Downbeating Nystagmus and due to Basilar Invagination
PIYANUD PRATIPARNA WATR, M.D.*, CHAIWIT T ANAPAISAL, M.D.**, SUTHIPUN JITPIMOLMARD, M.D., D.C.N. (Lond.)* Postural Hypotension SOMSAK TIAMKAO, M.D.*, JATURAT KANPITTAYA, M.D.***,
Affiliation : * Department of Medicine, **Department of Surgery, ***Department of Radiology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand.
Downbeating nystagmus is an involuntary vertical rhythmic eye movement with the fast
component in the downward direction. 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. The physical examination showed
high grade fever, postural hypotension and medium crepitation in the right upper lobe. The neuro-
logical examination showed downbeating nystagmus, atrophy and fasciculation of the right side
of the tongue, atrophy of the right sternocleidomastoid muscle, mild weakness of the extremities
and generalized hyperreflexia. The cervical spine X-ray revealed upward displacement of the ver-
tebral bodies of Cl and C2, with a mild narrowing of the space between Cl and the occiput. The
CT-myelogram and MRI showed upward displacement of Cl with overriding of the dens over the
anterior lip of the foramen magnum ; this also compressed the medulla. Syringomyelia was seen
at the C l-C5 level.
We report a patient who presented with postural hypotension, recurrent pneumonia and
downbeating nystagmus due to basilar invagination. The symptoms were aggravated by cough
which caused an increase in intracranial pressure. This resulted from medulla compression in the
foramen magnum by the first cervical spine. The treatment of choice was surgical decompression.
Keywords : Downbeating Nystagmus, Postural Hypotension, Basilar Invagination
