E. R. Flotte
MD, 2009
Please
send comments and corrections to admin@flotte2.com
Awake Craniotomy & Cortical
Mapping
·
Sedatives:
Versed, Thiopental
·
Narcotics
·
Nitrous
oxide: Avoid with pneumocephalus. Stop before dural closure to prevent tension
pneumocephalus.
·
Ketamine increases CBF
·
Sodium
thiopental most rapidly lowers ICP (faster than other agents or
hyperventilation)
·
Dexmedetomidine (Precedex):
α2-agonist, anxiolytic, analgesia, “cooperative
sedation”. Used in awake craniotomy, NICU. (ON7/05)
·
Paralytics
o
Succinylcholine: 1mg/kg – 3.5 to 5cc, lasts 5-10min. do not
use with spinal cord injury, hyperkalemia
o
Pavulon reversal: Neostigmine
(2.5-5mg IV) + atropine (0.5mg/mg neostigmine) or Robinul (0.2mg/mg neo). Takes 20 min
·
Propofol:
o
Propfofol Infusion Syndrome
(PIS): pediatric and adults patients. Causes rhabdomyolysis,
myoglobinuria. Increased CK, serum triglycerides,
LFTs, renal failure. Doses > 4 mg/kg/hr
o
Not
approved for < 16yo.
·
ASA Class estimates patient physical status (American
Society of Anesthesiologists)
·
Awake and/or fiber-optic
intubation: used in patients with severe cervical
spinal cord compression or instability to avoid injury during intubation
·
Double-lumen endotracheal tube: used for thoracotomy (above T8), thoracoscopy
·
Neuro-monitoring: Avoid inhalation agents, BZDs, barbs;
use nitrous or narcotics, short-acting muscle relaxants (not for MEPs)
o
Check
family history
Air
Embolism
·
Occurs when venous pressure is lower
than atmospheric pressure and the venous system is open to the atmosphere.
·
Most likely to occur in the sitting
position
·
Preparation: CVL, precordial doppler
·
Detection: precordial doppler (most sensitive), ¯ EtCO2 (earliest),
FEN2,
·
Cardiac: hypotension, ¯
CO,
PAP,
pulmonary vascular resistance, ventilation-perfusion mismatch.
·
Treatment: Lower the head-of-bed,
cover wound with wet laps, aspirate air through central
line, 100% O2.
·
Intubation/Extubation: 100mg lidocaine IVP, 100% O2 x 5min.
·
Tube:
20-22cm at gum line, tip 5cm above carina
·
PCWP
<12, PA 15-30/4-12, CI 2.8-4.2
·
Afib/Aflutter: Verapamil
(5mgx2), Diltiazem (0.25mg/kg 10-20mg). (adenosine, procainimide; digoxin for
flutter) If unstable cardiovert 100J.
·
Other SVT: Vagal maneuver,
Adenosine (6mg-12mg-12mg), verapamil, diltiazem
·
Vtach, Vfib: Pulseless:
Epi (1-3-5mg); Other: Lidocaine (1mg/kg q5m x 3), procainamide (20-30mg/min to 12mg/kg), bretylium
(10mg/kg q5m x 3)
·
Asystole: Epi,
atropine (0.5mg x 4)
·
Bradycardia: atropine
·
Clopidogrel with
aspirin is recommended for unstable angina or minor myocardial infarction; ticlopidine is not recommended
·
Nipride: onset seconds, Follow thiocyanate levels if used >24hrs. 0.3-10mg/kg/min.
Avoid in pregnancy
·
Nitroglycerin:
10-20 mg/min, 0.4mg SL q5m x 3
·
Both
raise ICP.
·
Nicardipine (Cardene)
·
Hydralazine: onset 3-5min,
duration 2-4hrs. OK in pregnancy. SE: tachycardia. IM 10mg, IV 20-40mg prn.
·
Labetalol: onset 5m, duration
3-3hrs; 20-40-60-80mg IV, 200mg po bid
·
Esmolol.
·
Vasotec: 1.25-5mg q6hrs prn
·
Types:
hypovolemic, cardiogenic,
septic, neurogenic, anaphylactic
·
Dopamine:
2-20 mg/kg/min, b>ab.
·
Dobutamine: 2.5-10mg/kg/min,
b only (inotrope, BP
unchanged). Use for cardiac failure if normotensive.
·
Palpable
pulses: radial 80, femoral 70, carotid 60
·
Cause
pancreatitis, immunosuppression, osteoporosis, gastrointenstinal
ulcers, Cushing’s syndrome
·
Must
be weaned after chonic use
·
Stress
dose given for surgery or other stressors
·
Addisonian crisis:
hydrocortisone (Solucortef) 100mg IVP then 50mg q6h
(not Solumedrol)
·
Treatment:
Epinephrine 1:1000 5ml SQ, Benadryl 50mg IM, Decadron
10mg IV
·
Urticaria: Benadryl 50mg PO/IM
+ Cimetadine 300mg PO/IV
·
Vasovagal reaction: hypotension,
bradycardia. Tx: Atropine 0.75mg IV, q 15min to 3mg
Hyperthermia / Fever
·
Ice
down patient, cold gastric lavage, cold IF fluids
·
Neuroleptic malignant syndrome:
On Parkinsons meds or neuroleptics,
given Haldol, Phenergan
DVT
·
Incidence in neurosurgical patients:
15-20%
·
May be increased in craniotomies due
to release of brain thromboplastin
·
Calf
vein thrombosis has <1% risk of PE, however they may
progress to DVT
·
Prophylaxis: Heparin 5000 U SQ BID, Lovenox 30mg SQ BID.
TEDs/SCDs (do not use if DVT is present)
o
ACCP
guidelines: fondaparinux is a alternative to
low-molecular-weight heparin (LMWH), because it is equally safe and effective
but has a longer half-life, a more predictable response, and fewer adverse
effects
o
Moderate-risk
surgical patients: Heparin 5000mg SQ BID or LMWH (less than 3,400 U once daily)
o
High-risk
surgery patients: Heparin 5,000 U SQ TID or LMWH more than 3,400 U daily
o
Aspirin
is not recommended
·
Diagnosis:
o
Doppler
ultrasound: Standard
o
Clinical
diagnosis (calf tenderness, warmth) is unreliable.
o
The fibrinogen uptake test and impedance plethysmography
have low accuracy and are not recommended
o
Contrast venography has high sensitivity
but limited availability and questionable use for small distal thrombi and high
patient discomfort. Use is limited to research
·
Treatment:
Bedrest x 10days, then careful ambulation. 3-6 months
full anticoagulation then low-dose coumadin (INR 1.5-2).
o
Three randomized trials of anticoagulants vs no anticoagulants in
DVT showed no benefit with heparin and coumadin
(combined all-cause mortality: anticoagulants = 6/66, un-anticoagulated
controls = 1/60, P = .07).
o
No RCT of LMWH or thrombolytics have
been done; they have not been proven safer or more efficacious than unfractionated heparin. Thrombolysis
causes more major and fatal bleeds than heparin and is no more effective in
preventing PE (CundiffDK 9/04).
o
IVC (Greenfield) filter
Pulmonary Embolism
·
Diagnosis:
o
V/Q scan:
§
Normal
scan rules out PE.
§
High
probability (88% true positive) then treat.
§
Low
or moderate probability then obtain leg dopplers
and if positive then angiogram to confirm.
o
o
Angiogram
·
Treatment: anticoagulation or IVC (
Fat
embolism
·
Occurs 12-48hrs post-injury
·
Symptoms: dyspnea,
petechiae over thorax, tachycardia, tachypnea.
·
Labs: serum lipase in 50%. Look for fat in blood,
urine. No specific test.
·
Cerebral embolism (causing confusion,
somnolence, seizures) does not occur without lung symtoms unless a PFO or ASD exists.
·
Treatment: O2, PEEP. Steroids
controversial.
·
Aminoglycosides/Gentamycin: Poor CSF penetration.
SE: nephrotoxic (ATN), ototoxic,
vestibulitis, worsens myasthenic
crises,. Coverage: Gram (-) (no strep).
·
Sinus
entry: Gentamycin, Clindamycin
·
A
meta-analysis of eight randomized clinical trials (RCTs) showed that
prophylactic antibiotics reduce rates of postoperative infection by
approximately 75% after craniotomy (Barker FG N1994)
·
AG
= Na – (Cl + HCO3)
·
Osm = 2(Na+K) +
BUN/2.8 + Glu/18
·
Hyponatremia: 1.0-1.5 meq/L/hr, 25meq/L/d, 3% Na 25-50cc/hr + Lasix
·
SIADH
o
Diagnosis:
Na<134, Osm<280, UNa
>50.
o
Treatment:
Fluid restriction <1L/d. 3% NaCl. Chronic: demeclocycline (300mg po q8°) or
lithium
o
Versus
cerebral salt wasting: SIADH has ↓↓ serum Na, ↓ or wnl BUN/CR, ↑ plasma volume, ↑ CVP/PCWP, no
dehydration signs
·
Diabetes
Insipidus (DI)
o
Treatment:
1/2NS, DDAVP/desmopressin (0.5-4 μg
IV°). Chronic: Intranasal DDAVP (10-40μg BID)
·
Hyperkalemia: 10% CaGluconate 5-10cc over 2m; 1 amp HCO3; 5-10U regular
insulin + 1 amp D50; Kayexalate
·
Fresh Frozen Plasma
·
Vitamin K: 10mg IM. PT reversal requires 6-12
hrs. (Do not give IV)
·
Prothrombin complex concentrate reverses coumadin 5x more quickly than FFP
·
Transfusion Reactions
·
Recombinant activated Factor VII (rFVIIa): used for quick
coagulopathy reversal
DIC
·
Labs: Increased PT, PTT & Bleeding
Time. Platelets <100K.
d-dimer, fibrin degradation
products (FDPs >40g/ml). ¯
fibrogen (<100mg/mm3)
= best correlation ().
·
Treatment: FFP ±
Heparin (thrombotic)
(cryoprecipitate if fibrinogen is low, platelets if low)
·
Workup:
antithrombin III, protein C, protein S, APC
resistance, factor V Leiden, plasminogen, fibrinogen,
aPL antibodies, ANA panel, anti-DNA antibodies, cryoglobulins, homocysteine,
SPEP/UPEP, hemolysis screen, rheumatoid factor.
Pregnancy test.
·
Perioperative Management
o
Mechanical
valves: stop coumadin 2-3d preop, admit and heparinize.
o
A-fib:
stop 4-5d preop. Can restart 5d
postop
o
Bleeding
time not predictive of intraoperative bleeding
o
Brain
tumors reportedly carry no higher risk of hemorrhage with anticoagulation
o
Stop
coumadin, heparinize, and stop heparin 6hrs prior to
angiography, myelograpy, or surgery
·
Coumadin
o
Always preheparinize
before starting coumadin (decreases proteins C&S initially causing hypercoaguability).
o
INR: Mechanical Heart valve: 3-4. All
other (DVT, TIA, afib, PE): 2-3.
·
Heparin
o
Increases Antithrombin
III.
o
IV: 5000U bolus then 1000U/hr. SQ:
5000U Q8h.
o
Causes thrombocytopenia (use lepirudin/Refludan).
o
Protamine:
1mg reverses 100U heparin.
·
Low molecular weight heparin (LMWH)
o
AKA fractionated heparin
o
enoxaparin
(Lovenox): 30mg SQ BID. nadroparin (Fraxiparin)
0.3ml SQ. dalteparin.
o
Protamine can reverse 60% of effect
o
Versus SQ heparin: greater bioavailability, more
predictable anticoagulation, lower risk
·
Antiplatelets: Clopidogrel, ticlopidine, aspirin
o
antithrombotic therapy for coronary
artery disease, stroke, etc: because of many adverse effects which are
sometimes fatal, ticlopidine is no longer recommended
for coronary interventions when other treatments are available. Clopidogrel plus aspirin is now recommended for most
patients with unstable angina or minor myocardial infarction
o
Reversal:
Platelets, repeat after 6-8 hours
o
Assays
exist to determine platelet inhibition
·
GP IIb-IIIa inhibitors: Integrellin
(eptifibatide), amaxicab (Reopro), tirofiban (Aggrastat)
Fluids
·
Hetastarch: Cheaper than
albumin. Possible anticoagulant effect at high dosage (>500 cm3/d)
Nutrition
·
Postoperative ileus
treated with dietary restriction, NG suction for symptomatic relief
·
Ogilvie’s syndrome: acute massive
dilation of the cecum and distal colon. Normal small
bowel sounds. Increased with PCA. Diagnosis: KUB. Requires rectal tube,
colonoscopy.
Alcohol
·
Wernicke’s syndrome
o
Symptoms:
Triad: gait ataxia, nystagmus/opthalmoplegia,
confusion. (also
hypothermia). Due to thiamine
deficiency. Ocular problems recover 1st. Usually
reversible. IV glucose worsens – always give thiamine (banana bag) before IV
glucose.
·
Kosakoff’s syndrome: memory
deficits, usually permanent
Brain Death
·
Review:
Wang MY N9/02
![]()
Neuroradiology
References
·
Osborn A., Diagnostic Neuroradiology,1994.
·
Osborn A. et al, Diagnostic Imaging: Brain, 2004.
·
Loevner LA, Case
Review: Brain Imaging.
·
Iodinated
Contrast Allergy: If minor,
can prep with prednisone 32mg PO 12hrs and 2hrs before; Benadryl 50mg either IM 1hr before, or IV 5min before. Use
non-ionic contast (Iohexol)
if possible. With a history of anaphylaxis do not give even with prep.
o IV Iodinated contrast and Glucophage
(metformin) can cause renal failure.
Angiography
·
Risk of
permanent major morbidity from
surveillance angiography is 0.04% (other series 0.3-2.3%) (Ringer
AJ N11/08) – Table 1 Literature Summary
Myelography
·
Only intrathecal contrast (nonionic water-soluble) agents: Iohexol (Omnipaque).
o Metrizamide and Pantopaque (iodinated
non-water soluble) have been supplanted by Iohexol - caused
seizures, etc.
o Pantopaque caused arachoiditis with
diffuse nodules (dense on CT)
·
Lumbar
puncture performed, dye injected. For cervical myelogram head of table lowered.
·
Plain films
usually combined with CT (CT-myelogram)
·
Spinal block patterns: “Feathering” =
extradural; meniscus = intradural, extramedullary
MRI
·
MRI
contraindications: www.MRIsafety.com, www.IMRSER.org. Partial list:
o Pacemakers, neurostimulators,
cochlear implants, recent vascular stent, coil, or filter, some aneurysm clips, some metallic implants
or fragments
o Pregnancy in 1st trimester. Gadolinium at
any time.
·
Diffusion-weighted:
ischemia shows up as high signal within minutes
·
Dynamic MRI
designed to detect dynamic stenosis or listhesis - Fonar Upright MRI
·
AANS
Course: BASICS OF MR & MR ANGIOGRAPHY
MR Angiography (MRA)
·
Phase-contrast
·
Time-of-flight
MR
Spectroscopy
·
Measures
metabolites in a 1cm2 voxel
o
Choline: indicative of cell membrane turnover
(eg tumors)
o
Lactate:
indicative of necrosis
o
NAA:
N-acetyl aspartate, found in neurons (normal brain)
·
Tumors
(generally nonspecific): ↑ Choline (& choline:creatinine ratio), ¯
NAA, ↑ lactate.
o
Cho:Cr ratio can predict survival & guide biopsy in gliomas.
o
Radiation necrosis: low Cho & Cho/Cr
o
Abscess: medium Cho/Cr
MR
tractography (Diffusion
Tensor Imaging)
·
Maps subcortical fiber
tracts (ie corticospinal
pathways) using diffusion tensor imaging.
·
Limited in areas of tumor or edema.
MR Neuroanatomy
·
MR landmarks
for precentral gyrus: on
most rostral axial cuts, look for L-shape. On midsagittal cuts it is just anterior to the termination of
the cingulated sulcus. On lateral sagittal cuts it is
bisected by a perpendicular line emanating from the posterior corner of the
insular triangle.


Functional
MRI (fMRI)
·
Detects
changes in deoxyhemoglobin.
·
Useful
for motor mapping, not sensitive enough for speech.
·
Motor
paradigms: 1) thumb-index opposition, 2) toe flexion, 3) tongue movement.
·
Speech
paradigms: 1) visualizing presented verbs, 2) decipher complex noun.
·
Protocols:
Hirsch J N9/00
·
May
be used after previous surgery (Peck
KK N4/09)
Positron
Emission Tomography (PET)
·
Measures metabolism. Radioisotopes
(emit positrons, eg 18F) conjugated to metabolically active
substance (eg glucose).
o
Requires cyclotron (for
radioisotopes). Positron = same mass of electron but + charge.
·
Radiotracers used:
o
18F flouro-deoxyglucose (FDG): measures glucose metabolism.
o
11C-methionine
(Met): Amino acid, measures protein
synthesis. Hot in low-grade tumors (unlike FDG). May be better for stereotactic
targeting (see JN9/04)
·
Resolution 8mm.
·
Findings:
o
Hot: GBM/ high
grade tumor, ictal seizure foci
o
Cold: Low grade
tumor, radiation necrosis, cortical dysplasia, interictal
seizure foci, mesial temporal sclerosis.
Single
Proton Emission Tomography (SPECT)
·
Measures blood flow.
·
201Tl
(thallium), 99Tc (technetium, HMPAO), or 133Xe used.
·
Resolution 10mm.
·
Findings similar to PET.
·
Thallium-SPECT
can distinguish tumor recurrence from radiation necrosis in metastases
(JN1/05S)
High-Intensity Focused Ultrasound
(HIFU)
·
Review:
see Jagannathan J N2/09 (History)
·
HIFU
Societies:
o
International
Society of Therapeutic Ultrasound (ISTUS)
o
Foundation for Focused Ultrasound
o
Focused
Ultrasound Surgery Foundation
![]()
·
Uses preoperative imaging (CT/MRI) registered to 3-D
space
·
Since
imaging is pre-operative, it does not account for intraoperative brain-shift,
which can be up to 1cm for tumor resections
·
Uses:
·
Preop/Intraoperative
planning: incision, craniotomy, approach
·
Extent
of resection for tumors
·
Stereotactic
Needle Biopsy
·
Lesioning
or placement of electrodes for functional neurosurgery
Frame-Based
Stereotaxy
·
Talraich or Schaltenbrand
atlases used
·
AC-PC
line: may be used to scale other measurements
·
Cosman-Roberts-Wells (CRW) Radionics
·
Leksell Elekta
·
Historical:
Brown-Roberts-Wells (BRW)
Frameless Stereotaxy
·
Use
LEDs or passive reflectors on instruments, tracked by mounted camera
·
Registration:
o
Skin
fiducials placed prior to imaging
o
“face
mask” with LEDs
o
Surface
matching
·
Frameless
Stereotactic Systems
o
BrainLab: VectorVision, Kolibri
o
Radionics/Integra: Omnisight
Stereotactic Needle
Biopsy
·
4%
morbidity, 1% mortality
·
Stereotactic
electrode placement: 0.5-2% risk of hemorrhage – higher with sulcal (10%) or ventricular (5%) penetration, hypertension (Elias WJ JN2/09)
![]()
Intraoperative MRI (IMRI)
·
Allows
for real time imaging
o
Real-time
biopsy
o
Confirmation
of extent of resection
o
Accounts
for brain-shift
·
Generally
require non-ferromagnetic instrumentation
·
Other
systems move into standard operative field
·
IMRI
Systems
o
General
Electric Signa SP: 0.5T “double-donut”. Operative
performed in MRI – no patient movement. Original IMRI design. Obsolete.
o
Medtronic
PoleStar (formerly Odin): Portable MRI
o
Brainlab BrainSuite: Rotating or movable table moves patient
into adjacent MRI
![]()
·
Given
as a single dose, conformal, stereotactic targeting, as opposed to conventional
radiotherapy
o
Standard
XRT kills rapidly dividing cells, spares normal tissue and hypoxic tissue
resistant. SRS kills tissue regardless of mitotic activity, oxygenation, or
inherent radiosensitivity.
o
Stereotactic Radiotherapy: Fractionated
radiosurgery.
o
“Staged-radiosurgery”: treating portions of large lesions 3-12 mos apart
o
Definition:
See Pollock
BE N12/04 and Adler
JR N12/04 for controversy
o
See
“Chained Lightning”: Hoh
Dj N7/07, 9/07
·
Systems:
o
LINAC: Linear accelerator accelerates electrons
into heavy metal (tungsten) which emits photons.
o
Advantages:
Frameless treatment, multiple-fractionation possible, can treat extracranial
lesions.
o
Systems:
§ CyberKnife (Accuray): uses
computer controlled robotics to move LINAC
·
See Neurosurgery 2/09S – abstracts from 2008 Cyberknife
Users’ Meeting
o
Gamma
Knife (Elekta): 201 Cobalt60 sources, emit photons.
o
Frame-based
treatment only. Multiple fractions difficult due to repeated frame placement.
o
Cannot
be used for extracranial lesions.
o
Recent
Models: 4,
4c,
Perfexion: robotized
·
Imaging: MR:
spoiled-GRASS sequence, 1-2mm slices, 512x256 matrix,
2 excitations. Fat suppression for previous TSRP with fat graft. MR appears to
be as accurate as CT (shift is minimal). Use short posts to avoid artifact.
o MRSpect data can be used for planning
·
Dose
toleration
o
Max.
dose to optic n.: Tishler
93: 8Gy. Leber 98: 10Gy had 0% optic neuropathy (had
better dosing).
o
Brainstem
15Gy max.
o
Spinal
Cord: 800Gy
·
Side-effects
o
Radiation-associated
neoplasms: 6 reported cases of, 6-19yr latency. Estimated risk 1:1000. Some
studies show no increase from baseline (RoweJ N1/07)
o
Deficits
may appear over 2yrs postop. Complications or tumor progression rarely occur
after 3yrs with benign lesions. (N03)
o Tumors may enlarge before contracting. Debateable
whether SRS makes subsequent surgery more difficult.
o Cavernous sinus 2% risk of CN4 or CN6 injury. (37%
of pre-treatment cranial nerve deficits improve).
·
Specific
Conditions
o Tumors
§ Brain Metastases
§ Gliomas
§ Pituitary Adenomas
§ Meningiomas
§ Acoustic neuromas
§ Cavernous sinus tumors: 98% local control. 37%
improved cranial nerve deficits, 2% new deficits.
§ Benign tumors (acoustics, meningiomas) may take over
5 years to begin regressing after treatment
o Trigeminal neuralgia
o AVMs
§ Cavernous malformations
o Also used for thalamic pain (hypophysectomy),
Proton Beam Therapy
·
Requires
cyclotron.
o
Current
PBT Centers: Loma Linda (CA), Indiana University, MD Anderson (TX), Hampton
University (VA), University of Florida, Massachusetts General Hospital,
Northern Illinois University
·
Uses
Bragg Peak Effect to maximize fall-off to surrounding tissues
·
The National Association for Proton
Therapy
Radiation Therapy
·
“4
Rs” of radiobiology to semiselectively target
dividing cells: reoxygenation, reassortment,
repopulation, repair of normal tissue (favors fractionation)
·
Intensity-modulated
radiotherapy (IMRT) is as a way of delivering highly conformal radiation to
tumors
·
Miniature
linear accelerators have mounted on a robotic arm (CyberKnife)
or mounted in a ring gantry (TomoTherapy)
·
Multileaf collimators
(MLC) replaces the custom-fabricated collimators. It consists up to 60 pairs
of opposing tungsten fingers, or leaves. The position of each leaf can be adjusted
to shape the beam. Depending on the manufacturer, the width of each leaf varies
from 1 cm to 3 mm. MLC has enabled intensity-modulated radiation therapy
(IMRT).
·
The
MLC can be used to vary the integrated intensity of the photon beam as a
function of position within the aperture. This can be achieved using either of
two techniques: stop and shoot or dynamic mode.
o
Using
stop and shoot, the beam is divided into eight or more segments, each of which
is delivered using a different MLC aperture. When the segments are delivered,
the superposition of the beams results in a field that can have eight or more
intensity levels, the highest intensity occurring at points where all segment
apertures overlap.
o
The
dynamic technique involves moving the MLC leaves across the field while the
beam is being delivered. In effect, a slit opens on one side of the field,
moves across the field, and finally closes on the other side. As it crosses the
field, its shape and width change. This modulates the beam intensity because at
any point, the intensity is a function of what fraction of the time the point
was under the gap.
·
IMRT
can be used in conjunction with a software tool known as inverse treatment
planning in which you start with the final dose distribution and working backward
toward the intensities for each beam.
·
The
patient must remain stationary in the correct position throughout dose
delivery. The techniques used can be grouped into two approaches:
o
In
the first, the patient is immobilized in a stereotactic body frame or
immobilization cradle. Such devices are noninvasive and, thus, do not guarantee
that the patient will remain perfectly positioned.
o
A
second approach is used when localization images can be taken frequently during
the treatment without greatly lengthening the procedure. It is especially
suited to procedures in which dual in-room kilovolt units are available. The
patient can be set up conventionally on the treatment machine couch without
additional immobilization. The positions of the bony structures are checked
many times during treatment
·
Cognitive effects
o
Memantine,
a NMDA receptor antagonist used to treat Alzheimer’s disease, is being studied
in the prevention of cognitive effects of WBRT – RTOG 0614
·
Yamada Y N8/07
·
See
“Chained Lightning”: Hoh Dj N7-9/07
![]()
·
Endoscope
may be passed thru ventricular catheter to confirm placement
![]()
Awake craniotomy
·
Anesthesia
o
Some do not intubate, use IV propofol during opening and closing, with versed or fentanyl while awake. In this case do not open dura until
the patient is fully awake, to prevent swelling
o
Local anesthesia (lidocaine+marcaine)
is used on incision. Additional local anesthetic is
infused around the supraorbital rim, the zygoma, the posterior auricular region, and the temporalis insertion to produce a field block. Pin sites are
injected if a headholder is used. The dura is also
injected.
o
Asleep-awake-asleep technique:
Intubation/General anesthesia > opening with hyperventilation > extubation > mapping > intubation (fiberoptic laryngoscope or tube changer) > general
anesthesia
o
Inhalational (isofluane,
nitrous oxide) and remifentanyl after verifying
muscle relaxants are worn off by train of four.
o
Berger feels propofol
may adversely affect cortical depolarization.
·
Some use head-pins, others use
doughnut.
Cortical Mapping
·
Slow-growing
lesions may shift eloquent areas, even contralateral
·
Stopping
resection 1-2cm from eloquent cortex greatly reduces postop deficits
·
See Tharin S N4/07
Cortical
stimulation
·
Done
with bipolar stimulator
(60Hz, 1msec, single-phase, 2-6mA awake, 4-16mA general anesthesia). Increase
current by 2mA until response is obtained. Hold tips on cortex for 2-3 secs.
·
Patient
temperature >36º.
·
EMG
recording may improve sensitivity.
·
May
be done asleep or awake.
·
Always
have cold irrigation ready to irrigate cortex in the event of a
stimulation-induced seizure. Seizures stopped by cold irrigation of cortex, bezodiazapines, and Dilantin
·
Some
vary current at different sites (while monitoring afterdischarges),
others don’t (JN9/04)
·
Afterdischarges monitored by electrocorticography – i.e. 5-grid strip laid
next to stimulated area. This prevents seizures and ensures that stimulation
effects are local only (ie specific)
·
Negative
results may not ensure safe resection; a positive result (ie
speech arrest) is necessary to be sure of the location of essential language
sites
·
May
be done at bedside with implanted electrode grids.
Language Mapping
·
Hemispheric
dominance: Left hemisphere for 99% of right-handers. Overall: 85% left, 9%
bilateral, 6% right.
·
In
left-handers use WADA test to determine language dominance.
·
Obtain
baseline language function. Test the patient preoperatively and eliminate
objects the patient can’t identify. Naming errors must be less than 25%. If
patient is unable to participate preoperatively a trial of higher-dose steroids
can be attempted to see if enough improvement occurs than language testing can
be used.
·
Awake
craniotomy with cortical stimulation
·
Object naming is the most reliable
test.
·
Each
site is tested 3 times, never twice in succession
·
Essential language sites exist
primarily on the surface of the gyri and not in the
depths. Primary language sites are vertically organized with respect to subcortical fibers, and surface stimulation can be used to
predict the results subcortical resection. But subcortical mapping can be used
to identify language fibers near the insula
·
Subcortical language mapping has
been performed (Duffau H JN9/08)
Motor Mapping
·
Resection may be continued into the
anterior bank of the precentral gyrus
without causing an adverse event
·
Resection may be performed in both
the dominant and nondominant supplementary motor
areas without causing permanent sequelae, as long as
the primary motor cortex is not violated
·
Primary somatosensory
cortex resection will produce a temporary hypesthesia
and proprioceptive deficit. When they affect the
dominant hand, such deficits are problematic to the patient and the patient
should be counseled preoperatively regarding this
·
Cortical stimulation: Motor area identified in 94%.
·
Reversal of SSEPs with cortical strip
placed over central sulcus used to identify central sulcus and motor and sensory cortex

![]()
·
Used in
spine surgery, or cranial surgery near motor pathways or vascular (aneurysms)
·
Used during
positioning (e.g. spinal stenosis) as well as during procedure
·
Done
by CNIM (certified neurophysiologic intraoperative monitoring tech – EEG tech with
national certification), audiologist, neurophysiologist, or MD (e.g.
neurologist)
·
Avoid
inhalation agents, BZDs, barbs; use nitrous or narcotics, short-acting muscle
relaxants (not for MEPs)
·
Evoked potentials: neural pathways’ integrity assessed
by stimulating at one end and recording at another
·
Amplitude and latency of transmission is recorded and
compared to baseline
·
Baseline data best obtained after exposure (normalizes
anesthesia, temp, vitals, etc.)
·
Amplitude
↓50% or latency ↑ 10% is significant (others
say 80% drop or “all-or-none” significance)
·
Loss of EPs:
·
Check wound – compression, retractors, etc. Irrigate
with warm saline (r/o cold irrigation).
·
Check with technician for system integrity
·
Check with anesthesia (type used), vitals (temp, BP, O2,
etc)
·
Raise BP
·
Can wake up patient and test function (Stagnara wake-up test) or ankle clonus
test (clonus normally present in anesthetized
patients – absence indicates damage)
·
Reviews: Quinones-Hinojosa A NCNA04
·
EMG used to monitor nerve root
function
·
During pedicle screw placement, screw
electrically stimulated – EMG reaction suggests pecidle
fracture/ violation by the screw
·
Burst EMG: mechanical irritation.
Train EMG: nerve root injury
·
Spinal cord monitoring : MEPs and
SSEPs
·
Motor Evoked Potentials (MEPs)
1.
Muscles (CMAP): detected by EMG
·
CMAPs: switch to muliphasic
waveform or loss in multiple muscles worrisome (Matsuyama
Y JN:S5/09)
2.
Peripheral mixed nerve (NMEP or CNAP):
measured by electrodes over nerves
·
Epidural electrode recording distal to
intramedullary resection site (“D waves”) may also be
used
·
Somatosensory Evoked Potentials (SSEPs)
·
Square wave,
300μsec, 25-30mA max, 5.3Hz.
·
Brainstem
auditory evoked responses (BAERS):
·
Used in preop evaluation of epilepsy
·
Used for pre-surgical mapping of visual, auditory, somatosensory, and motor cortex functional areas.
·
MEG
Systems: Elekta Neuromag
![]()
Neuroendovascular Procedures and
Devices
·
Embolization:
Coils, Liquid embolic agents
o
Guglielmi Detachable Coil
(GDC): Platinum microcoils. Used since the early
1990s. For aneurysms, supplanted balloons, pushable
coils, and liquid embolic agents. (Boston
Scientific)
o
Matrix
Detachable Coils (Boston Scientific): coated with bioactive polymer (polyglycolic/polylactic acid)
o
Micrus
ACT Microcoil
o
Hydrogel-coated coils: MicroVention HydroCoil Embolic System
o
Ev3: AXIUM, Nexus, NXT
o TruFill (Cordis
)o
Onyx: ethylene vinyl copolymer (ev3)
o
NBCA: n-Butyl Cyanoacrylate, ex. TruFill (Cordis)
·
Embolic/Ischemic complications
o
Due to vessel wall injury and thrombosis on
catheters, coils, etc.
·
Intracranial Stents:
used for arterial stenosis
o
Balloon-mounted coronary stents
§ Neuroform Stent: used for stent-assisted coiling of aneurysms
(Boston Scientific)
§ Wingspan
Stent: used for intracranial arterial stenosis (Boston Scientific)
§ Enterprise
Stent (Cordis/Johnson &
Johnson) (Mocco J JN1/09)
§ Leo & Leo
Plus (Balt Extrusion)
·
Most stents have 6-9% metal surface coverage, except
PED which has 30-35%
o
MERCI Retrieval System (Concentric Medical)
o
AngioJet rheolytic mechanical thrombolytic device (Possis Medical)
o Alligator
Retrieval Device (Chestnut Medical Technologies)
·
Review: Neurosurgery 11/06S: Endocascular
Neurosurgery
·
Audio: The
Evolution and Future Direction of Endovascular Technologies – Rossenwasser RH
Please send comments and corrections
to admin@flotte2.com
Disclaimer: This outline is complied, not
original. Sources are being added
retrospectively.