Vacuolar myelopathy

Vacuolar myelopathy is a disease affecting the central nervous system, caused by damage to myelin, the fatty tissue that covers and protects nerves. The myelin sheath around the spinal cord ensures that electrical messages sent by nerves are properly directed. In vacuolar myelopathy, the myelin sheath separates from the spinal cord, forming cavities or vacuoles. This causes disruption of bodily movements and functions.

There is evidence that up to 30% of adults with AIDS experience some level of damage to the myelin, although clinical signs of this condition are less common. The incidence of vacuolar myelopathy may be much higher in among HIV-infected children.

Symptoms include numbness in the limbs, brisk tendon reflexes, weakness and sensory abnormalities in the legs, problems with movement, impotence, frequent urination and incontinence. As a progressive condition, paralysis of the lower limbs may develop.

The cause of the condition in HIV-infected people is unknown, although researchers have proposed a number of possible mechanisms. One theory is that HIV in the central nervous system may lead to an over-production of the cytokine tumor necrosis factor, and an under production of interleukin-4 and interleukin-10. Dysregulation of these cytokines, in turn, damages the myelin.

Another theory contends that vacuolar myelopathy is due to direct HIV infection of cells in the central nervous system called oligodendrocytes.