Introduction Spinal dural arteriovenous fistulas (dAVF) are the most common vascular malformations of the spinal cord. The arterialization of the recipient radicular vein results in venous hypertension and cord edema. Without treatment, symptoms may progress to myelopathy, sensory deficits, paraplegia, bowel and urinary incontinence, and potentially venous infarction of the cord. Successful treatment of these lesions can halt symptom progression and result in significant functional recovery in many patients. To achieve obliteration of a spinal dAVF, the shunt site has to be targeted either by microsurgical clipping or by superselective embolization via an endovascular approach. The introduction of indocyanine green (ICG) into the operating room for use by surgeons performing a variety of neurovascular procedures holds promise as a useful adjunct. Employing this method, the operating field is illuminated by near infrared excitation light and ICG is injected intravenously. The intravenous fluorescence is imaged instantly with a video camera integrated into the microscope allowing differentiation between arterial, capillary and venous phases. ICG angiography provides a minimally invasive, quick, safe and reliable method of imaging the vasculature within the operative field.

Methods We performed a prospective observational study of patients with spinal dAVF that were treated by microsurgical obliteration to determine if ICG angiography: (1) provided supplemental flow related data that changed the surgical plan as it has been found useful for other neurovascular procedures; and (2) if the fidelity and resolution afforded by ICG angiography intraoperatively may substitute for a conventional postoperative selective spinal angiogram.

Results Four patients over a 6 month period were identified who were treated surgically with intraoperative confirmation with intravenous use of ICG. In all four cases, intraoperative radiographic identification of the level of the lesion, as determined by angiography, was achieved and led to a laminectomy and durotomy being performed at the correct site. In all cases, direct visual identification of the fistulous connection in close proximity to the exiting nerve root was readily obtained on intradural inspection. Initial ICG angiography confirmed the fistula but in none of the cases did it change the surgical plan. Following treatment of the lesion, ICG angiography was repeated. Confirmation of the eradication of the fistula was obtained in all cases with normal dye transit into pial veins. There was no residual filling of the fistulous vein in any of the cases and the findings from ICG angiography did not change the ultimate surgical management. In all four cases, conventional postoperative angiogram confirmed complete treatment of the dAVF. All patients demonstrated subjective and objective improvements in their lower extremity motor and sensory function.

Conclusions ICG angiography in the setting of surgical management of spinal dural fistula is a simple and effective technique for intraoperative confirmation of the relevant lesion. Additionally, post-resection ICG angiography reliably demonstrated technical success and may replace formal postoperative catheter angiography. Although not needed in our cases, the surgical plan may be modified based on ICG angiography should the lesion be more complex.