craniotomy & neuromonitoring

7/28/2019 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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craniotomy & neuromonitoring

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