<P> The signs and symptoms of seizures vary depending on the type . The most common type of seizure is convulsive (60%). Two - thirds of these begin as focal seizures and become generalized while one third begin as generalized seizures . The remaining 40% of seizures are non-convulsive, an example of which is absence seizure . </P> <P> Focal seizures are often preceded by certain experiences, known as an aura . These may include: sensory, visual, psychic, autonomic, olfactory or motor phenomena . </P> <P> In a complex partial seizure a person may appear confused or dazed and cannot respond to questions or direction . Focal seizure may become generalized . </P> <P> Jerking activity may start in a specific muscle group and spread to surrounding muscle groups--known as a Jacksonian march . Unusual activities that are not consciously created may occur . These are known as automatisms and include simple activities like smacking of the lips or more complex activities such as attempts to pick something up . </P>

Which of the following is a least likely cause of secondary seizures