Superficial temporal artery-to-middle cerebral artery bypass surgery for middle cerebral artery stenosis in a patient with cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy

History

A 54-year-old left-handed man was referred to our hospital with slight motor aphasia
and left finger numbness. His cognitive function and intelligence levels were normal.
Three years previously, he had been diagnosed with CADASIL by genetic testing for
mutation in the Notch 3 gene. At the time of initial diagnosis, he complained of sensory disturbances on
the right side of his body were caused by a lacunar infarction in the left thalamus.
There was no significant stenosis of the major cerebral arteries on MR angiography
at this time. During the interval between his initial diagnosis and the second infarction,
he was not administered any antithrombotic agents.

Examination

On clinical examinations, the patient was normotensive. A neurological examination
revealed dysphasia, dyslexia, and numbness of the left fingers. Multifocal acute subcortical
infarctions were found in the watershed area between the right MCA and the posterior
cerebral artery on diffusion-weighted imaging sequences (Fig. 1). MR angiography confirmed severe stenosis of the right MCA that had not been present
6 months prior (Fig. 2a, b). MR imaging (MRI) demonstrated typical increased T2-signal intensity indicating
white matter abnormalities in the left anterior temporal lobe, both anterior frontal
lobes, external capsules, and periventricular regions (Fig. 3a, b). Some cerebral microbleeds (CMBs) were also present in both the basal ganglia
and the subcortical areas. The patient was diagnosed with atherosclerotic infarction
and treated with anti-thrombotic therapy. His symptoms were relieved and he was discharged.
However, he presented with transient ischemic attacks (TIAs) characterized by left
hand motor weakness several times after discharge despite receiving oral antiplatelet
treatment. One month after the infarction, [
¹²³
I] N-isopropyl-p-iodoamphetamine single photon emission computed tomography (IMP-SPECT)
revealed a significant decrease in regional CBF (Fig. 4a) and CVR (Fig. 4b) under the acetazolamide challenge test occurring predominantly in the territory
of the right MCA. Therefore, a superficial temporal artery (STA)-MCA anastomosis was
planned to improve blood flow on the right side. Preoperative MRI revealed a newly
developed cerebral infarction in the right corona radiata (data not shown).

Fig. 1. MR imaging (diffusion weighted imaging sequences) revealed multifocal hyperintense
signal in a distribution pattern compatible with watershed infarcts in the right posterior
MCA territory

Fig. 2. MR angiography showed progression of atherosclerotic stenosis at the right MCA, 6 months
before the onset of stroke (a) and preoperatively (b)

Fig. 3. MR imaging (fluid-attenuated inversion recovery) demonstrated typical white matter
increased T2-signal intensity abnormalities in the anterior temporal lobe (a) and external capsules (b)

Fig. 4. Preoperative SPECT revealed the localized hypoperfusion in the right posterior MCA
territory (a), and decreased CVR was detected by ACZ challenge (b). Improvement of the CBF (c) and CVR (d) was identified on postoperative SPECT

Surgery

Under general anesthesia, the parietal and frontal branches of the STA were dissected
for use as donor arteries. After performing a fronto-temporal craniotomy and dural
incision, we exposed two normal-appearing recipient arteries. Intraoperative control
indocyanine green (ICG) videoangiography was performed before anastomosis to confirm
the patency of the recipient cortical arteries, and showed slow antegrade filling
due to atherosclerotic stenosis of the M1 and M2 segments. First, we selected the
angular branch of the M4 segment in the region showing a marked decrease in perfusion
as a recipient vessel. Anastomosis between the donor and recipient vessels was performed
in the usual manner. After ICG videoangiography revealed inadequate filling in the
territory of the MCA, an additional anastomosis was performed at the fronto-temporal
area of the MCA. The STAs were successfully anastomosed to the recipient vessels.
During and after surgery, hypotension and dehydration were avoided, and systolic blood
pressure was kept 120 mmHg. Aspirin was administered at a dose of 100 mg/day post
operatively.

Post-operative course

The post-operative course was uneventful. On post-operative day 1, an IMP-SPECT study
showed a 50 % increase in uptake in the right MCA territory but not hyperperfusion,
and MRI demonstrated the patency of the double anastomosis (data not shown). IMP-SPECT
images obtained 1 month after surgery showed improved regional CBF (Fig. 4c) and CVR (Fig. 4d) in the right hemisphere. No hemorrhagic complications occurred. After surgery,
the patient’s preoperative symptoms were relieved, and the TIAs disappeared. The patient
was discharged 12 days after surgery. Sixteen months have already passed since surgery,
and the patient is doing well. Cerebrovascular events such as TIA, infarction and
hemorrhage have not appeared. Follow up MRI 14 months after surgery showed no remarkable
area of increased intensity indicating white matter abnormalities in the left anterior
temporal lobe, both anterior frontal lobes, external capsules, or periventricular
regions on FLAIR images (Fig. 5a–c). MR angiography was used to confirm the patency of the bypass (Fig. 5d).

Fig. 5. Postoperative MRI shows no remarkable change on abnormal intensity in the anterior
temporal lobe (a), external capsules, periventricular regions (b), and white matter (c). MR angiography revealed the patency of the right STA-MCA double anastomoses (d)