Abstracts

RATIONALE: Yawning has been observed as an ictal phenomenon in animal studies. Yawning is induced in rats by electrical and chemical stimulation of the paraventicular nucleus of the hypothalamus and is blocked by lesions of the hypothalamic-septal-hippocampal pathways. In cats, increased hippocampal activity is seen 1-3 seconds before spontaneous yawning. Yawning has not been previously described as an ictal manifestation in humans. METHODS: A 23 year old man with a history of left temporal ganglioglioma complained about the new onset of uncontrollable episodes of yawning after his third resective surgery for intractable complex partial seizures. The yawning spells, which prevented the patient from leading a normal life, occurred up to once an hour and lasted up to 20 minutes. To determine the nature of these spells, an ictal SPECT scan was obtained after i.v. injection of 18.2 mCi of technetium99 23 seconds after onset of yawning. . An ictal MEG was obtained by using a 148 channel BTi Magnes 2500 WH biomagnetometer. A single equivalent current dipole model with a correlation cutoff of 97% and an amplitude cutoff of 350 fTesla resulted in a single dipole, which was projected on a brain MRI of the patient. RESULTS:The subtracted ictal SPECT scan showed a focal area of increased activity in the left anterosuperior temporal cortex. The dipole calculations of ictal MEG resulted in a single dipole with a maximum in the left mesiotemporal region. In contrast, 25 yawning spells monitored with closed circuit video and electroencephalogram (EEG) telemetry were not associated with any changes in the EEG. The interictal EEG showed a left midtemporal breach rhythm with associated focal slowing in the delta range and occasional left midtemporal sharp waves. CONCLUSIONS:Yawning may be a manifestation of temporal lobe seizures as documented by focal left temporal activity in ictal SPECT and MEG in the reported patient. This is consistent with prior animal studies reporting a role of the hippocampus in the initiation of yawning. Ictal SPECT and MEG are able to demonstrate focal epileptic activity even when electrical activity cannot be recorded by scalp electrodes.