Prof. Bryan Young
BMC Neurology
Dear Prof. Young:
Thank you for the opportunity to revise our manuscript entitled “The effectiveness of
neuroendoscopic versus non-neuroendoscopic procedures in the treatment of lateral ventricular
cysts: a retrospective medical record review study” for resubmission to BMC Neurology. We
would also like to thank the reviewers for providing valuable comments. Our responses to those
comments follow.
Reviewer #1
Comment:
It is unclear how patients were selected for either neuroendoscopy or open surgery. The abstracts
indicate that patients were randomly assigned to the groups but there are no details of the
randomization process. The authors should clarify how patients were assigned to the two
operative groups.
Response:
The neurosurgeon initially used open surgery procedures and then gradually transitioned to
endoscopic procedures. Therefore, the patients were not randomly assigned. The abstract has
been revised to reflect the fact that there was no randomization.
Comment:
Although I believe the authors are only discussing intraventricular arachnoid cysts, throughout
the paper, they refer to tumours. This results in confusion as to what the actual patient population.
References to tumour throughout the paper should be replaced with the term cyst.
Response:
We agree and have changed “tumor” to “cyst” where appropriate.
Comment:
While the neuroendoscopic technique is described in detail, the technique for open surgery is less
clear. More details regarding open surgery should be provided such as incision and craniotomy
size.
Response:
We have added more details on the open surgery procedure. (see the third paragraph under the
heading Surgical Method on pg 7)
Comment:
The authors refer to cysts being « almost » totally removed-clarify how degree of resection was
objectively measured.
Response:
Determining the degree of cyst removal during the operations was based on the normal anatomy
of the ventricle. When the walls of the lateral ventricle, choroid plexus and interventricular
foramen were revealed as normal and CSF circulation was restored then the cyst wall can be
considered to be completely removed.
Comment:
There remain scattered grammatical errors throughout the paper.
Response:
The paper has been reviewed again for grammar errors. Those found were corrected.
Comment:
It seems counter-intuitive that endoscopic management would yield a higher rate of cyst
resection than open surgery. The authors should provide a proposed explanation for why this is
so.
Response:
We have provided an explanation in the first paragraph of the Discussion section. We have
argued that the endoscopic approach improves visualization in tight spaces, particularly within
the lateral ventricle; increases the degree of freedom in creating corridors; etc.
Comment:
In the results section, the authors state that « most « fevers were non-infectious. Were any of the
fevers caused by an infection. If not, « most » should be removed. They should also provide an
explanation for the high fever rate in the endoscopy group.
Response:
Actually, all the fevers were non-infectious. We have revised the Results section to indicate this
(see pg 9). As we have indicated in our manuscript we believe that fevers were most likely the
result of intracerebroventricular rinsing during surgery.
Comment:
Did any patients have radiographic improvement without symptomatic improvement?
Response:
In the neuroendoscopy group, there was one case in which the symptoms were not relieved
following cyst resection 6 months after the operation. This patient later received a ventricularperitoneal shunt operation. But for most patients, the neuroendoscopic approach not only
removed the cyst but also restored the CSF circulation to the normal level.
Reviewer #2
Comment:
It is not clear whether this paper is primarily focused on the surgical treatment of arachnoid cysts.
The authors may want to specify that they are indeed reporting their experience in treating this
entity. A short description of arachnoid cyst would be a welcoming introduction to readers who
are not familiar with this problem.
Response:
We have clarified the aim of this study in the abstract. The study is focused on the surgical
treatment of arachnoid cysts. We have also provided a brief description of arachnoid cysts in the
introduction and cited the following reference: Westermaier T, Schweitzer T, Ernestus RI.
Arachnoid cysts. Adv Exp Med Biol 2012;724:37-50.
Comment:
Arachnoid cysts are more commonly found along the sylvian fissure (50%) and only 1% of them
are located at the lateral ventricle. The majority of the patients do not need surgical treatment.
Response:
Because a cyst in the lateral ventricle occludes the CSF circulation route it produces high ICP.
This situation requires surgical treatment. We have noted this requirement for surgery in the
Introduction. (see pg 4)
Comment:
In this study the authors presented their experience and outcome in using endoscopic technique
to resect these cysts at the lateral ventricles. They compared the outcomes of this approach to
that of craniotomy and shunting. In this study there are 26% more patients with gross total
resection in the endoscopic group than in the group treated with craniotomy; which may
explain the difference in the higher recurrence rate in the craniotomy group (20.5%).
Endoscopic approach definitely improves the visualization in tight spaces especially within the
lateral ventricle. This may be one of many contributing factors in the difference in the outcome.
However, its use in some cases are limited by the size of the ventricles. The authors may want to
re-think their discussion and expand on the interpretation of their data.
Response:
We have added to the Discussion section the view of Gangemi et al [25] that endoscopic cyst
fenestration from the lateral ventricle or third ventricle according to the extension of the cyst is a
relatively easy procedure and safe procedure which does not risk damaging the deep incisural
and quadrigeminal veins. (see pg 11) The reviewer noted that the use of the endoscopic approach
in some cases is limited by the size of the ventricles but we found in our cases of lesions in the
lateral ventricle that the ventricle had been stretched.
Comment:
The authors may want to offer an explanation why endoscopic approach allows more thorough
resection of the cyst; such as improved field of view, the degree of freedom in creating surgical
corridors etc.
Response:
As noted in a response above, the characteristics of the endoscope are helpful for completely
exposing the cyst and subsequent total removal of the masses.
Comment:
The subdural and fever may be explained by the presence of “chemical aseptic” meningitis and
decompressing the cyst into the subdural space, thus creates a transient "cystic subdural
fistula/shunt" hence less chance of recurrence. The merit of this study is its avocation in using
endoscopic technique and demonstrates it is more superior than open craniotomy ( a 64 vs 5.1
difference in marked improvement between the two groups.
Response:
Yes, we wanted to share our experience of using neuroendoscopy for treating arachnoid cysts
which demonstrated advantages over open craniotomy.