Complete occlusion of the left internal carotid artery in neurofibromatosis type 1. Congenital dysplasia or progressive occlusion?

Question: Neurofibromatosis type 1 (NF1) is caused by mutations of the NF1-gene (17q22.1) and is typically characterized by hyperpigmented patches of the skin (café-au-lait spots) and multiple tumors of the peripheral nervous system (neurofibromas). Vascular complications, also summarized as „vascular NF“, are less known manifestations of NF1. They most commonly present as hypertension secondary to renal artery stenosis. In addition, several case reports describe progressive cerebrovascular occlusions. Here, we present a young NF1 patient with complete obstruction of a carotid artery and discuss whether a progressive vascular occlusion or a congenital vascular dysplasia might be the underlying cause.

Method: We report on a 14 years old girl with a proven NF1 mutation and clear clinical features of NF1 such as café-au-lait spots, freckling as well as several aneurysmatic bone cysts and a tumorous lesion of the brain stem. MRI-controls of this lesion showed a dysplasia of the left internal carotid artery (ACI). The last MRI-control was suspicious of a complete occlusion of the ACI for the first time. For further clarification a MRI-angiography and a Doppler sonography were performed.

Result: MRI-angiography confirmed the complete occlusion of the left ACI. Compensatory enlargement of the right ACI suggested that cerebral perfusion was at least in part provided through this artery. Doppler sonography of the left external carotid artery revealed a flow profile characteristic of an organ-providing artery. Therefore, additional cerebral perfusion through the left external carotid artery could be presumed.

Conclusion: Slowly progressive occlusions of vessels – even carotid arteries – as part of a „vascular NF“ are a well described but still unclear phenomenon. Our imaging results are suggestive of a congenital dysplasia with compensatory formation of a collateral circulation. In that case the remaining lumen of the left ACI that was documented in earlier examinations might have been a misinterpretation since this question was not the focus of the examination.