A Demyelinating Disease; What Lies Beneath?

A 5-year-old boy presented with 1 mo history of excessive sleepiness, early morning headache and vomiting. Moreover, a 5-day history of increasing irritability was noted. Clinical examination demonstrated bradycardia, hypertension and right-side facial palsy. Subsequently, an urgent CT brain was done which revealed diffuse vasogenic cerebral edema with extensive white matter hypodensities. Such white matter changes were further defined by MRI (Fig. 1). Herpetic encephalitis and acute demyelinating encephalomyelitis were the top differential diagnoses. Accordingly, the child was given IVIG and IV acyclovir. Despite treatment, his Glasgow coma scale dropped gradually to 7 meriting intubation. The deteriorating clinical course necessitated exclusion of primary central nervous system lymphoma (PCNSL). Therefore, a stereotactic brain biopsy was executed. The pathology report was diagnostic of diffuse large B cell lymphoma (DLBCL). Further workup has unveiled spinal drop metastases. PCNSL constitutes 3 % of all brain tumors [1]. About 90–95 % of the cases are constituted by DLBCL, possibly affecting brain, spinal cord, eyes, meninges, and cranial nerves [2]. Our patient was commenced on chemotherapy protocolB LMB 89 group C^ with high dose methotrexate and whole brain irradiation [3]. He was brought into remission over the 3 y. MRI features of PCNSL in immunocompetent patients usually are non-specific; MRI shows a single lesion in 65 % of cases. Such a lesion is either homogenously isointense or hypointense to cortex on T1weighted images or hyperintense on T2-weighted images [4]. The borders of the lesion are either well defined or irregular with variable extent of surrounding edema and homogenous gadolinium enhancement [2, 4]. The lesions are frequently hyperintense on diffusion weighted imaging and hypointense on apparent diffusion coefficient maps. Such diagnostic radiologic feature is attributed to the restricted diffusion rate of unbound extracellular water molecules due to hypercellularity of PCNSL [5]. The rarity of such childhood malignancy coupled with the nonspecific presenting symptoms that could be explained by commoner benign diseases comprise a diagnostic challenge [1]. CNS malignancy is an important cause of diffuse demyelination that should be explored if the presentation of ADEM is compounded with persisting or worrisome clinical picture. Reaching such a diagnosis in a timely fashion is of crucial significance to patient’s outcome [1]. * Fatma Rabah fatmarabah@gmail.com