Moyamoya Disease
Radiology Cases in Pediatric Emergency Medicine
Volume 3, Case 9
Karen R. Sevigny Brown, MD
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
     This is a previously healthy, right-handed 7-year old 
Asian female who presents to the E.D three hours after 
developing right sided weakness of sudden onset.  She 
had been feeling well until noon, when she developed 
weakness of her right hand and was unable to feed 
herself.  She sat up and tried to walk to her room.  Her 
father noted that her right leg was "crooked" and she 
kept falling to the right.  Her arm was "hanging to the 
side" and was not swinging properly.  Her father also 
noted that her smile was "crooked."  She has remained 
alert through this illness.  There is no history of fever, 
trauma, seizures, loss of consciousness, headaches, 
migraines or palpitations.
     Exam:  VS  T37, P110, R24, BP 105/58.  Weight 19 
kg (10th percentile), Height 114 cm (10th percentile).  
She is healthy appearing, cooperative, and alert in no 
distress.  She speaks well without dysarthria or 
aphasia.  Head normocephalic.  Optic disc margins 
sharp.  TM's normal.  Oral mucosa clear.  Neck supple, 
no bruits.  Heart regular, grade 1/6 systolic ejection 
murmur, vibratory in quality, at the left sternal border.  
Lungs clear.  Abdomen benign.  Color and perfusion 
are good.
     Cranial nerve findings:  Vision is intact.  Pupils equal 
and reactive.  EOM's full.  Peripheral fields full.  Hearing 
intact.  Her tongue is midline.  Her uvula deviates to the 
left.  There is an obvious flattening of the right 
nasolabial fold and weakness of the right face.  
Specifically, weak closure of the right eye and 
movement of the forehead on the right.  Her facial 
sensation is intact.  Her masseter function is not weak.  
Trapezius function is good bilaterally.
     Extremities:  Using 4/4 as full strength, her right UE 
is 2/4 and her right LE is 2/4.  Her left side is not weak.  
DTR's are 3+ bilaterally.  There is a positive Babinski 
sign on the right.  Her left plantar reflex is downgoing.  
Sensation is fully intact.  Her observed gait is obviously 
unsteady.  She falls to the right.  Her cerebellar function 
is hard to test on her right because of her weakness.  
Her left side is normal.
     A CT scan is obtained.  Before we see the result of 
the CT scan, can you estimate where her CNS "lesion" 
is likely to be.

     1) Brain versus spinal cord ?
     2) Are her findings due to a small lesion or a large 
infarct as seen in the typical ACA (anterior cerebral 
artery) and MCA (middle cerebral artery) distributions?
     3) Is this likely to be a neoplasm, a hemorrhage, or 
an infarct?

     This is not a spinal cord lesion since she has 
extensive facial involvement.
     A large infarct is not likely since she is alert.  
Additionally, her motor findings extend from her face to 
her lower extremities without affecting speech and 
language.  This is most likely a smaller lesion.
     The sudden onset makes a neoplasm less likely 
although neoplasms can hemorrhage and undergo 
sudden expansion.  A hemorrhage is less likely since 
her symptoms are not progressing, she has no 
headache, and has no signs of increased intracranial 
pressure.  An infarct is uncommon in this age group, 
however, a small infarct would account for her findings 
and the sudden onset.

     4) Where is her lesion likely to be?

     It is most likely to be in a small area where the motor 
fibers (both corticospinal and corticobulbar), originating 
from the left brain, come together.  Since her sensation 
is unaffected, sensory pathways should be unaffected.  
A likely possibility is the posterior limb of internal 
     For a brief of review of the neuroanatomy of the 
brain in this region, refer to the diagram at any time.

View neuroanatomy.

     L = Lateral ventricles.  The anterior horns and the 
posterior horns are shown in this diagram.
     3 = Third ventricle.
     CC = Corpus callosum.
     C = Caudate nucleus.
     P = Putamen
     G = Globus Pallidus.  The putamen and globus 
pallidus together form the lenticular (lentiform) nucleus.
     T = Thalamus
     Arrows = Internal Capsule [anterior limb, posterior 
limb, genu (bend)].
     O = Optic radiations.
     A = Auditory radiations.

     The corticospinal tract originates from the motor 
strip of the cerebral cortex.  The fibers collect as they 
traverse through the posterior limb of internal capsule.  
The tract largely crosses the midline in the decussation 
of the pyramids.  Fibers exit the spinal cord at their 
respective levels.

View our patient's CT scan. 

     The image on the left is without contrast.  The same 
cut is shown on the right with contrast.  The patient's 
right is to the left of the image as marked.  There is a 
hypodense region in the left posterior basal ganglia.  
The white arrow points to this region which is in the 
area of the putamen adjacent to the posterior limb of 
internal capsule.  Although the neuroanatomy on the CT 
scan is not well defined, you should still be able to 
identify the caudate nucleus, the lenticular nucleus, and 
the thalamus.  The internal capsule can be identified 
faintly.  The posterior limb is located between the 
thalamus and the lenticular nucleus.  The anterior limb 
is located between the caudate nucleus and the 
lenticular nucleus.  There is no significant mass 
effect.  This hypodensity does not enhance with 
contrast suggesting that this is an ischemic lesion.
     A pediatric neurologist is consulted and she is 
admitted to the hospital.  An MRI scan is obtained.  
Magnetic resonance angiography (MRA) is also 

View MRI scan.

     T1 (left image) and T2 (right image) weighted axial 
images are shown (different levels).  On the T1 image, 
the ventricles appear to be dark and the infarct seen in 
the left lenticular nucleus is dark as well.  The T2 image 
is a lower cut through the center of the infarct.  The T2 
image shows the CSF within the ventricles to be white.  
The infarct appears as a white lesion in the caudate 
nucleus and the left putamen.  In the T2 image, internal 
capsule is dark.  Note the obvious distortion of the 
anterior limb of the left internal capsule, compared to 
the right.  The posterior limb of the left internal capsule 
is also slightly distorted (compared to the right) adjacent 
to the infarct in the putamen.  This study is read as an 
infarct in the left basal ganglia, the posterior limb of 
internal capsule, and the head of the caudate. 
     The structures of this T2 image are labeled if you 
have difficulty identifying the structures.
The white arrows point to the anterior and posterior limb 
of internal capsule.  The black arrow points to the genu.  
The other labeled structures are the caudate nucleus
(C), globus pallidus (G), putamen (P), and  thalamus
(T).  The lateral ventricles are white.

View MRA study.

     There is obvious narrowing and irregularity of the left 
internal carotid artery and its branches.  The arrow on 
the right points to the supraclinoid portion of the internal 
carotid.  The arrow on the left points to the horizonal 
section of the anterior cerebral artery.  She is 
tentatively diagnosed with Moyamoya syndrome.  An 
angiogram is ordered.

View angiogram.

     The image displayed here is an AP view of her left 
internal carotid angiogram.  The arrows point to 
narrowed regions in the internal carotid artery and its 
branches.  The classic "puff of smoke" pattern seen in 
Moyamoya disease was not visualized.  This patient 
turns out to have probable fibromuscular displasia (a 
rare cerebrovascular disease).

View "puff of smoke".

     The image displayed here is an internal carotid 
angiogram taken from a different patient with a more 
typical Moyamoya disease angiogram.  The black arrow 
points to the "puff of smoke" which represents 
neovascularization providing collateral blood flow.  
There is stenosis of the internal carotid artery proximal 
to this puff of smoke.  The white arrow points to a 
dilated ophthalmic artery which is providing collateral 
circulation as well.

     Moyamoya disease is a disease of the large cerebral 
vessels that results in a network of small collateral 
vessels that form a pattern on angiography resembling 
a "puff" or "hazy cloud" of smoke (the English 
translation of the Japanese term, moyamoya).  
Diseased vessels may narrow and occlude resulting in 
transient ischemic attacks and/or cerebral infarcts, or 
they may rupture resulting in spontaneous intracranial 
hemorrhage.  Patients may also present with 
headaches.  This condition presents largely in childhood 
and is uncommon (Despite this, three likely cases have 
been diagnosed in our center this year).  Moyamoya is 
often divided into a syndrome and a disease, however, 
both are not specific.  Not much is known about its 
etiology.  Its course typically results in progressive 
neurological deterioration.  While steroids and 
vasodilators have little or no effect in the long term 
outcome, a surgical procedure shunting intracerebral 
vessels may have long term benefit.  This patient's 
angiographic studies are not diagnostic of Moyamoya.  
This may be an early case of Moyamoya or some other 
type of vasculopathy.

Strokes in Children
     Stroke can be defined as an acute onset neurologic 
deficit lasting more than one hour.  The 
pathophysiologic mechanisms for vascular dysfunction 
include cerebral embolism, arterial and/or venous 
thrombosis, and intraparenchymal/subarachnoid 
hemorrhage.  In contrast to adults, cerebral vascular 
disease is not usually associated with atherosclerosis, 
hypertension, or diabetes.
     Sudden loss of function is usually characteristic for a 
cerebral embolism.  Incomplete improvement may be 
seen as the embolus fragments and reperfusion occurs.  
Cerebral embolism in children is most often associated 
with cardiac disease.
     Thrombotic infarction may be difficult to distinguish 
from embolic infarction.  Cerebral artery thrombosis 
takes longer to develop than embolism and may be 
preceded by transient ischemic attacks.  In children, 
arterial thrombosis is related to vasculopathy of cerebral 
blood vessels, hemoglobinopathy, and vasculitis.  
Venous thrombosis often presents with seizures and 
increased intracranial pressure with the most common 
causes including infection, dehydration, 
hemoglobinopathy, and malignancy.
     The presenting signs and symptoms of 
intraparenchymal and subarachnoid hemorrhage 
include severe headache, vomiting, and deterioration of 
function.  However, the findings may be very subtle, 
such as alteration in mental status and a bulging 
fontanelle in infants.  Trauma, hematologic disorders 
(sickle cell disease), vascular malformations (aneurysm 
and arteriovenous malformations) and inflammatory 
disease are among the most common causes of 
strokes in children.  Child abuse should be suspected in 
any child with an unexplained intracranial hemorrhage.
     When considering stroke in children, a diverse 
differential diagnosis must be considered.  Hemiplegia 
with other focal deficits can follow a seizure (Todd's 
paralysis).  Usually this dysfunction resolves within 6 
hours with complete resolution by 24 hours.  A child 
may frequently be found hemiplegic in the morning 
following an unwitnessed nocturnal seizure.  An 
intracranial mass, either neoplasm or abscess, may 
mimic a vascular lesion.  Tumors may often 
hemorrhage into a necrotic area, with localized 
compression or invasion of intracranial vascular 
structures.  Infection must be considered since multiple 
micro-infarcts are a common complication of bacterial 
meningitis.   Complicated and basilar migraines may be 
accompanied by neurologic symptoms, with alternating 
hemiplegia attributed to basilar migraine in children.
     Several conditions cause stroke in children.  Heart 
disease is the most common of these, responsible for 
one-third of all ischemic infarctions in children.  Right to 
left (cyanotic) intracardiac shunts can cause 
polycythemia, leading to thrombosis and embolism.  
Congenital heart disease with valvular defects and/or 
cardiomyopathies can lead to thrombus formation and 
stroke.  Another common cause is hematologic 
disorders such as sickle cell disease which is 
associated with multiple infarcts.  Coagulation disorders 
such as hemophilia and platelet disorders have an 
increased risk of intracranial hemorrhage and stroke.  
Homocystinuria, an uncommon autosomal recessive 
disorder, leads to an increased tendency for thrombosis 
as a result of endothelial damage from excessive 
homocystine, thus leading to platelet aggregation and 
thrombus formation.  Inherited disorders of the blood 
vessel wall can result in hemorrhage (AVM's, 
aneurysms, tuberous sclerosis, neurofibromatosis, 
hereditary hemorrhagic telangiectasia, fibromuscular 
dysplasia, von Hippel-Lindau syndrome, and Fabry 

     Riela AR,  Roach ES.  Etiology of Stoke in Children.  
Journal of Child Neurology 1993;8:201-220.
     Pavlakis SG, Gould RJ, Zito JL.  Stroke in Children.  
Advances in Pediatrics 1991:151-179.
     Matsushima Y, Aoyagi M, Niimi Y, Masaoka H, 
Ohno K.  Symptoms and Their Pattern of Progression 
in Childhood Moyamoya Disease.  Brain & 
Development 1990;12:784.
     Rooney CM, Kaye EM, Scott M, Klucznik RP, 
Rosman NP.  Modified Encephaloduro-
arteriosynangiosis as a Surgical Treatment of 
Childhood Moyamoya Disease:  Report of Five Cases.  
Journal of Child Neurology 1991;6:24-31.

Return to Radiology Cases In Ped Emerg Med Case Selection Page

Return to Univ. Hawaii Dept. Pediatrics Home Page

Web Page Author:
Loren Yamamoto, MD, MPH
Professor of Pediatrics
University of Hawaii John A. Burns School of Medicine