D
Deep Tendon Reflexes - The involuntary muscle jerks that are normally produced, when the tendon is tapped at certain spots on a limb with a hammer. In MS, the tone of these Reflexes are heightened by lack of Cortical inhibition (Spasticity). #25
Decompostion of Movement - inability to sequence properly fine, coordinated acts. #12
Decubitus - An Ulcer (Sore) of the Skin resulting from pressure and lack of movement, such as occurs when a person is mostly in a bed or a wheelchair. The Ulcers occur most frequently in areas where the bone lies directly under the Skin, such as the Elbow, Hip, or Tailbone. #28
Dementia - A generally profound and progressive loss of intellectual function, sometimes associated with personality change, that results from loss of Brain substance, and is sufficient to interfere with a person's normal functional activities. #28
DeMyelination - The destruction, loss, or removal of the Myelin Sheath, which normally insulates some Axons, by a disease process. Multiple Sclerosis is a Chronic CNS Disease that results in DeMyelination (Lesion, or Plaque), following damage to Axons, Myelin, Oligodendrocytes, or Neurons. #01, #09, #25 (View: Image, OR Image)
Also See: DeMyelinating Diseases Of The Brain
by: John R. Hesselink, MD, FACR
Dendrite Cell - A Phagocyte, these white blood cells are found in the Spleen and other Lymphoid Organs; they typically use threadlike tentacles to enmesh Antigen, which they present to T-Cells. #30
Diagnosis - The art or act of identifying a disease from its Signs and Symptoms. The MS diagnosis requires clinical evidence (a positve, objective finding) on Neurological Examination of two or more CNS White Matter lesions, in a person between 10 - 60 years old that occurred at two separate and distinct time periods, and of whom no other medical explanation exists ("Poser Criteria"). #12
Diplopia - Double Vision, or the simultaneous awareness of two images of the same object that results from the failure of the two Eyes to work in a coordinated fashion. Covering one Eye will eliminate Double Vision, by erasing one of the images. #25
(Also See: Fasciculus, Medial Longitudinal)
Disability
- A disability (resulting from an Impairment) is a restriction or lack of ability to perform an activity in the manner or within the range considered normal for a human being. Permanent MS disability is the result of Axons that have been severed and/or Atropied; while the temporary dysfunction experienced during an exacerbation is short-term, resolving after the Inflammation clears. #28
(See: Normal-Appearing White Matter & Axons & Disability)
Disseminated - Scattered or distributed (Multiple). #09
Dizziness
- A feeling of internal uneaseiness, confusion, or light-headedness (passing out). The term Dizzy is commonly confused with Vertigo (a sensation your surroundings are spinning). While the feeling that you are off-balance, vaguely out-of-sorts, and/or actually spinning (not your surroundings) is Dizziness. DeMyelination within the Cerebellum or its Nerve Pathways, may cause Dizziness.
Dysarthria
- Slurring, inappropriate phrasing and lack of modulation in Speech volume. Both Slurred and Scanning Speech are very common types of Motor-Dysarthrias and are generally a result of Lesions (DeMyelination), in the BrainStem or within its connecting Nerve pathways. #12
- Poorly articulated Speech resulting from Neural dysfunction of the Muscles controlling Speech. The content and meaning of spoken words remain normal. #28
Dyschromatopsia
- Impaired color vision, characterized by a reduced vividness of saturated colors. Dyschromatopsia, is always present in Optic Neuritis. In color terminology, Saturation refers to the purity of color, and desaturation is the degree to which a color is mixed with white.
- Some people see a red target characterize the sensation as darker, ie. red is shifted toward amber, whereas others say the color is bleached or lighter, ie. red is shifted towards orange. In the absence of a Macular lesion, color desaturation is a highly sensitive indicator of Optic Nerve Disease.
Dysdiadochokinesia - Inability to perform rapid alternating movements, such as the nose to finger Neurological Test. #12
Dysesthesia - Distorted or Unpleasant Sensations experienced by a person when the Skin is touched. It is often referred to as an unpleasant ''Burning'' Sensation. #25
Dyskinesia - Are stereotypical, involuntary movements that affect muscle groups in varying combinations. MyoClonus and Dystonia are the most common forms of Dyskinesia seen in MS. #12
Dysmetria - Inability to control range of movements. A disturbance of coordination, caused by lesions in the Cerebellum. A tendency to over or under estimate the extent of motion needed to place an arm or leg in a certain position. #12, #28
Dyspepsia - Indigestion, a feeling of being over stuffed. #09
Dysphagia - Difficulty in swallowing either solids, liquids, or both. It causes aspiration (food or saliva enters the airway), choking, and slow swallowing (possibly leading to inadequate nutrition).
- MS may cause Dysphagia, if Lesions develop in the BrainStem or along its connecting Nerve pathways, disrupting the sequencing and control of motor programs that govern muscles regulating swallowing (Mouth, Pharynx and Esophagus). #28
Dysphonia - Disorders of voice quality (including Poor Pitch Control, Hoarsness, Breathiness, and HyperNasality) caused by Spasticity, Weakness, and Incoordination of muscles in the Throat and Mouth. #28
Dystonia - movement disorders where sustained muscle contractions cause twisting and repetitive movements or abnormal postures. The movements are involuntary and sometimes painful, they may affect a single muscle; a group of muscles such as those in the arms, legs, or neck, or the entire body.
- Dystonia result from an abnormality in the Basal Ganglia, where some of the messages that initiate muscle contractions are processed. Scientists suspect a defect in the body's ability to process these NeuroTransmitters prevents Neurons from communicating with each other. Some of which include:
- GABA (Gamma-AminoButyric Acid) is inhibitory
- Dopamine is inhibitory
- Acetylcholine is excitatory
- In movement, Acetylcholine released at Nerve endings causes muscle contraction. NorEpinephrine and Serotonin are inhibitory NeuroTransmitters that help to regulate Acetylcholine.
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