What do spikes or sharp waves usually indicate?
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A propensity for seizures.
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What do spikes or sharp waves usually indicate?
A propensity for seizures.
What activities can be performed during an EEG to evoke abnormal brain activity?
Hyperventilation and strobe lights.
What is one of the primary reasons to order an EEG?
To confirm seizures and/or epilepsy.
How long does a typical EEG session last?
Usually 20-30 minutes, though it can be continuous.
What does EMG stand for?
Electromyography.
What can prolonged distal latencies of motor nerves indicate?
Prolonged distal latencies can indicate distal nerve lesions as a result of demyelination.
What are some sources that can affect nerve conduction studies?
Various factors including limb temperature, patient age, nerve anomalies, technical problems, stimulation problems, measurement errors.
What can cause the EEG abnormality referred to as diffuse background slowing and disorganization?
Metabolic derangements, intoxication, or brain structural abnormalities involving both hemispheres, such as head trauma, strokes, hydrocephalus, multiple sclerosis, or Alzheimer dementia.
What can EMG and nerve conduction studies help differentiate in terms of lesion location?
Lesions proximal and distal, such as peripheral neuropathy from myopathy and motor neuron diseases.
What does EEG compare?
EEG compares the brain electrical activity recorded from brain regions and plots the results over time.
What can be calculated using the response obtained from electrical stimulation in motor conduction studies?
Motor conduction velocity.
How can an EEG be used in the context of brain death?
To confirm electro cerebral inactivity (brain death).
How do nerve anomalies affect nerve conduction studies?
Errors in interpretation due to anatomic variation.
What does amplitude refer to in nerve conduction studies?
Amplitude refers to the height of the evoked responses, measured in millivolts for motor responses and microvolts for sensory responses.
Which disorders that cause pain, sensory loss / tingling, weakness, or cramping be diagnosed by EMG / NCS?
Examples include polyneuropathies, carpal tunnel syndrome, radiculopathy, peroneal neuropathy (foot drop), and amyotrophic lateral sclerosis, myasthenia gravis, Lambert-Eaton myasthenic syndrome, inflammatory myopathies, toxic myopathies, myotonic dystrophy, and hereditary myopathies such as muscular dystrophies.
Do persistently normal EEG tracings exclude the possibility of underlying epilepsy?
No, persistently normal tracings do not exclude the possibility of underlying epilepsy.
How many electrodes are typically placed on the scalp during an EEG?
21 electrodes.
What does EEG stand for?
Electroencephalography.
What is distal latency and how is it measured?
Distal latency is the time between the onset of the stimulus to the onset of the resulting action potential, measured in milliseconds.
What does needle EMG include?
Assessment of spontaneous activity; evaluation of motor unit amplitude, duration, and appearance; and recruitment pattern of the muscle.
Why might an EEG be used during a carotid endarterectomy?
For monitoring cerebral perfusion.
Is it common for patients to sleep during an EEG?
Yes, it is often done with the patient sleeping.
Are EEG findings always specific to a particular condition?
No, findings are often nonspecific.
Which rare neurologic syndromes can be diagnosed using an EEG?
Creutzfeldt-Jakob disease and subacute sclerosing panencephalitis.
In what environment is an EEG typically conducted?
In a quiet environment.
What is delivered over a peripheral nerve in motor conduction studies?
An electrical stimulus.
How can recording spikes and sharp waves during an EEG be useful?
It aids in diagnosing specific epilepsy syndromes, which can guide indicated treatment.
What additional method is often combined with EEG recording?
Simultaneous video recording.
What is a major application of continuous video EEG monitoring in epilepsy treatment?
Epilepsy presurgical evaluation to determine if a patient is a candidate for focal brain resection.
What do conduction velocity studies measure?
Conduction velocity studies measure the speed of impulse conduction in the largest and fastest fibers in the nerve tested.
What does the term 'Electromyography (EMG)' actually include?
It includes nerve conduction studies and EMG.
What is the response obtained from electrical stimulation in motor conduction studies called?
The compound motor action potential.
In what critical care situations is long-term EEG monitoring increasingly used?
Status epilepticus, post-craniotomy, stroke, or head trauma.
Why might conduction velocity studies fail to detect abnormalities in smaller sensory fibers?
Because they measure the speed of impulse conduction in the largest and fastest fibers, potentially missing abnormalities in smaller sensory fibers.
Why is a certain medical procedure not regularly utilized in pediatric patients?
Many patients do not tolerate it.
From where are motor responses recorded in motor conduction studies?
From muscles innervated by the nerve.
What can an EEG demonstrate in the setting of normal imaging?
A metabolic abnormality.
Can EEG be performed on an outpatient basis?
Yes, it can be done on an outpatient or inpatient basis.
How does limb length influence nerve conduction studies?
Longer limbs can result in longer conduction times, which can affect the interpretation of the study results.
How does temperature affect nerve conduction studies?
Lower temperatures can slow nerve conduction velocities, while higher temperatures can increase them.
Can patients with mild-to-moderate Alzheimer dementia have a normal EEG?
Yes, patients with clear memory impairment, language difficulties, and poor attention and concentration in mild-to-moderate Alzheimer dementia may have a normal EEG. EEGs can lack sensitivity, even in the face of glaring clinical abnormalities.
How does EEG assess brain function?
EEG assesses brain function by measuring the electrical activity of the brain.
What are spikes or sharp waves in the context of EEG?
Epileptiform discharges produced by paroxysmal depolarization shifts.
Why are prolonged EEG recordings valuable in critical care settings?
They provide continuous monitoring of the neurologic status of patients, especially when bedside neurologic examination is limited (e.g., in coma).
What does the duration of an evoked response reflect?
Duration reflects the different conduction rates of axons traveling in the nerve and contributing to the evoked response, measured in milliseconds.
What does the EEG report typically end with?
The interpreter’s impression of whether the tracing is normal or abnormal and how these findings correspond to the patient’s clinical picture.
What is considered the gold standard for the diagnosis of seizures?
Concurrent video and EEG monitoring is considered the GS for diagnosis of seizures, epilepsy, and psychogenic nonepileptic seizures and for distinguishing other paroxysmal spells from seizures (ex. syncope, hypoglycemia, or breath-holding spells).
What are the primary indications for EMG/NCS?
For assessing neurological disorders involving muscles, nerves, or the neuromuscular junction.
Evaluating pain, sensory loss or tingling, weakness, or cramping for cause.
Also help differentiate lesions proximal and distal.
Determine cause of symptoms.
Why is age a factor in nerve conduction studies?
Nerve conduction velocities tend to mildly decrease with age, affecting the results of the studies.
How do technical problems affect nerve conduction studies?
Lack of standardization, mistakes in electrode placement, variation in interelectrode distance.
How do stimulation problems affect nerve conduction studies?
Submaximal stimulation, excessive stimulation, reversal of cathode / anode, movement artifact.
How do measurement errors affect nerve conduction studies?
Errors in measuring distance due to change in limb position between time of stimulation and measurement, resulting in inaccurate calculation of conduction velocity.
What are findings of myopathic disease?
(+) spontaneous activity, increased polyphasia, decreased (nonpolyphasic) MUP amplitude, < 80% normal mean MUP duration, early / full recruitment / maximal effort, normal or decreased enveloped amplitude (normal 2-4mV)
What are findings of neurogenic diseases?
(+) spontaneous activity, increased polyphasia, increased MUP amplitude, >120% normal mean MUP duration, reduced / discrete recruitment / maximal effort, normal or increased enveloped amplitude (normal 2-4mV)
