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EXENCEPHALY : A RARE CASE DIAGNOSED ON ANTENATAL ULTRASOUND

Ajita J Nawale*, Suleman A Merchant**,Shyam Sunder R Koteyar*, Prakash Masand***
*Lecturer; **Professor and Head; ***Senior Resident, Department of Radiology, LTM Municipal Medical College and LTM General Hospital, Sion, Mumbai 400 022.

We wish to report a case of exencephaly which was diagnosed on antenatal USG in a primigravida patient with 18 weeks period of gestation with uterine enlargement larger than expected for dates.

CASE REPORT

Antenatal USG (Fig. 1) was performed in a primigravida patient with 18 weeks period of gestation, with uterine enlargement larger than expected for dates. It revealed an absent cranial vault with large amount of brain tissue exposed to the amniotic fluid with associated polyhydramnois. The spine showed evidence of kyphoscoliosis with no other obvious associated congenital anomalies. The foetus was a female and it showed jerky movements. Based on these findings the diagnosis of exencephaly with kyphoscoliosis was made. The patient was induced on the same day and a stillborn foetus was delivered and all the findings were confirmed.

DISCUSSION

Exencephaly is characterised by absence of cranial vault with a large amount of protruding brain tissue. This condition is considered to lie somewhere on the spectrum between anencephaly and encephalocoele.[1] It is much less common than anencephaly, but it has the same aetiology and recurrence risk as other neural tube defects.[1] Associations like spinal abnormalities, cleft lip, cleft palate and club foot, as in anencephaly may be noted, though exencephaly has been reported in association with exomphalos.[2] It may be an embryological precursor of the more common anencephaly, the exposed brain slowly degenerating through trauma and exposure to amniotic fluid, finally reaching the anencephalic stage.[3] The most striking feature is large amount of disorganised cerebral tissue arising from the base of the cranium as well as non-visualization of the calvarium. The residual brain mass is bereft of the normal features. The facial structures and the base of the cranium are always present.[2],[4] It is four times more frequent in female foetuses,[1] as was this foetus. As with anencephaly, exencephaly is also incompatible with life.[1]

Fig. 1
Fig. 1 : Antenatal USG showing a large amount of exposed brain tissue with absent cranial vault.


REFERENCES

1.  Alison Fowlie, Glyn Constantine. The Central Nervous System. In : Keith Dewbury, Hylton Meire, David Cosgrove, Barry Goldberg eds. Clinical Ultrasound : a comprehensive text : Ultrasound in obstetrics and gynaecology. Churchill Livingstone. pub. Edinburgh. 1993; 16 : 274-76.
2. Hendrics SK, Cyr DR, Nyberg DA, Raabe R, Mack LA. Exencephaly-clinical and ultrasonic correlation to anencephaly. Obstet Gynaecol 1988; 75 : 898-900.
3.  Ganchrow D, Ornoy A. Possible evidence for secondary degeneration of central nervous system in the pathogenesis of anencephaly and brain dysraphia : a study in young human fetuses. Virchows Arch 1979; 384 : 285-94.

4.  Cox GC, Rosenthal SJ, Holsapple JW. Exencephaly : Sonographic findings and the radiologic - pathologic correlation. Radiology 1985; 155 : 755-56.
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