Strabismus - Fundamentals of Clinical Ophthalmology.pdf

CHILDHOOD ONSET OF STRABISMUS
Spasmus nutans
This condition is characterised by nodding
spasms which are self-limiting. It was originally
regarded as a benign condition characterised by
asymmetric acquired pendular nystagmus, head
nodding and head tilt. There is a typical age of
onset with nystagmus preceding head nodding at
between 4–12 months. What is important is that
there are no reliable diagnostic clues to
differentiate spasmus nutans from acquired
pendular nystagmus and intracranial tumours,
including chiasmal gliomas.
Congenital retraction nystagmus
Attempts to look up are associated with
eyeball retraction. The movement is thought to
be due to opposed saccades. Clinically there may
be associated dorsal midbrain lesions which
may be intrinsic, for example Parinaud syndrome,
or extrinsic, for example hydrocephalus.
Ocular motor apraxia
Harris introduced the term saccade initiation
failure (SIF). Strabismus is common (see
Figure 4.24). SIF is intermittent, often more
noticeable when the child is stressed or tired. In
congenital SIF, the saccades when they occur
have normal speeds. Head thrusting (see glossary
for definition) may not develop until 2–3 months.
Shifting gaze with the head may also compensate
for gaze palsy, hemianopia, slow saccades or
even poor eccentric gaze holding. Older children
facilitate the triggering of saccades by blinking
synkinetically. Apart from agenesis of the corpus
callosum most structural abnormalities associated
with SIF occur in the posterior fossa, around the
fourth ventricle and vermis (Figure 4.25). MRI is
preferred. There is no treatment for SIF. Visual
outcome is good, although delayed speech and
poor reading as well as clumsiness and educational
problems may be apparent later in development.
Periodic alternating nystagmus
Periodic alternating nystagmus is seen as a
congenital nystagmus. It is characterised by
repeated cycles of nystagmus alternating in the
direction of beating punctuated by a pause in the
movement disorder. It is important to exclude
posterior fossa neurologic disease and to be
aware of the association with Arnold–Chiari
malformation, congenital hydrocephalus, and
myelomeningocele.
References
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