HTLV-1 associated myelopathy (HAM)
General description
HTLV-1 is a retrovirus infecting in CD4 positive T-cell transmitted through lactation and sexual intercourse.
The main pathogenesis of HAM is thought to be chronic inflammation of the spinal cord resulting from the increase and activation of HTLV-1-infected cells, which leads to destruction and degeneration of spinal cord tissue, forming the condition.
HAM is a disorder characterized by spastic paraplegia of both lower limbs due to damage to the lower thoracic spinal cord. Motor deficits are common, but there are also coexisting sensory, bladder-rectal disturbance, and autonomic neuropathies, and the symptoms are diverse. Ataxia, eye movement disorders, mild dementia, and Parkinson's syndrome may also be present.
Thoracic spinal cord involvement
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Spinal cordThoracic spinal cordSpinal white matterPosterior column
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Spinal cordThoracic spinal cordSpinal white matterLateral column
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Spinal cordThoracic spinal cordSpinal gray matterPosterior horn
In patients with HAM (HTLV-1-associated myelopathy), the thoracic spinal cord is typically involved. Imaging studies often reveal swellings and T2WI hyperintensity in the bilateral posterior column, lateral column, and posterior horn of the thoracic spinal cord.
Swellings and atrophy of thoracic spinal cord
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Spinal cordThoracic spinal cord
Imaging studies often reveal swelling in the thoracic spinal cord. As the disease progresses to the chronic phase, atrophy of the spinal cord becomes apparent.
Cerebral T2WI hyperintensity
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CerebrumCerebral white matter
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Internal capsulePosterior limbCorticospinal tract
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Middle cerebellar peduncle
Approximately half of the patients exhibit T2WI high signal intensity in the cerebral white matter, accompanied by analogous signal alterations in the corticospinal tract of the internal capsule and the middle cerebellar peduncle.