Microencephaly

Overview

Microcephaly is a neurodevelopmental disorder. It serves as an important neurological indication or warning sign, but no uniformity exists in its definition. It is usually defined as a head circumference (HC) more than two standard deviations below the mean for age and sex. Some academics advocate defining it as head circumference more than three standard deviations below the mean for the age and sex. Microcephaly may be congenital or it may develop in the first few years of life. The disorder may stem from a wide variety of conditions that cause abnormal growth of the brain, or from syndromes associated with chromosomal abnormalities. A homozygous mutation in one of the microcephalin genes causes primary microcephaly.

In general, life expectancy for individuals with microcephaly is reduced and the prognosis for normal brain function is poor. The prognosis varies depending on the presence of associated abnormalities.

Symptoms

The list of signs and symptoms mentioned in various sources for Microencephaly includes the 15 symptoms listed below:

  • Small brain
  • Small head
  • Mental retardation
  • Developmental delay
  • Epilepsy
  • Cerebral palsy
  • Impaired vision
  • Feeding difficulty
  • Delayed speech development
  • Delayed motor development
  • Asymptomatic
  • Hyperactivity
  • Convulsions
  • Clumsiness
  • Spastic quadriplegia

Note that Microencephaly symptoms usually refers to various symptoms known to a patient, but the phrase Microencephaly signs may refer to those signs only noticable by a doctor.

Causes

Microcephaly is a type of cephalic disorder. It has been classified in two types based on the onset:

Congenital

Isolated

  1. Familial (autosomal recessive) microcephaly
  2. Autosomal dominant microcephaly
  3. X-linked microcephaly
  4. Chromosomal (balanced rearrangements and ring chromosome)

Syndromes

  • Chromosomal
  1. Poland syndrome
  2. Down syndrome
  3. Edward syndrome
  4. Patau syndrome
  5. Unbalanced rearrangements
  • Contiguous gene deletion
  1. 4p deletion (Wolf–Hirschhorn syndrome)
  2. 5p deletion (Cri-du-chat)
  3. 7q11.23 deletion (Williams syndrome)
  4. 22q11 deletion (DiGeorge syndrome)
  • Single gene defects
  1. Smith–Lemli–Opitz syndrome
  2. Seckel syndrome
  3. Cornelia de Lange syndrome
  4. Holoprosencephaly
  5. Primary microcephaly 4

Acquired

  • Disruptive injuries
  1. Ischemic stroke
  2. Hemorrhagic stroke
  3. Death of a monozygotic twin
  • Vertically transmitted infections
  1. Congenital cytomegalovirus infection
  2. Toxoplasmosis
  3. Congenital rubella syndrome
  4. Zika virus is a suspected cause
  • Drugs
  1. Fetal hydantoin syndrome
  2. Fetal alcohol syndrome

Other

  1. Radiation exposure to mother
  2. Maternal malnutrition
  3. Maternal phenylketonuria
  4. Poorly controlled gestational diabetes
  5. Hyperthermia
  6. Maternal hypothyroidism
  7. Placental insufficiency


Diagnosis

The signs and symptom information on this page attempts to provide a list of some possible signs and symptoms of Microencephaly. This medical information about signs and symptoms for Microencephaly has been gathered from various sources, may not be fully accurate, and may not be the full list of Microencephaly signs or Microencephaly symptoms. Furthermore, signs and symptoms of Microencephaly may vary on an individual basis for each patient. Only your doctor can provide adequate diagnosis of any signs or symptoms and whether they are indeed Microencephaly symptoms.

Prognosis

Generally, no specific cure is known for microcephaly. Treatment is symptomatic and supportive.