Definition
A slipped disc L4/5 is a prolapse (protrusion) of the intervertebral disc between the 4th and 5th vertebral bodies of the lumbar spine. In this disease of the spinal column, the inner gelatinous core (nucleus pulposus) slips out of its original position. It is surrounded by a fibrous ring (annulus fibrosus), which can tear due to increasing wear.
Parts of the inner nucleus and the outer fibrous ring can then press on the nerve roots or nerve fibres that run through the adjacent spinal canal. This causes neurological symptoms that can vary depending on the type and severity of the constricted nerve fibres. A prolapse often occurs between L4 and L5 and affects both men and women between the ages of 46 and 55. Only a herniated disc L5/S1 occurs more frequently than the slipped disc between L4 and L5. Only a slipped disc L5/S1 is even more frequent than the slipped disc between L4 and L5.
Causes
The causes for the development of a slipped disc in the lumbar spine can be very different. One of the main reasons is the increasing wear of the vertebral bodies due to aging. The fibrous ring, gelatinous core and also the surrounding bones become more and more porous and finally give in to the load.
The gelatinous core, which stores water and thus acts as a shock absorber between the vertebral bodies, increasingly loses its function of being able to store water. This results in cracks, especially in the rear part of the fibrous ring. This results in rapid slippage of the inner core in unfortunate jerky movements or even heavy lifting.
A further cause can be a permanent incorrect loading of the spinal column. A crooked posture at a desk or workplace leads to an uneven distribution of the load and can cause a herniated disc in the lumbar spine. The situation is similar when standing for a long time.
The load is greatest in the lumbar spine. In addition, factors such as age and overweight play an important role in the development of a herniated disc. Weak back and abdominal muscles do not stabilize the spine sufficiently, so that a herniated disc is more likely to develop because the wear and tear caused by overloading is also greater. Furthermore, certain sports that put a lot of strain on the back can also contribute to the development of a herniated disc. Less frequent causes are injuries due to accidents.
Symptoms
Damage L4 If the nerve tracts are severely impaired, various failure symptoms of the musculature can occur. The nerve fibres from L4 are, among other things, also responsible for the innervation of the thigh musculature. Due to the nerve damage, the patient may no longer be able to stretch the knee.
At the same time, lifting the foot can also be difficult. A lumbar disc herniation can cause numbness in addition to various symptoms. This is a numbness of different skin areas, which are sensitively supplied by the damaged nerves.
The symptoms can vary individually. Tingling, formication or even complete numbness can occur. The symptoms also depend on the severity of the nerve damage.
Depending on the extent of the nerve damage, the sensory disturbances occur in certain areas of the skin. The supply areas of the nerves that emerge from the vertebral bodies L4/5 are each responsible for a specific skin area on the leg. These delimited areas are called dermatome.
They provide an important indication of the extent of the damage in the context of diagnostics. For example, the physician can draw conclusions about the damaged nerves due to numbness at a certain skin area. In anatomy and also in neurology, identification muscles are defined as certain muscles that are innervated by a single segment of the spinal column.
A spinal ganglion is located at the level of this segment for both left and right, from which nerve fibres emerge to supply certain muscles. These characteristic muscles are particularly important in the diagnosis of various spinal diseases. In the event of a functional failure of these characteristic muscles, the physician can use certain tests to obtain an initial indication of the height of the spinal column at which the injury could be located.
The symptoms range from muscle weakness to a loss of muscle function. The extent depends on the severity of the nerve damage. In addition, certain reflexes may be weakened or no longer resolvable.
The characteristic muscle for segment L4 is the large thigh muscle (Musculus quadriceps femoris). It enables flexion in the hip joint and extension in the knee joint. If the responsible nerve is restricted due to a prolapse, it can lead to failure symptoms.
Furthermore, the function of the nerve can be tested with the patellar tendon reflex. To do this, the doctor taps with a reflex hammer slightly below the kneecap (patella) on the coarse muscle tendon running there. Under normal circumstances, the leg would shoot forward.
If there is damage to the nerve, the reflex may be weakened or may not even show at all. The characteristic muscle for the lumbar vertebral body segment 5 is the extensor of the big toe (Musculus extensor hallucis longus). If this segment is damaged, the patient is no longer able to consciously extend the big toe, depending on the severity of the injury.
The physician can additionally test the function of this nerve path with the Tibialis-Posterior Reflex (TPR). To do this, the doctor taps the corresponding tendon of the muscle with a special reflex hammer on the inside of the foot below the protruding ankle. On the slight tap, an internal rotation (supination) of the foot and also the extension of the big toe is seen.
If there is pronounced damage to the nerve tract and thus the characteristic muscle, this reflex cannot be triggered. Most herniated discs occur in the lumbar spine and affect the segments L4/L5. Since such a prolapse involves the slippage of the intervertebral disc, it can therefore move in different directions.
It can slip up or down as well as to the right or left. In case of a left or right shift, this is called a medio-lateral disc prolapse. This often leads to various symptoms.
Left and right from each segment of the spine, the spinal nerves emerge from the nerve root. They take over the innervation of muscles or internal organs. If the intervertebral disc slips to the side (laterally), these nerve roots are compressed and the nerves are constricted.
The longer this pressure is on the nerves, the more severe the symptoms. Frequently there is back pain on the corresponding side and also pain in the corresponding leg. Examinations of the leg can then provide information about the height of the injured segment.
Imaging procedures can then reveal the full extent of the injury. The images also show to which side (right, middle, left) the intervertebral disc has shifted. The diagnosis of a herniated disc L4/5 can be made very well in the context of a neurological examination.
In addition to a detailed anamnesis of the symptoms and especially the pain, the doctor can quickly obtain indications of existing nerve damage with the help of various tests. For example, he uses a reflex hammer to test the reflexes on arms and legs, the sensitivity of different areas of skin and also the mobility of different muscles. In addition, the nerve conduction speed can also be determined by a measurement.
It provides information on the function of the nerves. Depending on how well the reflexes can be resolved or where the pain radiates, the doctor can draw conclusions about which nerve roots may be damaged. The posture and course of the spine is also examined.
However, the diagnosis of a slipped disc is usually confirmed by a radiological examination. Imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI of the lumbar spine) are the means of choice. MRI of the lumbar spine and CT images of the spine are used.
In an MRI of the lumbar spine, the surrounding soft tissue structures, such as the intervertebral disc, can also be depicted very well. In the x-ray itself, fine cracks in the intervertebral disc may be seen in the event of a prolapse. In addition, the herniated disc L4/5 itself can also be seen very well if an image was taken laterally of the spine.
The intervertebral disc of the lumbar spine has then advanced into the spinal canal and the rear surfaces of the surrounding vertebral bodies are also closer together. The cartilaginous surfaces of the vertebral bodies can be porous due to wear and tear and incorrect loading. The procedures (CT/MRI of the lumbar spine) can also be supported by the administration of contrast medium injected through the vein. The structures are then once again more clearly visible.
