SAN DIEGO—Vagus nerve stimulation (VNS) may help patients with refractory status epilepticus gain better seizure control, researchers reported at the 66th Annual Meeting of the American Epilepsy Society. The treatment may help some patients become seizure free, but it may not provide clinical benefits to others.

VNS May Reduce Seizure Length and Frequency
After a one-year dose-escalation period and six months of VNS, patients with refractory status epilepticus had spike-free intervals on their EEGs, said Christine Dean, MD, Director of the Epilepsy Institute of North Carolina in Winston Salem. After one year of VNS, the EEGs showed increased periods of spike-free intervals, and the duration of spikes and waves decreased. The patients did not show clinical improvements or recover function, however.

The results are part of a 10-year study of 550 patients with epilepsy, including 220 mentally challenged individuals and 330 cognitively normal individuals, who underwent VNS implantation. After one year of dose escalation, seizures were reduced by 68% in mentally challenged patients and by 59% in normal patients.

At one year, Dr. Dean and her colleagues identified 15 mentally challenged patients and 16 cognitively normal patients who had not responded to VNS. The nonresponders had an average of 15 clusters or prolonged seizures per year that required hospitalization, despite continuous VNS. EEG patterns indicated that the individuals had subclinical status epilepticus.

The patients had been taking an average of three antiepileptic drugs and had similar seizure etiology (eg, migrational disorders, encephalitis, and birth defects). The individuals were not candidates for epilepsy surgery and they continued VNS treatment. The researchers performed EEGs on the nonresponders at three, six, and 12 months after the one-year dose-escalation period.

“The pattern that’s established by the VNS is reliable. It’s just variable according to the patient’s brain, and maybe the stimulation parameters,” Dr. Dean told Neurology Reviews. “The clinical picture should definitely change if the brainwave becomes quiet and everything else remains stable,” she added. “Sooner or later, they are going to wake up. They’re not going to look so drowsy.” If patients’ seizures continue to become shorter and less frequent, the investigators will reduce the patients’ polytherapy. “If we can do that, we can save health care dollars,” Dr. Dean concluded.

VNS May Help Patients Become Seizure-Free
Two of five patients with refractory status epilepticus achieved seizure freedom within seven days of VNS implantation, said David Donahue, MD, a neurosurgeon at Cook Children’s Medical Center in Fort Worth, Texas. The remaining three patients had persistent refractory status epilepticus that lasted between 21 and 84 days. After more than six years of VNS therapy, these patients had achieved better seizure control but had not become seizure-free.

Dr. Donahue and his colleagues retrospectively reviewed data for children with refractory status epilepticus who were considered to be candidates for VNS from 2003 through 2011. Among the variables that the researchers examined were the precipitating factors for status epilepticus, the duration of refractory status epilepticus before VNS, the age at implantation of VNS, the number of anticonvulsants administered before VNS, the duration of refractory status epilepticus after VNS, VNS stimulation parameters, and outcomes.

Five patients with status epilepticus received VNS implantation between January 2003 and January 2011. Their median age at implantation was 5. The investigators initially used an output current of 0.25 mA, a frequency of 30 Hz, and a pulse width of 250 µs. Therapy began with a repeated cycle of 30 seconds of stimulation, followed by three minutes of off time.

Viral encephalitis was the precipitating factor for three cases of status epilepticus. Anticonvulsant withdrawal and metabolic complications, respectively, precipitated the other two cases. Three patients had a new-onset intractable seizure, and two had a history of seizures. Three patients had used 10 or more antiepileptic drugs, and two had used six or seven of these medicines.

Patients’ median length of stay in the medical center was 131 days, and their median stay before implantation was 26 days. Three patients remained in the medical center for 105 days or more following VNS implantation. One patient remained in the center for 35 days after implantation, and one patient remained in the center for one day after implantation.

“This case series … suggests that VNS may have a role in the interruption of refractory status epilepticus and prevention of its recurrence in patients who fail heroic medical treatment,” said Dr. Donahue. “VNS could be considered as a reasonable treatment option for this acute life-threatening event. Aggressive adjustment of stimulation parameters may contribute to response, though the contribution of individual parameters to outcome is unknown,” he concluded.

—Erik Greb
Senior Associate Editor

Vagus Nerve Stimulation for Refractory Status Epilepticus?