During stage 2 sleep the thalamic reticular neurons release GABA, allowing sleep spindles to emerge at an oscillatory frequency of 12-14 Hz.There is evidence from from thalamic kindling in cats that spindle oscillations develop into seizures in corticothalamic systems. From computer modeling it is hypothesized that that there is cortical transformation of one of every 2 or more spindle waves to a spike component of spike and wave discharges and the other replaced by a slow wave1. This model predicts the evolvement of spindle waves to seizures.We pondered on the predictive relationship between spindle characteristics among different types of epilepsy and compared them to subjects without epilepsy.
7 patients, each, with temporal lobe epilepsy, frontal lobe epilepsy, primary generalized epilepsy and 5 subjects without epilepsy were studied after IRB approval. At the time of EEG recordings 4 out of 5 normals were on benzodiazepines while the rest were on antiepileptic medications. From the whole night EEG recordings, segments of 300 seconds were extracted to assess spindle duration, number of spindles and fraction of spindle time per Epoch of stage 2 sleep by 2 independent scorers blinded to the clinical information. A 2 way ANOVA was used to test the differences between the various frequency categories.
See attached table.
1.More spindles were seen in normal subjects. This represents medication effect on sleep.2. Although mean spindle duration and fraction of spindle time per epoch of stage 2 sleep occurred more in temporal lobe epilepsy, this was not statistically significant. 3.Overall spindle characteristics are not discriminative between the various types of epilepsy.
In studying patients with epilepsy in the sleep laboratory, the morphology of spindles is unlikely to offer clues to assess either the origin or activity of spike and wave discharges.1. Traub RD, Contreras D et al. Single- column thalmocortical network model exhibiting gamma oscillations, sleep spindles and epileptogenic bursts. J Neurophysiol. 2005; 93:2194-232.
NormalGeneralizedTemporallobeFrontallobepMean spindle duration in seconds (±SD)0.69±0.240.72±0.211.47±1.120.63±0.210.37Spindle time /epoch in stage 2 sleep0.03±0.020.02±0.030.05±0.080.02±0.010.84Spindle number per epoch3.4±3.32.8±2.82.6±2.23.4±1.80.37
Juliana Rajter, None.