AUTHOR COMMUNICATION  
Lateral Rectus Superior Compartment Palsy  
Sana Nadeem1  
1Department of Ophthalmology, Foundation University Medical College &Fauji Foundation Hospital, Rawalpindi  
ABSTRACT  
Lateral rectus palsy with hypotropia constitutes a portion of sixth nerve palsy cases in which only the superior part  
of the lateral rectus is affected. We present such a case in a 10-year-old young Pakistani lady who presented with  
a peculiar appearing right esotropia and hypotropia due to acquired lateral rectus palsy along with apparent  
ipsilateral superior rectus underaction. Neuroimaging confirmed atrophy of the superior part of lateral rectus as  
compared to the inferior half. The superior rectus muscle was normal, along with other extraocular muscles. This  
confirmed our suspicion of superior compartment LR palsy. Augmented superior rectus transposition to the lateral  
rectus along with adjustable bimedial recessions and bilateral inferior oblique myectomies were done to restore  
her cosmetic appearance.  
Key Words: Lateral rectus palsy, sixth nerve palsy, esotropia, hypotropia, transposition, strabismus.  
How to Cite this Article: Nadeem S. Lateral Rectus Superior Compartment Palsy. Pak J Ophthalmol. 2020; 36  
(3): 298-301.  
Doi: 10.36351/pjo.v36i3.934  
studied through special MRI techniques also favors  
INTRODUCTION  
neuromuscular  
compartmentalization.  
Selective  
Compartmentalization of extraocular muscles has been  
studied extensively by Demer1 and Clark2, who put  
forth evidence that individual muscles have different  
functions corresponding to different fiber groups. The  
lateral rectus (LR) muscle is believed to have a dual  
embryonic origin and the abducent nerve (cranial  
nerve VI) is believed to innervate the lateral rectus by  
two or more trunks, with separation seen from as far as  
the cavernous sinus to the muscle itself, in autopsies.  
This is believed to divide the lateral rectus into two  
separate compartments: superior and inferior; and a  
sixth nerve palsy, either complete or partial, may  
affect any one of these. This holds true for other  
extraocular muscles as well.  
pathology of the different compartments can yield  
peculiar strabismus patterns, leading to erroneous  
diagnosis. The majority of sixth nerve palsies affect  
the superior compartment more than the inferior  
compartment of the lateral rectus, characterized by an  
esotropia with coexisting ipsilateral hypotropia. This  
may pose the diagnostic dilemma of a vertical muscle  
palsy in addition to the LR palsy1-3.  
We present a case of LR superior compartment  
syndrome in a 10-year-old girl who presented with a  
right sided acquired esotropia with hypotropia,  
accentuated upon abduction.  
Physiological behaviour of extraocular muscles  
CASE PRESENTATION  
A 10-year-old girl presented to the Eye OPD of Fauji  
Foundation Hospital, Rawalpindi; which is a tertiary  
care teaching hospital affiliated with the Foundation  
University Medical College; with a right sided  
esotropia and inability to turn the right eye outwards of  
1½ year duration, consequent to a severe febrile  
illness. Old hospital records were unavailable.  
Previous photographs showed that she was orthotropic  
Correspondence to: Sana Nadeem  
Foundation University Medical College &Fauji Foundation  
Hospital, Rawalpindi  
Email: sana.nadeem018@gmail.com  
Received: October 10, 2019  
Accepted: May 4, 2020  
Revised: May 4, 2020  
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Pakistan Journal of Ophthalmology, 2020, Vol. 36 (3): 298-301  
Lateral Rectus Superior Compartment Palsy  
Fig. I: Right superior compartment lateral rectus palsy with V-pattern esotropia and hypotropia. The hypotropia increased on abduction.  
There is apparent right superior rectus underaction, bilateral inferior oblique overaction and superior oblique underaction.  
Fig. 2: A. Coronal T1W MRI of the orbits showing atrophy of the right superior half of LR (white arrow) B. Post contrast images C. Post  
contrast T2W Coronal section of the orbit and extraocular muscles D. Axial T2W MRI of the brain showing a normal pons (asterisk).  
prior to the event. On examination, her unaided visual  
acuity was 6/6 bilaterally. On prism cover testing, she  
had a right esotropia (RET) of 75 prism diopters (PD)  
along with a right Hypotropia (RHoT) of 5 PD in  
primary distance gaze, RET of 62 PD and RHoT of 2  
PD in upgaze, RET of 80 PD and RHoT of 2 PD in  
Pakistan Journal of Ophthalmology, 2020, Vol. 36 (3): 298-301  
299  
Sana Nadeem  
Fig. 3: Post-operative Appearance at 1 Year.  
downgaze, RET of 60 PD and RHoT of 10 PD in right  
gaze and RET of 70 PD and RHoT of 9 PD in left  
gaze. The esotropia had a ‘V’-pattern of 18 PD. At  
near fixation, she had a RET of 80 PD and no  
hypotropia. She had a right LR underaction of -3 to -4,  
a right medial rectus (MR) overaction of +2, right  
superior rectus (SR) underaction of -2.5, bilateral  
inferior oblique overaction of +3, left LR underaction  
of -2 and bilateral superior oblique underaction of -1.5  
(Figure 1).  
confirmed our suspicion of superior compartment LR  
palsy.  
We performed a bimedial recession of 7 mm (right  
eye on an adjustable suture with a final adjustment to 5  
mm). An augmented transposition of the right SR to  
the LR with  
a
non-absorbable Ethibond 5/0  
augmentation suture, 12 mm behind the insertions was  
done, incorporating 1/4th of both the muscle bellies.  
Bilateral inferior oblique myectomies were also  
performed in a single setting. At 1 year post-  
operatively, she was well aligned, very happy although  
an elevation deficit in upgaze was persistent which we  
attributed to SR transposition, and inferior oblique  
myectomy (Figure 3).  
She had a right face turn. She was thus diagnosed  
with a right partial abducent nerve palsy and there was  
suspicion of a right superior rectus palsy. Titmus fly  
test showed stereopsis at 160 seconds of arc. Worth 4  
dots testing showed alternating suppression. Anterior  
segment was normal. Her fundus examination  
although normal showed bilateral fundus extorsion.  
We presumed that the cause of the sixth nerve palsy  
was infectious, possibly meningitis. Systemically she  
did not have any co-morbid conditions.  
DISCUSSION  
Abducent nerve is the sixth cranial nerve and solely  
innervates the lateral rectus muscle. It primarily  
functions to abduct the eye. Its nucleus lies within the  
pons, ventral to the floor of the fourth ventricle, and its  
fasciculus leaves the brainstem at the ponto-medullary  
junction. The basilar part passes upwards near the  
skull base and is crossed by the anterior inferior  
cerebellar artery. It pierces dura below the posterior  
clinoids and passes the petrous tips, through the  
Dorello canal to enter the cavernous sinus, lying in  
close proximity to the cranial nerves III, IV and V1,  
and the internal carotid artery. It enters the orbit via  
the superior orbital fissure within the annulus of Zinn.  
A sixth nerve palsy can be caused by any insult along  
its long course. Causes of acquired sixth nerve palsy in  
children are trauma, neoplasms, infections,  
A thorough investigative workup was done.  
Complete blood picture was normal, ESR was 24,  
plasma glucose and thyroid profile was normal. Urine  
routine examination, liver function tests and renal  
function tests were normal. Neurological examination  
was normal. A thin section MRI Orbit & Brain with  
contrast (2.5 mm) was ordered, which showed normal  
Pons and failed to reveal a lesion along the path of the  
abducent nerve. The right LR muscle was atrophied as  
compared to the left LR; and its superior half was  
smaller as compared to the inferior half on coronal  
sections (Figure 2). The superior rectus muscle was  
normal, along with other extraocular muscles. This  
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Pakistan Journal of Ophthalmology, 2020, Vol. 36 (3): 298-301  
Lateral Rectus Superior Compartment Palsy  
vasculopathies,  
malformations,  
aneurysms,  
arteriovenous  
of a superior compartment LR paresis. Inferior oblique  
overaction was treated by myectomies, which  
improved her bothersome up shoots on adduction.  
raised  
intracranial pressure,  
demyelination or iatrogenic; to name a few4,5.  
The abducent nerve has a bifid innervation  
structure to divide the lateral rectus into two  
functional neuromuscular compartments; superior and  
inferior. This compartmentalization allows the LR to  
have additional vertical and torsional actions in  
addition to abduction, due to differential contraction of  
these compartments during ocular counter-rolling,  
vertical ductions and vertical vergence. Thus, a lesion  
along the abducent pathway may affect only one  
compartment of the LR to cause a compartmental  
palsy. The lateral rectus superior compartment palsyis  
a newer subtype of abducent palsy, exhibiting  
asymmetric atrophy of the superior compartment only,  
resulting in vertical and torsional abnormalities  
concurrent to the abduction limitation. This results in  
paralytic esotropia coexistent with ipsilateral  
hypotropia and excyclotropia; with the hypotropia  
increasing in abduction. This was clearly seen in our  
case. This may occur in both complete and partial  
palsies of the sixth nerve. Surface coil thin section  
coronal MRI studies have confirmed the existence of  
such palsies, and have shown significant reduction in  
the maximum cross-sections of the superior  
Conflict of Interest  
Authors declared no conflict of interest.  
Author’s Designation and Contribution  
Dr. Sana Nadeem; Assistant Professor: Concept, data  
collection, patient management, manuscript writing.  
REFERENCES  
1. Demer JL. Compartmentalization of extraocular  
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compartment1,2,5,6  
.
Treatment of an acute LR palsy is alternate  
occlusion, botox to the medial rectus and requires  
observation for six months to one year, to allow for  
spontaneous resolution to occur. Surgery for non-  
resolving abducent palsies depends upon the degree of  
deviation and whether the palsy is complete or partial;  
it involves either recession of the contralateral  
synergistic muscle (MR), recession of the direct  
antagonist (ipsilateral MR), LR resection, or  
contralateral antagonist resection (LR). In cases of  
complete palsies, temporal transposition procedures of  
the vertical rectii may be done, like Hummelsheim or  
Jensen. Operating on multiple muscles especially the  
vertical rectii in conjunction with the horizontal rectii  
may pose a risk of anterior segment ischemia. A recent  
therapy for LR palsy is augmented transposition of the  
8. Hoyt CS, Taylor D. Paediatric Ophthalmology and  
Strabismus. Fourth edition. Elsevier: China, 2013: 847-  
850.  
9. Mehendale RA, Dagi LR, Wu C, Ledoux D,  
Johnston S, Hunter DG. Superior rectus transposition  
and medial rectus recession for Duane syndrome and  
sixth nerve palsy. Arch Ophthalmol. 2012; 130 (2):  
195-201.  
SR to the LR with a non-absorbable suture7-10  
.
10. Akar S, Gokyigit B, Pekel G, Demircan A, Demirok  
A. Vertical muscle transposition augmented with lateral  
fixation (Foster) suture for Duane syndrome and sixth  
nerve palsy. Eye (Lond). 2013; 27 (10): 1188-95.  
We thus performed a bimedial recession with an  
augmented SR transposition, as we have found this to  
be safer and effective, and because LR function has  
completely returned, this also supports the hypothesis  
.…….  
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