Radiosurgery for the treatment of dominant hemisphere periventricular heterotopia and intractable epilepsy in a series of three patients

Abstract

Periventricular heterotopia (PVH) is a neuronal migration disorder characterized by masses of gray matter located along the lateral ventricles that commonly cause epilepsy. The benefit of surgical resection of the PVH has been demonstrated in case reports to date; however, the location of the PVH in the paratrigonal region of the lateral ventricles can present significant surgical challenges. Noninvasive modalities of ablating this epileptogenic focus must therefore be considered. We present a small series of three patients who underwent stereotactic radiosurgery (SRS) for inoperable unilateral dominant hemisphere PVHs in order to illustrate the potential benefits and risks of this treatment modality. A total dose of 37.5-65 Gy resulted in seizure freedom for at least 14 months at the time of their last follow-up, even in patients harboring a second independent epileptic focus. Whether intracranial electrode recording truly offers added value is therefore uncertain. The two patients who received higher radiation doses suffered from symptomatic radiation necrosis and associated cerebral edema, requiring further medical intervention, and persistent monocular visual loss in one patient. While a longer interval prior to re-treatment may have been attempted, neither patient demonstrated radiographic findings typically associated with seizure remission. Refractory epilepsy due to PVH may be successfully treated with radiation therapy; but further work is needed to define the optimal dosing parameters in order to lower toxicity to normal tissue.

Keywords: Epilepsy; Periventricular nodular heterotopia (PVH); Radionecrosis; Stereotactic radiosurgery (SRS).

Fig. 1

A: T1 MRI demonstrating PVH in the left trigone. B: T2 Coronal MRI status-post implantation of intracranial electrodes. C: Dose plan for Case 1. D: Axial T2 MRI showing left trigone PVH.

Fig. 2

A: Coronal T2 MRI showing left trigone PVH. B: CT scan demonstrating cerebral edema from radiation necrosis. C: Dose plan for initial LINAC treatment for Case 2. D: Dose plan for second LINAC treatment for Case 2.

Fig. 3

A: Post-operative coronal T1 MRI showing depth electrodes. B: Dose plan for Case 3. C: Axial FLAIR MRI at 19 months post-treatment showing radiation necrosis.