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Case Reports
. 2020 Oct 22;6(10):e05324.
doi: 10.1016/j.heliyon.2020.e05324. eCollection 2020 Oct.

Long-term outcomes of two patients with progressive myoclonic epilepsy treated with vagus nerve stimulation therapy

Ayataka Fujimoto  1 , Tohru Okanishi  1 , Keishiro Sato  1 , Hideo Enoki  1
Affiliations
Case Reports

Long-term outcomes of two patients with progressive myoclonic epilepsy treated with vagus nerve stimulation therapy

Ayataka Fujimoto et al. Heliyon. .

Abstract

Purpose: Long-term outcomes associated with vagus nerve stimulation (VNS) therapy for progressive myoclonic epilepsy (PME) have not been studied. The purpose of this study was to report long-term outcomes of VNS therapy in two patients with PME.

Methods: We performed VNS therapy for two patients with PME. We reviewed the conditions of epileptic seizures, status epilepticus (SE), myoclonus, and Karnofsky performance state (KPS) scale scores at baseline and after 10 years.

Results: A 16-year-old boy with myoclonic epilepsy with ragged-red fibers (MERRF) underwent VNS therapy. Baseline KPS scale score was 50, seizure frequency was weekly, and SE occurred yearly. At 23 years old, KPS scale score was 10. He had remained SE-free and frequency of epileptic seizures had markedly reduced. At 24 years old, he died due to pneumonia. A woman with Gaucher's disease type III underwent VNS therapy at 20 years old. Baseline KPS scale score was 80, seizure frequency was daily, and SE occurred monthly. At 30 years old, KPS scale was 30. She remained SE-free, but still experienced epileptic seizures yearly. Both patients became lethargic during VNS-off periods, with symptoms improving to baseline levels when VNS was resumed.

Conclusion: Long-term outcomes with VNS showed good epileptic seizure control and freedom from SE. VNS might help maintain level of consciousness.

Keywords: Behavioral neuroscience; Cognitive neuroscience; Consciousness; Epileptic seizure control; Long-term outcome; Neurology; Neuroscience; Neurosurgery; Pediatrics; Progressive myoclonic epilepsy (PME); Rehabilitation; Vagus nerve stimulation (VNS).

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Figures

Figure 1
Figure 1
Ragged red fibers in Patient 1 (Gomori trichrome stain). Ragged red fibers (arrows) appear as red-stained structures in the myofiber membrane.
Figure 2
Figure 2
Follow-up neuroimaging. A) Brain of Patient 1 in 2009 and 2016. B) Brain of Patient 2 in 2011 and 2019. No obvious progression of atrophy is seen in either patient. Computed tomography was performed in Patient 1 as the generator for vagus nerve stimulation had not received approval for magnetic resonance imaging in Japan at the time of imaging.
Figure 3
Figure 3
Clinical courses. Epileptic seizures started at 12 years old in Patient 1 and at 13 years old in Patient 2. After vagus nerve stimulation therapy (VNS), both remained free from status epilepticus. Frequencies and intensities of generalized seizures improved after VNS. While VNS was off, patients became more lethargic, but returned to baseline level of consciousness when VNS was restarted. VNS: vagus nerve stimulation; KPS: Karnofsky performance state scale; LEV: levetiracetam; TPM: topiramate; CZP: clonazepam; VPA: valproic acid.
See this image and copyright information in PMC

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