Assessment of optic nerve sheath diameter measured by bedside sonography as a predictor of raised intracranial pressure in adults.

1. Various studies have investigated Optic nerve sheath diameter (ONSD) as a marker for elevated intracranial pressure (ICP) and have found good correlation between the two. Further, ONSD diameter as measured by bedside ultrasonography, has been found to be well correlated with that measured with the help of MRI images.
2. To the best of our knowledge, there is paucity of Indian studies which show correlation between the ONSD values as measured by ultrasonography and the signs of raised ICP on neuroimaging modalities (CT/MRI scans).

AIMS & OBJECTIVES

1. To determine the normal optic nerve sheath diameter measured by bedside ultrasonography in the Indian population
2. To study the correlation of optic nerve sheath diameter measured by bedside ultrasonography and the features of raised intracranial pressure on neuroimaging.
3. To determine optimal cut off point of optic nerve sheath diameter to detect raised intracranial pressure

METHODOLOGY

Linear ultrasound probe will be used to measure the ONSD as the outer limits of the 2 hyperechoic lines, using electronic callipers, 3mm behind the papilla.

ONSD cut-off of 5mm will be used to define the presence of intracranial hypertension.

Patients with any one of the following findings on neuroimaging will be considered to have raised intracranial pressure-

1. Midline shift > 3mm
2. Sulcal effacement with significant oedema
3. Compression of third ventricle
4. Hydrocephalus