Epileptic mechanisms in Charles Bonnet syndrome

Epileptic phenomena are usually not considered a possible cause of prolonged hallucinatory states such as Charles Bonnet syndrome (CBS). A 65-year-old woman with previous right hemorrhagic strokes developed complex visual hallucinations (CVHs), featuring CBS, and delayed palinopsic phenomena, along with new neurological signs and worsening of existing deficits. Video/EEG/polygraphy monitoring revealed the presence of right-sided periodic lateralized epileptiform discharges of the "plus" type (PLEDs plus) and documented a focal seizure in close relation to a delayed palinopsia episode. Adjustment of antiepileptic drug treatment led to remission of the CVHs with simultaneous disappearance of PLEDs plus and epileptic seizures and return to previous neurological status. We discuss the role of continuous (PLEDs plus) and intermittent (focal seizures) epileptic activities in this episodic form of CBS, considering current theories on the genesis of CVHs. EEG assessment is recommended if CBS develops in a patient with unexplained worsening of existing neurological signs.