LETM MRI (longitudinally extensive transverse myelitis)

Detection of a LETM spinal cord lesion associated with acute myelitis is the most specific neuroimaging characteristic of NMOSD (>3 vertebral segment longitudinally extensive transverse myelitis lesions)

(LETM) in NMO

Such lesions typically involve
—the central gray matter—cord swelling, —central hypointensity on T1- weighted sequences, and —enhancement following IV gadolinium administration; —extension of a cervical lesion into the brainstem is characteristic.

LETM pattern is characteristic of NMOSD - —7%–14% of initial and 8% of subsequent myelitis attacks in AQP4-IgG-seropositive patients do not meet the LETM definition.

LETM MRI pattern may also occur in patients with
infectious,
granulomatous,
neoplastic, and
paraneoplastic diseases,
acute disseminated encephalomyelitis (ADEM),
spinal cord infarction,
and dural arteriovenous fistula