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(BQ) Part 2 book Practical guide for clinical neurophysiologic testing EEG has contents: Activation procedures, EEG of premature and full term infants, artifact recognition and technical pitfalls, benign EEG patterns,... and other contents.
9 Activation Procedures THORU YAMADA and ELIZABETH MENG Activation procedures include various sensory and pharmacological stimulations to alter the physiological state They are usually aimed at eliciting or enhancing abnormal activity, especially epileptiform activity The most commonly used sensory stimulation is photic stimulation Others include tactile or electrical stimuli for somatosensory stimulation and music or sounds for auditory stimulation Pharmacological activation includes pentylenetetrazol to induce a seizure or benzodiazepine to attenuate one The most routine activation procedures in any EEG laboratory are hyperventilation (HV), photic stimulation (PS), and sleep Hyperventilation NORMAL HYPERVENTILATION RESPONSE This procedure consists of deep and regular breathing at a rate of about 3 to 4 per 10 seconds for a period of to minutes In young children, HV can be successfully performed by asking the child to blow on a pinwheel A characteristic HV response consists of bilaterally diffuse and synchronous slowwave bursts, initially with theta frequency and then progressing to delta frequency This is called “HV buildup” (Figs 9-1A and B and 9-2A and B) The amplitude may reach as high as 500 μV Theta–delta buildup by HV is usually anterior dominant in adolescents or adults but may be posterior dominant in children These occur in a serial semirhythmic fashion with fluctuating amplitude (Video 9-1) The effect is most prominent in children between the ages and 12 years and progressively decreases toward adulthood (compare Figs 9-1B and 9-2B); a clear HV response is seen in about 70% of children, but in adults, it may be less than 10%.1 HV effects, however, vary considerably from one individual to another Physiologically, HV reduces the carbon dioxide concentration (PCO2), which causes vasoconstriction and reduction of cerebral blood flow The reduction of PCO2 (hypocapnia) is likely the major factor in producing HV buildup.1 HV buildup is enhanced by a blood sugar level below 80 mg/100 mL.2 Therefore, HV buildup may be more prominent when the patient is hungry or his/her last meal was some time ago In subjects who show a low-voltage and poorly defined alpha rhythm, HV may bring out a better defined alpha rhythm FIGURE 9-1 | Comparison of resting EEG in the awake state (A) and EEG during hyperventilation (B) in a 5-year-old boy Note the increase of posterior delta waves (posterior slow waves of youth) and semirhythmic 3- to 4-Hz generalized delta–theta bursts during hyperventilation (B) FIGURE 9-2 | Comparison of resting EEG in the awake state (A) and EEG during hyperventilation (B) in a 38-year-old man Note the generalized bursts of 4- to 6-Hz theta waves This is unusually prominent HV response in this age of patient The frequency of bursts is faster than that seen in children (Fig 9-1B) Some delta bursts induced by HV may include “spiky” or spike-like discharges (small notched spikes preceding or mixed with theta–delta activity) especially in children Unequivocal spikes or clear focal or lateralizing (focal) changes elicited by HV are considered to be abnormal After cessation of HV, the patient may complain of numbness or tingling in the fingers and lips, transient blurring of vision, or ringing in the ears Some may even show changes of consciousness or awareness These symptoms are self-limiting and are not necessarily associated with EEG changes or related to the degree of buildup Likewise, after cessation of HV, the slow waves disappear quickly and the EEG returns to the pre-HV state within 30 seconds In some subjects, though, the effect may continue for a minute or longer One should be cautious in interpreting a long-lasting post-HV effect, since some subjects may continue to hyperventilate even after being told to stop The technologist should observe carefully to make sure that the patient did indeed stop HV If the delta bursts appear longer than 1 minute in the post-HV period, they are not likely related to the HV effect (An exception to this is seen in moyamoya disease.)3,4 ABNORMAL HYPERVENTILATION RESPONSE HV is a well-known activation procedure for inducing absence seizures HV activates more than 80% of untreated children with absence seizures.5 It is important for the technologist to document clinical signs associated with an absence seizure With a sudden onset of rhythmic (monomorphic) 3-Hz spike– wave bursts (Fig 9-3; Video 9-2, also see Video 10-6), the patient usually stops HV and often stares into space, sometimes with eyelid or facial muscle twitches If 3-Hz spike–wave bursts last longer than 5 seconds, the technologist is usually able to observe a clinical change by examining the patient’s level of consciousness An astute technologist will quickly ask the patient to remember words presented during the event and ask the patient after the event if he or she can recall the presented words If the patient’s communication or consciousness is impaired, the patient will not be able to recall the word spoken during the episode A more accurate assessment may be made by testing reaction time; the patient is instructed to press a button (which makes a mark on the EEG recording) in response to an auditory signal given by the technologist during the event of 3-Hz spike–wave bursts With cessation of the spike–wave bursts, the patient usually resumes HV without being prompted by the technologist There is no postictal confusion or impaired consciousness FIGURE 9-3 | Typical 3-Hz spike–wave bursts, characteristic for absence seizures, induced by hyperventilation in an 8-year-old girl Apparently, a clinical seizure was associated with the event involving staring and blinking as noted by a technologist HV may also activate focal or other types of generalized seizures, or precipitate interictal epileptiform activity, though the incidence of such activation is far less (~5%) than that for absence seizures Much more vigorous and prolonged HV is usually required to elicit partial seizures.6 HV may accentuate focal slowing, which is sometimes useful for verifying uncertain or subtle focal features observed in the resting EEG One unique HV effect has been observed in moyamoya disease in which the delta bursts reappear 3 to 5 minutes after cessation of HV, called the “re-buildup” HV effect.3,4 LRDA See Lateralized IRDA (LRDA) LSD See Lysergic acid diethylamide (LSD) LTM EEG See Long-term monitoring of EEG (LTM EEG) Lymphoma Lysergic acid diethylamide (LSD), effect on EEG M Magnetoencephalography (MEG) Manic–depressive disorder and lithium Material safety data sheets (MSDS) Medial geniculate nucleus Median nerves Medical devices, interfering artifacts from MEG See Magnetoencephalography (MEG) Mesial temporal lobe epilepsy (MTLE) Metabolic encephalopathy toxic Methohexital Methylphenidate, effect on EEG Micropsia Middle cerebral artery Midline lesions Midline thalamic pacemaker theory Midline theta rhythm Migraine headache Monoamine oxidase (MAO) inhibitors Montages average reference negative spike schematic model spike discharges bipolar deflection double phase reversal end of chain effect negative spike pairs of electrode phase reversal relationships positive spike creation and selection awake EEG circumferential longitudinal sleep EEG transverse triangular Laplacian method referential alpha rhythm average reference recording Cz reference ear contamination ear reference frontopolar electrodes monopolar sharp discharge spike discharge Motor aphasia Motor system Moyamoya disease MTLE See Mesial temporal lobe epilepsy (MTLE) Mu rhythm Multifocal interictal epileptiform discharges Multi-infarct dementia Multiple sclerosis (MS) Muscle artifacts tonic Musicogenic epilepsy Myelin Myelinated fibers Myoclonic encephalopathy, in nonprogressive disorders Myoclonic epilepsies with ragged red fibers (MERRF syndrome) Myoclonic jerks Myoclonic seizure focal Myoclonus Myogenic artifacts N Nasion Nasopharyngeal (NP) electrodes National Fire Protection Association (NFPA) NCS See Nonconvulsive seizures (NCS) NCSE See Nonconvulsive status epilepticus (NCSE) Neocortical temporal lobe epilepsy (NTLE) Neonatal infants, EEG abnormalities amplitude asymmetry between two hemispheres awake and sleep states burst suppression pattern continuous low-voltage/near-isoelectric pattern dysmaturity ictal positive sharp waves sharp and spike discharges of negative polarity general characteristics of normal active vs quiet sleep and wake EEG pattern continuity vs discontinuity delta brush focal sharp waves and spikes frontal sharp transients synchrony vs asynchrony temporal theta bursts recording techniques technologists role Neonatal montages Neonatal seizures Nernst equation Nervous system anatomy and physiology action potentials neurons peripheral nerve postsynaptic membrane potential resting membrane potentials synapse cortical activity relationship between, cellular activity and cortical waves structures Neurocardiogenic syncope Neuroleptics Neuromuscular blocking agents Neuronal ceroid lipofuscinosis Neurons Neuropsychiatric drugs, effect on EEG0 Neurotransmitter Nitrous oxide, effect on EEG N-methyl-D-aspartate (NMDA) receptor Node of Ranvier Nonconvulsive focal seizure Nonconvulsive seizures (NCS) CCEEG evaluation incidence of Nonconvulsive status epilepticus (NCSE) CCEEG evaluation incidence of Nonmyelinated fiber Nonphysiological artifacts/electrical interference artifacts electrode artifacts electrostatic artifacts high-frequency noise 60-Hz artifact interfering artifacts from medical devices Non-REM (NREM) sleep Nonrhythmic artifacts Nonspecific projection system NREM sleep See Non-REM (NREM) sleep Nyquist frequency Nystagmus (horizontal eye movement) O Occipital intermittent rhythmic delta activity (OIRDA) Occipital lesions Occipital lobe function seizures Occipital paroxysms, childhood epilepsy with Occipital tumors Occipitally predominant GRDA (OIRDA) Ohm’s law Ohtahara syndrome OIRDA See Occipital intermittent rhythmic delta activity (OIRDA) Olfactory hallucination Opsoclonus artifacts Orientation of generators Oxcarbazepine (Trileptal) P Pacemaker artifact Panayiotopoulos syndrome Pancuronium Paradoxical arousal response Parietal epilepsy Parietal lobe seizures Parieto-occipital fissure Parkinson’s disease Paroxysmal activity, abnormal Paroxysmal depolarization shift (PDS) Paroxysmal discharge rhythmic theta and delta slow waves without Partial complex seizures Paste application, electrode PDS See Paroxysmal depolarization shift (PDS) Pentylenetetrazole Perineurium Periodic discharges (PDs) Periodic lateralized epileptiform discharges (PLEDs) Periodic patterns Peripheral fibers Peripheral nerve Petit mal status Phantom spike and wave Pharmacological activation Phenytoin Photic response, atypical Photic stimulation atypical photic response photic driving response photomyogenic response (PMR) photoparoxysmal responses (PPRs) procedure Photoconvulsive response Photographic summation technique Photomyoclonic response/photomyogenic response (PMR) Photosensitive epilepsy Platinum electrodes PLEDs See Periodic lateralized epileptiform discharges (PLEDs) PMR See Photomyogenic response (PMR) Polymorphic delta slow waves Polysomnography (PSG), EMG Positive occipital sharp transients of sleep (POSTS) Positive spike bursts, 14- and 6-Hz Postanoxic cerebral insult after cardiac arrest Postconvulsive status epilepticus Posterior cerebral artery Posterior communicating artery Posterior spinal artery Posterior tibial nerve Postictal aphasia, tonic–clonic convulsions with Postsynaptic potential (PSP) Potassium Power, calculation formulas Power transformers ground loop isolation magnetic field operation primary coil second coil voltage and current Precentral gyrus Prednisone therapy Pregabalin (Lyrica) Premature infants, EEG conceptional age 27 to 29 weeks 29 to 31 weeks 32 to 34 weeks 34 to 37 weeks 38 to 40 weeks 41 to 44 weeks less than 27 weeks ictal abnormalities specific characteristics delta brush focal sharp waves and spikes frontal sharp transients temporal theta bursts Premature ventricular contraction (PVC) Prion disease Progressive myoclonic epilepsy Projection system Propofol, effect on EEG Prosthetic eye Psychomotor seizure Psychomotor variant See Rhythmic midtemporal theta of drowsiness (RMTD) Pulse artifact PVC See Premature ventricular contraction (PVC) Pyramid Q Quantitative EEG (qEEG) analyses for CCEEG Quiet sleep EEG pattern R Rapid bursts See Delta brush Rapid eye movement (REM) sleep RDA See Rhythmic delta activity (RDA) Reactivity, EEG change Receptive aphasia Referential montages alpha rhythm average reference recording Cz reference ear contamination ear reference frontopolar electrodes monopolar sharp discharge spike discharge Reflex epilepsy Reflex myoclonus, reticular REM sleep See Rapid eye movement (REM) sleep Renal failure and dialysis Repetitive blinking Resistors in parallel in series Respiration artifact Resting membrane potentials Reticular activating system (RAS) Reticular reflex myoclonus Reversed hat band montage Reye’s syndrome Rhythm See specific types of rhythm Rhythmic artifacts Rhythmic delta activity (RDA) See also specific types of rhythmic delta activity intermittent Rhythmic eye movements (opsoclonus) artifacts Rhythmic midtemporal theta of drowsiness (RMTD) Rhythmicity Ripple of prematurity See Delta brush RMTD See Rhythmic midtemporal theta of drowsiness (RMTD) Rocuronium Rolandic spikes S SAH See Subarachnoid hemorrhage (SAH) Sail wave Salaam attack Salaam spasms Saltatory conduction Scalp EEG Schwann cell Sclerosis, tuberous Sedative drugs, effect on EEG SEF See Spectral edge frequency (SEF) Seizure See also specific types of seizure diagnosis EEG abnormalities associated with ictal discharges periodic discharges spike and wave discharges generalized secondary generalized semiology Semicoma Semicomatose, arousal response in Sensitivity Sensors, digital EEG Sensory agnosia Sensory aphasia Severe myoclonic epilepsy in infants Sharp discharges Silver–silver chloride electrode SIRPIDs See Stimulus-induced rhythmic periodic/ictal discharges (SIRPIDs) 6-Hz spike and wave bursts 60-Hz artifact Skin preparation, electrodes Skull defect (Breach rhythm) Sleep activation active NREM quiet REM stage III and IV sleep (N3) Sleep apnea Sleep deprivation Sleep spindles abundant asynchronous duration 15-month-old baby 5-month-old baby K complex sedative medications 22-year-old man 22-year-old woman unilateral depression of V waves Slow spike and wave (SSW) complexes Slow wave sleep (SWS) Slow wave See specific types of slow waves Slow-drifting eye movement Slurred speech Small sharp spikes (SSSs) Sobbing Sodium Sodium–potassium pump Somatosensoryevoked potentials Spastic hemiparesis Spatial factor Spectral edge frequency (SEF) Spike and wave bursts, 6-Hz Spike and wave discharges Spike-wave bursts Spinal cord arteries vascular system Spindle coma Spindle-like fast See Delta brush Square-wave calibration signal, EEG labs SREDA See Subclinical rhythmic electrographic discharge in adults (SREDA) SSPE See Subacute sclerosing panencephalitis (SSPE) SSSs See Small sharp spikes (SSSs) Stable cyst Startle epilepsy Status epilepticus absence complex partial focal generalized convulsive nonconvulsive Stimulus Stimulus-induced rhythmic periodic/ictal discharges (SIRPIDs) Stroke, ischemic Stupor Stuporous state, paradoxical arousal response in Sturge–Weber syndrome Subacute sclerosing panencephalitis (SSPE) Subarachnoid hemorrhage (SAH) Subclavian artery Subclinical rhythmic electrographic discharge in adults (SREDA) Subdermal needle electrodes Subdural hematoma chronic Subtentorial lesions Succinylcholine Sudden unexpected death in epilepsy (SUDEP) Sulci Superior colliculi Supratentorial tumor Swallowing Sweat artifacts Sylvian fissure Symmetry, EEG activity Symptomatic epilepsy Synapse Synaptic cleft Synchrony, EEG activity Syncopal attacks, vasovagal Synthetic opiates, effect on EEG T Tachycardia, ventricular The Task Force for Determination of Brain Death in Children Technologist Tegmentum Temporal factors Temporal intermittent rhythmic delta activity (TIRDA) Temporal lobe seizures Temporal lobe epilepsy (TLE) mesial neocortical Temporal sawtooth/Temporal sharp transient See Temporal theta bursts Temporal slow waves Temporal theta bursts Temporally predominant GRDA 10–20 International System of Electrode Placement TGA See Transient global amnesia (TGA) Thalamic hemorrhage Thalamus Therapeutic hypothermia Theta activity Theta coma Theta–delta waves slow waves alpha rhythm associated with interspersed without paroxysmal discharges 3-Hz spike–wave bursts TIA See Transient ischemia attack (TIA) Time constant (TC) calibration signal high-frequency activity low-frequency activity resistance and capacitance circuit values of Time scale, amplifier controls TIRDA See Temporal intermittent rhythmic delta activity (TIRDA) TLE See Temporal lobe epilepsy (TLE) Tongue movement Tonic muscle artifacts Tonic seizures Tonic–clonic convulsions with developmental delay occipital spikes in patients with with postictal aphasia Tonic–clonic seizures generalized Tonic-clonic status epilepticus, generalized Topiramate (Topamax) Topographic mapping Toxic agents, effect on EEG Toxic metabolic encephalopathy Trace alternant (TA), EEG Trace discontinue (TD), EEG Traditional electroencephalogram (EEG) Transient global amnesia (TGA) Transient ischemia attack (TIA) Transients TRANSISTOR Transverse montages Tremor artifact Triangular montages Tricyclic antidepressants Trigeminal nerve Triphasic waves in Creutzfeldt–Jakob disease in hepatic encephalopathy in uremic encephalopathy Tuberous sclerosis U Ulnar nerves Unconscious Unilateral depression of beta rhythm Unverricht–Lundborg disease Uremic encephalopathy chronic V Valproic acid, effect on EEG Vascular etiology Vasospasms Vasovagal syncopal attacks Ventricular system Ventricular tachycardia Ventriculomegaly, congenital Vertebral artery Vertex sharp waves transients (V waves) Vertical scale, amplifier controls Vigabatrin (Sabril) Viral encephalitis Vitamin deficiency Voltage divider See also Amplifiers von Marxow, F W Wake EEG pattern Wakefulness Waveforms, EEG patterns Waves See specific types of wave Wernicke–Korsakoff encephalopathy Wernicke’s area West syndrome WHAM (Wake, High amplitude, and Anterior dominant in Male) Wicket spikes Z Zonisamide (Zonegran) ... CONTRAINDICATIONS HYPERVENTILATION OF The American Clinical Neurophysiology Society (formerly American EEG Society)7 recommended that HV should not be performed in certain clinical settings Included contraindications are acute stroke, recent intracranial hemorrhage,... activation procedure for inducing absence seizures HV activates more than 80% of untreated children with absence seizures.5 It is important for the technologist to document clinical signs associated... interictal epileptiform activity, though the incidence of such activation is far less (~5%) than that for absence seizures Much more vigorous and prolonged HV is usually required to elicit partial seizures.6