Neuroradiology (2001) 43: 821±823
Ó Springer-Verlag 2001

M. Takasawa
M. Watanabe
S. Yamamoto
T. Hoshi
K. Kajimoto
N. Kinoshita

Received: 13 January 2001
Accepted: 26 February 2001

)

M. Takasawa ( )
Division of Stroke Studies,
Department of Internal Medicine and
Therapeutics, Osaka University Graduate
School of Medicine, 2±2, Yamadaoka,
Suita City, Osaka, 565±0871, Japan
e-mail tkswm@medone.med.osaka-u.ac.jp
Tel.: + 81-6-68 79 36 34
Fax: + 81-6-68 78 65 74
M. Takasawa ´ M. Watanabe ´ S. Yamamoto
´ T. Hoshi ´ K. Kajimoto ´ N. Kinoshita
Division of Stroke Studies,
Departments of Cardiovascular Medicine
and Clinical Research,
Osaka-Minami National Hospital. 2±1,
Kidohigashi-cho, Kawachinagano City,
Osaka, 586±8521, Japan

D IA G N O S T I C NE UR OR A DI O LO G Y

ªSchistotaxisº in cerebral blood flow
on 99 mTc-HMPAO single-photon emission
computed tomography during a seizure
following a stroke

Abstract We describe a patient
with seizures following a stroke in
whom on ictal 99 mTc-HMPAO single-photon emission computed tomography demonstrated cerebral
blood flow ªschistotaxisº, i. e., focal
hyperaemia corresponding to an epileptogenic focus together with an
extensive hypoperfused area in the
same hemisphere. This phenomenon may have been caused by
haemodynamic alternation and a
remote transneural effect during the
seizures.
Keywords Stroke ´ Seizure ´ Singlephoton emission computed
tomography ´ Crossed cerebellar
diaschisis

Introduction
Rapid conversion from the lipophilic to the hypolipophilic form which deposits technetium-99m-hexamethyl-propyleneamine oxime (99 mTc-HMPAO) in the
brain [1, 2] produces a ªsnapshotº of cerebral perfusion
at the moment of administration of the radiopharmaceutical. 99 mTc-HMPAO single photon emission computed tomography (SPECT) can therefore be useful for
localising an epileptogenic focus during an seizure, but
there have been few cases in which a focus has been
demonstrated during seizures following a stroke [3],
and there have been no detailed reports on the haemodynamic aspects of this type of seizure. We describe a
patient with seizures following a stroke in whom ictal
99 m
Tc-HMPAO SPECT demonstrated cerebral blood

flow (CBF) ªschistotaxisº, by which we mean focal hyperaemia corresponding to the epileptogenic focus, together with an extensive area of hypoperfusion area in
the same cerebral hemisphere.

Case report
A 74-year-old right-handed woman with a history of a cardiogenic
cerebral embolism to the left cerebral 4 months previously suddenly had focal convulsions involving the right side of her face. Immediately after intravenous injection of 99 mTc-HMPAO for a SPECT
scan, clonic convulsions spread to the proximal part of the right
arm and leg, without loss of consciousness. Before anticonvulsants
could be given, the convulsions gradually resolved over a 5-min period. Her consciousness was clear and the blood pressure, heart
rate, and body temperature were stable during the study. After

822

Fig. 1 CT 30 days before the
onset of the seizure (top) shows
a large infarct in the left hemisphere; 28 days after the seizure
(bottom) no new ischaemic or
haemorrhagic lesion is seen

the SPECT, the patient recovered fully to her neurological state
before admission, and there was no recurrence of stroke or seizure
during the next month. CT 1 and 28 days after the resolution of the
seizures showed no new ischaemic or haemorrhagic lesions (Fig. 1).
99 m
Tc-HMPAO SPECT was acquired on a dual-headed camera
with fan-beam collimators 20 min after intravenous injection of
740 MBq 99 mTc-HMPAO. The transaxial slices were reconstructed
by filtered backprojection with a Butterworth filter. Each reconstructed slice was corrected for tissue absorption by Chang's method. The ictal images revealed the presumed epileptogenic focus as
an area of focal hyperaemia adjacent to the infarct, and a frontal
and posterior cortical area of low perfusion in the left hemisphere
which was more extensive than on postictal images the following
day (Fig. 2). The ictal study also showed hypoperfusion of the right
cerebellar hemisphere, which had also resolved the next day.

Discussion
The pattern of CBF we describe suggests that the changes in ipsilateral regional CBF were caused by the
hyperaemic epileptogenic focus during the seizure.
However, the blood flow to the left parietal ictal area
was in the territory of a posterior branch of the middle
cerebral artery, and the reduction in perfusion in the

frontal lobe cannot therefore be easily explained by
haemodynamic steal, since this territory is supplied by
cross-filling via the anterior cerebral communicating artery or by residual left internal carotid artery perfusion.
The reduction in posterior CBF could theoretically be
produced by steal. The reduction in posterior CBF as a
result of local steal due to the focal hyperemia might
have caused a reduction in ipsilateral anterior circulation through the superior longitudinal or occipitofrontal
fasciculi.
Crossed cerebellar hyperperfusion in patients with
seizures has been described on ictal SPECT [4]. In our
case, severe hypoperfusion of the contralateral cerebellar hemisphere, crossed cerebellar diaschisis, on ictal
SPECT may have been caused by the extensive area of
low perfusion in the left hemisphere through the corticopontine pathway [5]. Its disappearance on postictal
SPECT could also be explained by the restoration of
blood flow in the supratentorial hypoperfused area after
the seizure. These observations may be useful in understanding the pathogenesis of seizures following strokes.

823

Fig. 2 Single-photon emission computed tomography (SPECT)
during the seizure (top) shows focal hypaeremia in the left cortex
(arrowheads) adjacent to the infarcted area. A larger area of low
perfusion in the frontal and posterior cortex (arrows) is more extensive than on the second SPECT study the next day (bottom). Severe crossed cerebellar diaschisis on the ictal SPECT is no longer
evident on the second study

References
1. Nowotnik DK, Canning LR, Cumming
SA (1985) Technetium-99m-HMPAO: a
new radiopharmaceutical for imaging
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2. Neirinckx RD, Canning LR, Piper IM,
et al (1987). Technetium-99 m d,lHMPAO: a new radiopharmaceutical
for SPECT imaging of regional cerebral
flow perfusion. J Nucl Med 28: 191±202

3. Marks DA, Katz A, Hoffer P, Spencer
SS (1992) Localization of extratemporal
epileptic foci during ictal single photon
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Neurol 31: 250±255
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DJ (1987) Reversible cerebellar diaschisis in focal epilepsy. Lancet ii:
625±626

5. Baron JC, Bousser MG, Comar D, Castaigne P (1980) ªCrossed cerebellar diaschisisº in human supratentorial brain
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