CADASIL and multiple sclerosis: A case report of prolonged misdiagnosis

CADASIL is Cerebral Autosomal-Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy [corrected]. (CADASIL) is sometimes misdiagnosed as multiple sclerosis (MS). MS and CADASIL are not known to co-occur and brain magnetic resonance imagining (MRI) findings can help with differential diagnosis. Despite the availability of this information, a case report is presented of a 61-year-old woman who was misdiagnosed with MS at age 50, tested positive for CADASIL at age 56, described incorrectly as having both conditions simultaneously, and continued on MS disease-modifying medications, resulting in financial and physical hardship. Neuropsychological consultation helped initiate removal of the MS diagnosis and treatment. Better understanding is needed among clinicians that MS and CADASIL are not known to co-exist, that no association has been found between MS and the NOTCH3 mutations that cause CADASIL, and that neuroimaging and clinical features can help distinguish between the two conditions in addition to genetic testing. This case study highlights how neuropsychological consultation involves more than testing, can help improve diagnostic decision making, and can improve outcomes by reducing costs to the patient and the healthcare system.