Evaluating the Feasibility of a Portable Electroencephalogram Device in Diagnosing Transient Ischemic Attack and Stroke

Transient ischemic attack (TIA) has classically been defined as an ischemic episode, in which patients can present with transient neurological symptoms, in the absence of brain injury. However, recent literature showed evidence of cerebral tissue injury in TIA, which suggests that focal cerebral ischemic events are essentially cerebral infarctions. Based on this, TIA should be considered a minor ischemic stroke. TIA/minor stroke, as all strokes, should be considered a medical emergency. Identifying and treating patients with TIA in a timely manner is important for stroke prevention. Literature suggests that more than 10% of patients diagnosed with TIA have a stroke within the next 90 days, of which half of these cases occur in the first 48 hours.

When a patient presents to the emergency department or an outpatient clinic with transient or mildly observable neurologic symptoms, it is difficult to diagnose an ischemic event from other TIA/stroke mimics such as migraine, seizure, etc. This is mostly because diagnosis of TIA/minor stroke relies on subjective, retrospective report. One study found that about 45% of referrals to a rapid stroke prevention clinic for query TIA/stroke were TIA mimics. Diagnosis also becomes more uncertain for patients who present with symptoms other than motor and speech deficits, which are more classically seen with brain ischemia, such as dizziness or sensory symptoms.

Advances in brain imaging have facilitated the evaluation of brain injury in the context of transient neurological symptoms. Diffusion-weighted MRI can show infarcts in one-third of patients with TIA. However, this poses the risk of missing patients who are MRI-negative and discharging patients without appropriate stroke preventative care. Furthermore, there are also resource limitations, which make it difficult to do an MRI brain in all patients who present with transient or mildly observable neurological symptoms. For example, there is limited time during a code stroke, which makes a CT scan the more feasible option, and additionally there are resource constraints depending on the setting of care (ie rural setting, outpatient clinic). Therefore, this warrants the need for a portable diagnostic device to assist with timely and accurate evaluation of possible TIA/stroke.

Electroencephalogram (EEG), which is typically used in the context of epilepsy, provides a non-invasive measure of brain function. EEG also has potential to detect cerebral ischemia, given that there are metabolic and electrical changes of cortical neurons during times of reduced cerebral blood flow. However, the use of EEG and specifically portable EEG, in the context of acute stroke and TIA is limited.

In the literature, one study found that a 3-minute portable resting EEG accurately identified patients with large acute ischemic strokes in the emergency department and correlated with infarct volume. Another study, which used a 3-minute EEG obtained from a single electrode over the left frontal lobe, found unique EEG profiles for TIA versus ischemic stroke patients. However, these preliminary findings were limited due to small sample size and EEG data typically was obtained on the second day after symptom onset.