Benign neonatal sleep myoclonus (BNSM) is the occurrence of myoclonus (jerky movements) during sleep. It is not associated with seizures.

Occurs in the first few weeks of life, usually resolves in first 2–3 months of life. Often worries parents because they appear like seizures, but they are not. Features that can help distinguish this condition from seizures include: The myoclonic movements only occur during sleep, when baby is woken up the myoclonic movements stop, normal EEG, normal neurological examination, normal developmental examination. The myoclonic jerks occur during non-REM sleep

Myoclonic seizure can be described as "jumps" or "jolts" experienced in a single or even the entire body. The feeling experienced by the individual is described as uncontrollable jolts common to receiving a mild electric shock. The sudden jerks and twitching of the body can often be so severe that it can cause a small child to fall.

A myoclonic seizure ("myo" "muscle", "clonic" "jerk") is a sudden involuntary contraction of muscle groups. The muscle jerks consist of symmetric, mostly generalized jerks, localized in the arms and in the shoulders and also simultaneously with a head nod; both the arms may fling out together and simultaneously a head nod may occur. Symptoms have some variability amongst subjects. Sometimes the entire body may jerk, just like a startle response. As is the case with all generalised seizures, the patient is not conscious during the event but the seizure is so brief that the person appears to remain fully conscious.

In reflex epilepsies, myoclonic seizures can be brought on by flashing lights or other environmental triggers (see photosensitive epilepsy).

Familiar examples of normal myoclonus include hiccups and hypnic jerks that some people experience while drifting off to sleep. Severe cases of pathologic myoclonus can distort movement and severely limit a person's ability to sleep, eat, talk, and walk. Myoclonic jerks commonly occur in individuals with epilepsy.

The most common types of myoclonus include action, cortical reflex, essential, palatal, those seen in the progressive myoclonus epilepsies, reticular reflex, sleep and stimulus-sensitive.

Juvenile myoclonic epilepsy is responsible for 7% of cases of epilepsy. Seizures usually begin around puberty and usually have a genetic basis. Seizures can be stimulus-selective, with flashing lights being one of the most common triggers.

Myoclonic jerks that are not epileptic may be due to a nervous system disorder or other metabolic abnormalities that may arise in renal (e.g. hyperuraemia) and liver failure (e.g. high ammonia states).

Juvenile myoclonic epilepsy (JME) is an idiopathic generalized epilepsy that occurs in patients aged 8 to 20 years. Patients have normal cognition and are otherwise neurologically intact. The most common seizure is myoclonic jerks, although generalized tonic-clonic seizures and absence seizures may occur as well. Myoclonic jerks usually cluster in the early morning after awakening. The EEG reveals generalized 4–6 Hz spike wave discharges or multiple spike discharges. These patients are often first diagnosed when they have their first generalized tonic-clonic seizure later in life, when they experience sleep deprivation (e.g., freshman year in college after staying up late to study for exams). Alcohol withdrawal can also be a major contributing factor in breakthrough seizures, as well. The risk of the tendency to have seizures is lifelong; however, the majority have well-controlled seizures with anticonvulsant medication and avoidance of seizure precipitants.

Frontal lobe epilepsy, usually a symptomatic or cryptogenic localization-related epilepsy, arises from lesions causing seizures that occur in the frontal lobes of the brain. These epilepsies can be difficult to diagnose because the symptoms of seizures can easily be confused with nonepileptic spells and, because of limitations of the EEG, be difficult to "see" with standard scalp EEG.

Juvenile absence epilepsy is an idiopathic generalized epilepsy with later onset than CAE, typically in prepubertal adolescence, with the most frequent seizure type being absence seizures. Generalized tonic-clonic seizures can occur. Often, 3 Hz spike-wave or multiple spike discharges can be seen on EEG. The prognosis is mixed, with some patients going on to a syndrome that is poorly distinguishable from JME.

The cardinal features of Rolandic epilepsy are infrequent, often single, focal seizures consisting of:

Hemifacial sensorimotor seizures are often entirely localised in the lower lip or spread to the ipsilateral hand. Motor manifestations are sudden, continuous or bursts of clonic contractions, usually lasting from a few seconds to a minute. Ipsilateral tonic deviation of the mouth is also common. Hemifacial sensory symptoms consist of unilateral numbness mainly in the corner of the mouth.

Hemifacial seizures are often associated with an inability to speak and hypersalivation:

"The left side of my mouth felt numb and started jerking and pulling to the left, and I could not speak to say what was happening to me."

Negative myoclonus can be observed in some cases, as an interruption of tonic muscular activity

Oropharyngolaryngeal ictal manifestations are unilateral sensorimotor symptoms inside the mouth. Numbness, and more commonly paraesthesias (tingling, prickling, freezing), are usually diffuse on one side or, exceptionally, may be highly localised even to one tooth. Motor oropharyngolaryngeal symptoms produce strange sounds, such as death rattle, gargling, grunting and guttural sounds, and combinations:

"In his sleep, he was making guttural noises, with his mouth pulled to the right, ‘as if he was chewing his tongue’". "We heard her making strange noises ‘like roaring’ and found her unresponsive, head raised from the pillow, eyes wide open, rivers of saliva coming out of her mouth, rigid."

Arrest of speech is a form of anarthria. The child is unable to utter a single intelligible word and attempts to communicate with gestures.

"My mouth opened and I could not speak. I wanted to say I cannot speak. At the same time, it was as if somebody was strangling me."

Hypersalivation , a prominent autonomic manifestation, is often associated with hemifacial seizures, oro-pharyngo-laryngeal symptoms and speech arrest. Hypersalivation is not just frothing:

"Suddenly my mouth is full of saliva, it runs out like a river and I cannot speak."

Syncope-like epileptic seizures may occur, probably as a concurrent symptom of Panayiotopoulos syndrome:

"She lies there, unconscious with no movements, no convulsions, like a wax work, no life."

Consciousness and recollection are fully retained in more than half (58%) of Rolandic seizures.

"I felt that air was forced into my mouth, I could not speak and I could not close my mouth. I could understand well everything said to me. Other times I feel that there is food in my mouth and there is also a lot of salivation. I cannot speak."

In the remainder (42%), consciousness becomes impaired during the ictal progress and in one third there is no recollection of ictal events.

Progression to hemiconvulsions or generalised tonic–clonic seizures occurs in around half of children and hemiconvulsions may be followed by postictal Todd’s hemiparesis .

Duration and circadian distribution: Rolandic seizures are usually brief, lasting for 1–3 min. Three quarters of seizures occur during nonrapid eye movement sleep, mainly at sleep onset or just before awakening.

Status epilepticus: Although rare, focal motor status or hemiconvulsive status epilepticus is more likely to occur than secondarily generalised convulsive status epilepticus, which is exceptional. Opercular status epilepticus usually occurs in children with atypical evolution or may be induced by carbamazepine or lamotrigine. This state lasts for hours to months and consists of ongoing unilateral or bilateral contractions of the mouth, tongue or eyelids, positive or negative subtle perioral or other myoclonus, dysarthria, speech arrest, difficulties in swallowing, buccofacial apraxia and hypersalivation. These are often associated with continuous spikes and waves on an EEG during NREM sleep.

Other seizure types: Despite prominent hypersalivation, focal seizures with primarily autonomic manifestations (autonomic seizures) are not considered part of the core clinical syndrome of Rolandic epilepsy. However, some children may present with independent autonomic seizures or seizures with mixed Rolandic-autonomic manifestations including emesis as in Panayiotopoulos syndrome.

Atypical forms: Rolandic epilepsy may present with atypical manifestations such early age at onset, developmental delay or learning difficulties at inclusion, other seizure types, atypical EEG abnormalities.

These children usually have normal intelligence and development. Learning can remain unimpaired while a child is afflicted with Rolandic epilepsy.

Panayiotopoulos syndrome occurs exclusively in otherwise normal children and manifests mainly with infrequent autonomic epileptic seizures and autonomic status epilepticus. Onset of seizures is from age 1 to 14 years with 76% starting between 3–6 years. Autonomic seizures consist of episodes of disturbed autonomic function with nausea, retching and vomiting as predominant symptoms. Other autonomic manifestations include pallor (or, less often, flushing or cyanosis), mydriasis (or, less often, miosis), cardiorespiratory and thermoregulatory alterations, incontinence of urine and/or feces, hypersalivation, and modifications of intestinal motility. In approximately one fifth of the seizures the child becomes unresponsive and flaccid (syncope-like epileptic seizures or ictal syncope) before or often without convulsions. Syncope-like epileptic seizures (ictal syncope) with the child becoming "completely unresponsive and flaccid like a rag doll" occur in one fifth of the seizures. More-conventional seizure symptoms often appear after the onset of autonomic manifestations. The child, who was initially fully conscious, becomes confused and unresponsive. Eyes turn to one side or gaze widely open. Only half of the seizures end with brief hemiconvulsions or generalized convulsions. Autonomic symptoms may be the only features of the seizures. None of the above symptoms alone is a prerequisite for diagnosis. Recurrent seizures may not be stereotyped. The same child may have brief or prolonged seizures and autonomic manifestations may be severe or inconspicuous. The full emetic triad (nausea, retching, vomiting) culminates in vomiting in 74% of the seizures; in others only nausea or retching occur, and in a few, none of the emetic symptoms are apparent.

Most of the seizures are prolonged and half of them last more than 30 minutes thus constituting autonomic status epilepticus, which is the more common nonconvulsive status epilepticus in normal children. Characteristically, even after the most severe seizures and autonomic status epilepticus, the child is normal after a few hours of sleep, which is both diagnostic and reassuring. However, it has been recently reported that sometime after status epilepticus in children with Panayiotopoulos syndrome a. growth of the frontal and prefrontal lobes is slightly decreased and b.the scores on the neuropsychological tests is decreased.

Focal onset hemiconvulsions or generalised convulsions occur in nearly half of the seizures. These are usually shorter than the preceding autonomic manifestations but in a few cases a. they may be prolonged constituting convulsive status epilepticus or b. the preceding autonomic manifestations are brief and not apparent

Seizures can occur at any time but they are more common during sleep.

Myoclonic seizures involve brief involuntary muscle twitching, and may become frequent enough to be disabling. Tonic-clonic seizures have two phases: the tonic phase may last a few seconds and involves the muscles tensing, and may lead to the person falling down; the clonic phase involves a convulsion of rapidly alternating muscle tensing and relaxing. Neurological dysfunction includes difficulty coordinating muscle movements (ataxia) and a decline in cognitive ability (dementia).

In the early stages, it can be difficult to distinguish progressive myoclonic epilepsy from benign idiopathic generalised epilepsies, such as juvenile myoclonic epilepsy. With PME, the initial effectiveness of anticonvulsant treatment diminishes as seizures become more frequent and neurological decline progresses. However, these can also be signs of anticonvulsant intoxication. The myoclonus in PME is usually severe and is the prominent seizure type.

Panayiotopoulos syndrome is now the formally approved nomenclature for this syndrome in the new International League against Epilepsy report on classification, which abandoned a number of previously used descriptive terms such as early onset benign childhood epilepsy with occipital paroxysms, early onset benign childhood occipital epilepsy, nocturnal childhood occipital epilepsy. The reason for this is that these descriptive terms were criticized as incorrect because in Panayiotopoulos syndrome:

“An autonomic seizure is an epileptic seizure characterized by altered autonomic function of any type at seizure onset or in which manifestations consistent with altered autonomic function are prominent (quantitatively dominant or clinically important) even if not present at seizure onset. The altered autonomic function may be objective or subjective or both.”

“Autonomic status epilepticus is an autonomic seizure which lasts for more than 30 minutes, or a series of such seizures over a 30 minute period without full recovery between seizures.”

Benign neonatal seizures include two disorders benign idiopathic neonatal seizures and benign familial neonatal seizures. They are not classified as epilepsy. Anticonvulsants are not needed. And those affected do not develop epilepsy when they grow up.

Myoclonus is characterized by rapid contractions that affect the upper body including the neck, torso and arms, but may also affect the legs. These movements are stimulated by various factors including stress, noise, caffeine, and physical stimuli. Myoclonus can be characterized in multiple ways including neurological basis, muscular activity, and by stimuli. Myoclonus can be positive or negative; positive myoclonus results from brief spurts of muscle activity and negative myoclonus occurs when there is a lack of any muscular activity. Myoclonus is usually classified physiologically to optimize treatment. Myoclonus is a precursor effect to myoclonus dystonia and most commonly begins in childhood or adolescence.

Myoclonus is classified as cortical, subcortical, peripheral or spinal. Cortical myoclonus is the most common of these four and affects the upper limbs and face. Myoclonus dystonia has been characterized under subcortical origin, specifically under nonsegmented myoclonus or brainstem myoclonus. Symptoms within this classification include the startle response and reticular reflex myoclonus. Sudden stimuli like noise or touch to areas around the head or chest cause the startle response which will go up the brain stem and down the spinal cord causing jerk-like movements. Hyperekplexia is a heightened brainstem response where an affected person will continue to elicit the same response to a repeated stimuli. In contrast, reticular reflex myoclonus occurs spontaneously to stimuli applied to distal limbs. Spinal myoclonus is caused by defects in spinal organization or connections, and peripheral myoclonus has symptoms of rhythmic jerks due to a neuron-the most common being the hemifacial spasm.

Myoclonus dystonia includes the rapid contractions of myoclonus alongside the abnormal postures classified under dystonia, as well as neurological and psychiatric issues. This disease typically begins during childhood with symptoms of myoclonus and slight dystonia, most commonly cervical dystonia or writer’s cramp. Dystonia symptoms tend to not get exaggerated over the course of the disease and is rarely the only associated symptom, while the myoclonus symptoms can become more severe. Psychiatric issues are clinically diagnosed with the aforementioned symptoms and include depression, anxiety, personality disorders and addiction. Obsessive-compulsive disorder is associated with myoclonus dystonia as both have been found to have a commonality on chromosome 7 in various studies.

Neurological symptoms are relatively common in those with myoclonus dystonia. Any neurological abnormalities won’t normally be present in those affected at a young age. Neurological testing has been performed to determine the origins of these symptoms and multiple parts of the brain have been pinpointed including the brainstem, neocortex, pallidum, and thalamus. These cause various effects in those diagnosed with myoclonus dystonia including changes in posture and tremors, and very rarely dementia and ataxia.

Patients with Unverricht–Lundborg disease exhibit myoclonic jerks and tonic-clonic seizures at a young age, between ages 6–16. The myoclonic jerks occur in the muscles of the arms and legs closest to the torso, and are triggered due to a variety of common external stimuli. Seizures begin at an average age of 10.8 years, with myoclonus beginning around 12.1 years. It is not currently possible to diagnose without a genetic test, and since early symptoms are general, it is often mistaken for another more common epilepsy, in many cases juvenile myoclonic epilepsy (JME).

Patients with PLMD will complain of excessive daytime sleepiness (EDS), falling asleep during the day, trouble falling asleep at night, and difficulty staying asleep throughout the night. Patients also display involuntary limb movements that occur at periodic intervals anywhere from 20–40 seconds apart. They often only last the first half of the night during non-REM sleep stages. Movements do not occur during REM because of muscle atonia.

The diagnosis can be confirmed when the characteristic centrotemporal spikes are seen on electroencephalography (EEG). Typically, high-voltage spikes followed by slow waves are seen. Given the nocturnal activity, a sleep EEG can often be helpful. Technically, the label "benign" can only be confirmed if the child's development continues to be normal during follow-up. Neuroimaging, usually with an MRI scan, is only advised for cases with atypical presentation or atypical findings on clinical examination or EEG.

The disorder should be differentiated from several other conditions, especially centrotemporal spikes without seizures, centrotemporal spikes with local brain pathology, central spikes in Rett syndrome and fragile X syndrome, malignant Rolandic epilepsy, temporal lobe epilepsy and Landau-Kleffner syndrome.

People with PLMD often do not know the cause of their excessive daytime sleepiness and their limb movements are reported by a spouse or sleep partner.

PLMD is diagnosed with the aid of a polysomnogram or PSG. PLMD is diagnosed by first finding PLMS (periodic limb movements of sleep) on a PSG, then integrating that information with a detailed history from the patient and/or bed partner. PLMS can range from a small amount of movement in the ankles and toes, to wild flailing of all four limbs. These movements, which are more common in the legs than arms, occur for between 0.5 and 5 seconds, recurring at intervals of 5 to 90 seconds. A formal diagnosis of PLMS requires three periods during the night, lasting from a few minutes to an hour or more, each containing at least 30 movements followed by partial arousal or awakening.

Benign familial infantile epilepsy (BFIE), also known as benign familial infantile seizures (BFIS) or benign familial infantile convulsions (BFIC) is an epilepsy syndrome. Affected children, who have no other health or developmental problems, develop seizures during infancy. These seizures have focal origin within the brain but may then spread to become generalised seizures. The seizures may occur several times a day, often grouped in clusters over one to three days followed by a gap of one to three months. Treatment with anticonvulsant drugs is not necessary but they are often prescribed and are effective at controlling the seizures. This form of epilepsy resolves after one or two years, and appears to be completely benign. The EEG of these children, between seizures, is normal. The brain appears normal on MRI scan.

A family history of epilepsy in infancy distinguishes this syndrome from the non-familial classification (see benign infantile epilepsy), though the latter may be simply sporadic cases of the same genetic mutations. The condition is inherited with an autosomal dominant transmission. There are several genes responsible for this syndrome, on chromosomes 2, 16 and 19. It is generally described as idiopathic, meaning that no other neurological condition is associated with it or causes it. However, there are some forms that are linked to neurological conditions. One variant known as infantile convulsions and choreoathetosis (ICCA) forms an association between BFIE and paroxysmal kinesigenic choreoathetosis and has been linked to the PRRT2 gene on chromosome 16. An association with some forms of familial hemiplegic migraine (FHM) has also been found. Benign familial infantile epilepsy is not genetically related to benign familial neonatal epilepsy (BFNE), which occurs in neonates. However, a variation with seizure onset between two days and seven months called "benign familial neonatal–infantile seizures" (BFNIS) has been described, which is due to a mutation in the SCN2A gene.

The genetic cause of ULD is known, but research has led to new areas of study that may lead to an increase in knowledge of what causes ULD.

The three main signs of hyperekplexia are generalized stiffness, excessive startle beginning at birth and nocturnal myoclonus. Affected individuals are fully conscious during episodes of stiffness, which consist of forced closure of the eyes and an extension of the extremities followed by a period of generalised stiffness and uncontrolled falling at times. Initially, the disease was classified into a "major" and a "minor" form, with the minor form being characterized by an excessive startle reflex, but lacking stiffness. There is only genetic evidence for the existence of the major form.

Other signs and symptoms of hyperekplexia may include episodic neonatal apnea, excessive movement during sleep and the head-retraction reflex. The link to some cases of Sudden Infant Death remains controversial.

The only sign of BFNE are seizures, generally tonic-clonic, which occur within the first week of life. Seizures often begin as apnea, cyanosis, and hypertonia and last less than 1 minute.

People with BFNE are not more likely to develop epileptic seizures later in life.

A hypnic jerk, hypnagogic jerk, sleep start, sleep twitch or night start is an involuntary twitch which occurs when a person is beginning to fall asleep, often causing them to awaken suddenly for a moment. Physically, hypnic jerks resemble the "jump" experienced by a person when startled, sometimes accompanied by a falling sensation. Hypnic jerks are associated with a rapid heartbeat, quickened breathing, sweat, and sometimes "a peculiar sensory feeling of 'shock' or 'falling into the void. A higher occurrence is reported in people with irregular sleep schedules.

An individual displaying MERRFs syndrome will manifest not only a single symptom, but regularly patients display more than one affected body part at a time. It has been observed that patients with MERRF syndrome will primarily display Myoclonus as a first symptom, along with it they can also manifest seizures, cerebellar ataxia and myopathy. Secondary features include dementia, optic atrophy, bilateral deafness, peripheral neuropathy, spasticity or multiple lipomata. Additional symptoms include dementia, optic atrophy, bilateral deafness and peripheral neuropathy, spasticity, lipomatosis, and/or cardiomyopathy with wolff parkinson-white syndrome. Most patients will not exhibit all of these symptoms, however more than one of these symptoms will be present in a patient who has been diagnosed with MERRFS disease. Due to the multi-symptoms presented by the individual, the severity of the syndrome is very difficult to evaluate. Mitochondrial disorders may present at any age, and this holds truth for MERRS, since it forms part of them. Therefore, if a patient is presenting some of these symptoms, the doctor is able to narrow it down to MEERF mitochondrial disorder.