Internal maxillary artery (IMax) – middle cerebral artery bypass in a patient with bilateral atherosclerotic carotid occlusion: A technical case report

Presentation

The Institutional Vascular Review Board approved this study. A 77-year-old man with a history of diabetes, hypertension, systemic atherosclerosis, and two acute myocardial infarctions sought medical attention due to repeated TIAs. The image workout showed almost total occlusion of the right internal carotid artery (ICA) with 75% occlusion of the left ICA and a minor stroke at the right MCA territory. Physical examination revealed a left hemiparesis of 3/5. The patient was classified as grade 2 of the modified Rankin scale (mRS). Medical treatment included antiplatelet drugs, control of glucose levels, blood pressure, and the use of statins. However, the patient continued with recurrent TIAs despite this treatment. Magnetic resonance imaging (MRI) with perfusion sequence showed an increase in the time to peak (TTP), mean transit time (MTT), and a decrease in the regional cerebral blood flow (rCBF) at the right ICA territory (Fig. 1A-D). A superficial temporal artery (STA) – MCA bypass was considered; however, this patient had a very small-caliber STA.

Fig. 1.

Imaging studies. (A-C) Preoperative time to peak (TTP), mean transit time (MTT), and regional cerebral blood volume (rCBV) perfusion MRI shows low perfusion in the right hemisphere. (D) MRI shows an area of a previous infarction in the right opercular area. (E-G) Postoperative TTP, MTT, and rCBV perfusion image without areas of hypoperfusion. (H) CT-angio shows the IMax-radial artery graft (RAG) end-to-end anastomosis (yellow arrow) and the end-to-side M2 anastomosis (white arrow). CT-angio, computed tomography angiography; IMax, internal maxillary artery

Surgical approach (see supplementary Video 1)

To identify the IMax, we used the technique described by Peto et al. [10], consisting of a pterional approach with interfascial dissection of the temporal muscle (TM) and zygomatic osteotomy; the TM was cut, leaving a muscle cuff in the superior temporal line for the reconstruction. Next, the muscle was mobilized to the gap created by the zygomatic osteotomy. Next, the superior head of the lateral pterygoid muscle was identified and, if necessary, transected to discover the IMax. Afterward, a retrograde dissection was made to expose the whole pterygoid segment of the artery.

A radial artery graft (RAG) was obtained from the left side (after a negative Allen test) in a length of 12 cm. Then, a frontotemporal craniotomy was completed, with the temporal extension flush with the floor of the middle fossa. The Sylvian fissure was opened widely to identify M1-M2 segments of the MCA; the superior trunk was dissected and was left ready for distal anastomosis. Next, proximal and distal temporary clips were placed at the dissected segment of the IMax. The artery was divided after the alveolar nerve crossed it and was mobilized for an end-to-end anastomosis with the RAG. The anastomosis was completed with an 8-0 suture, using a separated suture technique; after the proximal anastomosis finished, the calculated graft’s free flow was 216 ml/min. Then, the anastomosis with the superior trunk of M2 was completed with a 10-0 suture with an interrupted suture technique. The temporary clips were released, and the patency was corroborated with fluorescein video angiography and intraoperative Doppler. The dura mater was closed, leaving a dural opening for the RAG, and the rest of the surgical layers were closed and reconstructed as usual (Fig. 2).

Fig. 2.

Illustrative case. (A) Surgical planning for a pterional and transzygomatic approach. (B and C) Incision and dissection of the radial artery. (D) IMax to radial artery graft end-to-end anastomosis. (E) Radial artery to M2 end-to-side anastomosis. (F) Intraoperative fluorescein video angiography shows the IMax-M2 anastomosis with radial artery graft (white arrows) with adequate perfusion of the cerebral hemisphere. IMax, internal maxillary artery

Postoperative course

Postoperative computed tomography angiography (CT-Angio) showed patency of the bypass and adequate irrigation of the MCA territory. Diffusion-weighted imaging showed no areas of new ischemic events. Perfusion sequence showed a decrease in the TTP and MTT and an increase in the regional cerebral blood flow (rCBF) in the MCA territory, with hypoperfusion in the posterior cerebral artery (PCA) territory included the watershed area between MCA and PCA (Fig. 1E-H, Fig. 3). In addition, the patient’s hemiparesis improved to 4+/5. The patient was discharged one week after the operation with an mRS of 1 without additional motor deficit to continue rehabilitation in a physical therapy facility.

Fig. 3.

Sagittal view shows the IMax-radial artery graft (RAG) end-to-end anastomosis (yellow arrow) and the end-to-side M2 anastomosis (white arrow). IMax, internal maxillary artery

Treatment strategy

The patient, in this case, as previously mentioned, continued with neurologic symptoms regardless of BMT, and the perfusion studies showed the whole right MCA territory with hypoperfusion that worsened with his daily activities, meaning that the patient alternated between oligemia and ischemia. So then, it was decided to perform the bypass in agreement with the Institutional Vascular Review Board.

The IMax was selected as a donor’s vessel because of the small size of the STA and the need to revascularize the whole MCA territory, meaning that the blood supply needed to be higher than 15–40 ml/100g/min. According to previous reports, IMax provides between 60-95 ml/min/100g [23]. To localize the IMax artery, we selected the technique described by Peto et al. [10] because of the short time needed to expose the artery. The radial artery was selected as a graft because it has some advantages; 1) more appropriate diameter similar to the M2 segment of the MCA, avoiding a type- 2b error [14], 2) the lack of valves, 3) less possibility of kinking and 4), adequate length from the temporal fossa to the Sylvian fissure. In this case, the final length of the graft was 7 cm [14,17,18]. We decided to perform the bypass to the superior trunk of M2 to prioritize the flow to the precentral and central arteries, which were the ones that irrigated the motor and supplementary motor cortex.

Cut flow calculation

In addition, the cut flow was calculated before discharge using transcranial Doppler measurements. The calculated flow at the RAG was 334 ml/min, and the flow of the MCA was 288 ml/ml. According to Jonathan and Charbel [15], these values provide a cut flow index of 0.86, meaning that the bypass has an 83.1% long-term patency rate.

To our knowledge, this is the first case published using an IMax bypass to treat a complex systemic steno-occlusive disease with improved perfusion parameters (TTP, MTT, and rCBF). Although we are waiting for new results of clinical trials such as Carotid and Middle cerebral artery Occlusion Surgery Study (CMOSS) [7], this procedure has a physiologic and logical foundation, so it should not be discarded as an option for treatment.