Benchtop and in Vitro Experiments of Novel Transform Stents for Trigeminal Neuralgia Treatment

BACKGROUND

Trigeminal neuralgia (TN) is a debilitating condition characterized by sudden, excruciating facial pain due to neurovascular compression of the trigeminal nerve. Stent deployment can change the course of the superior cerebellar artery upwards, possibly releasing the root entry zone of the trigeminal nerve. We developed a novel stent, the Transform stent, for TN treatment, and evaluated its mechanical properties using benchtop and in vitro hemocompatibility tests.

METHODS

We compared the performance of Transform and Enterprise stents in treating TN because they share similar self-expanding closed-cell features in the manufacturing process, are derived from nitinol tubes, and are fabricated through a laser-cutting process, but also because only the safety of Enterprise stents deployed in intracranial arteries has been reported clinically. All benchtop measurements, including radial force, trackability, bending stiffness, and conformability, were performed thrice for each stent model, and their average values are presented.

RESULTS

Transform stents showed higher radial forces in vessels of diameters ranging from 1.0 mm than Enterprise stents. The trackability of the Transform stent was better than that of the Enterprise stent in a neurovascular model. Bending stiffness was stronger in the Transform stent whereas conformability was superior in the Enterprise stent. No significant thrombogenic issues were observed in the in vitro hemocompatibility tests.

CONCLUSIONS

This study demonstrated the Transform stent as a potential option and paved the way for innovative endovascular approaches for the future TN treatment. Namely, the study confirmed that the characteristics of Transform stents at benchtop and in vitro evaluations may be used as a first step for studies such as in vivo pre- and clinical studies.

Evaluating Changes in Pulsatile Flow With Endovascular Stents in an In Vitro Blood Vessel Model: Potential Implications for the Future Management of Neurovascular Compression Syndromes

BACKGROUND

Neurovascular compression syndromes (NVCS), encompassing conditions such as trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia, significantly impair patient quality of life through abnormal vascular compression and micro-pulsation of vasculature on cranial nerves at the Obersteiner-Redlich zone. The modulation of pulsatile flow dynamics via endovascular stents presents a novel research frontier for alleviating these syndromes.

AIM

The primary aim of this investigation was to delineate the impact of various endovascular stents on pulsatile flow within an in vitro model of a blood vessel, thereby elucidating their potential applicability in the therapeutic management of NVCS.

MATERIALS AND METHODS

A simple in vitro analog of a posterior circulation artery was developed, employing an intravenous pump to replicate cardiac-induced blood flow. Within this model, alterations in pulsatile flow were quantitatively assessed following the introduction of three categorically distinct endovascular stents, varying in size. This assessment was facilitated through the employment of both micro-Doppler and Doppler ultrasound methodologies.

RESULTS

The Pipeline 5x35 mm stent (Medtronic, Minneapolis, MN) demonstrated the most significant reductions in peak systolic velocity (Vmax) and pulsatility index (PI), PI especially over the stent, suggesting its potential for drastically altering blood flow dynamics. Similarly, Neuroform Atlas 4.5x30 mm and Neuroform Atlas 4x24 mm stents (Stryker, Kalamazoo, MI) also showed notable decreases in hemodynamic parameters, albeit to different extents. Statistical analysis confirmed that these changes were significantly different from the control (P < 0.0001 for PI and Vmax; P < 0.05 for inter-stent comparisons), except for proximal PI means, which did not significantly differ from the control (P = 0.2777).

CONCLUSION

These findings affirm the potential of endovascular stents to substantially modulate arterial pulsatility. The observed decrease in pulsatile flow resultant from endovascular stent application has the potential to attenuate ectopic nerve excitation, a hallmark of NVCS. Consequently, this research highlights the prospective utility of endovascular stents in developing minimally invasive therapeutic approaches for NVCS.

Hemifacial spasm due to vertebral artery dissecting aneurysm treated with stent-in-stent placement; Pre- and post-treatment evaluation by 3D multifusion imaging using silent MR angiography

Background:

Hemifacial spasm (HFS) due to vertebral artery (VA) dissecting aneurysm (VADA) is rare and endovascular treatment has been performed in selected cases.

Case Description:

We encountered a case of HFS caused by VADA that was managed with endovascular stent placement and additional stent-in-stent placement. Therapeutic strategies and benefits based on pre- and post-treatment evaluation by 3D multifusion imaging using silent MRA were discussed.

Conclusion:

This is the first case report of stent-in-stent placement in successful treatment of HFS caused by VADA, in which relief of neurovascular contact was demonstrated by multifusion imaging.

Computational hemodynamic analysis of the offending vertebral artery at the site of neurovascular contact in a case of hemifacial spasm associated with subclavian steal syndrome: illustrative case

BACKGROUND

Hemifacial spasm (HFS) is caused by neurovascular contact along the facial nerve’s root exit zone (REZ). The authors report a rare HFS case that was associated with ipsilateral subclavian steal syndrome (SSS).

OBSERVATIONS

A 42-year-old man with right-sided aortic arch presented with progressing left HFS, which was associated with ipsilateral SSS due to severe stenosis of the left brachiocephalic trunk. Magnetic resonance imaging showed contact between the left REZ and vertebral artery (VA), which had shifted to the left. The authors speculated that the severe stenosis at the left brachiocephalic trunk resulted in the left VA’s deviation, which was the underlying cause of the HFS. The authors performed percutaneous angioplasty (PTA) to dilate the left brachiocephalic trunk. Ischemic symptoms of the left arm improved after PTA, but the HFS remained unchanged. A computational fluid dynamics study showed that the high wall shear stress (WSS) around the site of neurovascular contact decreased after PTA. In contrast, pressure at the point of neurovascular contact increased after PTA.

LESSONS

SSS is rarely associated with HFS. Endovascular treatment for SSS reduced WSS of the neurovascular contact but increased theoretical pressure of the neurovascular contact. Physical release of the neurovascular contact is the best treatment option for HFS.

Improvement of Hemifacial Spasm after Stent-assisted Coil Embolization for Ipsilateral Vertebral Artery Dissecting Aneurysm

Microvascular decompression (MVD) is the gold standard in the treatment of hemifacial spasm (HFS), and endovascular surgery has been described as a treatment only for aneurysm-induced HFS in several previous cases. We describe symptomatic HFS caused by a normal vertebral artery (VA) trunk adjacent to the ipsilateral dissecting VA aneurysm completely cured after stent-assisted coil embolization. A 52-year-old man presented with a 2-month history of gradually worsening left HFS. Magnetic resonance imaging (MRI) and cerebral angiography revealed a dissecting VA aneurysm on the left side. Based on the findings from preoperative MRI, not the aneurysmal dome itself, but the VA trunk just distal to the aneurysmal dome was considered likely to be compressing the root exit zone (REZ) of the facial nerve. Stent-assisted coil embolization was conducted for the VA aneurysm, and the stent was deployed to cover the wide neck of the aneurysm and offending zone of the VA trunk simultaneously. HFS started to show improvement just after the procedure and complete disappearance within 1 year. HFS was completely resolved by stenting of the offending artery. Stents may show efficacy for "intra-arterial decompression" by reducing pulsatility against the REZ of the facial nerve due to the thickness and rigidity of the stent metal and delayed endothelialization.

Treatment for Hemifacial Spasm Associated with a Dissecting Vertebral Artery Aneurysm Requiring Microvascular Decompression in Addition to Endovascular Trapping: A Case Report with Literature Review

BACKGROUND

 The treatment protocol for hemifacial spasm (HFS) associated with dissecting vertebral artery aneurysm (DVAA) has not been established.

CASE DESCRIPTION

 A-42-year-old man with left HFS underwent endovascular trapping for a DVAA that was identified on brain imaging. Although the dissecting segment was treated successfully, the HFS persisted for 3 months, and subsequently microvascular decompression (MVD) was needed. The posteroinferior cerebellar artery (PICA) was found to be interposed between the root exit zone of the facial nerve and DVAA during surgery. After pulling out the PICA, the HFS ceased immediately.

CONCLUSION

 HFS associated with DVAA should be considered carefully before formulating a treatment strategy. Moreover, the cause of pulsatile compression may not be visible on brain imaging, and MVD surgery may be indicated in such cases.

Hemifacial spasm caused by vertebral artery aneurysm treated by endovascular coil embolization

BACKGROUND

Hemifacial spasm (HFS) caused by vertebral artery (VA) aneurysms is rare. Several cases of HFS caused by VA aneurysms treated by endovascular parent artery occlusion (PAO) have been reported. Recently, we treated a rare case of HFS caused by a saccular VA aneurysm at the bifurcation of the posterior inferior cerebellar artery (PICA), which was successfully treated by endovascular coil embolization, preserving the parent artery, and PICA. We discuss endovascular treatment for HFS induced by VA aneurysms with a literature review.

CASE DESCRIPTION

A 59-year-old man presented with the left HFS persisting for 2 months. Magnetic resonance imaging revealed a left saccular VA-PICA aneurysm and demonstrated that a left facial nerve was compressed by the aneurysm at the root exit zone. Angiography revealed that the PICA was branching from the aneurysm neck. Endovascular coil embolization was performed using the balloon remodeling technique to preserve the left VA and PICA. HFS disappeared after treatment.

CONCLUSION

Although microvascular decompression was commonly accepted for the standard treatment of HFS, coil embolization of aneurysms without PAO may be an effective treatment for HFS caused by VA aneurysms.