Eight subjects underwent four testing sessions, at which repeated measurements of fusional vergence ranges were taken. Near ranges were tested at the first session only Distance ranges were tested at all four sessions. Intra-examiner standard deviations were averaged. The sign indicates a craniocervical disorder. The most common cause is the Arnold-Chiari malformation, followed by cerebellar degeneration.
Basilar invagination is a rare cause of downbeating nystagmus.
However, with appropriate treatment its prognosis is good. Here, we report a case of basilar invagination which presented with downbeating nystagmus and postural hypotension. A 31 year-old Thai male patient had a 20 year history of postural hypotension. He had recurrent pneumonia and cough-induced syncope a year before admission. He complained of symptoms of an acute febrile illness and a productive cough.