++
Congenital ptosis usually results from underdevelopment of the
eyelid levator muscle. The condition may be bilateral or unilateral and
may be isolated or associated with other ocular or systemic disorders.
Unilateral ptosis is more likely to be isolated. Bilateral ptosis is
more likely to be associated with other problems. Etiologies for
bilateral ptosis include familial (usually autosomal dominant), chromosomal
(eg, Turner syndrome), teratogenic (eg, fetal alcohol syndrome),
and syndromic. Both bilateral and unilateral ptosis also frequently
occur in otherwise normal children, in which case there is often
no identifiable causative factor.
++
Ptosis presents with the upper eyelid resting in a lower position
than normal on the eye. It may range from mild, with the eyelid
1 to 2 mm lower than normal, to severe, in which case the eyelid may
cover the whole cornea. In congenital ptosis, the eyelid crease
is usually absent, because the crease normally forms from fibers
of the levator muscle (which is hypoplastic in these patients) attaching
to the eyelid skin. The residual levator muscle in ptosis is also
usually stiff, which may limit full closure of the lid.
++
In rare instances, children may have pseudoptosis. In this condition,
the eye with the lower eyelid initially appears to be abnormal,
but the asymmetry is actually due to proptosis (anterior displacement)
of the contralateral eye, where the upper eyelid is somewhat retracted.
++
Approximately 5% of children with congenital ptosis
have the Marcus-Gunn jaw-winking phenomenon. In this condition,
the fibers that innervate the levator muscle are aberrantly connected
to fibers that innervate the masseter muscle. This produces a synketic
elevation of the eyelid during jaw movements. In infants, this is usually
noted while they suck during feeding, and in older children, it
can be seen by asking the child to move the jaw laterally. This
usually manifests as a baseline ptosis with intermittent elevation
or even retraction during jaw movements, but it may also manifest
as a baseline normal eyelid position, with intermittent widening of
the palpebral opening during jaw movement.
++
The primary visual problem associated with ptosis is amblyopia,
which may occur for two reasons.2 First, if the
eyelid margin rests at or below the pupil, it may interfere with
vision. In unilateral cases, this may cause the child to favor the
normal eye. Second, the mechanical weight of the eyelid may induce astigmatism
(asymmetric curvature) of the cornea, creating a blur that also
causes the child to favor the opposite eye. In mild cases (1 to
2 mm), ptosis usually does not produce any visual or appearance problems.
In moderate cases (the ptotic lid is 3 to 5 mm below normal level),
children will often adapt compensatory strategies to improve their
vision. Once affected infants have adequate neck control, they often
tilt their head back in order to look beneath the droopy eyelid
(chin lift). In addition, children will often attempt to use the
frontalis muscle to assist in lifting the eyelid, producing contraction
of this muscle and, in unilateral cases, asymmetric elevation of
the eyebrows (Fig. 589-1). In severe cases,
in which the lid covers most of the cornea, there is a great risk
of deprivation amblyopia, which may be irreversible if the ptosis
is not corrected early.
++
++
Treatment of ptosis involves surgical elevation of the eyelids.
Amblyopia treatment with patching and glasses for astigmatism is
also often necessary. Severe ptosis needs to be corrected within
the first few months of life due to the risk of amblyopia. Timing
of surgery for moderate ptosis depends on the presence of amblyopia and
compensatory head postures. If these are present, early surgery
is indicated. If not, surgery is often delayed until age 4 to 5
years. Children with mild ptosis often do not require surgery.
++
Compared to the incidence of congenital ptosis, acquired ptosis
is relatively uncommon in children, and the differential diagnosis
is large. Acquired ptosis rarely presents as an isolated phenomenon,
and an etiology can often be identified by the history and associated
findings. Possible etiologies include myogenic, neurogenic, inflammatory,
infectious, and mass lesions.
++
Myasthenia gravis is a myogenic disorder that results from antibodies
directed against acetylcholine receptors, which may initially present
with ptosis.3 This can occur in the neonatal period
and should be considered in the differential diagnosis of congenital
ptosis, but it more commonly presents at an older age. Historical
features that suggest this diagnosis include worsening of the symptoms
with fatigue and intermittent diplopia (due to involvement of the
extraocular muscles). Diagnostic tests include electromyography
and serum anticholinesterase antibodies, and administration of edrophonium
or neostigmine can improve symptoms.
++
Another myogenic disorder that may initially present with ptosis
is chronic progressive external ophthalmoplegia (CPEO). This is
usually due to mitochondrial dysfunction that affects the levator
and extraocular muscles. Sporadic and inherited forms occur, and
the ocular findings of CPEO may be seen in several diseases associated
with mitochondrial dysfunction. One of these is Kearns-Sayre syndrome, which
is associated with CPEO, pigmentary retinopathy, and cardiac conduction
abnormalities. Children with CPEO should be evaluated by a cardiologist.
++
Neurogenic causes of ptosis include third cranial nerve palsy
and Horner syndrome. The third cranial nerve innervates the eyelid
levator muscle, four of the six extraocular muscles, and the iris
muscles that constrict the pupil. In a complete third nerve palsy,
the eyelid is ptotic, the eye is turned out and down (because the
only residual functioning extraocular muscles are the lateral rectus
muscle, which pulls the eye out, and the superior oblique muscle,
which pulls the eye down), and the pupil is dilated (Fig.
589-2). In certain conditions, only the superior division of
the third nerve is involved, in which case only innervation of the
eyelid and superior rectus muscle are involved, producing ptosis
and downward deviation of the eye.
++
++
Horner syndrome (Fig. 589-3) results from
interruption of the sympathetic pathway between the hypothalamus
and the eye. Patients usually present with mild to moderate ptosis
due to decreased innervation of Mueller’s muscle (an accessory
eyelid-elevating muscle). Anisocoria (unequal pupils) is also present,
with the pupil smaller on the affected side (due to decreased innervation
to the pupil-dilating muscles in the iris). There may also be “upside-down
ptosis” of the lower lid: a higher position of the lower
lid due to a deficiency of its sympathetic innervation. Some patients
may have decreased periocular sweating on the affected side, and patients
with congenital Horner syndrome may have unequal pupil color (heterochromia).
++
++
Horner syndrome usually does not produce problems with vision.
Its primary importance lies in identifying an underlying cause.
The pathway for the series of neurons that are responsible for Horner
syndrome begins in the hypothalamus, travels through the spinal
cord to the thoracic vertebrae, ascends over the apex of the lung
and along the internal carotic artery, and through the orbital apex
to the eyelid and iris-dilating muscles. Horner syndrome in infants
may be caused by torsion of the neck during a difficult delivery,
but it is usually idiopathic and typically benign. Acquired Horner
syndrome may be seen in patients who have had damage to the pathway
following central line placement in the neck. Neuroblastoma is an
important potential cause of acquired Horner syndrome. If an underlying
cause is not apparent, evaluation includes magnetic resonance imaging
studies of the abdomen (looking for tumors in the adrenal area),
chest, neck, and head, and urine tests for vanillylmandelic acid.4
++
The remaining differential diagnosis for acquired ptosis is long
and includes trauma (either direct trauma to the levator muscle or
damage to the third cranial nerve), mass effects (including orbital
tumors and vascular malformations), inflammation (of either the
eyelid, levator muscle, or orbit), and infection.