title: Isolated relative afferent pupillary defect secondary to contralateral midbrain compression.
abstract: BACKGROUND
  Relative afferent pupillary defects are typically related to ipsilateral lesions within the anterior visual pathways.
  
  
  OBJECTIVE
  To describe a patient who had a workup for headache and was found to have an isolated left relative afferent pupillary defect without any other neurological findings.
  
  
  METHODS
  We review the neuroanatomy of the pupillary light reflex pathway and emphasize the nasotemporal bias of decussating fiber projections, which accounts for the relative afferent pupillary defect contralateral to the described lesion. Result Magnetic resonance imaging of the brain revealed a pineal tumor compressing the right rostral midbrain.
  
  
  CONCLUSIONS
  While rare, a relative afferent pupillary defect can occasionally occur secondary to lesions in the postchiasmal pathways. In these circumstances, the pupillary defect will be observed to be contralateral to the side of the lesion.
authors.affiliation: Departments of Neurology and Ophthalmology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75235, USA.
authors.forename: Cheun Ju
authors.initials: CJ
authors.lastname: Chen
authors.forename: Mia
authors.initials: M
authors.lastname: Scheufele
authors.forename: Maushmi
authors.initials: M
authors.lastname: Sheth
authors.forename: Amir
authors.initials: A
authors.lastname: Torabi
authors.forename: Nick
authors.initials: N
authors.lastname: Hogan
authors.forename: Elliot M
authors.initials: EM
authors.lastname: Frohman
mesh_terms: D000328:Adult; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008636:Mesencephalon / Q000473:pathology*; D009408:Nerve Compression Syndromes / Q000150:complications*; D010871:Pinealoma / Q000150:complications* / Q000000981:diagnostic imaging; D011681:Pupil Disorders / Q000209:etiology*; D011859:Radiography; D014795:Visual Pathways / Q000033:anatomy & histology