PICTORIAL INTERLUDE

Diagnosis of
paediatric

Huntington's
disease relies on
imaging findings

Savvas Andronikou
MB BCh, FCRad(D), FRCR (Lond)

Conrad Nel
MBChB

Department of Paediatric Radiology
Red Cross War Memorial Children's Hospital
University of Cape Town and Institute of Child

Health

Introduction
Huntington's disease is an autoso-

mally inherited neurodegenerative
disorder clinically characterised by

Fig. 1. Axial cerebral CT scsn of s child present-
Ing with seizures.
Level of the quadrigeminal plate cistern.

disturbances of movement, menta-
tion and behaviour. Onset is typically
in the 5th and 6th decade and symp-
toms can sometimes occur in an
affected child before appearing in the
affected parent, who is most likely to
be the father. Five per cent of patients
present under the age of 14 years.
Juvenile presentation differs from that
of adults, who usually show abnormal
movements; in children there may be
rigidity, dysarthria, progressive mental
deterioration and convulsions. Con-
vulsions occur frequently but late in
the course of the disease. This should

Fig. 2. Level of the thalami. Small atrophied heads
of the caudate nuclei with resultant squaring and
expansion of the frontal horns giving the 'box-like'
appearance. These features are diagnostic of
Huntington's disease.

50 SA JOURNAL OF RADIOLOGY • October 2001

be borne in mind when investigating a
child with 'epilepsy'.I

Pathology and
radiorogy

Both computed tomography (CT)
and magnetic resonance imaging
(MR!) can show striking basal ganglia
atrophy (typically volume loss of the
head of the caudate nucleus)."
Secondary focal enlargement of the
frontal horns of the lateral ventricles
(the lateral walls are convex towards
the shrunken caudate nuclei) results
in their progressively squared, 'box-
like' appearance. This is best appreci-
ated on coronal images but these are
not performed as a routine on CT
scanning and therefore the radiologist
must be able to appreciate this sign on
axial images (Figs 1 and 2). A ratio of
maximum width of the frontal horns
to intereaudate distance < 1.6 is con-
sidered diagnostic. Increased and
decreased putaminal signal intensities
on MR! have been reported. Also
common are associated atrophy of the
cerebellum and brain stern."

Conclusion
Because the above imaging find-

ings may be encountered during
imaging for 'epilepsy' without clinical
suspicion for Huntington's disease,
and because the parental disease may
not have manifested clinically as yet, it
is of utmost importance that the radi-
ologist be familiar with the character-
istic imaging findings. A rapid accu-
rate imaging diagnosis will allow for
genetic counselling prior to the child
reaching reproductive maturity.

References
1. Osborn AG. Diagnostic Neurotadiology. St

Louis: Mosby, 1994: 743-744.
2. Kirkwood RJ. Essentials of Neuroimaging. New

York: Churchill Livingstone, 1990: 316.