Tap seizures in infancy

Emanuela C. Turco, Anna Andreolli and Francesco Pisani.  Tap seizures in infancy: A critical review.  Seizure: European Journal of Epilepsy, 2018-07-01, Volume 59, Pages 11-15.

Highlights

• Reflex Myoclonic Epilepsy shows spontaneous remission and excellent prognosis.

• A clinical identification avoids extensive investigations and anti-convulsant drugs.

• Tap seizure is related to age-dependent hyperexcitability of sensorimotor cortex.

• Tap seizure seems specific of a low level of functional segregation of the brain.

Abstract

Tap seizure is a type of reflex myoclonic epilepsy in which seizures are evoked mainly by unexpected tactile stimuli and which is classified among the electroclinical syndromes of infancy. This condition, whose onset is in the first two years of life, is characterized by excellent prognosis and is extremely rare. We reviewed all published articles and case reports on Reflex Myoclonic Epilepsies focusing on touch-induced seizures in order to clarify clinical and electroencephalographic findings. Our aim is to increase knowledge about this specific disorder in order to help pediatricians avoid extensive investigations when making their diagnosis and reassure parents regarding absence of long-term complications.

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From the article

Reflex Myoclonic Epilepsy in Infancy (RMEI), first described by Ricci in 1995, is a rare form of electroclinical syndrome which the recent report of the ILAE Commission on Classification and terminology (2017) has categorised as infancy due to the age of onset. Seizures appear during the first 3 years of life in children with normal motor and mental development . They are characterized by reflex myoclonic seizures (Reflex MS) triggered by unexpected stimuli of different types, especially auditory stimuli or combinations of auditory and tactile stimuli. Cases of reflex seizures induced by tactile-only stimulation have been reported in literature too, and named “tap seizure” or “touch-evoked seizures”.  This form of epileptic disorder is described as a variant of Myoclonic Epilepsy in Infancy  nosographic syndromes. RMEI appears to have an earlier onset, better response to antiepileptic drugs and a positive cognitive outcome, but it is not currently recognized as a distinct entity  and is still classified among the electroclinical syndromes as myoclonic epilepsy in infancy (MEI) due to the age of onset. We have reviewed all case-reports covering “Tap Seizure” in literature, and focused on the clinical and electroencephalographic features. This review may be of help to pediatricians in recognizing these specific, yet rare seizures, so as to perform a suitable differential diagnosis compared to other seizures burdened by unfavourable outcome…

Interictal EEG is usually characterized by normal background activity, even though several studies have described the presence of isolated epileptic abnormalities, brief spike and wave, or polyspikes and wave complexes without electromyographic correlation, during wakefulness and, more often, during sleep. Ictal EEG recordings show isolated or recurrent spikes, polyspike and wave, or generalized spike and wave complexes (at a frequency of 3–4 Hz according to some authors, which are correlated with the myoclonic jerks…

Some authors do not recommend treatment since myoclonic seizures occur only after a trigger stimulation and are of very brief duration. Treatment is usually recommended if attacks persist for more than six months. Valproate represents the first-line drug; complete seizure control was rarely achieved by adding either Clonazepam , Clobazam   or Ethosuximide.  Seizures were reported to disappear spontaneously without treatment after 8–19 months. Neuropsychological outcome is usually normal. Only 3 cases of language delay or cognitive borderline IQ were described at follow-up , but no behavioral problems were reported.

This clinical entity may be differentiated from other epileptic syndromes, such as startle epilepsy, which may start in childhood but is characterized by poor outcome. The triggering stimuli can involve any sensorial modality (usually auditory stimulus) but they must be sudden and unexpected. Patients usually have large brain lesions, mostly due to perinatal hypoxic brain damage, the seizures can be either partial or generalized and of different types (e.g. myoclonic, tonic), and are often drug-resistant. Other epileptic syndromes with myoclonic seizures in infancy could be confused with tap seizure, e.g. neonatal myoclonic encephalopathy or myoclonic seizures in severe symptomatic epilepsies with neonatal or infantile onset. In these syndromes, seizures may be triggered by sudden somatosensory stimuli. Several other clinical conditions may exhibit reflex myoclonic jerks due to severe neurometabolic or genetic diseases, such as Down Syndrome, where myoclonic seizures are frequent, and in SCN1A mutation, where somatosensory reflex seizures have also been reported. All these conditions are usually accompanied by mental developmental arrest or regression, whereas children with RMEI have normal extensive metabolic testing and good outcome. Since an element of surprise is predominant in tap seizure, at least at the onset, differential diagnosis must include early manifestations of startle disease or hyperekplexia, in which excessive startling to an unexpected stimuli (characteristically a tap at the base of the nose, in infants) is associated with tonic contraction and complex movements without epileptic discharges at the EEG. In addition, the outcome is not favourable due to the persistence of excessive jerking, presence of mild developmental delay and of the specific generalized muscular stiffness.