Posterior Fontanelle Sonography: An Acoustic Window into the Neonatal Brain

Normal coronal sections of the PF (superior to inferior). CA indicates calcar avis; Ch, choroid plexus; CH, cerebellar hemispheres; LV, lateral ventricle trigone; OH, occipital horn; OL, occipital lobe; SA, subarachnoid space; and T, tentorium.

A–C, Images in a neonate at 30 weeks’ gestational age.

A, The most superior coronal view.

B, The middle coronal view.

C, The inferior view.

D, Same section as in C in a neonate at 25 weeks’ gestational age shows a more rounded configuration of occipital horns and a wide (up to 15 mm) subarachnoid space with internal echogenic dots corresponding to vessels.

Normal sections of the PF. CF indicates calcarine fissure; Ch, choroid plexus; FM, foramen magnum; M, medulla; OH, occipital horn; OL, occipital lobe; OS, occipital squama; PO, parieto-occipital fissure; QC; quadrigeminal cistern; S, aqueduct of Sylvius; SA, subarachnoid space; SC, supracerebellar cistern; Th, thalamus; V, vermis; and 4V, fourth ventricle.

A, Midsagittal view.

B, Parasagittal view.

C, More lateral parasagittal view.

Sonograms obtained in a neonate with a presumptive diagnosis of posterior fossa malformation at prenatal sonography.

A, AF midline sagittal view shows a cystic image (asterisk) in the posterior fossa behind the cerebellum.

B, PF midline sagittal view clearly demonstrates that the lesion corresponds to a megacisterna magna, depicting the normal-sized cerebellum vermis and fourth ventricle. Note that the cystic lesion (asterisk) extends around the cerebellum without compressing it, as often occurs with arachnoid cysts.

Images obtained in a premature neonate with systemic candidiasis treated with prolonged antibiotic therapy; disease was confirmed on the basis of blood culture findings.

A, AF right parasagittal sonogram demonstrates multiple, rounded, hyperechoic nodules—some with central umbilication—affecting the basal nuclei (arrowheads).

B, PF right parasagittal sonogram also shows multiple, rounded, hyperechoic lesions affecting the frontal and parietal lobes (arrowheads).

C, Parasagittal T1-weighted MR image confirms the sonographic findings. (The child survived, and the lesions [arrowheads] calcified.)

Images of cerebellar abscesses in a 45-day-old neonate presenting with AF bulging and lethargy. A culture of fine-needle aspiration material isolated S aureus.

A, PF coronal sonogram reveals bilateral occipital horn dilatation and enlarged left cerebellar hemisphere with two hypoechoic lesions (arrowheads).

B, PF left parasagittal sonogram shows lateral ventricle dilatation and the cerebellar abscesses (arrowheads).

C, Contrast-enhanced T2-weighted MR image confirms the sonographic findings (arrowheads).

Sonograms obtained in a premature neonate with grade I hemorrhage that was better delineated through the PF than through the AF.

A, AF left parasagittal view shows an equivocally echogenic image (arrow). The choroid plexus (Ch) is not well depicted.

B, PF left parasagittal view clearly depicts the echogenic lesion (arrow) independent of the choroids (Ch). On follow-up studies, the lesion disappeared.

Sonograms obtained in a premature neonate with grade II hemorrhage.

A, AF left parasagittal view shows a normal-appearing left lateral ventricle.

B, PF left parasagittal view reveals a small clot in the posteriormost portion of the occipital horn (arrow).

Sonograms obtained in a premature neonate with grade II intraventricular hemorrhage.

A, AF right parasagittal view shows inconclusive appearance of the choroid plexus.

B, PF right parasagittal view clearly depicts two clots in the occipital horn (arrows).

Sonogram of the occipital horn layering. Coronal PF view shows a fluid-fluid level (arrowheads) caused by blood and CSF in a slightly dilated left occipital horn.

Sonograms of the calcar avis simulating intraventricular hemorrhage.

A, AF parasagittal view shows a rounded masslike image mimicking an intraventricular clot within the occipital horn (arrow).

B, PF parasagittal view demonstrates that the mass is the calcar avis (arrow). Note its continuity with the occipital white matter and the calcarine fissure (CF).

Sonograms of bilateral cerebellar hemorrhage obtained in a neonate without intraventricular hemorrhage at 30 weeks’ gestational age.

A, AF coronal view shows the lateral ventricles to be normal. Echogenic areas in the subtentorial space (arrows) of indistinct cerebellar or extracerebellar origin are seen.

B, PF coronal view clearly reveals bilateral cerebellar hemorrhages (arrows).

C, PF coronal view obtained 1 week later shows that the hemorrhages have decreased in size and echogenicity (arrows).

Sonograms obtained in a premature neonate with massive intraventricular and unilateral cerebellar hemorrhages. T indicates tentorium.

A, AF coronal view shows echogenic material occupying the right lateral ventricle (asterisk) that hinders correct visualization of the cerebellum owing to slight shadowing.

B, PF coronal view clearly depicts left echogenic cerebellar hemorrhage (arrows). OH indicates the occipital horn.

Sonograms of abnormal peritrigonal hyperechogenicity in a premature neonate with periventricular leukomalacia.

A, AF left parasagittal view depicts heterogeneous peritrigonal hyperechogenicity with areas of cavitation.

B, PF left parasagittal view. Coarse peritrigonal echogenicity and cavities are evident.

Sonogram and gross specimen obtained in a patient with discrepant findings at sonography and autopsy.

A, PF coronal sonogram shows echogenic material in the occipital horns (asterisk) corresponding to intraventricular hemorrhage. The cerebellum and basal subarachnoid space seem normal. CH indicates cerebellar hemispheres; T, tentorium; and 4V, fourth ventricle.

B, Macroscopic view of the specimen 1 day later shows a hemorrhage surrounding the right cerebellar hemisphere.