Video Electroencephalographypolysomnography

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As mentioned earlier, paroxysmal events in sleep characterized by prominent motor activity or complex behavior may represent manifestations of epileptic seizures or sleep disorders and on rare occasions psychogenic seizures. Frequently, it may be difficult to make a definitive clinical diagnosis based solely on the history. In this situation, video EEG-PSG may prove extremely valuable in defining the nature of the paroxysmal events. If one of the recurrent episodes is recorded, careful analysis of the clinical semiology may allow one to determine if the event is consistent with epileptic seizure, parasomnia, or psychogenic seizure. However, at times, the exact nature of the episode may prove very difficult to distinguish solely on the basis of the clinical features. Simultaneous recording of the EEG may demonstrate associated ictal epileptiform activity, allowing one to identify the epileptic nature of the recorded behavior. This is particularly true for seizures originating from the supplementary sensorimotor area that may be characterized by bilateral extremity and truncal thrashing movements and vocalizations associated with preserved consciousness.

In the evaluation of these episodes, because of the absence of associated changes in the EEG recording, these episodes were initially thought to represent a sleep disorder, which was termed nocturnal paroxysmal dystonia (Lugaresi et al., 1981). However, it was later recognized that these patients with nocturnal paroxysmal dystonia were in fact patients with SSMA seizures with the ictal EEG activity restricted to the mesial aspect of the superior frontal gyrus and thus frequently not seen in the scalp EEG recordings (Bleasel and Morris, 1997). There may be prominent EMG activity during the seizures, which may obscure the EEG tracing, making it difficulty to discern the presence of any associated ictal EEG pattern. Frequently, the ictal EEG may be characterized by low-amplitude, fast activity, restricted to the vertex region, making it difficult to recognize. Utilization of a transverse montage may facilitate the recognition of this ictal pattern. At times, these patients have also been misdiagnosed as having psychogenic seizures because of the presence of prominent asymmetrical motor activity in conjunction with retained consciousness without any recognized changes in the EEG recording.

In a study of the diagnostic value of video EEG-PSG, Aldrich and Jahnke (1991) reviewed their experience with 122 patients who presented with suspected parasomnias and subsequently underwent video EEG-PSG monitoring (Table 16.1). The patients were divided into three groups. Group I consisted of 59 patients presenting with prominent motor activity without a prior diagnosis of epilepsy. Group II consisted of 27 patients presenting with minor motor activity without a prior diagnosis of epilepsy. Group III, 36 patients with known epilepsy, had unexplained movements occurring in sleep. Table 16.1 displays the patients evaluated. The video EEG-PSG study resulted in a definitive diagnosis being made in 43 (35%) of the 122 patients. It is interesting that approximately half the patients with motor events in sleep had a final diagnosis of epileptic seizures, while approximately half were given a diagnosis of a parasomnia. It is also important to note that three patients were diagnosed as having psychogenic seizures. The video EEG-PSG studies supported a specific diagnosis of epilepsy, parasomnia, or psychogenic seizures in another 37 (30%) of patients. The studies were inconclusive in 42 (34%) of the 122 patients.

We have reported on a group of six infants and children who presented for evaluation of apnea and in whom a combined video EEG-PSG study was performed (Kotagal and Dinner, 1991). In three of the six patients, the apnea represented a manifestation of an epileptic seizure. Zucconi and colleagues (1997) reported on two adults who presented with a history of awakening from sleep with a sensation of choking and abnormal motor activity as well as daytime sleepiness, and who had been previously diagnosed with obstructive sleep apnea. These patients underwent video EEG-PSG and were found to have

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