Radiology Cases in Pediatric Emergency Medicine Volume 3, Case 9 Karen R. Sevigny Brown, MD Loren G. Yamamoto, MD, MPH

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.

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 capsule.
   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.

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 performed.

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.

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.

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).

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 disease).

Copyrighted:Radiology Cases in Pediatric Emergency Medicine Volume 3, Case 9
Loren Yamamoto, MD, MPH
Professor of Pediatrics
University of Hawaii John A. Burns School of Medicine
loreny@hawaii.ed.