Vol.24 No.1, 2008

73症 例 報 告超急性期外傷性び慢性脳浮腫におけるreversal sign on CT石藏礼一，安藤久美子，小川理世，高田恵広，廣田省三
兵庫医科大学

放射線医学教室

The reversal sign on CT of hyper-acute diffuse traumatic brain swellingin an infantReiichi Ishikura, Kumiko Ando, Masayo Ogawa, Yoshihiro Takada, Shozo Hirota
Department of Radiology, Hyogo College of Medicine

Abstract

We present the case of a 6 - month - old boy who under went brain CT and MR imaging

within 90 minutes after traumatic injury. CT image obtained within 1 hour of trauma showed the so-called
reversal sign on CT, with reversal of the relatively greater density of the cerebellum compared to that ofthe cerebrum. The diffusion weighted images (DWI) of MRI obtained 90 minutes after onset showed pancerebral restricted diffusion, whereas T2-weighted and FLAIR image ﬁndings were normal. In our case,the image ﬁnding of the reversal sign on CT was equally diagnostic as DWI of MRI for diffuse traumaticbrain swelling in the hyper-acute state.

Keywords Reversal sign on CT, Diffusion weighted image on MRI, Infant, Traumatic diffuse brainswelling

Introduction

diagnostic as hyper-intensity on a dif fusionweighted image（DWI）of MRI in this case.

Dif fuse brain swelling（DBS）due to closed

Case reporttraumatic brain injur y is a kind of malignant
brain damage obser ved mostly in infants andA 6 - month - old male infant with an unremarkablechildren under ﬁve years old1,2）. Early and accurate

bir th and medical histor y was brought to thediagnosis, where imaging plays a primary role, ishospital after a car accident. He was on his mother simportant.

lap without a seatbelt in the front seat of the car,

We present a case of 6 - month - old male infant

which was hit by another car from behind. Thewith head trauma who under went both CT andcar was pushed forwards and hit the car in front,

MRI within 90 minutes after the traumatic event.

and the infant was caught between his mother s

The so-called reversal sign on CT was equallychest and the air bag. He exhibited generalized

原稿受付日：2007 年 5 月 18 日，最終受付日：2007 年 7 月 26 日
別刷請求先：〒 663−8501 西宮市武庫川町 1 − 1

兵庫医科大学

放射線医学教室

石藏礼一

73

74 日本小児放射線学会雑誌

convulsions when the ambulance reached theT2-weighted images, and FLAIR images reveal nohospital 15 minutes after the accident. He wassignal changes in the cerebrum（Fig.2a, b）. Fast

intubated immediately and initial SaO2 was 85%.

spin - echo T2-weighted images showed motion

During the transfer, there was no apnea attack orartifacts（Fig.2a）. On DWI（spin - echo echo - plannercardiac arrest.

imaging with diffusion encoding in 6 axes, B=0,

He was presented to our hospital 30 minutes

1000s/ ㎟ ）, the entire cerebrum, predominantly

after the accident. At that time, SaO2 was 100% but

gray matter, exhibited marked hyper-intensity,

blood pressure was low（60/20mmHg）with a low

except for the right insular cortex and both anterior

heart rate of 70/min, and his Glasgow coma scale

medial temporal regions（Fig.2c）. Thalamic

was 7（E2V2M3）. His anterior fontanelle exhibitedregions were also spared（not shown）. There wasswelling, suggesting elevated intracranial pressure.

a faint hyper-intense area in the dorsal brainstem.

CT scan was performed 1 hour after the accident.

The cerebellum exhibited normal signal intensity.

On CT images, a shallow subdural hematoma was

The ADC map（not shown）exhibited restricted

obser ved in the left side. The entire cerebrum

diffusion. MR angiography was also performed, but

exhibited slightly lower attenuation than that ofthere were no remarkable ﬁndings（not shown）.

the cerebellum, which is the so-called reversal

Despite intensive care with low-temperature

sign on CT （Fig.1a, b）. Cortical and white mattertherapy and steroids, CT examination performedinterface is slightly obscure.

after 24 hours revealed pan-cerebral low attenu-3）

MR scan was performed immediately after CT.
ation with diffuse brain swelling（Fig.3）

examination to conﬁrm the area of brain damage.

His electro-encephalogram showed a ﬂat pattern

MR images（Philips, Intera, 1.5T unit）including

on the next day, and he died 12 days after theT1-weighted images（not shown）, fast spin - echo

accident.

abFig.1 CT images 1 hour after onset
a : A shallow subdural hematoma was observed on the left side (arrows). Cortical and whitematter interface is slightly obscure.
b : The entire cerebrum exhibited slightly lower attenuation (arrows) than that of the cerebellum(arrowheads), which is the so-called reversal sign on CT.

74

Vol.24 No.1, 2008

75

a bc

Fig.2 MR images 90 minutes after onset.
a, b : T2-weighted image (a) and FLAIR image(b) show no abnormal signal change. T2weighted images showed motion artifacts.
c : On DWI, the entire cerebrum, predominantly
gray matter, exhibited marked hyper-intensity,
except for the right insular cortex andboth anterior medial temporal regions andcerebellum. There was a faint hyper-intensearea in the dorsal brainstem.

Discussion

the dominant contribution of intracellular edema

DBS, generalized cerebral swelling, or traumaticin DBS 5,6）. In our case also, restricted diffusion

cerebral edema is a malignant finding associatedsuggested intracellular edema. DWI is wellwith traumatic brain damage or asphyxia which

established as a sensitive MR technique in theis often obser ved in infants and yound children

detection of intracellular edema in acute brain

under ﬁve years of age1）. This generalized cerebral

ischemia.

swelling probably results from a combination of

The CT features of DBS are diffuse brain swelling

extracellular and intracellular edema and decrease

and the so-called reversal sign on CT1）. The reversal

in vascular resistance, resulting in vasodilatation

sign consists of a diffusely decreased density ofand increased cerebral blood volume 4）. Recent

cerebral cor tical gray and white matter with areports suggest, according to the DWI findings,

decreased or lost gray/white matter inter face,75

日本小児放射線学会雑誌

76

therefore look carefully and may need to observe
the images in narrow window width（under 60H.U.）.
Prognostic value of the reversal sign on CT inpediatric traumatic events has not been discussed
fully. In anoxic/ischemic cerebral injury, Hans et
al reported that patients with the reversal sign had
a poorer prognosis than those without it3）. On theother hand, Lang et al. evaluated the prognosis ofDBS after head injury and reported a better outcome
in children than in adults11）. The reversal sign on
CT in pediatric traumatic events may therefore
suggest a poor prognosis, but not always.
Recent studies have suggested that MRI may
be useful for blunt head trauma in the pediatricFig.3 CT image obtained after 24 hours shows
typical diﬀuse brain edema

population. Sue et al reported that of 18 children
with pr esumed non-accidental trauma who
under went MR imaging studies within 5 days ofpresentation, 16（89%）demonstrated abnormalities

or reversal of the gray/white matter densities

on DWI/ADC5）. Sigmund et al evaluated CT within

and relatively greater density of the cerebellum,

24 hours and MRI study 7 ＋/− 4 days after injury

brainstem, and thalami. In other words, thisand concluded that CT is inconsistent in lesion

1,3）

.

detection and outcome prediction in pediatric

It probably represents a diffuse brain edema as a

traumatic brain injur y 12）. However, they also

result of anoxic/ischemic cerebral injury 3,7,8）.

suggested that CT has an advantage in that theﬁnding is described as white cerebellar sign

It is noticeable that the reversal sign was

information is quickly obtained and aids in theobser ved on CT 1 hour after the injur y in ourrapid treatment of neurosurgical emergencies. Wecase. To our knowledge, this is the first reportsuggest, too, that CT is the brain imaging modalityof reversal sign on CT detected 1 hour after theof first choice evaluating pediatric trauma, buttraumatic event. In our case, the reversal signthat if the ﬁnding is not clear or the patient s stateon CT was obser ved only in the cerebellum,

is more severe than the imaging findings, MRIand thalami and brainstem were not white. Onincluding dif fusion-weighted images should beDWI, cerebral white matter and dorsal brainstem

considered.

showed restricted diffusion, whereas deep whitematter, thalami and cerebellum showed normal

Conclusion

diffusion. From these findings, the reversal sign

We present CT and MRI images of a case in theon CT in this case may reﬂect mainly the contrast

hyperacute stage of DBS. The reversal sign on CT

between hypo-dense cerebral cortex with edema

was subtle but equally diagnostic of DWI as MRI in

and normally dense cerebellar cortex. We suggest

our case. We should not miss this sign on CT.

that this is why the reversal sign was not observedin thalami or brainstem in our case.
As shown in our case, the reversal sign on CT
may be a subtle change in attenuation. We should

76

Acknowledgement
The authors would like to thank Ajaya R. Pandefor his help in preparing the manuscript.

Vol.24 No.1, 2008

● References
1） Blazer SI : Traumatic cerebral edema. Diagnostic
Imaging Brain, Ed by Osborn AG, Blaser SI,
Salzman KL, et al. Salt Lake City, Amirsys pbl,
2004, I - 2 - p46 - 49.
2） Arabi B, Hesdorffer DC, Ahn ES, et al : Outcome
following decompressive craniectomy formalignant swelling due to severe head injur y. JNeurosurg 2006 ; 104 : 469 - 479.
3） Han BK, Towbin RB, De Cour ten-MyersG,
et al : Reversal sign on CT : ef fect of anoxic/
ischemic cerebral injury in children. AJNR Am J
Neuroradiology 1989 ; 10 : 1191 - 1198.
4） Brazo P, Marmarou A, Fatouros P : Contributionof vasogenic and cellular edema to traumatic brain
swelling measured by diffusion-weighted imaging.
J Neurosurg 1997 ; 87 : 900 - 907.
5） S u h D Y, D a v i s P C , H o p k i n s K L , e t a l :Nonaccidental pediatric head injur y : diffusionweighted imaging findings. Neurosurgery 2001 ;49 : 309 - 318.
6） M a r m a r o u A , S i g n o r e t t i S , F a t o u r o s P P :Traumatic brain edema in diffuse and focal injury :cellular or vasogenic? J Neurosurg 2006 ; 104 :
720 - 730.

777） Bird CR, Drayer BP, Gilles FH : Pathophysiology
of "reverse" edema in global cerebral ischemia.
AJNR Am J Neuroradiol 1989 ; 10 : 95 - 98.
8） Schulman H, Laufer L, Berginer J, et al : CTfindings in neonatal hypothermia. Pediatr Radiol
1998 ; 28 : 414 - 417.
9） Ricci PE, Burdette JH, Elster AD, et al : A comparison of fast spin-echo, fluid-attenuated inversionrecovery, and diffusion-weighted MR imaging in
the first 10 days after cerebral infarction. AJNRAm J Neuroradiol 1999 ; 20 : 1535 - 1542.
10）Urbach H, Flacke S, Keller E, et al : Detectability
and detection rate of acute cerebral hemisphere
infarcts on CT and dif fusion-weighted MRI.
Neuroradiology 2000 ; 42 : 722 - 727.
11）Lang DA, Teasdale GM, Macherson P, et al :Diffuse brain swelling after head injur y : more
often malignant in adults than childr en? Jneurosurg 1994 ; 80 : 675 - 680.
12）Sigmund GA, Tong KA, Nickeson JP, et al :Multimodality Comparison of Neuroimaging inPediactric Traumatic Brain Injury. Pediatr Neurol
2007 ; 36 : 217 - 226.

77