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| LETTER TO EDITOR |
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| Year : 2013 | Volume
: 61
| Issue : 1 | Page : 85-86 |
Periodic lateralized triphasic waves in an adult with isolated hemimegalencephaly
Prabhat Singh1, Vimal K Paliwal1, Zafar Neyaz2, Hira Lal2
1 Department of Neurology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Raebareli Road, Lucknow, Uttar Pradesh, India
2 Department of Radiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Raebareli Road, Lucknow, Uttar Pradesh, India
| Date of Submission | 22-Dec-2012 |
| Date of Decision | 22-Dec-2012 |
| Date of Acceptance | 20-Jan-2013 |
| Date of Web Publication | 4-Mar-2013 |
Correspondence Address:
Vimal K Paliwal
Department of Neurology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Raebareli Road, Lucknow, Uttar Pradesh
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0028-3886.108024
How to cite this article:
Singh P, Paliwal VK, Neyaz Z, Lal H. Periodic lateralized triphasic waves in an adult with isolated hemimegalencephaly. Neurol India 2013;61:85-6 |
Sir,
Hemimegalencephaly is a rare congenital malformation of brain characterized by hamartomatous enlargement of one cerebral hemisphere imparting extreme asymmetry to brain. It usually presents in infancy with seizures, large asymmetric head, development delay, and mental retardation. Rarely, it is diagnosed in adults with epilepsy with or without dysmorphism and mental sub-normality. Different types of electroencephalographic (EEG) abnormalities are known in these patients. We present here an adult with isolated hemimegalencephaly and characteristic EEG abnormality.
A 26-year-old man presented with generalized tonic-clonic seizures since 6 months of age. His seizures remained well controlled on anti-epileptic drugs and recurred only on drug default. He was born normally, full term at home and cried immediately. Since birth, his parents noted mild weakness of left upper and lower limb. He had delayed motor and mental milestones and achieved sitting, standing, walking, and disyllabic speech at 8 months, 1 year, 2.5 years, and 2 years, respectively. He also had poor scholastic performance. He did not report any family member with seizures, facial dysmorphism, or any neurocutaneous syndrome. On examination, he had normal head size and no skin lesion or dysmorphic facial features. Higher mental functions and cranial nerves were normal. Motor system revealed grade 2 spasticity with grade 4/5 power in left upper and lower limb. All deep tendon jerks on left side were brisk and left planter was extensor. Sensory system examination was normal. His electroencephalogram revealed periodic large amplitude triphasic waves in the right-sided leads [Figure 1]. Magnetic resonance imaging (MRI) brain revealed large right cerebral hemisphere with pachygyria and hyperintense right corona radiata [Figure 2]a, thick cortical ribbon on right fronto-temporal lobes and colpocephaly [Figure 2]b, straight and compressed right frontal horn of lateral ventricle and thickened genu on right side [Figure 2]c and normal cerebellum and brainstem [Figure 2]d. | Figure 1: Electroencephalograph obtained by 10-20 international system of electrode placement reveals periodic large amplitude triphasic waves occupying predominantly over right cerebral hemisphere
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 | Figure 2: T2-weighted MRI brain shows large right cerebral hemisphere with pachygyria and hyperintense right corona radiata (a) thick cortical ribbon on right fronto-temporal lobes and colpocephaly (b) straight and compressed right frontal horn of lateral ventricle and thickened genu on right side (c) and normal cerebellum and brainstem (d)
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Hemimegalencephaly is classified as isolated, syndromic, or total. Total hemimegalencephaly involves enlargement of ipsilateral cerebellum and brainstem in addition to the cerebral hemisphere. Syndromic hemimegancephaly includes number of neurocutaneous syndromes, where hemimegancephaly exists in addition to several other features. These syndromes include epidermal nevus syndrome, Klippel-Trenaunay-Weber syndrome, Proteus syndrome, hypomelanosis of Ito, neurofibromatosis, and tuberous sclerosis. Isolated hemimegalencephaly presents with enlargement of one cerebral hemisphere, with normal brainstem and cerebellum, and without any neurocutaneous markers. [1] Three types of electrophysiological abnormality are found in these patients. Most common is periodic high amplitude triphasic waves predominantly involving the enlarged cerebral hemisphere. Asymmetrical burst-suppression pattern is seen in infancy and early age groups. Asymmetrical high amplitude alpha-rhythm like activity with little modification on waking state may also be seen. [2]
| » References | |  |
| 1. | Paladin F, Chiron C, Dulac O, Plouin P, Ponsot G. Electroencephalographic aspects of hemimealencephaly. Dev Med Child Neurol 1989;31:377-83. 
[PUBMED] |
| 2. | Flores-Sarnat L. Hemimegalencephaly: Part 1. Genetic, clinical, and imaging aspects. J Child Neurol 2002;17:373-84.
[PUBMED] |
[Figure 1], [Figure 2]
| This article has been cited by | | 1 |
Evolution of epilepsy in hemimegalencephaly from infancy to adulthood: Case report and review of the literature |
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| Kristin M. Ikeda,Seyed M. Mirsattari | | Epilepsy & Behavior Case Reports. 2017; 7: 45 | | [Pubmed] | [DOI] | |
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