J Clin Neurol.  2009 Jun;5(2):74-80. 10.3988/jcn.2009.5.2.74.

Cerebellar Hypoperfusion during Transient Global Amnesia: An MRI and Oculographic Study

• Yang YS
• Kim JS
• Kim SY
• Kim YK
• Kwak YT
• Han IW

• KMID: 2287657
• DOI: http://doi.org/10.3988/jcn.2009.5.2.74

Abstract

BACKGROUND AND PURPOSE: Transient global amnesia (TGA) is characterized by sudden anterograde and retrograde amnesia lasting for up to 24 hours. Diffusion-weighted magnetic resonance imaging (DWI) in cases of TGA and ischemia demonstrates a high frequency of high signal intensities restricted to the hippocampus, and this has been proposed as an etiology of TGA. The aims of this study were to characterize the DWI and single-photon-emission computed tomography (SPECT) findings during the acute and recovered phases of TGA and to correlate the findings with oculomotor abnormalities.
METHODS
Five consecutive patients with a clinical diagnosis of TGA underwent DWI and SPECT of the brain within 24 hours after symptom onset and again 3 days later. Eye movements were also recorded using three-dimensional video-oculography.
RESULTS
In all patients, DWI disclosed small punctuate (1-3 mm), high-signal lesions in the lateral portion of the hippocampus. The initial SPECT also revealed hypoperfusion in the cerebellar vermis, which had recovered by the follow-up examination. Three patients showed saccadic hypermetria or impaired smooth pursuit only during the acute phase.
CONCLUSIONS
Our patients with TGA showed cerebellar vermian hypoperfusion in addition to ischemic insults to the lateral hippocampus. The oculomotor abnormalities observed in our patients support the occurrence of cerebellar dysfunction during the TGA attack.

Keyword

transient global amnesia; MRI; SPECT; hippocampus; cerebellum; saccades; smooth pursuit

MeSH Terms

Amnesia, Retrograde
Amnesia, Transient Global
Brain
Cerebellar Ataxia
Cerebellar Diseases
Cerebellum
Eye Movements
Follow-Up Studies
Hippocampus
Humans
Ischemia
Magnetic Resonance Imaging
Pursuit, Smooth
Saccades
Tomography, Emission-Computed, Single-Photon

Figure

• 

  Fig. 1 Diffusion-weighted images obtained from a 64-year-old female. A: Initial diffusion-weighted images obtained at 11 hours after TGA onset show no lesion at b=1,000/5 mm and b=1,000/3 mm, but a subtle bright lesion (grade +) in the right hippocampus at b=2000/3 mm and b=3,000/3 mm (arrow). B: Diffusion-weighted images obtained 3 days after symptom onset show brighter lesions (grade ++) for all sequences (arrow).

• 

  Fig. 2 Comparison with eight healthy controls (p<0.005, k>100); cerebral activity was normalized using an ANCOVA scale (global=50 mL/min/100 g). A: Patient 5 showed a hypoperfusion in the cerebellar vermis, left medial temporal lobe, right corpus callosum, and bilateral frontal lobes. B: This same patient also exhibited hypermetric horizontal saccades. C: The cerebellar vermian hypoperfusion observed in patient 5 had normalized 3 days later. D: The saccadic hypermetria of both eyes on the video-oculography had disappeared 14 days after symptom onset.

• 

  Fig. 3 Brain regions showing significant decreases in cerebral perfusion in five TGA patients as compared with healthy subjects. Significant voxels (p<0.005, uncorrected cluster k>100) of statistical T-maps were superimposed onto a standard MRI template that was specially normalized to the Montreal Neurological Institute space. The color bar presents the T-scores. The transaxial planes were cut from 38 mm below the bicommissural plane at 4-mm intervals.

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