What is the next step for a 5-year-old patient with normal Magnetic Resonance Imaging (MRI) and laboratory (labs) results, presenting with rhythmic right parietal slowing on an Electroencephalogram (EEG)?

Management of Rhythmic Right Parietal Slowing in a 5-Year-Old

In a 5-year-old with rhythmic right parietal slowing on EEG but normal MRI and labs, repeat EEG is warranted because focal EEG abnormalities in children with partial epilepsy are unpredictable and may yield unexpected findings that change management, even when initial structural imaging is normal. 1, 2

Clinical Significance of Focal EEG Abnormalities

• Rhythmic right parietal slowing represents a focal EEG abnormality that indicates potential epileptogenic activity originating from the right parietal region, which is associated with focal (partial) seizures 3, 4

• Focal seizure features show considerably higher positive neuroimaging yields and recurrence rates (up to 94%) compared to generalized seizures, making ongoing monitoring critical 3

• The presence of any focal feature on EEG is independently associated with clinically relevant abnormalities, even when initial imaging appears normal 3

Why Repeat EEG is Necessary

• EEGs in children with epilepsy are not predictable and may yield unexpected results—in fact, 3.4% of children with epilepsy revealed unexpected findings on EEG that completely changed their management 1

• Repeat EEGs are twice as likely to be abnormal compared to initial studies (95% CI 1.3-3, p=0.001), providing additional diagnostic information 1

• Normal EEG findings do not predict normal brain function in children with partial epilepsy—22.2% of children with normal EEG had abnormal MRI findings, and the correlation between EEG and structural imaging is poor (weighted Kappa = 0.105) 2

• EEG abnormalities can evolve over time, and follow-up studies may reveal progression, improvement, or complete normalization that impacts treatment decisions 5

Limitations of Initial Normal MRI

• MRI detected abnormalities not identified by CT in 47% of children with focal seizures, but even MRI can miss epileptogenic lesions initially 3

• A normal MRI does not exclude the presence of functional epileptogenic activity, as demonstrated by cases where focal epilepsy with documented EEG and PET abnormalities occurred despite normal structural imaging 5

• The American College of Radiology notes that only 2% of low-risk patients had abnormal MRI findings, but focal features increase this yield substantially 3

Clinical Decision Algorithm

Immediate actions:

• Schedule repeat EEG, ideally with sleep recording, as sleep activation increases detection of epileptiform abnormalities 1, 4
• Document any clinical seizure semiology carefully, looking specifically for focal motor features (hemiparesis, mouth deviation), sensory symptoms, aphasia, or impaired awareness 3

Monitoring strategy:

• Repeat EEG should be performed within 3-6 months if the child remains asymptomatic, or sooner if any clinical seizures occur 1
• Consider extended EEG monitoring or video-EEG if clinical events occur, as this improves detection of ictal patterns 4

Follow-up imaging considerations:

• If repeat EEG shows persistent or worsening focal abnormalities, consider dedicated epilepsy protocol MRI with 3T scanner if not already performed, including coronal T1-weighted imaging perpendicular to hippocampus and high-resolution 3D sequences 6
• Advanced imaging (FDG-PET) may be considered if seizures develop and become refractory, though this is typically reserved for surgical planning 6

Important Caveats

• Do not assume this represents benign rolandic epilepsy—that diagnosis requires centrotemporal sharp spikes (not parietal slowing) plus specific clinical features of orofacial involvement 7

• Spontaneous remission can occur even in cases of documented focal epilepsy with EEG abnormalities, so aggressive intervention is not always necessary if the child remains seizure-free 5

• The seizure recurrence rate after a first seizure in neurologically normal children is 66.4%, and abnormal EEG findings poorly predict recurrence at 9,18, or 27 months 8

• Focal parietal abnormalities can be associated with various etiologies including subtle cortical dysplasias, prior ischemic injury, or functional epileptogenic zones not visible on standard MRI 3, 2