Latency of epileptic and psychogenic nonepileptic seizures

Due to their semiological similarities, psychogenic nonepileptic seizures (PNESs) can occasionally hardly be differentiated from epileptic seizures (ESs), and long-term video-electroencephalographic monitoring (VEM) is needed for the differential diagnosis.

Objective

To investigate the time of the first clinical event and its distribution on the days of VEM in ES and PNES patients.

Methods

In total, a consecutive series of 48 PNES and 51 ES patients matched for gender and age were retrospectively and consecutively evaluated. The time distribution of the seizures during the day was noted. Seizure latency was determined as the time in hours from the start of the video-electroencephalographic recording to the first clinical event.

Results

The seizure latency was significantly shorter in PNES patients compared to ES patients (p < 0.001). Seventy-two percent of PNES patients and 49.1% of ES patients had their first seizure in the 24 hours of video-EEG recording (p = 0.023). Recording longer than 48 hours was required for 12.5% of PNES patients and 37.3% of ES patients (p = 0.006). While ESs were almost evenly distributed throughout the day, most PNESs occurred during the evening hours (p = 0.011).

Conclusion

We observed that the PNESs appeared earlier than the ESs in the VEM and were concentrated during daylight hours. Although not strictly reliable, seizure latency can contribute to the differential diagnosis of ES and PNES.

Keywords
Psychogenic Nonepileptic Seizures; Epilepsy; Electroencephalography

		PNES group (n = 48)	ES group (n = 51)	p
Sex (n)	Female	32 (66.7%)	28 (54.9%)	0.304
Sex (n)	Male	16 (33.3%)	23 (45.1%)	0.304
Age (year)		32.8 ± 11.7	36.9 ± 15.1	0.09
Age at the onset of seizures (year)		27.5 ± 11.9	20.7 ± 16.1	< 0.001
Family history of epilepsy (yes/no)		11/ 37	12/ 39	0.1
Number of AEDs before VEM (n)		1.6 ± 0.9	2.2 ± 1.2	< 0.001
Duration of AED use (year)		3.88 ± 4.99	11.37 ± 9.83	< 0.001
Duration of VEM (day)		4.5 ± 2.4	5.6 ± 2.8	< 0.001
Number of seizures before VEM/year		122.6 ± 164.7	123.5 ± 154.4	0.218
Number of seizures in VEM/day		1.0 ± 1.3	1.5 ± 3.5	< 0.001
Onset time of the AED reduction (day)		1.1 ± 1.3	1.8 ± 1.4	0.006
Seizure latency (hour)		20.4 ± 24.2	45.8 ± 54.9	< 0.001
Seizure in the first 24 hours (yes/no)		35/13	25/26	0.023
Seizure in the first 48 hours (yes/no)		42/6	32/19	0.006
Seizure after 48 hours (yes/no)		6/42	19/32	0.006

Variables	Subjective (n = 29)	Akinetic (n = 46)	Minor motor (n = 26)	Hypermotor (n = 17)	p ^* * Kruskal-Wallis test.
Age (year)	26 (20–53)	37 (18–58)	38 (18–51)	26 (20–48)	0.771
Age at the onset of seizures (year)	21 (12–48)	32.5 (10–55)	23.5 (12–48)	22 (12–47)	0.784
Number of AEDs before VEM (n)	2 (0–3)	1 (0–3)	2 (1–3)	2 (0–2)	0.109
Duration of VEM (day)	4 (1–10)	3.5 (1–9)	5 (1–8)	4 (1–12)	0.307
Number of seizures in VEM/day	0.5 (0.2–1.5)	1 (0.2–5.0)	0.35 (0.1–7.0)	1 (0.2–1.7)	0.094
Onset time of the AED reduction (day)	1 (0–3)	0.5 (0–3)	0.5 (0–4)	1 (0–5)	0.863
Seizure latency (hour)	11 (1–70)	7.5 (1–89)	16.5 (1–79)	15.0 (1–77)	0.830

Time interval (hours)	Number of seizures		p
Time interval (hours)	PNES (n = 118)	ES (n = 176)	p
06:01–12:00	26 (22.1%)	51 (28.9%)	0.184^a a Pearson Chi-square test;
12:01–18:00	38 (32.2%)	50 (28.4%)	0.486^a a Pearson Chi-square test;
18:01–24:00	42 (35.6%)	39 (22.2%)	< 0.01^a a Pearson Chi-square test;
24:01–06:00	12 (10.2%)	36 (20.5%)	< 0.05^b b Yates Chi-square test.

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[1] Address for correspondence Hulya Ozkan (email: dr_hulyaozkan@yahoo.com).