Stroke. 2006;37:e1-e2
Published online before print November 23, 2005,
doi: 10.1161/01.STR.0000195179.93268.e2
(Stroke. 2006;37:e1.)
© 2006 American Heart Association, Inc.
Ataxic Hemiparesis From Strategic Frontal White Matter Infarction With Crossed Cerebellar Diaschisis
Alexander C. Flint, MD, PhD;
MaryAlice C. Naley, MD
Clinton B. Wright, MD
From the Neurological Institute of New York, Columbia University Medical Center, New York.
Correspondence to Clinton B. Wright, MD, MS, 710 W 168th St, NI-640, New York, NY 10032. E-mail cwright{at}neuro.columbia.edu
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Abstract
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Background Ataxic hemiparesis is a classic lacunar syndrome
that most often localizes to the pons.
Results We report 3 patients who presented with left-sided ataxic hemiparesis and were found on imaging to have small right frontal subcortical white matter infarcts in similar locations by diffusion-weighted MRI. [99mTc]hexamethylpropylenamine oxime single-photon emission computed tomography (SPECT) scans in all 3 patients showed decreased metabolism in the contralateral cerebellar hemisphere, indicative of crossed cerebellar diaschisis (CCD).
Conclusion CCD is under-recognized in ataxic hemiparesis and may have implications for functional recovery after this type of ischemic stroke.
Key Words: ataxia lacunar infarction magnetic resonance imaging tomography, emission computed stroke
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Case 1
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A 62-year-old right-handed man with a history of hypertension,
type 2 diabetes mellitus, and hypercholesterolemia presented
with sudden onset of left-sided weakness and clumsiness of the
arm and leg. There was no history of atrial fibrillation, no
history of previous stroke, and no family history of stroke.
On examination, power was 4 out of 5 in the left arm and leg
on the Medical Research Council scale and a mild left-sided
upper-motor neuron facial paresis. There was only subtly decreased
sensation on the left side of the body compared with the right.
The reflexes were brisk on the left side, and there was an extensor
plantar response on the left. He had left-sided dysmetria, dysdiadochokinesis,
and marked end point tremor out of proportion to his weakness.
MRI showed a small acute infarct in the right periventricular
posterior frontal white matter on diffusion-weighted imaging
(DWI). There was no abnormality of the cerebellum or brain stem
on MRI. A brain SPECT scan on day 3 demonstrated hypoperfusion
of the left cerebellar hemisphere (
Figure , case 1), consistent
with the phenomenon of crossed cerebellar diaschisis (CCD).
Ultrasonographic evaluation of the heart and cervical vessels
revealed no source of emboli, confirming the lacunar/small vessel
stroke subtype in this patient. The National Institutes of Health
Stroke Scale (NIHSS) score on admission was 4, and the modified
Rankin Scale (mRS) on discharge was 3.

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DWI (black and white panels) and [99mTc]hexamethylpropylenamine oxime SPECT (color panels) from each of the 3 cases (case 1 to case 3). Arrows indicate the region of the infarct detected by DWI, and arrowheads indicate the area of hypoperfusion detected by SPECT. The calculated asymmetry index (affected cerebellar hemisphere SPECT intensity/unaffected cerebellar hemisphere SPECT intensity x100) was 51.5% in Case 1, 84.8% in Case 2, and 48.7% in Case 3.
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Case 2
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A 72-year-old right-handed man presented with sudden onset of
left-sided clumsiness and gait ataxia. On examination, he had
mild left pronator drift but no weakness on confrontation. The
sensory examination and reflexes were normal. Coordination testing
showed mild left-sided dysmetria, dysdiadochokinesis, and end
point tremor. Brain MRI demonstrated a very small right subcortical
white matter acute infarct on DWI, with no MRI abnormalities
in the cerebellum or brain stem. A brain SPECT scan done on
day 3 showed subtle hypoperfusion of the left cerebellar hemisphere
that was consistent with his subtle ataxia. Ultrasonographic
evaluation of the heart and cervical vessels revealed no source
of emboli. The NIHSS score on admission was 3, and the mRS on
discharge was 1.
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Case 3
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A 49-year-old right-handed man awoke with left arm and leg weakness
and left-sided clumsiness and gait imbalance. On examination,
he had a left pronator drift, decreased fine motor movements
with the left hand, and mild (four fifths) weakness of the proximal
left leg. The sensory examination and reflexes were normal.
There was profound left-sided dysmetria, dysdiadochokinesis,
failure of checking, and end point tremor, with veering to the
left on attempted ambulation. Brain MRI showed a small right
subcortical white matter infarct on DWI, with no abnormalities
in the cerebellum or brain stem. Brain SPECT done on day 4 showed
hypoperfusion of the left cerebellar hemisphere. As with the
first 2 cases, ultrasonographic evaluation of the heart and
cervical vessels revealed no source of emboli. The NIHSS score
on admission was 3, and the mRS on discharge was 2.
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Discussion
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Ataxic hemiparesis (AH) is one of the classic lacunar syndromes.
The "lacunar hypothesis" is fulfilled for AH, in that the majority
of cases are caused by lacunar (small vessel) infarction.
1 Small
vessel infarctions producing AH are reported most commonly in
the pons or the internal capsule/corona radiata. In one series
of AH, 40% of patients had infarcts in the internal capsule
or corona radiata, 31% had infarcts in the pons, 14% had infarcts
in the basal ganglia, 11% had infarcts in thalamus, and 3% had
infarcts in other brain stem locations.
1 In another large series
of AH, the infarct localizations were similar (43% pons, 13%
internal capsule only, 33% thalamocapsular, and 10% striatocapsular).
2 In another series, the most common infarct locations were internal
capsule, pons, and corona radiata.
3 The corona radiata localization
of the lacunar infarcts seen in our 3 cases is thus not an uncommon
cause of AH. Any of the common infarct locations that cause
AH may affect the corticopontocerebellar or dentatorubralthalamocortical
pathways to cause ataxia, but explicit demonstration of a resultant
crossed cerebellar diaschisis (CCD) in such lacunar infarcts
has not, to our knowledge, been reported.
CCD is thought to result from deafferentation of the affected cerebellar hemisphere attributable to contralateral interruption of corticopontocerebellar fibers. The hemispheric locations most likely to cause CCD after infarction appear to include the postcentral and supramarginal areas,4 but it is unknown how small of a cortical or subcortical infarct might give rise to the phenomenon of CCD.
CCD is most often reported in association with large cerebral hemispheric infarcts.57 Most series have reported patients with dense hemiparesis, thus preventing assessment for ipsilateral hemiataxia. However, in some cases with milder hemispheric strokes, ipsilateral ataxia has been reported.8
The 3 cases of AH presented here show that a small stroke in the right subcortical white matter can be sufficient to cause CCD. It is likely that the infarcts in these patients involved the corticopontocerebellar projections but had only a minimal effect on the descending corticospinal tract, thus producing hemiataxia out of proportion to hemiparesis.
The degree of CCD may provide useful information about potential for recovery.5 Further studies are needed to clarify the relationship between small vessel strokes, diaschesis, and recovery potential.
Received June 24, 2005;
accepted July 18, 2005.
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