The nonmalformed hemisphere is secondarily impaired in young children with hemimegalencephaly: a pre- and postsurgery study with SPECT and EEG.
OBJECTIVE
To study separately the functional value of each cerebral hemisphere in hemimegalencephaly (HME). HME is a unique model of unilateral hemispheric lesion, but one suspects that the non-HME hemisphere also could be functionally impaired because the postsurgery outcome is less favorable than expected.


METHODS
We performed simultaneous prolonged EEG and 133-xenon SPECT (single-photon emission computed tomography); we measured the absolute values of cerebral blood flow (CBF) in both hemispheres and compared them with the normal values previously acquired. Thirteen patients (aged 5-38 months) underwent 31 examinations, 20 before surgery (hemispherotomy) and 11 after.


RESULTS
In the HME hemisphere, we confirmed the presurgical mixture of increased and decreased CBF due to intermittent ictal discharges. After surgery, CBF was decreased in most cases. In the non-HME hemisphere, presurgery CBF was abnormal in 60% of the patients, increased and related mostly to diffuse interictal spikes on the same side, whereas normal CBF cases had focal spikes. After surgery, CBF was normal in 82% of cases, corresponding to an EEG without diffuse spikes. In the six patients longitudinally studied, CBF dramatically decreased after surgery in the HME hemisphere, whereas in the non-HME hemisphere, CBF was mostly normal very early (three fourths before 2 months), increased as soon as 3 months, and normalized only after hemispherotomy, the more rapidly the child was operated on, the earlier it was.


CONCLUSIONS
This study shows that the function of the nonmalformed hemisphere is impaired as soon as the first months of the course of HME but can be restored after surgery. Our data support the recommendations to operate on the children as early as possible.
Soufflet
Christine
C
Clinical Neurophysiology Department, Necker-Enfants Malades Hospital, Paris, France.
Bulteau
Christine
C
Delalande
Olivier
O
Pinton
Florence
F
Jalin
Claude
C
Plouin
Perrine
P
Bahi-Buisson
Nadia
N
Dulac
Olivier
O
Chiron
Catherine
C
D001921:Brain / Q000002:abnormalities* / Q000098:blood supply* / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography / Q000706:statistics & numerical data*; D007839:Functional Laterality; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D009421:Nervous System Malformations / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000503:physiopathology; D012039:Regional Blood Flow; D015899:Tomography, Emission-Computed, Single-Photon / Q000706:statistics & numerical data*; D016896:Treatment Outcome; D014743:Videotape Recording; D014850:Waiting Lists; D014980:Xenon Radioisotopes
D014980:Xenon Radioisotopes