Acute demyelinating lesions with restricted diffusion in multiple sclerosis

Abstract

Background and objectives It is widely accepted that typical acute demyelinating lesions in relapsing–remitting multiple sclerosis (RRMS) exhibit vasogenic edema with increased diffusion, as demonstrated by an increased apparent diffusion coefficient on MRI. In contrast, acute ischemic lesions demonstrate cytotoxic edema with restricted diffusion. Recent reports have documented selected cases of acute demyelinating lesions exhibiting restricted diffusion (ADLRD) in MS. We aimed to assess the morphologies, distributions, signal characteristics and changes over time of nine ADLRD. An additional goal was to obtain clinical correlations and relate our findings to all previously published case reports describing ADLRD. Methods A retrospective case series study was performed at two academic centers. MRI characteristics of nine ADLRD found in six RRMS patients were compared with typical active symptomatic contrast-enhancing lesions with increased or normal diffusion in control RRMS patients. Results The average size of ADLRD was not significantly different from typical lesions. A periventricular location and faint signal on T2-weighted images were significantly more common for ADLRD compared with typical lesions. Two patients with ADLRD on initial MRI exhibited new ADLRD on their follow up scans. Conclusion Our results and review of prior published cases suggest that ADLRD represent a new variant of MS lesion. The restricted diffusion that is a characteristic of ADLRD on MRI is a new challenge in the differential diagnosis of stroke in young adults. The pathogenesis of ADLRD remains to be understood.

Utility of Proton MR Spectroscopy for Differentiating Typical and Atypical Primary Central Nervous System Lymphomas from Tumefactive Demyelinating Lesions

“…10,19 However, at times, an acute demyelinating lesion may also have areas of low ADC values, which makes it difficult to differentiate from tumors. 20 Cha et al 21,22 summarized the perfusion MR imaging features of brain tumors. The typical PWI feature of PCNSL is low relative CBV compared with that of high-grade gliomas and metastasis.…”

MAGNIMS consensus guidelines on the use of MRI in multiple sclerosis—clinical implementation in the diagnostic process

“…97 However, during a short and very early phase of lesion evolution (first few hours or days), transient diffusion restriction (high signal intensity on DWI and reduced apparent diffusion coefficient) has been described in some acute MS lesions. [98][99][100][101] This feature might result from an inflammatory process that leads to local hypercellularity, or from a hypoxic-ischaemic event that induces cytotoxic and vasogenic oedema. As this phenomenon only occurs in a subset of acute MS lesions, 98 DWI cannot replace contrast-enhanced T1-weighted images for differentiating between acute and chronic lesions.…”

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“…A recent study of 13 such plaques demonstrated that the majority of the lesions were symptomatic, enhancing and periventricular in location, and all of the lesions ultimately demonstrated increased ADC values on follow-up [75]. Although it is not clear why some multiple sclerosis plaques demonstrate restricted diffusion, it has been observed that glutamate is increased in the cerebrospinal fluid of patients with acute multiple sclerosis and that macrophages and microglia produce high levels of glutamate near areas of axonal damage [76,77].…”