Pyridoxine-dependent seizures

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Read about pyridoxine-dependent seizures, a rare form of epilepsy that occurs when the body cannot metabolize vitamin B6.

Key points

  • Pyridoxine-dependent seizures (PDS) occur when the body cannot metabolize vitamin B6.
  • Seizures can start in the womb before birth or as late as two years old.
  • PDS does not respond to anti-epileptic medication. Instead, your child will need to take vitamin B6 every day for months or even years.

"Vitamin B6 dependent epilepsy" or "pyridoxine-dependent seizures" (PDS) are a rare but intractable (meaning they cannot be controlled with anti-epileptic medication) type of seizures in infants. In such cases, the body is not lacking in vitamin B6 (also known as pyridoxine), but it has difficulty metabolizing the vitamin and therefore requires extra. Vitamin B6 is important for processing amino acids, the building blocks of proteins.

When do pyridoxine-dependent seizures start?

PDS usually start within a few hours of birth. However, the seizures can also start before birth, while the baby is still in the womb, in which case the mother will feel a hammering sensation within. The seizures can also develop as late as when the child is two years old.

What are the symptoms of PDS?

Apart from uncontrollable seizures, children with PDS may have other symptoms such as swelling of the brain, slow development and intellectual disabilities.

How are PDS diagnosed?

PDS may be verified by the doctor giving the child vitamin B6 orally (by mouth) or intravenously (through a vein) while recording the EEG. If the seizure stops and the EEG patterns improve, this indicates that the seizures are pyridoxine-dependent. While intravenous injections of vitamin B6 can reverse seizure activity immediately, it may take several days for the EEG to become normal.

How are PDS treated?

PDS do not respond to anti-epileptic medication. Instead, your child will need to take vitamin B6. This is available in tablet or liquid form or through injection.

If your child is found to have PDS, they will need to take extra vitamin B6 every day for many months or years, possibly for the rest of their life. The doctor will discuss this with you.

Some doctors suggest trying vitamin B6 injections on any baby with unexplained intractable seizures. Some doctors may also try vitamin B6 in older children with difficult-to-control seizures, on the principle that it may help and is unlikely to do any harm.

What are the side effects of PDS treatment with vitamin B6?

Side effects of vitamin B6 include nausea, headaches and drowsiness.

When used over the long term, vitamin B6 may cause peripheral neuropathy, a condition in which the nerves that carry information back and forth between the CNS and the body are damaged and no longer work properly. This can cause pain, numbness or difficulty controlling the muscles.

Last updated: February 4th 2010