In these epilepsy syndromes, seizure frequency and interictal epileptic activity are higher in somnolence and in non-REM sleep (NREM): self-limited epilepsy with autonomic seizures (SeLEAS), self-limited epilepsy with centrotemporal spikes (SeLECTS), and—not considered to be self-limited—sleep-related hypermotor epilepsy (SHE; [1]).

The self-limited epilepsy syndromes are considered to be a nosological continuum, etiologically corresponding to alterations in the genetically determined cerebral maturation processes. The focal semiology of the seizures corresponds to electroencephalographic (EEG) changes and reflects a hyperexcitability of the corresponding neuronal network maturation of the brain [4].

Depending on age, different networks are implicated, namely, the autonomous network in SeLEAS and the sensory–motor and vocal network in SeLECTS (Fig. 1).

Fig. 1

Spectrum of sleep-related epilepsy syndromes and developmental and epileptic encephalopathies (DEEs) depending on predominant seizure activity at sleep onset or in the transition to wakefulness. CSWS continuous spikes and waves during sleep, PMG polymicrogyria. (Adapted from Specchio et al. [1] and Hirsch et al. [2])

Self-limited epilepsy with autonomic seizures

Self-limited epilepsy with autonomic seizures (SeLEAS), formerly called “Panayiotopoulos syndrome,” represents the youngest spectrum of the sleep-associated epilepsy syndromes. It has a prevalence of 13% of all children with epilepsy between 3 and 6 years and is probably genetically determined; rare SCN1A pathogenic variants have been described. It starts between 3 and 6 years and remits after a mean duration of 3 years. There is a history of febrile seizures in 5–17% of cases, but also transitions to SeLECTS are seen in 20% of patients, but also transitions to developmental and epileptic encephalopathy (DEE) and epileptic encephalopathy (EE) with spike-and-wave activation in sleep (SWAS) are possible.

Seizure semiology is either (a) autonomic or (b) non-autonomic and there is (c) a tendency toward status epilepticus.

Autonomic seizures are present in 75% of SeLEAS and consist of pallor, retching, flushing, nausea, malaise, abdominal pain, and vomiting. More than 90% are focal seizures with impaired awareness. Fatal complications are rare but have been reported, for example, cardiac arrest and sudden unexpected death in epilepsy (SUDEP); in this context nocturnal monitoring has to be considered [5, 6].

Non-autonomic seizures consist of eye deviation (minutes to hours) and hemi-convulsions in less than 10% of cases, including hemi-spasms, visual hallucinations, eye lid myoclonia, and nystagmus. Two thirds of all seizures appear during sleep. The duration of these seizures is longer than 30 min in 50% of all cases of SeLEAS (Fig. 2).

Fig. 2

Electroencephalogram of a case of self-limited epilepsy with autonomic seizures (SeLEAS), with autonomic symptoms starting from the right occipital area

As in all self-limited epilepsies, treatment is not always mandatory and depends very much on the seizure frequency or the risks associated with the seizures. The frequency of interictal epileptic activity is not a robust argument in favor of antiseizure treatment when there are no clinical signs of a transition to (D)EE-SWAS with stagnation or regression or no clear risk for injuries during seizures. Nevertheless, since autonomic seizures are particularly difficult for parents to witness and are associated with rare fatal complications, antiseizure treatment may be started more easily along with monitoring (e.g., NightWatch; [5, 6]).

Self-limited epilepsy with centrotemporal spikes

Self-limited epilepsy with centrotemporal spikes, formerly called “Rolandic epilepsy,” is the most frequent focal epilepsy in childhood, with a prevalence of 6–7% of all pediatric epilepsies. The origin is clearly genetic although gene variants are yet to be determined, with the exception of pathogenic gene variants in GRIN2A in some of the children with a transition to (D)EE-SWAS; nevertheless, a positive family history is not rare. Febrile seizures are reported in 5–15% of cases and, although rare, there is a transition from SeLEAS to SeLECTS. The first seizures tend to start at 4–10 years of age with a peak at 7 years and they remit by puberty, whereas epileptic discharges remit only in late adolescence.

Seizure duration in SeLECTS is normally brief, i.e., < 2–3 min. The seizures are few in number and in 80–90% of cases they occur during sleep; nevertheless, up to 20% appear while awake [4, 6,7,8].

Seizure semiologies comprise the following somatosensory symptoms (see also Fig. 3):

Unilateral numbness or paresthesia of the tongue, lips, gums, and inner cheek

Orofacial motor signs, with tonic or clonic contraction of one side of the mouth, face, or tongue

Speech arrest with inability to speak but understanding of language, in particular in left hemispheric seizures

Sialorrhea, ictal, due to increased salivation or swallowing disturbances

Fig. 3

Electroencephalographic study showing a interictal spikes in the right centrotemporal area; b start of the seizure, with numb sensation in the corner of the mouth; c deviation of the corner of the mouth; d clonic jerks in the right corner of the mouth with involvement of the left arm

As mentioned earlier, treatment in SeLECTS is not always mandatory and depends very much on the seizure frequency or the risks associated with the seizures. As in the case of SeLEAS, in SeLECTS, too, the frequency of interictal epileptic activity is not a robust argument in favor of antiseizure treatment when there are no clinical signs of a transition to (D)EE-SWAS with stagnation or regression or no clear risk for injuries during seizures.

Comorbidities of self-limited epilepsies of childhood as the simultaneous presence of two or more diseases have to be differentiated from direct consequences of epilepsy or epileptic activity and from drug side effects. In the presence of all options this differentiation is not always easy or obvious, but it is very important to disentangle these through neuropsychological testing and, when possible, with antiseizure drug modification or tapering [9].

SeLEAS are often associated with impaired performance in arithmetic, comprehension of image arrangements, visuoconstructive abilities, attention, and memory, but there is normal intelligence.

SeLECTS patients occasionally complain about executive disfunctions including inhibitory control, mental flexibility, and working memory. Attention-deficit/hyperactivity disorder (ADHD) symptoms are present in 20% of these patients. Nevertheless, concentration impairment due to epilepsy or antiseizure medication has to be differentiated from ADHD as a comorbid disease. Further impairment of visual perception is reported, as well as in fine motor skills, memory, working speed, but also verbal functions—verbal fluency, phonemic, semantic, auditory verbal, lexical comprehension, reading, spelling, learning, and verbal knowledge. Intelligence in SeLECTS patients is normal, but slightly lower than in controls.

In general, in sleep-associated self-limited epilepsies of childhood, learning disorder is reported in 10–40% of patients and leads to academic underachievement.

For sleep-associated self-limited epilepsies of childhood, sleep EEGs are mostly needed to make the correct diagnosis; overnight EEGs make it possible to quantify the activation of epileptic activity and the impact on sleep structure.

Transitions to encephalopathies are possible in sleep-associated self-limited epilepsies of childhood [7]: They involve atypical focal epilepsy of childhood, (D)EE-SWAS, and as a subgroup, Landau–Kleffner syndrome (LKS). These will be described in more detail in the section on “Sleep-accentuated epilepsies.”

Sleep-related hypermotor epilepsy

Sleep-related hypermotor epilepsy was formerly called “nocturnal frontal lobe epilepsy”; SHE is a rare syndrome with a prevalence of the nonfamilial form of 1.8–1.0 per 100,000 [10, 11].

Although most cases of SHE arise from the frontal lobe, an extra-frontal onset is also possible and is challenging when no structural abnormality is present.

Regarding seizure semiology, most highly integrated ictal behaviors tend to originate from anterior prefrontal regions, whereas more elementary motor signs emerge from posterior regions of the frontal lobe [12]. They are characterized by clusters of motor seizures occurring from sleep with abrupt onset, brief duration, preserved awareness, and stereotyped (a) hyperkinetic or (b) asymmetric dystonic or tonic motor seizure patterns; mostly they are accompanied by (c) autonomic features such as tachycardia, tachypnea, irregular respiration, but also vocalization and fear. Eye or head deviation is possible.

Hyperkinetic movements include irregular large-amplitude movements like pedaling, jumping, pelvic thrusting, or rocking. They can also be very subtle, formerly called “paroxysmal arousals,” but can also be of longer duration and greater complexity in the semiology, for example, epileptic wandering [12].

They can be genetic, although only in a small portion of patients have gene variants been identified such as CHRNA4 and others such as KCNT1 and DEPDC5 [13, 14].

Structural origins of SHE are focal cortical dysplasias or acquired structural abnormalities. Differential diagnoses are disorders of arousal, sleep-related movement disorders, and REM sleep behavior disorders (Fig. 4).

Fig. 4

Electroencephalogram showing seizure onset in the left frontal and frontotemporal area with spikes and rhythmic theta activity (Fp1, F3, T3) followed by hypermotor seizure semiology and corresponding muscle artifacts