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Year : 1999  |  Volume : 47  |  Issue : 3  |  Page : 210-3

Factors of error involved in the diagnosis of juvenile myoclonic epilepsy : A study from South India.


Department of Neurology, Nizam's Institute of Medical Sciences, Panjagutta, Hyderabad, 500 082, India.

Correspondence Address:
Department of Neurology, Nizam's Institute of Medical Sciences, Panjagutta, Hyderabad, 500 082, India.

  »  Abstract

The study was aimed at finding possible factors for delay in the diagnosis of juvenile myoclonic epilepsy (JME) in a developing country. Data was analyzed retrospectively through the medical records and prospectively through a re-evaluation of the history and EEGs of patients with JME registered in a university hospital in south India. Of the 131 patients, 23 (17.5%) patients were seen by neurologists before registration in the clinic. Diagnosis of JME was established in 118 patients at the time of registration and in 13 (10%) patients during follow-up in the clinic. The mean interval between onset of disease and the diagnosis was 6.8 + 6.3 years. In 20 patients the diagnosis was established 10 years after the onset. The mean interval between the first evaluation and diagnosis was 24. 2 months in the 13 patients in whom the diagnosis was established during follow-up in the clinic. Lack of familiarity with the clinical syndrome was probably the factor for delay in the diagnosis in 108 patients seen by practising physicians. The factors for delay in the diagnosis in patients seen by neurologists included failure to ask about myoclonic jerks resulting in misinterpretation of EEGs in 28 patients, misinterpretation of absences and/or unilateral jerks in 4 patients, and failure to ask about myoclonic jerks and misinterpretation of focal EEG abnormalities in 4 patients. This study suggests that the possible factors of error in the diagnosis of JME among the neurologists were similar to the observations reported from the developed countries; whereas the factor for delay in the diagnosis of JME among practising physicians was lack of familiarity with the epileptic syndrome.

How to cite this article:
Murthy J M. Factors of error involved in the diagnosis of juvenile myoclonic epilepsy : A study from South India. Neurol India 1999;47:210


How to cite this URL:
Murthy J M. Factors of error involved in the diagnosis of juvenile myoclonic epilepsy : A study from South India. Neurol India [serial online] 1999 [cited 2019 Nov 18];47:210. Available from: http://www.neurologyindia.com/text.asp?1999/47/3/210/1613



Juvenile myoclonic epilepsy (JME) is a common form of idiopathic generalized epilepsy, with a prevalence of 5-11% among patients with epilepsy.[1],[2],[3] Despite the distinctive clinical and electroencephalographic features, JME is widely underdiagnosed or diagnosed late.[1],[2],[3],[4],[5],[6],[7] The literature on JME from developing countries is scanty.[7] The aim of the study is to determine possible factors responsible for the delay in the diagnosis of JME in a developing country.


   »   Material and methods Top


Patients registered in the epilepsy clinic, Nizam's Institute of Medical Sciences, in a six year period formed the study material. Patients registered in the clinic included patients referred by the author as well as those referred by practising physicians of the region.

Criteria for the diagnosis of JME included : (a) unequivocal clinical evidence of generalized tonic clonic seizures (GTCS) with myoclonic jerks mainly on awakening, (b) absence seizures (if present), (c) normal physical examination, (d) family history (if present), (e) characteristic EEG with generalized multiple spike and spike slow wave discharges (in an untreated patient).8 The possible factors responsible for the delay in the diagnosis of JME were studied retrospectively through the medical records and prospectively through a re-evaluation of the history and EEG of the patients.


   »   Results Top


Of the 131 patients with JME, 23 (18%) patients were seen by neurologists before registration in the clinic. Diagnosis of JME was made at the time of registration in 118 (90%) patients and during follow-up in the clinic in 13 (10%) patients. The mean age at onset in the total patient population was 13.37 + 4.83 years. The correct diagnosis was established after a mean of 6.8 + 6.3 years from the onset of disease. In 20 patients the delay was more than 10 years. The mean interval between the first evaluation and diagnosis was 24.2 months in the 13 patients in whom the diagnosis was established during follow-up in the clinic.

The referal diagnosis in the 108 patients seen by practising physicians was nonsyndromic [Table I]. Failure to ask about or failure to interpret the history of myoclonic jerks were the factors for the delay in the diagnosis in all of them. Probably this might be secondary to lack of familiarity with the epileptic syndrome. The factors of error that delayed correct diagnosis in 23 patients seen by neurologists and in 13 patients in whom the diagnosis was made during follow-up in the clinic are given in [Table II] [Table III].

Failure to ask about myoclonic jerks or not giving due importance to the history suggestive of jerks resulted in misinterpretation of EEG and delay in the diagnosis in 28 patients seen by neurologists. In 19 of them the initial diagnosis was idiopathic generalized epilepsy. All of them sought medical attention for generalized tonic clonic seizures. EEG features were diagnostic of JME in 11 and normal in 8 patients. In 9 patients the initial diagnosis was absence epilepsy and the seizure type for which they sought medical attention was absences. EEG showed 3-3.5 Hz spike wave activity, more pronounced during hyperventilation [Table III].

Diagnosis of partial or localization related epilepsy was made in 8 patients. Misinterpretation of unilateral onset of jerks preceding GTCS was responsible in 1 patient. Interictal EEG was normal in this patient. In 3 patients brief absences and predominantly unilateral onset of jerks that preceded GTCS were misinterpreted as `complex partial epilepsy'. EEG discharges were characteristic of JME in all the 3 patients. Failure to ask about myoclonic jerks and misinterpretation of the focal EEG abnormalities resulted in the diagnosis of partial epilepsy in 4 patients. Voltage asymmetry as the focal EEG abnormalities was observed in 4 patients.


   »   Discussion Top


Long delay between the onset of symptoms and the diagnosis has been noted in the earlier studies.[2],[6] In this study lack of awareness of the clinical syndrome and failure to ask about myoclonic jerks or not giving due importance to the history suggestive of myoclonic jerks seem to be the most important factors for the delay in the diagnosis. This error has happened even with qualified neurologists. Of the 15 patients studied by Greenwald et al,[2] 11 were seen by neurologists.

Factors of error in the diagnosis of JME among neurologists were similar to the observations made in various studies from developing countries.[1],[2],[3],[4],[5],[6] Type of seizures for which patient seeks medical attention may delay diagnosis of JME, if one fails to ask about myoclonic jerks. Generalized tonic clonic seizures may appear as the first clinical event in JME and they may not always show the circadian relation to awakening from sleep that is consistently manifested by the myoclonic jerks.[3],[9] Further more the circadian distribution of GTCS may alter as a result of antiepileptic medication, particularly with clonazepam.[4] Myoclonic jerks can have unilateral onset or may be predominantly unilateral.[3],[6],[9] Patients may be diagnosed as having partial epilepsy if such jerks precede GTCS.[6],[10] This will be confounded if EEG shows focal abnormalities.[10],[11] In JME, absences precede myoclonic jerks and GTCS by 4 to 5 years.[3] These patients are likely to be diagnosed as childhood or juvenile absence epilepsy until JME is revealed by the appearance of myoclonic jerks and GTCS.[6] In a recent study of long term prognosis of typical childhood absence epilepsy, 15% of the total cohort had progressed to JME. Development of GTCS or myoclonic seizures during antiepileptic drug treatment predicted both lack of remission and progression to JME.[12] Absences in JME are markedly different from those of childhood absence epilepsy (CAE) and juvenile absence epilepsy (JAE). The absences in JME are simple absences and impairment of consciousness is mild. The EEG discharge is characteristically different from that of CAE and JAE. The discharge is frequently short and fragmented, the spike and slow wave complexes show interdischarge frequency variations with multiple spikes and other characteristics which are different from those of CAE and JAE components.[3],[13],[14] However, Waltz et al,[15] after thorough analysis of 2000 EEG records of patients with CAE, JAE, and JME, felt that the differences were not statistically significant.

This study suggests that among neurologists the factors of error in the diagnosis of JME were similar to the observations reported from the developed countries, whereas the factor for delay in the diagnosis among practising physicians was the lack of familiarity with the epileptic syndrome.
 

  »   References Top

1.Delgado Escuta AV, Enrile Bacsal FE : Juvenile myoclonic epilepsy of Janz. Neurology 1984; 34 : 285-294.  Back to cited text no. 1    
2.Grunewald RA, Chroni E, Panyiotopulos CP : Delayed diagnosis of juvenile myoclonic epilepsy. J Neurol Neurosurg Psychiatry 1992; 55 : 497-499.  Back to cited text no. 2    
3.Panayiotopoulos CP, Obeid T, Tahan AR : Juvenile myoclonic epilepsy : A 5 year prospective study. Epilepsia 1994; 35 : 285-296.  Back to cited text no. 3    
4.Obied T, Panayiotopoulos CP : Juvenile myoclonic epilepsy : A study in Saudi Arabia. Epilepsia 1989; 30 : 603-606.  Back to cited text no. 4    
5.Penry JK, Dean JC, Riela AR : Juvenile myoclonic epilepsy : long term response to therapy. Epilepsia 1989; 30(Suppl) : 519-523.  Back to cited text no. 5    
6.Panayiatopoulas CP, Tahan R, Obeid T : Juvenile myoclonic epilepsy : Factors of error involved in the diagnosis and treatment. Epilepsia 1991; 32 : 672-676.  Back to cited text no. 6    
7.Murthy JMK, Rao ChM, Meena AK : Clinical observations of juvenile myoclonic epilepsy in 131 patients : A Study in South India. Seizure 1998; 7 : 43-47.  Back to cited text no. 7    
8.Commission on classification and terminology of the International League Against Epilepsy. Proposal for revised classification of epilepsies and epileptic syndromes. Epilepsia 1989; 30 :389-399.  Back to cited text no. 8    
9.Canevini MP, Mai R, Di Mario C et al : Juvenile myoclonic epilepsy of Janz. Clinical observations in 60 patients. Seizure 1992; 1 : 291-298.  Back to cited text no. 9    
10.Lancman ME, Asconape JJ, Penry JK : Clinical and EEG asymmetries in juvenile myoclonic epilepsy. Epilepsia 1994; 35 : 302-306.  Back to cited text no. 10    
11.Amberti V, Greenewald RA, Panayiatopoulos CP et al : Focal electroencephalographic abnormalities in juvenile myoclonic epilepsy. Epilepsia 1994; 35 : 297-301.  Back to cited text no. 11    
12.Wirrell EC, Camfield CS, Camfild PR et al : Long term prognosis of typical childhood absence epilepsy : Remission or progression to juvenile myoclonic epilepsy. Neurology 1996; 47 : 912-918.  Back to cited text no. 12    
13.Panayiotopoulos CP, Obeid T, Waheed G : Absences in juvenile myoclonic epilepsy : A clinical and videoelectroencephalographic study. Ann Neurol 1989a; 391-397.  Back to cited text no. 13    
14.Panayiotopoulos CP, Obeid T, Waheed G : Differentiation of typical absence seizures in epileptic syndromes : a video EEG study of 224 seizures in 20 patients. Brain 1989b; 112 : 1039-1056.  Back to cited text no. 14    
15.Waltz S, Mannagetta G, Janz D : Are three syndromes related genetically determined spike and wave patterns ? A comparision between syndromes of generalized epilepsy. Epilepsia 1990; 31(Suppl): 819(abstract).  Back to cited text no. 15    

 

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