Late-onset myoclonic epilepsy in Down syndrome (LOMEDS): A spectrum of progressive myoclonic epilepsy - Case report.

Cognitive decline and epilepsy are well recognized complication of Down syndrome (DS). Here, we intend to present a case of 28 year old male who presented with progressive mental regression, gait ataxia and myoclonic jerking especially on awakening in morning. His EEG was normal and karyotyping revealed trisomy of chromosome 21. Very few cases had been described in literature of late-onset myoclonic epilepsy in DS. This is first case report from India and our aim is to propose the inclusion of this entity in the spectrum of progressive myoclonic epilepsies but still more cases are yet to be found.

Introduction

Epilepsy is a well-recognized complication of Down syndrome (DS). In literature, “late-onset myoclonic epilepsy in Down syndrome” (LOMEDS), characterized by seizure onset after the fourth decade, myoclonic jerks, occasional tonic–clonic seizures, and progressive dementia, is described. Here, although a bit early onset in comparison to previous studies, we report a patient with progressive dementia, gait ataxia, and myoclonic jerking associated with trisomy of chromosome 21.

Case Report

A 28-year-old male was admitted in our ward in May 2014, who was born of a nonconsanguineous marriage with normal birth history. His developmental history was not clear although as told by his father, he was mentally retarded from his childhood but was able to perform his daily routine activities. From December 2013, they noticed a change in his behavior in the form of apathy and decreased talkativeness. The patient was also giving history of formed visual hallucinations that he sees an imaginary boy who talks to him. There was progressive decline in his memory. Four months after this the patient developed myoclonic jerking, initially segmental involving the right upper limb resulting in dropping of objects from hand (like a glass of water). Later on, these jerks became diffused involving arm, face, trunk, and legs. The jerks occurred mostly at morning awakening, and occasionally at other times of the day. Simultaneously, they found that patient developed imbalance while walking and occasional falls. His voice became progressively slurred.

On examination, we found that the patient have broad forehead, small and low sets of ears, macroglossia, saddle nose, and single palmar crease that are consistent findings in patients with DS [Figures 1 and 2]. Neurological examination revealed horizontal nystagmus, bilateral optic atrophy, dysarthric speech, and gait ataxia.

Figure 1

Image of the patient showing broad forehead, saddle nose, and macroglossia

Figure 2

Image showing Simian crease

Routine investigations including complete blood count (CBC), renal function test, liver function test, serum electrolytes, thyroid profile, serum vitamin B12, venereal disease research laboratory (VDRL), and human immunodeficiency virus (HIV) enzyme-linked immunosorbent assay (ELISA) were all normal. Brain magnetic resonance imaging (MRI) showed mild cortical atrophy and his EEG was normal. Karyotyping revealed trisomy of chromosome 21. We prescribed him sodium valproate and clonazepam. At the last telephone contact (Feburary 2015), we were informed that his cognitive deterioration was slowly progressing, and that the gait ataxia and jerks are still persisting.

Discussion

Veall (1974) in his study of 1,654 patients with DS, showed an increased prevalence of epilepsy with increasing age and underlined the absence of an obvious cause of epilepsy.[1] In late stages of DS, myoclonus may become the most characteristic epileptic symptom. Pedersen mentioned that elderly DS patients could present as myoclonic jerks, with normal EEGs.[2] Dementia with myoclonic epilepsy in elderly patients with DS had been brought into light by various authors (Genton and Paglia 1994, Roberto De Simone 2006).[34] Möller et al. (2001, 2002) have proposed the inclusion of LOMEDS among the possible causes of epileptic myoclonus in the differential diagnosis of adult-onset myoclonic epilepsies.[5]

In contrast to previous studies in which the age of onset was after 40 years, our patient was relatively young and in addition to cognitive decline and myoclonic jerking he was also having ataxia. So we propose this to be included in the category of progressive myoclonic epilepsy (PME) as all the three characteristics of PME (cognitive decline, myoclonus, and ataxia) were present in our patient.

Conclusion

Although LOMEDS is rarely described in literature, advancement of medical science and increased life expectancy of patients with DS might bring LOMEDS into light in future than currently acknowledged. Presence of all the three characteristics of PME in our patient paves the way of inclusion of LOMEDS in the spectrum of PME although more cases are yet to be found.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.