Central nervous system hyperexcitability associated with glutamate dehydrogenase gain of function mutations.
OBJECTIVE
To describe seizure phenotypes associated with the hyperinsulinism/hyperammonemia syndrome (HI/HA), which is caused by gain of function mutations in the enzyme glutamate dehydrogenase (GDH).


METHODS
A retrospective review of records of 14 patients with HI/HA.


RESULTS
Nine patients had seizures as the first symptom of HI/HA, and six had seizures in the absence of hypoglycemia. No electroencephalogram (EEG) background abnormalities were identified. In four patients, EEG recordings during seizures in the setting of normal blood glucose contained generalized epileptiform discharges. EEGs of three of these patients showed 0.5- to 2-second generalized irregular spike-and-wave discharge at 3 to 6 Hz corresponding to eye blinks, eye rolling, or staring. The EEG of the fourth patient consisted of 20 seconds of generalized regular spike-and-wave discharge at 3 Hz in the clinical context of staring and unresponsiveness. In two patients, seizure control worsened with carbamezapine or oxcarbezapine treatment.


CONCLUSIONS
In patients with HI/HA, generalized seizures are common and can occur in the absence of hypoglycemia. The drugs carbamazepine and oxcarbazepine should be used with caution for treatment. Pathogenesis of epilepsy in these patients may be related to effects of GDH mutations in the brain, perhaps in combination with effects of recurrent hypoglycemia and chronic hyperammonemia.
Raizen
David M
DM
Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, USA.
Brooks-Kayal
Amy
A
Steinkrauss
Linda
L
Tennekoon
Gihan I
GI
Stanley
Charles A
CA
Kelly
Andrea
A
D000293:Adolescent; D001786:Blood Glucose / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography; D004829:Epilepsy, Generalized / Q000209:etiology* / Q000235:genetics / Q000503:physiopathology; D005260:Female; D005969:Glutamate Dehydrogenase / Q000235:genetics*; D006801:Humans; D022124:Hyperammonemia / Q000235:genetics*; D006946:Hyperinsulinism / Q000235:genetics*; D007003:Hypoglycemia / Q000235:genetics; D007223:Infant; D009154:Mutation; D012189:Retrospective Studies; D012640:Seizures / Q000175:diagnosis*
D001786:Blood Glucose; D005969:Glutamate Dehydrogenase