Congenital malformations - Edocr

CHAPTER 11 AGENESIS OF THE CORPUS CALLOSUM 81
these are listed in Table 11-1. There are many
other multiple malformation syndromes, not
listed in the table, in which agenesis of the corpus
callosum can be an occasional feature.
Therefore, consultation with a clinical geneticist
is recommended in complex cases.
EVALUATION
The following studies should be obtained on
any infant with agenesis of the corpus callosum:
1. MRI of the brain—to confirm the presence
of the defect and to detect and define any
associated CNS malformations
2. Careful physical examination to identify any
associated major or minor birth defects or
dysmorphic features
3. Ophthalmologic examination—this is particularly
important in female infants to look
for the chorioretinal lacunae seen in Aicardi
syndrome
4. Blood chromosome analysis
5. Ultrasound evaluation of the urinary tract
6. Echocardiogram
MANAGEMENT AND PROGNOSIS
The treatment for infants with agenesis of the
corpus callosum is directed at any associated
anomalies for which treatment may be indicated.
Similarly, the prognosis is dependent on
the overall diagnosis and on the prognosis for
that condition or, if there is no specific diagnosis
established, the prognosis for the anomalies
identified. The outcome is generally not favorable
for symptomatic patients who have neurologic
abnormalities in early infancy. Of all patients with
agenesis of the corpus callosum, mental retardation
of some degree is found in approximately
83%. 8,9 About half of all patients develop seizures
and over a third have findings consistent with
cerebral palsy. 9 Factors predictive of a poor outcome
include microcephaly or findings of cerebral
dysgenesis on MRI.
GENETIC COUNSELING
Genetic counseling for families of patients with
agenesis of the corpus callosum is dependent on
the underlying diagnosis. If a diagnosis cannot
be established and the patient has multiple malformations,
a clinical geneticist should be consulted
since there are many single gene disorders
in which agenesis of the corpus callosum can be
an occasional feature. Some of these can be inherited
in an autosomal recessive or autosomal
dominant pattern so a specific diagnosis would
be important prior to future family planning.
If the patient has isolated agenesis of the corpus
callosum with no evidence of a metabolic
disorder, then counseling can be provided in the
postnatal setting. The prognosis may be good
for the infant once associated anomalies have
been ruled out and there is room for cautious
optimism. This reassurance can only be given
postnatally, however, and only after a thorough
evaluation since some of the syndromes most
commonly associated with agenesis of the corpus
callosum, like Aicardi syndrome, would not
be expected to be associated with any additional
findings on prenatal ultrasonography. Parents of
an asymptomatic normal infant are rarely too
concerned about recurrence risks except for the
fact that they may again be confronted by abnormal
ultrasound findings should they have a
recurrence. Since familial cases have been reported,
recurrence risks are higher than those
faced by couples in the general population. Empiric
recurrence risk data are not available; an
estimated risk of 5% would seem reasonable.
REFERENCES
1. Hunter, Alaidair GW. Agenesis of the corpus callosum,
In: RE Stevenson and JG Hall, eds. Human
Malformations and Related Anomalies. 2nd ed.
New York: Oxford University Press; 2006:581–604.
2. Chacko A, Koul R, Sankhla DK. Corpus callosum
agenesis. Saudi Med J. 2001;22:22–5.
3. Bookstein FL, Sampson PD, Connor PD, et al. Midline
corpus callosum is a neuroanatomical focus of
fetal alcohol damage. Anat Rec. 2002;269:162–74.