There is variation in the literature with regard to dosage regimens. Prednisone mg/kg/day to 1 mg/kg/day PO is commonly reported, followed by gradual taper over 3 to 6 weeks. Use of IV methylprednisolone for a few days may precede oral corticosteroid use. NOTE: Following biopsy to confirm diagnosis, corticosteroids are usually instituted soon afterward as an adjunctive measure; removal of the suspected offending agent /cause is the primary treatment. While many case reports suggest a possible net benefit to the use of corticosteroids, some experts advocate for more prospective study of their value.
Valproic acid was first synthesized in 1882 by Beverly S. Burton as an analogue of valeric acid , found naturally in valerian .  Valproic acid is a carboxylic acid , a clear liquid at room temperature. For many decades, its only use was in laboratories as a "metabolically inert" solvent for organic compounds. In 1962, the French researcher Pierre Eymard serendipitously discovered the anticonvulsant properties of valproic acid while using it as a vehicle for a number of other compounds that were being screened for antiseizure activity. He found it prevented pentylenetetrazol -induced convulsions in laboratory rats .  It was approved as an antiepileptic drug in 1967 in France and has become the most widely prescribed antiepileptic drug worldwide.  Valproic acid has also been used for migraine prophylaxis and bipolar disorder.