CADASIL mimicking multiple sclerosis: The importance of clinical and MRI red flags.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited small vessel disease, manifesting as recurrent ischaemic events, migraine with aura, behavioural disturbance and cognitive decline. We report two patients with CADASIL masquerading as multiple sclerosis (MS). A 23year old female presented with a visual scotoma and was discovered to have a corresponding retinal cotton wool spot. MRI brain revealed diffuse T2 hyperintensities suggestive of demyelination. A 56year old male presented with transient sequential paraesthesia, initially of the perineum followed by the right leg. He also reported memory and mood impairment with a history of migraine with aura. MRI of the brain showed diffuse bilateral white matter lesions with sparing of the anterior temporal poles. Both patients satisfied the modified McDonald diagnostic criteria and were initially thought to have MS. However, they did not satisfy the caveat of "no better explanation" and on subsequent testing NOTCH 3 mutations were identified in both patients [1]. These cases highlight the importance of careful clinical assessment and neuroimaging findings in identifying clinical and paraclinical 'red-flags' for a diagnosis other than MS.