Convulsive syncope following placement of sphenoidal electrodes

Area of Science:

• Neurology
• Cardiology
• Medical Devices

Background:

• Sphenoidal electrodes are used in electroencephalography (EEG) to record brain activity.
• Insertion of sphenoidal electrodes is generally considered a safe procedure.

Observation:

• Two patients experienced convulsive syncope shortly after sphenoidal electrode insertion.
• Episodes included behavioral arrest, loss of muscle tone, posturing, and extremity jerking.
• These events were initially misdiagnosed as psychogenic seizures.

Findings:

• EEG revealed diffuse slowing and generalized suppression of rhythms during the episodes.
• EKG monitoring showed bradycardia followed by brief asystole in both cases.
• The syncope events were clinically different from the patients' usual seizure patterns.

Implications:

• Vagally mediated cardioinhibitory reactions represent a rare but serious complication of sphenoidal electrode placement.
• Fear, pain, and trigeminal nerve stimulation may trigger these reactions.
• Clinicians should be aware of this potential adverse event during electrode insertion procedures.