HTLV-1-associated myelopathy (also known as 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, Melanesia, equatorial Africa, and some parts of Central and South America with an estimated 10-40 million individuals having life-long infection 1,3,4. It is transmitted by blood (transfusion, IVDU) and other bodily fluids (breast feeding, sexual intercourse) 1,4. Despite its prevalence, only a small fraction of individuals who are infected ever manifest HTLV-1 related pathology 3.
The most common neurological manifestation of HTLV-1 associated myelopathy is a slowly progressing chronic spastic paraparesis with bowel and bladder dysfunction and lower limb sensory disturbance 1,4. 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, myositis, alveolitis and arthropathy 1,3.
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. This is most pronounced in the lateral columns, mostly involving white matter, but also involving nearby grey matter and anterior nerve roots.
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
No accepted treatment has been shown to alter the disease outcome. Mainstay of treatment is immune modulation including steroids, plasmapheresis, danazol, pentoxifylline and interferon 1,4.
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:
- HIV vacuolar myelopathy: typically posterior and lateral columns 1,4
- relapsing-remitting myelopathy (associated with anticardiolipin antibodies)
- hereditary spastic paraplegia
- multiple sclerosis
- primary lateral sclerosis
- Lyme disease
- subacute combined degeneration of the cord (usually confined to the dorsal columns)