title: Chiari I malformation presenting as downbeat nystagmus: clinical presentation, diagnosis, and management.
abstract: BACKGROUND
  Chiari I malformation is a congenital, neurological condition that is characterized by defects of the skull base resulting in herniation of the cerebellum through the foramen magnum into the cervical spinal canal. Because the condition can result in visual symptoms, patients will often search for answers from their eye care providers;
  
  
  METHODS
  A 28-year-old Hispanic diabetic male with a 10-year history of nystagmus was referred to the neuro-ophthalmic disease clinic following the initiation of oscillopsia 1 year previous. Downbeat nystagmus, which worsened in right and down gaze, was evident. Cranial nerve testing was unremarkable, but the patient did report trouble with choking on food and drink. Neuroimaging revealed Chiari I malformation. The patient underwent a suboccipital craniectomy which resulted in lessened nystagmus and improved symptoms;
  
  
  CONCLUSIONS
  The majority of patients with Chiari I malformation have an onset of symptoms in the second or third decade of life. Most commonly, a suboccipital headache that worsens with Valsalva maneuver is present. Visual symptoms include retro-orbital pain, flashing lights or floaters, blurred vision, photophobia, diplopia, transient vision loss, and peripheral vision loss. Objective evidence is often lacking in these patients; however, horizontal or vertical nystagmus is present in up to 45% of those with Chiari I malformation. Surgery has proven to be an effective and safe method to treat symptomatic Chiari I malformation.
authors.affiliation: Pacific University College of Optometry, 2043 College Way, Forest Grove, OR 97116, USA. goodwin@pacificu.edu
authors.forename: Denise
authors.initials: D
authors.lastname: Goodwin
authors.forename: Ami R
authors.initials: AR
authors.lastname: Halvorson
mesh_terms: D000328:Adult; D001139:Arnold-Chiari Malformation / Q000150:complications* / Q000175:diagnosis / Q000601:surgery; D003937:Diagnosis, Differential; D005133:Eye Movements; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D019635:Neurosurgical Procedures / Q000379:methods*; D009759:Nystagmus, Pathologic / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology