Case Report Of Successful Gamma Knife Stereotactic Radiosurgery Treatment For Previously Medically Intractable Heterotopia Based Seizure Disorder

Keywords: epilepsy, gamma knife, seizures, outcome, radiosurgery

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     Mesial temporal lobe epilepsy is a condition often successfully treated with medication and/or neurosurgical intervention. Temporal lobectomy and amygdalohippocampectomy is the usual surgical procedure for individuals with medically intractable seizures, although trials are currently ongoing to examine the efficacy of gamma-knife stereotactic radiosurgery (GK-SRS) for this refractory condition.
     In contradistinction, little is known regarding the use of GK-SRS for medically refractory, surgically inoperable, heterotopia based epilepsy.
     A 44 year old right handed female presented to our medical center with a 20 year history of medically intractable complex partial seizure disorder; averaging 3-4 seizures per week.
     Epilepsy monitoring unit stay with video electroencephalography could only localize epileptiform to the right hemisphere. MRI imaging identified a right lateral periventricular heterotopia. Extensive grid and depth electrode investigation revealed the entire ventricular heterotopia as electrographically active. Its extent however did not allow for surgical extirpation. The heterotopia was targeted for GK-SRS by dividing it into a superior component which received 16 x 8 mm collimator shots, and inferior component which received 10 x 8 mm collimator shots. Both were prescribed 18 Gy to the 50%IDL with 99% of the superior component receiving 20 Gy while 98% of the inferior target received 20 Gy.
     Six weeks following GK-SRS the patient reported her last seizure. This has been a durable effect for the last 14 months.
     This is a retrospective study.
     The follow-up time and single patient treated preclude robust predictions regarding the general applicability of GK-SRS in the treatment of medically refractory, surgically inoperable, heterotopia based seizure disorders.
     Nevertheless, our initial experience with 14 month seizure-free follow-up is extremely encouraging and warrants further large scale study.


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