular hemorrhage, infection/ meningitis or as a result of chronic shunt overdrainage after hydrocephalic shunting 3) 4) 5) 6).
A postinfectious occlusion of fourth ventricle outflow (foramen of Luschka and Magendie) and aqueduct of sylvius is the second most common cause for the development of trapped fourth ventricle 7).
This condition is caused by blockage of both the outlets (Foramen of Luschka, Foramen of Magendie) and the inlet of the fourth ventricle at the level of the aqueduct of Sylvius 8).
Progressive dilation of the fourth ventricle is due to continuing CSF production by the choroid plexus of the fourth ventricle within a closed space.
An increased cerebrospinal fluid (CSF) pressure within the fourth ventricle can lead secondary to the enlargement of the central canal in terms of communicating secondary syringomyelia. The exact pathophysiological mechanism of developing syringomyelia generally is not well established and remains yet controversial although several theories have been postulated 9).

In a follow-up study of 164 hydrocephalic children without tumors treated with ventriculoperitoneal shunts, 46 (28.0%) developed slit ventricle syndrome, 5 (3.0%) developed isolated fourth ventricles, and 4 (2.4%) developed isolated unilateral hydrocephalus. All of the patients with isolated unilateral hydrocephalus and 3 with isolated fourth ventricles had associated slit ventricles, 2 of whom had enlarged ventricles as double-compartment hydrocephalus. Reopening of the foramen of Monro or the aqueduct was achieved in one of the former and two of the latter cases with re-expansion of the slit ventricles. It is suggested that in some cases, the slit ventricle could be a causative factor in post-shunt isolated ventricle 10).

Clinical features

Such an entrapment may lead to clinical symptoms secondary to distortion of the brainstem and lower CNs. The clinical findings are mostly non localizing, even when there are obvious bulbar signs.


Imaging may corroborate clinical findings but may not be diagnostic by itself.

The diagnostic and treatment dilemma is to differentiate between a “true” symptomatic TFV and other conditions associated with a large fourth ventricle. This dilemma is especially significant when one is attempting to identify those patients who may benefit from surgery, as opposed to those patients with a well-compensated process that simply have a similar clinical and a radiological picture of a large fourth ventricle.

Differential diagnosis

Posterior fossa cysts are usually divided into Dandy Walker malformations, posterior fossa arachnoid cysts, and isolated and/or trapped fourth ventricles.


Treatment of the TFV remains a formidable challenge. However, prompt recognition and intervention may aid in the preservation of life and neurological function 11).
Treatment extends from placement of fourth ventriculoperitoneal shunt, endoscopic aqueductoplasty and interventriculostomy to open fenestration via suboccipital craniotomy 12) 13).
Prone position is better compared to the sitting position. Apart from the risk of air embolism and post operative pneumocephalus in the sitting position, the air may get trapped in the ventricle and interfere in intraoperative visualization 14).
Unfortunately, these techniques showed a high rate of dysfunction and complications.
Standard management of loculated fourth ventricle hydrocephalus consists of fourth ventricle shunt placement via a suboccipital approach. An alternative approach is stereotactic-guided transtentorial fourth ventricle shunt placement via the nondominant superior parietal lobule.


The development of neuroendoscopy has dramatically changed the outcome of these patients and the literature review suggest that endoscopic trans-fourth ventricle aqueductoplasty and stent placement is a minimally invasive, safe, and effective technique for the treatment of TFV and should be strongly recommended, especially in patients with supratentorial slit ventricles 15).
Aqueduct stent placement is technically feasible and can be useful in selected patients either with endoscopy or open surgery 16).
Essentially, the main cause of a TFV, namely, the aqueductal obstruction, is addressed using an endoscopic technique, and hence it is the most rational of all surgeries for this condition. The aqueduct can be dilated and kept open using a stent either through a transfrontal (trans-third ventricle) route or through a trans-fourth ventricular route. The latter is a shorter route, but is less commonly used probably due to the lack of familiarity with the endoscopic anatomy of the region of the fourth ventricle.
With either route, the surgeon has to decide whether a simple dilatation of the aqueduct will suffice or to leave a stent in place. The advantage of a stent is that the patency of the aqueduct is ensured in the postoperative period unless the stent migrates. The major disadvantage is that of infection due to the presence of a foreign body. Gallo et al., placed a stent whenever the dilated aqueduct was narrower than the width of the stent. Although theoretically it is possible to produce additional neurological deficits by introducing a wider stent through a narrower aqueduct, in the authors’ series, the complications (two patients with ophthalmoparesis) were equally distributed between those who had a stent placed and those who underwent aqueductoplasty alone. Hence, it appears that fear of additional deficits should not deter a surgeon from using a stent 17).

Longatti et al., suggest a very simple method of steering the tip of standard ventricular catheters by using materials commonly available in all operating rooms. The main advantage of this method is that it permits less invasive transaqueductal drainage of trapped fourth ventricles, especially in cases of narrow third ventricle, because the scope and catheter are introduced in sequence and not in a double-barreled fashion. Two illustrative cases are reported 18).

Stereotactic parietal transtentorial approach

Stereotactic parietal transtentorial shunt placement may be considered for patients with loculated fourth ventricle hydrocephalus, especially when shunt placement via the standard suboccipital approach fails. It is therefore reasonable to offer this procedure either as a first option for the treatment of fourth ventricle hydrocephalus or when the need for fourth ventricle shunt revision arises 19).

In 10 patients, Turner et al., used an alternative technique involving stereotactic and endoscopic methods to place a catheter in symptomatic posterior fossa cysts across the tentorium. Discussion of these cases is included, along with a review of various approaches to shunt placement in this region and recommendations regarding the proposed technique.
No patient suffered intracranial hemorrhage related to the procedure and catheter implantation. All 3 patients who underwent placement of a new transtentorial cystoperitoneal shunt and a new ventriculoperitoneal shunt did not suffer any postoperative complication; a decrease in the size of their posterior fossa cysts was evident on CT scans obtained during the 1st postoperative day. Follow-up CT scans demonstrated either stable findings or further interval decrease in the size of their cysts. In 1 patient, the postoperative head CT demonstrated that the transtentorial catheter terminated posterior to the right parietal occipital region without entering the retrocerebellar cyst. This patient underwent a repeat operation for proximal shunt revision, resulting in an acceptable catheter implantation. The patient in Case 8 suffered from a shunt infection and subsequently underwent hardware removal and aqueductoplasty with stent placement. The patient in Case 9 demonstrated a slight increase in fourth ventricle size and was returned to the operating room. Exploration revealed a kink in the tubing connecting the distal limb of the Y connector to the valve. The Y connector was replaced with a T connector, and 1 week later, CT scans exhibited interval decompression of the ventricles. This patient later presented with cranial wound breakdown and an exposed shunt. His shunt hardware was removed and he was treated with antibiotics. He later underwent reimplantation of a lateral ventricular and transtentorial shunt and suffered no other complications during a 3-year follow-up period 20).


Frassanito et al., report an exceptional case of Descending transtentorial herniation (DTH) complicating the implant of a CSF shunting device in the trapped fourth ventricle of a 17-year-old boy in whom a second CSF shunting device had been implanted for neonatal posthemorrhagic and postinfectious hydrocephalus. The insidious clinical and radiological presentation of DTH, mimicking a malfunction of the supratentorial shunt, is documented. Ultimately, the treatment consisted of removal of the infratentorial shunt and endoscopic acqueductoplasty with stenting. The absence of supratentorial mass lesion and other described etiologies of DTH prompted the authors to speculate on the hydrodynamic pathogenesis of DTH in the present case 21).

Cranial nerve palsy is rarely seen after shunt placement in an isolated fourth ventricle. In the few reports of this complication, neuropathies are thought to be caused by catheter injury to the brainstem nuclei either during the initial cannulations or after shrinkage of the fourth ventricle. The authors treated a child who suffered from delayed, progressive palsies of the sixth, seventh, 10th, and 12th cranial nerves several weeks after undergoing ventriculoperitoneal shunt placement in the fourth ventricle. Magnetic resonance imaging revealed the catheter tip to be placed well away from the ventricular floor but the brainstem had severely shifted backward, suggesting that the pathogenesis of the neuropathies was traction on the affected cranial nerves. The authors postulated that the siphoning effect of the shunt caused rapid collapse of the fourth ventricle and while the cerebellar hemispheres were tented back by adhesions to the dura, the brainstem became the only mobile component in response to the suction forces. Neurological recovery occurred after surgical opening of the closed fourth ventricle and lysis of the basal cistern adhesions, which restored moderate ventricular volume and released the brainstem to its normal position 22).

Case series


Pomeraniec et al retrospectively reviewed 8 consecutive cases involving pediatric patients with TFV following VP shunting for IVH due to prematurity between 2003 and 2012. The patients ranged in gestational age from 23.0 to 32.0 weeks, with an average age at first shunting procedure of 6.1 weeks (range 3.1-12.7 weeks). Three patients were managed with surgery. Patients received long-term radiographic (mean 7.1 years; range 3.4-12.2 years) and clinical (mean 7.8 years; range 4.6-12.2 years) follow-up.
The frequency of TFV following VP shunting for neonatal posthemorrhagic hydrocephalus was found to be 15.4%. Three (37.5%) patients presented with symptoms of posterior fossa compression and were treated surgically. All of these patients showed signs of radiographic improvement with stable or improved clinical examinations during postoperative follow-up. Of the 5 patients treated conservatively, 80% experienced stable ventricular size and 1 patient experienced a slight increase (3 mm) on imaging. All of the nonsurgical patients showed stable to improved clinical examinations over the follow-up period.
The frequency of TFV among premature IVH patients is relatively high. Most patients with TFV are asymptomatic at presentation and can be managed without surgery. Symptomatic patients may be treated surgically for decompression of the fourth ventricle 23).


Of 1044 aneurysms treated, 3 patients were identified who required fourth ventricular shunting, for the treatment of the isolated ventricle. All 3 patients underwent microsurgical clip obliteration of their aneurysms and had subsequent frontal approach ventriculoperitoneal cerebrospinal fluid diversion. These patients had no evidence of infection of the cerebrospinal fluid as measured by serial cultures. Subsequently, all 3 patients presented in a delayed fashion with symptoms attributable to a dilated fourth ventricle and syringomyelia or syringobulbia. Either exploration or percutaneous tapping confirmed the function of the supratentorial shunt. These patients then underwent fourth ventriculoperitoneal cerebrospinal fluid diversion by the use of a low-pressure shunt system. The symptoms attributable to the isolated fourth ventricle resolved rapidly in all 3 patients after shunting. This clinical improvement correlated with the fourth ventricular size.
Isolated fourth ventricle, in an adult, is a rare phenomenon associated with intracranial posterior circulation aneurysm rupture treated with microsurgical clip obliteration. Fourth ventriculoperitoneal cerebrospinal fluid diversion is effective at resolving the symptoms attributed to the trapped ventricle and associated syrinx 24).


Between February 1998 and February 2007, 12 children were treated for TFV in Dana Children’s Hospital by posterior fossa craniotomy/craniectomy and opening of the TFV into the spinal subarachnoid space. The authors performed a retrospective analysis of relevant data, including pre- and postoperative clinical characteristics, surgical management, and outcome.
Thirteen fenestrations of trapped fourth ventricles (FTFVs) were performed in 12 patients. In 6 patients with prominent arachnoid thickening, a stent was left from the opened fourth ventricle into the spinal subarachnoid space. One patient underwent a second FTFV 21 months after the initial procedure. No perioperative complications were encountered. All 12 patients (100%) showed clinical improvement after FTFV. Radiological improvement was seen in only 9 (75%) of the 12 cases. The follow-up period ranged from 2 to 9.5 years (mean 6.11 ± 2.3 years) after FTFV 25).


Between January 1986 and December 1995, Eder et al., treated 292 children younger than 16 years for hydrocephalus: 7 (2.4%) developed an isolated IV ventricle, and 5 of these were symptomatic with posterior fossa signs. These 5 patients required posterior fossa shunting, after which their neurological status improved. However, 1 week and 6 weeks after surgery, respectively, 2 patients developed new cranial nerve deficits related to a slit-like IV ventricle with secondary irritation of the brain stem by the IV ventricular catheter. Shortening the catheter and replacing the valve eliminated the cranial nerve palsies, implying that these complications were not caused by direct injury of the brain stem during placement of the shunt. Alternative surgical techniques and the use of different (flow-regulating) valves may avoid such complications 26).


Isolated fourth ventricles were diagnosed by computed tomography (CT) in 16 children in a 3 year period. They all had shunting of the lateral ventricles for hydrocephalus, and all needed subsequent shunt revisions. Seven patients without signs of raised intracranial pressure clinically had new posterior fossa signs at different intervals after lateral ventricular shunting. The clinical findings in the other nine patients were much less specific and in some cases the isolated fourth ventricle was an incidental finding. CT is essential for the diagnosis. The isolated fourth ventricle needs to be differentiated from posterior fossa cysts and cystic tumors. Shunting of the fourth ventricle improved the clinical condition in six of 14 children 27).


Signs of cerebellar dysfunction combined with signs suggestive of shunt malfunction developed in three children with obstructive hydrocephalus. Shunt function was normal. In all cases, the cerebellar signs persisted and computerized tomography scans revealed enlargement of the fourth ventricle. Shunting of the fourth ventricle returned the patients to normal function 28).

Case reports


Trapped Fourth Ventricle With Vasogenic Edema 29).


A 28-year-old female who had previously undergone treatment of intracerebral hemorrhage and meningitis developed a hydrocephalus with TFV. After 3 years she developed disturbance of walking and coordination. Cranial-CT revealed an enlargement of the shunted fourth ventricle as a result of shunt dysfunction. Furthermore a cervical syringomyelia developed. The patient underwent a revision of a failed fourth ventriculo-peritoneal shunt. Postoperatively, syringomyelia resolved within 6 months and the associated neurological deficits improved significantly. An insufficiency of cerebrospinal fluid draining among patients with TFV can be associated with communicating syringomyelia. An early detection and treatment seems important on resolving syringomyelia and avoiding permanent neurological deficits. Ventriculo-peritoneal shunt in trapped fourth ventricles can resolve a secondary syringomyelia 30).


A 4-year-old girl with a ventriculoperitoneal shunt presented with complaints of ataxia and altered consciousness. These symptoms were subacute at onset and progressive in nature.
Radiological evaluation revealed a trapped fourth ventricle with brainstem compression, associated with abnormal diffuse diencephalic signal changes compatible with edema. The entrapment was managed by foramen magnum decompression, resulting in complete symptom resolution and improvement in the abnormal magnetic resonance findings.
While trapped fourth ventricle is a well-described entity, we could not find a similar reported case where such an acute clinical syndrome was associated with such a distinct radiological picture 31).

A 20-year-old man with complex hydrocephalus and trapped fourth ventricle underwent a suboccipital placement of a VP shunt. Postprocedure patient developed double vision. Magnetic resonance imaging showed that the catheter was penetrating the dorsal brainstem at the level of the pontomedullary junction. Patient was referred to our Neuroendoscopic Clinic. Physical exam demonstrated pure right VI cranial nerve palsy. Patient underwent flexible endoscopic exploration of the ventricular system. Some of the endoscopic findings were severe aqueductal stenosis and brainstem injury from the catheter. Aqueductoplasty, transaqueductal approach into the fourth ventricle, and endoscopic repositioning of the catheter were some of the procedures performed. Patient recovered full neurological function. The combination of endoscopic exploration and shunt is a good alternative for patients with complex hydrocephalus. A transaqueductal approach to the fourth ventricle with flexible scope is an alternative for fourth ventricle pathology 32).


Cranial nerve palsy is rarely seen after shunt placement in an isolated fourth ventricle. In the few reports of this complication, neuropathies are thought to be caused by catheter injury to the brainstem nuclei either during the initial cannulations or after shrinkage of the fourth ventricle. The authors treated a child who suffered from delayed, progressive palsies of the sixth, seventh, 10th, and 12th cranial nerves several weeks after undergoing ventriculoperitoneal shunt placement in the fourth ventricle. Magnetic resonance imaging revealed the catheter tip to be placed well away from the ventricular floor but the brainstem had severely shifted backward, suggesting that the pathogenesis of the neuropathies was traction on the affected cranial nerves. The authors postulated that the siphoning effect of the shunt caused rapid collapse of the fourth ventricle and while the cerebellar hemispheres were tented back by adhesions to the dura, the brainstem became the only mobile component in response to the suction forces. Neurological recovery occurred after surgical opening of the closed fourth ventricle and lysis of the basal cistern adhesions, which restored moderate ventricular volume and released the brainstem to its normal position 33).


The first reported case was a patient with cysticercosis meningitis and communicating hydrocephalus in whom signs of a posterior fossa mass developed a few months after shunting of the lateral ventricles . Air studies and posterior fossa exploration demonstrated an encysted fourth ventricle due to occlusion of its outlets as well as of the aqueduct 34).

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