Key-words: Anterior communicating aneurysm - clipping - neuroendoscope
Introduction
The goal of surgical management of intracranial aneurysm is to exclude the aneurysm
from the circulation while preserving the parent artery, its branches, and perforators
while avoiding damage to the adjacent cranial nerves and brain parenchyma.[[1 ]] Hence, it is crucial to achieve a good view of regional anatomic features, including
the relationships between the aneurysm neck, wall and parent vessel, branches, perforators,
and adjacent cranial nerves before, during, and after clipping. This is not always
possible even with most sophisticated microscope available. This problem is overcome
by the intraoperative use of endoscope, which permits observation of areas considered
blind under the microscope and allows close-up view of regional anatomic features.
To enhance the intraoperative visualization of the regional anatomy, endoscopy was
introduced during microneurosurgery for cerebral aneurysms by Fischer and Mustafa.[[2 ]] In 1977, Apuzzo et al. applied the side-angled rigid endoscope to neurosurgical
procedures and reported its great value for assessing the confirmation of clip placement
in a case of the basilar tip aneurysm.[[3 ]] Perneczky and Fries elaborated on the general principles of endoscope-assisted
microsurgery and described three advantages of the endoscope as follows:[[4 ]],[[5 ]] (1) increased light intensity while approaching an object, (2) clear depiction
of details in close-up positions, and (3) extended viewing angles. Therefore, the
surgeon can inspect hidden structures, dissect perforators at the back of aneurysm,
identify important vessels without retraction of aneurysm, and check for the completion
of clipping.
Anterior communicating (A-com) artery anatomy is very complex; there are total of
seven major vessels (bilateral A1, bilateral A2, bilateral recurrent Heubners arteries,
and A-com artery) and multiple small perforators. A-com aneurysm can have anterior,
superior, inferior, and posterior projections hiding these vessels and perforators
during pterional craniotomy. Hence, it is very important to have precise anatomical
information before and after the clipping of aneurysm which is possible with simultaneous
use of microscope and endoscope. Intraoperative use of endoscope in A-com aneurysm
surgery is not individually assessed according to our knowledge. Hence, we present
our experience with the use of intraoperative endoscopy in A-com aneurysm surgery.
Materials and Methods
We studied 25 serial cases of A-com aneurysm which were operated between November
2018 and October 2019 (all were unruptured aneurysms) in Bantane Hospital, Fujita
Health University, Japan. For these patients, intraoperative endoscopy was done.
Instrumentation
We used rigid rod lens endoscope(A81000A, Olympus, Germany) for microsurgical procedures.
Rigid endoscope of diameter 2.4 mm and 4.0 mm with angles of 0° and 30° was used.
Illumination was provided by the Xenon light source. The endoscope was attached to
a three-chip camera and the images were viewed on video monitor (Olympus, Germany).
Operative technique
The pterional craniotomy was done in the usual manner. The initial exposure was performed
under the microscope. The endoscope was then introduced into the surgical field with
observation through microscope, and the endoscopic image is viewed on the monitor.
An initial view of the aneurysm and surrounding structures is obtained with the endoscope
for the assessment of regional anatomy. Further, dissection and exposure of the aneurysm
was performed under the microscope. Once aneurysm was exposed, we did preclipping
indocyanine green (ICG) and examination with endoscope. The aneurysm neck was then
clipped usually with microscopic observation and occasionally with endoscopic observation
assistance. After aneurysm clipping, ICG study and endoscopic inspection were repeated.
The inspection includes assessment of the completeness of aneurysm clipping, inadvertent
inclusion of the parent vessel in the clip, and pressure on surrounding vital structures
such as the cranial nerves. If any of these are encountered, necessary changes were
made in operative decisions such as readjustment of the clip, application of the second
clip, or release of perforator compromise.
Results
Of 25 A-com aneurysm patients operated, ten patients were male, while 15 patients
were female (male-to-female ratio of 1:1.5) with an average age of 67 years. Following
observations were made [[Table 1 ]]. The distribution of patients according to the age and size of aneurysm is as shown
in [[Table 2 ]] and [[Table 3 ]]. In cases with aneurysm size >5 mm, we found more percentage of abnormal findings
(42.9%) on endoscope which lead to change in the intraoperative management [[Table 3 ]]. However, this difference was not found statistically significant (P = 0.428).
In six out of 25 patients, endoscope has given additional information over microscope
and ICG which changed the operative plan [[Table 4 ]]. In three patients after clip application, there was residual aneurysm visualized
below the clip on endoscope (intraoperative ICG showed complete obliteration of aneurismal
sac). Hence, the second clip application or readjustment of the clip was done in those
patients. In one patient, incomplete clipping (distal tip of the clip was not across
the aneurysm) was visualized on endoscope (intraoperative ICG did not show any obvious
refilling of aneurysm) and needed readjustment of the clip. In one patient, distal
tip of the clip was seen compressing on the optic nerve on endoscopic inspection and
needed readjustment of the clip. In one patient, the clip was seen compressing the
perforator on endoscopy, and hence, perforator was separated and clip readjustment
was done. Postoperative computed tomography angiography did not reveal any neck remnant,
and no patients have required further interventional or surgical treatment.
Table 1: Endoscopic observations
Table 2: Age group
Table 3: Size group
Table 4: Change in operative plan
Illustrative cases
Case 1: Residual aneurysm under the clip
A 69-year-old female was diagnosed with A-com aneurysm [[Figure 1 ]]a with left A1 dominance. The patient was operated with left pterional craniotomy
with a transsylvian approach. Intraoperatively, aneurysm was found as shown in [[Figure 1 ]]b. After application of the first clip [[Figure 1 ]]c, ICG was done suggestive of complete occlusion of the aneurismal sac [[Figure 1 ]]d and no residual. After doing intraoperative endoscopy, we found a residual aneurysm
below the first clip [[Figure 1 ]]e, hence, the second clip application was needed for residual aneurysm [[Figure 1 ]]f.
Figure 1: (a) Preoperative three-dimensional computed tomography scan showing anterior communicating
aneurysm. (b) Intraoperative microscopic image showing aneurysm (shown by black arrow),
ipsilateral A1 and A2. (c) Intraoperative microscopic image showing completely clipped
anterior communicating aneurysm. (d) Intraoperative microscopic post indocyanine green
image showing completely clipped aneurysm with no indocyanine green in aneurismal
sac. (e) Intraoperative endoscopic image showing residual aneurysm sac under the clip.
(f) Intraoperative microscopic image showing second clip applied for residual aneurysm
Case 2: Perforator compromise
A 79-year-old female presented with A-com aneurysm with right A1 dominance [[Figure 2 ]]a. The patient was operated with right pterional craniotomy with transsylvian approach,
and aneurysm was visualized as shown in [[Figure 2 ]]b. Preclipping endoscopy was done [[Figure 2 ]]c which showed small perforator adherent to dome of the aneurysm, but the aneurysm
neck was free. Aneurysm was clipped under the microscope [[Figure 2 ]]d, but no perforator compromise was noticed, however, after doing postclipping endoscopy
[[Figure 2 ]]e, we found that perforator is kinked and part of its wall is caught in the clip,
hence, the readjustment of the clip was done [[Figure 2 ]]f and perforator was separated.
Figure 2: (a) Preoperative three-dimensional computed tomography scan showing anterior communicating
aneurysm with the right A1 dominance. (b) Intraoperative microscopic image showing
aneurysm (a), right A1, left A1, and perforator (as shown by arrow). (c) Intraoperative
endoscopic image showing perforator (shown by arrow) adherent to dome of the aneurysm.
(d) Intraoperative microscopic image showing clipped aneurysm. (e) Intraoperative
endoscopic view showing perforator getting kinked and part of its wall caught in the
clip. (f) Intraoperative endoscopic view showing perforator (shown by black arrow)
separated from the clip
Incomplete clipping
A 71-year-old female presented with A-com aneurysm with right A1 dominance [[Figure 3 ]]a. The patient was operated with right pterional craniotomy and transsylvian approach,
and aneurysm was visualized, as shown in [[Figure 3 ]]b. Preclipping endoscopy was done [[Figure 3 ]]c, which was showing multiple perforators at the neck of aneurysm which were separated
and aneurysm was clipped with two clips [[Figure 3 ]]d. Postclipping endoscopy was done [[Figure 3 ]]e, which was showing the second clip was not across aneurysm suggestive of incomplete
clipping, hence, the readjustment of the second clip was done [[Figure 3 ]]f.
Figure 3: (a) Preoperative three-dimensional computed tomography scan showing anterior communicating
aneurysm with the right A1 dominance. (b) Intraoperative microscopic view of aneurysm
(a). (c) Intraoperative endoscopic view clearly showing perforator at the neck of
aneurysm (shown by black arrow). (d) Intraoperative microscopic view showing two clips
applied. (e) Intraoperative endoscopic view showing second clip not across the aneurysm
suggestive of incomplete clipping. (f) Intraoperative endoscopic view showing clip
position after the second clip readjustment
Discussion
History
The first endoscopic neurosurgical procedure was performed in 1910 by V.L.L'Espinasse,
an urologist from Chicago.[[6 ]] He used a small rigid cystoscope to cauterize the choroid plexus of two hydrocephalic
infants. In 1922, Dandy[[7 ]] coined the term “ventriculoscope” and described the use of a rigid Kelly cystoscope
to inspect the lateral ventricles of two hydrocephalic infants. In 1923, Mixter[[8 ]] described the first successful third ventriculostomy procedure. In 1930, Tracy
Putnam working with the urethroscope described by Mixter, treated a series of children
with communicating hydrocephalus through choroid plexus coagulation.[[9 ]] Fukushima introduced his ventriculofiberoscope in 1973. Fukushima[[10 ]] described three important phases in the development of the application of endoscopic
devices. The first phase (from 1910 to 1950s) involved endoscopic diagnosis and coagulation
of choroid plexus to treat hydrocephalus; the second phase (initiated in the early
1970) involved the application of flexible fiber endoscopes; and the third phase involves
the recent revival of endoscope assisted, minimally invasive surgical procedures.
Advantages of endoscope in aneurysm surgery
The endoscope with its higher magnification, better observation, and additional illumination
can provide us with information that may not be available with the microscope. It
can look around corners and allow observation of areas considered blind under the
microscope.[[6 ]]
The endoscope provides a second perspective on the regional anatomic features and
enables surgeons to develop a mental three-dimensional image of the aneurysm and its
surroundings. During aneurysm surgery, maneuvers such as retraction or unnecessary
dissection performed under inadequate microscopic observation can be dangerous. The
straight line of view imposed by microscope results in inadequate observation of structures
that lie behind the aneurismal sac. The use of endoscope during aneurysm surgery can
overcome this “microscopic blind eye” and avoid disastrous complications. During endoscope-assisted
aneurysm surgery, the endoscope can be used to inspect hidden structures, dissect
perforators at the back of the aneurysm, identify important vessel segments without
retraction of the aneurysm or arteries, and check for the completeness of clipping.[[5 ]]
Perneczky and Fries enumerated five ways in which microscopic and endoscopic images
can be observed at the same time.[[4 ]] We connect the scope to a three-chip camera and the image is viewed on the monitor
placed in front of the surgeon. The microscopic image is simultaneously monitored
on a video monitor placed next to the endoscopic image monitor.
Other authors experience
In our experience, the use of endoscope changed the operative plan in six out of 25
cases (24% cases) of A-com aneurysm. In a series of 54 cases reported by Taniguchi
et al.,[[11 ]] the endoscope clarified the detailed additional regional anatomy in 9 cases (16.7%),
and the surgeons reapplied the clip on the basis of endoscopic information obtained
after the initial clipping in 5 cases (9.3%). In a series of studies by Kalavakonda
et al.,[[1 ]] the endoscope was used to observe the clip position in 75 of 79 cases (95%) and
anatomic features in 26 (33%). In 15 (19%) aneurysms, key information such as parent
artery, branches, perforators, the neck and back wall of the aneurysm, and completeness
of clipping of the neck and inclusion of the parent artery in the clip could be visualized
through the endoscope. The clip repositioned because of residual neck or inclusion
of the parent artery in six cases, and the clip position was readjusted because of
compression of the optic nerve in one case.
In a report by Fischer et al.,[[12 ]] the endoscope was used to gain additional topographic information before clipping
in 150 of 180 cases (83%). Depending on the endoscopic findings, rearrangement of
the applied clip or additional clipping was found to be necessary in 26 of 130 cases
(20%). In recent report by Galzio et al.,[[13 ]] the endoscope provided additional information in 147 cases (71.4%), and clipping
under the endoscopic view was done in 42 cases (20.4%). Reapplication of the clip
was required in 42 cases (20.4%).
Our study findings coincide with these reports regarding application or readjustment
of the clip rate (24%). Our study specifically deals with the use of endoscope in
A-com aneurysm, for which no data are available in current literature. Apart from
the use of endoscope for inspection of aneurysm, it could be also used for endoscopic
ICG video angiography as described by Yoshioka and Kinouchi.[[14 ]]
Complications
We encountered no major complication related to the use of endoscope. Taniguchi et
al.[[11 ]] encountered one patient with transient oculomotor palsy and one patient with an
asymptomatic cerebral contusion in a series of 48 patients with 54 aneurysms. Van
Lindert et al.[[15 ]] observed accidental rupture of four aneurysms in a series of 197 aneurysms. Yamada
et al.[[16 ]] described the single-center experience for the intraoperative use of endoscope
in aneurysm surgery, they did not report any complication related to the use of endoscope.
The morbidity in their case series was not related to use the endoscope.
Disadvantages
Some disadvantages of the endoscope have been reported as follows:[[1 ]]
(1) the endoscope can cause rupture of the aneurysm during initial inspection, (2)
three-dimensional views are not possible, (3) when there is blood in the operative
field, the endoscope is useless, (4) there is still a lack of instrumentation specifically
designed for endoscopic surgery, and (5) bimanual surgery is impeded when the scope
is handhold.
Conclusion
Simultaneous endoscopic and microscopic guidance can reveal important information
hidden from the microscope and it can avoid potential complications. This method increases
the safety and durability of the A-com aneurismal clipping.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
