CNIM Comprehensive Study Guide: Neuroanatomy, Evoked Potentials, and Intraoperative Monitoring

Comprehensive vocabulary flashcards covering neuroanatomy, intraoperative neurophysiological monitoring (IONM) modalities (SSEP, MEP, BAER, EEG, EMG), anesthesia, instrumentation, and clinical safety standards based on the CNIM Study Guide.

Neuron

An effector cell (gray matter) that causes a postsynaptic response in a muscle, gland, or organ cell following a stimulus at the terminal end of the presynaptic neuron.

Duration (pulse width) range for MN SSEP?

100 - 300 us

What opposes any change in current ?

Inductance

Largest cortical SSEP following L PTN is found between _____ & ______

Cpz & Cp3

When trying to ISOLATE brainstem potential UN SSEP a good location for non cephalic quiet reference electrode is

EPcontra

SSEP clinical bandpass?

30 - 3000 HZ

For a jugular bulb tumor what cranial nerves are monitored ?

Lower cranial nerves VII (7) to XII (12)

Brown Sequard Syndrome

Pain/temp (contra) & motor loss (ipsi)

Hypocarbia

Low CO2 in blood

What are MRI conditional electrodes made out of ?

Nickel titanium

Impedance is opposition to

Alternating flow

Bandpass for MN phase reversal ?

1 - 30HZ to 250 - 1500HZ

Vascular compromise of the PCA (posterior cerebral artery) will most likely have what effect on the MN SSEP?

Loss of P14/N18

Posterior Cerebral arteries profuse the ____ & _____

Brainstem & cerebellum

Member of circle of Willis (4)

1. MCA

2. ACÁ

3. anterior communicating artery

4. Posterior communicating artery

Main distributor of blood to the brain

• 2 vertebral arteries

forming

• basilar artery

• ICAs

4 Lobes of Brain & their functions:

1. Frontal: thinking, decision making, behavioral control

(Houses motor cortex-precentral gyrus)

(Houses Broca’s area)

2. Parietal: association

(Houses sensory cortex-post central gyrus)

3. Occipital: visual center

4. Temporal: language, auditory cortex

(Houses wernicke’s area)

Great radicular artery is also known as ______ which is in _____ of spine levels _____

Great radicular artery, artery of adamkiewicz, anterior thoracic spine, levels T11-T12

ICA supplies the ____ & ___ with blood. _____% of profusion

ICA supplies the MCA & ACÁ with blood. 85% of profusion

What kind of flow from Pos & Ant communicating arteries ?

contralateral flow

Basilar/vertebral arteries supply……

PCA

MCA supplies _____ cortex

Lateral cortex (UE SSEP)

ACA supplies _____ cortex

Medial cortex (LE SSEP)

Ex of bipolar montage

Cpi- Fpz

Ex of Referential montage

Cpi - Epc

Cpi - hand

Bipolar Recording Montage

Cpi - Fpz

Excitatory postsynaptic potential

Temporary depolarization of cell caused by the flow of (+) ions into the cell

Bandpass for short latency SSEP

30-3000HZ

Disadvantages of D wave monitoring ?

1. Can’t assess laterality

2. Epidural recording require additional laminectomy below surgical site (extended exposure)

3. Can’t assess function below clonus

UNAFFECTED BY NMJ BC OVER DURA

Bilateral slowing of EEG during R CEA cross clamping. What’s the cause of the slowing ?

R cerebral ischemia

How do you convert seconds (s) to milliseconds (ms)?

Multiply by 1000

SSEP bandpass

30-1000HZ

Minimum bandpass filter for EP system ?

0.1-5000HZ

BAEP Bandpass

LFF: 100-150 HZ

HFF: 2500-3000HZ

Charcot Marie Tooth Disorder may affect following modalities

SSEP & TcMEP

Chiari Malformation Modalities

SSEP, MEP, BAER

Pulse width for SSEP

100microseconds

Best Derivation to isolate MN cortical response ?

Cpc- Cpi

DTAB

D: 0-4 HZ (deep sleep)

T: 4-7 HZ (drowsy/ dreaming)

A: 8-13 HZ (alert & relaxed)

B: >13 HZ (concentration)

If you run a MEP with the anode at C4 & cathode at C3…… What response is larger L AH or R AH?

L AH is larger

• anode @C4 (R)

• contralateral muscles of anode will have larger response, so in this case L response is bigger bc anode is C4 on (R)

Left side cranial nerve palsies & right side extremity palsies has a lesion where ?

Fan (dorsiflex) / upper motor lesion

• OSHA stands for:

• Covers what safety standards ?

• occupational safety & health administration

• smoke fume safety & bloodborne pathogens

Issue with notch filter ?

Ringing artifact

A lesion of the brainstem will result in ____ motor dysfunction of the extremities but ____ cranial nerve dysfunction

a lesion of the brainstem will result in CONTRA motor dysfunction of the extremities but IPSI cranial nerve dysfunction

A drop from 12 HZ to 6 HZ in 4 EEG channels may indicate ?

Ischemic stroke

Receptive Aphasia results from damage to ____ which is located in the ______

Wernicke’s Area located in the posterior superior temporal gyrus

Broca’s vs Wernicke’s

Broca’s: motor, frontal lobe (slow broken speech)

Wernicke’s: sensory, temporal lobe (normal/excessive speech)

SSEP Anode/Cathode:

Anode (+) and cathode (-)

• anode distal

•cathode proximal

Selective dorsal rhizotomy may be performed on a patient with a diagnosis of ____ by severing _____.

Diagnosis of cerebral palsy by severing posterior rootlets

Vestibulocochlear nerve appears where in the brain?

In the groove between the pons & medulla

EcochG records potentials from what two things ?

1. Cochlea

2. Distal auditory nerve appears where

   *look @ stuff recorded before and up to wave I in Ecog

• transaction of proximal portion of auditory nerve has no EFFECT in Ecog

Subdural electrodes are made of ?

Platinum

Decrease in alpha (8-13HZ) & beta (>13HZ) may indicate:

Cortical ischemia & cerebral infarct

20dB:

40 dB:

60 dB:

80 dB

20dB: increase press 10x

40 dB: increase 100x

60 dB: increase 1,000x

80 dB: increase 10,000x

Apraxia vs ataxia

Apraxia: motor disorder, difficulty performing tasks- talking/moving

Ataxia: loss of coordination/balance- tremors, slurred speech, poor balance, fine motor difficulty (can be motor or sensory)

Derivation for ISOLATING MN cortical response?

CPc - CPi

Dendrites

Neuronal projections that collect electrical signals (IPSPs and EPSPs) and propagate potentials toward the soma.

Soma

The cell body of a neuron that houses the nucleus; it integrates incoming signals and generates outgoing electrical signals to the axon.

Axon

A neuronal extension that conducts electrical impulses away from the soma to the dendrites of another cell or to an effector cell ($1\text{--}1000\,\text{mm}$ in length, $1\text{--}25\,\mu\text{m}$ in diameter, with thicker diameters conducting faster).

Nodes of Ranvier

Gaps along the axon where the membrane is uninsulated by myelin, enabling rapid saltatory ("jumping") propagation of action potentials.

Action Potential

An all-or-none electrical impulse generated when resting potential ($-70\,\text{mV}$) reaches threshold ($-55\,\text{mV}$), characterized by rapid depolarization ($\text{Na}^+$ influx up to $+30\,\text{mV}$), repolarization ($\text{K}^+$ efflux), and transient hyperpolarization (refractory period).

Sodium-Potassium Pump ($\text{Na}^+/\text{K}^+$ Pump)

An active transport pump that restores and maintains the cell resting membrane potential at $-70\,\text{mV}$ by pumping $3\,\text{Na}^+$ ions out and $2\,\text{K}^+$ ions in.

Glutamate

An endogenous excitatory neurotransmitter that causes EPSPs and acts on NMDA receptors.

GABA

An endogenous inhibitory neurotransmitter in the central nervous system that produces IPSPs.

Acetylcholine (ACh)

A neurotransmitter that exerts inhibitory effects on cardiac muscle and excitatory effects on skeletal muscle.

Dorsal Column Pathway

An afferent sensory pathway situated in the posterior $1/3$ of the spinal cord that mediates discriminative touch, conscious proprioception, and vibration.

Corticospinal Tracts

Descending motor pathways mediating conscious voluntary movement; $90\%$ of fibers decussate in the medullary pyramids (lateral tracts) and $10\%$ decussate in the spinal cord (anterior tracts) to synapse on alpha motor neurons in the ventral horn.

Spinothalamic Tract

An ascending sensory pathway responsible for transmitting pain, temperature, and crude touch sensations.

Cerebral Cortex

A thin layer of gray matter covering the outer portion of the cerebrum, folded into gyri (bulges) and sulci (deep furrows/fissures) to increase surface area for cell communication.

Circle of Willis

An arterial circle distributing blood to the brain, supplied by the two vertebral arteries (uniting into the basilar artery) and the internal carotid arteries, formed by the MCA, ACA, anterior communicating artery, and posterior communicating artery.

Artery of Adamkiewicz

The great radicular artery situated in the anterior thoracic spine at $\text{T11--T12}$ that supplies blood to the anterior lower two-thirds of the spinal cord.

Sylvian Fissure

The lateral sulcus/fissure that demarcates the temporal lobe from the overlying frontal and parietal lobes.

Vertebral Column

The spinal skeletal column consisting of $7$ cervical vertebrae (lordosis), $12$ thoracic vertebrae (kyphosis), $5$ lumbar vertebrae (lordosis), $5$ fused sacral vertebrae (kyphosis), and $4$ fused coccygeal vertebrae.

Ligamentum Flavum

A spinal ligament that connects the adjacent laminae of the vertebrae.

Conus Medullaris

The tapered lower terminus of the spinal cord, normally situated between the $\text{T12}$ and $\text{L2}$ vertebral levels.

Trigeminal Nerve (CN V)

A mixed cranial nerve responsible for facial sensation and mastication, exiting via the superior orbital fissure ($\text{V}_1$), foramen rotundum ($\text{V}_2$), and foramen ovale ($\text{V}_3$).

Facial Nerve (CN VII)

A mixed cranial nerve controlling facial expression and taste from the anterior $2/3$ of the tongue, exiting the skull through the internal auditory meatus with five branches: temporal, zygomatic, buccal, mandibular, and cervical.

Minimum Alveolar Concentration (MAC)

The minimum alveolar concentration of an inhalational anesthetic required to prevent motor response to a noxious stimulus in $50\%$ of patients.

Potentiation Effect

The exponential depressant effect exerted on evoked potentials when volatile halogenated anesthetics are co-administered with nitrous oxide ($\text{N}_2\text{O}$).

Train of Four (TOF)

A peripheral nerve stimulation pattern used to quantify neuromuscular blockade ($0/4 = 100\%$ blocked, $1/4 = 90\%$ blocked, $2/4 = 80\%$ blocked, $3/4 = 75\%$ blocked, $4/4 < 75\%$ blocked).

International 10-20 System

An internationally recognized system of EEG electrode placement using relative proportional measurements ($10\%$ and $20\%$ intervals) between cranial landmarks (nasion, inion, and preauricular points).

Electro-cerebral Inactivity / Silence (ECI)

An electroencephalographic confirmation of brain death defined by the absence of non-artifact electrical activity exceeding $2\,\mu\text{V}$ when recorded with inter-electrode distances $> 10\,\text{cm}$ for at least $30\,\text{minutes}$.

WADA Test (ISAP)

Intracarotid Sodium Amobarbital Procedure that determines hemispheric language and memory dominance by injecting sodium amobarbital via catheter into the carotid or femoral artery to temporarily inactivate one cerebral hemisphere.

Spectral Edge Frequency (SEF)

A quantitative EEG parameter (typically set at $90\text{--}97\%$) describing the frequency boundary below which that percentage of total signal power resides.

Carotid Endarterectomy (CEA) ALERT Criteria

Intraoperative warning criteria defined by a $\ge 50\%$ decrease in fast activity, a $\ge 50\%$ increase in slow delta activity, or a $10\%$ latency shift in median nerve SSEPs following cross-clamping.

Electrocorticography (ECoG)

Direct recording of electrical activity from the exposed cerebral cortex to delineate epileptogenic zones, guide resections, and monitor for stimulation-evoked after-discharges.

Spontaneous EMG (spEMG)

Continuous, real-time, free-running recording of muscle electrical activity to detect mechanical irritation, stretching, or thermal injury to motor nerves.

Transcranial Motor Evoked Potentials (MEPs)

Compound motor action potentials recorded from distal skeletal muscles following multipulse electrical train stimulation applied over the motor strip to monitor the integrity of the lateral and anterior corticospinal tracts.

Anodal Stimulation

Cortical stimulation using the anode as the depolarizing electrode, capitalizing on the orientation of pyramidal apical dendrites toward the brain surface to depolarize at the soma and bypass the axon hillock.

D Waves and I Waves

Descending corticospinal potentials recorded directly from the spinal cord; D waves reflect direct pyramidal axon activation, whereas I waves reflect indirect excitation through cortical interneurons and are abolished by anesthesia.

Somatosensory Evoked Potentials (SSEPs)

Averaged electrical recordings of ascending afferent signals generated along peripheral nerves, the dorsal column-medial lemniscal system, and the primary somatosensory cortex following peripheral nerve stimulation.

Near-Field vs. Far-Field Potentials

Near-field potentials are generated by neural structures situated directly beneath the recording electrode (e.g., Erb's point, cortical peaks); far-field potentials are generated by distant subcortical generators conducted through volume-conducting tissue (e.g., subcortical brainstem peaks).

Upper Extremity SSEP Obligate Peaks

Median nerve SSEP peaks consisting of $N9$ (brachial plexus at Erb's point), $N13$ (cervical spinal cord), $P14$ (caudal medulla/medial lemniscus), $N18$ (upper brainstem/thalamus), and $N20/P23$ (primary somatosensory cortex).

Lower Extremity SSEP Obligate Peaks

Posterior tibial nerve SSEP peaks consisting of $N9$ (popliteal fossa), lumbar potential $LP/N22$ (lumbar cord), $P31$ (caudal medial lemniscus), $N34$ (upper brainstem/thalamus), and $P37/N45$ (medial somatosensory cortex).