Intraoperative digital subtraction angiography in neurovascular disorders

Intraoperative digital subtraction angiography is useful for assessing the results of complex neurovascular procedures. Fifty-five patients with A VMs, aneurysms (Berry and bacterial), carotid-cavernous fistulae, spontaneous intracranial haemorrhages and penetrating head injuries had intraoperative angiograms. Sixteen of these patients had findings on the angiogram which altered the surgical procedure. There were no angiographic complications. We found intraoperative digital subtraction angiography a valuable adjunct to several neurovascular procedures.


Introduction
In the past neurosurgeons have relied mainly on direct visualisation or postoperative angiography to assess the results of complex neurovascular procedures. Advances in equipment have made it easier and faster to perform intraoperative angiography. Intraoperative angiography facilitates the immediate assessment of neurovascular procedures and allows the surgeon to correct any technical defects.We report our experience with intraoperative angiography atWentworth Hospital.

Patients and methods
From April 1990 to December 1994 fiftyfive intraoperative angiograms were performed at Wentworth Hospital. Angiograms were done via a transfemoral approach. A sheath was introduced preoperatively and flushed with heparinised saline (2000U/1 000ml of normal saline at30ml!hr). The patient was then anaesthetised and placed in the required position for surgery. The theatre table had a radiolucent extension to facilitate screening of the aortic arch and neck vessels.The standard three-pin Mayfield-Kees head-holder was used as required. (Radiolucent carbon fibre headholders are available).
Angiography was performed with a mobile digital subtraction imaging system (Ziehm Exposeop CB7-D). This consisted of a C-arm, digital processing unit, dual video monitors and an image storage unit.
The appropriate carotid or vertebral artery was catheterised during or at the end ofthe procedure asrequired by the surgeon.
Contrast Iohexol (6-1 Oml) (Omnipaque, Nycomed) was injected by hand to delineate the relevant vascular anatomy. The images were reviewed immediately. If it was felt that the surgical procedure was in any way unsatisfactory or incomplete further surgery was performed under the same I ntraoperative cj igital subtraction angiography in neurovascular disorders frompage24 anaesthetic. The sheath was removed at the end of the procedure. Postoperatively the groin was monitored for the development of haem atom a and peripheral pulses checked.
Routine postoperative angiography was not performed.

Results
Fifty-five intraoperative angiograms have been performed at Wentworth Hospital. The surgical procedures performed are detailed in Table 1. There were no angiographic complications Although not strictly monitored the intraoperative angiogram added an additional forty-fiveto sixty minutes to the procedure (including the time required to place the femoral sheath preoperatively).
The four patients with spontaneous intracranial haemorrhage had intraoperative angiography,astheir clinicalcondition necessitated immediate transfer to theatre for evacuation of the haematoma, precluding preoperative angiography.
Intraoperative angiograms were used to 10calise pseudoaneurysms or arteriovenous fistulae in patients with traumatic haemorrhages following penetrating head injury. Patients with mycotic aneurysms had intraoperative angiograms to help localise the aneurysms. Intraoperative angiograms were used to monitor the successful surgical closure of carotid cavernous fistulae. Sixteen of these angiograms revealed findings which altered the surgical procedure (TableII) . Six of the patients with AVMs required further surgery to completely excise theA VM. Three of the aneurysms had to have clipsrepositioned, due to a residual neck in one case and occluded vesselsin two cases.One mycotic aneurysm had thrombosed at the time of surgery.In a second patient with multiple mycotic aneurysms an additional aneurysm was detected on the intraoperative angiogram. Two patients with spontaneous intracerebral haemorrhages were found to have middle cerebral artery aneurysms. This finding enabled immediate clipping. In one of our patients a clip which was 25 SA JOURNAL OF RADIOLOGY. September1996 compromising the lCA was repositioned immediately due to the intraoperative angiogram finding.

Discussion
In the past,most intraoperative angiography was performed by using fluoroscopy or rapid serial-ftlm angiography, following either direct puncture of the internal carotid or by retrograde catheterisation of the superiidal temporal artery. I Severalauthors have reported the use of a mobile digital subtraction imaging system. I ,2,3 The advantages of this system are immediate review of subtracted images,high contrast resolution and superior spatial resolution (although not as good asconventional film lo page 28