Neuronavigated microvascular Doppler sonography for intraoperative monitoring of blood flow velocity changes during aneurysm surgery - a feasible monitoring technique

The Use of Intraoperative Microvascular Doppler in Vascular Neurosurgery: Rationale and Results-A Systematic Review

Surgical treatment of neurovascular lesions like intracranial aneurysms, arteriovenous malformations and arteriovenous dural fistulas is still associated with high morbidity. Several recent studies are providing increasing insights into reliable tools to improve surgery and reduce complications. Inadvertent vessel compromise and incomplete occlusion of the lesion represent the most possible complications in neurovascular surgery. It is clear that direct visual examination alone does not allow to identify all instances of vessel compromise. Various modalities, including angiography, microvascular Doppler and neurophysiological studies, have been utilized for hemodynamics of flow vessels in proper clipping of the aneurysm or complete obliteration of the lesion. We intended to review the current knowledge about the intraoperative microvascular Doppler (iMDS) employment in the most updated literature, and explore the most recent implications not only in intracranial aneurysms but also in neurovascular lesions like arteriovenous malformations (AVMs) and arteriovenous dural fistulas (AVDFs). According to the PRISMA guidelines, systematic research in the most updated platform was performed in order to provide a complete overview about iMDS employment in neurovascular surgery. Twelve articles were included in the present paper and analyzed according to specific research areas. iMDS employment could represent a crucial tool to improve surgery in neurovascular lesions. The safety and effectiveness of the surgical treatment of neurovascular lesions like intracranial aneurysm and other neurovascular lesions like AVMs and AVDFs requires careful and accurate consideration regarding the assessment of anatomy and blood flow. Prognosis may depend on suboptimal or incomplete exclusion of the lesion.

Enhance Safety in Aneurysm Surgery: Strategies for Prevention of Intraoperative Vascular Complications

Complications during surgery for intracranial aneurysms can be devastating. Notorious pitfalls include premature rupture, parent vessel occlusion, local cerebral injury and brain contusion, and incomplete neck obliteration. These unfavorable intraoperative events can result in major neurological deficits with permanent morbidity and even mortality. Herein, the author highlights the relevant surgical strategies used in his daily practice of aneurysm surgery (e.g., aneurysm clipping with adenosine-induced temporary cardiac arrest), application of which may help prevent vascular complications and enhance surgical safety through reduction of the associated risks, thus allowing improvement of postoperative outcomes. Overall, all described methods and techniques should be considered as small pieces in the complex puzzle of prevention of vascular complications during aneurysm surgery.

Cotton-Assisted Surgical Clipping of Very Small Aneurysms: A Two-Center Study

OBJECTIVE

Very small intracranial aneurysms (VSIAs) are challenging to treat because aneurysm tearing and clip slippage can occur during neurosurgical clipping. In this study, we introduce and share our experience with cotton-assisted clipping of VSIAs.

METHODS

We retrospectively analyzed the data of 20 patients with 24 VSIAs treated with cotton-assisted clipping between February 2008 and December 2014 in the Neurosurgery Departments of the First Affiliated Hospital, Soochow University and Taizhou People's Hospital. During surgery, 2 aneurysm necks were torn. To treat the tears, we wrapped rectangular cotton pads around the parental arteries at the site of rupture. The remaining 22 aneurysms were clipped after being wrapped in cotton pads.

RESULTS

The 2 aneurysm ruptures were successfully repaired with cotton-assisted clipping. In the remaining 22 aneurysms, no cases of aneurysm clip slippage or aneurysm rupture occurred. Patients were followed up on average for 59.0 months (range, 30-113 months). Of the 20 patients, the 16 patients with preoperative Hunt-Hess grades of 1-3 recovered well after the surgery (Glasgow Outcome Scale [GOS] score, 5). Of the 4 patients with Hunt-Hess grades of 4-5, 3 had a good recovery (GOS scores, 4-5), and 1 patient died of heart disease 6 months after being discharged from the hospital; this patient had a GOS score of 4 at the time of discharge.

CONCLUSIONS

Cotton-assisted clipping could prevent aneurysm clip slipping and aneurysm rupture and facilitate the repair of aneurysm neck tears. This technique is a useful alternative therapy for VSIAs.

Intravenous 3-Dimensional Digital Subtraction Angiography During Surgical Treatment of Intracranial Aneurysm

BACKGROUND

Although intraarterial 3-dimensional digital subtraction angiography (ia-3DDSA) using an angiographic C-arm system is still the gold standard for postoperative confirmation of surgical clipping of intracranial aneurysms, ia-3DDSA requires catheterization and intraarterial injection of contrast medium, which adds risks to the surgical procedure and takes time. We propose a less invasive acquisition of 3D digital subtraction angiography with intravenous injection (iv-3DDSA) in the hybrid operating room to confirm the results of surgical clipping immediately after surgery.

CASE DESCRIPTION

A 56-year-old woman was diagnosed with an incidental wide-necked aneurysm located at the distal anterior cerebral artery. We performed surgical clipping. During the surgery, indocyanine green video angiography and Doppler ultrasonography were used for confirmation, and after the surgery iv-3DDSA and ia-3DDSA were performed with the angiography C-arm system in the hybrid operating room while the patient was still under anesthesia. We could confirm that there was no neck remnant left and that the parent vessels were patent on both iv-3DDSA and ia-3DDSA images. The image quality of iv-3DDSA was sufficient for all treatment evaluations and offered the additional benefits of visualizing the whole angioarchitecture including the contralateral side, being less invasive, and requiring only a few minutes until the availability of images.

CONCLUSIONS

Iv-3DDSA can be useful for postsurgical confirmation of clipping of aneurysms in the hybrid operating room.

Real-Time Ultrasound Doppler Enhances Precision in Image-Guided Approaches to the Cerebellopontine Angle

OBJECTIVE

To evaluate efficacy and reliability of intraoperative Doppler sonography in localizing the transverse and sigmoid sinuses during lateral suboccipital craniotomy.

METHODS

A 16-Mhz intraoperative micro-Doppler ultrasound (16Mhz, Multi-Dop pro, Compumedics, Singen, Germany) was applied to detect the medial border of the sigmoid sinus and the inferior border of the transverse sinus in 25 patients. Micro-Doppler measurements were compared with magnetic resonance- and computed tomography-based image guidance (Kolibri, Brainlab, Munich, Germany). Visual detectability of the sinuses with the operating microscope was also documented.

RESULTS

Inadvertent incision of the transverse or sigmoid sinuses did not occur in any patient when the 2 localizing methods have been used in combination. The mean mismatch of image-guided system and micro-Doppler was 2.64 mm (range, 0-6 mm; standard deviation, 1.55 mm). With the microscope the transverse sinus was invisible in 7 patients, the sigmoid sinus was visually undetectable in 1 case. The micro-Doppler indicated blood flow outside the visible borders of the sinuses in 5 patients.

CONCLUSIONS

A combination of image-guidance and micro-Doppler enhances the accuracy in localizing the margins of the transverse and sigmoid sinuses using the retrosigmoid approach, thus preventing inadvertent injury. The method could potentially be applied during other craniotomies involving the exposure of a venous sinus.