How to measure fatigue in epilepsy? The validation of three scales for clinical use

Fatigue can be defined as extreme and persistent tiredness, weakness or exhaustion that could be mental, physical or both. The main objective of this study is to validate three instruments to measure fatigue (Fatigue Symptom Inventory--FSI, Fatigue Assessment Instrument--FAI, Fatigue Severity Scale--FSS) in patients with epilepsy (PWE). We used concurrent validity as a method of validation. Reliability of the fatigue scales was assessed in PWE. We applied the three selected questionnaires plus the Beck Depression Inventory (BDI) in PWE, healthy volunteers (HV) and patients with other neurological conditions. We studied 67 PWE, 34 HV and 56 patients with different neurological conditions. The mean fatigue scores in each group were as follows: (a) for the FSS, the score in HV was 2.6±1.1, in PWE 4.2±1.5, in Patients with multiple Sclerosis (PMS) 4.8±1.4, in Patients with Migraine (PWM) 4.4±1.9, in Patients with radiculopathy (PR) 4.5±0.9. (b) For the FSI, the score in HV was 2.2±1.3, in PWE 3.9±2.3, in PMS 4.1±1.9, in PWM 4.5±2.5, and in PR 5.4±1.4. (c) For the FAI in HV was 3.0±1.1, in PWE 4.2±1.3, in PMS 4.5±0.9, PWM 4.3±1.5, and in PR 4.4±1.4. The correlation between the BDI and the FSS was 0.52 (p<0.001), between the BDI and the FSI was 0.62 (p<0.001), and between the BDI and the FAI was 0.54 (p<0.001). Patients with epilepsy have consistently higher fatigue scores compared healthy controls, and scores that are comparable with other neurological conditions. The FSI, FAI and FSS display concurrent validity and high intra-observer reliability in PWE, indicating that these scales could be utilized for further study of fatigue in epilepsy.