nerves level motor function c1–c6 neck flexors c1–t1 neck extensors c3, c4, c5 supply diaphragm (mostly c4) c5, c6 move shoulder, raise arm (deltoid); flex elbow (biceps) c6 externally rotate (supinate) the arm c6, c7 extend elbow and wrist (triceps and wrist extensors); pronate wrist c7, t1 flex wrist; supply small muscles of the hand t1–t6 intercostals and trunk above the waist t7–l1 abdominal muscles l1–l4 flex thigh l2, l3, l4 adduct thigh; extend leg at the knee (quadriceps femoris) l4, l5, s1 abduct thigh; flex leg at the knee (hamstrings); dorsiflex foot (tibialis anterior); extend toes l5, s1, s2 extend leg at the hip (gluteus maximus); plantar flex foot and flex toes further information: dermatome (anatomy) signs (observed by a clinician) and symptoms (experienced by a patient) vary depending on where the spine is injured and the extent of the injury. a section of skin innervated through a specific part of the spine is called a dermatome, and injury to that part of the spine can cause pain, numbness, or a loss of sensation in the related areas. paraesthesia, a tingling or burning sensation in affected areas of the skin, is another symptom. a person with a lowered level of consciousness may show a response to a painful stimulus above a certain point but not below it. a group of muscles innervated through a specific part of the spine is called a myotome, and injury to that part of the spinal cord can cause problems with movements that involve those muscles. the muscles may contract uncontrollably (spasticity), become weak, or be completely paralysed. spinal shock, loss of neural activity including reflexes below the level of injury, occurs shortly after the injury and usually goes away within a day. priapism, an erection of the penis may be a sign of acute spinal cord injury. the specific parts of the body affected by loss of function are determined by the level of injury. some signs, such as bowel and bladder dysfunction can occur at any level. neurogenic bladder involves a compromised ability to empty the bladder and is a common symptom of spinal cord injury. this can lead to high pressures in the bladder that can damage the kidneys. lumbosacral the effects of injuries at or above the lumbar or sacral regions of the spinal cord (lower back and pelvis) include decreased control of the legs and hips, genitourinary system, and anus. people injured below level l2 may still have use of their hip flexor and knee extensor muscles. bowel and bladder function are regulated by the sacral region. it is common to experience sexual dysfunction after injury, as well as dysfunction of the bowel and bladder, including fecal and urinary incontinence. thoracic in addition to the problems found in lower-level injuries, thoracic (chest height) spinal lesions can affect the muscles in the trunk. injuries at the level of t1 to t8 result in inability to control the abdominal muscles. trunk stability may be affected; even more so in higher level injuries. the lower the level of injury, the less extensive its effects. injuries from t9 to t12 result in partial loss of trunk and abdominal muscle control. thoracic spinal injuries result in paraplegia, but function of the hands, arms, and neck are not affected. one condition that occurs typically in lesions above the t6 level is autonomic dysreflexia (ad), in which the blood pressure increases to dangerous levels, high enough to cause potentially deadly stroke. it results from an overreaction of the system to a stimulus such as pain below the level of injury, because inhibitory signals from the brain cannot pass the lesion to dampen the excitatory sympathetic nervous system response. signs and symptoms of ad include anxiety, headache, nausea, ringing in the ears, blurred vision, flushed skin, and nasal congestion. it can occur shortly after the injury or not until years later. other autonomic functions may also be disrupted. for example, problems with body temperature regulation mostly occur in injuries at t8 and above. another serious complication that can result from lesions above t6 is neurogenic shock, which results from an interruption in output from the sympathetic nervous system responsible for maintaining muscle tone in the blood vessels. without the sympathetic input, the vessels relax and dilate. neurogenic shock presents with dangerously low blood pressure, low heart rate, and blood pooling in the limbs—which results in insufficient blood flow to the spinal cord and potentially further damage to it. cervical spinal cord injuries at the cervical (neck) level result in full or partial tetraplegia (also called quadriplegia). depending on the specific location and severity of trauma, limited function may be retained. additional symptoms of cervical injuries include low heart rate, low blood pressure, problems regulating body temperature, and breathing dysfunction. if the injury is high enough in the neck to impair the muscles involved in breathing, the person may not be able to breathe without the help of an endotracheal tube and mechanical ventilator. function after complete cervical spinal cord injury level motor function respiratory function c1–c4 full paralysis of the limbs cannot breathe without mechanical ventilation c5 paralysis of the wrists, hands, and triceps difficulty coughing, may need help clearing secretions c6 paralysis of the wrist flexors, triceps, and hands c7–c8 some hand muscle weakness, difficulty grasping and releasing complications complications of spinal cord injuries include pulmonary edema, respiratory failure, neurogenic shock, and paralysis below the injury site. in the long term, the loss of muscle function can have additional effects from disuse, including atrophy of the muscle. immobility can lead to pressure sores, particularly in bony areas, requiring precautions such as extra cushioning and turning in bed every two hours (in the acute setting) to relieve pressure. in the long term, people in wheelchairs must shift periodically to relieve pressure. another complication is pain, including nociceptive pain (indication of potential or actual tissue damage) and neuropathic pain, when nerves affected by damage convey erroneous pain signals in the absence of noxious stimuli. spasticity, the uncontrollable tensing of muscles below the level of injury, occurs in 65–78% of chronic sci. it results from lack of input from the brain that quells muscle responses to stretch reflexes. it can be treated with drugs and physical therapy. spasticity increases the risk of contractures (shortening of muscles, tendons, or ligaments that result from lack of use of a limb); this problem can be prevented by moving the limb through its full range of motion multiple times a day. another problem lack of mobility can cause is loss of bone density and changes in bone structure. loss of bone density (bone demineralization), thought to be due to lack of input from weakened or paralysed muscles, can increase the risk of fractures. conversely, a poorly understood phenomenon is the overgrowth of bone tissue in soft tissue areas, called heterotopic ossification. it occurs below the level of injury, possibly as a result of inflammation, and happens to a clinically significant extent in 27% of people. muscle mass is reduced as muscles atrophy with disuse. people with sci are at especially high risk for respiratory and cardiovascular problems, so hospital staff must be watchful to avoid them. respiratory problems (especially pneumonia) are the leading cause of death in people with sci, followed by infections, usually of pressure sores, urinary tract infections and respiratory infections. pneumonia can be accompanied by shortness of breath, fever, and anxiety. another potentially deadly threat to respiration is deep venous thrombosis (dvt), in which blood forms a clot in immobile limbs; the clot can break off and form a pulmonary embolism, lodging in the lung and cutting off blood supply to it. dvt is an especially high risk in sci, particularly within 10 days of injury, occurring in over 13% in the acute care setting. preventative measures include anticoagulants, pressure hose, and moving the patient's limbs. the usual signs and symptoms of dvt and pulmonary embolism may be masked in sci cases due to effects such as alterations in pain perception and nervous system functioning. urinary tract infection (uti) is another risk that may not display the usual symptoms (pain, urgency, and frequency); it may instead be associated with worsened spasticity. the risk of uti, likely the most common complication in the long term, is heightened by use of indwelling urinary catheters. catheterization may be necessary because sci interferes with the bladder's ability to empty when it gets too full, which could trigger autonomic dysreflexia or damage the bladder permanently. the use of intermittent catheterization to empty the bladder at regular intervals throughout the day has decreased the mortality due to kidney failure from uti in the first world, but it is still a serious problem in developing countries. an estimated 24–45% of people with sci have disorders of depression, and the suicide rate is as much as six times that of the rest of the population. the risk of suicide is worst in the first five years after injury. in young people with sci, suicide is the leading cause of death. depression is associated with an increased risk of other complications such as uti and pressure ulcers that occur more when self-care is neglected. causes falling as a part of recreational activities can cause spinal cord injuries. spinal cord injuries are most often caused by physical trauma. forces involved can be hyperflexion (forward movement of the head); hyperextension (backward movement); lateral stress (sideways movement); rotation (twisting of the head); compression (force along the axis of the spine downward from the head or upward from the pelvis); or distraction (pulling apart of the vertebrae). traumatic sci can result in contusion, compression, or stretch injury. it is a major risk of many types of vertebral fracture. pre-existing asymptomatic congenital anomalies can cause major neurological deficits, such as hemiparesis, to result from otherwise minor trauma. in the us, motor vehicle accidents are the most common cause of scis; second are falls, then violence such as gunshot wounds, then sports injuries. another study from asia, found that the most common cause of the sci is fall (31.70%) from various sites such as fall from roof-tops (9.75%), electric pole (7.31%), fall from tree (7.31%) etc. whereas road traffic accidents count for 19.51%, firearm injuries (12.19%), slipped foot (7.31%) and sports injuries (4.87%). as a result of injury, 26.82% in some countries falls are more common, even surpassing vehicle crashes as the leading cause of sci. the rates of violence-related sci depend heavily on place and time. of all sports-related scis, shallow water dives are the most common cause; winter sports and water sports have been increasing as causes while association football and trampoline injuries have been declining. hanging can cause injury to the cervical spine, as may occur in attempted suicide. military conflicts are another cause, and when they occur they are associated with increased rates of sci. another potential cause of sci is iatrogenic injury, caused by an improperly done medical procedure such as an injection into the spinal column. sci can also be of a nontraumatic origin. nontraumatic lesions cause anywhere from 30 to 80% of all sci; the percentage varies by locale, influenced by efforts to prevent trauma. developed countries have higher percentages of sci due to degenerative conditions and tumors than developing countries. in developed countries, the most common cause of nontraumatic sci is degenerative diseases, followed by tumors; in many developing countries the leading cause is infection such as hiv and tuberculosis. sci may occur in intervertebral disc disease, and spinal cord vascular disease. spontaneous bleeding can occur within or outside of the protective membranes that line the cord, and intervertebral disks can herniate. damage can result from dysfunction of the blood vessels, as in arteriovenous malformation, or when a blood clot becomes lodged in a blood vessel and cuts off blood supply to the cord. when systemic blood pressure drops, blood flow to the spinal cord may be reduced, potentially causing a loss of sensation and voluntary movement in the areas supplied by the affected level of the spinal cord. congenital conditions and tumors that compress the cord can also cause sci, as can vertebral spondylosis and ischemia. multiple sclerosis is a disease that can damage the spinal cord, as can infectious or inflammatory conditions such as tuberculosis, herpes zoster or herpes simplex, meningitis, myelitis, and