Objective To assess diagnostic accuracy of cranial ultrasound (CUS) performed through the anterior fontanelle (AF) and mastoid fontanelle (MF) in detecting cerebellar haemorrhages (CBH) in very low birthweight (VLBW) infants.

Setting Third-level neonatal intensive care unit (NICU).

Design VLBW infants consecutively admitted at Gaslini Children’s Hospital between February 2012 and September 2013 underwent both CUS and MR susceptibility-weighted imaging (SWI). CUS was performed at days 1, 2, 3 and 7 after birth, then weekly until term-equivalent age. All CUS examinations were performed through AF and MF using an 8 Mhz convex probe. Depending on the size, CBHs were classified as massive, limited or microhaemorrhages. Diagnostic accuracy of CUS through AF and MF in detecting all types of CBHs was assessed by comparing it with SWI, used as the gold-standard technique.

Results 140 VLBW infants were included. CUS sensitivity in detecting massive CBH through both AF and MF was excellent (100%). However, CUS sensitivity through AF dropped down to 16.7% (95% CI 1% to 46%) in cases of limited CBH, with sensitivity through MF remaining good (83.3%; 95% CI 53% to 100%). None of the microhaemorrhages diagnosed by SWI was identified by CUS, despite the use of MF. Specificity of CUS in detecting all degrees of CBH through both AF and MF was excellent (100%).

Conclusions Routine use of MF allows a better detection of limited CBH when compared with AF. Overall sensitivity of CUS in detecting CBH is low when microhaemorrhages are included. In other words, microhaemorrhages proved to be undetectable by CUS.