Led astray: MELAS initially misdiagnosed as herpes simplex encephalitis.

Abstract

Mitochondrial encephalopathy, lactic acidosis and strokelike episodes (MELAS) is characterised by severe headaches, stroke-like episodes, short stature, sensorineural deafness, cognitive decline and exercise intolerance in most cases [1]. Less commonly, features such as hypertrophic cardiomyopathy, ataxia, ophthalmoplegia and diabetes mellitus may develop [1]. MELAS presenting with the features of herpes simplex encephalitis (HSE) is rare, having been described in only few case reports, and can therefore pose diagnostic challenges. We report a case whereby MELAS was eventually diagnosed in a patient who initially presented with clinical and radiological features suggestive of HSE. The 3243 A?G mutation was found in blood. A 29-year-old left-handed gentleman with type 2 diabetes mellitus, presented with a gradual onset of confusion, headaches, irritability, and personality change of a few days’ duration, followed by three tonic–clonic seizures. His initial assessment revealed a temperature of 39 C and a Glasgow Coma Scale (GCS) of 3/15, following the administration of intravenous diazepam to control his seizures in the ambulance. Serum white cell count (WCC) was raised at 26.50 9 10/L and C-reactive protein was 56 mg/L. Computed tomography (CT) of the brain showed swelling of the parenchyma of the right temporal and parietal lobes (Fig. 1a). HSE was strongly suspected and intravenous aciclovir was started. Cerebrospinal fluid (CSF) showed WCC of 1 9 10/L and protein of 0.62 g/L. Magnetic resonance imaging (MRI) showed involvement of the right temporo-parietal region, the right insular cortex and at the pole of the left temporal lobe on T2 and fluidattenuated inversion recovery (FLAIR) images (Fig. 1b–d). However, although there was corresponding restriction on diffusion-weighted imaging (DWI), there was also high signal on apparent diffusion coefficient (ADC) images suggesting that this was more likely to be vasogenic oedema. Diffusion restriction was not seen throughout the entire affected regions, but involved predominantly the cortical areas. Results for viral PCR, which became available a week later, were however negative. The diagnosis was unclear at this point and, as well as a false negative result, autoimmune encephalitis was considered. Vasculitis screening, anti-voltage-gated potassium antibodies (abs) and anti-NMDA abs were negative. He was discharged after 2 weeks in hospital, having made a good recovery with residual hearing loss ipsilateral to the temporal lobe changes. Approximately 6 months after discharge, he re-presented with expressive dysphasia. A CT scan showed an area of low attenuation in the left temporal lobe (Fig. 2a). MRI FLAIR now showed changes with abnormalities in the left temporal, parietal and occipital regions with involvement of the left insular cortex, suggestive of ischaemia in the left posterior circulation. However, the abnormal region again corresponded with diffusion restriction on DWI and high signal on ADC images (Fig. 2b–d). Generalised atrophy of the brain was also obvious at that point. A repeat LP showed no white cells and protein was raised at 0.93 g/L. Anti-nuclear abs, antineutrophil cytoplasmic abs and anti-neuronal (including anti-Hu, anti-Yo, anti-Ri, anti-Ma2 and anti-CV2/CRMP5) abs were all negative. Serum lactate was raised at 3.5 mmol/L. Given his diabetes mellitus, hearing loss, MRI R. Gooriah (&) B. E. A. Dafalla T. C. Venugopalan Neurology Department, Huddersfield Royal Infirmary, Huddersfield, UK e-mail: rubesh@doctors.org.uk