Neurological features of pre-eclampsia and progression to eclampsia
Pre-eclampsia (new high blood pressure after 20 weeks with signs that organs or the placenta are not coping) can affect the nervous system, with headache, blurred vision and brisk reflexes.
Remember
Headache, visual disturbance (blurred vision or flashing lights) and brisk reflexes warn that pre-eclampsia affects the nervous system, whereas eclampsia means pre-eclampsia that has progressed to seizures.
Pre-eclampsia means new high blood pressure after 20 weeks of pregnancy together with proteinuria (protein in the urine), organ dysfunction (organs that are not coping) or a placenta that is not working well. Early on it usually causes no symptoms, which is why blood pressure and urine are checked at routine appointments.
Factors from the placenta injure the endothelium (the lining of blood vessels) and trigger vasospasm (tight narrowing of the vessels). This can damage the brain, kidneys and liver. When the brain is affected, the recognised neurological features include headache, visual disturbance (blurred vision or flashing lights), confusion, hyperreflexia (exaggerated reflexes) and seizures. Severe headache, visual disturbance, confusion and hyperreflexia are features of pre-eclampsia with severe features.
Hyperreflexia means exaggerated tendon reflexes, for example a very brisk knee jerk. In pre-eclampsia the reflexes can be brisk, not reduced, so checking them is part of monitoring a woman with the condition. Clonus is involuntary, rhythmic contraction and relaxation of muscle, for example at the ankle. Hyperreflexia with sustained clonus shows that the nervous system has become over-excitable, so it raises concern that eclampsia may be close, especially alongside severe headache, upper abdominal pain or vomiting.
Eclampsia is pre-eclampsia that has progressed to generalised tonic-clonic seizures. Tonic means the body stiffens and clonic means it then jerks rhythmically. The other findings, such as headache, sudden swelling of the face, hands or feet, and brisk reflexes, warn of worsening disease but do not define eclampsia.
Pain under the ribs and sudden swelling can accompany pre-eclampsia, but they do not point to the brain. Pain under the right ribs reflects the liver, not the brain. Sudden swelling of the face, hands or feet comes from fluid shifting out of the blood vessels, so it does not point to the brain.
Key facts
- Neurological features
- headache, visual disturbance, confusion, hyperreflexia and seizures are recognised neurological features of pre-eclampsia.
- Reflex direction
- reflexes can be exaggerated in pre-eclampsia, not reduced.
- Clonus
- hyperreflexia with sustained clonus shows that the nervous system has become over-excitable.
- Eclampsia
- pre-eclampsia that has progressed to generalised tonic-clonic seizures.
- Liver sign
- pain under the right ribs reflects the liver, not the brain.
- Treatment
- magnesium sulfate (a drug given by drip to prevent seizures) is the drug of choice to treat eclampsia and to prevent it in severe pre-eclampsia.
Exam traps
- Reduced or absent reflexes run the opposite way to pre-eclampsia, where the reflexes can be brisk and examination looks for hyperreflexia, so they would suggest a different problem.
- A persistent headache is a warning that pre-eclampsia may be severe, but it can occur without any progression, so headache alone does not establish eclampsia.
- Brisk reflexes can be an early sign of severe pre-eclampsia and reflect an irritable nervous system, but they do not equal an established seizure, so they do not establish eclampsia.
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