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Cortical dysplasia is increasingly being recognised as an important cause of partial seizures including epilepsia partialis continua. With the advent of high resolution MRI it is now often possible to identify areas of cortical dysplasia, increasing the possibility of neurosurgical intervention when seizures are refractory to medical treatment. We present a patient with intractable epilepsia partialis continua due to cortical dysplasia that was refractory to all medical treatments, was not evident on MRI, and was dramatically improved by multiple subpial transections.
A 19 year old man who was the product of an uneventful pregnancy with no perinatal problems and normal early milestones developed simple partial seizures at the age of 14 years. These comprised clonic movements of the left side of his face, left arm, and left leg. Brain MRI was reported as normal and an EEG showed a right frontoparietal focus. Carbamazepine was started at a dose of 800 mg daily and he remained seizure free for a year. A subsequent recurrence of the left sided simple partial seizures responded to the addition of phenytoin (300 mg daily). Over the next four years there was reduced academic attainment but seizures were infrequent. At the age of 19 he developed clonic movements of the right side of his face and right arm. These partial seizures increased in frequency and after a week he was admitted to his local hospital with epilepsia partialis continua comprising continuous motor seizures of the right side of his face and right arm. There was no alteration of consciousness ictally but his seizures were sufficiently distressing to require sedation and ventilation. Several antiepileptic drugs were tried over a two month period without success, including phenytoin, phenobarbitone, sodium valproate, vigabatrin, and infusions of clonazepam, lorazepam, and diazepam. The patient was transferred to this hospital, ventilated, and sedated on a thiopentone infusion. On examination there was marked hepatosplenomegaly but no focal neurological deficit was evident. Investigations were aimed at identifying a progressive degenerative disorder in view of the cognitive decline, involvement of both hemispheres at different times, and the hepatosplenomegaly. A full metabolic screen was normal. Liver, bone marrow, skin, and muscle biopsies were non-contributory and a screen for mitochondrial DNA mutations was negative. The MRI was performed on a 0.5 T Vectra (GE) instrument with T1 and T2 weighted axial and coronal sequences including volume acquisitions, and again no abnormality was detected. His EEG showed spike and sharp waves over the left central cortex, and during seizures runs of repetitive polyphasic discharges were recorded. Electrocorticography and a biopsy of the left premotor cortex was performed. The cortex appeared macroscopically normal but electrocorticography showed polyphasic discharges over the area that was biopsied. Histological examination showed areas of focal cortical dysplasia with disordered cortical lamination, large dysplastic neurons occurring in clusters and aggregates of astrocytes (figure). During this period of investigation his seizures could only be controlled initially on a thiopentone infusion at doses sufficient to cause burst suppression on EEG. This resulted in impairment of liver function and coagulopathy and so was therefore replaced with a propofol infusion. High doses of up to 1000 mg/hour were required to control his seizures, but this was associated with prolongation of bleeding time and gastrointestinal haemorrhage and had to be discontinued. Other antiepileptic drugs were tried without success. Vigabatrin at a dose of <4g daily, carbamazepine <3g daily, gabapentin <2.4 g daily, piracetam <24 g daily, and acetazolamide <1 g daily did not control seizures. Phenytoin induced myelosuppression and was withdrawn. Some degree of control was obtained with a combination of ketamine, phenobarbitone, and midazolam but at doses that rendered the patient unconscious. In view of the intractable nature of the seizures and biopsy findings, multiple subpial transections were undertaken. Before the transections were performed high amplitude spikes were recorded over the left premotor and motor cortex on electrocorticography. Guided by the electrocorticography, multiple subpial transections were performed on the left precentral and postcentral gyri and after this the electrocorticography showed no epileptiform discharges. Postoperatively there was marked improvement in seizures, it was possible to discontinue intravenous antiepileptic drugs and the patient was extubated. The hepatosplenomegaly resolved. He subsequently had only a few brief self limiting clonic movements of the right arm. There was no neurological deficit attributable to the surgical procedure but rehabilitation was hampered by a critical illness polyneuropathy. Nine months after discharge he remains wheelchair bound but is beginning to mobilise, with no recurrence of his EPC.
Cortical dysplasia is increasingly being recognised as an important and treatable cause of partial seizures.1 2 There have recently been major advances in structural brain imaging that allow detection of cortical abnormalities with high resolution MRI,2-4 although a considerable proportion of cases are not identifiable.3 4
The histological diagnosis, complications, and failure of the patient to respond to pharmacological measures led us to perform multiple subplial transections with dramatic effect. The results of surgical treatment for cortical dysplasia depend on the site and grade of the lesion and type of procedure performed.4 The most established techniques are lesionectomy, resection of epileptogenic tissue as assessed by electrocorticography, or a combination of the two procedures. The use of multiple subplial transections has also been described5 and used in an attempt to avoid any deficit resulting from excision of primary sensorimotor cortex.5 6 This technique has been successfully used to end EPC due to Rasmussen’s syndrome,6 but this is the first reported case we are aware of in which it has been used as a treatment for intractable epilepsia partialis continua due to cortical dysplasia. The outcome in terms of seizure control was good and our patient was spared the hemiparesis that would have resulted from resection of the motor cortex. We conclude that multiple subpial transections should therefore be considered in patients with medically refractory EPC secondary to cortical dysplasia, even when structural imaging is unremarkable.