LEMON SIGN

Q.Lemon shaped skull on antenatal USG  is noted in
a.neural tube defect
b.down syndrome
c.achondroplasia
d.osteogenesis imperfect







ANS---A NEURAL TUBE DEFECT ------.LEMON'S SIGN REFERS TO BIFORNTAL SCALLOPING OR INDENTAION NOTED IN OPEN NEURAL TUBE DEFECT .

OTHER CHARACTERISTIC HEAD CHANGES IN OPEN NEURAL TUBE DEFECT ARE 

1.VENTRICULOMEGALY 
2.THE BANANA SIGN(C- SHAPED SHAPE OF CEREBELLUM,CHIARI 2 MALFOMATION ) 
3. CISTERNA MAGNA EFFACEMENT .

THE BANANA SIGN AND EFFACEMENT OF POSTERIOR FOSSA ARE RESULT OF HYPOPLASIA OF THE POSTERIOR FOSSA AND LEAK OF FLUID FROM THE OPEN SPINA DEFECT

REF

1.Adam: Grainger & Allison's Diagnostic Radiology, 5th ed.

2.DIAGNOSTIC ULTRASOUND ,3RD EDITION, RUMECK

3.http://www.fetalsono.com