Background
Rasmussen’s encephalitis (RE), which was first reported in 1958 by professor Rasmussen, is a rare immune-mediated condition that is characterized by drug-resistant focal epilepsy, progressive neurological, and cognitive deficits associated with unilateral hemispheric atrophy [
1,
2]. Diagnosis criteria consist of clinical, electroencephalogram (EEG) and magnetic resonance imaging (MRI) features. However, Early diagnosis is particular challenge. RE is generally found in children with an onset age peak of approximately 6 years. Anti-epilepsy drugs are limited to secondarily generalized seizures and complex partial seizures, whereas epilepsia partialis continua is typically totally refractory [
2]. Surgery plays a major role in the treatment of childhood RE and aims to control seizures and interrupt the evolution of the structural encephalitic process. Because most of the lesions are limited to one hemisphere, functional hemispherectomy and hemispherotomy are the final effective treatments for controlling the seizures in these patients, although there are some neurological sequels [
3]. For most children with RE, these disconnective techniques constitute an extremely effective method to terminate seizures. Moreover, the contralateral disabled limbs may obtain good functional recruitment with effective compensation and can obviously improve the patient’s quality of life.
However, RE in adults is rare. There is little medical experience with the progression of RE initiation in adults. Whether surgical resection of damaged hemispheres is beneficial, as well as the degree of postoperative functional compensation, is unknown. The disconnective approach may not be feasible in adults with preserved neurological functions because of the heavy neurological morbidity [
4].
We report two special patients with adult-onset RE (A-RE) who received functional hemispherectomy at Xuanwu hospital. Surgical treatment for patients with A-RE is rarely reported. We discuss the clinical features, surgical treatment, and surgical outcome of patients with A-RE who underwent epilepsy surgery. The use of sample from the patients was approved by the Institutional Ethics Committee of Xuan Wu hospital Capital Medical University and informed consents have been obtained from patients prior to analysis.
Discussion
RE also known as Rasmussen syndrome, is an acquired, progressive, chronic inflammatory brain disease that develops in childhood, and it is characterized by refractory epilepsy, progressive hemiplegia, and mental decline in one hemisphere of the brain [
1]. However, RE with adult onset is rare, and it was reported in only a few publications [
5‐
7]. A-RE is reported with an atypical presentation and a slower and milder course in which motor and speech function are preserved [
8]. Compared with childhood RE patients, the A-RE patients had atypical electro-clinical features and less severe progression of the structural brain atrophy. It needed to be differentiated from hemiconvulsion-hemiplegia-epilepsy syndrome, focal cortical dysplasia and tuberous sclerosis. Therefore, a later correct diagnosis or misdiagnosis may occur. This milder progression of the structural brain atrophy is thought to be related to the selective susceptibility of specific brain structures to immunological or inflammatory processes [
9,
10].
Both of the patients in our report had typical refractory epilepsy and progressive hemiplegia. The two patients progressed to obvious hemiplegia in a few months. The MRI showed a prominent progressive hemispheric atrophy in patient 1 and relative milder alterations in patient 2.
Although some therapeutic options, such as new antiepileptic drugs or immunomodulatory agents, are now available for RE patients, seizure freedom is never completely achieved, and the epilepsia partialis continua is generally “super-refractory” [
11,
12]. Therefore, surgery remains a choice of treatment. Functional hemispherectomy or hemispherotomy is the most effective therapy to achieve long-term seizure freedom for 62.5–85% of patients, but some neurological complications occur [
2]. However, the experience of surgery for patients with A-RE is limited. Some authors preferred focal resection, but others suggested hemispherectomy [
6]. Limited cortical resection achieved sustained seizure freedom [
4]. One possible explanation of a favourable surgical outcome following limited cortical resection is that the surgical procedure produced seizure network disruption. Unfortunately, the favourable surgical outcome in that study was not paralleled by the inhibition of neurological progression in one of the two cases. Selective cortical resection may not change the progressive nature of this disease. Limited cortical resections are only transiently effective [
9]. Therefore, functional hemispherotomy is suggested, rather than a conservative surgical approach, to obtain favourable surgical outcome.
The lesions in these two patients located in the non-dominant hemisphere, which was relatively simple for surgical selection. However, if the lesion is located in the dominant hemisphere of the patient, the extent of impaired speech and contralateral compensation needs to be adequately assessed. As we know, the compensatory ability of language function in adults is significantly weaker than that in children. The common methods we used to assess the extent of language function are functional magnetic resonance imaging (fMRI) of language tasks and transcranial magnetic stimulation (TMS). There is still an opportunity to perform hemispherectomy if the patient develops significant speech impairment with evidence of contralateral compensation on either fMRI or TMS. Otherwise, hemispherectomy may not be recommended. As for the selection of hemispherical operations, the main consideration is the compensatory ability of the contralateral hemisphere, including the volumetric compensation. As we know, the compensatory ability is relatively weak in adults. Therefore, we didn’t applied anatomical hemispherectomy avoiding large intracranial cavity. Both functional hemispherectomy and hemispherical disconnection are suitable. Another consideration for the choice of functional hemisphrectomy in our two patients was the diagnosis. Because the A-RE was rare, the pathological examination was help for confirming the diagnosis of RE. Therefore, we performed functional hemispherectomy and removed some part of the damaged brain tissue in the intraoperative exposure.
Both patients in our report underwent functional hemispherectomy and had sustained seizure freedom, but hemiplegia was aggravated instantly after surgery. Fortunately, the hemiplegia was also gradually alleviated after rehabilitation. Although the hemiplegia was obvious, both patients could walk independently and achieved a satisfying postoperative quality of life.