Detection of raised intracranial pressure by ultrasound measurement of optic nerve sheath diameter in African children

To evaluate optic nerve sheath (ONS) ultrasound as a non-invasive method of detecting raised intracranial pressure (ICP) and to establish normal ONS diameter data for African children. Children with acute neurological disease admitted to the Paediatric Department of Queen Elizabeth Central Hospital, Malawi had ultrasound measurements of ONS diameter. Controls were children admitted to the same department with non-neurological disease. The mean of three measurements of the ONS diameter was used for analysis. Children were assessed for clinical signs of raised ICP. Patients had CT brain scans if required for their normal clinical care. In 14 children with neurological disease and clinical signs suggestive of raised ICP, the mean ONS diameter was 5.4 mm (range 4.3-6.2 mm). Radiological signs on CT scans substantiated the presence of raised ICP in eight (all those scanned). In seven children with neurological disease but no specific signs of raised ICP the mean ONS diameter was 3.6 mm (range 2.8-4.4 mm). None of four of these patients examined by CT scan had signs of elevated ICP. The mean ONS diameter in 30 controls without neurological disease was 3.5 mm (range 2.5-4.1 mm). If 4.2 mm is taken as the upper limit of normal the sensitivity and specificity of this test for elevated ICP is 100% and 86%, respectively. ONS ultrasound is an accurate method for detecting raised ICP that can be applied in a broad range of settings. It has the advantages of being a non-invasive, bedside test, which can be repeated multiple times for re-evaluation.