Hemispherotomy in Young Children

Historical Background: Anatomical hemispherectomy, in which most of the affected cerebral hemisphere
is resected, was first successfully used in 1938 by MacKenzie to treat epilepsy in a 16-year-old patient with
infantile hemiplegia.1 Subsequent uses of this operation yielded a rate of complete or nearly complete seizure control of up to 80 percent, but by the 1970s, surgeons noted a variety of severe late complications related to chronic hemorrhage into the large resection cavity. This entity became known as superficial-cerebral hemosiderosis and resulted in a 25 percent mortality rate.2

To reduce these risks, a variety of modified functional hemispherotomies were developed, in which the hemisphere was disconnected from the opposite side and from the underlying brain stem. Resection in these procedures was limited to selected regions such as the temporal lobe or the opercular areas. Larger resection cavities and the associated hemosiderosis were thus avoided, leading to fewer complications while preserving favorable rates of seizure control.2, 3 By the early 1990s, hemispherotomy had replaced hemispherectomy in most centers and yielded higher rates of seizure-free outcomes.3

Indications and Selection Criteria
To be considered for hemispherotomy, the patient must have seizures that are intractable to medical management and that originate almost entirely from the hemisphere under consideration. Furthermore, the function of that hemisphere must either be already impaired or there should be some evidence that the function has migrated to the contralateral side.3 Typical conditions include congenital hemiplegia from a prenatal vascular insult, Sturge-Weber syndrome, hemimegencephaly or diffuse hemispheric cortical dysplasia, Rasmussen encephalitis, hemiconvulsion-hemiplegia-epilepsy syndrome, or a sequela of trauma or infection.3

Outcome for Early Hemispherotomy
Despite the inherent risks of operating on young children, early relief of epilepsy may halt the deleterious effects of both the seizures and the anticonvulsant drugs on the developing brain and upon the unaffected side.3
Furthermore, evidence suggests that the greater degree of brain plasticity in younger patients might enhance and preserve neurological function after hemispherotomy. For example, one retrospective study showed that hemispherotomy offers the highest rate of seizure freedom when performed in patients with the shortest duration of epilepsy and the lowest age at seizure onset. In this review of 92 patients, 85 percent were seizure-free after at least one year of follow-up.4

1.     McKenzie KG. JAMA 1938; 111:168.
2.     Di Rocco C, Fountas K, Massimi, L. Hemispherectomy and Hemispherotomy Techniques. Chapter 25, Anatomical Hemispherectomy: 215-223.
3.     de Ribaupierre S, Delalande O. Neurosurgical Focus 2008; 25:1-10.
4.     Schramm J, Kuczaty S, Sassen R, Elger C, von Lehe M. Acta Neurochirurgica 2012; 154:2017-2028.

Case: A 16-month-old girl presented with seizures that began at 8 months of age. The seizures are typified by brief body spasms, occurring as often as 20 times a day in clusters. She was born prematurely at 29 weeks, and her weight is low, at the 5th percentile. She has a left hemiparesis and a left hemianopsia. Although she initially attained milestones of crawling and using words, these have regressed, and she no longer crawls or speaks fluidly. After treatment with ACTH failed at another institution, her family was told that no other treatment was available.

Phase I
Video/EEG Monitoring: Interictal spiking seen exclusively on the right. Seizure onset appears as diffuse desynchrony. 
MRI: Significant volume loss of white matter, particularly on the right side. Atrophy of right thalamus and dysmorphic right hippocampus.
PET: Overall decreased metabolism on the right side, with near absent activity in right occipital lobe and posterior right temporal lobe.

Surgery 
Because of the predominance of interictal spiking on the right, the anatomical evidence of right hemispheric atrophy, the baseline left hemiparesis and hemianopsia, and the PET evidence of decreased function on the right, the patient underwent a right-sided modified hemispherotomy. The procedure included resection of the right temporal lobe, resection of the frontal and parietal operculae, a corpus callosotomy, and disconnection of the remainder of the posterior and anterior neocortex from the brain stem and opposite side (see Figures). Due to her young age and low weight, a team was assembled consisting of both pediatric and epilepsy neurosurgeons from 
the Children’s Hospital of Georgia and Augusta University Medical Center. Only a handful of U.S. centers perform these procedures in children so young.

Outcome
The patient is seizure-free four months after surgery, thriving developmentally and regaining her milestones. Her activity has increased; she is saying more words, and she is laughing and looking directly at those around her. The use of her left hand and arm has improved since surgery, most likely due to the cessation of seizures and migration of her motor areas.


Figure Legends
Figure 1. Schematic view of this patient’s right hemisphere.
Figure 2. Same view with areas to be resected – temporal lobe (green), opercular areas (blue), and insula (purple). 
Figure 3. Expanded view showing the remainder of the hemisphere after resections.
Figure 4. Same view showing brainstem and callosum (yellow). The three boxes show the cuts made to disconnect the hemisphere from the stem and callosum in order to prevent seizure spread to the contralateral side.


For more information or to refer a patient, call 706-721-4626.