Posterior Reversible Encephalopathy Syndrome Related to Severe Hypomagnesaemia

Posterior reversible encephalopathy syndrome (PRES) might be associated with a wide spectrum of symptoms, including irreversible neurological damage. Management is primarily symptomatic and focuses on addressing the underlying causes.

A 65-year-old female with a medical history of smoking, arterial hypertension and dyslipidaemia, was admitted due to dysarthria associated with ataxia, visual disturbances and diarrhoea. The neurological physical examination revealed a mild decreased strength in both legs (4/5), mild dysdiadochokinaesia and mild heel-knee dysmetria. Remarkable laboratory findings showed potassium 2.6 mmol/l and magnesium 0.24 mg/dl. Brain computed tomography (CT) showed no suggestive ischaemic areas. During hospitalisation, potassium and magnesium levels were initially corrected through intravenous supplementation. A brain magnetic resonance imaging (MRI) scan revealed symmetrical cortical alterations in the posterior regions of both cerebellar hemispheres, consistent with a diagnosis of PRES. After the exclusion of other potentially related diseases, the final diagnosis was PRES in the setting of severe hypomagnesaemia.

PRES pathophysiology is unknown, while its incidence is probably underestimated. It is suggested that rapid increases in blood pressure are thought to overwhelm the self-regulatory capability of cerebral blood flow, especially in the posterior brain regions where the regulatory flow capacity may be weaker. This might result in increased cerebral perfusion leading to oedema due to capillary leakage. PRES has been associated with poorly controlled arterial hypertension, autoimmune diseases, eclampsia and chemotherapy, among others.

Hypomagnesaemia represents an uncommon but potentially reversible cause of PRES and should be taken into account for differential diagnosis.

Chronic drug therapies should always be included in the medical approach.The most common aetiology of posterior reversible encephalopathy syndrome is arterial hypertension with poor control and the use of cytotoxic drugs. However, other less common causes, such as severe hypomagnesaemia, should be taken into account.The diagnosis of posterior reversible encephalopathy syndrome is based on neuroimaging findings in the correct clinical setting. Therapy is mainly symptomatic and focuses on the underlying causes.