The spectrum of benign myoclonus of early infancy: Clinical and neurophysiologic features in 102 patients

Abstract

SUMMARYPurpose: To redefine benign myoclonus of early infancy (BMEI) through analysis of clinical and neurophysiologic features in 102 patients with the aim to widen the spectrum of the syndrome, including a number of different clinical expressions of transient nonepileptic paroxysmal movements occurring in normal infants. Methods: We recruited patients from one center in Argentina and two in Italy, including infants with normal neurologic and psychomotor development presenting with brief paroxysmal abnormal movements. Children with motor phenomena occurring only during sleep were excluded. Patients with abnormal interictal or ictal electroencephalography (EEG) findings were also excluded. The follow-up ranged from 2-40 years. Results: One hundred and two infants (60 male) met the inclusion criteria. Age at onset ranged from 1-12 months, with a median age of 6.2 months. The following nonepileptic paroxysmal motor phenomena were recognized: (1) myoclonus, (2) spasms and brief tonic contractions, (3) shuddering, (4) atonia or negative myoclonus, (5) more than one type of motor phenomenon. In the majority of cases the episodes occurred only while awake and repeated several times a day. In 45 (44.1%) of the 102 cases contractions appeared in clusters. Conclusions: Based on the analysis of clinical and EMG features in this large series of infants, we postulate that the spectrum of the syndrome is wider than initially suspected, and that the different transient motor manifestations and their correlation with different EMG patterns will allow recognition of this definitely benign condition comprising a variety of episodic motor phenomena in normal babies.

Intermittent head drops: the differential spectrum

“…Most of the conditions associated with IHDs occur in infancy (ie, epileptic encephalopathy, progressive myoclonic epilepsy and IHDs of unknown origin)7–17 45 46 or childhood (ie, stereotypies, paroxysmal torticollis, narcolepsy type 1 and Tourette syndrome) 3–5 18–20 29–31. Conversely, the only type of IHDs occurring during adulthood is seen in choreic syndromes and sometimes in narcolepsy type 1 1 2 23–26 35.…”

Syncopes and other paroxysmal events

“…Paroxysmal tonic up-gaze now seems a heterogeneous condition (Caraballo et al, 2009) that does not always have a favorable outcome (Hayman et al, 1998) and, unlike the three conditions previously outlined, may include "organic" conditions such as channelopathies and dopa-responsive disorders.…”

Epileptic encephalopathies in infancy and early childhood

“…29 Erroneous diagnoses include exaggerated startle responses or 'colic and abdominal pain', nonepileptic episodic disorders and gastro-oesophageal reflux. 29 Benign myoclonus of early infancy (benign non-epileptic infantile spasms or Fejeman syndrome) [63][64][65] is not an epileptic condition, but may cause diagnostic problems because of a similar age at onset and similar spasms (see page 112). A normal EEG is of decisive significance in the differential diagnosis.…”