ABPN Clinical Neurophysiology cheat sheet

Alpha rhythm: 8-13 Hz posterior dominant rhythm, attenuates with eye opening; reactive alpha is the key marker of normal wakefulness.

N1 sleep: low-amplitude mixed-frequency EEG, vertex sharp waves, slow eye movements; N2 requires sleep spindles (11-16 Hz) or K-complexes.

N3 sleep: delta waves 0.5-2 Hz with peak-to-peak amplitude >75 uV occupying >20% of the epoch.

Temporal lobe spikes are best seen with a tangential montage (e.g., F7-T3, T3-T5, F8-T4, T4-T6) and may be missed on referential montages.

Benign epileptiform transients of sleep (BETS): small sharp spikes in N1/N2, broad field, no focal slowing; do not treat as epileptiform.

Triphasic waves: 1.5-2.5 Hz, anteriorly predominant, with a fronto-occipital lag; classically metabolic (hepatic/uremic) encephalopathy.

Burst suppression: generalized high-amplitude bursts alternating with attenuation <10 uV lasting >1 s; implies severe cortical dysfunction or deep anesthesia.

Periodic lateralized epileptiform discharges (PLEDs): lateralized periodic complexes at 0.5-2 Hz, often post-stroke or with HSV encephalitis.

Seizure onset on scalp EEG: rhythmic activity that evolves in frequency, amplitude, and morphology, distinguishable from artifact by field and reactivity.

Nerve conduction velocity (m/s) = distance (mm) / latency difference (ms); measured between two stimulation sites to exclude distal latency.

Upper limb median motor normal values: distal latency <4.2 ms, amplitude >4 mV, conduction velocity >49 m/s; lower limb peroneal CV >40 m/s.

Reduced amplitude with normal latency and velocity suggests axonal loss; prolonged distal latency with normal amplitude suggests demyelination.

Demyelination criteria: CV <75% of lower limit of normal, distal latency >130% of upper limit, or >50% amplitude drop across a segment (conduction block).

F-wave latency reflects proximal conduction; prolonged F-wave with normal distal study indicates proximal demyelination (e.g., Guillain-Barre, radiculopathy).

H-reflex: tibial nerve, S1 radiculopathy; absent in S1 root lesion and in polyneuropathy; normal in L5 lesions.

EMG needle exam sequence: insertional activity, spontaneous activity (fibrillations, positive sharp waves, fasciculations), motor unit potentials, recruitment.

Fibrillations and positive sharp waves indicate active denervation; large polyphasic MUPs indicate chronic reinnervation (collateral sprouting).

Myopathic EMG: short-duration, low-amplitude, polyphasic MUPs with early recruitment; neuropathic: long-duration, high-amplitude MUPs with reduced recruitment.

Visual evoked potential (VEP): P100 wave at ~100 ms recorded over occipital cortex (Oz); delay indicates optic nerve demyelination (e.g., optic neuritis).

VEP requires checkerboard pattern reversal; normal P100 latency is approximately 95-115 ms depending on laboratory and check size.

Brainstem auditory evoked potential (BAEP): waves I (cochlear nerve), II, III (cochlear nucleus), IV, V (inferior colliculus); wave V latency ~5.5-6 ms.

BAEP interpeak latencies: I-III ~2.0 ms, III-V ~1.9 ms, I-V ~4.0 ms; prolonged I-V suggests brainstem dysfunction.

Somatosensory evoked potential (SSEP): tibial nerve stimulation records P37/N45 over scalp; median nerve records N20; used for prognosis after cardiac arrest.

SSEP after cardiac arrest: absent bilateral N20 responses predict poor neurologic outcome with high specificity.

Motor evoked potentials (MEP): transcranial magnetic stimulation; central motor conduction time = MEP latency minus peripheral latency.

Evoked potential interpretation: amplitude reflects axonal loss, latency reflects demyelination; both may be abnormal in compressive or demyelinating lesions.

AASM sleep staging: score in 30-second epochs; wake if >50% alpha; N1 if theta with vertex waves; N2 if spindles/K-complexes; N3 if >20% delta; REM if low-voltage mixed frequency with rapid eye movements and low chin EMG.

Apnea: cessation of airflow >=10 s; hypopnea: >=30% airflow reduction with >=3% desaturation or arousal; AHI = events per hour of sleep.

Obstructive apnea shows continued respiratory effort; central apnea shows absent effort; mixed apnea begins central and becomes obstructive.

OSA severity: AHI 5-15 mild, 15-30 moderate, >30 severe; CPAP is first-line for moderate-to-severe OSA.

Narcolepsy: multiple sleep latency test (MSLT) shows mean sleep latency <8 min and >=2 sleep-onset REM periods (SOREMPs).

REM sleep behavior disorder: REM sleep without atonia on PSG; associated with synucleinopathies (Parkinson disease, Lewy body dementia).

Tilt-table testing: positive if syncope or presyncope with systolic BP drop >=20 mmHg or diastolic >=10 mmHg; vasovagal shows bradycardia.

Quantitative sudomotor axon reflex test (QSART) and thermoregulatory sweat test assess small-fiber autonomic function; heart rate variability assesses cardiovagal tone.

Autonomic testing interpretation: orthostatic hypotension = systolic drop >=20 or diastolic >=10 mmHg within 3 min of standing.

Alpha rhythm: 8-13 Hz posterior dominant rhythm, attenuates with eye opening; reactive alpha is the key marker of normal wakefulness.

N1 sleep: low-amplitude mixed-frequency EEG, vertex sharp waves, slow eye movements; N2 requires sleep spindles (11-16 Hz) or K-complexes.

N3 sleep: delta waves 0.5-2 Hz with peak-to-peak amplitude >75 uV occupying >20% of the epoch.

Temporal lobe spikes are best seen with a tangential montage (e.g., F7-T3, T3-T5, F8-T4, T4-T6) and may be missed on referential montages.

Benign epileptiform transients of sleep (BETS): small sharp spikes in N1/N2, broad field, no focal slowing; do not treat as epileptiform.

Triphasic waves: 1.5-2.5 Hz, anteriorly predominant, with a fronto-occipital lag; classically metabolic (hepatic/uremic) encephalopathy.

Burst suppression: generalized high-amplitude bursts alternating with attenuation <10 uV lasting >1 s; implies severe cortical dysfunction or deep anesthesia.

Periodic lateralized epileptiform discharges (PLEDs): lateralized periodic complexes at 0.5-2 Hz, often post-stroke or with HSV encephalitis.

Seizure onset on scalp EEG: rhythmic activity that evolves in frequency, amplitude, and morphology, distinguishable from artifact by field and reactivity.

Nerve conduction velocity (m/s) = distance (mm) / latency difference (ms); measured between two stimulation sites to exclude distal latency.

Upper limb median motor normal values: distal latency <4.2 ms, amplitude >4 mV, conduction velocity >49 m/s; lower limb peroneal CV >40 m/s.

Reduced amplitude with normal latency and velocity suggests axonal loss; prolonged distal latency with normal amplitude suggests demyelination.

Demyelination criteria: CV <75% of lower limit of normal, distal latency >130% of upper limit, or >50% amplitude drop across a segment (conduction block).

F-wave latency reflects proximal conduction; prolonged F-wave with normal distal study indicates proximal demyelination (e.g., Guillain-Barre, radiculopathy).

H-reflex: tibial nerve, S1 radiculopathy; absent in S1 root lesion and in polyneuropathy; normal in L5 lesions.

EMG needle exam sequence: insertional activity, spontaneous activity (fibrillations, positive sharp waves, fasciculations), motor unit potentials, recruitment.

Fibrillations and positive sharp waves indicate active denervation; large polyphasic MUPs indicate chronic reinnervation (collateral sprouting).

Myopathic EMG: short-duration, low-amplitude, polyphasic MUPs with early recruitment; neuropathic: long-duration, high-amplitude MUPs with reduced recruitment.

Visual evoked potential (VEP): P100 wave at ~100 ms recorded over occipital cortex (Oz); delay indicates optic nerve demyelination (e.g., optic neuritis).

VEP requires checkerboard pattern reversal; normal P100 latency is approximately 95-115 ms depending on laboratory and check size.

Brainstem auditory evoked potential (BAEP): waves I (cochlear nerve), II, III (cochlear nucleus), IV, V (inferior colliculus); wave V latency ~5.5-6 ms.

BAEP interpeak latencies: I-III ~2.0 ms, III-V ~1.9 ms, I-V ~4.0 ms; prolonged I-V suggests brainstem dysfunction.

Somatosensory evoked potential (SSEP): tibial nerve stimulation records P37/N45 over scalp; median nerve records N20; used for prognosis after cardiac arrest.

SSEP after cardiac arrest: absent bilateral N20 responses predict poor neurologic outcome with high specificity.

Motor evoked potentials (MEP): transcranial magnetic stimulation; central motor conduction time = MEP latency minus peripheral latency.

Evoked potential interpretation: amplitude reflects axonal loss, latency reflects demyelination; both may be abnormal in compressive or demyelinating lesions.

AASM sleep staging: score in 30-second epochs; wake if >50% alpha; N1 if theta with vertex waves; N2 if spindles/K-complexes; N3 if >20% delta; REM if low-voltage mixed frequency with rapid eye movements and low chin EMG.

Apnea: cessation of airflow >=10 s; hypopnea: >=30% airflow reduction with >=3% desaturation or arousal; AHI = events per hour of sleep.

Obstructive apnea shows continued respiratory effort; central apnea shows absent effort; mixed apnea begins central and becomes obstructive.

OSA severity: AHI 5-15 mild, 15-30 moderate, >30 severe; CPAP is first-line for moderate-to-severe OSA.

Narcolepsy: multiple sleep latency test (MSLT) shows mean sleep latency <8 min and >=2 sleep-onset REM periods (SOREMPs).

REM sleep behavior disorder: REM sleep without atonia on PSG; associated with synucleinopathies (Parkinson disease, Lewy body dementia).

Tilt-table testing: positive if syncope or presyncope with systolic BP drop >=20 mmHg or diastolic >=10 mmHg; vasovagal shows bradycardia.

Quantitative sudomotor axon reflex test (QSART) and thermoregulatory sweat test assess small-fiber autonomic function; heart rate variability assesses cardiovagal tone.

Autonomic testing interpretation: orthostatic hypotension = systolic drop >=20 or diastolic >=10 mmHg within 3 min of standing.

Alpha rhythm: 8-13 Hz posterior dominant rhythm, attenuates with eye opening; reactive alpha is the key marker of normal wakefulness.

N1 sleep: low-amplitude mixed-frequency EEG, vertex sharp waves, slow eye movements; N2 requires sleep spindles (11-16 Hz) or K-complexes.

N3 sleep: delta waves 0.5-2 Hz with peak-to-peak amplitude >75 uV occupying >20% of the epoch.

Temporal lobe spikes are best seen with a tangential montage (e.g., F7-T3, T3-T5, F8-T4, T4-T6) and may be missed on referential montages.

Benign epileptiform transients of sleep (BETS): small sharp spikes in N1/N2, broad field, no focal slowing; do not treat as epileptiform.

Triphasic waves: 1.5-2.5 Hz, anteriorly predominant, with a fronto-occipital lag; classically metabolic (hepatic/uremic) encephalopathy.

Burst suppression: generalized high-amplitude bursts alternating with attenuation <10 uV lasting >1 s; implies severe cortical dysfunction or deep anesthesia.

Periodic lateralized epileptiform discharges (PLEDs): lateralized periodic complexes at 0.5-2 Hz, often post-stroke or with HSV encephalitis.

Seizure onset on scalp EEG: rhythmic activity that evolves in frequency, amplitude, and morphology, distinguishable from artifact by field and reactivity.

Nerve conduction velocity (m/s) = distance (mm) / latency difference (ms); measured between two stimulation sites to exclude distal latency.

Upper limb median motor normal values: distal latency <4.2 ms, amplitude >4 mV, conduction velocity >49 m/s; lower limb peroneal CV >40 m/s.

Reduced amplitude with normal latency and velocity suggests axonal loss; prolonged distal latency with normal amplitude suggests demyelination.

Demyelination criteria: CV <75% of lower limit of normal, distal latency >130% of upper limit, or >50% amplitude drop across a segment (conduction block).

F-wave latency reflects proximal conduction; prolonged F-wave with normal distal study indicates proximal demyelination (e.g., Guillain-Barre, radiculopathy).

H-reflex: tibial nerve, S1 radiculopathy; absent in S1 root lesion and in polyneuropathy; normal in L5 lesions.

EMG needle exam sequence: insertional activity, spontaneous activity (fibrillations, positive sharp waves, fasciculations), motor unit potentials, recruitment.

Fibrillations and positive sharp waves indicate active denervation; large polyphasic MUPs indicate chronic reinnervation (collateral sprouting).

Myopathic EMG: short-duration, low-amplitude, polyphasic MUPs with early recruitment; neuropathic: long-duration, high-amplitude MUPs with reduced recruitment.

Visual evoked potential (VEP): P100 wave at ~100 ms recorded over occipital cortex (Oz); delay indicates optic nerve demyelination (e.g., optic neuritis).

VEP requires checkerboard pattern reversal; normal P100 latency is approximately 95-115 ms depending on laboratory and check size.

Brainstem auditory evoked potential (BAEP): waves I (cochlear nerve), II, III (cochlear nucleus), IV, V (inferior colliculus); wave V latency ~5.5-6 ms.

BAEP interpeak latencies: I-III ~2.0 ms, III-V ~1.9 ms, I-V ~4.0 ms; prolonged I-V suggests brainstem dysfunction.

Somatosensory evoked potential (SSEP): tibial nerve stimulation records P37/N45 over scalp; median nerve records N20; used for prognosis after cardiac arrest.

SSEP after cardiac arrest: absent bilateral N20 responses predict poor neurologic outcome with high specificity.

Motor evoked potentials (MEP): transcranial magnetic stimulation; central motor conduction time = MEP latency minus peripheral latency.

Evoked potential interpretation: amplitude reflects axonal loss, latency reflects demyelination; both may be abnormal in compressive or demyelinating lesions.

AASM sleep staging: score in 30-second epochs; wake if >50% alpha; N1 if theta with vertex waves; N2 if spindles/K-complexes; N3 if >20% delta; REM if low-voltage mixed frequency with rapid eye movements and low chin EMG.

Apnea: cessation of airflow >=10 s; hypopnea: >=30% airflow reduction with >=3% desaturation or arousal; AHI = events per hour of sleep.

Obstructive apnea shows continued respiratory effort; central apnea shows absent effort; mixed apnea begins central and becomes obstructive.

OSA severity: AHI 5-15 mild, 15-30 moderate, >30 severe; CPAP is first-line for moderate-to-severe OSA.

Narcolepsy: multiple sleep latency test (MSLT) shows mean sleep latency <8 min and >=2 sleep-onset REM periods (SOREMPs).

REM sleep behavior disorder: REM sleep without atonia on PSG; associated with synucleinopathies (Parkinson disease, Lewy body dementia).

Tilt-table testing: positive if syncope or presyncope with systolic BP drop >=20 mmHg or diastolic >=10 mmHg; vasovagal shows bradycardia.

Quantitative sudomotor axon reflex test (QSART) and thermoregulatory sweat test assess small-fiber autonomic function; heart rate variability assesses cardiovagal tone.

Autonomic testing interpretation: orthostatic hypotension = systolic drop >=20 or diastolic >=10 mmHg within 3 min of standing.