Michael 1993.
| Methods | Randomised, controlled, double blind, active‐control study of patients with refractory partial seizures. Pre‐randomisation baseline period: 12 weeks. Duration of treatment: 14 weeks. Efficacy was determined at the end of the acute phase. At the end of the 14 week double‐blind phase patients entered an extension phase in which low stimulation patients were switched to high stimulation. |
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| Participants | A multi‐centre trial (USA). 22 people randomised. High stimulation group: 10 participants. Low stimulation group: 12 participants. Mean age 32 years (range 15‐56); seizure frequency 2 per day; mean duration of epilepsy 19 years (range 5‐32). |
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| Interventions | Comparison of high (output current 1.0‐3.0 mA, on/off time 30 s/5 min, frequency 30 Hz, pulse width 500 µs) and low (output current 0.25‐0.5 mA, on/off time 30 s/60‐90 min, frequency 1 Hz, pulse width 130 µs) stimulation in treatment of refractory partial seizures. All patients had an identical implantation of the vagus nerve stimulation device (NeuroCybernetic Prosthesis, Cyberonics). |
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| Outcomes | Primary outcome: Seizure frequency (mean seizure frequency percent reduction).
Secondary outcomes: a) Dropouts. b) Adverse events. |
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| Notes | Supported by Cyberonics, Inc., Webster, TX. | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | Method of randomisation not specified. |
| Allocation concealment (selection bias) | Unclear risk | No information provided. |
| Blinding of participants and personnel (performance bias) All outcomes | Unclear risk | No details provided. |
| Blinding of outcome assessment (detection bias) All outcomes | Unclear risk | No details provided. Identical implants used. |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | All participants were included in the analysis. |
| Selective reporting (reporting bias) | Unclear risk | Protocol unavailable, but appears all expected and pre‐specified outcomes are reported. |
| Other bias | Unclear risk | All studies are sponsored by Cyberonics, the manufacturer of the device. |