Myoclonus and epilepsies

Abstract

The possible associations of myoclonic phenomenae, progressive or non-progressive encephalopathies and epileptic features are reviewed, with special emphasis on pediatric age. This leads to recognize the following five groups of conditions: (1) Myoclonus without encephalopathy and without epilepsy; (2) Encephalopathies with non-epileptic myoclonus; (3) Progressive encephalopathies presenting myoclonus seizures of epileptic syndromes (Progressive myoclonus epilepsies); (4) Epileptic encephalopathies with myoclonic seizures; (5) Myoclonic epilepsies. Within the first group, which also includes physiologic myoclonus, a more thorough description of "Benign sleep myoclonus of newborn" and "Benign myoclonus of early infancy" is given. Characteristics of group 2 are "Kinsbourne Syndrome" and certain types of "Hyperekplexia" which pose interesting differential diagnosis with stimulus-sensitive epilepsies. In group 3, the concept of progressive encephalopathies is stressed. The fourth group refers to severe epilepsies, mainly on infancy and childhood, which lead to mental retardation irrespective of their aetiology. Group 5 comprises the true myoclonic epilepsies, differentiating syndromes recognized as idiopathic--such as "Benign myoclonic epilepsy of infancy" and "Juvenile myoclonic epilepsy"--from those which are cryptogenic and carry a more cautious prognosis--as "Cryptogenic myoclonic and myoclonoastatic epilepsies" and "Severe myoclonic epilepsy of infancy". Other epileptic syndromes not usually considered as myoclonic epilepsies, but presenting sometimes as myoclonic seizures, are finally referred.

Top of the basilar artery embolic stroke and neonatal myoclonus

“…This child had lesions in the superior cerebellar cortex and dentate nucleus on both sides, the dentato‐rubro‐thalamic pathways, and the left occipital cerebral cortex. These lesions were the most likely cause of the acute, symptomatic myoclonus of both his upper limbs, without time‐locked cerebrocortical EEG correlate, which is classified as subcortical–supraspinal 11 . Many acute movement disorders in adults and older children follow focal injury to the striatum, thalamus, 12 or the brainstem 13 .…”

“…These lesions were the most likely cause of the acute, symptomatic myoclonus of both his upper limbs, without time-locked cerebrocortical EEG correlate, which is classified as subcortical-supraspinal. 11 Many acute movement disorders in adults and older children follow focal injury to the striatum, thalamus, 12 or the brainstem. 13 Holmes' wide-range 2 to 5Hz tremor is associated with cerebellar injury with loss of afferent control on the rubral neurons, 14,15 but myoclonus can also follow injury to the cerebellum.…”

Opsoclonus-myoclonus syndrome: A study of three patients with stimulus-sensitive myoclonus

“…According to the cortical or subcortical origin, myoclonic jerks may be epileptic or non-epileptic, respectively [4][5][6]. Table 1 shows the different combinations of encephalopathies, myoclonus, and epilepsy, including the stimulus-sensitive forms [7][8][9][10][11]. According to this classification, our patients could be included in the group of non-epileptic encephalopathies with myoclonus as they presented myoclonic jerks in the course of an encephalopathy and their electroencephalographic studies did not show pathologic ictal or interictal activity, even during the episodes.…”

“…We believe that spontaneous and reflex myoclonic jerks in patients with OMS may share a similar pathophysiological mechanism. On the other hand, we have Table 1 Combinations of myoclonus, encephalopathies, and epilepsy (modified by Fejerman [10] • Prospective studies would be necessary to define the true incidence of stimulus-sensitive myoclonus to evaluate if the presence of the myoclonus interferes in the general evolution of the disease, and to consider if symptomatic treatment of the crises is necessary.…”

Nocturnal variant of benign myoclonic epilepsy of infancy: a case series

“…Benign myoclonic epilepsy of infancy, described by Fejerman in 1997, is an epilepsy syndrome characterised by myoclonic seizures that manifest in young children with normal development (Fejerman, ). The brief myoclonic attacks occur in otherwise normal infants from 6 months to 3 years of age, involving the upper limbs, head, and rarely the lower limbs.…”