title: Detection of third and sixth cranial nerve palsies with a novel method for eye tracking while watching a short film clip.
abstract: OBJECTIVE
  Automated eye movement tracking may provide clues to nervous system function at many levels. Spatial calibration of the eye tracking device requires the subject to have relatively intact ocular motility that implies function of cranial nerves (CNs) III (oculomotor), IV (trochlear), and VI (abducent) and their associated nuclei, along with the multiple regions of the brain imparting cognition and volition. The authors have developed a technique for eye tracking that uses temporal rather than spatial calibration, enabling detection of impaired ability to move the pupil relative to normal (neurologically healthy) control volunteers. This work was performed to demonstrate that this technique may detect CN palsies related to brain compression and to provide insight into how the technique may be of value for evaluating neuropathological conditions associated with CN palsy, such as hydrocephalus or acute mass effect.
  
  
  METHODS
  The authors recorded subjects' eye movements by using an Eyelink 1000 eye tracker sampling at 500 Hz over 200 seconds while the subject viewed a music video playing inside an aperture on a computer monitor. The aperture moved in a rectangular pattern over a fixed time period. This technique was used to assess ocular motility in 157 neurologically healthy control subjects and 12 patients with either clinical CN III or VI palsy confirmed by neuro-ophthalmological examination, or surgically treatable pathological conditions potentially impacting these nerves. The authors compared the ratio of vertical to horizontal eye movement (height/width defined as aspect ratio) in normal and test subjects.
  
  
  RESULTS
  In 157 normal controls, the aspect ratio (height/width) for the left eye had a mean value ± SD of 1.0117 ± 0.0706. For the right eye, the aspect ratio had a mean of 1.0077 ± 0.0679 in these 157 subjects. There was no difference between sexes or ages. A patient with known CN VI palsy had a significantly increased aspect ratio (1.39), whereas 2 patients with known CN III palsy had significantly decreased ratios of 0.19 and 0.06, respectively. Three patients with surgically treatable pathological conditions impacting CN VI, such as infratentorial mass effect or hydrocephalus, had significantly increased ratios (1.84, 1.44, and 1.34, respectively) relative to normal controls, and 6 patients with supratentorial mass effect had significantly decreased ratios (0.27, 0.53, 0.62, 0.45, 0.49, and 0.41, respectively). These alterations in eye tracking all reverted to normal ranges after surgical treatment of underlying pathological conditions in these 9 neurosurgical cases.
  
  
  CONCLUSIONS
  This proof of concept series of cases suggests that the use of eye tracking to detect CN palsy while the patient watches television or its equivalent represents a new capacity for this technology. It may provide a new tool for the assessment of multiple CNS functions that can potentially be useful in the assessment of awake patients with elevated intracranial pressure from hydrocephalus or trauma.
authors.affiliation: New York Harbor Health Care System, Manhattan Veteran's Administration; 
authors.forename: Uzma
authors.initials: U
authors.lastname: Samadani
authors.forename: Sameer
authors.initials: S
authors.lastname: Farooq
authors.forename: Robert
authors.initials: R
authors.lastname: Ritlop
authors.forename: Floyd
authors.initials: F
authors.lastname: Warren
authors.forename: Marleen
authors.initials: M
authors.lastname: Reyes
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Lamm
authors.forename: Anastasia
authors.initials: A
authors.lastname: Alex
authors.forename: Elena
authors.initials: E
authors.lastname: Nehrbass
authors.forename: Radek
authors.initials: R
authors.lastname: Kolecki
authors.forename: Michael
authors.initials: M
authors.lastname: Jureller
authors.forename: Julia
authors.initials: J
authors.lastname: Schneider
authors.forename: Agnes
authors.initials: A
authors.lastname: Chen
authors.forename: Chen
authors.initials: C
authors.lastname: Shi
authors.forename: Neil
authors.initials: N
authors.lastname: Mendhiratta
authors.forename: Jason H
authors.initials: JH
authors.lastname: Huang
authors.forename: Meng
authors.initials: M
authors.lastname: Qian
authors.forename: Roy
authors.initials: R
authors.lastname: Kwak
authors.forename: Artem
authors.initials: A
authors.lastname: Mikheev
authors.forename: Henry
authors.initials: H
authors.lastname: Rusinek
authors.forename: Ajax
authors.initials: A
authors.lastname: George
authors.forename: Robert
authors.initials: R
authors.lastname: Fergus
authors.forename: Douglas
authors.initials: D
authors.lastname: Kondziolka
authors.forename: Paul P
authors.initials: PP
authors.lastname: Huang
authors.forename: R Theodore
authors.initials: RT
authors.lastname: Smith
mesh_terms: D020434:Abducens Nerve Diseases / Q000175:diagnosis* / Q000503:physiopathology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D000465:Algorithms; D001331:Automation; D001932:Brain Neoplasms / Q000601:surgery; D002648:Child; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009040:Motion Pictures; D019635:Neurosurgical Procedures; D015840:Oculomotor Nerve Diseases / Q000175:diagnosis* / Q000503:physiopathology; D010775:Photic Stimulation; D011446:Prospective Studies; D012727:Sex Characteristics; D055815:Young Adult
keywords: CN = cranial nerve; EDH = epidural hematoma; ICP = intracranial pressure; SDH = subdural hematoma; TBI = traumatic brain injury; abducent nerve; diagnostic and operative techniques; diplopia; eye movement tracking; hydrocephalus; oculomotor nerve; pds = prism diopters; prepontine cistern