Migrating partial epilepsy in infancy. Malignant migrating partial seizures in infancy (MMPSI)
Incidence
The incidence of the syndrome is unknown. This is a newly-described epilepsy starting in very early childhood. It seems to be a very rare type of epilepsy. Some familial case or consanguinity has been reported.
Clinical Characteristics
Malignant migrating partial seizures in infancy is a rare, age-specific epileptic encephalopathy. It is characterized by onset before age 6 months, virtually continuous multifocal seizures with ictal electrical encephalographic activity shifting from one hemisphere to the other, no identifiable immediate or remote causes, intractability to antiepileptic drugs, and developmental arrest. The age of onset for migrating partial seizures in infancy ranges from 13 days to 7 months, and frequency increases progressively over a mean period of a few weeks (7 days to 3 months). Between 1 month and 10 months of age, the full pattern of the disorder is reached. Seizures are then almost continuous, and the patients experience psychomotor deterioration. It is considered an epileptic syndrome. The course is characterized by clusters of seizures lasting several to a few weeks, during which the infant deteriorates considerably, and followed by disappearance of seizures during a few weeks with slow improvement of the condition. Between seizure clusters, infants are floppy, drooling, often somnolent, and unable to drink and swallow. Microcephaly progressively occurs. Only patients whose seizures are brought under control acquire the ability to reach for objects, recognize their surroundings, and, eventually, walk. No cause has been found to explain this type of epilepsy until recently. Mutations in the KCNT1 gene have been found in several individuals with these condition and are the most common cause of MMPSI. Recently another gene mutation TBC1D24 was found responsible for familial MMPSI. Also SCN1A mutation was found associated with this condition as well. All tests, including brain scans, blood and urine tests, skin and muscle biopsies and genetic tests are usually normal. It is not due to any ‘birth injury’ and it does seem to run in families in some cases. It is possible that a child’s development may show some progress if the seizures can be controlled for a number of months. However, this is very rare. Even if some development does occur, the child’s developmental will not ‘catch up’. They will still have learning difficulties. The learning difficulties are usually severe. The prognosis or outcome is usually very poor. This is because the seizures never come under control for more than a few days or a week at a time. Sometimes they are never controlled and continue to occur daily. In addition, most children show very little developmental progress. No child with this condition has ever shown a completely normal development.
Precipitants
None known.
Provocation Tests
None known.
Diagnostic Procedures
It is a clinical-EEG diagnosis. No cause has been found to explain this type of epilepsy until recently. Mutations in the KCNT1 gene have been found in several individuals with these condition and are the most common cause of MMPSI. Recently another gene mutation TBC1D24 was found responsible for familial MMPSI. Also SCN1A mutation was found associated with this condition as well. All tests, including brain scans, blood and urine tests, skin and muscle biopsies and genetic tests are usually normal.