Reversible visual pareidolia and ictal bradykinesia associated with a left parieto-occipital cavernous malformation: illustrative case.

backgroundVisual pareidolia-the meaningful reinterpretation of ambiguous visual stimuli-is a rare but recognizable manifestation of cortical irritation. Its occurrence as a focal ictal symptom of cerebral cavernous malformation (CCM) has not been previously documented. OBSERVATIONS: The authors report the case of a 36-year-old male with chronic drug-resistant epilepsy who presented with stereotyped paroxysmal episodes of perceiving inanimate objects (plastic bags) as cats, accompanied by subjective ipsilateral hand slowing. Preoperative MRI demonstrated a 10 × 7-mm hemosiderin-rimmed nodular lesion at the left parieto-occipital junction, consistent with CCM. Preoperative EEG showed reactive parieto-occipital alpha activity with persistent left frontotemporal sharp-wave discharges. Neuronavigation-guided prone position transcortical microsurgical resection achieved gross-total lesionectomy. The patient experienced immediate, complete resolution of visual pareidolia and ictal bradykinesia postoperatively. Histopathological analysis confirmed CCM. Postoperative EEG, however, revealed persistence of left frontotemporal sharp-wave activity, indicating an established secondary epileptogenic network. LESSONS: Excision of CCM at the parieto-occipital junction is effective in resolving higher-order perceptual seizure semiology, with sustained remission beyond 6 months. Persistent postoperative EEG abnormalities emphasize the need for continued antiseizure therapy even after clinically successful lesionectomy. https://thejns.org/doi/10.3171/CASE26344.