Outline of
Neurosurgery
E. R. Flotte, 2008
Please send comments
and corrections to admin@flotte2.com
General
·
Intractable: failed at least 3 meds. Occurs in 30%
·
Remission: seizure-free off medications for 5 or more
years
Antiepileptics
·
Non-enzyme inducing: Kepra
(po only), Lamictal (po only), Depakote (causes
bleeding?)
·
Tegretol: causes
leucopenia, hepatitis
Status Epilepticus
·
30+ minutes seizure activity or multiple seizures
without regaining consciousness
·
Step-wise:
·
Ativan (4mg x 2
- 0.1mg/kg, IV or rectal) & Dilantin/Fosphenytoin
load (20mg/kg).
·
Phenobarbitol (<100mg/min
up to 20mg/kg) until seizures stop. Watch BP.
·
>30 mins: Intubate and pentobarbital (or Versed) infusion or general anesthesia
Hippocampal Sclerosis
·
AKA Ammon’s Horn Sclerosis
(AHS)
·
Correlated with Mesial
Temporal Sclerosis (MTS) on MRI (↑ FLAIR/T2). Hypometabolism
on PET
·
Correlated with febrile seizures
·
Seen with Timm stain – CA1
& CA3 loss
Hypothalamic
hamartoma
·
Causes gelastic seizures
initially, then complex-partial or generalized. Responds well to radiosurgery.
o
Gelastic seizures: laughing
fits. Other causes: hypothalamic glioma, 3rd ventricle tumor,
temporal lobe epilepsy, infantile spasms, etc.
Tumors
·
Seizure focus is usually in the surrounding brain,
not in the tumor
·
Single or controlled seizures – do lesionectomy. Intractable seizures – lesionectomy
plus intraoperative ECOG and resection of seizure
focus
Cortical Dysplasia
·
With complete resection of epileptogenic
focal cortical dysplasia, 87% have good seizure
outcome
Preoperative Evaluation
Phase I:
Imaging
·
MRI (FLAIR)
If nonlesional then proceed with:
·
PET
o
Ictal PET shows
hypermetabolism in focus. Interictal
PET shows hypometabolism in focus in 70%.
o
Sensitvity in TLE
60-90%
o
Does not correlate with histopathological
changes (eg atrophy)
·
SPECT
o
Subtraction Ictal-Interictal
SPECT shows hypermetabolism in focus
·
Can
coregister T1 MRI with PET, SPECT, grid xray for image guidance (JN3/04)
·
Possibly
MR Spectroscopy, FMRI triggered spike detection
Scalp
EEG/Video-EEG
·
Dense-array EEG. EEG Dipole Analysis
·
Magnetoencephalography
Neuropsychological
Testing
·
Cognitive and functional deficits, memory reserve
Phase II:
Invasive
monitoring
Subdural
Grids & Strips:
·
Scalp EEG fails to localize focus in 30%. Used to
confirm preoperative hypothesis.
·
Standard: 2 placed perpendicular to temporal lobe
(consider 1 medial & parallel)
·
Electrocorticography may
assist in grid placement
·
Low-amplitude high-frequency activity at onset
correlates with good surgical outcome. Electrodes recording higher-frequency
spikes are closer to focus
·
Stereoelectroencephalography:
Stereotactic placement of depth electrodes
Depth
Electrodes
WADA test:
·
Injection of sodium amobarbital
into
·
Speech: arrest not enough, must have
naming errors.
·
Memory:
Uses:
o
1) Memory localization: less reliable than speech.
(Note hippocampal blood supply mainly from PCA)
o
2) Focus localization: able to detect side of eplieptogenic focus in 40-80%, incorrect in <10%,
indeterminate 20-50%. Memory improves
when given on side of focus.
Surgery
Lesionectomy
·
MRI lesion with concordant EEG: 80-90% seizure-free
at 12 months
o
Nonlesional postop
seizure-free 30-50%
Temporal Lobectomy
·
Complications:
o
Anterior choroidal a. can loop into choroids plexus –
avoid coagulating choroid plexus
·
Anterior temporal lobectomy:
o
70-94% Engle I-II.
o
Wiebe S NEJM
2001: Only RCT 58% (complex) seizure-free, 8% off
medicine. 10% adverse effects, 55% visual field deficits
o
Diplopia 19% (due to CN4 palsy, resolves).
o
Extent: 4-5cm in nondominant
lobe, 3.5-4cm dominant lobe.
o
Open choroidal fissure between hippocampus and choroids plexus
(vessels run between choroids plexus & thalamus). Be aware of basal
temporal language area (N5/04)
o
“Temporal
lobotomy”: See N6/04
·
Amygdalohippocampectomy: Transsylvian approach described by Yasargil.
74% Engle class I-II in kids. Versus ATL: No difference in adults, worse
control in peds.
Multiple Subpial Transections
·
Used to make disconnections in eloquent cortex
·
Used alone: 15% seizure-free, 35% improved, 50% unchanged. Combined with resection: 40% seizure-free,
40% improved, 20% unchanged.
·
Used in Landau-Kleffner
Syndrome in which epileptic aphasia develops in previously normal child
Corpus Callosotomy:
·
Indications: Secondary generalized, atonic (drop attacks), infantile hemiplegia,
Rasmussens, Lennox-gastaut.
o
Contraindicated in crossed dominance (left-handedness
with left-sided speech) – obtain WADA in all left-handed patients.
·
Most commonly anterior 2/3rds is sectioned,
interhemispheric approach
·
Complications:
o
Anterior: ¯
spontaneous speech (SMA), nondominant leg paresis
& grasping, urge incontinence (all usually temporary). Permanent speech
deficit with mixed cerebral dominance (speech & motor on opposite sides).
o
Posterior:
interhemispheric disconnection syndrome (¯ tactile sensation & vision on nondominant
side, bradyphrenia, incontinence
o
Complete: as above
+ nondominant hand doesn’t perform commands (can
perform antagonistic actions)
Hemispherectomy
·
Indications: Hemiplegia
with intractable seizures: Rasmussen’s disease, cortical dysplasia,
hemispheric infarct.
·
Anatomic: Complete
resection of hemisphere. Complications: hydrocephalus, superficial siderosis.
·
Functional: Removal
of central cortex and temporal lobe, basal ganglia left intact but disconnected
from cortex, disconnection of contralateral hemisphere. 25% reoperation for
recurrent seizures.
·
Other techniques: Hemispherotomy
(JN:P2/04, JN11/04).
Vagal
Nerve Stimulator:
·
Effective on left side only (reason unknown).
·
Efficacy: All seizure types equally
reduced. 42% reduction in seizures @ 18mo, very few seizure
free. Equivalent to adding another medicine.
o
Can be effective after failed craniotomy (N11/04)
o
Cochrane Database: VNS for partial seizures appears to
be an effective and well tolerated treatment. Adverse effects of hoarseness,
cough, pain, paresthesias, and dyspnea are associated
with the treatment but appear to be reasonably well tolerated as dropouts were
rare.
·
Complications: Coughing, voice changes, throat
pain, drooling, laughing, torticollis, urinary retention. (No cardiac changes
reported.)
Intraoperative Electrocorticography
·
Done either with strips or the “Hellraiser”
·
Under general anaesthesia
avoid benzodiazepines and babituates. Under local use
only narcotics (fentanyl) and droperidol.
Perioperative
·
Taper and discontinue AEDs 24hrs preop.
Continue AEDs 1-2 years.
Radiosurgery
·
Dose limited by optic chiasm and brainstem. Takes >9mos to work; auras or seizures may
increase before decreasing. May take up
to 3yrs before considering retreatment.
·
One
report using 20Gy (N6/04) showed 0/5 improvement with MTS and possibly worsened
cognitive testing. Marseilles group (Regis) report 82% seizure-free and another
12% significantly improved using 25Gy. T2 signal peaks at 1yr.
·
Multicenter trial (led by UCSF) currently ongoing.
Deep
brain stimulation:
of anterior thalamic nucleus and other areas (centromedian
nucleus, STN, hippocampus) being investigated
Text Copyright 2008
Revised 4/14/2008
Please send comments
and corrections to admin@flotte2.com
Disclaimer: This outline
is complied, not original. Sources are being added
retrospectively.
It is intended for
personal educational use by students and residents. It is not intended to guide clinical decision
making. Accuracy and timeliness cannot be guaranteed.