tabes dorsalis, , also called Progressive Locomotor Ataxia, rare neurologic form of tertiary syphilis, involving sensory deficits, loss of neuromuscular coordination, and diminished reflexes. Symptoms of this form of neurosyphilis chiefly affect the legs and may not appear for more than 25 years after the initial infection. Untreated, tabes dorsalis usually makes unassisted walking impossible and severely debilitates the victim.
Symptoms result from degeneration of the dorsal roots of the spinal cord, giving it its name, which means “dorsal wasting.” The first manifestation is usually “lightning pain,” transient, stabbing pains affecting the legs; this is followed by loss of tendon reflexes and by progressive loss of muscular coordination (ataxia) causing a spasmodic, uneven walk. Victims become unable to sense pain, limb position, and temperature; these sensory deficits cause loss of bladder and sometimes bowel control, severe foot ulcerations, and Charcot joints (an osteoarthritis that typically involves the knees and hip). Neurologic deterioration also causes the pupils of the eye to lose their ability to react to changes in light.
Tabes dorsalis is seldom fatal. Elimination of the causative organism, Treponema pallidum, with penicillin may relieve pain but does not reverse nervous degeneration. Therapy otherwise involves support of diminished functions and prevention of further deterioration.