Download - Vagal Nerve Stimulation for epilepsy
VAGAL NERVE STIMULATION
INTRODUCTION
• a new non-pharmacological antiepileptic therapy, approved in 1997 by the US Food and Drug Administration
• adjunctive therapy for adults and adolescents over 12 years of age whose partial onset seizures are refractory to antiepileptic medications.
Schematic drawing of the general placement of the vagusnerve stimulation system and bipolar stimulating lead
VNS Therapy: components
• Programmable pulse generator• bipolar lead• programming wand with accompanying
software • tunnelling tool • hand-held magnets
PULSE GENERATOR&BIPOLAR LEAD
The Model 400 NCP Tunneling Tool is used during implantation to
create a subcutaneous path between the device in the chest and the vagus nerve in the neck
Programming wand
MAGNETS
procedure
• Incisions1&2• Electrode pin placing• Vagus nerve connection• Generator connection• Checking system• Setting parameters• Replacement of generator
VNS
Lead connections close-up
Use of programming wand to adjust generator stimulatorparameters
programming
stimulation parameter settings
Vagus nerve anatomy andmechanism of action of VNS
Mechanism of action
• NTS-PBN-THALAMIC CIRCUIT• HIGH FREQUENCY STIMULATION-
UNMYELINATED FIBRES-EEG DESYNCHRONIZATION
• LOW FREQUENCY STIMULATION-MYELINATED FIBRES-EEG SYNCHRONIZATION
Mechanism of action
• In 1993, McLachlan posited that VNS decreased cortical epileptiform activity indirectly by influencing the reticular activating system.
• Krahl et al demonstrated that the anticonvulsant effect of VNS could be reduced experimentally by lesioning the locus ceruleus.
• Henry et al reported that VNS causes measurable changes in cerebral blood flow in the cerebellum, thalamus, and cortex and may activate inhibitory structures in the brain
Indication
• FDA indication: "... adjunctive therapy in reducing the frequency of seizures in adults and adolescents over 12 years of age with partial onset seizure, which are refractory to antiepileptic medications."
• Although the FDA indication for VNS excludes other types of epilepsy (ie, those without partial seizure), most epileptologists agree that the VNS indications are probably broader than that
indications
• CPS• GTCS• LGS• EPILEPTIC ENCEPHALOPATHIES• ATONIC • ABSENCE• JME
Efficacy, LABAR etal
• 24 pts,-medication resistant GTCS• Idipathic-7,symptomatic -17• Seizure frequency reduced by 46% after 3
months,• 11 pts had >50% reduction
Hosain etal in LGS
• AGE 4-14,13 PTS• 52% REDUCTION IN SEIZURE RATE IN 6
MONTHS• 3 HAD >90% REDUCTION• 2 HAD >75% REDUCTION• ONE HAD >50% REDUCTION
MURPHY etal,
• 12 children • 4-16 yrs,medically&surgically refractory
seizures• 5 had >90% red.• 4 pts able to reduce AED doses
MURPHY etal,
• 60 children ,pharmacoresistant epilepsy,27%-GTCS
• After 6 months med.red.in frequency of seizures 31%
• After 12 months 34%• After 18 months 42%
PARKER etal,
• 16 children with epileptic encephalopathy• 50% red. In 1yr significant improvement in• EEG• adaptive behaviour• QOL• language performance
PATWARDAN etal,
• 38 children• 10-18 months follow up• Seizure reduction in atonic-80%,absence -
65%,CPS-48%,GTCS-45%
Sirven etal,
• Refractory epilepsy in 45 pts• 50 yrs or older• After 3 months,12 had >50% red• At 1 yr 21 had >>50% red
RESPONDER RATES.E03,E05 STUDIES
EFFICACY
LONG TERM CONTROL
responder rates for several of the newer AEDs with VNS
compares responder rates for several of the newer AEDs with VNS. Odds ratios (OR) and associated 95% confidence intervals for at least a 50% decrease in seizure frequency in response to gabapentin,lamotrigine,topiramate,tiagabine, or VNS
OTHER BENEFITS
Non epileptic indications
• ALZHEIMER’S DISEASE• OBESITY• BIPOLAR DISORDER• OCD• PTSD• CHRONIC MIGRAINE• ANXIETY DISORDERS
Safety&tolerability
• Mechanical and electrical safety• Environmental considerations• Laboratory values• Long-term safety and tolerability,
(mortality,pregnancy,swallowing defects,obstructive sleep apnea)
• Effects on mood and behaviour in patients with epilepsy
safety
Adverse events,E05 STUDY
Clinical use of VNS for epilepsy
Clinical usage,programming
• Increments of current• Reviewed after 6-9 months• Off time reduction• Rapid cycling
Efficacy of rapid cycling vagus nerve stimulation in
pharmaco-resistant epilepsy
• Rapid cycling is more efficacious than SC in pediatric group, but not in adult group. Lennox-Gastaut syndrome in pediatric patients yields a greater response to RC.
Suresh G GURBANI etal,Neurology Asia 2004;
To conclude
• Untill 2008;nearly 43,000 pts were treated with VNS WORLD WIDE
• Patient education• Surgical implantation• Follow up programming visits• Titrate stimulation