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Abstract:
Two patients with strokes were examined with MEG and MRI.
Patient 1 was a 42 year-old female with epilepsy. The MRI revealed
large cystic lesion involving the left occipital and lateral
parietal lobes, thought to represent a very old, possibly
intrauterine, infarct or hematoma. Magnetic responses to
somatosensory, auditory, and visual stimulation were measured, as
well as motor-evoked fields. None of the normal ipsilateral
responses to median left nerve stimulation were observed. However,
multiple ipsilateral dipoles were found in response to right median
nerve stimulation. Auditory responses were normal. The visual
responses to upper and lower visual field stimulation were lateral
to one another in the left hemisphere, as compared to the more
normal superior/inferior organization around the calcarine sulcus
on the right. Patient 2 is a 53 year-old female that suffered a
stroke approximately two years before examination. The MRI showed
right posterior temporal and parietal encephalomalacia including
the right central sulcus. Magnetic responses to somatosensory
stimulation were measured. The patient had no contralateral
response to left median nerve stimulation. There was a very large,
long-latency ipsilateral response to left median nerve stimulation.
In both cases the MEG was useful in examining long-term changes in
the functional organization of the brain following
infarction.
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