Volume 11 Issue 1 (February) - Australasian Society for Ultrasound ...

CASE STUDY
ASUM Ultrasound Bulletin February 2008; 11 (1): 30–35
Fetal intracranial abnormalities in the third ­
trimester – MRI as a useful diagnostic tool
Jacqueline Cartmill 1 , Ann Quinton 1 , Michael Peek 2
1
Nepean Centre for Perinatal Care and Research, Level 5 South Block, Nepean Hospital, Penrith, New South Wales 2750, Australia.
2
The University of Sydney, Nepean Centre for Perinatal Care and Research, Level 5 South Block, Nepean Hospital, Penrith,
New South Wales 2050, Australia.
Correspondence to Mrs Ann Quinton. Email aquinton@med.usyd.edu.au.
Fig 1: Sagittal transvaginal (TV) fetal brain USS at 26 weeks 6 days
demonstrating anechoic space posteriorly.
Fig. 3: Axial TV USS demonstrating preserved falx and difficulty in visualising
brain structures due to USS reverberation at 30 weeks gestation.
Introduction
Ultrasound has many advantages as an imaging modality as it
is relatively inexpensive, does not use ionising radiation, and
high resolution images are obtained allowing dynamic real time
assessment. It is widely employed in prenatal diagnosis and the
assessment of fetal anomalies, however, sonographic evaluation
of the fetal central nervous system (CNS) can be hindered
by the non-specific appearance of some abnormalities, and by
technical factors such as maternal obesity and advanced gestational
age 1 . Developments in the field of magnetic resonance
imaging (MRI), particularly the use of ultra fast image acquisition
which minimises fetal motion artefact, have led to its use
as a non-invasive, complementary technique in situations where
Fig. 2: Axial TV USS demonstrating bilateral anechoic areas posteriorly
and preserved frontal brain structures at 30 weeks gestation.
the extent of the fetal intracranial anomaly cannot be accurately
determined on ultrasound scan (USS).
We report three cases of fetal intracranial abnormalities
detected late in pregnancy where sonographic visualisation
of the structural anatomy of the CNS in the third trimester
was found to be inconclusive, and MRI was then used in an
attempt to clarify the diagnosis.
Case 1 – Hydranencephaly
A 41-year-old woman in her second pregnancy, booked
late for antenatal care and had a routine fetal anatomy scan
performed at 26 weeks 6 days gestation. An intra-cranial
abnormality was strongly suspected, although structures
were difficult to visualise, even with transvaginal scanning,
due to fetal position and gestational age (Figs. 1, 2, 3).
Amniocentesis was performed and reported a normal 46XY
(male) karyotype and negative polymerase chain reaction
(PCR) for cytomegalovirus (CMV) and toxoplasmosis. A
fetal MRI was performed, which demonstrated absence of
normal cortical mantle apart from a thin rim of tissue in
the inferior aspect of the frontal lobe and the inferomedial
aspect of the temporal lobes. The thalami, falx, cerebellum
and brainstem appeared to be intact. These findings were
consistent with hydranencephaly (Figs. 4, 5, 6).
Following multidisciplinary discussion regarding the
poor prognosis, the patient requested termination of pregnancy.
Fetocide was carried out with intracardiac potassium
chloride injection at 30 weeks gestation, followed by
induction of labour. A stillborn male infant was delivered
weighing 1240 g. Postmortem examination confirmed the
diagnosis of hydranencephaly.
0 ASUM Ultrasound Bulletin 2008 February 11 (1)