The Nonmalformed Hemisphere Is Secondarily Impaired in Young Children with Hemimegalencephaly: A Pre‐ and Postsurgery Study with SPECT and EEG

Abstract

Summary:Purpose: 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.

Temporal lobe impairment in West syndrome: Event‐related potential evidence

“…The diaschisis phenomenon has been proposed to account for the finding that focal cortical resection around the epileptogenic lesion, or hemispheric disconnection, can restore the contralateral hemisphere's functional and hemodynamic maturation. 16,[55][56][57] It will be important to determine whether impairments in interhemispheric temporal lobe connectivity impact on the development of verbal skills, as has been reported for cohorts of children with perinatal pathology. 58,59 In conclusion, an impairment of temporal lobe maturation is a likely sequela of WS.…”

Hemispherectomy in a Premature Neonate with Linear Sebaceous Nevus Syndrome

“…The intrauterine excessive fetal movement and hiccups were likely manifestations of intrauterine seizure activity [11]. Rapidly progressing clinical and EEG abnormalities raised concern for irreversible injury to the more normal-appearing right hemisphere, as a result of epileptogenic bombardment from the abnormal hemisphere [13,16,17,18,19]. The proposed mechanism of this injury has been decreased oxygenation of the more normal hemisphere by a steal-like phenomenon [18, 19].…”

“…Rapidly progressing clinical and EEG abnormalities raised concern for irreversible injury to the more normal-appearing right hemisphere, as a result of epileptogenic bombardment from the abnormal hemisphere [13,16,17,18,19]. The proposed mechanism of this injury has been decreased oxygenation of the more normal hemisphere by a steal-like phenomenon [18, 19]. Alfonso et al [19], using near-infrared spectroscopy (SPECT), found bilateral decreased oxygen saturation in a 3-week-old with tuberous sclerosis and hemimegalencephaly; this was interpreted as being due to increased oxygen consumption by the abnormal brain with decreased availability of oxygen to the normal hemisphere.…”

“…Alfonso et al [19], using near-infrared spectroscopy (SPECT), found bilateral decreased oxygen saturation in a 3-week-old with tuberous sclerosis and hemimegalencephaly; this was interpreted as being due to increased oxygen consumption by the abnormal brain with decreased availability of oxygen to the normal hemisphere. Soufflet et al [18] demonstrated earlier return of normal cerebral blood flow in infants who underwent early hemispherectomy compared to their counterparts. Our patient’s intracranial hypertension with compression of the more normal hemisphere added to the concern.…”

Epidermal nevus syndrome

“…Surgical resection of facial lipomatosis is difficult because of infiltration and lack of encapsulation; it usually requires re-intervention (Unal et al, 2000). Early extensive resection or surgical disconnection of the epileptogenic dysplastic hemisphere also may favor improved outcome by protecting the contralateral hemisphere from spreading of electrical activity (Soufflet et al, 2004). It may control severe epilepsy and preserve the development of higher cortical functions in the more normal contralateral hemisphere (Humbertclaude et al, 1997).…”