What are the potential causes of diplopia (double vision) in a postpartum patient with a history of eclampsia and controlled blood pressure?

Diplopia in Postpartum Eclampsia with Controlled Blood Pressure

In a postpartum patient with eclampsia history presenting with diplopia despite controlled blood pressure, the most likely cause is posterior reversible encephalopathy syndrome (PRES), which represents the neuroradiological manifestation of cerebral involvement in eclampsia and can occur even when blood pressure appears adequately controlled. 1

Primary Pathophysiologic Mechanism

The development of visual disturbances, including diplopia, in postpartum eclampsia stems from cerebral endothelial dysfunction and vasogenic edema affecting the posterior circulation, regardless of current blood pressure readings. 1, 2

• PRES was identified in 86.7% of eclampsia patients and represents the underlying cerebral pathology causing visual symptoms 1
• The syndrome can manifest even with relatively modest blood pressure elevations, as cerebral involvement depends more on the rapidity of blood pressure changes than absolute values 1
• Importantly, PRES has been documented in 20-26% of severe preeclampsia patients who were neurologically asymptomatic, indicating that cerebral involvement can be subclinical 1

Specific Visual Manifestations in Eclampsia

Visual disturbances in postpartum eclampsia include several distinct entities beyond simple diplopia:

• Cortical blindness from occipital lobe involvement in PRES 3, 2
• Diplopia (double vision) from cranial nerve involvement or brainstem edema 2
• Scotomata and photopsia from retinal or cortical dysfunction 2
• Serous retinal detachment and retinal hemorrhages 2
• Homonymous hemianopsia from posterior cerebral involvement 2

Critical Timing Considerations

Postpartum eclampsia typically presents 3-10 days after delivery (median: 5 days), with visual symptoms being a common prodromal feature. 4

• Over half (55%) of postpartum eclampsia cases had no antepartum preeclampsia diagnosis 4
• Visual changes and headache are among the most common prodromal symptoms before seizures occur 4
• All patients who seized had prodromal symptoms, making recognition of visual disturbances critical for seizure prevention 4

Immediate Management Approach

Despite controlled blood pressure, the presence of diplopia mandates urgent evaluation and treatment:

1. Continue magnesium sulfate for 24 hours postpartum as recommended for eclampsia prophylaxis, as this remains the standard despite some debate about duration 5

2. Maintain blood pressure control with target <160/110 mm Hg using oral nifedipine or intravenous labetalol/hydralazine 5

   • Note that not all postpartum eclampsia patients present with severely elevated blood pressure; only 3 of 19 women in one series had diastolic BP ≥110 mm Hg 4

3. Obtain urgent neuroimaging (MRI brain preferred) within 48 hours to identify PRES and assess extent of cerebral involvement 1

   • MRI is superior to CT for detecting vasogenic edema patterns characteristic of PRES 1

4. Monitor neurological status closely as eclampsia may occur postpartum even with controlled blood pressure 5

Important Clinical Pitfalls

The most critical error is assuming that controlled blood pressure excludes serious cerebral pathology. 1

• PRES can develop with shorter durations of hypertension and does not require sustained severe hypertension 1
• Visual symptoms represent severe preeclampsia features and warrant aggressive management regardless of current blood pressure readings 2, 4
• Avoid NSAIDs for pain management in this setting, as they can exacerbate hypertension and worsen cerebral perfusion 5

Prognosis and Follow-up

Most visual disturbances from eclampsia-related PRES resolve within weeks to months, though permanent visual impairment rarely occurs. 2

• Treatment focused on PRES recognition induces early reversibility and prevents long-term neurological sequelae 1
• Beyond magnesium sulfate and blood pressure control, no specific therapy is typically required 2
• All laboratory abnormalities (platelets, creatinine, liver enzymes) should be monitored daily until stable 5

Postpartum Monitoring Protocol

• Monitor blood pressure at least 4-6 hourly for minimum 3 days postpartum 5
• Continue neurological assessments as eclampsia can occur de novo in the postpartum period 5
• Review within 1 week if requiring antihypertensives at discharge 5
• All women require 3-month postpartum follow-up to ensure normalization of blood pressure, urinalysis, and laboratory tests 5