7-year old girl present with sudden onset of right sided weakness

image7-year old girl present with sudden onset of right sided weakness . 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.

Examination

  T37 C, P110, RR 24, BP 105/58.  Weight 19 kg (10th percentile), Height 114 cm (10th percentile).  She is healthy appearing, cooperative, and alert in no distress.  She peaks 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. 

1. Before we see the result of  the CT scan, can you estimate where her CNS "lesion" is likely to be ?????

  • This is not a spinal cord lesion since she has extensive facial involvement.
  • A arge 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.
  • he 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.

So 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 Lecture

image
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.


image
The image on the left is without contrast.  The same cut is shown on the right with contrast
2. Comment on this  CT scan  ?????
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.

View MRI scan.
image
T1 (left image) and T2 (right image) weighted axial images are shown (different levels).

3. Comment on this  MRI ?????

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 leftputamen.  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.
image

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.

image
 
4. Comment on this  MRA ????? 


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