In this episode Jen, Meshia, and Petra discuss taking a thorough patient history.
Petra explains that when they are taking the history on a pediatric patient the following questions need to be asked:
- Was the patient born on time or premature? (late doesn’t matter)
- What was the gestational age or pre-menstrual age of the patient?
- Any complications at birth or during pregnancy, such as illness or anoxia?
- Any trauma at birth or during the pregnancy?
- Any developmental delays noted at birth or during childhood?
She states that the normal values for EEG are based on age related changes. Patients over 16 share the majority of features but under age 16 the normal features vary in groups. The groups are: 8-16; 4-7; 1-3; 2-12 months and every 2 weeks of development down to age 26 weeks premenstrual age. Trauma, infections, pre-eclampsia, low birth weight, intra-uterine growth retardation are the biggest complications.
Jen explained that in IOM when we are getting a patient’s history in pre op we ask if the patient has a history of seizures. If they say yes we expand further to ask if they are on any medication for the seizures because seizures is a contraindication for motor evoked potentials. If you have a patient with a history of seizures (which typically means they are on anti-seizure medication) running MEPs can cause a patient to have seizures, but the ACNS guidelines for MEPs state that that risk is actually low, with about 5 patients out of 15,000.
Petra explained the most relevant questions we need to ask when a patient is sent for an EEG when suffering seizures:
- At any point during life, has the patient had seizures, spells, episodes or syncope?
- If yes, please answer the following:
- what type of event?
- At what age did the event start?
- Is there a known precipitating and/or relieving factor for the event?
- How frequently does the event occur? How long does the average event last? When was the most recent event?
- Describe the symptoms from beginning to recovery of baseline state. Include any aura or post ictal symptoms.
- What medications have been used to abort events?
- Are there any similar circumstances to the events, i.e., smells, sounds, sights, foods, exercise or stress?
- Any additional type of events? If so, please describe as stated above for each type of event.
Jen talks about other contraindications for MEPs. It is important to ask if the patient has cochlear implants, a pacemaker, any metal in the head, or previous head trauma or surgery. In the case of cochlear implants, MEPs can actually short circuit the implant. If the patient has any metal in their head it can cause the stimulation for MEPs to be shunted and affect your MEPs. And finally, if the patient has a pacemaker MEPs can actually trigger it to deliver a volt.
Petra then continues the discussion explaining that changes to the skull can make a huge impact on the EEG. Some questions to ask would be:
- Any history of head trauma or surgery?
- If yes, when? Trauma or Surgery? If trauma, what caused the trauma? Any period of loss of awareness? if so, how long? How long did it take the patient to return to their baseline state?
- Any history of stroke, blood clots, TIAs? If so, describe.
Meshia continues that when taking the patient history in preop it is important to ask if the patient has diabetes. If they do have diabetes, follow up asking if the patient has been diagnosed with peripheral neuropathy. If a patient has peripheral neuropathy you can see an increase in latency in your waveforms or a reduced amplitude in you baseline data. It is important to document this. Something else I would like to point out that may seem obvious, but could be an easy oversight. Did the pt walk into the hospital today, or did they require any assistance (cane, wheel chair) I like to ask the patient to wiggle their toes, fingers, etc. If any data changes were to occur during the case that may suggest a post surgical neurological deficit post, then how the patient actually arrived the day of the surgery would be extremely helpful.
Petra states that during an EEG we conduct activation procedures or tasks that can elicit seizures. These activation procedures are fairly safe when conducted carefully. We have to screen for certain health conditions prior to performing activation procedures or we could cause harm to the patient. For example:
- Does the patient have:
- asthma or other lung disease, sickle cell anemia, or are they pregnant? (Contraindications for hyperventilation)
- history of seizure to strobe lights? If yes, describe. Any EEG showing photic induced seizures?
- When did the patient eat last?
- Was the patient sleep deprived? If so, when did they sleep prior to the test in the last 24 hours?
Sleep deprivation is a two-fold assistant. It aggravates the brain and elicits sleep. There are many seizure types in which the seizures occur at insert of sleep or upon Awakening. There are also seizures only brought out by sleep deprivation.
Timing between the EEG and the patient’s last meal can affect the EEG overall because hypoglycemia causes slowing and because it an amplify the slowing associated with hyperventilation.
The last important question we have to ask is:
- What medications were taken in the last 24 hours?
Anticonvulsants can blunt seizure discharges. The interpreting provider must know if the patient is being treated. Benzodiazipines cause excess fast activity. Antipsychotics can cause excess fast activity or excess slowing on an EEG.