Perioperative variation in Optic Nerve Sheath Diameter measured by Transbulbar Ultrasonography in Neurological patients

Achievingoptimum intracranial pressure is a core concept in neurosurgical disease. Transbulbarsonography is yet to gain wide application in surgeries for primaryneurosurgical disease. Transbulbar sonography if well validated in this groupof patients can sooner or later replace or corroborate other methods ofintracranial pressure measurement. In this context the impact of intracranialprocedures on measurements of optic nerve sheath by sonograpy pre andpost-operatively attains relevance.

Astransbulbar ONSD measurement by sonography is gaining much impetus, thefallacies of this technique, if any, in primary neurosurgical disease need tobe clearly defined. Till date no studies have compared the application oftransbular sonography in primary neurosurgical procedures. Neurosurgicalprocedures are associated fluctuations in ICP due to various reasons apart frompatient surgical position. This together with the inherent CSF loss throughdural incisions, use of external ventricular drains or external lumbar CSFdrains can further alter CSF flow dynamics. These changes can also affect theCSF flow over the optic nerve sheath. This can be non-invasively measured bytransbulbar sonography. Till date no published studies have analysed the effectof open neurosurgical procedures on CSF flow dynamics measured by ultrasonicoptic nerve sheath assessment.

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