Microcephaly: Clinical Case Discussion & Key Points
Model Case Presentation
Patient Demographics
Name: Master Arjun, Age: 18 months, Gender: Male, Informant: Mother (Reliable)
Chief Complaints
- Small head size noted since birth
- Delayed developmental milestones – noticed from 6 months
- Poor speech – not speaking any words at 18 months
History Summary
Mother noticed that the baby's head was smaller than his older sibling's at the same age. He sat with support at 10 months, cannot stand independently. No meaningful words. He follows people with eyes and smiles socially. No history of seizures. No regression of milestones. History of consanguineous marriage (first-cousin parents). No antenatal infections, no teratogen exposure, no alcohol. Born at term, birth weight 2.6 kg. Mother recalls head was noted to be "small" at birth by the nurse. Antenatal period was uneventful. No family history of similar illness.
Examination Summary
| Parameter | Finding | Significance |
|---|---|---|
| Head Circumference (HC) | 40 cm | −3.5 SD below mean for age/sex (severe microcephaly) |
| Weight | 9 kg | ~10th percentile (relatively preserved) |
| Height | 78 cm | Normal for age |
| Fontanelle | Closed (premature) | Reduced brain growth |
| Forehead | Narrow, sloping | Characteristic of primary microcephaly |
| Development | Gross motor: 8 months level; Fine motor/language: 6 months level | Global developmental delay |
| Cranial Nerves | Intact | — |
| Tone/Power | Normal tone, no spasticity | Against cerebral palsy |
| Fundus | Normal (no chorioretinitis) | Against TORCH |
| Dysmorphic features | Absent (isolated microcephaly) | — |
Scalp: Loose, redundant scalp skin (characteristic). Prominent occiput is absent (unlike posterior plagiocephaly).
Systemic examination: No hepatosplenomegaly, no rash, no lymphadenopathy. Normal cardiovascular and respiratory examination.
✅ Complete Diagnosis
Primary (Congenital) Microcephaly — Likely Autosomal Recessive Primary Microcephaly (MCPH / Microcephaly Vera) — with Global Developmental Delay and Intellectual Disability. (Given consanguineous parents, isolated microcephaly, sloping forehead, no structural brain or systemic anomalies.)
💡 How to Measure Head Circumference
Use a non-stretchable tape. Measure the Occipitofrontal Circumference (OFC): tape passes just above the supraorbital ridges anteriorly and over the most prominent part of the occiput posteriorly. Always take the maximum measurement after 2–3 attempts. Plot on gender-specific growth chart (WHO or IAP).
📝 History — Exam Q&A
Microcephaly is defined as an Occipitofrontal head Circumference (OFC) more than 2 Standard Deviations (SD) below the mean for age and sex.
- Microcephaly: OFC < −2 SD
- Severe/True microcephaly: OFC < −3 SD (also called microcephaly vera)
Microcephaly is a clinical sign, not a diagnosis — it indicates reduced brain volume (microencephaly) and has multiple etiologies.
| Age | Normal HC (Approximate Mean) |
|---|---|
| At birth (term) | 34 cm (range 32–37 cm) |
| 3 months | 40 cm |
| 6 months | 43 cm |
| 1 year | 46–47 cm |
| 2 years | 48–49 cm |
| Adult | ~55 cm (female) / ~57 cm (male) |
Rate of growth: HC grows ~2 cm/month for first 3 months, ~1 cm/month from 3–6 months, ~0.5 cm/month from 6–12 months.
By Timing of Onset:
| Type | Definition | Implication |
|---|---|---|
| Primary (Congenital) | Present at birth — HC small from birth | Failure of neurogenesis during fetal life |
| Secondary (Acquired/Postnatal) | Normal HC at birth; fails to grow normally thereafter | Postnatal brain injury (HIE, infection, metabolic) |
By Proportionality:
- Proportionate (Symmetric): HC small but proportionate to weight and length — often familial or genetic
- Disproportionate (Asymmetric): HC small but weight and length are relatively normal — more likely pathological
By Etiology: Primary/Genetic vs. Secondary/Environmental (see next question).
A. Primary (Genetic) Causes:
- Autosomal Recessive Primary Microcephaly (MCPH/Microcephaly vera) — mutations in MCPH1–MCPH12 genes; most commonly ASPM gene (MCPH5)
- Chromosomal: Down syndrome (Trisomy 21), Cri-du-chat (5p−), Trisomy 13, 18
- Syndromes: Cornelia de Lange, Angelman, Rett, Rubinstein-Taybi, Smith-Lemli-Opitz, Seckel syndrome
- Craniosynostosis (premature fusion of sutures)
B. Environmental / Acquired Causes:
- Intrauterine infections (TORCH): CMV (most common congenital infection causing microcephaly), Toxoplasma, Rubella, Herpes, Zika virus, Syphilis, Varicella
- Teratogens: Alcohol (Fetal Alcohol Syndrome), Valproic acid, Thalidomide, Phenytoin, Maternal PKU
- Radiation: Especially 8–15 weeks gestation (most sensitive period)
- Perinatal insults: Hypoxic-Ischemic Encephalopathy (HIE), severe neonatal hyperbilirubinemia
- Postnatal: Meningitis/encephalitis, severe malnutrition (marasmus), metabolic disorders (PKU, maple syrup urine disease)
- Familial/Normal variant: Familial small head with normal intellect
💡 Mnemonic: TORCH-Z causes congenital microcephaly
Toxoplasma, Other (Syphilis, VZV, Parvovirus), Rubella, CMV (most common), Herpes, Zika (emerging)
1. About the head:
- Was HC noted to be small at birth? (Primary vs. Secondary)
- HC measurement and plot — is it progressive or static?
- Parents' head size? (Familial microcephaly)
2. Antenatal history:
- Maternal infections — fever, rash, lymphadenopathy during pregnancy?
- Maternal alcohol, drugs, anticonvulsants?
- Maternal diabetes or PKU?
- Radiation exposure?
- Consanguinity? (Autosomal recessive causes)
- Prenatal USG — when was microcephaly first detected?
3. Birth history:
- Term or preterm? Birth weight?
- Perinatal asphyxia (HIE)? NICU admission?
- Neonatal seizures, jaundice, infection?
4. Developmental history:
- All 4 domains: gross motor, fine motor, speech/language, social
- Any regression of milestones? (Suggests neurodegenerative disorder)
5. Seizure history: Type, frequency, treatment
6. Family history: Siblings with microcephaly, intellectual disability, or consanguinity
Familial microcephaly (also called "relative microcephaly" or "benign familial microcephaly") occurs when a child has a small head that is proportionate to the parents' small heads, with normal intelligence and development.
| Feature | Familial/Benign Microcephaly | Pathological Microcephaly |
|---|---|---|
| Intellect | Normal | Impaired (usually) |
| Development | Normal milestones | Delayed |
| Parental HC | Small (one or both parents) | Normal |
| Severity | Usually −2 to −3 SD | Often < −3 SD |
| Other features | None | May have seizures, dysmorphism, TORCH stigmata |
Always measure parents' head circumference in the assessment of a child with microcephaly.
Microcephaly Vera (True/Primary hereditary microcephaly — MCPH) is an autosomal recessive condition characterized by:
- HC < −3 SD at birth, worsening to −4 to −12 SD in adulthood
- Mild to moderate non-progressive intellectual disability
- Narrow, sloping forehead
- Redundant scalp skin
- Normal brain architecture (mildly simplified gyral pattern on MRI)
- No other systemic anomalies (isolated microcephaly)
Genetics: At least 12 genetic loci (MCPH1–MCPH12). Most commonly caused by mutations in ASPM gene (MCPH5) — accounting for ~40–50% of cases. WDR62 (MCPH2) is second most common.
Associated with consanguinity. Common in Pakistani, Arab, and Indian populations.
Cytomegalovirus (CMV) is the most common congenital infection causing microcephaly. It affects 0.5–1% of live births in developed countries (up to 6% in developing countries). Associated features include:
- Periventricular calcifications (pathognomonic)
- Sensorineural hearing loss
- Chorioretinitis
- Hepatosplenomegaly, jaundice, petechiae
- Intellectual disability, cerebral palsy
Gold standard diagnosis: CMV urine PCR within 3 weeks of birth (after 3 weeks, cannot distinguish congenital from acquired).
The most sensitive period for radiation-induced microcephaly is 8–15 weeks of gestation, which corresponds to the period of maximal neuronal proliferation and migration. This was demonstrated by survivors near the epicenter of atomic bomb explosions at Hiroshima and Nagasaki (1945). Exposure after 25 weeks carries minimal risk of microcephaly.
🩺 Examination — Exam Q&A
- Use a non-stretchable (non-elastic) tape measure
- Position: Tape passes just above the eyebrows (supraorbital ridges) anteriorly and over the most prominent part of the occiput posteriorly
- Take 3 measurements and record the largest value
- Plot on gender-specific, age-appropriate growth chart (WHO or IAP)
- Always measure parental head circumferences for comparison
Note: Biparietal Diameter (BPD) on antenatal USG is less reliable for diagnosing microcephaly than HC (OFC).
- Small head — markedly reduced OFC (often < −3 SD)
- Narrow, sloping forehead — the cranial vault appears disproportionately small relative to the face
- Prominent occiput/ears — relatively, because the vault is small
- Redundant (loose) scalp skin — unused scalp folds
- Face appears large compared to the skull (face continues normal development)
- Fontanelle: Anterior fontanelle may be small or closed prematurely
- Sutures may be overriding or fused early
| Feature | True Microcephaly (Microencephaly) | Craniosynostosis |
|---|---|---|
| Cause | Reduced brain volume → small skull | Premature suture fusion → restricts skull growth |
| Brain size | Small (primary pathology) | Normal initially (brain is constrained) |
| Head shape | Symmetric, round (normal shape) | Abnormal — depends on suture fused (scaphocephaly, brachycephaly, plagiocephaly, trigonocephaly) |
| Sutures | Open (or close normally) | Fused prematurely — firm ridge palpable |
| Fontanelle | Normal or small | Small or absent at fused suture |
| Raised ICP | No | May be present (bulging fontanelle, papilledema) |
| Intelligence | Usually impaired | Normal (if treated early) |
| Treatment | Supportive/rehabilitation | Surgical (craniectomy/remodeling) |
💡 Key Pearl
In craniosynostosis, there is a palpable bony ridge along the fused suture. CT skull (3D) confirms it. Surgery is the only option.
- Hepatosplenomegaly — all TORCH infections
- Jaundice — CMV, Rubella, Toxoplasma
- Petechiae / purpuric rash — CMV (blueberry muffin rash), Rubella
- Chorioretinitis — CMV, Toxoplasma (salt-and-pepper fundus), Rubella, Herpes
- Cataracts — Rubella (also glaucoma)
- Sensorineural hearing loss — CMV (most common), Rubella
- Congenital heart defects — Rubella (PDA, peripheral PS)
- Intracranial calcifications — CMV (periventricular), Toxoplasma (diffuse/scattered)
- Skin vesicles — Herpes simplex
- Low birth weight, SGA — any TORCH
💡 Calcification Pattern
CMV: Periventricular (lining the ventricles) — "eggshell" pattern. Toxoplasma: Diffuse/basal ganglia calcifications. Different pattern on CT/skull X-ray!
Most children with pathological microcephaly have global developmental delay (GDD) and eventual intellectual disability (ID). The severity correlates broadly with the degree of microcephaly:
- Mild microcephaly (−2 to −3 SD): Mild-moderate ID
- Severe microcephaly (< −3 SD): Moderate-severe ID
Domains typically affected: Speech/language (most severely), fine motor, gross motor, adaptive/social. Social milestones may be relatively preserved in primary MCPH.
Regression of milestones suggests a progressive/degenerative condition (e.g., Rett syndrome, metabolic disorders) — these require urgent workup.
| Syndrome | Key Associated Features |
|---|---|
| Down Syndrome (Trisomy 21) | Upslanting palpebral fissures, single palmar crease, sandal gap, hypotonia, CHD (AVSD/VSD), Brushfield spots |
| Cornelia de Lange Syndrome | Synophrys (joined eyebrows), thin upper lip, limb anomalies, short stature, growth retardation |
| Rubinstein-Taybi Syndrome | Broad thumbs and toes, beaked nose, downslanting palpebral fissures |
| Seckel Syndrome | Extreme short stature, "bird-headed" facies, prominent nose, no intellectual disability |
| Angelman Syndrome | Happy demeanor, frequent laughter, seizures, absent speech, wide-based gait |
| Rett Syndrome | Girls only, loss of purposeful hand use, hand-wringing stereotypies, acquired microcephaly (normal at birth) |
| Fetal Alcohol Syndrome | Short palpebral fissures, smooth philtrum, thin upper lip, behavioral problems, maternal alcohol history |
- Seizures — in 10–50% (especially with TORCH, structural brain anomalies)
- Spasticity / increased tone — especially in secondary microcephaly (HIE, post-meningitis)
- Cerebral palsy — associated comorbidity
- Hyperreflexia — upper motor neuron involvement
- Hearing loss — sensorineural (especially CMV)
- Visual impairment — cortical visual impairment or chorioretinitis
- Feeding difficulties — due to oromotor dysfunction
Note: In pure MCPH (microcephaly vera), tone is usually normal, and there are no major neurological deficits other than intellectual disability.
🔬 Investigations — Exam Q&A
MRI Brain is the preferred first-line neuroimaging for microcephaly.
It can show:
- Simplified gyral pattern (MCPH)
- Lissencephaly (smooth brain, absent sulci and gyri)
- Pachygyria (thickened cortex with broad, shallow gyri)
- Polymicrogyria (many small, irregular gyri)
- Periventricular calcifications (CMV)
- Diffuse/basal ganglia calcifications (Toxoplasmosis)
- Cortical malformations, agenesis of corpus callosum, ventriculomegaly
- Porencephaly, hydranencephaly (post-ischemic/post-hemorrhagic)
- Cerebellar hypoplasia
💡 CT vs MRI
CT is preferred for detecting calcifications (TORCH). MRI is superior for cortical malformations, white matter, and structural detail. When calcifications are suspected, CT is done first; MRI follows for full characterization.
Step 1 — History-guided (clinical diagnosis first):
- Measure parental HC — if small parents with normal child intellect → familial microcephaly, no further workup needed
- Consanguinity + isolated microcephaly → suspect MCPH
- Antenatal infection exposure → TORCH screen
- Dysmorphic features → chromosomal/syndrome workup
- Postnatal onset → investigate for acquired cause
Step 2 — Targeted investigations:
- All cases: MRI Brain (preferred), EEG if seizures
- TORCH suspected: CMV urine PCR (within 3 weeks of birth is gold standard), TORCH serology (IgM/IgG), Rubella IgM, Toxoplasma IgM
- Chromosomal suspected: Karyotype, CMA (Chromosomal Microarray)
- Single gene/MCPH: Targeted gene panel or Whole Exome Sequencing (WES)
- Metabolic suspected: Urine organic acids, plasma amino acids, Tandem MS (newborn screening); Maternal serum phenylalanine (to exclude maternal PKU)
- Rett syndrome (girls): MECP2 gene testing
Step 3 — Developmental assessment: Formal neuropsychological/developmental evaluation — Bayley Scales, DASII, Vineland Adaptive Behavior Scales.
CMV urine PCR (or saliva PCR) within the first 21 days (3 weeks) of life is the gold standard for diagnosing congenital CMV.
- After 3 weeks, positive CMV PCR cannot distinguish congenital from postnatally acquired infection
- Saliva PCR is a convenient alternative (same sensitivity as urine)
- Serology (IgM/IgG) has poor sensitivity in neonates due to immature immune system
EEG findings depend on the underlying etiology:
- Hypsarrhythmia — chaotic, high-amplitude pattern seen in Infantile Spasms (West Syndrome), which can complicate any structural brain disease including microcephaly
- Suppression-burst pattern — early-onset epileptic encephalopathy, severe structural anomalies
- Multifocal spikes — polymicrogyria, cortical dysplasia
- Generalized spike-wave — various epilepsy syndromes complicating microcephaly
EEG is indicated in any microcephalic child with clinical or subclinical seizures.
Skull X-ray has limited utility and has largely been replaced by CT/MRI. However, it may show:
- Intracranial calcifications: visible in congenital toxoplasmosis and sometimes CMV (coarse, diffuse calcifications)
- Fused sutures with sclerotic ridges — craniosynostosis
- Small cranial vault with prominent facial bones
CT skull/brain is more sensitive for calcifications and is preferred over skull X-ray when infection or structural cause is suspected.
- Antenatal ultrasound: Head circumference (HC) < −2 SD on serial measurements; typically becomes apparent after 24–28 weeks (brain growth is most active in third trimester). BPD is less reliable; use HC.
- HC < −3 SD prenatal raises strong suspicion; HC < −5 SD is considered highly specific.
- Fetal MRI: Useful adjunct when USG shows microcephaly — provides better cortical detail, may identify lissencephaly, agenesis of corpus callosum, etc.
- TORCH serology and PCR on maternal blood or amniotic fluid if infection suspected.
- Amniocentesis for karyotype/chromosomal microarray if chromosomal cause suspected.
- Whole Exome Sequencing on amniotic fluid — emerging approach for family history of MCPH.
Note: A normal prenatal USG does NOT exclude microcephaly — many cases of primary microcephaly become apparent only in the third trimester or after birth.
💊 Management — Exam Q&A
There is no cure or treatment that restores normal brain or head size for primary microcephaly. Management is symptomatic, supportive, and habilitative.
Key Principles:
- Early intervention: Best outcomes with early developmental therapy
- Multidisciplinary team approach: Developmental Pediatrician, Neurologist, Geneticist, Physiotherapist, Occupational Therapist, Speech-Language Pathologist, Ophthalmologist, Audiologist, Psychologist, Social worker
- Treat treatable causes (e.g., congenital CMV with Valganciclovir, craniosynostosis with surgery)
- Manage complications — seizures, feeding difficulties, spasticity
- Physiotherapy (PT): Improve motor function, prevent contractures, improve sitting balance, gait training
- Occupational Therapy (OT): Fine motor skills, activities of daily living, adaptive equipment
- Speech and Language Therapy (SLT): Improve communication, oromotor feeding skills; AAC (Augmentative and Alternative Communication) devices if needed
- Special education: Individualized Education Program (IEP) — structured schooling tailored to cognitive level
- Seizure management: Anti-epileptic drugs based on seizure type (Valproate, Levetiracetam, Clonazepam, ACTH/Vigabatrin for Infantile Spasms)
- Nutritional support: High-calorie feeds, NG tube/PEG if feeding is poor
- Sensory aids: Hearing aids for hearing loss; glasses/low vision aids for visual impairment
- Spasticity management: Oral Baclofen, Botulinum toxin injections, intrathecal Baclofen (for severe cases)
Valganciclovir (oral — preferred) or Ganciclovir (IV) is the antiviral treatment for symptomatic congenital CMV.
Indications (symptomatic congenital CMV with any of):
- CNS involvement — microcephaly, seizures, intracranial calcifications, ventriculomegaly
- Sensorineural hearing loss
- Thrombocytopenia, hepatitis, chorioretinitis
Dose: Valganciclovir 16 mg/kg/dose twice daily for 6 months
Benefit: Reduces progression of hearing loss and improves neurodevelopmental outcomes when started early (within first month of life ideally).
Asymptomatic congenital CMV with isolated hearing loss — Valganciclovir for 6 months is also recommended to prevent hearing deterioration.
Craniosynostosis is treated with surgical correction:
- Strip craniectomy — for single suture craniosynostosis in early infancy (< 3 months)
- Cranial vault remodeling — comprehensive reshaping of the skull for complex or multiple suture involvement
- Ideal age: 6–12 months for most cases, before brain growth is further restricted
- Spring-mediated cranioplasty — newer technique for single-suture synostosis
- Postoperative: Ophthalmology follow-up (for papilledema), developmental monitoring, and helmeting if needed
Early surgery prevents raised intracranial pressure and allows normal brain growth.
- Determine recurrence risk based on etiology
- Autosomal recessive (MCPH): 25% recurrence risk per pregnancy → parents counseled about prenatal testing (amniocentesis for molecular diagnosis if mutation identified)
- De novo chromosomal: Low recurrence risk
- Environmental/TORCH: Prevention for future pregnancies (rubella vaccination, CMV precautions, avoid alcohol)
- Discuss prognosis, developmental expectations, educational placement
- Discuss prenatal diagnosis options for future pregnancies: Chorionic Villus Sampling (CVS), Amniocentesis, Preimplantation Genetic Testing (PGT)
- Psychosocial support for parents (acceptance, coping, local support groups)
Prognosis is highly variable and depends on the underlying etiology:
| Etiology | Prognosis |
|---|---|
| Familial microcephaly | Normal intellect, good prognosis |
| Microcephaly vera (MCPH) | Mild-moderate intellectual disability, usually able to function independently with support |
| Congenital CMV (treated early) | Hearing loss may be stabilized; neurodevelopmental outcomes variable |
| Lissencephaly | Severe intellectual disability, intractable seizures, poor survival |
| HIE-related microcephaly | Depends on severity — can range from mild to severe disability |
| Craniosynostosis (treated) | Good if treated early |
In general: The more severe the microcephaly (lower the SD), the worse the expected neurodevelopmental outcome. However, individual variation is wide.
Children with microcephaly should receive all routine immunizations as per the national immunization schedule (UIP/IAP). Vaccinations are generally safe unless the child is on immunosuppressive therapy or has specific contraindications.
- Ensure up-to-date routine schedule (BCG, OPV, IPV, DTP, Hep B, Measles, MMR)
- Children with underlying immune deficiency (e.g., on steroids for epilepsy) — live vaccines need caution
- MMR vaccine can prevent congenital rubella in future siblings (vaccinate mother post-delivery if non-immune)
- Influenza and pneumococcal vaccines — recommended for children with neurological conditions
🔭 Recent Advances — Exam Q&A
Zika virus (flavivirus, transmitted by Aedes aegypti mosquito) emerged as a major cause of congenital microcephaly during the 2015–2016 epidemic in Brazil. It is now considered a potential addition to the TORCH group.
Key points:
- Zika infects and destroys neural progenitor cells in the fetal brain during neurogenesis → severe microcephaly
- Congenital Zika syndrome features: severe microcephaly with partially collapsed skull, periventricular calcifications, ventriculomegaly, lissencephaly/pachygyria, polymicrogyria, corpus callosum abnormalities, arthrogryposis, ocular anomalies (chorioretinal atrophy, optic nerve atrophy)
- Maternal Zika infection is often mild — pruritic maculopapular rash, fever, arthralgia, conjunctivitis
- Vertical transmission risk highest in first trimester
- No specific antiviral treatment available; management is supportive
- Prevention: Mosquito control, avoid travel to endemic areas during pregnancy
MCPH (Microcephaly Primary Hereditary) genes are a group of genes that, when mutated, cause autosomal recessive primary microcephaly. They encode proteins critical for centrosome function, mitotic spindle regulation, and cell division of neural progenitor cells during embryonic neurogenesis.
| Locus | Gene | Notes |
|---|---|---|
| MCPH1 | MCPH1 (Microcephalin) | Premature chromosome condensation; DNA repair |
| MCPH2 | WDR62 | Second most common; broader phenotype (pachygyria, polymicrogyria) |
| MCPH5 | ASPM | Most common (~40–50%); regulates mitotic spindle in neuroblasts |
| MCPH6 | CENPJ (CPAP) | Centrosomal; overlaps with Seckel syndrome |
These genes were shown to have undergone positive selection in human evolution, suggesting they played a role in the expansion of the human neocortex. This evolutionary insight has driven significant research into human brain size determination.
Molecular testing: Whole Exome Sequencing (WES) or targeted MCPH gene panel is used for diagnosis in consanguineous families with isolated microcephaly.
- WES sequences all protein-coding regions of the genome and has revolutionized the diagnosis of genetic causes of microcephaly
- Particularly useful when: karyotype is normal, no TORCH cause identified, consanguineous families, or isolated microcephaly with no identifiable cause on routine workup
- Diagnostic yield in primary microcephaly: 30–50% (higher in consanguineous families)
- Can diagnose known MCPH gene mutations as well as novel variants
- Enables preimplantation genetic testing (PGT) for future pregnancies once causative variant is identified
- Trio WES (proband + both parents) increases diagnostic yield and helps determine de novo vs. inherited variants
Brain organoids (cerebral organoids) are 3D mini-brain structures grown from induced pluripotent stem cells (iPSCs) in the laboratory. They mimic early human brain development and have been instrumental in microcephaly research:
- Organoids derived from iPSCs of microcephalic patients show reduced size and premature neural differentiation — recapitulating the disease in a dish
- Zika virus was shown to preferentially infect and kill neural progenitor cells in organoids, providing mechanistic evidence for Zika-induced microcephaly
- Used to screen potential therapeutic drugs and identify pathways involved in cortical development
- Represent a significant advance in understanding the cellular basis of primary microcephaly
- Valganciclovir for congenital CMV: 6 months of therapy improves hearing and neurodevelopmental outcomes (standard of care)
- Congenital Toxoplasmosis: Pyrimethamine + Sulfadiazine + Folinic acid for 12 months — reduces severity of neurological damage when treated early
- Zika: No specific antiviral; candidate antivirals and vaccines (Zika mRNA vaccine) are under development. Intensive rehabilitation remains the cornerstone
- mRNA vaccine technology (pioneered in COVID-19 vaccines) is being applied to develop vaccines against Zika, CMV — these could prevent congenital infections in the future
⚡ Key Points — Quick Revision
One-Liners for Exam
- Definition: OFC > 2 SD below mean for age and sex
- Severe microcephaly: OFC > 3 SD below mean (microcephaly vera)
- HC at birth (term): ~34 cm; at 1 year: ~46–47 cm
- Microcephaly is a sign, not a diagnosis — always find the etiology
- Primary = congenital (present at birth): Failure of neurogenesis
- Secondary = acquired (normal HC at birth): Later brain injury — HIE, meningitis, metabolic
- Most common TORCH cause: CMV (periventricular calcifications)
- CMV gold standard test: Urine PCR within first 3 weeks of life
- CMV treatment: Valganciclovir 16 mg/kg/dose BD for 6 months
- Toxoplasma calcification: Diffuse/scattered (vs. CMV periventricular)
- Most common MCPH gene: ASPM (MCPH5) — ~40–50%
- MCPH inheritance: Autosomal recessive; associated with consanguinity
- Microcephaly vera MRI: Small brain with simplified gyral pattern; normal architecture
- Craniosynostosis vs. microcephaly: Palpable bony ridge at suture; abnormal head shape; normal brain; needs surgical correction
- Familial microcephaly: Small HC but normal intellect; small parental HCs
- Zika = emerging TORCH: Severe microcephaly, periventricular calcifications, arthrogryposis, chorioretinitis
- First-line imaging: MRI brain (CT preferred when calcifications suspected)
- Management: No cure — early intervention (PT, OT, SLT), multidisciplinary team, manage seizures
- Radiation-sensitive period: 8–15 weeks gestation
- Rett syndrome: Girls only; acquired microcephaly; loss of purposeful hand use; hand wringing; MECP2 gene
- Prenatal diagnosis tool of choice: Antenatal USG (HC); fetal MRI for structural detail
- Recurrence risk in MCPH: 25% per pregnancy (autosomal recessive)
Quick Reference: Etiology vs. Key Feature
| Etiology | Distinguishing Feature |
|---|---|
| CMV | Periventricular calcifications, sensorineural hearing loss |
| Toxoplasmosis | Diffuse calcifications, hydrocephalus, chorioretinitis |
| Rubella | Cataracts, CHD (PDA), deafness, "blueberry muffin" rash |
| Zika | Severe microcephaly, collapsed skull, polymicrogyria, arthrogryposis |
| Fetal Alcohol Syndrome | Smooth philtrum, thin upper lip, short palpebral fissures; maternal alcohol |
| MCPH (Microcephaly Vera) | Consanguinity, sloping forehead, redundant scalp, isolated, autosomal recessive |
| Down Syndrome | Typical facies, hypotonia, simian crease, CHD |
| Craniosynostosis | Bony ridge at suture, abnormal skull shape, normal brain |
| HIE (secondary) | Normal HC at birth, perinatal asphyxia history |
| Rett Syndrome | Girls, acquired microcephaly, hand wringing, regression |