OCULOPALATAL MYOCLONUS: EYE MOVEMENT
STUDIES, MRI FINDINGS AND THE DIFFICULTY OF
TREATMENT
S. J. TALKS and J. S. ELSTON

Oxford

SUMMARY

incoordination. He was unable to stand due to ataxia

Two cases of oculopalatal myoclouus with bilateral
horizoutal gaze palsies are presented. The abnormal
vertical eye movements developed several months after
brain stem haemorrhage.

Eye movement measure­

ments showed rhythmical vertical eye movements at
similar rates

(2.3 Hz and 2.4 Hz), unaffected by

attempts to fixate, converge or gaze in any direction.

T2-weighted MRI scans showed bilateral enlargement

and had increased tone and clonus in his legs.

Reflexes were brisk in both upper and lower limbs
with upgoing plantar reflexes. He had bilateral
horizontal gaze palsies with no movement on

vestibulo-ocular

stimulation. He

nerve palsy. A

strated on autopsy. Both patients had severe oscillopsia
and an attempt was made to improve this by bilateral
disinsertion of the vertical rectus muscles. The pendular

CT scan showed a brain stem

one case enough to relieve the oscillopsia. However,

6 months retrobulbar botulinum toxin was

required

to

continue

to

provide

relief

from

the

oscillopsia. Other treatment options, including pharma­
cological agents, are discussed.

Two months later he developed vertical nystagmus

consists of continuous rhythmical movements of the

soft palate, sometimes in association with synchro­
nous movements of the face, upper arm or dia­

phragm. Occasionally there are also pendular vertical

eye movements and the condition is then called
myoclonus?3

It

causes

debilitating

oscillopsia. Two cases are presented in which we

have assessed the eye movements, performed MRI

and attempted to provide relief of the symptoms. The

treatment options are reviewed.

Case 1

CASE REPORTS

A 54-year-old man, a former heavy smoker, pre­

sented with a 3 hour history of slurred speech and
Correspondence to: Mr S. 1. Talks, Ophthalmology Depart­
ment, The Radcliffe Infirmary, Woodstock Road, Oxford

OX26HE, UK.

Eye (1997) 11, 19-24

tude vertical eye movements in both eyes, with

oscillopsia. Vision deteriorated to 6/36. Two months
later he developed palatal movements synchronous

with the ocular movements. The gaze palsies did not

improve and he remained confined to a wheelchair

due to ataxia.

One year after his initial presentation he under­

Palatal myoclonus was first described in 1886.1 It

oculopalatal

to

with diplopia which was controlled by a 3 dioptre
base-down prism in the left eye. He could see 6/12.
At 7 months he developed continuous large-ampli­

eye movements continued but were greatly reduced, in
after

unable

haemorrhage and an old temporal lobe infarct.

of the inferior olivary nuclei in both cases, which
confirms the expected pathology previously demon­

was

converge and had a right lower motor neurone VII

© 1997 Royal College of Ophthalmologists

went bilateral inferior and superior rectus disinser­

tions. Tenon's capsule was oversewn to prevent

reattachment to the globe. This greatly reduced the

amplitude of vertical movement but did not eliminate

it. His oscillopsia was controlled but he became
aware of horizontal diplopia for near due to his

inability to converge. This was helped by patching

one eye. After 6 months, however, he was again
troubled by some oscillopsia. This was relieved by

the use of retrobulbar botulinum toxin injection (10
units

Dysport),

which

has

been

repeated

after

6 months. He has now been followed up for a year
and we would expect to give repeat injections at 4-6
monthly intervals.

Case 2
A

74-year-old

hypertensive

woman

was

found

unconscious. She responded only to painful stimuli.
Two days later she regained consciousness but had a

right hemiplegia and absent gag reflex. She was fed

20

S. 1. TALKS AND 1. S. ELSTON

Left eye

o,:r�

Right eye

Position

o;�c/�=�
i
0.1

0.2

0.3

0.4

�"i

0.1

%

0.6

0.5

sec

:�.
0.1

VV

0 .5

2

�

, '

4

'T
8

6

0.5

�

Power

':llLAI\ �

10

Hz

(a)

r

0.1

%

""i

sec

Velocity

: �VW'
'W �.,A

�

2

�

0.5

0.3

Degrees/sec

sec

P

��'i

Position

Degrees

Left eye

o�oI=r-,.e",
. �,"",, -�,",:Io, Tro '2

�

4

(b)

6

8

Hz

Right eye

o��
Q3

Ql

':10

Q5

Velocity

Degrees/sec

�
.

%

o

':�'
2

4

i

s�

�,""
s�

...,
10

6

Hz

(c)

by a

Eye movement studies. (a) Case 1 before surgery.
(b) Case 1 after surgery. (c) Case 2 after surgery. Top trace
shows free-running eye movements. Lower traces show an
analysis of one oscillation of the eye. Fourier analysis of the
power spectrum shown on the bottom trace reveals a
frequency of eye movement of 2.4 Hz in case 1 and 2.3 Hz
in case 2.
Fig. 1.

nasogastric tube for the first month but

amplitude rhythmical vertical eye movements, inter­

has remained a problem. Her mental state remained

right gaze palsy. There were synchronous palatal as

gradually managed liquid food, although choking
good.

After

1

year

she

was

referred

to

the

ophthalmic department. She was able to sit in a

mittent blepharospasm, a left gaze palsy and a partial
well as head and upper body movements. Baclofen
had caused a transient improvement in vision. She

wheelchair. She had severe oscillopsia, causing her to

was also taking sodium valproate 400 mg b.d. which

visual acuity was 6/36. She had been treated with

on the eye movements. After 18 months the inferior

spend most of the day with her eyes closed. Her

timoptol 0.5% b.d. for open angle glaucoma, but had

maintained good visual acuity at 6/9 and almost full

fields. On examination she had bilateral large-

had reduced the tremor a little but had had no effect
and superior recti were disinserted in both eyes, as in
case 1. This reduced the amount of vertical move­

ment but did not eliminate it. The oscillopsia was

OCULOPALATAL MYOCLONUS

21

(a)

(b)

(c)

(d)

MRI scans of brain stem in case I (a, b) and case 2 (c, d). (a, c) Blood in IV ventricle. (b, d) Increased signal intensity
reveals inferior olivary enlargement.
Fig. 2.

initially reduced but at 3 months after surgery her
symptoms had largely returned, although less so in
the right eye. Her left eye was therefore patched. She
declined treatment with retrobulbar botulinum toxin,
mainly due to the difficulties of attending hospital
regularly.
Eye Movement Studies

The eye movements of the two cases were measured
with infrared refiectometry. This was carried out
before and after surgery in case 1 and only after
surgery in case 2. The average frequency of the
pendular movements, calculated by Fourier analysis
of the traces, was 2.4 Hz in case 1 and 2.3 Hz in case

2. In case 1 the amplitude of the eye movements was
reduced by surgery but the rhythm of the movements
continued unabated. The pendular movements were
unaffected by attempts to fixate, converge or gaze in
any direction (Fig. 1).
MRI and CT Scan Findings

On T2-weighted MRI both cases showed bilateral
enlargement of the inferior olivary nuclei, with
increased signal intensity and blood in the fourth
ventricle (case 1, Fig. 2a, b; case 2, Fig. 2c, d).
The MRI scan was taken 10 months after the initial
presentation in case 1 and after 14 months in case 2.
eT scans taken at the time of the acute event showed

S. 1. TALKS AND 1. S. ELSTON

22
brain stem haemorrhages, but it was not possible to

resolve the exact site of damage.

tory and oblique movements have been described?·8

The frequencies of the pendular movements were
very similar in the two cases (2.3 and 2.4 Hz) and

similar to the frequencies found by Gresty et at? who

DISCUSSION
Oculopalatal myoclonus follows a lesion in the
dento-rubro-olivary tract and is associated with
enlargement of the inferior olivary nuclei.4.5 This

tract passes from the cerebellar dentate nucleus via

the superior cerebellar penduncle to the contra­

lateral red nucleus and then to the ipsilateral inferior
olivary nucleus through the central tegmental tract.6.7

recorded a mode of between 2.6 and 3 Hz with a
mean of 3.6 Hz in 16 cases of pendular nystagmus,
although

not

all

these

cases

had

oculopalatal

myoclonus. Hoh and Sakata23 reported frequencies

of 2-3 Hz. In some of these cases various movements

modified the nystagmus, such as saccades or near
gaze, but we did not find any modifying factor.

Why the rhythm is at 2.3-2.4 Hz and what the

Damage to the central tegmental tract produces

source of this rhythm is is uncertain, especially

to

involved, from the palate to the diaphragm. The

enlargement of the ipsilateral inferior olive. Damage
the

dentate

nucleus

results

in

contralateral

enlargement. In some cases bilateral inferior olivary

enlargement occurs. Correspondingly oculopalatal
myoclonus may

be

bilateral or

unilateral. The

bilateral or midline form tends to show pendular

movements whereas the lateral form may have more

rotatory movements.8 Both our cases were midline
forms.

As we have shown this enlargement of the inferior

olivary nuclei can be seen with an MRI scan. In both
our cases bilateral inferior olivary enlarg�ment was

found. In unilateral cases of oculopalatal myoclonus
the contralateral inferior olive has been shown to be

enlarged on MRI.9 Only 3 previous MRI reports

have documented bilateral inferior olivary enlarge­
ment

in

clinical

cases

of

midline

oculopalatal

myoclonus.1O-1 2 There have been a total of

17

reported cases of MRI showing olivary enlargement,

but only 4 with oculopalatal myoclonus,u-1 6. In some
cases olivary enlargement has not been demon­

strated on MRJ.ll,1 7 This may relate to the quality
of

the

scan

or

sensitivity

of

the

method,

as

pathologically almost all patients with oculopalatal

myoclonus have enlarged inferior olives. Typical
MRI findings are increased signal intensity on

because of the wide range of body movements

role of the inferior olive is uncertain as the pathology
is of degeneration. In view of the diversity of

structures involved it may be that the rhythm relates

to a property of neuronal function rather than the

particular neuronal circuit involved.3 Inferior olivary

neuronal
generate

cell

membranes

cycles

of

have

excitation

been

and

found

to

inhibition?4

Another theory is that the pendular eye movements

are due to an instability in the vestibulo-ocular reflex
adaptation mechanism, as a result of a dysfunction in

the inferior olive leading to inappropriate oscillatory
discharges by the floccular Purkinje cells.8 In both

our cases the vestibulo-ocular reflex was absent.
Increased glucose metabolism has been shown in the

region of the inferior olive on positron emission
tomography in palatal myoclonus, but not in the one

patient with oculopalatal myoclonus?5 An alterna­

tive argument is that the inferior olive is not the

generator of palatal myoclonus but that the nucleus

ambiguus and adjacent dorsolateral reticular forma­

tion may be, as they are involved in rhythmic activity

such as respirationP

Patients with oculopalatal myoclonus are often

proton- or T2-weighted images and enlargement of
the inferior 01ives.9.1 l

severely debilitated with poor mobility. They may

enlargement to develop.1 8 This is similar to the time

Treatment is difficult. Numerous pharmacological

inferior olivary enlargement is thought to occur

results have been documented in case reports with

pathological changes consist of enlargement and

vacuolation of neurones, neuronal loss, gliosis and

clonazepam,19 trihexyphenidyl?O 5-hydroxytrypto­
phan plus carbidopa?l hyoscine3 and baclofen?2

oculopalatal myoclonus follows a brain stem haem­

been documented not to help?·6.32.33 Treatment has

There is a latency of 2-49 months for olivary

well

be

mentally

alert

and

find

particularly serious addition to

oscillopsia

a

their handicaps.

delay in onset of the rhythmical movements. The

agents have been tried with varying success. Good

secondarily to transneuronal degeneration.4

sodium valproate,26 phenytoin,27 carbamazepine,28

The

astrocytic hypertrophy.19-21 In the majority of cases

However, in other case reports these agents have

orrhage, as in our two cases. All the cases in which

also been tried without much success with prochlor­

previous

can be a problem. One of our patients had been

MRI has been
brain

performed

stem

showed

haemorrhage.

evidence

of

Oculopalatal

myoclonus, can, however, occur with certain neo­

plasms, degenerative diseases,

encephalitis. after

trauma and with multiple sclerosis?2

The eye movements in oculopalatal myoclonus are

usually pendular vertical movements, although rota-

perazine, tetrabenazine and diazepam?,6,34 Sedation

treated with baclofen and sodium valproate without
success.

Optical dampening of oscillopsia has been tried

using high minus-power contact lenses in conjunction
with high plus-power spectacles?5 but this is not

OCULOPALATAL MYOCLONUS

always satisfactory. Botulinum toxin can be of
benefit, either given directly into the muscles or
retrobulbar. However, it needs to be given every 3-4
months and ptosis can be a problem?6 Retrobulbar
botulinum toxin can also cause the loss of the
vestibular ocular reflex, which may be a problem,
especially in patients who can walk.
Our patients both had poor mobility and found
travelling to the hospital difficult. They therefore
decided to opt for surgery as an attempt at a more
permanent solution. We did not feel pre-operative
botulinum toxin injections would help clarify the
likely success of surgery. Surgery for nystagmus is
usually of benefit where there is a null point and is
carried out to correct a compensatory head pos­
ture?7 Surgery to try to decrease the nystagmus itself
and to control oscillopsia has not frequently been
performed. Retroequatorial recessions of the hori­
zontal recti for congenital nystagmus have been
found to have some success?8 Detaching an extrao­
cular muscle and fixing it to periosteum has been
tried?9 Spalton et at. 32 carried out 10 mm recessions
on the inferior and superior rectus of one eye of a
patient with ocular myoclonus without success. We
disinserted the inferior and superior recti of both
eyes in both patients to try to produce a maximum
decrease in vertical movements. In case 2 this only
dampened the oscillations mildly, but in case 1 it did
provide temporary relief of oscillopsia. The much
reduced oscillopsia was then controlled by botulinum
toxin injections. Surgery of this nature could lead to
vertical diplopia, but with surgery to both eyes this
would not be expected to be a problem. Much more
of a problem is adequate control of the vertical
oscillations.
In conclusion, MRI in oculopalatal myoclonus can
help confirm the diagnosis by showing inferior
olivary enlargement. Surgery may help reduce
oscillopsia but additional botulinum toxin injections
may be required.
We would like to acknowledge the help of M. R. Baker,
DPhil, ARCS, Research Scientist, and P. Anslow, FRCR,
Consultant Radiologist, in preparing this paper.
Key words: Oculopalatal myoclonus, MRI, Nystagmus, Rectus
muscle.

REFERENCES
1. Spencer HR. Pharyngeal and laryngeal 'nystagmus'.
Lancet 1886;2:702.
2. Guillian G. The syndrome of synchronous and rhythmic
palato-pharyngo-Iaryngo-oculo-diagphragmatic
myo­
clonus. Proc R Soc Med 1938;31:1031-8.
3. Gresty MA, Ell n, Findley LJ. Acquired pendular
nystagmus: its characteristics, localising value and
pathophysiology. J Neurol Neurosurg Psychiatry
1974;37:570-7.
4. Gautier JC, Blackwood W. Enlargement of the inferior
olivary nucleus in association with lesions of the central

23
tegmental tract or dentate nucleus. Brain 1961;84:
341-61.
5. Koeppen AH, Barron KD, Dentinger MP. Olivary
hypertrophy: histochemical demonstration of hydro­
lytic enzymes. Neurology 1980;30:471-80.
6. Guillain G, Mollaret P, Bertrand I. Sur la h�sion
responsable du syndrome myoclonique du tronc
cerebral. Etude anatomique d'un cas demonstratif
sans lesions focales. Rev NeuroI 1933;3:666-74.
7. Lapresle J. Rhythmic palatal myoclonus and the
dentato-olivary pathway. J Neurol 1979;220:223-30.
8. Nakada T, Kwee IL. Oculopalatal myoclonus. Brain
1986;109:431-41.
9. Chang YY, Tsia TC, Shih PY, Liu LS. Unilateral
symptomatic palatal myoclonus: MRI evidence of
contralateral inferior olivary lesion. Kaohsiung J Med
Sci 1993;9:371-6.
10. Sperling MR, Herrmann C Jr. Syndrome of palatal
myoclonus and progressive ataxia: two cases with
magnetic
resonance
imaging.
Neurology
1985;
35:1212-4.
11. Yokota T, Hirashima F, Furukawa T, Tsukagoshi H,
Yoshikawa H. MRI findings of inferior olives in palatal
myoclonus. J Neurol 1989;236:115-6.
12. Massry GG, Chung SM. Magnetic resonance imaging
findings in oculopalatal myoclonus. Am J Ophthalmol
1994;117:811-2.
13. Uchino A, Hasuo K, Uchida K, Matsumoto S,
Tsukamoto Y, Ohno M, Masuda K. Olivary degenera­
tion after cerebellar or brain stem haemorrhage; MRI.
Neuroradiology 1993;35:335-8.
14. Zarranz n, Fontan A, Forcadas I. MR imaging of
presumed olivary hypertrophy in palatal myoclonus.
AJNR 1990;11:1164.
15. Hirono N, Kameyama M, Kobayashi Y, Udaka F,
Mezaki T, Abe K, Nishitani N. MR demonstration of a
unilateral olivary hypertrophy caused by pontine
tegmental hematoma. Neuroradiology 1990;32:340-2.
16. Revel MP, Mann M, Brugieres P, Poirier J, Gaston A.
MR appearance of hypertrophic olivary degeneration
after contralateral cerebellar hemorrhage. AJNR
1991;12:71-2.
17. Keane JR. Acute vertical ocular myoclonus. Neurology
1986;36:86-9.
18. Matsuo F, Ajax ET. Palatal myoclonus and denerva­
tion supersensitivity in the central nervous system. Ann
Neurol 1979;5:72-8.
19. Goto N, Kaneko M. Olivary enlargement: chronologi­
cal and morphometric analyses. Acta Neuropathol
1981;54:275-82.

20. Kurachi M, Nakamura I, Katsukawa K, Kobayashi K,
Sano Y, Isaki K, Yamaguchi N. Olivary hypertrophy in
a case with palatal myoclonus: light and electron
microscopic study. Folia Psychiatr Neurol Jpn 1985;
39:543-50.

21. Pierot K, Cervera-Pierot P, Delattre JY, Duyckaerts C,
Chiras J, Brunet P. Palatal myoclonus and inferior
olivary lesions: MRI pathologic correlation. J Comput
Assist Tomogr 1992;16:160-3.
22. Deuschl G, Mischke G, Schenck E, Schulte-Monting J,
Lucking CH. Symptomatic and essential rhythmic
palatal myoclonus. Brain 1990;113:1645-72.
23. Itoh Y, Sakata E. Acquired pendular oscillations after
brain stem hemorrhage. Acta Otolaryngol 1989;
(Suppl)468:205-8.
24. Llinas RR, Yarom Y. Electrophysiological properties
of mammalian inferior olivary cells in vitro. In:
Courville J, de Montigny C, Lemarre Y, editors. The

24
olivary nucleus: anatomy and physiology. New York:
Raven Press, 1980:379-88.
25. Dubinsky RM, Hallett M, Di Chiro G, Fulham M,
Schwankhaus J. Increased glucose metabolism in the
medulla of patients with palatal myoclonus. Neurology
1991;41:557-62.
26. Lefkowitz D, Harpold G. Treatment of ocular myo­
clonus with valproic acid. Ann NeuroI 1985;17:103-4.
27. Ferro LM, Castro-Caldas A. Palatal myoclonus and
carbamazepine. Ann Neurol 1981;10:402.
28. Sakai T, Shiraishi S, Murakami S. Palatal myoclonus
responding to carbamazepine. Ann Neurol 1981;
9:199-200.
29. Gledhill RF, Wiles CM. Clonazepam and branchial
myoclonus. Ann NeuroI 1977;1:306-7.
30. Jabbari B, Gunderson CH. Palatal myoclonus respond­
ing to trihexyphenidyl. Ann Neurol 1983;14:95.
31. Magnussen 1, Dupont E, Prange-Hansen A, et al.
Palatal myoclonus treated with 5-hydroxytryptophan
and a decarboxylase inhibitor. Acta Neurol Scand
1977;55:251-3.
32. Spalton DJ, Sanders MD, Gresty M, Rosen ES. Ocular

S. J. TALKS AND J. S. ELSTON
myoclonus and oscillopsia: a problem of treatment.
Trans Ophthalmol Soc UK 1980;100:507-8.
33. Carlow TJ. Medical treatment of nystagmus and ocular
motor disorders. Int Ophthalmol Clin 1986;26:251-64.
34. Jankovic J, Pardo R. Segmental myoclonus: clinical and
pharmacologic study. Arch Neurol 1986;43:1025-31.
35. Leigh RJ, Rushton DN, Thurston SE, et al. Effects of
retinal image stabilization in acquired nystagmus due
to neurologic disease. Neurology 1988;38:122-7.
36. Ruben ST, Lee JP, O'Neil, Dunlop I, Elston JS. The
use of botulinum toxin for treatment of acquired
nystagmus and oscillopsia. Ophthalmology 1994;
101:783-87.
37. Lee JP. Surgical management of nystagmus.
1988;2:44-7.

Eye

38. von Noorden GK, Sprunger DT. Large rectus muscle
recessions for the treatment of congenital nystagmus.
Arch OphthalmoI 1991;109:221--4.
39. Colburn JE. Fixation of the external rectus muscle in
nystagmus and paralysis. Am J Ophthalmol 1906;
23:85-8.