Dravet syndrome (DS) is a devastating form of pediatric seizure disorder (epilepsy), often related to abnormalities of one of the genes that controls sodium channel function in the brain (SCN1A). Most children with DS experience continued seizures even with optimal treatment of currently available anti-seizure therapies \[1\]. Many of these seizures are prolonged, and can be life threatening.

This pilot study will assess the efficacy of verapamil in improving control of seizures in children and young adults DS. This will be done by adding verapamil as open label adjunctive therapy to medications already being given. Investigators will assess the effect of verapamil therapy on seizure control and on signs of autonomic dysfunction observable to the parents/guardians. Signs of autonomic function include body temperature regulation, sweating, heart rate, pupil size, and flushing of the skin. Iannetti, et al reported treating 2 children with clinical DS (one with an SCN1A mutation) with verapamil as adjunctive therapy \[2\]. Both children had a positive clinical response persisting for a number of months. No adverse effects were noted. We have treated an additional 4 children with DS with verapamil. There have been no significant adverse effects; 3 of 4 have experienced improved seizure control for months also.

Verapamil has been shown to affect autonomic tone in patients with cardiac disorders (eg. high blood pressure, heart attack). It alters the balance between parts of the autonomic nervous system's function (called sympathetic and parasympathetic function) with a shift toward decreased sympathetic tone and increased parasympathetic (vagus nerve) tone \[8, 9, 10\]. Verapamil is used as an effective agent to treat certain types of autonomic headaches in both adults and children. In cluster headaches, autonomic symptoms (tearing, nasal congestion, facial sweating, papillary constriction) are prominent; verapamil is an accepted treatment \[11, 12\].

Intense emotion triggers seizures in a subset of children with DS. Modulation of autonomic function is likely an integral part of seizure threshold in those so affected. Children with DS have a higher rate of signs of abnormal autonomic function than do controls \[13\]. Cardiac autonomic control is also altered in these children, with a shift in the balance between sympathetic (relatively overactive) and parasympathetic (relatively less active) tone \[14\]. Similar findings have been identified in adults with intractable epilepsy and children with partial epilepsy \[15, 16, 17\]. Verapamil's action in stabilizing the balance of sympathetic and parasympathetic tone may play a role altering autonomic tone abnormalities in children with DS as well. This may be a part of the mechanism that leads to improved seizure control.

Verapamil has been in clinical use for \~ 25 years. The FDA has granted an Investigational New Drug approval for use of this medication in this population of children and young adults. Investigators propose to add it to the patient's existing medications, and evaluate potential improvement in seizure control. Potential side effects will be screened. Investigators will monitor liver function with blood tests as well as concentrations of anti-seizure medications. Verapamil and nor-verapamil levels will be assessed twice also. Testing of heart rhythm (EKG) will be done before the study starts and twice more during the study.