What is the most likely diagnosis in a 2½‑year‑old girl with brief staring episodes, 3‑5‑second head‑shaking automatisms, atypical eye movements, and immediate return to baseline without post‑ictal confusion?

Childhood Absence Epilepsy (Typical Absence Seizures)

The most likely diagnosis is childhood absence epilepsy, characterized by typical absence seizures. 1

Clinical Features That Support This Diagnosis

The presentation is classic for typical absence seizures:

• Brief staring episodes lasting 3-5 seconds with abrupt onset and termination are the hallmark of typical absence seizures 2, 3
• Immediate return to baseline without post-ictal confusion distinguishes absence seizures from other seizure types 1, 2
• Age of 2.5 years falls within the typical onset range for childhood absence epilepsy, which usually begins between 6 months and 5 years 4, 2
• Head shaking and atypical eye movements represent motor automatisms commonly seen during typical absence seizures, with myoclonic components (particularly facial) being the most frequent motor manifestation 2, 3

Diagnostic Evaluation Required

EEG is mandatory and the single most important diagnostic test for any child with suspected absence seizures 1:

• The characteristic EEG pattern shows generalized 3-4 Hz spike-and-wave discharges during the clinical event 2, 3
• Hyperventilation provokes absence seizures in approximately 90% of untreated patients, making it a valuable diagnostic maneuver 2
• EEG should be obtained promptly and not delayed 1

Laboratory testing should be selective, not routine 1:

• Order labs only when clinical circumstances suggest metabolic derangements such as vomiting, diarrhea, dehydration, or failure to return to baseline 1
• Fingerstick glucose should be checked if there is any concern for hypoglycemia 1

Neuroimaging is not typically indicated for uncomplicated absence seizures where the child has returned to baseline 1:

• MRI is the preferred modality if neuroimaging is obtained 1
• Non-urgent MRI should be considered only in children with significant cognitive or motor impairment of unknown etiology, unexplained abnormalities on neurologic examination, or in children aged less than 1 year 1

Key Differentiating Features

This presentation is not consistent with:

• Febrile seizures – no fever present, and simple febrile seizures do not require imaging 4
• Atypical absence seizures – these typically last longer (15-30 seconds or more), occur in children with developmental delay or mental retardation, and have a less favorable prognosis 5, 3
• Benign paroxysmal torticollis – episodes last minutes to days, onset before 3 months of age, and present as head tilt rather than staring 4
• Sandifer syndrome – episodes occur after eating and are secondary to gastroesophageal reflux 4

Treatment Considerations

Once the diagnosis is confirmed by EEG, first-line treatment options include 2:

• Valproic acid controls absences in 75% of patients and also controls generalized tonic-clonic seizures (70%) and myoclonic jerks (75%) 2
• Ethosuximide controls 70% of absences but is unsuitable as monotherapy if other generalized seizures coexist 2
• Lamotrigine may control absences and generalized tonic-clonic seizures in 50-60% of patients 2

Disposition

Outpatient management is appropriate if the child has returned to baseline, has a normal neurologic examination, and no concerning features on history 1:

• Arrange outpatient EEG if not performed in the emergency department 1
• No hospital admission is required for uncomplicated first-time absence seizures when the child has returned to baseline 1

Critical Pitfalls to Avoid

• Do not routinely order extensive laboratory panels in otherwise healthy children who have returned to baseline, as these are very low yield 1
• Do not delay EEG, as it is the single most important diagnostic test and should be obtained promptly 1
• Do not confuse brief absence seizures with attention lapses – the presence of motor automatisms (head shaking, eye movements) and the stereotyped nature of the episodes point toward seizures rather than behavioral inattention 2, 3