Occurrence of only myoclonic jerks in juvenile myoclonic epilepsy

Objectives - The clinical data on individuals who were diagnosed to have juvenile myoclonic epilepsy (JME) on the basis of myoclonic jerks alone has been analysed. The points in favour and against individuals with only myoclonic jerks being classified as ''affected'' for research on JME are discussed. Materials and methods - We studied 15 persons diagnosed with JME on the basis of only myoclonic jerks in a series of 161 patients with JME and their relatives. Detailed information on the seizure types in JME patients and their family members was collected. All affected individuals were examined by one person and had at least one conventional scalp EEG. CT/MRI of the brain was done as and when indicated. Results - Nine of these were probands while 6 were the relatives of JME patients. The EEG was abnormal in 8 of 9 probands and 1 of 6 relatives with only myoclonic jerks. All the 9 probands and 2 relatives with only myoclonic jerks were treated with anti-epileptic drugs. Three of the 4 relatives had spontaneous remission of jerks after variable intervals. Four of 15 persons with only myoclonic jerks had a first degree relative with definite JME. Conclusions - It appears that persons with myoclonic jerks alone may represent a benign subgroup of JME that may be genetically distinct from classic JME and the jerks may even spontaneously remit in a few cases. It is suggested that those persons with only myoclonic jerks and a first degree relationship with a definite diagnosis of JME can be classified as ''affected'' for inclusion into molecular studies, till molecular tools are available to settle the issue of phenotypic variations in hereditary neurological disorders like JME.