Fig 1.
Typical EEG findings in Lassa fever patients and misinterpretation pitfalls in the resource-limited LF isolation ward setting.
(A) EEG of a 32-year-old male LF patient showing theta frequency background slowing (6 Hz) with reversed anterior-posterior gradient. (B) Typical intermittent, high-amplitude, frontally predominant, 2.5 Hz generalized rhythmic delta activity in the EEG of a 31-year-old male patient. (C) Severe artefact overlay (muscle artefacts in T4 and T6, T3 electrode artefacts and electrical disturbances in the frontal electrodes) make this otherwise normal EEG largely unreadable. (D) F3 electrode artefact which can be confused with focal epileptiform discharges as seen in patients with focally triggered seizures as a sign of increased seizure susceptibility. (E, F) Same EEG section with incorrect (E) and correct (F) time constant and high-frequency filter settings. Incorrect filter settings simulate better recording quality by masking certain artefacts: A falsely reduced time constant of 0.03 seconds masks sub-delta activity, like sweat artefacts (C3, P3, and F4), by smoothing the EEG baseline. A high-frequency filter incorrectly lowered to 15 Hz reduces high-amplitude electrode artefacts, promoting a potential misinterpretation of epileptiform potentials as demonstrated by the F4 electrode artefact. (G) Eyelid-related eye artefacts can be mistaken for bifrontal delta activity in the absence of EOG. (H) EEG without abnormalities in appropriate recording quality after numerous adjustments of our EEG setup, correct filter setting application (time constant 0.3 s; high-frequency filter 70 Hz), and EOG addition.