Teaching Case

A 30-year-old male patient with complaints of headache, dizziness and vomiting for one week. Blood pressure was elevated (188/106 mm of hg) at admission. Sensorium was intact with no signs of meningeal irritation/ focal neurological deficit. Ophthalmoscopy showed bilateral papilloedema s/o Grade IV hypertensive retinopathy. Cerebrospinal fluid analysis was normal.

MRI showed confluent T2/FLAIR hyperintensities in bilateral parieto-occipital and left frontal white matter, brainstem and cerebellar hemispheres with a long segment hyperintensity in the cervical spinal cord. Focal areas of restricted diffusion in bilateral parieto-occipital and left frontal region were also seen on diffusion-weighted images (Fig. 1).

In view of hypertension, the MRI findings were interpreted as atypical posterior reversible encephalopathy syndrome (PRES). Anti-hypertensive treatment with anti-hypertensives was instituted. Rapid improvement in symptoms was seen following treatment.

A repeat MRI was done one month later, which showed complete resolution of white matter hyperintensities (Fig. 2). The pattern of distribution of oedema in the brain in a patient with hypertension along with reversibility of the clinical symptoms and MR findings after anti-hypertensive treatment confirmed a diagnosis of PRES-SCI. The patient was discharged on oral anti-hypertensives and was completely asymptomatic at three month follow-up.

Background
Posterior reversible encephalopathy syndrome (or PRES) was first described in 1996 by Hinchey et al [1] and is characterised by reversible symmetrical vasogenic white matter oedema with acute onset headache, seizures and visual disturbances. It classically occurs in patients of hypertension, pre-eclampsia and eclampsia but has also been reported in patients on immunosuppressive medications, with autoimmune disease and other risk factors.
The most frequently described mechanism of PRES is due to failure of autoregulation of the cerebral vasculature in extreme hypertension. The vertebrobasilar system is especially sensitive to these sudden changes in blood pressure due lack of autonomic supply.
In addition to involvement of the parieto-occipital, other regions like the frontal lobe and temporal lobe are also frequently involved. Bartynski and Boardman described three major patterns of PRES in the cerebrum- dominant parieto-occipital, holohemispheric watershed and superior frontal sulcus pattern [2].
Unusual locations of involvement in PRES include the basal ganglia, cerebellum, splenium and brainstem. Asymmetry, unilaterality, contrast-enhancement, diffusion restriction, haemorrhages and irreversibility on MRI are also atypical imaging findings [3].
Imaging Perspective
PRES with SCI is a new entity first proposed in 2014 by Havenon et al [4] in a case series of eight patients with severe acute hypertension and confluent expansile central T2 hyperintensity spanning at least four spinal segments originating at the cervicomedullary junction. Seven out of eight patients had hypertensive retinopathy and showed resolution of spinal cord lesions and favourable clinical course with only anti-hypertensive treatment.
Although, the anterior spinal artery arises from the posterior circulation, the cervical cord is infrequently affected in PRES due to dense sympathetic innervations of these vessels leading to effective autoregulation. As a result, PRES-SCI is rarer and is almost always associated with a more severe degree of hypertension.
Outcome
PRES requires quick, aggressive and early institution of blood pressure control. Any delay in reduction of blood pressure may result in progression of the vasogenic oedema to cytotoxic oedema and infarction, because of the exquisite sensitivity of the cortex to impaired blood flow.
Teaching Points
Spinal cord involvement in PRES is an uncommon entity seen in young males with acute severe hypertension, who clinically present with headache, vomiting and hypertensive retinopathy. Recognition of this imaging pattern could differentiate it from other imaging mimics, and lead to early institution of antihypertensive therapy preventing long term sequelae of this potentially reversible illness.

Written informed patient consent for publication has been obtained.