Downbeat Nystagmus on Physical Exam 65 year old female with new walking difficulty and dizziness. Why downbeat nystagmus? The eyes tend to move down due to gravity. To counteract this the SVN sends faciliatory stimuli to the superior rectus to move the eyes up. This is balanced by floccular inputs that inhibit this. Floccular lesions impair this balance and the SVN to SR impulses overact causing the eyes to move up slowly. The corrective movement causes downbeat 'fast' movements seen as DBN. Hence DBN is a great localizing tool as it points to bilateral floccular lesions. In the absence of structural lesions, look for intra-axial pathologies like autoimmune/paraneoplastic encephalitis. Dr. Boby Varkey Maramattom @bobvarkey #DBN #Downbeat #Nystagmus #PhysicalExam #clinical #video #ocular #ophthalmology #neurology
