Evolution of Surgical Management for Intractable Epileptic Spasms☆
Introduction
The first historical account of infantile spasms comes from the Letters to the Editor section of “The Lancet” dating back to 1841. West1 described the semiology of infantile spasms in his own son as “bobbings” that “cause a complete heaving of his head forward toward his knees, and then immediately relaxing into the upright position…these bowings and relaxings would be repeated alternately at intervals of a few seconds…he sometimes has 2, 3, or more attacks in a day.” Dr West also reported the subsequent marked mental retardation and developmental delay.2 More than a century later, hypsarrhythmia was recognized as the characteristic electroencephalographic pattern of infantile spasms.3 The earlier-described triad of spasms (clusters of axial jerks), neurodevelopmental delay, and electroencephalographic findings was given several different names, but in 1960, Gastaut suggested the eponym of “West syndrome.”4 In 1958, adrenocorticotropic hormone was reported to be the first successful treatment for infantile spasms.5 During the next 3 decades, various medications including benzodiazepines and valproic acid were tried to control infantile spasms with variable success.2 In 1991, Chiron et al6 reported remarkable efficacy of vigabatrin, especially in cases of infantile spasms related to tuberous sclerosis. However, because of the medically intractable nature of infantile spasms in an overwhelming number of cases, the notion that some cases can be offered a curable surgical intervention was welcomed. The aim of curative epilepsy surgery in patients with infantile spasms is to obtain seizure freedom, stop the downhill course of encephalopathy, and to allow normal cognitive development.7 To attain this goal, epilepsy surgery teams make use of the data obtained from the semiology of seizures, interictal electroencephalogram (EEG), ictal EEG, ictal electrocorticography (ECoG), interictal ECoG, anatomical neuroimaging, functional neuroimaging, and neuropsychological testing.
This article is a review of the history and evolution of the surgical approach in managing West syndrome. As recommended by the International League against Epilepsy (ILAE), the term infantile spasms would be replaced by the term epileptic spasms in the remainder of this article.8
Section snippets
Focal Onset of Epileptic Spasms
Based on the sleep studies of patients with epileptic spasms, Hrachovy et al9, 10 postulated that the spasms may originate from areas near the sleep centers in the brainstem. This hypothesis was based on the observation that children with epileptic spasms have comparatively decreased rapid eye movement sleep, which then normalizes in those who are successfully treated with medications. This theory also supported the proposed abnormality of serotonergic metabolism in raphe nuclei as the
Introduction and Success of a Neurosurgical Approach
In several functional neuroimaging-based studies on epileptic spasms, the focal abnormalities were most commonly seen in the temporo-parieto-occipital regions.23, 24, 25 A study was done in 1987 and used single photon emission computed tomography (SPECT) technology. These patients had normal prior computed tomography (CT) scans, but SPECT imaging further revealed findings of focal hypoperfusion corresponding with the EEG abnormalities seen in the temporo-parieto-occipital regions.24 After 3
Role of PET Technology
Within the last 3 decades, PET scans have played a significant role in the identification of epileptic foci in cases of intractable epileptic spasms when conventional anatomical neuroimaging failed to reveal focal abnormalities. A review of 140 cases of medically intractable epileptic spasms revealed that without the use of PET imaging, only 30% (n = 42) of cases were classified to have symptomatic epileptic spasms. Of the 42 patients, 13 were included in the symptomatic group on
Outcome of Epileptic Spasms Without a Resectable Surgical Focus
In patients with multifocal PET scan abnormalities and a single epileptogenic focus on EEG, cortical resection provided improvement in seizure control, but patients remained developmentally delayed postresection.30, 40, 41 In 1996, another study was published that focused on the outcome of those infants who were not considered surgical candidates because of multifocal glucose metabolism PET scan abnormalities, multifocal or bilateral ECoG changes, or the absence of a recognizable epileptic
“Subtotal” Hemispherectomy
Not infrequently, the epileptogenic or nociferous cortex or both in a surgical case is very extensive, involving much of 1 hemisphere. When the child is not significantly hemiparetic, we have attempted to spare primary motor and sensory cortex to introduce a motor deficit. The concept of subtotal hemispherectomy is a relatively recent development regarding the surgical approach for intractable epileptic spasms. In 2014, a study evaluated 23 patients on whom subtotal hemispherectomies were
Palliative Epilepsy Surgery
The overall success rate for curative epilepsy surgery is 60%-80%.44, 45 However, in patients who have bilateral multifocal epileptogenic foci, curative surgery is not feasible. In some such cases, palliative surgery, such as hemispherectomy, lobectomy, multilobar resection, or tuberectomy, targeting the major focus of seizures can still be considered. The aim of this surgical approach is to decrease the patient’s seizure burden and improve quality of life. In a recent retrospective chart
Conclusions
The finding of a focal onset with secondary generalization epilepsy pattern was a major breakthrough in the management of patients with medically intractable epileptic spasms. FDG PET played an immense role in identification of a surgically resectable epileptic focus in many of these children. Curative surgical resection led to resolution of symptoms that profoundly changed the clinical course of these children. Proper identification and resection of a nociferous area not only led to improved
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