Achieving optimum intracranial pressure is a core concept in neurosurgical disease. Transbulbar sonography is yet to gain wide application in surgeries for primary neurosurgical disease. Transbulbar sonography if well validated in this group of patients can sooner or later replace or corroborate other methods of intracranial pressure measurement. In this context the impact of intracranial procedures on measurements of optic nerve sheath by sonograpy pre and post-operatively attains relevance. 

As transbulbar ONSD measurement by sonography is gaining much impetus, the fallacies of this technique, if any, in primary neurosurgical disease need to be clearly defined. Till date no studies have compared the application of transbular sonography in primary neurosurgical procedures. Neurosurgical procedures are associated fluctuations in ICP due to various reasons apart from patient surgical position. This together with the inherent CSF loss through dural incisions, use of external ventricular drains or external lumbar CSF drains can further alter CSF flow dynamics. These changes can also affect the CSF flow over the optic nerve sheath. This can be non-invasively measured by transbulbar sonography. Till date no published studies have analysed the effect of open neurosurgical procedures on CSF flow dynamics measured by ultrasonic optic nerve sheath assessment.

·         We aim to evaluate the Optic Nerve Sheath Diameter (ONSD) by ultrasonography in neurosurgical patients; undergoing craniotomy (elective and emergency) in varied surgical positions; preoperatively after induction of general anaesthesia and postoperatively before reversal of neuromuscular blokade.