Pyridoxine dependent epilepsy: a suggestive electroclinical pattern

Abstract

Aims-To determine if there is an electroencephalographic pattern suggestive of pyridoxine dependent epilepsy that could be used to improve the chances of early diagnosis. Methods-A retrospective study was made of all the clinical records and electroencephalograms of neonates identified with pyridoxine dependent seizures between 1983 and 1994, at this hospital. Neonates whose seizures began after more than 28 days of life were excluded; in all, five patients from four families were studied. Follow up ranged from 2 to 10 years. Results-A history of miscarriage and neonatal death during an epileptic seizure had occurred in the siblings of two families. One mother reported rhythmic movements of her child during the last month of pregnancy. At birth, all babies were hypotonic; four had decreased visual alertness. All babies were agitated, irritable, jittery, hyperalert, and exhibited sleeplessness and a startle reaction to touch and sound. Age of onset of seizures varied from 30 minutes to 3 days. Seizures of various types were recorded in all cases on EEG tracings, including spasms, myoclonic seizures, partial clonic, and secondary generalised seizures. Burstsuppression patterns occurred in three cases, and a combination of continuous and discontinuous patterns in two others. Bilateral high voltage delta slow wave activity was observed in four patients. Psychomotor delay was severe in three patients, moderate in one, and mild in one. Conclusions-There is an identifiable EEG pattern that is highly suggestive of pyridoxine dependent epilepsy. Pyridoxine dependent epilepsy is probably underdiagnosed. (Arch Dis Child Fetal Neonatal Ed 1999;81:F125-F129)

Pyridoxine-dependent epilepsy initially responsive to phenobarbital

“…Atypical cases, however, have been reported such as late-onset PDE starting after 19 months of life, seizures that initially respond to very small doses of pyridoxine but then later require pharmacological doses 8 and epileptic conditions that initially respond to anticonvulsants but after a certain period of time respond only to pyridoxine, challenging its diagnosis 9 .…”

“…According to this test, patients with PDE would present an immediate improvement of the EEG pattern after the endovenous administration of pyridoxine 9 . The dose of pyridox- In our patient, endovenous administration pyridoxine diagnostic test was not performed since its intravenous formulation was not available at that time.…”

“…Electroencephalographic fi ndings can be, as well, very heterogeneous, with abnormal background activity, no sleep organization, discontinuous EEG with suppression burst-like pattern and spike and polyspike foci 9 . In our patient, EEG showed a discontinuous suppression burst-like pattern which disappeared after a therapeutic trial with pyridoxine.…”

“…Pyridoxal phosphate, the active metabolite of pyridoxine, is the coenzyme of glutamate decarboxylase, the rate-limiting enzyme for the production of GABA from glutamate 9 . However laboratory and genetic studies are still inconclusive 7 .…”

“…The only way to confi rm its diagnosis is through a formal trial of withdrawal. The other certainty in this disorder is that pyridoxine has to be continued for life [1][2][3][4][5]8,9 .…”