Case report Monophasic, solitary tumefactive demyelinating lesion: neuroimaging features and neuropathological diagnosis 1 H M TAN, FRCR, 1 L L CHAN, FRCR, 2 K L CHUAH, FRCPA, 2 N S S GOH, MBBS (Singapore) and 3 K K TANG, FRCS Departments of 1 Diagnostic Radiology, 2 Pathology and 3 Neurosurgery, Singapore General Hospital, Outram Road, Singapore 168609 Abstract. The characteristic clinicoradiological findings of multiple sclerosis and acute disseminated encephalomyelitis (ADEM), demonstrating a recurrent progressive course in the former and monophasicity in the latter associated with multiple discrete white matter lesions with variable enhancement on MRI, are not a diagnostic challenge. On the other hand, the less typical radiological presentation of a solitary tumefactive demyelinating lesion mimics a neoplasm, and often necessitates a biopsy. Nonetheless, histopathological examination is an imperfect gold standard and the recognition of certain imaging features may facilitate the correct diagnosis. The spectrum of primary demyelinating diseases, of which multiple sclerosis is most common, is often made on clinical grounds. Histological confirmation is uncommon except when atypical clinical or radiological features are present. Tumefactive demyelination, as the name implies, poses a diagnostic challenge as it simulates a neoplasm on imaging, and especially so in a clinically monophasic and solitary lesion [1]. We highlight in our report how radio- logical features aided in the diagnosis of a case of acute tumefactive demyelination, and discuss potential histo- pathological pitfalls of demyelinating lesions. Case report A previously well 30-year-old right-handed Chinese male factory worker presented with subacute onset of right-sided weakness and numbness over 6 week’s dura- tion. Neurological examination confirmed a mild right hemiparesis and neuropsychological examination further revealed a clinical tetrad of right–left disorientation, finger agnosia, agraphia and acalculia, constituting Gerstmann’s syndrome. There was no language disturbance, or history of preceding viral prodrome or immunization. A CT scan of the brain showed a hypodense lesion without significant enhancement or mass effect in the superior left parietal subcortical white matter (Figure 1). MRI revealed a 3 cm rounded, well-defined T 1 hypointense, T 2 hyperintense mass with an incomplete rim of enhancement in the post- contrast scans (Figure 2). No other similar mass lesion or focal signal change was visualized. There was no encroach- ment into the grey matter. Given the large size of the mass, it was observed that the accompanying oedema was disproportionately mild. Despite its mass-like appearance, the rim enhancement and relative little perilesional oedema were thought to favour a demyelinating lesion over a low grade glioma. Progressive multifocal leucoencephalopathy (PML) was unlikely as the patient was not immunocom- promised. HIV serology was also negative. Other negative blood test results included absent autoimmune markers and normal erythrocyte sedimentation rate (ESR) value. Despite the radiological features favouring a tumefactive demyelinating lesion, both the patient and the surgeon favoured stereotactic biopsy for the purpose of obtaining a histological confirmation. The choice of MR spectroscopy was also offered to the patient at this juncture but he opted for biopsy as he felt that histological confirmation would be definitive. The pre-biopsy surgical planning contrast-enhanced MRI scan was performed 8 days later. Interval increase in rim enhancement was noted in this scan (Figure 3). The patient underwent uneventful stereo- tactic biopsy of the mass. The lesion was reported to be an astrocytoma on histology. However, the patient declined surgery. Received 17 June 2002 and in revised form 29 April 2003, accepted 19 May 2003. Figure 1. Contrast-enhanced CT reveals a hypodense lesion in the left parietal subcortical white matter, showing no significant mass effect or enhancement. The British Journal of Radiology, 77 (2004), 153–156 E 2004 The British Institute of Radiology DOI: 10.1259/bjr/26682607 153 The British Journal of Radiology, February 2004
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