craniotomy & neuromonitoring
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NEUROLOGICAL
SURGERY & MONITORINGCraniotomies
Marisa Goddard MS CNIM
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Neurological Surgeries
Craniotomies are among the mostdelicate and intricate surgery type
Procedures can be as straight forward asMicrovascular Decompressions (MVDs)
to as complicated as Posterior FossaTumor Resection (Acoustic Neuromas)
Knowledge of anatomy and criticalstructures is imperative in Crani cases
Often times surgeons may be trying anew approach or have a challenging timeplanning the surgery and monitoring isleft to the Physiologist to determine
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Microvascular Decompression
Procedure that relieves
pressure on a nerve caused by
a surrounding blood vessel
Most commonly used to treatTrigeminal Neuralgia
Monitoring is usually focused on
the Motor Cranial Nerve that is
being irritated or may be in the
path of exposure
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Tumors - General
Posterior Fossa
Middle Fossa
Anterior Fossa
Skull Base
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Posterior Fossa Tumors
(Acoustic Neuroma) Characterized by a tumor on the
VIIIth Cranial Nerve
Monitoring BAERs (ABRs) is
critical in such cases as well as
CN V and VII due to proximity to
the VIIIth nerve
Pre Operative hearing tests
should be performed and in
chart prior to case to determinepre operative loss and to explain
baseline deficits
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Middle Fossa Tumors Tumors located in Parietal lobe as
well as Temporal lobes
Monitoring EEG as well as SSEPs
can help minimize the damage that
usually takes place during
exploration of the tumor
Based on location of the tumor major
vessels that surround the area
should be noted so that proper focus
can be placed on SSEP responses(MCA- Upper SSEPs vs ACA- Lower
SSEPs)
BAERs may be requested based on
location and size of tumor and pt
symptoms
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Anterior Fossa Tumors
Tumors located in Frontal lobe as
well as pituitary surgeries
SSEPs are critical in such cases
especially where pituitary tumors
are being resected
Upper and Lower SSEPs are of
interest depending on location and
affected blood vessels (sometimes
VEPs)
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Skull Base Procedures
Usually involves tumors on
brainstem
Here is where the nuclei of
cranial nerves lie as well as the
point of decussation of many
evoked potentials
BAERs, SSEPs and Motor
Cranial Nerve stimulation and
EMG is usually monitored withdirection of surgery and critical
structures
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Cerebrovascular Procedures
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Aneurysm Clipping and AVMs
In these surgeries even thoughstraight forward, the conditionand structure of the aneurysmcan prove fatal if not clampedin time
Monitoring EEG as well asSSEPs (Upper and Lower) ismost reliable in detecting anyischemic events prior to, duringand post clamp
Arteriovascular malformationsare deformities of bloodvessels in the brain (AVMs)
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Important Points
Most important information to learn
prior to the surgery is:
Location of aneurysm (or
malformation)
Has the anuerysm bled (this is
usually noted by pt having a
drain in the skull and being
ventilated)
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Cerebrovascular Keys
EEG is a primary modality
used not only for monitoring
during surgery but to also
determine burst suppression
for neuroprotection duringcritical stages of the case
Post clamping should not
show any deficits in SSEPs
or EEG to ensure properbrain perfusion
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Cortical Mapping
In many surgeries the
localization of the central
sulcus is imperative (Epilepsy
surgery vs Tumor Cases)
This is achieved with a cortical
grid and SSEP stimulation ( at
time direct cortical stimulation
is performed)
Phase reversal denoteslocation of central sulcus
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Motor Mapping
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Summary
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