A 32-year-old pregnant woman at 28 weeks gestation presents to the prenatal clinic with complaints of severe headaches, visual disturbances, and epigastric pain. Her blood pressure is 160/110 mmHg, and urinalysis shows 3+ proteinuria. Which assessment finding would be most concerning and require immediate intervention?

Hyperreflexia with sustained clonus indicates severe CNS involvement in preeclampsia, signaling imminent risk of eclamptic seizures requiring immediate magnesium sulfate and delivery. Other findings (ankle edema, mild headache, elevated BP) are less urgent.

Clinical Context and Pathophysiology

This clinical presentation is classic for severe preeclampsia. The patient's blood pressure of 160/110 mmHg, 3+ proteinuria, severe headache, visual disturbances, and epigastric pain at 28 weeks gestation meet the diagnostic criteria for a severe feature of the disease. The underlying pathophysiology, as described in the literature, involves a common pathway of endothelial cell activation, intravascular inflammation, and syncytiotrophoblast stress ^[1]. This widespread endothelial dysfunction is responsible for the multi-organ manifestations, including central nervous system (CNS) irritability and hepatic involvement signaled by epigastric pain.

Analysis of the Most Concerning Finding

The assessment finding that demands immediate intervention is hyperreflexia with sustained clonus. This sign is a direct indicator of severe CNS irritability and is a hallmark of progression from severe preeclampsia to eclampsia. Eclampsia, the onset of generalized tonic-clonic seizures in a patient with preeclampsia, is a major source of maternal morbidity and mortality ^[4]. Sustained clonus represents a state of neuromuscular hyperexcitability that sits on the threshold of seizure activity. The pathophysiologic link is the failure of cerebral autoregulation due to endothelial damage, leading to cerebral edema and hyperperfusion, which manifests clinically as hyperreflexia and clonus. Immediate intervention, typically with magnesium sulfate for seizure prophylaxis, is critical to prevent eclamptic seizures.

Why Other Options Are Less Immediately Critical

While all findings are relevant to preeclampsia, they do not signal an imminent life-threatening event like a seizure in the same way that hyperreflexia with clonus does.

- Ankle edema and weight gain of 2 pounds in one week: This finding reflects the physiologic fluid retention and capillary leak common in preeclampsia due to endothelial dysfunction. While it indicates a worsening of the condition, it is a less specific marker of immediate CNS danger and does not require the same emergent pharmacologic intervention as impending eclampsia.
- Mild frontal headache that responds to acetaminophen: A headache that is mild and responsive to a simple analgesic is less concerning than the severe, persistent headache described in the initial presentation. The severe headache of preeclampsia is a symptom of cerebral irritation and is a severe feature of the disease. A mild, responsive headache does not carry the same immediate risk of seizure.
- Blood pressure reading of 150/95 mmHg on repeat measurement: Although this reading confirms persistent severe-range hypertension (defined as systolic BP ≥160 mmHg or diastolic BP ≥110 mmHg), and requires urgent antihypertensive therapy to prevent maternal stroke, the finding of hyperreflexia with clonus is a more direct harbinger of an eclamptic seizure. The management of severe hypertension and seizure prophylaxis are both critical and often occur simultaneously, but the assessment finding that most specifically predicts an imminent seizure is the neurologic sign of sustained clonus ^[4].