Absence of Local Sign Withdrawal in Chronic Human Spinal Cord Injury

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Absence of Local Sign Withdrawal in Chronic Human Spinal Cord Injury

Spinal cord
• Main pathway of communication between the brain and the rest of the body. • Soft tube-like structure of nerves that extends downward from the base of the brain. • Protected by the bones of spinal column.

- Nerves enter and exits from the spinal cord through its length, passing through small openings between each vertebra. • It is highly organized.
- Anterior motor neuron – transmit information to muscles and stimulate movement. - Posterior sensory neuron – transmits information to the brain about sensations such as touch, position, pain, heat and cold.

Flexor Reflexes
• A.k.a. withdrawal reflexes.
• Reflexes where in the flexor muscles contract due to a cutaneous sensory stimulus.

Local Sign
• Principle where the integrative centers of the cord cause groups of muscles to contract effectively and remove the pained part of the body from the object that cause pain.

Local Sign Withdrawal
• A reflex directing the limb away from noxious stimuli. • An indicative of a modular organization of spinal cord.

Windup-Crossover Test
• Test employing a sequence of stimuli not more than 3 seconds, used to assess whether common neuronal pathways were responsible for the loss of modular organization.

Spinal Cord Injury
• It is the damage to the nerves to the spinal canal.
• Identified as low incidence, high-cost disability requiring tremendous changes in patient’s life-style.

Etiology of Spinal Cord Injury
1. Traumatic Injuries
▪ Most frequent cause of injury.
▪ Result from damage caused by a traumatic event. e.g. vehicular accident
gunshot wound

2. Non-traumatic Injuries
▪ Result from a disease or pathologic influence. e.g. Vascular malfunctions (thrombosis, hemorrhage). Vertebral subluxations – secondary to rheumatoid arthritis Infection – syphilis, spinal neoplasm etc.

Two Types of Lesions
1. Complete Lesions
▪ There is no sensory or motor function below the level of the lesion.

2. Incomplete Lesions
▪ Characterized by preservation of some sensory-motor function below the level of injury.

• Local sign withdrawal is observed in spinal-intact humans in response to electrocutaneous stimuli applied to the different regions of skin on the foot and leg. After spinal cord injury, this organization of electrocutaneous reflexes was questioned. • The skin regions of the spinal-intact human foot have been mapped in detail regard to the activity of the muscles of the leg, demonstrating a clear pattern of muscle activity consistent with local sign withdrawal from the stimulus.

Study Description
Session 1 – test for Local Sign Withdrawal
4-6 location of the lower leg and foot.
Subject: 10 Spinal Cord Injured Patient
3 Spinal-intact Patient

Session 2 – test for Windup-crossover
4 locations on the foot and lower leg
Subject: 10 Spinal Cord Injured Patient (8 from session 1)

Test Apparatus
• Each subject was seated in an adjustable chair (Biodex). The foot was clamped to a fixation plate coupled with a load cell. The load cell was used to measure the isometric joint torque response to electrocutaneous stimuli. • Surface EMG were recorded from the tibialis anterior, soleus, medial gastrocenemius, vastus medialis, rectus femoris and biceps femoris.

• Stimulating electrodes were placed at the high point of the medial arch of the foot, on the foot dorsum approximately 3cm distal to the ankle joint. On the foot dorsum at the base of 1st and 2nd metatarsals. At the ankle posterior to the lateral malleolus (near the sural nerve), and on the posterior and...
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