Rare diseases · Sign or symptom

Increased theta frequency activity in EEG

HP:0031535

What it means

Increased frequency of theta wave activity in the electroencephalogram. Theta waves have a frequency of 3.5-7.5 Hertz, and are present in very small amounts in healthy waking adult EEGs. Theta activity is normal in small very amounts in the healthy waking adult EEG in a symmetrical distribution.

Rare diseases that can present with this4

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Increased theta frequency activity in EEG

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This page uses the Human Phenotype Ontology (2026-06-23) — Human Phenotype Ontology Consortium, hpo.jax.org. Disease associations from Orphanet (INSERM), CC BY 4.0. Content is educational and is not medical advice.