**2. Epidemiology**

TSC is a rare condition. It has a birth incidence of 1 per 5800 and an incidence of 1 per 30,000 in the general population [6]. From all cases between 1900 and 2018 that were published in the English literature, only 33 patients with 42 IA were found [11]. But the incidence of IA in TSC might be higher as reported, as no screening trial has been performed yet. Furthermore, according to the recommendations of the 2012 TSC Consensus Conference [12], the MRI at diagnosis and every 1–3 years until the age of 25 years does not involve a special sequence for the vascular system, so-called time-of-flight MR angiography (TOF-MRA). This circumstance increases the risk of overlooking small aneurysms.
