Hernia is an abrupt condition which usually leads to an emergency that can be life threatening. Disc herniation is one of the most frequent conditions of the spine especially pertaining to sport injuries and trauma. The lumbar region begins from distal end of the vertebral column consisting of five vertebrae. They are chronologically represented as L1, L2, L3, L4 and L5 respectively. The vertebral column contains discs which enable them in dexterity and movement in absorbing the shock and friction during any kind of physical activity. About 60% of people experience because of the disposition of these vertebral discs located in the lumbar region.
Herniated discs can cause excruciating pain because of the location and associations with numerous nerve endings and blood vessels passing through the region. The initiation of the lumbar hernia is predominantly because of wear and tear caused to the disc or sometimes due to trauma. The inter vertebral discs contain viscous nucleus which tends to permeate to the outer region of the disc causing pressure on it to slip forward or herniate. The first noticeable symptom of lumbar hernia is observed at this point. The patient complains of radiating pain in the sciatic or thigh region. Other symptoms include lower back pain, weakness in the legs and numbness or tingling sensation in the feet.
Lumbar herniation can also be connected with other underlying medical conditions such as cauda equina syndrome in which urinary incontinence is noticed. The spinal roots are usually impaired because of compression thus leading lack of bladder control.
Diagnosis of Lumbar herniation
Lumbar herniation requires radiological and neurological diagnostic methods to identify the exact location of the herniated disc and to identify the presence of any inflammation and nerve root compressions. Neurological examinations also include nerve conduction studies to identify the presence of neurogenic or myogenic conditions caused due to the herniated disc. It also helps in identifying neuromuscular deterioration and weakness associated with it. Physical examination maneuvers such as straight leg raise is done to diagnose the origin of pain radiation. MRI also provides a comprehensive analysis of the herniated disc along with its adjacent impaired neuromuscular involvement.
Herniated discs are treated depending upon the intensity of the damage caused. Sometimes physiotherapy on a regular basis can reduce the pain caused because of movements at a certain angle. Anti-inflammatory drugs, epidural administration of steroids can reduce the pain to a greater extent. Other options includes surgical interventions such removal of the disc.
Anterior Cord Syndrome
Anterior Cord Syndrome refers to the Anterior Spinal Artery Syndrome. The anterior spinal artery originates from the vertebral arteries and basal artery at the base of the brain. It supplies the anterior two thirds of the spinal cord to the upper thoracic, that is chest, region. Anterior cord syndrome results from injury to the motor and sensory pathways in the anterior cord. Patients suffering from Anterior Cord Syndrome may feel some crude sensations, but their movement and more detailed sensation is lost. In Anterior cord syndrome there is damage primarily in the anterior 2/3 cord. This is related to vascular insufficiency, sparing the posterior columns. Anterior cord syndrome usually results from the compression of the artery that runs in front of the spinal cord. The compression may be from bone fragments or a large disc herniation.
MRI is a most accurate imaging test for spinal disorders. This is because in MRI the spinal cord parenchyma, soft tissue lesions like hematomas, tumors and interverterbral disks, bony lesions like erosion, hypertrophic changes, collapse, fracture and subluxation are revealed. Myelography with a radiopaque agent is used less often. Physicians normally use CT scans to demonstrate bony fragments compressing the anterior spinal cord. X rays may help to detect bony lesions.
Anterior cord syndrome is said to have the worst prognosis of all cord syndromes. The prognosis is usually good if the recovery is evident and progressive in the patient during first 24 hours. However, if there are no signs of sacral sensibility to pinprick or temperature are present after 24 hours, then the prognosis for functional recovery can be said to be poor. There is no standard course of treatment or cure for anterior cord syndrome. Physicians adopt drug therapies and surgery as part of the treatment program. There have been some exceptional cases where sensations that travel along pathways are still intact after the injury. Normally, it is observed that only 10 to 15% of anterior cord syndrome sufferers demonstrate any improvement in functions over a period of time.
Nerve Conduction Study
A medical diagnostic tool used to evaluate the ability of the motor and sensory nerves for electrical conduction is the Nerve conduction study. Nerve conduction studies are performed by medical specialists in neurophysiology, physiatry and neurology with sub-specialization in electro diagnostic medicine. The common measurement made during this test is called Nerve conduction velocity or NCV. This is conducted to determine the damage and destruction caused to nerves.
The procedure is to stimulate the nerve with surface electrode patches attached to the skin. Two electrodes are placed on the skin over the nerve. One electrode stimulates the nerve with a mild electrical impulse. The resulting electrical activity is recorded by another electrode. This testing is repeated in about 2 - 3 places along the arms or legs. After the procedure, the nerve conduction speed is calculated by measuring the distance between electrodes and the time it takes for electrical impulses to travel between electrodes.
The nerve conduction velocity (speed) is then calculated by measuring the distance between electrodes and the time it takes for electrical impulses to travel between electrodes.
A related procedure that may be performed is electromyography (EMG). An EMG measures the electrical activity in muscles and is often performed at the same time as NCS. Both procedures help to detect the presence, location and extent of diseases that damage the nerves and muscles.
Prior to the procedure
This study does not require any fasting or sedation prior to the procedure. But body temperature must be maintained before and during the procedure as low body temperature slows nerve conduction. Keep the doctor informed in case of any medicine or herbal supplements you might be taking. You must stop using lotions or oils on your skin a few days before the procedure. Based on your medical condition, the doctor may request any other specific preparation.
During the procedure
A nerve conduction study is performed as an outpatient procedure although procedures may vary depending upon the condition and doctor's practices. The study is performed by a neurologist although a technologist may perform portions of the test. During the procedure, the patient is asked to remove any clothing, jewelry, hairpins, eyeglasses, hearing aids, or any other metal objects that may interfere with the procedure.
The patient is asked to either sit or lie down for the test. A recording electrode is attached to the skin over the nerve with a special paste. A stimulating electrode is placed at a known distance away from the recording electrode. The nerve is stimulated by a mild and brief electrical shock through the stimulating electrode. You might experience minor discomfort for a few seconds. The patient senses rapid tingling in the area. The stimulation of the nerve and the response are displayed on an oscilloscope.
What does the test results indicate?
Generally, the nerve conduction velocity would be around 50 to 60 meters per second. But it tends to vary from person to person and from one nerve to another.
The speed of the nerve conduction study is related to the diameter of the nerve and the degree of myelin sheath (which is a type of insulation) around the nerve. While a normally functioning nerve will transmit a stronger and faster signal, a damaged nerve will be slower. The larger the wire, the better the insulation and more consistent and stronger will be the signal.
If results are abnormal, they may be due to some sort of neuropathy or damage to the nerve resulting from a traumatic injury or nerve. Sometimes, other diseases may also cause the impulses to slow down. It could be due to conduction block that is an obstacle to the impulse within the nerve or due to demyelination or damage to the myelin sheath.
Why nerve conduction study?
Nerve conduction study is done along with EMG to differentiate a nerve disorder from a muscle disorder. While nerve conduction study detects whether the nerve has any problem, EMG detects whether a muscle is functioning properly in response to the nerve's stimulus. Whenever there is any neurologic injury or disorder, nerve conduction studies often combined with needle electromyography measure are used. This helps in identifying cause for any pain or weakness in the limbs from spinal nerve compression or injury.
Nerve conduction studies are used primarily for evaluation of numbness, tingling and burning or weakness of arms and legs depending upon the part of the body the symptom is present. Physical examination by the doctor and patient's history help to direct the investigation. A number of disorders are diagnosed by nerve conduction studies - carpal tunnel syndrome, Gullian-Barre syndrome, peripheral neuropathy, spinal disc herniation, ulnar neuropathy and others.
Risks of the procedure
Although the voltage of electrical pulses used in this study is quite low, there may be risks depending upon specific medical conditions. Certain factors such as damage to the spinal cord, severe pain before the test and body temperature may affect the test. In case you are using cardiac defibrillator or pacemaker, adequate precautions need to be taken.
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Bibliography / Reference
Collection of Pages - Last revised Date: December 1, 2022