Doctors, in a patient with suspected sporadic fatal insomnia, cognitive and autonomic issues and extreme insomnia, what can an eeg (electroencephalography) test alone detect? thank you

Fatal insomnia: Fatal insomnia is caused by prion. It has two forms: familial and sporadic. EEG is usually abnormal but nonspecific showing slow wave pattern. Diagnosis of fatal insomnia is made by clinical, sleep study, PET-scan and genetic study (specific D178N PRNP gene mutation, especially in familial form). Sometimes, prion protein can be detected in CSF, but often not sensitive enough.