Magnetic resonance angiography image guidance for the microsurgical clipping of intracranial aneurysms: a report of two cases

Frameless neuronavigation based only on 3D digital subtraction angiography using surface-based facial registration

OBJECT

Cerebrovascular lesions can have complicated abnormal anatomy that is not completely characterized by CT or MR angiography. Although 3D rotational angiography provides superior spatial and temporal resolution, catheter angiograms are not easily registered to the patient, limiting the use of these images as a source for neuronavigation. However, 3D digital subtraction angiography (DSA) contains not only vascular anatomy but also facial surface anatomy data. The authors report a novel technique to register 3D DSA images by using only the surface anatomy contained within the data set without having to fuse the DSA image set to other imaging modalities or use fiducial markers.

METHODS

A cadaver model was first created to assess the accuracy of neuronavigation based on 3D DSA images registered by facial surface anatomy. A 3D DSA scan was obtained of a formalin-fixed cadaver head, with acquisitions of mask and contrast runs. The right common carotid artery was injected prior to the contrast run with a 45% contrast solution diluted with water-soluble red liquid latex. One week later, the head was registered to a neuronavigation system loaded with the 3D DSA images acquired earlier using facial surface anatomy. A right pterional craniotomy was performed and 10 different vascular landmarks were identified and measured for accuracy using the neuronavigation system. Neuronavigation based only on 3D DSA was then used to guide an open clipping procedure for a patient who presented with a ruptured distal lenticulostriate aneurysm.

RESULTS

The accuracy of the measurements for the cadaver model was 0.71 ± 0.25 mm (mean ± SE), which is superior to the 1.8-5 mm reported for neuronavigation. The 3D DSA-based navigation-assisted surgery for the distal lenticulostriate aneurysm aided in localization, resulting in a small craniotomy and minimal brain dissection.

CONCLUSIONS

This is the first example of frameless neuronavigation based on 3D catheter angiography registered by only the surface anatomy data contained within the 3D DSA image set. This is an easily applied technique that is beneficial for accurately locating vascular pathological entities and reducing the dissection burden of vascular lesions.

Image-Guided Resection of Embolized Cerebral Arteriovenous Malformations Based on Catheter-Based Angiography

OBJECTIVE

We introduce a technique that enables the use of catheter angiography during image-guided surgery for the resection of previously embolized arteriovenous malformations.

METHODS

We used models to test the possibility of matching specific anatomic points 1:1 and the accuracy of merging catheter-based 3-dimensional angiography with standard computed tomographic angiography.

RESULTS

After obtaining excellent accuracy matching the 2 modalities, we merged both studies into the image-guidance platform. After embolizing a patient's arteriovenous malformation with Onyx, we successfully used the merged study to navigate during surgical resection of the lesion. No complications resulted from this technique, which increases contrast by only 15 cm3 and radiation exposure by 4 seconds.

CONCLUSION

Catheter-based angiography can be used during image guidance to reduce the artifact from metal particles after embolization. Excellent accuracy was obtained in merging 3-dimensional angiography with computed tomographic angiography. Further studies are needed to evaluate catheter-based 3-dimensional angiography as a single method for navigation during neurovascular surgery.

Management of distal anterior cerebral artery aneurysms: a single institution retrospective analysis (1997-2005)

OBJECTIVE

Our goal was to assess the clinical and angiographic outcomes among patients undergoing treatment for distal anterior cerebral artery aneurysms at the Jefferson Hospital for Neuroscience (1997-2005).

METHODS

Forty-one patients (1.5% of all aneurysms treated) with distal anterior cerebral artery aneurysms had undergone treatment. The clinical and angiographic outcomes of these patients were studied retrospectively using chart reviews, operative reports, and angiographic reports. The mean clinical and angiographic follow-up periods were 16 months (range, 3-74 mo) and 16.5 months (range, 6-81 mo), respectively.

RESULTS

Twenty-eight (68%) patients had undergone endovascular embolization (22 women, six men; mean age, 58.2 yr), whereas 13 (32%) had undergone microsurgery for clip ligation (six men, seven women; mean age, 47.4 yr). Within the coiled group, 50% of the patients belonged in the Hunt and Hess (HH) III and IV groups, whereas 46.2% of the patients in the clipped group were elective patients (HH Grade 0). The mean aneurysmal sizes among the clipped and coiled groups were 4.9 and 5.5 mm, respectively. Among the clipped patient population, 100% of the patients had successful clip ligation as evidenced by intraoperative cerebral angiography, there was a 0% recurrence rate among the two patients who have had long-term follow-up, 0% recurrent subarachnoid hemorrhage, and 92% patients achieved a modified Glasgow Outcome Scale score of I to II. Among the coiled patient population, there was an 89% rate of successful embolization, 18% recurrence rate, 0% recurrent subarachnoid hemorrhage, and 64% achieved a modified Glasgow Outcome Scale score of I to II. None of the patients had clinically symptomatic vasospasm. A strong correlation existed between having a ventriculostomy and requiring a shunt in patients with HH Grade IV compared with patients in HH Grades I through III.

CONCLUSION

In our analysis, clinical outcomes were better in the clipped group; however, the differences are not statistically significant (P = 0.3675) and are explained by the selection bias. Statistically significant predictors of outcomes were age (<60 yr), size of the aneurysm (>5 mm), absence of ventriculostomy, and presenting HH grade.