https://doi.org/10.5664/jcsm.9896

R E M : A P U B L I C AT I O N F O R R E S I D E N T S A N D F E L L O W S

Images: polysomnographic findings of nystagmus caused by a midbrain
hemorrhagic stroke
Umer Shoukat, MD1; Danielle R. Glick, MD1; Seemant Chaturvedi, MD2; Montserrat Diaz-Abad, MD3
University of Maryland Sleep Disorders Center, University of Maryland Medical Center, Baltimore, Maryland; 2Department of Neurology and Stroke Program, University of
Maryland School of Medicine, Baltimore, Maryland; 3Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland

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1

Brainstem strokes can present with an array of ophthalmologic findings depending on the location of the lesion. Eye movements are recorded on electrooculogram
during polysomnography for sleep staging. We present the case of a patient with a dorsal midbrain hemorrhagic stroke and nystagmus with distinct findings on the
electrooculogram during polysomnography. These eye movements from nystagmus differed in many aspects (frequency and amplitude) from the classic findings
of other eye movements recorded during different stages of sleep. These polysomnography findings have not been reported in the setting of midbrain stroke.
Future studies comparing nystagmus in multiple sleep stages in stroke patients would be of interest.
Keywords: nystagmus, polysomnography, stroke, dorsal midbrain syndrome, electrooculogram, hypersomnolence, narcolepsy
Citation: Shoukat U, Glick DR, Chaturvedi S, Diaz-Abad M. Images: Polysomnographic findings of nystagmus caused by a midbrain hemorrhagic stroke. J Clin
Sleep Med. 2022;18(5):1479–1482.

BRIEF SUMMARY
Current Knowledge/Study Rationale: Eye movements are recorded on electrooculogram during polysomnography for sleep staging. Brainstem strokes
can present with an array of ophthalmologic complications, including nystagmus.
Study Impact: Images are presented showing the characteristic findings of nystagmus on electrooculogram during polysomnography caused by a
midbrain hemorrhagic stroke. Awareness of these characteristic findings on polysomnography may help in the detection of previously undiagnosed
nystagmus.

INTRODUCTION

to have dorsal midbrain syndrome with convergence-retraction
nystagmus. The vertical nystagmus was pronounced in the right
eye and persisted in all gaze positions, with a lateral nystagmus
of the left eye that was intermittent.
The patient was referred by neurology to the sleep clinic
6 months poststroke due to severe and persistent hypersomnolence, which was new in onset following the stroke. Prior to
this, he slept 8 hours per night, always felt refreshed when waking up, and denied daytime sleepiness or other sleep symptoms,
except for snoring without witnessed apneas. Body mass index
was 25.8 kg/m2 and neck circumference was > 17 inches. The
patient was able to resume a regular office desk job but required
excessive amounts of caffeine (10 cups of coffee and energy
drinks per day) to stay awake. Daily total sleep time was
15 hours and sleep was unrefreshing. The Epworth Sleepiness
Scale3 score was 21/24 and STOP-BANG4 score was 4/8.
The patient underwent a level 3 home sleep apnea test with
an estimated total sleep time > 10 hours, which revealed an
apnea-hypopnea index (events/h) of 21.9 consistent with moderate OSA. He was subsequently started on home autotitrating
continuous positive airway pressure therapy. Despite good
compliance (use 80% of nights for an average of 5 hours and
42 minutes) and reduction of apnea-hypopnea index to near normal (6.0), there was no perceived improvement in excessive
daytime sleepiness or sleep quality. Therefore, a baseline PSG

Sleep disturbances after stroke are common and, given the
known co-occurrence of sleep-disordered breathing and stroke,
polysomnography (PSG) is sometimes performed in these
patients. Obstructive sleep apnea (OSA) is a common finding in
stroke patients and all stroke patients should undergo evaluation
for OSA as untreated OSA represents an independent risk factor
for recurrent stroke. Stroke patients with OSA have worse prognosis and treatment can significantly improve cognitive and
physical disabilities.1 Occasionally, PSG can provide insight
into other coexisting disorders, such as seizure or nystagmus.2
We present the case of a patient post–hemorrhagic midbrain
stroke with an interesting finding on electrooculogram (EOG)
during PSG.

REPORT OF CASE
A 46-year-old male with a history of hyperlipidemia developed
a hemorrhagic stroke of unclear etiology involving the left dorsal midbrain. His course was complicated by increased intracranial pressure requiring ventriculoperitoneal shunt placement
and residual diplopia requiring the use of a right eye patch. On
ophthalmologic examination 6 weeks poststroke, he was noted
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PSG findings of nystagmus in stroke

Figure 1—Nystagmus on stage W.

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On PSG, EOG showing conjugate sharp vertical eye movements during stage W with frequency of 2.8 Hz, mean amplitude 60 mV, and mean duration 0.36 s.
Frequency is faster than eye blinks (0.5–2 Hz). The eye movements are transmitted to the F3-M2 and F4-M1 channels, represented by high amplitude waves.
EOG = electrooculogram, PSG = polysomnography.

(while on continuous positive airway pressure) followed by a
multiple sleep latency test was performed. The multiple sleep
latency test showed mean sleep latency of 6 minutes and 49 seconds, Rapid eye movement (REM) latency of 2 minutes and
15 seconds with 2 sleep-onset REM sleep periods. Given a history of prior stroke and subsequent excessive sleepiness, the
multiple sleep latency test was consistent with narcolepsy type
2 due to medical disorder. The sleep studies were performed in
a fully accredited sleep laboratory and scored according to standardized criteria.5 During the PSG and multiple sleep latency
test, unusual eye movements caused by his nystagmus were
noted (Figure 1, Figure 2, and Figure 3).

DISCUSSION
We present distinct images of nystagmus seen on EOG during
PSG in a patient post–midbrain hemorrhagic stroke. The eye
movements associated with nystagmus in our patient had very
characteristic findings, distinct from other eye movements routinely seen on PSG.
Eye movements on PSG are recorded on the EOG due to the
potential electrical difference across the eyeball, where the front
(cornea) is positive and the back (retina) negative. Eye movement toward an electrode results in downward (positive)

Figure 2—Nystagmus on stage N1 sleep.

On PSG, EOG showing conjugate vertical lower frequency eye movements of 2.5 Hz during stage N1. Also noted are slow rolling eye movements in the first part
of the epoch. The movements are transmitted to the F3-M2 and F4-M1 channels, represented by high amplitude waves. EOG = electrooculogram, PSG =
polysomnography.

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PSG findings of nystagmus in stroke

Figure 3—Nystagmus on REM stage sleep.

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On PSG, EOG showing conjugate vertical sharp waves with frequency 3.5 Hz in REM stage in the second half of epoch. The waves are fast frequency-lower amplitude compared to the classic rapid eye movements of stage REM sleep seen in the first half of the epoch. EOG = electrooculogram, PSG = polysomnography,
REM = rapid eye movement.

deflection and eye movement away from an electrode results in
upward (negative) deflection.6
Previous studies have reported that the nystagmus associated
with central nervous system disorders present while awake
often disappears during sleep. However, it has been suggested
that spontaneous neural activation may allow for nystagmus to
episodically appear in REM sleep and can be present in healthy
adults.7,8 Indeed, nystagmus in vegetative patients has been
reported to persist in REM but disappears in non-REM sleep.9
In the present case, the very distinct pattern of rapid eye movements noted on EOG during wake persisted in non-REM
and REM stage sleep. These vertical upward deflections were
faster in frequency compared with eye blinks in the W (wake)
stage. The deflections were sharp, with an acute angle,
slowing in frequency in stages N1 and N2, with the highest
frequency observed in REM. These eye movements were the
result of rapid upward and adducting saccadic oscillations seen
in convergence retraction nystagmus (Figure 1, Figure 2, and
Figure 3).
The ophthalmologic manifestations of brainstem strokes
depend on the location of the ischemic event. Strokes involving
territories of dorsal midbrain (Parinaud syndrome) can cause
dilated pupils, light near dissociation, lid retraction, lid ptosis,
nystagmus (convergence retraction), and paralysis of upward
and later downward gaze and accommodation.10 Due to a paucity of patients with brainstem syndromes undergoing PSG,
findings of nystagmus can potentially be missed. The findings
of positional nystagmus have been described in patients with
benign paroxysmal positional vertigo but always in the W stage
in association with positional maneuvers and tend to disappear
as patients enter sleep stages.11 Nystagmus associated with
peripheral neuritis is absent during REM sleep.12 To our knowledge, nystagmus has not been described in the context of stroke
Journal of Clinical Sleep Medicine, Vol. 18, No. 5

and represents a finding of interest. Also, nystagmus previously
reported in other case studies disappeared in non-REM sleep,
but interestingly, persisted in our patient. Until more is understood about the persistence of nystagmus into sleep from wake,
PSG should not be used as a screening or diagnostic tool, but
rather attention should be paid to its presence, especially in the
setting of stroke. Future studies comparing nystagmus during
sleep stages in patients with midbrain lesions compared with
other locations (pons, medulla) would be of interest.

ABBREVIATIONS
PSG, polysomnography
EOG, electrooculogram
OSA, obstructive sleep apnea
REM, rapid eye movement sleep stage
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PSG findings of nystagmus in stroke

7. Tauber ES, Weitzman ED, Herman J, Pessah M. Absence of nystagmus during
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ACKNOWLEDGMENTS
The authors thank Angela Dawson, RPSGT, for assistance with obtaining
polysomnographic images.

SUBMISSION & CORRESPONDENCE INFORMATION

9. Gordon CR, Oksenberg A. Spontaneous nystagmus across the sleep-wake cycle
in vegetative state patients. Electroencephalogr Clin Neurophysiol. 1993;86(2):
132–137.

Submitted for publication June 4, 2021
Submitted in final revised form October 18, 2021
Accepted for publication January 11, 2022
Address correspondence to: Umer Shoukat, MD, University of Maryland Sleep
Disorders Center, 100 North Greene Street 2nd Floor, Baltimore, MD 21201; Email:
umershoukatmd@gmail.com

10. Le N, Vickers A, Ugoh PM, et al. Ophthalmologic Manifestations of Brainstem
Stroke Syndromes. American Academy of Ophthalmology. EyeWiki. November 8,
2020. https://eyewiki.org/Ophthalmologic_Manifestations_of_Brainstem_Stroke_
Syndromes. Accessed June 6, 2021.
11. Valko Y, Werth E, Bockisch CJ, Valko PO, Weber KP. Polysomnography reveals
nystagmus from benign paroxysmal positional vertigo. Sleep Med. 2014;15(7):
840–842.
12. Eisensehr I, Noachtar S, Strupp M, von Lindeiner H, Brandt T, B€uttner U. Absence
of nystagmus during REM sleep in patients with vestibular neuritis. J Neurol
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DISCLOSURE STATEMENT

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Copyright 2024 American Academy of Sleep Medicine. All rights reserved.

All authors have seen and approved the manuscript. Work for this study was
performed at the University of Maryland Medical Center, Baltimore, Maryland. The
authors report no conflicts of interest.

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