CCNT flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Upper motor neuron signs

Spasticity, hyperreflexia, Babinski sign, and loss of fine motor control occur with lesions of the corticospinal tract above the anterior horn cell.

Lower motor neuron signs

Flaccidity, atrophy, fasciculations, and areflexia result from lesions of the anterior horn cell, nerve root, or peripheral nerve.

Cerebellar lesion signs

Ipsilateral ataxia, dysmetria, intention tremor, and dysdiadochokinesia occur because cerebellar outputs decussate after leaving the cerebellum.

Basal ganglia direct pathway

The direct pathway facilitates movement by inhibiting the globus pallidus interna, disinhibiting the thalamus and increasing cortical motor activity.

Common-mode rejection ratio

CMRR = 20 log10(differential gain / common-mode gain); higher values indicate better rejection of noise common to both inputs, ideally above 100 dB.

Nyquist sampling theorem

The sampling rate must be at least twice the highest frequency of interest; for EEG up to 70 Hz, use a sampling rate of at least 140 Hz.

Patient leakage current limits

Under IEC 60601-1, patient leakage current must be below 100 µA in normal condition and below 500 µA in single-fault condition for type BF/CF applied parts.

Electrode impedance target

EEG electrode impedance should be less than 5 kΩ and balanced across inputs; high or unequal impedance degrades common-mode rejection and increases artifact.

10–20 system electrode placement

Electrodes are placed at 10% or 20% of the nasion–inion and preauricular distances; odd numbers are left, even numbers right, and z indicates midline.

Longitudinal bipolar montage

Also called double banana, it chains Fp1-F3-C3-P3-O1, Fp2-F4-C4-P4-O2, Fp1-F7-T3-T5-O1, and Fp2-F8-T4-T6-O2 to display anteroposterior voltage gradients.

Polarity convention in EEG

When input 1 is more negative than input 2, the deflection is upward; when input 1 is more positive, the deflection is downward.

Photic stimulation protocol

Flashes at 1–30 Hz are delivered for up to 10 seconds per frequency to assess photoparoxysmal response and occipital driving.

Normal awake alpha rhythm

A posterior dominant rhythm of 8–13 Hz, reactive to eye opening, seen in relaxed wakefulness with eyes closed over occipital regions.

Sleep spindle

A burst of 12–14 Hz activity lasting at least 0.5 seconds, maximal centrally, marking stage N2 sleep.

3 Hz spike-and-wave

Generalized 3 Hz spike-and-wave discharges are the classic EEG signature of absence epilepsy and are often provoked by hyperventilation.

Triphasic waves

Generalized periodic waves with three phases, often frontally predominant, seen in metabolic encephalopathy such as hepatic failure.

Electrocerebral inactivity

No cerebral activity greater than 2 µV during a 30-minute recording at increased sensitivity, used as an adjunct in brain death determination.

Visual evoked potential P100

The P100 wave is a positive occipital response at about 100 ms after pattern-reversal stimulation; prolonged latency suggests optic nerve demyelination.

BAEP wave V

Wave V of the brainstem auditory evoked potential arises near the inferior colliculus and is the most robust wave for identifying brainstem dysfunction.

SSEP median nerve N20

The N20 wave is the first cortical response after median nerve stimulation, recorded over the contralateral somatosensory cortex; prolonged latency indicates central conduction delay.

Evoked potential averaging

Repeated stimuli are averaged to improve signal-to-noise ratio; hundreds to thousands of trials are typically required to extract small evoked responses.

Motor conduction velocity formula

Conduction velocity (m/s) equals the distance between stimulation sites (mm) divided by the latency difference (ms).

Demyelinating conduction findings

Prolonged distal latency, slowed conduction velocity, and preserved CMAP amplitude suggest demyelination rather than axonal loss.

Axonal loss findings

Reduced CMAP or SNAP amplitude with relatively normal conduction velocity and distal latency indicates axonal degeneration.

Fibrillation potentials

Spontaneous brief spikes on EMG indicating active denervation of muscle fibers, appearing weeks after nerve injury.

H-reflex

A late response recorded from the soleus after tibial nerve stimulation, assessing the S1 root and afferent pathways; prolonged latency suggests S1 radiculopathy.

Hand hygiene

The single most effective infection control measure; use alcohol-based hand rub or soap and water before and after every patient contact.

Needlestick injury protocol

Wash the wound with soap and water, report immediately, and initiate post-exposure prophylaxis evaluation; HIV prophylaxis should begin as soon as possible.

Seizure during EEG

Note the time and semiology, protect the patient from injury, do not restrain, and ensure suction and oxygen are available.

Informed consent

Obtain and document patient understanding before invasive or non-routine procedures, including risks, benefits, and alternatives.

HIPAA confidentiality

Protected health information may be disclosed only on a need-to-know basis; secure records and avoid discussing patients in public areas.

Documentation correction

Errors in records must be corrected with a dated, signed explanation while keeping the original entry visible; never obliterate or alter the original.