Coupon Accepted Successfully!


Congenital anomalies of the central nervous system

A. Neural tube defect

NTD results from failure of the neural tube to close spontaneously between the 3rd and 4th weeks of in utero development.

Failure of closure of the neural tube allows excretion of fetal substances (e.g
α-fetoprotein AFP, acetyl cholinesterase) into the amniotic fluid serving as biochemical markers for a neural tube defect.

  1. Spina Bifida occulta              
  2. Meningocele
  3. Myelomeningocele        
  4. Encephalocele      
  5. Anencephaly 

1. Spina Bifida occulta


This common anomaly consists of a midline defect of the vertebral bodies without protrusion of the spinal cord or meninges.

Most individuals are asymptomatic and lack neurologic sign.

In some cases patches of hair, a lipoma, discoloration of the skin or a dermal sinus in the midline of the low back signifies an underlying spina bifida occulta


2. Meningocele

This is an out pouching of skin and meninges without obvious involvement of the neural element (Spinal cord)


3. Myelomeningocele [myelo(neural structures), meningo (meninges)]

  1. This represent most severe form of dysraphism involving the vertebral column. This is an out pouching of skin, meninges and neural element
  2. Incidence 1/1000 live birth
  3. The risk of recurrence after one affected child rises to 3-4% and increases to approximately 10% with two previous abnormal pregnancies.
  4. A myelomeningocele may be located any where along the spinal cord but the lumbosacral region accounts for at least 75% of the cases. 

Clinical features


  1. A lesion in the low sacral region causes bowel and bladder incontinence associated with anesthesia in the perineal area but with no impairment of motor function.
  2. A lesion in the mid lumbar region shows flaccid paralysis of lower extremitiesQ
    1. absence DTR
    2. Lack of response to touch and pain
    3. constant urinary dribbling and a relaxed anal sphincter
    4. postural abnormalities of the lower extremities (club feet and subluxation of the hips)
  3. A lesion in the upper thoracic or cervical region usually has very minimal neurological deficit and in most cases do not have hydrocephalus

4. Encephalocele


Ocipitally, cervically and more rarely frontally this defect is an out pouching of dura with or without brain.

5. Anencephaly

The cranial vault and posterior occipital bone are defective and derivatives of the neural tube are exposed.

  1. Cerebral hemisphere and cerebellum are usually absent & only a residue of the brain stem can be identified.
  2. The pituitary gland is hypoplastic and the spinal cord pyramidal tracts are missing owing to the absence of the cerebral cortex
  3. 50% cases associated with poly hydramnios 

Prenatal diagnosis of neural tube defects.

  1. Biochemical marker   b. USG
    1. AFP (most sensitive)
    2. Acetyl cholinesterase (most specific) 



Folic acid should be initiated one month before conception and at least 12 wk of gestation


Marker of neural tube defect: (AIPG 09)
A. Phosphatidyl esterase
B. Pseudo choline esterase
C. Acetyl choline esterase
D. Butyryl choline esterase


Ans C

B. Disorder of neuronal migration

  1. Lissencephaly
  2. Schizencephaly
  3. Porencephaly
  4. Holoprosencephaly
    1. Lisencephaly or agyria – characterized by absence of cerebral convolutions. There is 4 layered Cortex rather than usual six.
    2. Schizencephaly – is the presence of unilateral or bilateral cleft with in the cerebral hemisphere due to an abnormality of morphogenesis.
    3. Porencephaly- is the presence of cysts or cavities within the brain that result from development defect or acquired lesions including infarction of tissue.
    4. Holoprosencephaly due to defective cleavage of the prosencephalon

C. Microcephaly

Microcephaly is defined as a head circumference that measures more than 3 SD below the mean for age and sex


  1. Primary (Genetic)
    1. Familial (Autosomal recessive)
    2. Autosomal dominant
    3. Syndromes
      1. Down            
      2. Edward                
      3. Cri du chat          
      4. Cornelia de lange
  2. Secondary.
    1. Radiation                     
    2. Congenital infection             
    3. Drugs                   
    4. Malnutrition                 
    5. Meningitis                    
    6. Metabolic              
    7. Hypoxic ischemic encephalopathy

Test Your Skills Now!
Take a Quiz now
Reviewer Name