A Vulcan disease that results in the incurable degradation of the synaptic pathways. It also affects the Vulcan endocrine and immune systems. It is transmitted thru a specific form of telepathy known as the "Vulcan mind meld".
In 2151, Pa'nar Syndrome was still considered fatal until Dr. Phlox was able to develop a course of treatment (with the help of Dr. Yuris) after T'Pol herself contracted the disease. (ENT: "Stigma")