Sonographic Optic Nerve Sheath Diameter Following Seizure Prophylaxis in Pre-Eclamptic Parturients With Severe Features: A Prospective, Observational Study

OBJECTIVES

Neurological manifestations, including raised intracranial pressures, are a hallmark of worsening pre-eclampsia. Invasive methods for measuring intracranial pressure, though a gold standard, are not always a viable option. Maternal ocular sonography is a promising bedside tool, which serves as a noninvasive, cost-effective means for measuring optic nerve sheath diameter (ONSD), a surrogate marker of raised intracranial pressures. We studied the ultrasonographically measured ONSD in severely pre-eclamptic women, and the effect of magnesium sulfate therapy on its values.

METHODS

Thirty severely pre-eclamptic women at ≥28 weeks gestation were included. We recorded baseline ONSD values, serum magnesium levels, neurological symptoms, vitals, and repeated them at 4 and 12 hours following magnesium sulfate therapy, and then at 24 hours postpartum. An ONSD value >5.8 mm was suggestive of raised intracranial pressure. Primary outcome measure was to evaluate changes in ultrasonographically measured ONSD following seizure prophylaxis with magnesium sulfate.

RESULTS

Women, 73.3%, had baseline ONSD >5.8 mm, with mean diameter being significantly high (6.02 ± 0.77 mm). There was a statistically nonsignificant decline in mean ONSD values at 4 and 12 hours, as well as at 24 hours postpartum. Patients with neurological symptoms declined significantly (from 70 to 10%; p value <.001) following magnesium sulfate therapy.

CONCLUSIONS

Majority of severely pre-eclamptic parturients had high ONSD value suggestive of raised intracranial pressures, which persisted in the postpartum period and was unaffected by magnesium sulfate therapy. Ultrasound can thus serve as a point-of-care, cost-effective, easily available bedside tool for indirectly measuring intracranial pressures in this high-risk population.