Pediatric Neurosurgery

SURGICAL MANAGEMENT OF EPILEPSY

Definition of Epilepsy

Epilepsy implies a periodic recurrence of seizures with or without convulsions

Seizures result from an excessive synchronous discharge of cortical neurons and is characterized by changes in electrical activity

A convulsion implies violent, involuntary contraction(s) of the voluntary muscles

Classification of Seizures: Generalized Seizures

• Absence seizures
• Tonic-clonic seizures
• Myoclonic seizures
• Tonic seizures
• Clonic seizures
• Atonic seizures

Classification of Seizures: Absence (Petit Mal)

• Brief alterations of awareness
• Activity arrest, starring, automatisms
• Pick-up where they left-off
• Average age 8-10years
• Classic EEG Pattern of 3Hz/sec
• Females slightly more than males
• Hyperventilation provokes onset

Classification of Seizures: Tonic-Clonic

• Any age onset and M=F
• Stiff extension of body/extremities followed by violent, rhythmic, symmetric movements
• Alteration of consciousness followed by confusion and sleepiness
• Changes in respiration, bladder and bowel

Classification of Seizures: Myoclonic

• Brief, random, lightning-like movements
• May occur singly or in clusters
• Seconds in duration, no post-ictal changes
• Various age onset
• Can be resistant to therapy

Classification of Seizures: Tonic

• Symmetric, rhythmic movements of extremities as in Tonic/Clonic seizures
• Often occur out of sleep

Classification of Seizures: Atonic

• Abrupt loss of tone
• Frequently associated with trauma
• Positive alteration consciousness with variable post-ictal changes

Classification of Seizures

• Partial seizures
• Simple partial seizures
• Complex partial seizures
• Impaired consciousness at outset
• Simple partial evolving to lost consciousness
• Partial seizures evolving to general tonic-clonic seizures (GTCS)

Classification of Seizures: Simple Partial

• Often called Benign Rolandic
• Hallmark is preservation of consciousness
• Classic pattern on EEG
• M=F, average age onset 7-8
• +/− therapy necessary
• Often “outgrown”
• May not be “so benign”

Classification of Seizures: Complex Partial

• Change in consciousness
• Most common epilepsy in children
• Automatisms, deja vue, auras or alice in wonderland changes seen
• Focal motor movements of any limb
• Variable duration and severity
• Any age onset

Mechanisms of Action: Antiepileptic Drugs

• Sodium channel effects
• Potassium channels and GABA release
• GABAergic effects
  • Precursors, mimicry, and transporters
• Glutamate regulation-neuroprotection
• Calcium channels and transmitter release

Patient Typically Not Considered Surgical Epilepsy Candidate Unless:

• They have failed at least 3 adequate anti-convulsant trials
  • Definition of failure varies
• EEG confirming epilepsy
• Recent MRI
• Family/patient willing to consider surgery

Etiology

• Focal
  • Lesion
  • Anatomically Normal
  • Temporal
  • Extra-Temporal
• Multi-Focal/Generalized

Epilepsy Associated with Cortical Malformation:

• 20% of epilepsy patients
• Mental retardation
• Autism
• Neuropsychiatric syndromes

Cell Migration Disorders:

• Heterotopias - A failure of neuronal migration from the periventricular matrix to the cortex; asymptomatic or mental retardation or seizure
• Agyria - No gyri (lissencephaly) or a few malformed gyri (pachygyria)
• Polymicrogyria - Excessive number of gyri are formed with shallow sulci; sporadic (congenital ischemia/hypoxia, infection) or familial; asymptomatic, mental retardation or seizure
• Focal cortical dysplasia

Success

• Temporal lobe epilepsy
  • 90% were seizure free
  • 98% had a >90% reduction in seizures¹
• Extra-temporal lobe epilepsy
  • 70% were seizure-free²

1. Cukiert et al: Neurosurg Focus. 2002 Oct 15;13(4):ecp2
2. Kazemi et al: Epilepsia. 1997 Jun;38(6):670-7.

Multi-focal Epilepsy

• Temporal lobe epilepsy
  • 90% were seizure free
  • 98% had a >90% reduction in seizures¹
• Extra-temporal lobe epilepsy
  • 70% were seizure-free²

1. Cukiert et al: Neurosurg Focus. 2002 Oct 15;13(4):ecp2
2. Kazemi et al: Epilepsia. 1997 Jun;38(6):670-7.

VNS Therapy

• Implantable pulse generator and lead
• Mild electrical pulses applied to the left vagus nerve in the neck send signals to the brain
• Automatic intermittent stimulation
• Magnet use allows patient/caregiver
  • On-demand stimulation
  • On-demand side effect control
• Simple in-office programming
• Assured compliance

VNS Surgical Technique

• Creation of left chest sub-cutaneous pocket
• Cut-down to left vagus nerve
• Attachment of lead to nerve
• Tunneling on lead
• Lead test
• Programming
• Closure