alt=A human spinal column alt=A person with dermatomes mapped out on the skin The effects of<unk>  depend on the level along the spinal column (left). A dermatome is an area of the skin that sends sensory messages to a specific spinal nerve (right). alt=diagram of vertebrae and spinal nerves Spinal nerves exit the spinal cord between each pair of vertebrae.<unk>  can be traumatic or nontraumatic, and can be classified into three types based on cause: mechanical forces, toxic, and ischemic (from lack of blood flow). The damage can also be divided into primary and secondary<unk> : the cell death that occurs immediately in the original<unk> , and biochemical cascades that are initiated by the original insult and cause further tissue damage. These secondary<unk>  pathways include the ischemic cascade, inflammation, swelling, cell suicide, and neurotransmitter imbalances. They can take place for minutes or weeks following the<unk> . At each level of the spinal column, spinal nerves branch off from either side of the spinal cord and exit between a pair of vertebrae, to innervate a specific part of the body. The area of skin innervated by a specific spinal nerve is called a dermatome, and the group of muscles innervated by a single spinal nerve is called a myotome. The part of the spinal cord that was damaged corresponds to the spinal nerves at that level and below.<unk> es can be cervical 1–8 (C1–C8), thoracic 1–12 (T1–T12), lumbar 1–5 (L1–L5), or sacral (S1–S5). A person's level of<unk>  is defined as the lowest level of full sensation and function. Paraplegia occurs when the legs are affected by the spinal cord damage (in thoracic, lumbar, or sacral<unk> es), and tetraplegia occurs when all four limbs are affected (cervical damage).<unk>  is also classified by the degree of impairment. The International Standards for Neurological Classification of<unk>  (ISNCSCI), published by the American Spinal<unk>  Association (ASIA), is widely used to document sensory and motor impairments following<unk> . It is based on neurological responses, touch and pinprick sensations tested in each dermatome, and strength of the muscles that control key motions on both sides of the body. Muscle strength is scored on a scale of 0–5 according to the table on the right, and sensation is graded on a scale of 0–2: 0 is no sensation, 1 is altered or decreased sensation, and 2 is full sensation. Each side of the body is graded independently. Muscle strength ASIA Impairment Scale for classifying<unk>  Grade Muscle function Grade Description 0 No muscle contraction A Complete<unk> . No motor or sensory function is preserved in the sacral segments S4 or S5. 1 Muscle flickers B Sensory incomplete. Sensory but not motor function is preserved below the level of<unk> , including the sacral segments. 2 Full range of motion, gravity eliminated C Motor incomplete. Motor function is preserved below the level of<unk> , and more than half of muscles tested below the level of<unk>  have a muscle grade less than 3 (see muscle strength scores, left). 3 Full range of motion, against gravity D Motor incomplete. Motor function is preserved below the level of<unk>  and at least half of the key muscles below the neurological level have a muscle grade of 3 or more. 4 Full range of motion against resistance E Normal. No motor or sensory deficits, but deficits existed in the past. 5 Normal strength Complete and incomplete<unk> es + Level and completeness of<unk> es Complete Incomplete Tetraplegia 18.3% 34.1% Paraplegia 23.0% 18.5% In a "complete" spinal<unk> , all functions below the<unk> d area are lost, whether or not the spinal cord is severed. An "incomplete"<unk>  involves preservation of motor or sensory function below the level of<unk>  in the spinal cord. To be classed as incomplete, there must be some preservation of sensation or motion in the areas innervated by S4 to S5, e.g. voluntary external anal sphincter contraction. The nerves in this area are connected to the very lowest region of the spinal cord, and retaining sensation and function in these parts of the body indicates that the spinal cord is only partially damaged. Incomplete<unk>  by definition includes a phenomenon known as sacral sparing: some degree of sensation is preserved in the sacral dermatomes, even though sensation may be more impaired in other, higher dermatomes below the level of the lesion. Sacral sparing has been attributed to the fact that the sacral spinal pathways are not as likely as the other spinal pathways to become compressed after<unk>  due to the lamination of fibers within the spinal cord.<unk>  without radiographic abnormality<unk>  without radiographic abnormality exists when<unk>  is present but there is no evidence of spinal column<unk>  on radiographs. Spinal column<unk>  is trauma that causes fracture of the bone or instability of the ligaments in the spine; this can coexist with or cause<unk>  to the spinal cord, but each<unk>  can occur without the other. Abnormalities might show up on magnetic resonance imaging (MRI), but the term was coined before MRI was in common use. Central cord syndrome Incomplete lesions of the spinal cord: Central cord syndrome (top), Anterior cord syndrome (middle), and Brown-Séquard syndrome (bottom). Central cord syndrome, almost always resulting from damage to the cervical spinal cord, is characterized by weakness in the arms with relative sparing of the legs, and spared sensation in regions served by the sacral segments. There is loss of sensation of pain, temperature, light touch, and pressure below the level of<unk> . The spinal tracts that serve the arms are more affected due to their central location in the spinal cord, while the corticospinal fibers destined for the legs are spared due to their more external location. The most common of the incomplete<unk>  syndromes, central cord syndrome usually results from neck hyperextension in older people with spinal stenosis. In younger people, it most commonly results from neck flexion. The most common causes are falls and vehicle accidents; however other possible causes include spinal stenosis and impingement on the spinal cord by a tumor or vertebral disk. Anterior cord syndrome Anterior cord syndrome, due to damage to the front portion of the spinal cord or reduction in the blood supply from the anterior spinal artery, can be caused by fractures or dislocations of vertebrae or herniated disks. Below the level of<unk> , motor function, pain sensation, and temperature sensation are lost, while sense of touch and proprioception (sense of position in space) remain intact. These differences are due to the relative locations of the spinal tracts responsible for each type of function. Brown-Séquard syndrome Brown-Séquard syndrome occurs when the spinal cord is<unk> d on one side much more than the other. It is rare for the spinal cord to be truly hemisected (severed on one side), but partial lesions due to penetrating wounds (such as gunshot or knife wounds) or fractured vertebrae or tumors are common. On the ipsilateral side of the<unk>  (same side), the body loses motor function, proprioception, and senses of vibration and touch. On the contralateral (opposite side) of the<unk> , there is a loss of pain and temperature sensations. Posterior cord syndrome Posterior cord syndrome, in which just the dorsal columns of the spinal cord are affected, is usually seen in cases of chronic myelopathy but can also occur with infarction of the posterior spinal artery. This rare syndrome causes the loss of proprioception and sense of vibration below the level of<unk>  while motor function and sensation of pain, temperature, and touch remain intact. Usually posterior cord<unk> es result from insults like disease or vitamin deficiency rather than trauma. Tabes dorsalis, due to<unk>  to the posterior part of the spinal cord caused by syphilis, results in loss of touch and proprioceptive sensation. Conus medullaris and cauda equina syndromes Conus medullaris syndrome is an<unk>  to the end of the spinal cord, located at about the T12–L2 vertebrae in adults. This region contains the S4–S5 spinal segments, responsible for bowel, bladder, and some sexual functions, so these can be disrupted in this type of<unk> . In addition, sensation and the Achilles reflex can be disrupted. Causes include tumors, physical trauma, and ischemia. Cauda equina syndrome (CES) results from a lesion below the level at which the spinal cord splits into the cauda equina, at levels L2–S5 below the conus medullaris. Thus it is not a true spinal cord syndrome since it is nerve roots that are damaged and not the cord itself; however, it is common for several of these nerves to be damaged at the same time due to their proximity. CES can occur by itself or alongside conus medullaris syndrome. It can cause low back pain, weakness or paralysis in the lower limbs, loss of sensation, bowel and bladder dysfunction, and loss of reflexes. Unlike in conus medullaris syndrome, symptoms often occur on only one side of the body. The cause is often compression,
Spinal cord injury
Spinal tumor
Vascular myelopathy
Posterior cord syndrome
Basal ganglia disease
Spinal disease
Syringomyelia
Central cord syndrome