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Intern. J. Neuroscience, Vol. 93(3-4). pp. 181-184
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Brief Communication

CROSSED CEREBRO-CEREBELLAR
DIASCHISIS IN A PATIENT WITH MELAS WITH
APHASIA BUT WITHOUT HEMIPARESIS
N.I.L.J. BOHNEN, M. BERAN-KOEHN, B. MULLAN and J.R. FULGHAM
Departments of Neurology and Nuclear Medicine, Mayo Clinic, Rochester MN 55905
(Received in final form 18 January 1997)
We describe a 25 year old woman diagnosed with MELAS during an acute stroke-like episode. Global
aphasia, migraine-like headaches and hemi-anopsia were her main clinical features. MR imaging
revealed extensive cortical and subcortical left hemispheric signal abnormalities. [Tc-99m]ECD
SPECT scanning revealed crossed cerebrocerebellar diaschisis. Aphasia in the absence of gross hemiparesis can be related to cross-cerebellar diaschisis in MELAS.

Keywords: Aphasia; cerebellum; diaschisis; MELAS; SPECT, stroke.

INTRODUCTION
Mitochondria1 myopathy associated with Lactic Acidosis and Stroke-like
episodes (MELAS) is a form of mitochondria1 encephalomyopathy that may present with stroke-like episodes, seizures, myopathy, and optic atrophy in children
or young adults (Hirano & Pavlakis, 1994). The term “diaschisis” refers to disturbance of function in an area remote from the site of a primary brain lesion (Meyer,
Obara & Muramatsu, 1993). Baron et al. (1990) observed a parallel reduction in
blood flow and oxygen use using PET in the cerebellar hemisphere contralateral
to a supratentorial cerebra1 infarction and coined the term “crossed cerebellar
Correspondence to Dr. N. Bohnen, Department of Neurology and Division of Nuclear Medicine,
The University of Michigan Medical Center, B 1G412 University Hospital, Ann Arbor, Michigan
48 109-0028.
181

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N.I.L.J. BOHNEN rt ifl

diaschisis". It is probably caused by disruption of the corticopontinecerebellar
pathways and is commonly seen in stroke patients with major motor deficits. It
occurs less frequently in non-motor deficit stroke.

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CASE DESCRIPTION
A 25-year-old woman presented with episodes of headache associated with
homonymous vision field defects. Her previous medical history was significant
for long standing hearing loss, short body status. and oral contraceptive medication. Initial MR imaging revealed increased T2 signal in the right occipital lobe
that subsequently cleared. A new episode with headache and contralateral hemianopsia revealed increased T?, signal in the left occipital lobe extending into the
posterior temporal and parietal lobe. Signal changes were more prominent in the
cortex. Subsequently. patient was found to be in a withdrawn. depressed state and
was transferred to Mayo Medical Center.
Clinical examination revealed a young slender woman of short body habitus with
a surgically corrected micrognathia and minimal facial dysmorphic features.
Neurologic examination revealed an alert woman with mixed sensory more than
expressive aphasia: pupils were equal in size and reactive to light; fundoscopic
examination showed bilateral optic atrophy. Patient was able to walk. Coordination
was precerved: reflexes were brisk with a right sided Babinsky response in the
absence of hemiparesis. MRI examination with FLAIR sequences revealed extcnsive increased signal in the left temporal. occipital and parieto-occipital lobes with
mild mass effect and minimal radiolopic evidence of uncal herniation. Minimal signal changes were seen in the medial right cerebellar hemisphere as well.
Leptomeningeal enhancement was confined to the left occipital lobe. EEG revealed
hi-occipital and left temporal slowing without epilep tiform changes. Muscle
biopsy findings revealed succinate dehydrogenase deficiency consistent with
MELAS. Mitochondria1 DNA analysis revealed not a specific defect.
The SPECT study were performed following intra-venous injection of
I! 1 .-I
mCi of Tc-99m Ethylene Cysteine Dimer (ECD) in darkened room with the
patient's eyes closed and the ears unplugged. Imaging was performed on a dual
headed SPECT camera (Elscint Helix) equipped with ultrahigh-resolution fan
beam collimators and acquired in a 128 x 128 matrix. There were 120 views at
3 degrees intervals for 15 seconds per view using a circular orbit. The energy setting was at 140 keV with a 15-208 window. The reconstruction was performed
with a standard filtered backprojection algorithm. rebinned into 64 x 64 matrix
with a 2X zoom, attenuated correction applied and viewed in the usual 3 orthogonal planes. The reconstructed system resolution was approximately 7mm

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DIASCHISIS AND APHASIA

183

FWHM and the pixel size was 4.4mm. Both color- and gray-scale images were
used for qualitative visual interpretation.
The study shows a large area of significantly decreased perfusion in the left temporal, parietal and occipital lobes. At the edges of the defects there is focally
increased perfusion particularly at the fronto-parietal junction. Perfusion to the left
basal ganglia is increased compared to the right. The areas of increased perfusion
may related to blood flow to brain compressed by edema as luxury perfusion is said
not to occur with Tc-99m ECD. Cerebellar perfusion is asymmetric with reduction
on the right cerebellar hemisphere in keeping with crossed cerebellar diaschisis.
Thalamic perfusion may be minimally reduced on the left [Fig. 11.

DISCUSSION
Reports of SPECT studies in patients with MELAS are scarce and indicate early
enhanced perfusion followed later by are of low perfusion at the sites of the

FIGURE 1 SPECT perfusion study shows crossed right cerebellar diaschisis and reduced radiotracer
activity in the left temporal and occipital lobes.

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N.I.L.J. BOHNEN et al.

reported stroke-like imaging abnormalities (Gropen et al., 1994; Fujii et al.,
1995).
Crossed cerebellar diaschisis most often occurs with a hemiparesis, indicating
functional damage to motor projection pathways from cortex to cerebellum (Meyer
et al., 1993). Barker et al. (1 99 1) studied the effect of behavioral activation on cerebral and cerebellar glucose metabolism in healthy volunteers when performing a
verbal memory task. This PET study revealed asymmetric metabolic activation
which was opposite in direction within the cerebral and cerebellar hemispheres.
This coupled metabolic activation of one cerebellar hemisphere and areas within the
opposite cerebral hemisphere represents the inverse of crossed cerebellar diaschisis
phenomenon commonly observed in supratentorial lesions. Overall, these authors
found that the predominant supratentorial activation was within the left hemisphere
and is likely due to the left hemisphere's dominance for language function.
With respect to MRI data and diaschisis, Stubgen (1995) reported a case with
focal motor seizures and extensive right hemispheric signal abnormalities and
mild left medial cerebellar signal changes that resolved 6 weeks later. This may
have been the first report of MRI evidence of diaschisis.
The presence of prominent crossed cerebellar diaschisis in our patient with
severe aphasia but without apparent hemiparesis further illustrates the importance
of the cerebellum in behavioral functioning. Botez and colleagues (199 1 ) postulated at least 3 main anatomical pathways which could be involved in crossed cerebellar diaschisis. One of these arises from the posterior parietal association cortices
to the basis pontis and could have been involved in our patient. Further studies are
needed to clarify the role of the cerebellum in relation to behavioral functioning.

References
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