Modern Plastic Surgery, 2013, 3, 65-67
http://dx.doi.org/10.4236/mps.2013.32012 Published Online April 2013 (http://www.scirp.org/journal/mps)
65
Congenital Unilateral Hypoplasia of the Orbicularis
Oris Muscle: A Rare Cause of Congenital Unilateral
Upper Lip Palsy
Sadık Şentürk1, Duran Efe2
1Department of Plastic and Reconstructive Surgery, Mevlana (Rumi) University Hospital, Konya, Turkey; 2Department of Radiology,
Mevlana (Rumi) University Hospital, Konya, Turkey.
Received January 14th, 2013; revised February 20th, 2013; accepted February 28th, 2013
Copyright © 2013 Sadık Şentürk, Duran Efe. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Asymmetric facial appearance may originate from abnormalities of facial musculature or facial innervation. Congenital
absence or hypoplasia of facial muscles has not been known except for the depressor anguli oris muscle. Even,
congenital unilateral hypoplasia of the orbicularis oris muscle cause of unilateral upper lip palsy has not been reported
in the literature up to day. In this report, we present a patient with congenital unilateral upper lip palsy although the
facial nerve was normal.
Keywords: Congenital Upper Lip Palsy; Unilateral Hypoplasia; Orbicularis Oris Muscle
1. Introduction
Asymmetric facial appearance may occur abnormalities
of facial musculature or facial innervation. Asymmetric
face is occur in 0.2% - 0.6% of newborns [1-3]. Con-
genital absence or hypoplasia of facial muscles is un-
common anomaly causing a remarkable aesthetic de-
formity. Congenital absence or hypoplasia of facial mus-
cles has not been known except for the depressor anguli
oris muscle. Even, congenital unilateral hypoplasia of the
orbicularis oris muscle cause of unilateral upper lip palsy
has not been reported in the literature up to day. In this
report, we present a patient with congenital unilateral
upper lip palsy although the facial nerve was normal.
Clinical presentation of patients with asymmetric face is
characterized by the lip appears distorted towards the
healthy side. Diagnosis can be detectable by the clinical
picture, an electromyographic and magnetic resonance
imaging study [4,5].
2. Case Report
A 33-year-old girl presented with asymmetric movement
of upper lip when she whistled and ate. The patient de-
nied having any previous trauma, major infection, or
facial surgery and was unaware of any other associated
congenital deformity. Her medical history was otherwise
unremarkable. The patient was born at term after an un-
eventful pregnancy. Physical examination revealed thin
unilateral upper lip. The face appeared symmetric at rest
(Figure 1). The patient had inward deviation of right
upper lip when she whistled (Figure 2). Facial nerve
function, as determined by frowning/forehead, wrinkling,
eye closure, nasolabial fold depth, and tearing, was sym-
metric. Neurologic exam was normal. Magnetic reso-
nance imaging of the upper lip were unilateral hypoplasia
of the orbicularis oris muscle (Figure 3).
3. Discussion
Asymmetric facial appearance may occur abnormalities
of facial musculature or facial innervation. Asymmetric
face is occur in 0.2% - 0.6% of newborns [1-3]. Con-
genital absence or hypoplasia of facial muscles is un-
common anomaly causing a remarkable aesthetic defor-
mity. Congenital absence or hypoplasia of facial muscles
has not been known except for the depressor anguli oris
muscle. Even, congenital unilateral hypoplasia of the
orbicularis oris muscle has not been reported in the lit-
erature up to day. Clinical presentation of patients with
congenital unilateral hypoplasia of the orbicularis oris
includes typical clinical picture, which includes upper lip
asymmetry during whistling while forehead wrinkling,

Congenital Unilateral Hypoplasia of the Orbicularis Oris Muscle:
A Rare Cause of Congenital Unilateral Upper Lip Palsy
66
Figure 1. Patient with right-sided asymmetric upper lip at
rest.
Figure 2. The upper lip is pulled toward the intact left side.
Figure 3. Magnetic resonance imaging of the upper lip were
unilateral hypoplasia of the orbicularis oris muscle.
nasolabial fold depth, and eye closure remain intact and
equal on both side. Diagnosis can be detectable by the
clinical picture, an electromyographic and magnetic re-
sonance imaging study [4,5]. Differential diagnosis of
upper lip asymmetry includes facial nerve paralysis and
trauma factors. Facial nerve lesions may cause weakness
of facial expressions; however, congenital unilateral hy-
poplasia of the orbicularis oris afflicts upper lip while
other functions of facial nerves are preserved.
Congenital palsy of the depressor anguli oris muscle,
said to have an asymmetric crying facies is characterized
by facial asymmetry that is usually first noticed when the
infant cries, because half of the lower lip manifests a
pulled-down, outward appearance. It is also known as
congenital unilateral lower lip palsy, congenital hypo-
plasia of the depressor anguli oris muscle, and partial
facial paralysis [6-8]. A wide variety of anomalies in-
volving cardiovascular, gastrointestinal, genitourinary,
skeletal, and central nervous systems may be seen in
children with congenital hypoplasia of depressor anguli
oris [9-13].
The pathogenesis of congenital absence or hypoplasia
of facial muscles has not been established. Up to day,
intrauterine molding, viral infection during pregnancy,
and heredity have been suggested as causative factor
[14,15]. Nonetheless, pathogenesis of congenital absence
or hypoplasia of facial muscles appears to be multifactor-
rial and further studies are needed to elucidate it.
As a result, the present case highlights the clinical
presentation of congenital unilateral hypoplasia of the
orbicularis oris muscle that causes asymmetric face.
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