(See also Overview of Spinal Cord Disorders.)
The HTLV-1 retrovirus is transmitted via sexual contact, IV drug use, or exposure to infected blood or from mother to child via breastfeeding. It is most common among prostitutes, IV drug users, hemodialysis patients, and people from endemic areas such as equatorial regions, southern Japan, and parts of South America.
TSP/HAM affects < 2% of HTLV-1 carriers. It is more common among women; this finding is consistent with the higher prevalence of HTLV-1 infection in women. HTLV-2 may cause a similar disorder.
The virus resides in T cells in blood and cerebrospinal fluid (CSF). CD4+ memory T cells, CD8+ cytotoxic T cells, and macrophages infiltrate the perivascular areas and parenchyma of the spinal cord; astrocytosis occurs. For several years after onset of neurologic symptoms, inflammation of spinal gray and white matter progresses, causing preferential degeneration of the lateral and posterior columns. Myelin and axons in the anterior columns are also lost.
Symptoms and Signs
Diagnosis
Tropical spastic paraparesis/HTLV-1–associated myelopathy is suggested by typical neurologic deficits that are otherwise unexplained, particularly in patients with risk factors.
Serum and CSF serologic tests, PCR tests, and spinal cord MRI are indicated. If CSF-to-serum ratio of HTLV-1 antibodies is > 1 or if PCR detects HTLV-1 antigen in CSF, the diagnosis is very likely. Protein and Ig levels in CSF may also be elevated, often with oligoclonal bands; lymphocytic pleocytosis occurs in up to 50% of patients. Spinal cord lesions often appear hyperintense on T2-weighted MRI.
Treatment
Key Points
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Tropical spastic paraparesis/HTLV-1–associated myelopathy (TSP/HAM) affects < 2% of HTLV-1 carriers and occurs more commonly in women.
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Symptoms include gradually developing spastic weakness in both legs, extensor plantar responses, bilateral symmetric loss of position and vibratory sensation in the feet, and absent Achilles tendon reflexes.
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Diagnose using serum and CSF serologic tests, PCR tests, and MRI.
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Interferon alfa, IV immune globulin, and oral methylprednisolone may have some benefit; treat spasticity with baclofen or tizanidine.
