Detection of third and sixth cranial nerve palsies with a novel method for eye tracking while watching a short film clip

Abstract

OBJECT 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.

Oculometric Assessment of Sensorimotor Impairment Associated with TBI

“…We conclude that characteristic datasets aggregated from standardized oculomotor test batteries (such as COBRA) may allow clinicians to detect, quantify, and characterize impairments from transient brain insults (e.g. due to trauma, drug toxicity, or alcohol) and permanent injuries 6 , 14 , 18 ; to detect the onset of degenerative, 22 developmental, 38 and psychiatric 39 , 40 disorders and track their progression; and to evaluate the effectiveness of candidate therapeutic interventions, even in the absence of an individual baseline.…”

“… 4 , 5 Thus, oculomotor examinations are used in both clinical (e.g. localizing lesions, 3 diagnosing vestibular disorders, 4 detecting cranial nerve palsies 6 ) and field (e.g. detecting alcohol intoxication 7 , 8 and fatigue 9 , 10 ) settings.…”

Traumatic brain injury reduction in athletes by neck strengthening (TRAIN)

“…This data is then analyzed using novel algorithms to yield 89 metrics involved in eye movement and tracking. This method has been shown to detect disconjugate eye movement associated with head trauma [ 21 ], as well as changed ratios of vertical to horizontal eye movements in patients with cranial nerve palsies [ 22 ].…”

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“…TBI has long been associated with impaired disconjugate eye movement. It has only been recently quantitatively measured via eye tracking devices ( Pearson et al, 2007 ; Samadani et al, 2015a ; Samadani et al, 2015b ). In the future, our goal must be directed towards standardizing the results from these devices and building and interface that is user-friendly so that it can easily be applied in the field (i.e., by EMS personnel, coaches, bystanders, etc.).…”