Abstracts

RATIONALE: Vagus nerve stimulation (VNS) has emerged as adjunctive therapy in the management of epilepsy. The use of VNS has expanded beyond epilepsy centers into general neurology practice since a comprehensive evaluation is not required prior to implantation. However, approximately 20-40% of patients presenting with intractable seizures actually have non-epileptic events (NEE). Clinical description of seizure activity by witnesses and patients form the basis of the diagnosis in the outpatient setting, the accuracy of which is limited. In order to increase awareness of the consequences of circumventing a comprehensive epilepsy evaluation in making these decisions, we present two patients with NEE in whom VNS was initiated.
METHODS: After approval by the IRB, the EEG database at the Mayo Clinic was reviewed for all patients with VNS examined in the Epilepsy Monitoring Unit between 1998 and 2001in whom NEE were recorded.
RESULTS: Two patients were identified. The first patient reported daily spells over the last 5 years consisting of of chest pain or headache, progressing to asynchronous limb shaking, with occasional tongue bite and incontinence. These were diagnosed as epileptic seizures elsewhere after video-EEG monitoring and remained refractory to multiple trials of anti-epileptic drugs (AEDs). A VNS was placed in 1999 with complete control for 6 months. After January 1, 2000, seizures returned, attributed to Y2K effect by the patient. Subsequent AED and VNS adjustments were unsuccessful. After admission to the video-EEG monitoring unit, all of the patient[ssquote]s habitual events were recorded which were clinically and electrographically consistent with NEE. A comprehensive psychiatric evaluation diagnosed panic disorder and PTSD. Behavioral and medical therapy was successful. At four months follow up, she was event free with the device turned off.
The second patient developed stereotyped events at age 14 described as generalized tonic clonic seizures. They previously occurred one to three times per year, but increased to two per week at age 48 resulting in medical disability. AEDs were ineffective and a VNS was placed elsewhere without prior video-EEG monitoring. This resulted in fewer generalized seizures, but a new spell type emerged, consisting of facial tingling progressing to flaccid unresponsiveness, occurring several times a day. These were followed by extreme headache requiring narcotics. At age 54, the patient was admitted to our monitoring unit. All of his habitual events were recorded which were clinically and electrographically consistent with NEE. The patient did not accept the diagnosis, and elected to continue his AED.
CONCLUSIONS: VNS is increasingly used by general neurlogists as well as epileptologists in the treatment of refractory epilepsy without standardized evaluation. These cases illustrate a pitfall of this process. Rrequiring video-EEG monitoring prior to implantation may not insure proper diagnosis. In light of the known limitation of the device, the decision to start VNS therapy is best made following comprehensive evaluation at an epilepsy center with large patient numbers, in which a variety of treatment options are available.