[Neurological manifestations of leprosy]

Leprosy, also known as Hansen's disease, is a chronic, infectious disease caused by Mycobacterium leprae. Bacilli localize preferentially in the skin and peripheral nerves and have a propensity to cause nerve damage. The resulting disability has caused great suffering for victims in many countries. Despite recent advances in the immunopathogenesis, epidemiology and prognostic factors of leprosy nerve damage, many aspects of the disease have remained enigmatic. The spectrum of clinical and pathological manifestations of the disease ranges from lepromatous to tuberculoid, depending on the host's T-cell-mediated immune response. Diagnosis is based on three criteria: characteristic skin lesions in association with thickened nerves, demonstration of acid fast bacilli in slit skin smears, and histopathology of skin biopsies. Nerve biopsy is necessary to establish the diagnosis of pure "neural leprosy". In developed countries, the diagnosis is suspected when a patient who has stayed in an endemic area suffers from a peripheral neuropathy of unknown etiology. To facilitate determination of the appropriate antibiotic regimen, patients are classified as either paucibacillary or multibacillary. Some patients may have multibacillary leprosy in nerves and paucibacillary leprosy in skin, which emphasizes the usefulness of nerve biopsy. The course of the disease is often complicated by immune mediated "reactions", which can rapidly lead to further nerve damage, namely reversal reaction and erythema nodosum leprosy. However, nerves are often functionally impaired before developing obvious symptoms such as skin reactions or nevralgia (silent neuropathy). Early recognition and prompt treatment with corticosteroids of leprous reactions and "silent neuropathies" is very important to prevent disability with all its attendant problems. Research progress from clinical trials may improve current methods of prevention and treatment of nerve damage in leprosy.