Keywords extracranial-intracranial high-flow bypass - giant cavernous internal carotid artery
dissecting aneurysm - radial artery graft - mono-ocular blindness
Introduction
Developed by Professor Gazi Yasargil in 1967, cerebral revascularization has become
an indispensable tool for managing patients with steno-occlusive intracranial ischemic
disease, complex intracranial aneurysms that require deliberate occlusion of a parent
artery and invasive skull base tumors.[1 ]
[2 ]
[3 ]
[4 ] Patients with complex, giant aneurysm have a 5-year mortality rate (80%). This means
that they have a worse prognosis.[1 ]
[5 ] As they cannot be treated by endovascular means, surgical clipping is the only option.
Clipping is usually not performed because of a wide neck, a fusiform aneurysm, major
parent vessels arising from the dome or the neck of the aneurysm, and because the
aneurysm must be decompressed under direct trapping, all of which necessitate some
form of bypass.[1 ]
[6 ] It is well recognized that extracranial-intracranial (EC-IC) high-flow bypass (HFB)
with therapeutic internal carotid artery (ICA) occlusion has become a treatment option
for giant ICA aneurysms.[7 ] Such treatment may be associated with many complications such as graft occlusion,
hemorrhage, infarct, ophthalmoplegia, hyperperfusion syndrome, cognitive disturbance,
etc. We report a case that developed postoperative mono-ocular blindness after having
EC-IC HFB with ICA ligation at the neck. So far to our knowledge, such complication
has not been reported in the literature.
Case Report
A 14-year-old right-handed girl presented with recent headache, eye ache, occasional
double vision, and occasional right-sided visual impairment for the past 2 months.
Neurologic examination revealed no abnormality, including visual acuity, visual field,
ocular movements, and funduscopy. Allen’s test in both sides was negative. All other
systemic examinations were within normal limit. Computed tomographic (CT) scan of
the head showed a right parasellar, large, mostly hyperdense space-occupying lesion
([Fig. 1 ]). CT angiogram of the brain showed giant dissecting aneurysm of right whole cavernous
segment of ICA ([Fig. 2 ]). After counseling with the patient party, a right-sided external carotid artery–radial
artery graft–middle cerebral artery (ECA-RAG-MCA [M2]) HFB was planned with ligation
of ICA at its origin in the neck.
Fig. 1 (A–D) Initial CT scan of the head sequential axial sections showing probable right internal
carotid artery giant aneurysm.
Fig. 2 (A–D) CTA of the brain showing right cavernous ICA giant fusiform aneurysm.
Operation
Under general anesthesia with endotracheal intubation, the patient was placed in supine
position. Head was fixed with three-pin head holder with neck extension and head turning
to the opposite side (30 degrees). Left upper limb was placed on a side “limb rest”
in extended elbow for radial artery (RA) procurement.
With longitudinal incision, the RA was harvested from brachial bifurcation at elbow
to wrist (20 cm). The artery was distended, and then it was kept in heparin and papaverine-mixed
normal saline. The forearm wound was closed with a drain.
A curve incision on the right side of the neck was made from the mastoid tip and extended
downward and medially 2 cm posterior to the angle of mandible to the midline. Sternocleidomastoid
muscle was retracted laterally. With further dissection, posterior belly of the digastric
muscle, hypoglossal nerve, internal jugular vein, common carotid, ICA, and ECA with
its branches were identified.
A right-sided precoronal post hairline curvilinear incision was made, and superficial
temporal artery (STA) and its parietal branch were procured and prepared for STA-MCA
insurance bypass as donor artery. A temporally extended pterional craniotomy was done.
Temporal bone was removed down to the middle fossa floor. A 26F thoracostomy tube
was passed from cervical wound to the middle fossa floor. RAG was passed from middle
fossa floor to cervical wound through the tube.
After durotomy, an STA-MCA (temporal M4) “insurance bypass” was done. After sylvian
dissection, temporal M2 was identified and prepared for bypass. RAG and temporal M2
bypass was made after systemic heparinization.
With the control of ECA just distal to bifurcation of common carotid artery (CCA),
an anastomosis was made between caudal end of RAG and ECA. The patency and flow through
the anastomoses and RAG were checked with micro Doppler. ICA was permanently ligated
with 1–0 silk at its origin in the neck. Cervical wound and craniotomy wound were
closed with drains.
Postoperative Course
The patient recovered well from anesthesia, but she developed right-sided complete
ophthalmoplegia with ptosis. After elevation of right-sided upper eyelid, her vision
was checked. Initially she said that she could not see with her right eye, but later
she confirmed that she could. However, there was blurring of vision on right side.
Funduscopy revealed pale fundus. Postoperatively, the patient was on aspirin and inj.
heparin. CT scan on first postoperative day (POD) showed no infarct or any gross hematoma
([Fig. 3 ]). CT angiogram on second POD showed right ECA-RAG-M2 bypass with absence of the
right ICA with aneurysm ([Fig. 4 ]). ICA seemed to be occluded up to its terminal bifurcation with absent right-sided
ophthalmic artery ([Fig. 5 ]). On second POD, check examination showed no vision in right eye as well as absence
of perception of light (PL) and projection of light (PR), but funduscopic examination
revealed no definite abnormality except pallor. Her ophthalmoplegia with ptosis recovered
completely within 4 weeks after operation, but there was no PL and PR in right side
with optic atrophy till last follow-up (8 months after operation).
Fig. 3 Postoperative CT scan of the head axial images (A–D) on first POD showing no gross infarct or hematoma.
Fig. 4 CTA of the brain axial images (A, B) on second POD showing presence of left ICA and left ophthalmic artery (arrow mark)
and absent of aneurysm, right ICA, and right ophthalmic artery (arrow mark).
Fig. 5 CTA of the brain (A–D) on second POD showing presence of left ICA and absent of aneurysm, right ICA with
patent right-sided high-flow EC-IC bypass.
Discussion
The credit for the first intracranial EC-IC bypass surgery goes to Donaghy and Yasargil
in 1967.[8 ] Lougheed then performed the first HFB 2 years later.[9 ]
[10 ] There are two major indications for EC-IC bypass surgery: (1) flow augmentation
and (2) flow replacement.[7 ]
High-flow bypass followed by ligation of the ICA is an effective treatment, but the
impact of abrupt occlusion of the ICA is unpredictable, especially on postoperative
cognitive function. HFB followed by ICA ligation can achieve good clinical outcomes.
This HFB (flow from the ECA to MCA via the RAG) cures the cavernous and supraclinoidal
ICA aneurysm and usually does not allow anterograde flow into the aneurysm.[11 ]
For HFB, RAG or great saphenous vein graft is usually used.[1 ]
[7 ]
The RA has the benefits of having a thick wall, a good size match to the M2, and providing
an intermediate flow that has been proven by many authors to be ideal to the brain.[12 ] The RA also has a proven long-term patency rate that has been accepted as superior
to great saphenous vein grafts. Pressure distension technique as described by Ramanathan
et al can effectively prevent spasm.[12 ]
There is a general agreement, to use end-to-side anastomosis as the main form of anastomosis
for most cases of cerebral revascularization.[1 ] A standard end-to-side anastomosis technique with two anchoring stitches at the
heel and at the toe is usually used.[1 ] Either slit or tear drop arteriotomy can be used during anastomosis.[1 ]
[12 ]
Studies on the short- and long-term patency of HF EC-IC bypass grafts have shown that
for the experienced neurovascular surgeon, patencies of 90 to 95% can be obtained.[7 ] In a study of 137 revascularizations, Sekhar and Kalavakonda reported an overall
graft patency rate of 95.6%.[13 ]
[14 ]
STA-MCA bypass has its own share of complications, the major ones being graft occlusion,
subgaleal hematoma, scalp necrosis, and postoperative intracranial hemorrhage.[1 ] Graft occlusion can be prevented by meticulous dissection of both the donor and
recipient arteries with minimal handling of the endothelium. Rarely post bypass hyperperfusion
syndrome can develop, which proved to be very difficult to treat.[9 ]
In a study of 137 revascularizations, Sekhar and Kalavakonda[13 ]
[14 ] reported an incidence of postoperative cerebral infarction of 16.8%. In addition
to graft thrombosis, cerebral infarction can be caused by a prolonged ischemia time
of the recipient segment of the MCA. Chazono et al[15 ] reported a case of intraoperative infarction with a clamping time of 65 minutes
and no infarction in three identical cases with clamping times of 30 to 40 minutes.
The risk of ischemia in the donor artery territory is related to the clamp time, which
is directly related to the learning curve. The risk can be reduced by raising the
mean arterial pressure greater than 20% above baseline and reducing metabolism by
burst suppression.[1 ]
Successful HFB using RAG with supportive STA-MCA bypass and ICA ligation does not
adversely affect postoperative cognitive function.[11 ]
In our case, the patient became blind postoperatively on right side (no PL or PR),
with normal left-sided vision. Her ophthalmoplegia recovered completely, but right-sided
eye vision remained absent. There was no surgical manipulation in the areas related
to intracranial ICA, ophthalmic artery, central retinal artery, and optic apparatus.
ECA clamping time was less than 25 minutes. There was no drop of perioperative pressure.
We think that this mono-ocular blindness occured due to ophthalmic artery/central
retinal artery occlusion by progression of thrombosis from the ICA to the ophthalmic
artery and then to central retinal artery, as it was supported by nonvisualization
of the opthalmic artery on right side compared with the left one. Initially funduscopy
revealed pallor fundus only (that can occur in cilioretinal sparing of central retinal
artery occlusion).[16 ] The thrombosis occurred when the patient was on inj. heparin and aspirin. Now the
question is, how can we prevent it? Yes, we may think of one option, where we can
stop thrombus propagation by trapping the ICA from the neck to clinoid ICA proximal
to the ophthalmic artery (after clinoid drilling), but once again, it may be associated
with ophthalmic artery spasm or very rarely in trauma. Now should we use trapping
in all such cases or in which cases should we use trapping other than only neck ligation
of ICA in the neck?
Conclusion
Mono-ocular blindness is a serious complication. It is very difficult to draw a conclusion
from a single case; we have to learn more about the mono-ocular blindness from ophthalmic/central
retinal artery thrombosis in EC-IC HFB with ICA ligation to prevent it.
