Correspondence - ICO Library

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Binocular Vision & Inferior Oblique Muscle Palsy with ‘Paradoxical’ V-Pattern Strabismus FIRST Quarter of 2011
Strabology Quarterly© E. Khawam, MD and D. Fahed, MD Volume 26 (No.1)
A Medical Scientific e-Periodical Pages 51-60
Paradoxical A-pattern esotropia with primary marked
bilateral primary over-action of the IO muscles (14-16): We
believe factors related to horizontal rectus muscle function in upand
down-gazes may explain this rare pattern seen in reports
(14): medial rectus underaction in downgaze, and lateral rectus
underaction in upgaze being the cause of the A-pattern despite
bilateral IO overaction. In such a situation, we advocated supraplacement
of the MR muscles to deal with the A-pattern (17),
plus surgical weakening of the IOs to prevent a postoperative
development of a V-pattern by their abducting forces.
• Paradoxical A-pattern in bilateral SO palsy was reported by
Mansour and Reinecke (8). They attributed the pathophysiology
of A-pattern, in cases of SO palsy, to the spread of comitance
with a) either inhibitional innervational pseudo-palsy of the
synergist of the paretic muscle (the IR of the ipsilateral eye),
resulting in A-exotropia (Figure 6 directly below, ), ...
Our case herein reported, of a
patient with a right IO palsy
fulfilling all the Parks’ (17), 3-
step-diagnostic criteria of cyclovertical
muscle palsy, showed a
paradoxical V-pattern in her horizontal
exodeviation. In agreement
with Mansour &Reinecke’s
hypothesis, we believe the pathophysiologic
mechanism of this
paradoxical V-pattern with IO
palsy can be explained by the
spread of comitance resulting in
inhibitional innervational pseudopalsy
of the synergist of the paretic
muscle, the right SR muscle
of the affected eye, resulting in
V-exotropia (Figure 8, below).
Figure 6 (Khawam & Fahed): Right superior
oblique muscle palsy. Spread comitance
to the ipsilateral inferior rectus muscle(RIR).
...or b) to inhibitional innervational pseudopalsy
of the synergist of the yoke of the
antagonist (the IO muscle of the fellow eye),
resulting in A-esotropia (Figure 7 , below).
Figure 8 (Khawam & Fahed): Right
inferior oblique muscle palsy. Spread of
comitance to the ipsilateral superior rectus
muscle (RSR) resulting in V- exotropia.
Had the spread of comitance reached the
synergist of the yoke of the antagonist –the
contralateral left SO, the resulting pattern would
have been a V-esotropia .
(Figure 9, top next page, References).
Figure 7 (Khawam & Fahed): Right superior
oblique muscle palsy. Spread comitance to the
contralateral inferior oblique muscle (LIO).