Bacterial and parasitic neuropathies
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Borrelia Burgdorferi (Lyme disease) Clinical syndrome/ signs
The earliest stage of Lyme disease (stage I) is characterized by the unique skin rash and symptoms of general infection. Neuroborreliosis begins in stage II of the disease.
In stage II disease, the most common occurrence is lymphocytic meningoradi-culitis. Motor and sensory symptoms may occur variably and undulate in severity over the course of months. Half of patients have focal or multifocal cranial nerve disease, including the facial, trigeminal, optic, vestibulocochlear, and oculomotor nerves.
Late stage II disease involves distal symmetric sensory neuropathy and encephalomyelitis, lasting for weeks or months. Motor signs are rare. Asymmetric oligoarthritis, cardiac impairment, and myositis can occur alongside a variety of CNS conditions in stage III disease. Demyelination and subacute encephalitis may be accompanied by ataxia, spastic paraparesis, bladder dysfunction, cognitive problems, and dementia.
Pathogenesis Lyme disease (sometimes known as Bannwarth's syndrome in Europe) is caused by infection with the Borrelia Burgdorferi spirochete. The infection is transmitted by bites from the Ixodes dammini, scapularis, and pacificus tick species. The cause of peripheral neuropathy following infection is unclear, although there is cross reactivity between spirochete antigens and epitopes from Schwann cells and PNS axons.
Diagnosis
Serology commonly leads to false positives. A combination of ELISA and Western blot of CSF and serum is more reliable. PCR of blood and CSF is the most specific method and can be used for difficult cases.
Therapy
Antibiotics are important both for eradication of the infection and quick resolution of painful symptoms. The usefulness of steroids for pain management is not clear at this point.
Prognosis
Antibiotic therapy typically leads to resolution of neurological symptoms in a few weeks to months.
Cranial neuropathies and peripheral neuropathies with sensory and motor signs occur in 20% of cases, but overall the disease is rare in the U.S. All extremities become weak. Initial infection is characterized by sore throat, dyspnea, and decreased lung function. Neurological symptoms begin with weakness in the diaphragm and pharynx 5-7 weeks later, and progress to trunk and limb weakness at 2-3 months.
The bacterial toxin released by Corynebacterium diphtheriae causes demyeli-nation, but cannot cross the blood brain barrier, and so damage is restricted.
Corynebacterium diphtheriae
(Diphtheria)
Pathogenesis
Throat culture confirms the presence of bacterium. EMG will show signs of Diagnosis demyelination.
Early use of antibiotics can be effective. Good, if treated early.
Therapy Prognosis
Mycobacterium leprae (Leprosy)
Fig. 12. Leprosy: this patient served with the foreign legion in North Africa. He has mutilated hands and toes and an ulcer
Leprous neuropathy is characterized by sensory loss in a patchy distribution. Clinical syndrome/
"Tuberculoid" leprosy involves only a few skin lesions with accompanying signs local sensory loss. "Lepromatous" disease is more extensive, with loss of temperature and pain occurring first on the forearms, legs, ears, and dorsum of hands and feet (Fig. 12). Cranial nerve damage can lead to facial damage, including iritis, alopecia, and changes in eyelid and forehead skin. Some patients with intermediate disease may be classified as "borderline". This group is most susceptible to therapy-induced reactions that cause disease to worsen for the first year of treatment.
Pathogenesis
Infection with Mycobacterium leprae causes severe disease in patients with an impaired cell-mediated immunity (lepromatous cases) or benign disease in patients with intact immunity (tuberculoid cases). Early lepromatous disease involves infection of Schwann cells with minimal inflammatory response. Later, increased inflammation may lead to axon damage, and scarring and onion bulb formation from episodes of demyelination and remyelination. Nerve damage from tuberculoid and borderline disease results from granuloma formation.
Diagnosis
Patients can be classified as lepromatous or tuberculoid by a skin reaction to injected lepromin antigen. Tuberculoid and borderline cases will have an indurated reaction at the injection site. Skin biopsy can show granulomas. Nerve biopsy is used when other causes need to be excluded. EMG shows segmental demyelination, axon damage, slowed NCV, and low amplitude SNAPs.
Therapy
Lepromatous patients are treated with dapsone for a minimum of 2 years. Tuberculoid and borderline patients are treated with dapsone and rifampin for 6 months. Cases of treatment-induced reactions require quick diagnosis and treatment with high-dose steroids until the reaction subsides. Attention must be given to areas of the body that have lost sensation.
Prognosis
Progression can be arrested by treatment, but outcomes are dependent upon the severity and duration of disease, and the response to treatment.
Other infectious neuropathies
Treponema pallidum A sexually transmitted disease caused by a spirochete. Peripheral nerve disease
(syphilis): may be heralded by lancinating pain, paresthesias, incontinence, and ataxia.
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