High frequency hearing loss

A female 36 years, gravida 3 para 2 comes with complaints of headache, loss of sight and is in labour with poor cervical dilatation progress. on admission, the BP is 178/102 with no history of convulsions and magnesium sulphate is given. A LSCS is performed under spinal anesthesia with BP stabilised. she is transferred to ICU for post operative management with BP continuing to increase . After 5 days, a feedback is given that the patient is discharged and gained her sight. What caused the loss of sight?