CASE REPORT
Annals of Nuclear Medicine Vol. 15, No. 3,267-270, 2001

Transient seizure activity demonstrated by Tc-99m HMPAO SPECT
and diffusion-weighted MR imaging
Takao SAGIUCHI,Katsumi IsHn, Yuuji ASANO, Yuki AOKI, Reiko WOODHAMS,
Hisashi YANAIHARA,Shinichi KAN and Kazushige HAYAKAWA

Department of Radiology, Kitasato University School of Medicine

Cerebral perfusion single photon emission computed tomography (SPECT) has been used to
confirm the localization of the epileptic focus and the evaluation of seizure. Recently, diffusionweighted MR imaging (DWI) has been recognized for evaluation of seizure activity. We describe
a case of transient seizure activity demonstrated by Tc-99m HMPAO SPECT and DWI. This patient
was a 61-year-old woman with a 10-month history of right middle cerebral artery (MCA) infarction
who had a generalized seizure during MRI. DWI immediately after seizure showed transient
hyperintensity in the right frontal gray matter and the white matter, and these apparent diffusion
coefficients (ADC) were transiently decreased. This transient hyperintensity on DWI corresponded
to transient hyperperfusion identifying the epileptic focus on interictal Tc-99m HMPAO SPECT.
Transient sustained seizure activity might cause these changes on DWI and SPECT. It was
considered that interictal Tc-99m HMPAO SPECT showed the delayed hyperperfusion caused by
excitatory neuronal overaction and DWI showed cytotoxic edema seizure-induced by energy
failure of the membrane-bound Na/K-ATPase pump.

Key words: seizure activity, epilepsy, diffusion-weighted MR imaging, technetium-99m
hexamethylpropyleneamine oxime (Tc-99m HMPAO), single photon emission computed tomography (SPECT)

INTRODUCTION
IN EPILEPSY,it is known that cerebral perfusion single
photon emission computed tomography (SPECT) is very
useful for evaluation and localization of the epileptic
focus.l,2 The usefulness of diffusion-weighted MR imaging (DWI) for epilepsy was recently reported, and it has
been recognized for the evaluation of seizure activity.3~
DWI is a sensitive method for assessing the molecular
motion of water. The extent of water diffusion in vivo is
determined as the apparent diffusion coefficient (ADC).
A decrease in ADC is seen in regions of restricted water
diffusion, which appears as hyperintensity on DWI. DWI
has become an essential tool for making a diagnosis of
acute cerebral ischemia or infarction. 7 In this report we
Received January 25, 2001, revision accepted March 6, 2001.
For reprint contact: Takao Sagiuchi, M.D., Department of
Radiology, Kitasato University School of Medicine, 1-15-1,
Kitasato, Sagamihara, Kanagawa 228-8555, JAPAN.

Vol. 15, No. 3, 2001

describe a case of transient seizure activity demonstrated
clearly by technetium-99m hexamethylpropyleneamine
oxime (Tc-99m HMPAO) SPECT and DWI.

CASE REPORT
This patient was a 61-year-old woman who had a 10month history of mild left hemiparesis due to cerebral
infarction in the right middle cerebral artery (MCA)
territory. On January 24, 2000, she noticed left-sided
facial spasms, which continued for more than 1 hour, so
she was transported to our hospital by ambulance. On
admission, she was alert and well oriented. She had a
simple partial seizure in the left face. Her simple partial
seizure was controlled by administration of diazepam
intravenously. 3 hours later, MRI was performed on a
1.5 T (Signa Horizon Lx, GE-Yokogawa Medical Co.,
Tokyo). During MRI, she suddenly had a generalized
seizure. The seizure subsided within a few minutes without further anticonvulsant therapy. Immediately after the

Case Report 267

A

B

Fig. 1 A 61-year-old woman with a 10-monthhistory of right middle cerebral artery (MCA) infarction
has symptomatic epilepsy. (A) Diffusion-weighted MR imaging (TR/TE/EC 10000/99/1,5-mm section
thickness, b-value of 1000 s/mm2, three directions) immediately after the seizure shows hyperintensity
in the right frontal gray matter and in the white matter around an old infarction of the right MCA territory.
(B) Tc-99m HMPAO SPECT (740 MBq) in the interictal state shows hyperpeffusion in the right frontal
cortex. The regional cerebral blood flow of old infarction in the right MCA territory is observed as severe
hypoperfusion.

seizure ceased, DWI showed hyperintensity in the right
frontal gray matter and slight hyperintensity in the white
matter around an old cerebral infarction in the right MCA
territory (Fig. 1A). Fluid-attenuated inversion recovery
(FLAIR) images showed no acute cerebral infarction.
After MRI, a generalized seizure occurred again. Although the generaIized seizure was controlled by administration of diazepam intravenously, she had disturbance
of consciousness for approximately 5 hours. Nine hours
later she again became alert, cerebral perfusion SPECT
was obtained. SPECT was performed 5 minutes after
intravenous injection of Tc-99m HMPAO (740 MBq).
We used a gamma camera (Starcam 400AC/T, GEYokogawa Medical Co., Tokyo) equipped with a lowenergy all-purpose collimator, and collected data under
the following conditions: 128 x 128 matrix, 360 ~ 64
directions, and 35 seconds per direction. During reconstruction of SPECT images, a Butterworth filter and a
Ramp filter were used for preprocessing and postprocessing, respectively. Interictai Tc-99m HMPAO
SPECT showed significant hyperperfusion in the right
frontal cortex and hypoperfu-sion in the region of old
infarction in the right MCA territory (Fig. 1B). Electro-

268 Takao Sagiuchi, Katsumi Ishii, Yuuji Asano, et al

encephalography 24 hours after seizure onset showed no
seizure discharges or waves. Thereafter, she had no
epileptic episode. MRI and Tc-99m HMPAO SPECT
were repeated 8 days later. On DWI, the abnormalities in
the right frontal gray matter and white matter around the
old infarction in the right MCA territory had returned to
normal intensity (Fig. 2A), T2-weighted MR and FLAIR
images showed no evidence of acute cerebral infarction
(Fig. 2B, C). On Tc-99m HMPAO SPECT, hyperperfusion
in the right frontal cortex had returned to the baseline (Fig,
2D). On the basis of her clinical course, DWI and SPECT
findings, it was suggested that she had symptomatic
epilepsy due to old cerebral infarction in the right MCA
territory and her epileptic focus was in the right frontal
lobe.
DISCUSSION
Cerebral perfusion SPECT is a useful method for evaluating the change in regional cerebral blood flow (CBF) in
a seizure. Ictal SPECT shows hyperperfusion and interictal SPECT shows hypoperfusion or no changes in the
epileptic focus.l.2 Although it is known that postictal CBF

Annals of Nuclear Medicine

A

C

D

Fig. 2 MRI and Tc-99m HMPAO SPECT (740 MBq) 8 days later, (A) The abnormalities on diffusionweighted MR imaging (TR/TE/EC 10000/99/1, 5-mm section thickness, b-value of 1000 s/mm2, three
directions) in the right frontal gray matter and in the white matter around an old infarction in the right
MCA territory have returned to normal intensity. (B and C) T2-weighted MR (TR/TE/EC 4000/105/2)
(B) and fluid-attenuated inversion recovery (TR/TE/EC/TI 8000/112/1/1800) imagings (C) show no
evidence of acute cerebral infarction in the right frontal gray matter and in the white matter around an
old infarction in the right MCA territory. (D) Interictal Tc-99m HMPAO SPECT (740 MBq) shows that
the hyperperfusion in the right frontal cortex has returned to the baseline.

Vol. 15, No. 3, 2001

Case Report

269

changes return to the baseline within 10-30 min after
seizure, 8 postictal and interictal hyperperfusion in the
epileptic focus has been reported in SPECT 9,1~or PET lj
studies. In the present case, interictal Tc-99m HMPAO
SPECT also showed transient hyper-perfusion in the
right frontal cortex. CBF in the right frontal cortex was a
transient increase of approximately 41% compared with
CBF in the left frontal cortex. The interictal hyperperfused phenomenon in the epileptic focus might be considered to be sustained seizure activity because interictal
hyperperfusion was transient and the patient had no neurological deficit in this episode, but the mechanism of
hyperperfusion in the postictal or interictai state has not
been clarified. 11
Changes in water diffusion in status epilepticus with
DWI has been reported by investigators. The epileptic
focus will appear as hyperintensity on DWI and there will
be a decrease in ADC. In a model of bicuculline-induced
status epilepticus in rats, Zhong et al. 3 reported that the
reduction in ADC was approximately 14-18% within 3
hours after injection of the drug. In experimental model of
kainic acid-induced status epilepticus in rats, Righini A et
al. 4 reported that the reduction in ADC was approximately
36--49%, and reached a peak 24 hours after intraperitoneal
kainic acid injection. In man, Wieshmann et al. 5 reported
a patient with a 27% decrease in ADC in the left motor
cortex during status epilepticus. Lansberg et al. 6 reported
three patients with complex partial status epilepticus who
had a mean 36% decrease in ADC. In the present case,
DWI immediately after seizure showed hyperintensity in
the right frontal gray matter and white matter around an
old infarction in the right MCA territory. The ADC in the
gray matter decreased approximately 21%, and ADC in
the white matter decreased approximately 10%, respectively, compared with the contralateral cerebral hemisphere. It is said that in a seizure energy failure of the
membrane-bound Na/K-ATPase pump caused by excitatory neuronal overaction ~2,13 leads to cytotoxic edema
induced by an influx of extracellular water and Na ยง into
the cells 13and shrinkage of the extracellular space with an
high K+. 14 We suggest that the decrease in ADC in
sustained seizure activity was caused by cytotoxic edema
associated with excitatory neuronal overaction. 6 The
mechanism of a decrease in ADC in seizure activity may
be considered to differ from that in acute cerebral ischemia or infarction, because cytotoxic edema in ischemic stroke was caused by energy failure of the membrane-bound Na/K-ATPase pump associated with a
reduction in CBF.
From our SPECT and DWI findings, we considered
that a transient hyperperfusion and hyperintensity in the
right frontal gray matter might be associated with excitatory neuronal overaction. SPECT is useful for the localization and evaluation of CBF changes caused by excitatory neuronal overaction in the ictal, postictal or interictal
state. DWI may be useful for evaluating seizure-induced

270 Takao Sagiuchi, Katsumi Ishii, Yuuji Asano, et al

cytotoxic edema caused by seizure activity. The repeated
cytotoxic edema induced by seizure activity may lead to
chronic hypofunction in the epileptic focus or intractable
epilepsy.
In conclusion, it is very important to understand the
condition of the nerve cells and its effect on seizure
activity. In this case we could not obtain SPECT and DWI
at the same time. To clarify the pathology of seizures, it
will be important and necessary to compare cerebral
perfusion SPECT findings with DWI findings. Therefore,
if possible, SPECT and DWI shoud be done at the same
time.

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Annals of Nuclear Medicine