What EEG findings are characteristic of subacute spongiform encephalopathy>?

Updated: Oct 09, 2019
  • Author: Eli S Neiman, DO, FACN; Chief Editor: Selim R Benbadis, MD  more...
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Aguglia et al described 20 patients with subacute spongiform encephalopathy and periodic paroxysmal activities in the EEG. Evolution of clinical and EEG abnormalities were analyzed in all 20 (16 pathologically confirmed). Illness duration was less than 4 months in 65% and greater than 17 months in 10%. The early clinical stage was characterized by gradual gait disturbances, mental deterioration, and sensory or autonomic changes. In 10 EEG recordings from 7 patients examined in the early clinical stage, no periodic discharges were present. [47]

Early periodic paroxysmal activity appeared within 12 weeks of the onset of the disease in 88% of the patients who underwent EEG recordings. This early periodic paroxysmal activity usually occurred at an intermediary stage, when the patients demonstrated marked worsening of the clinical picture. Focal, segmental, and/or generalized myoclonic jerks were observed in 15%, 53%, and 100% of cases at prodromal, intermediary, and terminal stages, respectively. Different kinds of periodic paroxysmal activity were observed:

  • Biphasic or triphasic periodic complexes

  • Periodic complexes with multiphasic configuration

  • Periodic polyspiking discharges

Abnormal "pacing" by slowly repeated flashes was found in 4 patients presenting with visual hallucinations or cortical blindness. Burst-suppression activity was observed frequently in the terminal stage in decorticate patients.

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