EDITORIAL 20 SA JOURNAL OF RADIOLOGY • March 2010 MRI findings and diagnosis Cranial MRI: findings and diagnosis QUIZ CASE S K Misser, MB ChB, FCRad (D) Lake Smit and Partners, Durban Please refer to page 105 of the December 2009 issue of the SAJR (http:// www.sajr.org.za/index.php/sajr/article/view/395/310) for the clinical details and images. We congratulate Dr N Maharaj, who is a radiology registrar at King Edward VIII Hospital, Durban, for the precise and winning diagnosis, for which she receives an award of R1 000 from the RSSA. Dr Misser elaborates below on the causative condition. Diagnosis T2-weighted (Figs 1a and 1b) and FLAIR (Fig. 1c) sequences demon- strate bilateral paramedian thalamic and parieto-occipital subcortical hyper-intensity. Bilateral superior parietal gyral swelling is shown on the T1-weighted axial image (Fig. 2a). Nodular lepto-meningeal and peri- vascular post-gadolinium enhancement is seen in Figs 2b and 2c. In a patient with known colonic carcinoma, on chemotherapy, the most likely cause for abnormalities in such a distribution is chemotherapy-related posterior reversible encephalopathy syndrome (PRES). PRES, as described in 1996 by Hinchey et al.,1 is a clinico-radio- logical syndrome characterised by reversible symmetrical subcortical vasogenic oedema with a predilection for posterior cerebral arterial ter- ritories and watershed zones. In addition to the parietal lobes, the basal ganglia, thalami, brain-stem and cerebellum may be involved.1 There is classically absence of restricted diffusion in these affected areas, and patchy nodular pial enhancement is occasionally seen (as in the patient reported). Causes include hypertensive encephalopathy, eclampsia, com- bination chemotherapy, renal failure and septic shock. Despite several theories, the pathogenesis of vasogenic oedema in PRES is not clear.2 Relative paucity of sympathetic innervation of the ver- tebrobasilar circulation when compared with the internal carotid territo- ries has been suggested as an explanation for the distribution frequently observed. Chemotherapeutic and immunosuppressive agents are known to increase porosity of the blood-brain barrier as well as to elevate intra- vascular pressure. P-glycoprotein expression in the blood-brain barrier is also affected in patients with brain metastases. Hypomagnesaemia, a consequence of some platinum-containing chemotherapeutic agents and eclampsia, has also been implicated in increasing blood-brain barrier permeability. 1. Hinchey J, Chaves C, Appignani B, et al. A reversible posterior leukoencephalopathy syndrome. N Engl J Med 1996; 334: 494-500. 2. Bartynski WS. Posterior reversible encephalopathy syndrome, part 2: Controversies surrounding patho- physiology of vasogenic edema. Am J Neuroradiol 2008; 29: 1043-1049. Quiz Case.indd 20 2/26/10 9:50:03 AM