Key-words:
Cavernous carotid aneurysm - high-flow bypass - radial artery graft
Introduction
Cavernous carotid aneurysms (CCAs) account for 2%–9% of all intracranial aneurysms.[[1]] Most often, they remain asymptomatic and are detected incidentally. They may attain
large size and present with mass effect causing cranial neuropathies. A transitional
variant with intradural component may rupture, causing SAH and rarely intracavernous
rupture leads to direct carotid-cavernous fistula.[[2]],[[3]],[[4]] There are lots of controversies regarding management of CCAs. Management options
include surgical and endovascular methods with aim of exclusion of aneurysm from circulation
and maintenance of normal cerebral perfusion. This can be achieved by parent artery
occlusion by surgical or endovascular method with or without bypass procedures, coiling
(balloon or stent assisted), flow diverters and liquid embolic agents.[[5]]
We present a case of CCA managed by high-flow bypass with radial artery (RA) interposition
graft followed by carotid ligation.
Case Report
A 66-year-old female patient was incidentally diagnosed with right CCA and left side
internal carotid artery (ICA) paraclinoid aneurysm. She underwent surgery for the
paraclinoid aneurysm was 1 year back. Option of conservative treatment with follow-up
was explained to the patient; however, she was very apprehensive and decided to go
for surgery. Four-vessel digital substraction angiography (DSA) was performed to study
the aneurysm anatomy in further details as well as to see the cross flow. Aneurysm
sac size was 8.9 mm × 8.4 mm with 2.0 mm neck diameter and there was no evidence of
cross flow [[Figure 1]].
Figure 1: Three-dimensional digital substraction angiography anteroposterior view (a) showing
right side cavernous carotid aneurysm, measuring 9.3 mm x 9.7 mm with 8.3 mm neck
diameter (b). Right and left internal carotid artery injection revealed poor cross
flow through anterior communicating artery (c and d)
Surgical procedure
Position and incision
The patient was positioned supine with head turned to 30° to the left side. Superficial
temporal artery (STA) was palpated and a frontotemporal curvilinear incision reaching
till midline was marked accordingly. Neck incision started above the level of angle
of mandible along the anterior border of sternocleidomastoid muscle and curved anteriorly
along the superior border of thyroid cartilage. A curvilinear incision along the medial
border of brachioradialis muscle of right forearm was marked for RA graft. Proximal
end was approximately 2 centimeters below elbow crease and distal end was just proximal
to wrist crease [[Figure 2]].
Figure 2: Head position and scalp incision (a and b), neck incision (c) and incision for radial
artery graft (d)
Neck exposure
Platysma was incised to expose the sternocleidomastoid and dissection toward the anterior
border of sternocleidomastoid was done to identify parotid gland. Greater auricular
nerve was preserved and external jugular vein was sacrificed. Posterior belly of digastric
muscle was dissected from carotid sheath. Common facial vein was encountered which
was dissected carefully to preserve hypoglossal nerve. Common facial vein was ligated
and cut. Descending loop of ansa cervicalis and hypoglossal nerve was mobilized anterosuperiorly
to completely expose carotids. Carotid sheath was incised and carotid bifurcation,
ICA, external carotid artery (ECA) and superior thyroid artery was exposed [[Figure 3]]a.
Figure 3: (a) Carotid bifurcation, internal carotid artery, and external carotid artery. (b)
Superficial temporal artery with frontal and parietal branch harvested from scalp
Craniotomy and superficial temporal artery harvesting
Parietal and frontal branches of STA were dissected from the flap [[Figure 3]]b. Frontotemporal craniotomy was done. Extratemporal bone toward the temporal pole
was removed to make way for RA graft.
Radial artery graft
Preoperatively collateral circulation with ulnar artery was confirmed with Allen's
test as well as imaging. Incision was made as described above. Fascial sheath between
brachioradialis and flexor carpi radialis muscle was incised and RA was exposed [[Figure 4]]. It was dissected free from surrounding soft tissue and accompanying concomitant
veins. The artery was lifted using vascular tape and small muscular branches were
coagulated and cut. Once the artery was completely free, it was left in situ. Length
of the graft was 18 cm.
Figure 4: (a) Harvesting radial artery graft. (b) Technique of making tunnel for radial artery
graft with help of finger dissection and Kelly forceps. (c) Radial artery graft is
tied with silk suture and passed into the tunnel through the chest tube
Tunneling
Submandibular route was used for RA graft. Index finger was inserted between posterior
belly of digastric and hypoglossal nerve. Blunt dissection was done with finger and
styloid process was palpated. At this point finger was moved forward toward the anterior
temporal region. A Kelly forceps was inserted from cranial end beneath the zygoma
and temporalis muscle and its tip was felt by the finger inserted from neck. Then,
the Kelly forceps was advanced into the passage made by finger to come out of cervical
incision. A 24 Fr chest tube threaded with 1.0 silk suture was guided through the
tunnel with help of Kelly forceps. On the cranial side, RA graft is tied to the 1.0
silk suture and suture is pulled from cervical side to position the RA graft inside
the chest tube [[Figure 4]].
Anastomosis
Superficial temporal artery-M3 anastomosis
Purpose of this bypass was to prevent ischemic complications at the time of RA-M2
anastomosis that requires longer temporary proximal blockade (double insurance bypass).
This also helps in monitoring the brain surface middle cerebral artery (MCA) pressure
to assess the patency of RA graft.
Connective tissue around STA stump was thoroughly removed. Stump was incised at an
angle of 60 degrees and one end was further incised for the same length as the diameter
of distal end.
Margin was stained with violet dye. Arteriotomy site on M3 was marked and it was trapped
with temporary clips. Arteriotomy was done and end to side anastomosis was performed
with nylon 9-0 suture in interrupted fashion. Temporary occlusion time was 19 min.
Radial artery-M2 anastomosis
RA graft was flushed with heparinized saline and chest tube was removed from cranial
end. Stump of RA graft was prepared and arteriotomy site on M2 was temporarily trapped
[[Figure 5]]. Nylon 9-0 sutures were used for anastomosis. Temporary occlusion time was 25 min.
Before removing the temporary clips from MCA, a temporary clip was placed over RA
graft close to anastomosis site.
Figure 5: Preparation for anastomosis (a) preparation of radial artery graft stump for anastomosis
(b) arteriotomy at M2 for radial artery-M2 anastomosis (c) arteriotomy at External
carotid artery which has been enlarged using vascular punch
External carotid artery-radial artery anastomosis
RA graft stump was widely cut to make a large aperture. Arteriotomy was done in ECA
after temporary trapping of ECA. Opening was enlarged with help of vascular punch
[[Figure 5]]. End to side anastomosis was performed with prolene 7-0 suture.
Monitoring of brain surface pressure
This was done to ensure the patency of graft as well as to assess intraoperatively
whether STA-MCA anastomosis is sufficient to maintain adequate brain perfusion or
high-flow bypass is required. A cannula was inserted into the branch of STA and it
was connected to pressure transducer. STA trunk was clamped and the transducer indicates
the brain surface pressure of MCA. ICA was clamped and there was significant fall
in pressure. After releasing STA clamp, MCA pressure increased, but still it was around
60% of baseline. Hence, the decision for high-flow ECA-MCA bypass was made. After
performing ECA-MCA bypass with RA interposition graft, STA and RA graft was unclamped
and MCA stump pressure was measured. MCA pressure increased to baseline level indicating
sound graft patency as well as adequate brain perfusion [[Figure 6]].
Figure 6: BP and middle cerebral artery pressure measured through transducer connected to branch
of superficial temporal artery before internal carotid artery occlusion (a), after
internal carotid artery occlusion (b), internal carotid artery occluded but superficial
temporal artery unclamped to fill middle cerebral artery (c) and internal carotid
artery occluded and middle cerebral artery filled through radial artery graft (d)
Dual imaging video angiography and intraoperative Doppler probe were also used to
confirm graft patency [[Figure 7]]. Cervical ICA was double ligated and cut.
Figure 7: (a) Final view after radial artery-M2 and superficial temporal artery-M3. (b) Dual
imaging video angiography revealing robust flow through both radial artery-M2 and
superficial temporal artery-M3 anastomosis
Postoperatively, the patient was extubated and there was no neurological deficit.
Three-dimensional computerized tomography angiography revealed good flow through the
graft into MCA and no anterograde flow in aneurysm [[Figure 8]].
Figure 8: Postoperative angiography anteroposterior (a) and lateral (b) view showing good flow
through radial artery graft and nonvisualization of aneurysm
Discussion
CCAs have relatively benign natural history. As per the International Study of Unruptured
Aneurysm Trial, 5 years rupture rate for <13 mm, 13–24 mm and >25 mm size CCAs is
0%, 3.0% and 6.4%, respectively.[[6]] If rupture, they lead to direct caroticocavernous fistula (CCF) or rarely cause
SAH in cases with intradural component. Fatal epistaxis due to sphenoid bone erosion
is a rare complication. Spontaneous thrombosis of giant CCA had also been reported.[[7]] Stiebel-Kalish et al. published the follow-up results of treated and untreated
patients of CCAs. Among 111 untreated patients, 2% had stroke, 1% had SAH, 1% had
direct CCF, and 6% developed compressive optic neuropathy leading to overall 10% adverse
events rate.[[8]],[[9]]
CCAs can be managed by open surgical methods such as clipping, trapping with or without
bypass or endovascular methods. Endovascular coiling with or without stent carry a
high rate of recanalization and re-treatment.[[10]],[[11]] Recently, pipeline devices had shown promising results, however, several studied
have reported significant hemorrhagic and thrombotic complications.[[12]],[[13]],[[14]] Direct surgical methods such as clipping and trapping are technically challenging
and carries high risk of complications. Indirect methods such as high-flow bypass
with ICA ligation can achieve aneurysm obliteration with acceptable morbidity and
mortality rates.[[15]],[[16]]
Murai et al. published results of 8 cases of giant CCAs managed by ECA-RA-MCA bypass
with cervical ICA occlusion. Complete aneurysmal thrombosis was achieved in 100% cases
and 87.5% patients showed symptomatic improvement. Postoperatively, one patient (12.5%)
had small ipsilateral frontal infract, one patient (12.5%) developed transient trochlear
nerve palsy, and one patient (12.5%) had one episode of seizure probably due to hyperperfusion
syndrome.[[17]]
Shimizu et al. performed high-flow bypass with ICA occlusion in six patients with
CCAs with acceptable clinical and hemodynamical results.[[18]]
In this reported case, CCA was incidentally detected. In view of poor cross flow on
DSA, we decided to go for revascularization with carotid occlusion. Option of endovascular
treatment was also explained to patient and relatives; however, they opted for surgical
management.
There is no clear cut guideline to decide whether revascularization should be done
or not after ICA is sacrificed. One policy is to evaluate cerebrovascular reserve
preoperatively by Balloon occlusion test (BOT), single-photon emission computed tomography
or positron emission tomography and to decide the need for revascularization. Risk
of ischemic complications is 32%–60%, if carotid occlusion is performed without preoperative
evaluation of cerebrovascular reserve.[[19]],[[20]] Risk of infarction is 22%, if revascularization is not done on the basis of preoperative
BOT showing adequate cerebrovascular reserve. With additional revascularization in
patients showing adequate cerebrovascular reserve, risk of infarction comes down to
14%.[[21]],[[22]] Other problem with parent artery occlusion without revascularization is delayed
de novo aneurysm formation or enlargement of existing aneurysms due to increased hemodynamic
stress.[[23]] This is why we decided to go for revascularization without performing preoperative
BOT. BOT also helps in deciding between low-flow and high-flow bypass. High-flow and
low-flow STA-MCA bypass are performed for patients with poor and moderate cerebrovascular
reserve, respectively.[[24]] We intraoperatively decided to go for high-flow bypass by measuring MCA pressure
after STA-M3 anastomosis and ICA temporary occlusion using pressure transducer connected
to a branch of STA.
Although high-flow bypass appears to be a very extensive technique, it is minimally
invasive to brain except for the temporary occlusion part. To reduce the temporary
occlusion-related ischemic complications, we performed STA-M3 anastomosis in our case
before going for RA-M2 anastomosis. Occlusion time for STA-M3 anastomosis is less
as compared to RA-M2 anastomosis leading to less chances of ischemic complications.
Second, Occlusion at more proximal segment (M2) carries more risk as compared to distal
occlusion (M3).[[15]],[[25]],[[26]] Hence, by performing STA-M3 anastomosis, during RA-M2 anastomosis, MCA territory
is supplied by STA and risk for ischemic complications is minimized.
Conclusion
High-flow bypass with RA interposition graft followed by cervical ICA ligation is
an effective management option for CCAs. Performing STA-MCA bypass as insurance bypass
and intraoperative measurement of MCA stump pressure adds to the safety of the procedure.
Complications related to surgical technique are minimal, when performed by expert
surgeon at high volume centers.
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.
