Imaging and Management of Unilateral Ventriculomegaly in Term Infants

1. Imaging Strategy

Cranial ultrasound has limited sensitivity for many pathologies – it often misses hypoxic‑ischemic injury, small infarctions, congenital malformations, and encephalitis, identifying an etiologic cause in only ~38 % of neonates with seizures. 1
Term‑equivalent MRI uncovers clinically relevant abnormalities in 11.9 % of cases missed on ultrasound and adds diagnostic information in an additional 39.8 % of patients, making it the preferred modality for comprehensive evaluation. 1, 2
Cerebellar hemorrhage occurs in ~10 % of preterm infants, but ultrasound detects only about 23 % of lesions seen on MRI; lobar cerebellar hemorrhage can produce isolated lateral ventricular dilation without intraventricular hemorrhage. 2
A normal term‑equivalent MRI (absence of major cerebral lesions) strongly predicts normal neurological outcome, supporting its use for prognostication. 1, 2
MRI provides superior visualization of grey‑matter heterotopia, cortical malformations, and posterior‑fossa structures that may explain unilateral ventricular asymmetry. 3

Perform serial cranial ultrasonography every 1–2 weeks to track ventricular size and detect progression. 2
Levene ventricular index >19 mm exceeds the 97th percentile for all gestational ages and signals significant enlargement. 3
Anterior horn width (AHW) >6 mm is considered abnormal (normal < 3 mm). 4
Key clinical signs of increased intracranial pressure (ICP) to monitor:
- Progressive splaying of the sagittal suture. 2
- Acceleration of orbitofrontal head‑circumference growth (>2 cm in <7 days). 5
- Full, tense fontanelle. 5
- Episodes of apnea or bradycardia. 5
- Lethargy or decreased activity. 2
- Feeding intolerance. 5, 2

Surgical treatment is indicated for progressive symptomatic hydrocephalus, defined by:
- Ventricular enlargement above the 97th percentile (Levene index ≈ > 19 mm). 3 and
- Presence of clinical signs of increased ICP (e.g., suture splaying, rapid head‑circumference growth, tense fontanelle). 5, 2
Rapid ventricular expansion to 20–25 mm warrants urgent investigation for obstructive causes, including genetic syndromes. 1

Neurodevelopmental outcome is driven primarily by associated brain injury rather than the degree of ventricular enlargement; isolated mild unilateral ventriculomegaly generally has a favorable prognosis. 6, 2
Even after ventricular size normalizes post‑treatment, children remain at risk for persistent cognitive and behavioral difficulties (e.g., attention‑deficit disorders) later in childhood. 6, 2
Long‑term neurological follow‑up is essential because deficits may emerge later, regardless of whether a shunt was placed. 6, 2