Radiology


34 SA JOURNAL OF RADIOLOGY • February 2005

LETTERS

The hyperdense
middle cerebral
artery sign in a
polycythaemic

child

To the Editor: The hyperdense mid-
dle cerebral artery (HMCA) sign is
known to be an early sign of intracra-
nial arterial occlusion or infarction
during unenhanced CT imaging of
the brain.1 This sign has also been seen
after treatment with bromide,2 in
cocaine abusers3 and in adults with
elevated haematocrit,4 but has not
previously been reported to be a result
of polycythaemia in children. We
recently encountered this sign as an
incidental finding throughout the ves-
sels of the circle of Willis in a child
with a cyanotic heart condition and
speculate that the dense appearance of
these intracranial vessels was the result
of polycythaemia. A 4-year-old girl
was admitted with headaches, vomit-
ing and fever. The child had an atrial
septal defect, ventricular septal defect,
pulmonary atresia and multiple
aorto-pulmonary collateral arteries.
Clinically, she was cyanotic and
clubbed. The neurological examina-
tion was normal. Laboratory tests
showed a haematocrit of 67.6% and
haemoglobin level of 21.9 g/dl in
keeping with polycythaemia. A CT
scan of the head was performed in

order to exclude a brain abscess or
meningitis. The uncontrasted CT scan
did not show any findings of a brain
abscess but the HMCA sign was seen
involving both middle cerebral arter-
ies as well as the basilar artery (Figs 1 a
and b). There was no clinical or radi-
ological evidence of cerebral infarc-
tion or vessel occlusion. The high
haematocrit may therefore have
increased the density of the blood
leading to an HMCA sign. Although
the HMCA sign has been shown to be
a false indicator of vascular occlusion
in adults,4 an association between an
elevated haematocrit and a HMCA in
children has not yet been reported.

References
1. Petitti N. The hyperdense middle cerebral

artery sign. Radiology 1998; 208: 687-688.

2. Osborne D, Bohan T, Hodson A. CT demon-
stration of hyperdense cerebral vasculature due
to bromide therapy. J Comput Assist Tomogr
1984; 8: 982-984.

3. Hall A, Wagle V. CT enhancement after use of
cocaine. Am J Neuroradiol 1990; 11:1083.

4. Rauch RA, Bazan C 3rd, Larsson EM, Jinkins
JR. Hyperdense middle cerebral arteries identi-
fied on CT as a false sign of vascular occlusion.
Am J Neuroradiol 1993; 14: 669-673.

Figs 1 a and b. Sequential non-contrast CT slices
in a 4-year-old girl show increased density of the
arteries of the circle of Willis due to polycythaemia.

H Douis
S Andronikou
S Jadwat

Department of Paediatric Radiology
Red Cross Children’s Hospital
University of Cape Town

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