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Diagnosis of Microcephaly

Microcephaly Diagnosis: Book Excerpts

• Differential Diagnosis - Microcephaly
• Clinical Features and Diagnosis - Microcephaly

Diagnostic Tests for Microcephaly: Online Medical Books

16 MEDICAL BOOKS ONLINE! Review excerpts from medical books online, free, without registration, for more information about diagnostis of Microcephaly.

Microcephaly: Differential Diagnosis
(In A Page: Pediatric Signs and Symptoms)

• Benign familial
• Hypoxic ishemic encephalopathy
• Intrauterine infection (TORCH)
• Teratogens
  –Ethanol
  –Cocaine
  –Isotretinoin
  –Phenytoin
• Down syndrome
• Trisomy 13
• Trisomy 18
• Lissencephaly
• Holoprosencephaly
• Anencephaly
• Porencephaly
• Intrauterine stroke
• Malnutrition
  –Typically preceded by decreased weight and height velocities
• Growth hormone deficiency
• Thyroid hormone deficiency
• Panhypopituitary
• Chromosomal deletions
• Smith-Lemli-Opitz syndrome (SLO)
• Menkes syndrome (kinky hair disease)
• Neuronal ceroid-lipofuscinosis
• Rett syndrome
  –Normal head circumference at birth
  –Acquired microcephaly after 6 months
• Incontinentia pigmenti
• Alper disease
• Phenylketonuria (PKU)
• Pelizaeus-Merzbacher
• Cri-du-chat syndrome
• Cornelia de Lange syndrome

Workup and Diagnosis

• Confirm and plot head circumference (HC)
• History
  –Signs of neurologic dysfunction
  –Developmental delay, paroxysmal movements
  –Early hand preference
  –Prenatal/birth history (gestational age, weight, HC)
  –Family history of microcephaly

• Physical exam
  –Measure parents’ HC and plot it on the chart
  –Obtain previous HC measurements
  –Deceleration of head growth is a more ominous sign than stably growing small head
  –Plot weight and height; hormonal deficiency and malnutrition affect these parameters as well as HC
  –Skin, eye (looking for TORCH, chorioretinitis infections), dysmorphic features, fontanelle size, hepatosplenomegaly
  –Neurological and developmental assessment (differential diagnosis is dependent on normal vs. delayed)

• Labs
  –TORCH titers, thyroid/GH levels, LFT
  –Chromosomes, 7-dehydrocholesterol (high in SLO)
  –Genetic testing for MECP-2, proteolipid protein
  –Amino acids, copper (low in Menkes)
• Neuroimaging
  –MRI is essential in diagnosis of structural abnormalities of the microcephalic brain

» READ BOOK EXCERPT ONLINE »

Source: In A Page: Pediatric Signs and Symptoms, 2007

Microcephaly: Clinical Features and Diagnosis
(The Diagnostic Approach to Symptoms and Signs in Pediatrics)

Normal Variation

Some normal infants have small head sizethat is proportional to their weight and height. This is often seenin preterm infants who never experience catch-up growth.

Primary Microcephaly

Small head size that occurs because brainis small and never developed properly due to genetic and embryologicdisturbances.

Microcephaly Vera (Genetic)

Mainly transmittedas autosomal-recessive trait. Gene locus has been mapped to chromosome8.

Characteristic findings include foreheadthat slants backward, prominent ears and nose, small chin, spasticdiplegia, seizures, and mental deficiency.

Brain imaging is normal.

Chromosomal Disorders

Small headsize is frequent finding in trisomies 13 and 18, deletion syndromes(3p, 4p, 5p, 11q, 13q, 18p, 18 q), and duplication syndromes (4p,10q).

In these disorders, children are dysmorphicand have other associated findings. Chromosomal karyotype confirmsdiagnosis.

See Jones (1997) for description ofthese syndromes.

Dysmorphic Syndromes with Normal Karyotype

Small headsize occurs in some syndromes in which gene loci have been mapped. Theseinclude Angelman, Bloom, Cockayne, Rubenstein-Taybi, Seckel, Smith-Lemli-Opitz,and Williams syndromes.

Small head size also exists in othersyndromes in which the gene loci have not been mapped. These areCornelia de Lange, DeSanctis-Cacchione, and Dubowitz syndromes.

See Jones (1997) for description ofthese syndromes.

Structural Defects in Brain Development

Defects described in this section are associatedwith microcephaly and may be diagnosed by MRI.

Disorders of Neuronal Migration

Polymicrogyria

Characterizedby excessive number of abnormally developed gyri.

Clinical findings depend on locationand extent of lesion.

Involvement of entire cortex may producesmall head, severe psychomotor retardation, and seizures.

Abnormal development and bilateralspasticity occur with bilateral focal lesions, whereas focal motorseizures and hemiparesis occur with unilateral focal involvement.

Lissencephaly

Lissencephaly(smooth brain) is absence of gyri and sulci or reduced number ofgyri with normal or shallow sulci.

Frequent findings include hypotonia,severe motor delay, and seizures.

Schizencephaly

Malformationin which abnormal clefts extend from cortical surface of brain toventricles.

Clinical findings depend on locationand extent of lesion; however, seizures and severe psychomotor retardationusually occur.

Holoprosencephaly

Spectrumof malformations that result from defective cleavage of forebrainsuch that cerebral hemispheres fail to separate.

In most severe form, microcephaly usuallyoccurs along with seizures, apneic episodes, severe psychomotorretardation, and occasionally, midline facial anomalies.

Agenesis of Corpus Callosum

Absenceof commissural fibers that bridge cerebral hemispheres.

Can be asymptomatic isolated findingor associated with other malformations of brain.

Seizures and mental retardation arecommon associated findings.

Macrogyria

Presenceof abnormally small number of large gyri.

Besides microcephaly, seizures andmental retardation usually occur.

Secondary Microcephaly

In this circumstance brain develops normally,until some process impairs its growth.

Maternal Disorders and Exposures

Maternal Phenylketonuria

Exposureof fetus to high phenylalanine levels from mother with phenylketonuria mayproduce certain abnormalities: microcephaly, round facies with prominentglabella, decreased weight and length, congenital heart defects,and mental retardation.

Any woman with mental retardation ofunknown cause should be screened for phenylketonuria.

Drug or Poison Ingestion

Fetal Alcohol Syndrome

Occurs inmany infants whose mothers are chronic alcoholics.

Characteristic findings include microcephaly;facies with short palpebral fissures, maxillary hypoplasia, shortnose, and smooth philtrum with thin upper lip; cleft lip and palate;small distal phalanges with small fifth fingernail; congenital heartdisease (ventricular septal defect or atrial septal defect); prenataland postnatal growth deficiency; and mental retardation.

Fetal Hydantoin Syndrome

Microcephalyis occasionally seen following maternal hydantoin intake duringpregnancy.

Characteristic findings include facieswith wide nasal bridge, hypertelorism, short nose, and bowed upperlip; cleft lip and palate; wide anterior fontanelle; small distalphalanges with hypoplastic nails; poor growth that is usually prenatal;and mental retardation.

Other Ingestions

Cocaine abuse and use of solvents (e.g.,toluene) also have been associated with microcephaly.

Malnutrition (Fetal and Early Infancy)

With severe malnutrition during pregnancyor early infancy, brain fails to grow normally and microcephalyoccurs.

Hypoxic-Ischemic Encephalopathy

May cause destruction of brain tissue withsubsequent atrophy and areas of cystic degeneration. CT or MRI isdiagnostic.

Infection

Microcephalymay occur with congenital infections (e.g., rubella, herpes simplex,cytomegalovirus, toxoplasmosis, and syphilis).

Bacterial meningitis also may causebrain atrophy and small head size.

See Chap.3, Alteration in Consciousness, and Chap. 36, Jaundice.

Craniosynostosis

Primarydisorder of skull in which premature fusion of cranial sutures impairsbrain growth.

Shape of head is abnormal.

Skull radiographs and CT are diagnostic.

Diagnostic Approach

Measurehead circumference, weight, and height at each well-child visitusing growth charts published by the CDC (2001).

If these measurementsare proportional, child most likely is small in size and does not haveprimary abnormality in brain growth.

Head circumference that is proportionallysmaller than weight and length usually signifies primary decreasein brain growth or secondary process (e.g., hypoxic-ischemic encephalopathyor infection).

History of microcephaly in family memberssuggests genetic disorder, which is important for genetic counseling.

History of maternal drug or alcoholingestion, maternal phenylketonuria, or other disorders should beclarified.

Presence of dysmorphic features suggestschromosomal or malformation syndrome, and chromosomal karyotypeshould be determined.

Skull radiographs help diagnose craniosynostosis.CT and MRI can diagnose structural defects in brain development.

Presence of other findings helps diagnosevarious infections.

» READ BOOK EXCERPT ONLINE »

Source: The Diagnostic Approach to Symptoms and Signs in Pediatrics, 2006

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