Rolandic Epilepsy Surgery — Weighing the Risks
Abstract & Commentary
By Theodore H. Schwartz, MD, FACS, Associate Professor of Neurosurgery, Neurology and Neuroscience, Weill Cornell Medical College, New York Presbyterian Hospital. Dr. Schwartz reports no financial relationship relevant to this field of study.
Synopsis: Surgery for epilepsy in and around sensory-motor cortex can be effective in controlling seizures, but mild post-operative neurological deficits are not uncommon in patients operated on after age 25.
Source: Pondal-Sordo M., et. al. Epilepsy surgery involving the sensory-motor cortex. Brain. 2006; 129: 3307-3314.
Although surgery for medial temporal lobe epilepsy is widely accepted as a safe and effective means of controlling seizures and improving quality of life, surgery for extratemporal epilepsy is more complex and less well-studied. In particular, seizures arising in Rolandic cortex can be quite difficult to control because of the high risk of neurological deficit. In this current study the authors report a series of 52 patients with seizures arising from the sensory-motor strip that underwent surgery to control their seizures. The etiology of the seizures was diverse, including tumors (50%), vascular lesions (15%), cortical dysplasia (12%), Rasmussen's encephalitis (6%), and a variety of other etiologies, such as mitochondrial encephalopathy. All patients had electrocorticography (ECoG) to identify the area of interictal spiking at the time of surgery and stimulation mapping to identify Rolandic cortex. An unclear, but apparently small, subgroup of patients also underwent chronic subdural recordings to localize ictal onsets. Surgery consisted of lesionectomy, when appropriate, and additional removal of epileptogenic cortex. As indicated by the ECoG, peri-Rolandic tissue was resected, as was the inferior portion of the motor strip, and multiple subpial transections (MSTs) were performed when epileptogenicity was identified in the middle or superior Rolandic cortex. Of note, pre-operative scalp electroencephalography (EEG) demonstrated spikes outside Rolandic cortex in 50% of the patients, of which 24% were multifocal and generalized.
The authors report worthwhile improvement (defined as Engel outcome grade I-III) in 75% of patients, although only 31% were seizure-free. Predictors of better outcome were localized ECoG spikes, absence of post-resection spikes, and patients who underwent lesionectomy alone or in combination with corticectomy, as opposed to MSTs. Neurological deficits occurred in 50% of patients, of which 50% were mild. Deficits were more frequent in patients operated on after age 25.
Commentary
The authors of this article ultimately advocate a cautious approach to surgery in Rolandic cortex based on their limited ability to render patients seizure-free and the not insignificant risk for post-operative neurological deficits. However, the group of patients presented in this article represents such a heterogeneous population that it is difficult to draw any firm conclusions from this data. Patients with lesional epilepsy, which make up a significant proportion of this sample, are quite different than patients with non-lesional epilepsy. Not only is it well-known that rates of seizure-freedom are much higher after lesional compared with non-lesional epilepsy surgery, but the surgical approach itself and the outcome are often dictated by the pathology rather than the physiology. For example, one cannot partially resect a vascular malformation to preserve cortical function. Likewise, a tumor can re-grow after surgery causing recurrent seizures and neurological deficits regardless of the adequacy of the initial surgical resection. Patients with Rasmussen's encephalitis will likely fail surgery if a hemispherectomy is not performed. A metabolic encephalopathy is generally not a cause for focal epilepsy.
In addition, many of the patients in this study had multifocal epilepsy, which in some centers would have eliminated them from being considered for epilepsy surgery. It would be useful for the authors to divide their patients into those in whom a palliative operation was performed, which was never intended to be curative, versus those in whom seizure-freedom was actually a goal of surgery. Whereas worthwhile improvement from a palliative operation might be considered a success, the same outcome after a surgery intended to be curative might be considered a failure.
Another limitation of this study was the institutional bias towards ECoG to identify epileptogenic cortex. In other centers, all cases of neocortical epilepsy are investigated with chronic subdural electrodes to clearly identify the site of ictal onset. Although the ictal onset zone is generally included within the area of interictal spiking, this is not always the case. Therefore, the authors may not have completely identified the area of seizure onset in all patients.
In spite of these limitations, there is still useful information in this article. Patients with lesional or focal neocortical epilepsy will have a better outcome after surgery than those with non-lesional or multifocal epilepsy. Younger patients, on the whole, are better candidates for epilepsy surgery. Hence, it is critical to identify patients with medically intractable epilepsy who might be candidates for surgery as early as possible and refer them to specialized epilepsy surgery centers that have significant experience evaluating and treating this complex, heterogeneous group of patients.
Surgery for epilepsy in and around sensory-motor cortex can be effective in controlling seizures, but mild post-operative neurological deficits are not uncommon in patients operated on after age 25.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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