Differential Diagnosis of Longitudinally Extensive Transverse Myelitis in Adults

Introduction

Transverse myelitis (TM), characterized by focal spinal cord inflammation, may be caused by a wide variety of disorders. Features of TM are related to spinal cord dysfunction and include motor, sensory, and/or autonomic deficits.1 Longitudinally extensive transverse myelitis (LETM) is a relatively recent term designating a TM that extends three or more vertebral segments in length. These lesions, which may occasionally span the entire length of the spinal cord, are much rarer and in general associated with greater morbidity than the typical lesions of idiopathic TM or multiple sclerosis (MS)- associated TM. Acute complete TM (characteristic of idiopathic TM) is generally regarded as an idiopathic moderate-to-severe inflammatory disorder of the spinal cord that results in symmetric cord dysfunction below a specific level of cord function.2 Acute complete TM typically extends two or less vertebral segments in length and is associated with a low risk for future conversion to clinically definite MS.3 Acute partial/incomplete TM (characteristic of MS-associated TM) also typically extends two or less vertebral segments in length, but unlike complete TM is associated with asymmetrical (or mild) cord dysfunction. Acute partial TM often produces patchy sensory impairment, with mild-to-moderatemotor weakness and occasional bladder dysfunction. Acute partial TM is associated with a higher risk for future conversion to clinically definite MS.2 Although complete TM is typical of idiopathic TM and partial TM is typical of MS-related TM, these associations are not exclusive and a wide variety of disorders may cause them.

Abstract

Longitudinally extensive transverse myelitis (LETM), characterized by spinal cord inflammation extending three or more vertebral segments in length, may be caused by a multitude of disorders. LETM is most commonly associated with neuromyelitis optica (NMO). Such is the frequent association between these two entities that there is a growing tendency amongst physicians to regard them as being practically synonymous with each other. The objective of this review is to highlight the wide range of disorders that may cause LETM and to emphasize the need to carefully consider all potential etiologies in the assessment of LETM. In particular, we focus on the salient clinical, laboratory, and radiographic features of these various disorders, which help them to be differentiated from one another.

Keywords

Longitudinally Extensive Transverse Myelitis, LETM, NMO, neuromyelitis optica, myelopathy