Healthline reports that a lesion on the spine is defined as scar tissue on the spinal nerves due to injury, inflammation or disease. The two types of spinal lesions are inactive lesions and active lesions. Spinal lesions are commonly associated with multiple sclerosis but aren't limited to that condition.
Healthline describes inactive lesions as scar tissue that is not expanding or causing an symptoms. Active lesions are those that are new, currently growing or causing symptoms in a patient. Doctors can identify active from inactive lesions by using contrast dye during a magnetic resonance imaging test. The National Multiple Scerlosis Society reports that diseases such as leukodystrophy, cancer, motor neuron disorder, neuromyelitis optica and acute disseminated encephalomyelitis can also involve spinal lesions.