Dr. David Newman-Toker is an associate professor of neurology at Johns Hopkins who began presenting data three years ago on the use of eye movements to differentiate acute peripheral vestibulopathy from ischemic episodes. In other words, acute vestibular syndrome patients who have about a 10 to 25% chance of experiencing stroke, vs. vestibular neuritis which is a relatively more benign inner ear disturbance. His group derived an acronym for bedside eye movement tests know as HINTS: HI for Head Impulse test, N for Nystagmus, and TS for Test of Skew or vertical misalignment on cover testing. 12% of stroke patients initially yield false negatives on MRI testing whereas the HINTS testing was 100% accurate. One challenge had been that HINTS is dependent on the skill of the examiner.
Charlie Rose is a widely recognized interviewer who made his reputation on PBS stations but is now part and parcel of CBS This Morning. Dr. Newman-Toker was interviewed on the show today, and he featured a pair of goggles equipped with an infrared video camera cabled to a computer. So now instead of relying on the subjectivity of eye movement patterns when patients have dizziness and vertigo, the goggles can lend objective evidence of the eye movement abnormalities detected by HINTS. The state of how the brain is working when blood flow is impeded shows up immediately in the physiology of eye movements, whereas in MRI as noted above there are false negatives up to two days out until the impeded blood flow shows up in structural brain changes in the MRI. Charlie Rose tossed out an interesting question as to whether the goggles could be used to predict strokes in advance, and the answer is that this isn’t likely, but the ability to identify the patients who are experiencing early stages of stroke and administer clost-busting drugs can be life-saving.
Our colleague in in Maryland, Dr. Stan Appelbaum, who is in Hopkins’ backyard, posed an interesting question. Since we routinely use infrared eye movement recording goggles (Readalyzer or Visagraph) to document saccadic patterns while reading, could this form of elector-oculography be useful in detecting stroke patients? Indeed this may provide clues when the patient has had a “mini-stroke”. or is in the recovery phase of stroke being assessed for vision rehabilitation services. Also keep in mind the implications of alteration in the physiology of eye movement performance when blood flow is impeded by concussion, as noted on the King-Devick website.