Multiple Sclerosis (MS) is an autoimmune disorder where the immune system mistakenly attacks the Central Nervous System (CNS), specifically targeting the protective myelin sheath surrounding nerve fibers in the brain and spinal cord. This attack causes inflammation and scarring, which appear as damaged areas called lesions. When lesions occur in the spinal cord, they disrupt the flow of nerve signals between the brain and the rest of the body. Since the spinal cord is the main pathway for physical commands and sensory information, damage in this location is responsible for many disabling MS symptoms. The specific symptoms experienced depend on the precise location and size of the lesions within the spinal cord nerve tracts.
Impact on Movement and Mobility
Spinal cord lesions frequently interrupt motor pathways, leading to muscle weakness (paresis), often affecting the legs and resulting in difficulty controlling lower limb movements. The inability to regulate muscle tension below the lesion causes spasticity, characterized by involuntary stiffness, tightness, and painful spasms.
The combination of weakness and spasticity complicates walking and balance. Damage to coordinating tracts can lead to ataxia, resulting in clumsy or unsteady movements, often requiring the use of assistive devices.
Fatigue is another common consequence accompanying motor impairment. This fatigue severely limits physical activity and endurance because the body expends more energy to execute movements compromised by weakness and spasticity.
Altered Sensations and Pain
Lesions in the sensory tracts interrupt information flowing back to the brain, causing various abnormal sensations. The most common is paresthesia, described as “pins and needles,” numbness, or tingling. This results from garbled transmission of nerve impulses through demyelinated sections.
More severe sensory disruption is dysesthesia, involving abnormal and often painful sensations without external triggers. These include feelings of burning, electrical shocks, or a crawling sensation on the skin. Neuropathic pain is chronic pain caused directly by nerve damage, often described as stabbing or shooting.
The “MS Hug” is a unique symptom related to thoracic spinal lesions, causing a painful, band-like sensation of tightness or squeezing around the torso. Lhermitte’s sign is an electrical sensation where bending the neck forward sends a brief, shock-like feeling down the spine and into the limbs. This sign is caused by mechanical stretching of damaged nerve fibers in the cervical region.
Autonomic Function and Internal Systems
The spinal cord houses pathways of the autonomic nervous system, and lesions here can cause internal system dysfunction. Bladder issues are highly prevalent when nerve signals are interrupted, often resulting in an overactive bladder. This causes urinary frequency, urgency, and incomplete emptying, which increases the risk of infection.
Bowel dysfunction is also common, with constipation being the most frequent complaint due to slowed transit time. Impaired nerve signals affect the smooth muscle contractions needed for normal bowel movements.
Spinal lesions can affect sexual function by disrupting the nerves that control sensation and response. This manifests as reduced sensation, difficulty achieving arousal, or challenges in reaching orgasm.
Spinal lesions can occasionally affect temperature regulation, contributing to heat sensitivity (Uhthoff’s phenomenon). A rise in body temperature can temporarily worsen existing neurological symptoms because demyelinated nerve fibers are vulnerable to minor temperature fluctuations.