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BMJ Case Rep. 2010; 2010: bcr10.2009.2345.
Published online 2010 May 11. doi:  10.1136/bcr.10.2009.2345
PMCID: PMC3047380
Findings that shed new light on the possible pathogenesis of a disease or an adverse effect

Cerebral vasomotor reactivity monitoring in posterior reversible encephalopathy syndrome


A 25-year-old woman was admitted for vomiting, hypertension and seizures. Magnetic resonance imaging was compatible with posterior reversible encephalopathy syndrome and a transcranial Doppler/vasomotor reactivity study (TCD/VMR) demonstrated loss of vasomotor reactivity. The clinical recovery was concomitant to improvement in the TCD/VMR.


The posterior reversible encephalopathy syndrome (PRES) comprises a clinicoradiographic entity, which includes headaches, altered mentation, seizures, visual loss, and stereotypical neuroimaging findings. These are characterised by vasogenic subcortical white matter oedema, preferentially involving the posterior regions of the brain.13 Conditions classically associated with PRES include hypertensive emergencies, eclampsia, cytotoxic/immunosuppressant drugs, toxic/systemic conditions (such as sepsis or organ transplantation), acute glomerulonephritis, and dialysis.1,2,4,5 The pathophysiological mechanisms responsible for PRES are still debated.5

It is unclear as to how long the haemodynamic abnormalities last, but the clinical and radiological reversibility of PRES suggests that the vasomotor reactivity normalises with time as well. This paper reports the reversibility of the clinical features of PRES and of vasomotor reactivity, as evaluated by transcranial Doppler/vasomotor reactivity (TCD/VMR).

Case presentation

A 25-year-old African American woman was admitted after awakening with nausea, vomiting, headache and experiencing a generalised tonic-clonic seizure. She had a history of myelomeningocele, neurogenic bladder with recurrent urinary tract infections, hypertension, and end stage renal disease. Peritoneal dialysis was started 1 month earlier.

Blood pressure on admission was 170/110 mm Hg. Magnetic resonance imaging (MRI) of the brain demonstrated white matter abnormalities and an Arnold-Chiari malformation type II (fig 1). On examination, the patient was drowsy, easily arousable, with no visual deficits. She had flaccid paraparesis and abnormal lower extremity sensory examination attributed to the spina bifida/myelomeningocele.

Figure 1
Demonstration of the blood pressure measurements, vasomotor reactivity (VMR) and magnetic resonance imaging (MRI) studies during hospital stay and follow-up.


TCD examination was performed with a Pioneer TC 8080 TCD machine by Viasys Healthcare CO2 Delivery System. Firstly, a standard TCD examination was performed with the patient lying supine with eyes closed. The TCD probes were fitted in a light metal frame firmly fixed to the head with two earpieces and an adjustable nose saddle. This included a 2 min insonation of the middle cerebral arteries (MCAs) bilaterally for the determination of the baseline mean blood flow velocity (normocapnia). Secondly, for vasodilatation purposes a gas mixture of 5% carbon dioxide and 95% oxygen (carbogene) was inhaled for 2 min through a mouthpiece connected to a respiratory balloon (hypercapnia). Lastly, the patient was oriented to hyperventilate for 273 min until a plateau blood flow velocity was reached (hypocapnia).The blood pressure was concomitantly measured with an automatic device.6,7

The mean blood flow velocity (MBFV) during normocapnia was compared with those values obtained during hypercapnia and hypocapnia, and the resultant changes (in percentage) were recorded. Values [gt-or-equal, slanted]70% were considered to represent a normal vasomotor reactivity (VMR) response; 50–69% mild VMR impairment; 35–49% moderate VMR impairment; and <35% severe impairment of VMR.6,7


A nicardipine drip was started, with a goal of reducing systolic blood pressure by 25% in the first 24 h. Phosphenytoin and oral β-blocker were also prescribed. On the third day of admission, she was headache-free and her mental status normalised; subsequently a VMR study was performed. Oral extended release nifedipine was started on day 4, and the nicardipine drip was weaned off on day 8.

Outcome and follow-up

The patient recovered to baseline and was discharged home 10 days after admission.


Multiple pathophysiological mechanisms have been described according to the clinical setting where PRES takes place. In cases of hypertension, severe hypertension exceeding the limit of cerebral autoregulation leads to vasodilatation and plasma leakage into the interstitial space8; this would occur preferentially in the posterior areas of the brain due to less prominent sympathetic innervation in the vertebrobasilar system.8 In cases of eclampsia, there is an excessive vasoconstriction in response to hypertension, with endothelial injury and cytotoxic edema.1,2,5,9,10 Immunosuppressive medications are thought to exert direct cytotoxic effects on the cerebral vasculature, and dialysis seems to reduce plasma urea and/or osmotically active solutes leading to fluid shifts into brain tissue.1,11

In our case, the recent dialysis onset and the high blood pressure could have been the cause of the syndrome. Despite this uncertainty, the VMR was clearly reduced initially and was normalised by day 10 (fig 1), supporting the suggestion that angioparesis is a main feature of PRES. Regardless of the pathophysiological mechanism, TCD/VMR constituted a rapidly available, inexpensive surrogate marker of improvement.

One potential limitation of this report could be related to the effect of antihypertensive treatment on the patient’s acute presentation, which could arguably have affected the VMR. However, there is supportive evidence that rapid blood pressure normalisation within 1–2 weeks may not exhaust vasomotor reserve12; in addition, there are data to suggest that VMR may even improve with long term use of certain antihypertensives.13,14

We believe that TCD with VMR is a simple and practical method of monitoring the haemodynamic abnormalities in patients with PRES.

Learning points

  • Posterior reversible encephalopathy can occur in patients with normal blood pressure or only mild elevation.
  • Transcranial Doppler with vasomotor reactivity study can be used to evaluate the brain arteries responsiveness to chemical stimuli.
  • In our patient, the loss of vasomotor reactivity was associated with the radiological picture of PRES and its normalisation was associated with her clinical recovery.


Competing interests: None.

Patient consent: Patient/guardian consent was obtained for publication.


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