Dr. João Lemos, Neurologist and Neuro-Ophthalmologist, sees a broad range of neurological patients and has done so for 15 years.
His video-oculography test battery is vast, and he is a firm believer in the importance of vertical and torsional eye movement assessment.
Interacoustics interviewed Dr. Lemos to learn the clinical utility of video-oculography in neurological patients, and how vertical and torsional eye movement analysis supplement their horizontal counterpart.
What is your typical patient population?
It is rather heterogenous, I must say!
As in any other otoneurology clinic, I often see patients with vestibular neuritis, benign paroxysmal positional vertigo (BPPV), vestibular migraine and vascular vertigo.
The latter group is overrepresented in our clinic, since we are based in a Neurology Department.
Due to the same reason, we are often asked to observe patients with degenerative ataxia, parkinsonism, and other neurodegenerative disorders.
Finally, since we also provide neuro‑ophthalmological assessment, patients with acquired strabismus, congenital nystagmus and optic nerve disease are among our patient population.
What are their conditions?
From a pure oculomotor perspective, our patients show several types of eye movement disorders.
This includes several types of nystagmus:
- Spontaneous
- Eccentric
- Vibration-induced
- Head-shaking-induced
- Positional
Also, our patients show slow, delayed or dysmetric saccades, decomposed ocular pursuit, different forms of saccadic intrusions interrupting ocular fixation, and/or decreased/increased head impulse responses.
Could you elaborate on your video-oculagraphy test battery?
We always perform pursuit, saccade, and optokinetic testing along the horizontal and vertical planes.
We also perform specific tests in patients with position-induced or spontaneous nystagmus and other unusual saccadic intrusions.
As a side point, we also use our video‑oculography equipment to test pupillary function in light and dark in patients with pupillary abnormalities, and to further document pupillary response after pharmacological testing.
Finally, we use EyeSeeCam vHIT to simultaneously test eye and head movements in patients who might show involuntary eye and head movements, such as oculopalatal tremor patients.
Why are you interested in both horizontal and vertical assessment?
There are several neurological disorders that selectively impair upward and/or downward saccades or pursuit.
This includes Parkinson’s disease [PD], other forms of parkinsonism, neurometabolic diseases, and vascular lesions targeting areas dedicated to the generation of vertical eye movements.
Thus, from a pure neurological perspective, vertical assessment is mandatory and equally important as its horizontal counterpart in eye movement assessment.
Do you rely on torsional eye movement analysis to diagnose your patients?
Torsional analysis is a wonderful addition to any oculomotor test battery.
There are several clinical scenarios where torsional assessment becomes very useful and can help the clinician to support or exclude his/her initial diagnosis.
I have found torsional analysis to be very useful in patients with posterior canal BPPV, acute vestibular syndrome and vestibular migraine.
Could you elaborate on torsional nystagmus in these patient populations?
Yes, certainly!
Posterior canal BPPV
In a subset of posterior canal BPPV patients, the torsional component of nystagmus dominates.
Thus, clinicians with only horizontal and vertical recording available will miss torsional nystagmus, ultimately leading to less diagnostic accuracy.
Moreover, even when the torsional nystagmus is less prominent than the vertical or horizontal nystagmus, it is nevertheless important to detect it, as well as to detect its direction (i.e. clockwise versus counterclockwise) and its position-induced reversion to further support posterior canal BPPV diagnosis.
Acute vestibular syndrome
In acute vestibular syndrome, the detection of the torsional component of nystagmus may be critical in patients with central lesions.
In these patients, vertical strabismus (i.e. skew deviation) is often found, which in turn is frequently associated with pure or predominant spontaneous torsional nystagmus.
Again, the lack of such analysis in contemporary eye video-oculography equipment may compromise diagnostic accuracy.
There are of course other entities associated with imbalance and vestibular impairment that classically present with a relevant torsional component of nystagmus, such as oculopalatal tremor.
Vestibular migraine
Finally, in central positional nystagmus, which is often encountered in the clinic in vestibular-migraine patients, analysis of torsion during positional testing is an extra feature.
This can add diagnostic precision when differentiating these patients from classic BPPV patients.
About Dr. João Lemos
Dr. João Lemos, Neurologist and Neuro-Ophthalmologist, has worked in the field of video-oculography testing in neurological patients for 15 years, both as a clinician and researcher. He is based at Coimbra University Hospital Centre, Coimbra, Portugal. Dr. Lemos is the Director of the Neurology of Vision and Balance Unit in the hospital’s Neurology Department, which sees around 1500 neuroophthalmological and neuro‑otological patients annually.
