Lateral SpinoThalamic Tract - A Sensory Nerve Tract in the Anterior-Lateral (Front-Side) portion of the Spinal Cord. Interruption of the LST, results in loss of Pain and Temperature sensations below the level of the lesion, on the Opposite Side of the body. #01 (View: Image)
Lesion - Any damage to tissue structure or function. A Scar is a Lesion. So is Cancer, a MS Plaque, a Stomach Ulcer or a Pimple. On T1 MRI scans, old lesions register as *Black Holes* - HypoIntense (less tissue) areas. While new inflammatory lesions are seen on T2 scans as, *Bright Spots* - HyperIntense (higher fluid content) areas.
- MS lesions on conventional MRIs T2, first appear as small, ovid shaped, focal bright spots having discrete borders. Cerebral lesions are usually located centrally, near the MidLine, asymmetrically arrayed, deep within the White Matter, and close to a blood vessel (Venule) that is near CerebroSpinal Fluid (Ventricles, or Spinal Cord). #01
Leukocytes - Any of the blood cells that are colorless, lack Hemoglobin, and contain a Nucleus. They are also called White Blood Cells (Corpuscles).
L'hermitte's Sign - An electrical sensation (Shock, Lightning Bolt) that some MSers experience, when flexing the neck, tilting, or lowering the head towards the chest. It begins at the base of the skull, runs down the Spine and into the limbs, before exiting through the hands or feet. #02, #25
- L'hermitte's Sign is thought to stem from injury (ie: compression, distortion, inflammation, radiation, metabolic or toxic aberrations) of the Cervical Dorsal Columns.
- After injury, the damaged Dorsal Column Axons or cell bodies have increased MechanoSensitivity, producing Ectopic Action Potentials that occur with greatest frequency during Cervical flexion (i.e., a maneuver that can alter Spinal Cord length by 2 cm).
- L'hermitte's Sign occurs in 33% of MSers and was the presenting symptom in 16%. (Also See: Tic-Douloureux)
Ligand - A Molecule or Ion that can bind another Molecule.
Lobe (Of The Brain) - A major division of the Cerebral Hemisphere. Each Cerebral Hemisphere is divided into: Frontal Lobe, Parietal Lobe, Occipital Lobe, Temporal Lobe, and Limbic Lobe. #01
Lymphocytes - A variety of White Blood Cells (Leukocytes), which are part of the body's Cellular Immune System. #09
- White Blood Cells play a large role in the Immune System, by responding to Antigens and triggering reactions in other cells. #27 (Also See: Lymphocytes)
- Are produced by Bone Marrow Stem Cells and depending on their site of subsequent maturation, they develop into either: B-Cells or T-Cells. #30
B-Cells - are responsible for Humoral Immune Responses, they produce ImmunoGlobulins (AntiBodies) to fight ExtraCellular infections (Bacteria, Fungus, etc.).
- T-Cells - are responsible for Cell-Mediated Immune Responses (Cellular Immunology) including both effector and regulatory cells. Helper T-Cells prime both AntiBody-mediated and Cell-mediated effectors for the attack, while Suppressors await the signal to change, slow, or end the assult.
Natural Killer Cells (NK) - recognize classes of cells and destroy tumor cells on contact, without needing a costimulator signal.
- CytoToxic T-Cells (CD8+) - handle the destruction of host cells, which have become infected by Viruses or other IntraCellular Pathogens. #22, #30
Helper T-Cells (CD4+) - heighten the production of AntiBodies by B-Cells and regulate the activities of all effector cells. A functional subclass of T-Cells that helps to generate CD8+ Cells and cooperate with B-Cells in the production of AntiBody-mediated responses.
- CD4+ Cells only recognize Antigens that are presented in association with MHC Class II molecules. #30
Suppressor T-Cells - supress B-Cell activity and seem to be in short supply during a MS attack (exacerbation). #28
- A functionally defined population of T-Cells which reduce the Immune Responses of other T-Cells or B-Cells, or switch the response onto a different pathway. #30