Minimally invasive superficial temporal artery to middle cerebral artery bypass through a bur hole

STA-MCA bypasses are established EC-IC bypasses for low to moderate flow cerebral revascularization. A STA-MCA, low-flow, EC-IC bypass traditionally requires a large frontotemporal craniotomy to expose the distal Sylvian fissure for the anastomotic site. We describe a less-invasive procedure using a single 2- to 2.5-cm enlarged bur hole, in place of the standard craniotomy, through which the recipient and donor vessels were identified and the anastomosis performed.¹

This procedure was performed for multiple patients with recurrent cerebrovascular ischemic episodes. One patient was awake for the procedure, with local anesthesia and propofol sedation, due to his multivessel occlusive disease and compromised vascular reserve, in an effort to avoid general anesthesia-related hypotension. With the aid of a stereotactic neuronavigation system, we minimized the size of the skin incision and the craniotomy such that the procedure could be performed effectively via an enlarged bur hole or small craniotomy (2- to 2.5-cm diameter). A CT angiogram was used preoperatively to select the donor vessel, recipient vessel, and anastomosis site. The STA was visualized, along with its frontal and parietal branches. The diameters of the branches were measured in order to identify the optimal donor vessel (Figure 15–1A). A linear skin incision was then made overlying the donor vessel. Bur hole/craniotomy placement can be planned preoperatively using a stereotactically reconstructed model based on the CT angiogram (Figure 15–1B). The recipient vessel is chosen according to its caliber and superficial location in the Sylvian fissure. The optimal recipient vessel is identified on review of the CT angiogram (Figure 15–1C). The exact location of the bur hole/craniotomy is then planned using CT angiography–based neuronavigation, and overlies the selected recipient vessel in immediate proximity to the chosen donor vessel.

Figure 15–1 A, Image guidance workstation view of three-dimensional reconstruction of CT angiogram showing the donor vessel, parietal branch of STA (arrow). B, Image guidance workstation axial, coronal, and saggital and three-dimensional reconstruction CT angiogram views showing the preselected bur hole/craniotomy site (red dots). The overlying donor (arrow) and recipient vessels are seen on both sides of the bur hole location. C, Image guidance workstation axial, coronal, and saggital and three-dimensional reconstruction CT angiogram views showing the MCA recipient vessel in the sylvian fissure (arrow).

The incision is performed under the microscope where the temporalis muscle is split vertically directly below the selected donor branch of the STA. A bur hole is made and enlarged to the size of a small craniotomy (∼2 to 2.5 cm) under the microscope, and then 1 cm of the recipient vessel is exposed in the Sylvian fissure (Figures 15–2 and 15–3). A rubber dam is applied and the anastomosis is performed with a 9-0 nylon suture in a running fashion. The back wall is anastomosed before the front wall. Temporary clips are applied on the recipient vessel, the M4 branch of the MCA, during the anastomosis. Postoperatively, the patients were followed up with angiography or CT angiography, and clinically, disease progression was halted (Figures 15-4 through 15-7).

Figure 15–2 Intraoperative photograph obtained through the microscope while the bur hole/craniotomy was being performed.

(From Coppens JR, Cantando JD, Abdulrauf SI, Minimally invasive superficial temporal artery to middle cerebral artery bypass through an enlarged bur hole: the use of computed tomography angiography neuronavigation in surgical planning, J Neurosurg 2008;109(3):553–558, with permission.)

Figure 15–3 Intraoperative photograph obtained through the microscope demonstrating the maximum diameter of the bur hole/craniotomy to be ∼2 cm.

(From Coppens JR, Cantando JD, Abdulrauf SI, Minimally invasive superficial temporal artery to middle cerebral artery bypass through an enlarged bur hole: the use of computed tomography angiography neuronavigation in surgical planning, J Neurosurg 2008;109(3):553-558, with permission.)

Figure 15–4 AP (A) and lateral (B) views of the postoperative cerebral angiogram demonstrating the bypass in the form of a STA-MCA (M4 branch) anastomosis.

(From Coppens JR, Cantando JD, Abdulrauf SI, Minimally invasive superficial temporal artery to middle cerebral artery bypass through an enlarged bur hole: the use of computed tomography angiography neuronavigation in surgical planning, J Neurosurg 2008;109(3):553-558, with permission.)

Figure 15–5 A and B Sequential coronal CT angiographies showing the STA-MCA bypass entering through a bur hole (<2.5 cm in size). Arrow 1 shows the STA, arrow 2 points toward the bur hole opening, and arrow 3 indicates the recipient MCA vessel.

Figure 15–6 A three-dimensional reconstruction of the postoperative CT angiogram demonstrating maturation of the EC-IC bypass.

(From Coppens JR, Cantando JD, Abdulrauf SI, Minimally invasive superficial temporal artery to middle cerebral artery bypass through an enlarged bur hole: the use of computed tomography angiography neuronavigation in surgical planning, J Neurosurg 2008;109(3):553-558, with permission.)

Figure 15–7 CT angiography three-dimensional reconstruction of the STA-MCA bypass using a minimally invasive technique. (Note the right carotid artery occlusion with which the patient presented.)

We were able to successfully perform minimally invasive STA-MCA bypasses with 2- to 2.5-cm craniotomies through the use of preoperative CT angiography neuronavigation. With the use of stereotaxy we were able to limit the size of both the skin incision and the bur hole/craniotomy. We anticipate the widespread incorporation of CT angiography neuronavigation into future STA-MCA bypass procedures.

Since the publication of this minimally invasive procedure, Fischer et al.² have described a similar minimally invasive procedure with the use of 3D virtual planning with the Dextroscope and magnetic resonance angiography in place of intraoperative stereotaxy that could serve as an alternative to the technique described above.

Minimally invasive high-flow bypass technique: internal maxillary artery to middle cerebral artery ec-ic bypass

High-flow cerebral revascularization currently requires graft vessel harvesting, cervical incision for the proximal anastomosis, craniotomy for distal anastomosis, and parent vessel occlusion. This conventionally necessitates a large craniotomy and extensive cervical incision. Instead, we illustrate a technique that avoids a long cervical incision and allows for purely intracranial extradural access to the internal maxillary artery (IMAX) to perform a short segment high-flow anastomosis from it to the MCA, using a radial artery graft.³

In recent years a number of important variations have been introduced to make the high-flow EC-IC bypasses less invasive. The contributions of C. A. F. Tulleken in devising the non-occlusive, laser-assisted anastomosis have to be commended (see Chapter 14). A case report was published using the Cardica C-Port xA Distal Anastomosis System for an automated high-flow bypass. This involves an automated end-to-side anastomosis with simultaneous arteriotomy and insertion of 13 microclips into the graft and recipient vessels. This latter technique however, is very limiting because of the size and configuration of the device and is unlikely to be used widely due to this important limitation.⁴

In this section we describe our development of the IMAX-MCA bypass technique, which we believe is much less invasive than the standard high-flow EC-IC bypass. Prior to clinical application of our bypass, we performed a series of six adult cadaveric dissections. The IMAX was dissected via a middle fossa extradural approach in the cadaveric specimens in order to confirm the middle fossa surface landmarks, location, and depth of the artery (Figure 15–8). This methodology was subsequently implemented in a clinical case as outlined below.

Figure 15–8 A, Cadaveric dissection showing the relationship between IMAX (red arrow) and V2 (blue arrow), via an extradural, right-sided, middle fossa approach. B, Cadaveric dissection showing the distal portion of the IMAX 6 mm lateral to V2.

We drew a straight line extending anteriorly from the V2/V3 apex along the inferior edge of V2. The distance from the V2/V3 apex to the lateral rotundum was 7.8 mm ± 3.033 mm. The distance from the lateral edge of the foramen rotundum to the medial extent of the IMAX was 8.6 mm ± 2.074 mm anteriorly. We then drilled to a depth of 4.2 mm ± 1.304 mm into the greater wing of the sphenoid bone, ultimately exposing an average of 7.8 mm ± 1.643 mm of the maxillary artery (Table 15–1). The IMAX was consistently found running just anterior and parallel to a line between the foramina rotundum and ovale.

The high-flow bypass was conducted via an extradural middle fossa approach for a patient with bilateral transitional (cavernous and clinoidal) internal carotid artery (ICA) aneurysms (Figures 15–9 and 15–10). Prior to the procedure, balloon test occlusion (BTO) was performed in order to assess the quality of the collateral vasculature (Figure 15–11). This showed that the collateral system was insufficient to support cerebral perfusion without an EC-IC bypass. Intraoperatively, the anterolateral triangle between V2 and V3 was identified. Using the aforementioned measurements taken in the laboratory, the anterior loop of the IMAX was found just anterior and parallel to a line running between the foramen rotundum and the foramen ovale. The greater wing of the sphenoid bone was drilled at this location and the anterior loop of the internal maxillary artery was identified.

Figure 15–9 Lateral DSA of the common carotid artery of a patient with a giant aneurysm showing the proximity of the IMAX (arrow) to the internal carotid artery (ICA) and middle cerebral artery (MCA) for potential interposition grafting.

Figure 15–10 DSA three-dimensional reconstruction of a complex transitional segment ICA aneurysm, AP (A) and lateral (B) views.

Figure 15–11 Lateral DSA of the common carotid artery during balloon test occlusion (BTO) showing the internal maxillary artery (arrow).

Simultaneous radial artery harvest was undertaken. Temporary clips were placed on the IMAX (Figure 15–12). An end-to-side anastomosis of the radial artery graft to the IMAX was performed (Figure 15–13), followed by an end-to-side anastomosis to the recipient M2 branch within the Sylvian fissure (Figure 15–14). Intraoperative ICG angiography confirmed a patent graft (Figure 15–15). The ICA was occluded both proximally and just distal to the aneurysm in the supraclinoidal segment with aneurysm clips. The proximal clipping of the ICA, in this particular case, required a very small high cervical incision (2 cm) to avoid clipping the ICA within the cavernous segment, which we hope to avoid in future cases.

Figure 15–12 Right-sided intraoperative view of the middle fossa extradural approach showing temporary clips on anterior loop of the IMAX (yellow arrow), adjacent to V2 (blue arrow).

Figure 15–13 Proximal anastomosis of the radial artery graft to the IMAX in the middle fossa extradural space (intraoperative view).

Figure 15–14 A and B, Radial artery interposition graft between the IMAX and the M2 segment of the MCA.

Figure 15–15 Intraoperative ICG angiogram showing patency of the radial artery graft.

Postoperatively, the patient did well, without any new neurological deficits, and underwent formal angiography ensuring graft patency (Figures 15–16 and 15–17). The patient was discharged home on postoperative day 5; at the 3-week follow-up visit she had resumed normal activity without any restrictions.

Figure 15–16 Right common carotid artery (CCA) DSA postoperative angiography showing IMAX-MCA bypass using a radial artery graft in AP (A), oblique (B), and lateral (C) views.

Figure 15–17 Three-dimensional DSA reconstruction of right common carotid artery (CCA) angiography showing a radial artery interposition graft coursing from the floor of the middle fossa to the MCA in AP (A), oblique (B), and lateral (C) views.

We successfully used a short segment of the radial artery to connect the IMAX with the MCA in order to circumvent the diseased internal carotid artery in a patient with bilateral giant aneurysms. With use of the IMAX as the donor vessel, we were able to minimize the transverse cervical incision traditionally used to expose the CCA, ICA, and MCA. We anticipate obviating the need for cervical incisions all together in the future.

We believe minimally invasive endeavors and technology will play key roles in the future of EC-IC bypass and cerebral revascularization, in regards to both low- and high-flow procedures.