Transcript MONITORING OPERATIONS IN THE SKULL BASE

MONITORING OPERATIONS
IN THE SKULL BASE
CHAPTER VI
Monitoring of cranial nerves
in skull base operations:
what to monitor?
1. Extraocular muscles
2. Facial muscles
3. Masseter muscle
4. Tongue
5. CNIX pharynx
6. CNX larynx
7. ABR
8. CAP from CNVIII and cochlear nucleus
Monitoring other cranial motor
nerves
Extraocular muscles
• CN III
• CN IV
• CN VI
Lower cranial nerves
• CN IX
• CN X
• CN XI
• CN XII
Monitoring other cranial motor
nerves
• Monitoring the facial nerve is a model
for monitoring other cranial motor
nerves
How to activate the motor
system?
•
•
•
•
Electrical stimulation of motor nerves
Magnetic stimulation of motor nerves
Electrical stimulation of the motor cortex
Magnetic stimulation of the motor cortex
How to record the response?
• Recording of electromyographic (EMG)
potentials
• Mechanical recordings of muscle
contractions
• Recording of motor nerve CAP
Recording of EMG potentials
Recording muscle responses
• Muscle relaxants cannot be used
MONITORING OTHER
CRANIAL MOTOR NERVES
EXTRAOCULAR MUSCLES
• CN III
• CNVI
• CNIV
LOWER CRANIAL NERVES
• CNIX
• CNX
• CNXI
• CNXII
Monitoring nerves that
innervate extraocular muscles
CN III, CN IV, CN VI
Recording EMG potentials
from extraocular muscles
• Using needle electrodes
Recording from
extraocular
muscles:
Place needle
electrodes
percutaneously
so they come
close to
respective
muscles
Medial rectus for
CNIII
Lateral rectus for
CNVI
Superior oblique
for CNIV
EMG potentials
recorded from
extraocular muscles
in response to
electrical stimulation
of respective cranial
nerves intracranially
Recording EMG potentials
from extraocular muscles
• Using non-invasive electrodes
Electrical stimulation of the oculomotor
nerve (CN III)
Middle rectus
Lateral rectus
Masseter
Monitoring multiple systems
simultaneously
•
•
•
•
•
•
•
Extraocular muscles
Facial muscles
Masseter muscle
Tongue
Neck muscles
BAEP
VEP
Typical placements of
recording electrodes
used in skull base
operations
Recording from
extraocular muscles:
Place needle
electrodes
percutaneously so they
come close to
respective muscles
Medial rectus for CNIII
Lateral rectus for CNVI
Superior oblique for
CNIV
Monitoring other cranial motor
nerves
Lower cranial motor nerves
CN IX, CN X, CN XI, CN XII
FROM YINGLING
Monitoring CN X can be done
by placing recording
electrodes in the vocal folds
Monitoring
CNX
FROM YINGLING
FROM YINGLING
Auditory neuromonitoring
Recording of auditory evoked
potentials in operations in the
posterior fossa
Monitoring of ABR can detect
manipulations of the
brainstem before
cardiovascular signs change
Waveform analysis of the ABR
provides information about the
anatomical location of an
injury
Different
conventions for
display of BAEP
NEURAL GENERATORS
OF THE ABR:
• Peak I: distal auditory
nerve
• Peak II: central auditory
nerve
• Peak III: mainly cochlear
nucleus
• Peak IV: unknown
• Peak V: termination of
the lateral lemniscus in the
contralateral inferior
colliculus
Ipsilateral
stimulation
Waveform
analysis of the
BAEP
provides
information
about the
anatomical
location of an
injury
PEAK V
PEAK III
Contralateral
stimulation
Waveform
analysis of the
BAEP provides
information
about the
anatomical
location of an
injury
PEAK V
PEAK III