Makindo Medical Notes

Also known as Tropical Spastic Paraparesis (TSP), the disease predominantly affects the lower limbs, leading to motor and gait dysfunction.

About

• HTLV-1 Associated Myelopathy (HAM) is a slowly progressive neurological condition characterized by spastic weakness, primarily affecting individuals in the Caribbean, Africa, South America, and parts of Asia.
• HAM/TSP typically develops after a long latency period following infection with HTLV-1, and it is considered a chronic and debilitating disease.

Aetiology

• Caused by infection with the Human T-Cell Lymphotropic Virus type 1 (HTLV-1), a retrovirus that can also lead to adult T-cell leukemia/lymphoma (ATL).
• HTLV-1 transmission occurs through blood transfusions, sexual contact, breastfeeding, or sharing needles.
• Not all individuals infected with HTLV-1 will develop HAM/TSP, but factors such as genetic susceptibility and immune response are thought to play a role.

Pathophysiology

• The virus triggers chronic inflammation in the spinal cord, specifically the thoracic region, leading to degeneration of the corticospinal tracts and demyelination.
• This inflammation and demyelination results in motor neuron dysfunction, causing the characteristic spastic paraparesis.
• Immune-mediated mechanisms are implicated, with ongoing viral activity in affected tissues and an abnormal immune response contributing to the disease process.

Clinical Features

• Progressive spastic weakness that predominantly affects the lower limbs, though the upper limbs may also be involved over time.
• Patients exhibit a characteristic scissor gait due to spasticity, with difficulty walking and increased muscle tone.
• There is often brisk reflexes, including abdominal and lower limb reflexes, with clonus and Babinski signs.
• Bladder dysfunction such as urinary urgency, frequency, and incontinence is common in advanced stages.
• Some patients may also experience mild sensory changes, such as numbness or tingling in the lower extremities.
• Other neurological features, such as upper limb weakness and cognitive symptoms, are rare but can occur in severe cases.

Investigations

• HTLV-1 serology or PCR testing of blood or cerebrospinal fluid (CSF) confirms the diagnosis.
• MRI of the spinal cord is usually normal, though it may show subtle signs of cord atrophy in advanced cases.
• CSF analysis is typically normal, elevated white cells or elevated protein levels.
• Electromyography (EMG) and nerve conduction studies (NCS) rule out other causes of lower limb weakness.

Differential Diagnosis

• Cervical or thoracic cord compression: This must be excluded with imaging (MRI) to rule out causes such as disc herniation or tumour.
• Vitamin B12 deficiency: This may cause subacute combined degeneration of the spinal cord, leading to spastic paraparesis and sensory changes.
• Multiple sclerosis (MS): MS can mimic HAM/TSP with spastic paraparesis and bladder dysfunction, but MRI typically shows characteristic brain lesions in MS.
• Other infectious myelopathies: Including HIV-associated myelopathy or syphilitic myelitis, should be considered, especially in patients with risk factors.

Management

• There is no specific antiviral treatment for HAM/TSP. Focus on symptomatic relief and supportive care.
• Spasticity: Medications such as baclofen or tizanidine can help reduce muscle tone and spasticity.
• In some cases, steroids or immunosuppressive therapies (e.g., prednisone, interferon-α) and plasma exchange have been tried, but results are variable and not definitive.
• Physiotherapy is crucial to maintaining mobility, improving gait, and preventing contractures.
• Bladder management may involve anticholinergic medications (e.g., oxybutynin) and intermittent catheterization for severe bladder dysfunction.
• Progressive weakness may necessitate the use of walking aids, and in advanced cases, patients may become wheelchair-bound.
• Psychological support and multidisciplinary care involving neurologists, physiotherapists, occupational therapists, and urologists are essential for improving the quality of life.

Prognosis

• The disease is progressive, but the rate of progression can vary. Some patients may remain ambulatory for several years, while others progress rapidly to significant disability.
• Life expectancy is often normal, but the quality of life may be significantly impacted by motor, bladder, and functional decline. Cardiovascular complications, such as thromboembolic events, can occur due to immobility in later stages.