Estimation of Intracranial Pressure by Ultrasound of the Optic Nerve Sheath in an Animal Model of Intracranial Hypertension

Abstract

Background: Invasive monitoring of intracranial pressure (ICP) is currently the gold standard method for the safe diagnosis and treatment of intracranial hypertension (ICHy), but it is subject to hemorrhage, infection and malfunction. Ultrasound of the optic nerve sheath diameter (ONSD) has been applied as a non-invasive alternative that is cost effective and available at the bedside. However, ONSD time-lapse behavior in a set of ICHy and its relief by means of whether saline infusion or surgery is still unknown. The objective of this study was to correlate intracranial pressure and ultrasonography of the optic nerve sheath in an experimental animal model of ICHy, and the interval needed to ONSD to return to its baseline levels.Methods: An experimental study was conducted on 30 male and female pigs weighing about 20 kg. The diameter of the optic nerve sheath was evaluated by ultrasound at different measures of ICP given by intraventricular catheter and intracranial balloon inflation, saline infusion and balloon deflation. Laboratory and hemodynamic data were collected from the animals. ICP and ONSD values were correlated at each time point of the study.Results: All the variables obtained by ONSD ultrasonography as left optic nerve, right optic nerve and average of optic nerve sheath (AON) diameter were statistically significant to estimate ICP value. ONSD values changed immediately at balloon inflation, with a delay of 30 minutes average to return to baseline levels after balloon deflation (p = 0.016). No statistical significance was observed in ICP and ONSD values with hypertonic saline infusion. Correlation between ICP and ONSD was linear and can be estimated using the formula: -80.5 + 238.2 x AON, in this swine model. Conclusion: In the present study, ultrasound of optic nerve sheath diameter disclosed linear correlation with ICP, although a short delay in returning to its baseline levels may be observed in the case of sudden intracranial hypertension relief.

Animal models for the study of intracranial hematomas (Review)

“…Regarding the animals used for modeling ICH, the following different species were used: Mice or rats (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33), pigs (34)(35)(36)(37)(38)(39)(40), dogs (41)(42)(43), monkeys (44), sheep (45), cats (46) and rabbits (47,48). The majority of studies (63%) utilized rats, whereas the model most used is autologous blood intracranial injection (51%).…”

“…Studies for ultrasound assessment of the optic nerve sheath diameter (34,94) and transcranial Doppler pulsatility index (35) have taken advantage of this method because of sudden IHT development. Thus, the balloon model appears to be sufficient for generating oscillations in intracranial pressure measurements as well as for causing an impact on cerebral hemodynamic conditions and valuable for studying the effects of mechanical damage to the brain tissue (43).…”

Avaliação da solução salina hipertônica a 20% e manitol sobre a pressão intracraniana avaliada por método invasivo e não invasivo em modelo animal suíno de hipertensão intracraniana

“…e por métodos não invasivos, tendo destaque recente a medida ultrassonográfica da bainha do nervo óptico (USBNO) [2][3][4][5][6][7] .…”

“…O aumento da pressão intracraniana leva a um aumento do LCR na bainha do nervo óptico com aumento de suas dimensões. Estudos demonstraram que o local de maior distensibilidade da bainha do nervo óptico é na sua porção intraorbitária que se encontra, aproximadamente, de 3-5mm da papila em humanos (Figura 7).Diversos estudos relacionaram uma forte associação entre o aumento da PIC e a distensão da bainha do nervo óptico2,3,7, . Existem poucos estudos sobre o USBNO em modelos experimentais animais de hipertensão intracraniana5,84,85 .…”