Low Serum Pyridoxine Levels Worsen Seizure Control in Adult Epilepsy Patients

Abstract

Background: Vitamin B6 (pyridoxine) is an important cofactor in the process by which glutamic acid decarboxylase (GAD) converts the excitatory, pro-epileptogenic neurotransmitter, glutamate, into the inhibitory, anti-epileptogenic neurotransmitter, gamma-aminobutyric acid (GABA). This concept has been established in infants with pyridoxine-dependent epilepsy as well as adult patients with other epilepsy subtypes who presented with medication-resistant status epilepticus, with both patient groups experiencing cessation of seizure activity following pyridoxine administration. Given our knowledge of the role of vitamin B6 in the conversion of glutamate to GABA, its effect on seizure control in infants with specific epilepsy subtypes, reports of adult-onset seizures associated with vitamin B6 deficiency, and vitamin B6's role in terminating status epilepticus in adult patients with other types of epilepsy, we suspect that low vitamin B6 levels in adult epilepsy patients may correlate with poor seizure control across all epilepsy subtypes. This study seeks to determine whether there is a relationship between pyridoxine levels and the level of seizure control in adults with epilepsy, regardless of their seizure type. Methods: After obtaining institutional review board approval, we prospectively enrolled 32 patients (age range: 25-57 years) with epilepsy who presented to our clinic. Patients who did not meet the study criteria or who were diagnosed with psychogenic non-epileptic seizures (PNES) were excluded from the study (n = 2). Patients were classified as well-controlled (WC) or poorly controlled (PC) based on the absence or presence of a seizure within the last three months, respectively. After classification as WC or PC, pyridoxine serum levels and anti-seizure medication (ASM) levels were drawn in that clinic visit, following patient consent. All patients were contacted regarding pyridoxine and serum ASM levels, and patients that were found to be deficient in pyridoxine were treated with appropriate supplementation. At the end of the recruitment period, we performed analyses to determine if there was a statistically significant relationship between PC status and serum pyridoxine levels. Results: Of 32 patients, two patients were diagnosed with psychogenic non-epileptic events and were subsequently excluded. Of 30 patients, 10 had PC epilepsy. Median (interquartile range) serum B6 levels were 35.8 (26.8-54.2) in patients with WC epilepsy and 17.5 (10.1-41.3) in patients with PC epilepsy (P = 0.11). In the PC group, 6/10 (60%) of the patients demonstrated low serum pyridoxine compared to 3/20 (15%) in the WC group (P = 0.03). Conclusion: There was a statistically significant relationship between serum pyridoxine levels and seizure control. If appropriate, pyridoxine supplementation should be considered, especially in critically ill adult patients with refractory or PC seizures despite good adherence to ASMs.