HTLV-1-associated myelopathy (aka tropical spastic paraparesis) is primarily seen in Japan, Melanesia and the Caribbean and presents with chronic spastic paraparesis.
This condition has been independently described in Japan (HTLV-1 associated myelopathy) and in the Caribbean (tropical spastic paraparesis), and it is now often referred to by both terms, i.e. HTLV-1-associated myelopathy/tropical spastic paraparesis) 1.
HTLV-1 is only present in some parts of the world, endemic in Japan, and also found in the Caribbean, some parts of Africa and Melanesia 1. It is transmitted by blood (transfusion, IVDU) and other bodily fluids (breast feeding, sexual intercourse) 1.
The most common neurological manifestation of HTLV-1 associated myelopathy is a slowly progressing chronic spastic paraparesis, although a preceding episode of acute deterioration is reported in a minority of patients 1. As such it is felt that there are two phases; an early acute inflammatory phase and a second chronic phase 1.
In addition of myelopathy, HTLV-1 can result in adult T-cell leukemia, uveitis and arthropathy 1.
It is believed that HTLV-1 associated myelopathy is the result of a multifactorial immune / autoimmune response to infection with the HTLV-1 virus 1. This results in axonal and myelin loss in the cord, particularly in the anterior and lateral columns, although the entire cord (including grey matter) demonstrates infiltration with lymphocytes and macrophages 1.
MRI is the modality of choice to evaluate both cranial and spinal cord manifestations.
The most common imaging feature of HTLV-1 associated myelopathy is cord atrophy and increased signal, seen in three quarters of affected individuals 2. During the acute exacerbation, reported in a minority of patients, the cord is swollen and of high T2 signal with peripheral contrast enhancement 1.
Although the cord manifestations are the best known features of over half of affected individuals will also demonstrate high T2 signal in the cerebral white matter 2.
Treatment and prognosis
The mainstay of treatment is immune modulation. In the acute setting corticosteroid therapy may be useful in controlling cord swelling 1.
The differential diagnosis depends upon the phase of the disease.
In the acute phase the main differentials include:
In the more common chronic phase the differential includes:
- vacuolar myelopathy (HIV): typically posterior and lateral columns 1
- relapsing-remitting myelopathy (associated with anticardiolipin antibodies)