Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited small vessel disease characterised by recurrent ischemic stroke, cognitive decline progressing to dementia, psychiatric disturbances and apathy. More than half of mutation carriers suffer from migraine, most often migraine with aura. Recently, a CADASIL patient was treated with a monoclonal antibody targeting the calcitonin gene-related peptide (CGRP) receptor. Monoclonal antibodies targeting the CGRP system have been demonstrated to be safe, well tolerated, and effective in reducing migraine attacks. There is, however, abundant evidence that CGRP is important in maintaining cardiovascular homeostasis under (patho)physiological conditions. CGRP may act as a vasodilatory safeguard during cerebral and cardiac ischemia and blockage of the system could, therefore, potentially worsen ischemic events. Therefore, we caution against treating patients with small vessel diseases, such as the monogenic disorder CADASIL, with these drugs until relevant safety data and long term follow up results are available. Alternative preventive migraine treatments in CADASIL may be acetazolamide, sodium valproate, lamotrigine, topiramate, verapamil, or flunarizine.