V. Holloway et al., The reorganization of sensorimotor function in children after hemispherectomy - A functional MRI and somatosensory evoked potential study, BRAIN, 123, 2000, pp. 2432-2444
Children who have suffered extensive unilateral brain injury early in life
may show a remarkable degree of residual sensorimotor function. It is gener
ally believed that this reflects the high capacity of the immature brain fo
r cerebral reorganization. In this study, we investigated 17 patients who h
ad undergone hemispherectomy for relief from seizures; eight of the patient
s had congenital brain damage and nine had sustained their initial insult a
t the age of 1 year or older. Sensorimotor functions of the hand were inves
tigated using functional MRI (fMRI) during a passive movement task, somatos
ensory evoked potentials (SEPs) arising from electrical and vibration stimu
lation, and behavioural tests including grip strength, double simultaneous
stimulation and joint position sense. On fMRI, two of the eight patients st
udied with this technique tone with congenital damage and one with damage a
cquired at the age of 3 years) showed activation in the sensorimotor cortex
of the remaining hemisphere with passive movement of the hemiplegic hand.
The location of the ipsilateral brain activation was similar to that found
on movement of the normal contralateral hand, although the latter was great
er in spatial extent. In one of these patients, a greater role was demonstr
ated for the ipsilateral secondary sensorimotor area (compared with the ips
ilateral primary sensorimotor area) for movement of the hemiplegic hand tha
n for movement of the normal hand. Median nerve stimulation of the hemipleg
ic hand showed reproducible early-latency ipsilateral SEP components in the
remaining sensorimotor cortex in 10 of the 17 patients (five with congenit
al and five with acquired disease). Five of the patients who demonstrated i
psilateral electrical SEPs also showed ipsilateral vibration SEPs (two with
congenital and three with acquired disease). The behavioural tests reveale
d residual sensorimotor function in 14 of the patients; however, not all of
the patients who exhibited ipsilateral SEP or fMRI responses had residual
sensorimotor function in the hemiplegic hand. Ipsilateral sensorimotor resp
onses were demonstrated both in patients with congenital disease and those
with acquired disease, suggesting that factors additional to aetiology and
age at injury may influence the degree of residual sensorimotor function an
d cerebral reorganization.