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Acta Otorrinolaringol Esp. 2016;67(1):e1---e3
www.elsevier.es/otorrino
CASE STUDY
Periodic Alternating Nystagmus --- A Case Report夽
Nistagmus alternante periódico: caso clínico
Diana Cunha Ribeiro,a,∗ Nicolás Pérez-Fernandesb
a
Department of Otorhinolaryngology, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal
Department of Otorhinolaryngology, Clínica Universitaria de Navarra, University Hospital and Medical School, University
of Navarra, Pamplona, Spain
b
Received 21 May 2014; accepted 8 August 2014
Case Report
A 71-year-old man complained of 5 years of progressive postural instability, more intense when standing up from bed,
especially in darkness and during the day when walking on
street. It lasted a few seconds and resolved spontaneously.
No reference to vegetative symptoms, hearing loss or rotatory movements.
Relevant personal clinical antecedents were slowly progressive visual loss that began at age 20, followed by the
diagnosis of pigmentary glaucoma at age 40, and three
episodes of retinal detachment repair (twice in the right
eye and once on left eye, during the last two decades), and
6 months ago he underwent a combined surgery directed to
right glaucoma and cataract.
Other antecedents were lymph node tuberculosis and
radical prostatectomy three years ago and benign paroxysmal positional vertigo of horizontal and posterior right
semicircular canals treated with repositioning maneuvers
two years ago.
夽 Please cite this article as: Cunha Ribeiro D, Pérez-Fernandes N.
Nistagmus alternante periódico: caso clínico. Acta Otorrinolaringol
Esp. 2016;67:e1---e3.
∗ Corresponding author.
E-mail address: [email protected]
(D. Cunha Ribeiro).
The latest otoneurologist examination detected a spontaneous horizontal nystagmus in the primary position that
periodically reverses its direction with a transition period of
several seconds, with visual suppression.
An approximately 155 s left-side nystagmus (slow phase
velocity (SPV): 4.9◦ /s), an approximately 15 s pause with
low amplitude square-wave jerks, and an approximately 105
right-side nystagmus were recorded (video 1# , Fig. 1).
With straight head-hanging position an upbeat nystagmus appeared with a small torsional component. The smooth
pursuit and saccadic pursuit were normal.
His ophthalmological status on the latest otoneurological examination was 10/10 visual acuity on right eye, and
50/100 visual acuity on the left eye.
A mild bilateral hearing loss was found.
We performed the head impulse test to evaluate the
vestibulo-ocular reflex evoked by the stimulation of the 6
semicircular canals with a video-based system (v-HIT, GN
Otometrics, Denmark) and the results were normal for
both ears and each semicircular canal (normal gain, no
refixation saccades). Sinusoidal harmonic accelerations
(frequency range 0.01---0.64 Hz, peak velocity: 50◦ /s)
showed a phase advance and normal gains and symmetry,
# Video---The patient shows a 9 min sequence of periodic alternating nystagmus (PAN) that consists of left beating nystagmus
(more durable), a null phase, and right beating nystagmus, and
then a repetition of all phases. Link: https://www.dropbox.com/s/
e5egzk6n1hvebuf/PAN%20final.m4v.
2173-5735/© 2014 Elsevier España, S.L.U. and Sociedad Española de Otorrinolaringología y Patología Cérvico-Facial. All rights reserved.
Document downloaded from http://www.elsevier.es, day 31/07/2017. This copy is for personal use. Any transmission of this document by any media or format is strictly prohibited.
e2
D. Cunha Ribeiro, N. Pérez-Fernandes
Nistagmo
dirección
Izquierda
Derecha
Arriba
Abajo
20
Ojo derecho
Nistagmos/s
a.VFL
Ojo izquierdo
Nistagmos/s
a.VFL
Nistagmos
Nistagmos
5.4º/s
0.2º/s
119
4.9º/s
0.3º/s
160
6.9º/s
0.1/s
84
4.3º/s
0.1/s
61
20.7º/s
8.7º/s
0.0/s
26
20
21.8º/s
10.4º/s
0.0/s
17
11
0.0/s
0.0/s
D
Posición horizontal de ojo [º]
10
0
–10
–20
–30
20
I
Nistagmos I
VFL horizontal [º/s]
10
0
–10
–20
–30
50
Nistagmos D
Ar
Posición vertical de ojo [º]
40
30
20
10
0
20
Ab
Nistagmos Ab.
VFL vertical [º/s]
10
0
–10
–20
–30
Nistagmos Ar.
2:15
2:20
2:25
2:30
2:35
2:40
2:45
2:50
2:55
3:00
3:05
Figure 1 Videonystagmography register of spontaneous nystagmus without visual fixation shows a periodic alternating nystagmus
(PAN), with the left beating nystagmus, a null phase and a right beating nystagmus.
without per-rotatory visual suppression with ocular fixation,
generating a sinusoidal pattern. On visual-vestibular interaction, a sinusoidal harmonic acceleration with optokinetic
stimulus (frequency range 0.01---0.64 Hz, peak velocity:
50◦ /s) phase, gain and symmetry were normal.
Magnetic resonance imaging revealed periventricular
leukoencephalopathy on oval centers bilaterally.
The patient underwent treatment with baclofen (GABAbergic drug), 30 mg/day without recovery; however after
that, the patient treatment a new surgical treatment on
the left eye, recovered the visual acuity and the PAN disappeared.
Discussion
Acquired periodic alternating nystagmus (PAN) is an uncommon disorder in which there is a continuous spontaneous
horizontal nystagmus, present in central gaze, that periodically reverses direction (approximately every 90---120 s),
with a null period of several seconds on which downbeat
nystagmus and square wave jerks.1---4
PAN can be congenital or acquired.1---7 Acquired PAN
has been reported in various neurologic disorders, such
as Arnold---Chiari malformation and other hindbrain
anomalies, multiple sclerosis, cerebellar degenerations,
cerebellar tumor, abscess, cyst, and other mass lesion,
Creutzfeldt-Jakob disease, ataxia telangiectasia, brainstem
infarction, lithium, anticonvulsant medications and
seizures, hepatic encephalopathy, trauma, following visual
loss (vitreous hemorrhage or cataract) and aperiodic form
as a component of congenital nystagmus, especially in
albinos.
In most patients with acquired PAN, the nystagmus has
the same characteristics in light or in darkness.1
Because the period of oscillation is about 4 min, the
diagnosis may be missed unless the examiner observes
the nystagmus for several minutes.1
The per-rotatory nystagmus is normally suppressed by
visual fixation; however, this suppressive effect is lost after
damage of the uvulonodulus.3
The pathomechanisms thought to be responsible for
PAN came from experimental studies of ablation of the
cerebellar nodulus and uvula (NU) in monkeys, causing
PAN in darkness.1---5 The cerebellar NU control the time
course of rotationally induced nystagmus (‘‘velocity storage’’ system). Thus, dysfunction of NU causes PAN by
prolongation of velocity storage and the instability of
VOR. It was postulated that normal vestibular ‘‘repair
mechanisms’’ act to reverse the direction of nystagmus,
producing the oscillations. And the latter can be blocked
by visual stabilization mechanisms. However, cerebellar disease that causes PAN also impairs these ‘‘compensatory
mechanisms’’.
Normal results in the vHIT precluded more examinations
as there is convincing evidence of normal peripheral
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Periodic Alternating Nystagmus
vestibular function. Although the caloric test is possible,
some caution must be taken into account at the time
of evaluating results as it is recommended to observe
nystagmus during the whole test to disclose reversal of the
expected caloric nystagmus due to PAN.
The baclofen (GABAb-ergic drug) abolishes successfully
acquired PAN due to its inhibitory control on the vestibular
rotational responses on Purkinje cell activity of the nodulus
and uvula.1,4
In our patient there was no evidence of any underlying
neurologic disorder even on MRI, and we presume that PAN
emerged due to an impairment of central visual stabilization
mechanisms and deficient visual input and fixation, caused
by his ophthalmological antecedents.
Another point of interest in our case was the asymmetry of the nystagmus, probably due to the asymmetry of
visual input (deficient visual acuity on left eye), suggesting
that the left VOR may be relatively more unstable than the
right.
It was postulated that unilateral visual loss itself does
not cause PAN7 and in our case it was not demonstrated.
However, PAN was abolished after the latest successful ophthalmologic surgery.
e3
Conflict of Interest
No conflict of interests.
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