Aneurysms involving supra-aortic extracranial vessels have a number of serious risks such as rupture and local compression, but also a risk of brain embolization and stroke. Presenting symptoms may be different, including the presence of a palpable mass, supraclavicular pain, dysphagia, hoarseness, Horner's syndrome, transient ischemic attacks (TIA) or ischemic stroke 19
. The patient in our report developed slow-onset symptoms but increasing swallowing difficulties made her seek care where a simple oral inspection revealed the mass that was later revealed as the giant ICA aneurysm.
Aneurysms of the extracranial portion of the ICA are extremely rare, accounting only for 0.5% to 1.9% of all carotid surgical treatments 20
. As the presenting manifestation of NF-1 vasculopathy, ICA aneurysms are even rarer, predominantly affecting women in their fourth decade of life 21
Although most patients with NF1-associated vascular lesions are asymptomatic 9
, in cases of carotid artery aneurysms with symptoms like cerebral ischemia, mass effect or rupture, treatment is usually recommended. There are doubts, however, about the natural history of asymptomatic aneurysms as they are so uncommon, and therefore the indications for treatment are not clearly defined. While the diameter threshold to recommend treatment for adult asymptomatic aneurysms is proposed to be 2 cm, it is even more difficult to establish such threshold in pediatric patients because of the disease rarity 22,23
Early surgical treatment may be preferred in children considering the serious risks of cerebral ischemia or rupture and the lack of experience from stents and covered stent grafts in the pediatric population. Open surgery may be a treatment option also in adults 21
, but as the NF-1 related aneurysms discovered in adults often are of a significant size at the time of treatment, operative exposure is mostly considered challenging and risky. Reports on covered stent graft placement in the internal carotid artery in adults are few and reveal the risks of both thromboemboli and graft occlusion 24-26
requiring meticulous antithrombotic treatment 27
. Endovascular techniques may also include filling the aneurysm with coils, glue 21
or Onyx 28
but more recently, stenting techniques using flow diverters have been proposed for the treatment of giant and large aneurysms. Flow diverters appear to be a promising tool even though the risks and the outcomes of such treatment are still not well known 29
, especially in cases of a known underlying disease like NF-1. Finally, giant and large aneurysms of the internal carotid artery may be treated with parent vessel occlusion. Endovascular treatment by occlusion of the parent artery is a long-practiced, safe and effective treatment despite the obvious limitation and potential long-term complications of sacrificing the vessel 29
. In the face of an underlying vasculopathy affecting the vessel wall, it may also be preferable not to leave too much foreign material in the vasculature and especially not directly in the aneurysm, be it coils, liquid embolics or different types of advanced stent constructs. There have been reports in the literature that NF-1 affected arteries are indeed more fragile with dissections and vessel wall degeneration in the elastic lamina and the media 2,30
After passing a balloon occlusion test, our patient was treated with parent artery occlusion, trapping the aneurysm with two detachable balloons, positioned distal and proximal to the aneurysm. To secure the construct, coils were placed below the proximal balloon. The procedure was performed under flow-reversal achieved by an 8 French balloon guide catheter to avoid escape of small thromboemboli as well as of the detachable balloons. Before embarking on this treatment, other options were discussed but ruled out: open surgery because of the need for a very high exposure, different stent techniques mainly for anatomical-technical reasons. Finally coils or liquid embolics to fill the sac were excluded because of the risk for augmentation of the compression symptoms and because of the huge aneurysm size necessitating large amounts of foreign material in a diseased segment of the vasculature that harbored unpredictable vessel wall alterations.
Therapeutic carotid artery occlusion is a simple, safe, and effective treatment for large and giant carotid artery aneurysms in patients who can tolerate sacrifice of the vessel 31-33
, which can be reliably tested by angiographic balloon test occlusion. The aim of therapeutic carotid artery occlusion is thrombosis of the internal carotid artery, including the aneurysm. In a clinical study De Gast et al. 34
evaluated aneurysm size and clinical symptoms midterm after therapeutic carotid artery occlusion in 39 patients with large or giant intracranial carotid artery aneurysms. Most aneurysms involuted totally or decreased substantially in size over time, particularly in the first year after carotid artery occlusion. Thrombosis of the aneurysm was assessed by typical signal changes in the aneurysmal lumen on MR scans over time, including loss of flow void and the appearance of T1-weighted hyperintensities.
Negative effects of parent vessel sacrifice include the increased risk for hemodynamic impairment in patients with a single carotid artery 29
as well as the risk for formation of flow-related de novo
aneurysms in other, mainly contra-lateral arteries that now have to harbor an increased flow 35,36
In our patient, the aneurysm gradually involuted and decreased in size as demonstrated on an MR performed 20 months after treatment where the size was approximately half of the original. Repeated esophagographies revealed normalized swallowing and clinically after 2.5 years she reports to be almost completely asymptomatic. Still, she is scheduled for another MR scan to be performed five years after treatment. In addition to controlling the treated aneurysm, the investigation will include MR angiography and MR perfusion to look for de novo aneurysms and signs of hemodynamic impairment. The need for life-long periodic assessments in NF-1 patients with vascular manifestations has been debated 2,30
. The rarity of such vascular involvement in this particular disease has been argued to speak against long-term follow-up whereas the potential catastrophic consequences of a rupture or a major ischemic infarct to speak in favor of following the patients possibly for life. The problem of inactive neurofibromin is, however, also related to tumor formation, which is equally well-demonstrated by mutations in another gene, RASA1
, (p120-RASGAP) 37
. Such mutations increase the risk for a variety of fast-flow vascular anomalies as well as for tumor development 38
. Even if the vascular malformations in such patients with mutations in RF1
may potentially be treated and cured, it has been argued that the patients still need long-term follow-up to disclose any potential appearance of tumors. We have together with the patient agreed on clinical and MR follow-ups at least five and ten years after treatment.
In conclusion, giant cervical internal carotid aneurysms associated with NF-1 can be safely treated with parent artery occlusion leading to an excellent result both radiologically and clinically.