Overview

Until now, approximately 60 cases have been published in the medical literature since MPSI was first described in 1995.

A reserarch group at Alder Hey Children's Hospital in the UK have recently completed a survey of MPSI in the UK and Ireland via the British Paediatric Neurology Surveillance Unit (BPNSU). The local paediatric neurologist was asked via email whether they had seen any children with MPSI and then completed an anonymous questionnaire with information about clinical features, investigation results and EEG reports.

15 cases have been reported over the last two years and they are collecting together the data which will be published soon.

This will be the first national case series, although series of 15 to 17 patients from individual centres from different parts of the world have previously been published in the medical literature.

There have been several theories proposed in the past.

Firstly, some believed that there might be a problem with the neurotransmitters (chemical substances responsible for signaling between nerve cells) in the brain, as this would explain why all of the brain could be affected. However treatments such as bromides (which are thought to act via neurotransmitters) have not been effective in all patients and measurement of neurotransmitter levels done in some of the previously reported cases have been normal.

Another possibility was a problem with the channels in the cell membrane which regulate the flow of sodium and potassium in and out of cells. Mutations in these genes, causing conditions known as channelopathies, have in recent years been found to be the cause of several different epilepsy syndromes such as Dravet syndrome also known as severe myoclonic epilepsy of infancy (SMEI). So far there are no reports of these mutations in MPEI.

Other possibilities that have been considered include metabolic conditions- however most previously reported cases of MPEI have been extensively investigated including blood, urine, cerebrospinal fluid testing and muscle biopsy and no cause has been found.

It is also possible that, as in West syndrome, there may be more than one cause of MPEI.

It is believed that it is likely that some cases of MPSI have a genetic basis. This is likely to be sporadic i.e. have just occurred by chance in the child affected, as there are limited reports of affected siblings.

There may be more than one genetic abnormality involved, as all cases of MPEI are not the same- while some children sadly die in the first few years of life with very frequent seizures, there are others whose seizures burn out.

Through the Yahoo MPEI Support group I am aware of a small number of children that have been clinically diagnosed with MPEI and whom also have had an abnormal genetic test result (although none of these results have yet been published to the best of my knowledge)

2 children with abnormality in PLCB1 gene (20p 12.3) - Chromosome 20
1 child with novo translocation 6XX t (5,20) (q11.2; q 11.21) - Chromosome 20
1 child with mitochondrial disease (complex I and III)
1 child with a deletion and replication on Chromosome 16

It is not clear whether these genetic mutations are the cause of the MPEI but they are cerainly very important observations which will certainly help direct further reserach into this condition.