Feeling & function
The peripheral nerves are those nerves that exit from the spinal cord and thereafter the vertebral column to supply sensation and motor function.
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Other neural compressions can occur in the arms and legs that are less common and usually need to be carefully distinguished from other conditions, including neural compression at the spine.
It is not unexpected for a neurosurgeon to see peripheral neural compressive syndromes treated as other more common conditions, until the appropriate expertise in examination and investigation reveal the true pathology.
- Nerve conduction studies provide a functional rather than just anatomic review of a nerve allowing accurate diagnosis
- Non-surgical options in management will often suffice in treating the condition
- If surgery is required, then generally, ‘day case’ surgery is appropriate
- A family history of peripheral nerve compression is often very relevant and should be made clear to the neurosurgeon.
Services & Information
The peripheral nerves are those nerves that exit from the spinal cord and thereafter the vertebral column to supply sensation and motor function. Peripheral nerves may be mixed nerves supplying both, or they may be solely one or the other. These peripheral nerves can become entrapped through a variety of reasons producing symptoms that are quite significant. These symptoms may resolve on their own, or may continue and require treatment. Surgical decompression is one of those treatments.
Peripheral nerve concerns can often be mistaken for, or misdiagnosed as, a nerve related concern coming from the spine itself. Nerve roots that exit the spine can come together or split apart distant to the vertebral column to form the peripheral nerves. Therefore, most peripheral nerves are made up of one or more nerve roots from the spine. The symptoms that arise from nerve root compression at the spinal level can often seem similar or even the same as symptoms that arise from a peripheral nerve entrapment in a limb. On rare occasions, both can occur simultaneously.
A good clinical history, physical assessment, and radiological review may be insufficient. There may be other tests that are required, such as nerve conduction studies or EMG, to try to differentiate where the source of the concern is coming from. When it has been determined that a peripheral nerve is the cause of the concern, there are certain surgical considerations in reference to relieving that pain. Not all peripheral nerve surgical procedures are performed by Neurosurgeons. Orthopaedic hand and upper limb and lower limb surgeons perform surgeries that Neurosurgeons often do not and the opposite is also true. Finally, some of these syndromes are so common (such as carpal tunnel syndrome) that many different specialties offer that surgery.
Carpal Tunnel Syndrome
Carpal tunnel syndrome is the most common peripheral neurological compression. It can occur unilaterally or bilaterally.
The carpal tunnel is in essence an area where the forearm meets the hand. There is a semicircle of bone in cross section roughly that makes up one side and there is a fibrous ligament that makes up the other. Running through that area are many of the tendons that move the hand and the fingers of the hand, blood vessels and the median nerve. It is the median nerves compression that brings on these symptoms. The median nerve happens to be placed on the palm side of the wrist, with the other structures mainly deeper. The median nerve starts to cause symptoms such as heaviness in the hand, sensation changes and pain when it becomes compressed. It can become compressed due to the thickening of the ligament above it, due to inflammatory changes within the carpal tunnel, due to blood vessel changes, due to changes within the tendons and due to growths within the carpal tunnel taking up space. A classic time that carpal tunnel will manifest is during pregnancy. The physiological changes of pregnancy can bring on these symptoms and subsequently, with the resolution of those symptoms at childbirth, the symptoms can resolve once more.
If the symptoms have been confirmed and clinically there is no other cause, then various courses of management can be undertaken. Many of these are avoidance of exacerbating factors, such as splinting the wrist at night to ensure it stays straight, guided injections around the region and even anti-inflammatories. Further, if these symptoms are not particularly severe, they can simply be tolerated without any specific intervention. Should intervention be considered, surgical decompression is certainly reasonable. Without going into the nuances of decompression, the requirement really is to allow the nerve more room, such that it is no longer compressed, and the symptoms are allowed to resolve. This can occur through an open direct approach or through an endoscopic approach. Both are valid ways of decompressing the nerve.
There are certain risks involved in carpal tunnel surgery and while rare, some of them are particularly problematic and difficult to manage. Thus, while this surgery perhaps can be considered as relatively straight forward comparative to many, it must still be considered as a surgical intervention like any other with the risks, benefits and complications possible weighed up before proceeding. That process ought to occur with your Neurosurgeon after the diagnosis has been made.
Thoracic Outlet Syndrome
Thoracic outlet syndrome is something that can occur due to a congenital abnormality such as a band or a cervical (neck) rib. It can also manifest due to muscular enlargement or other compressive lesion in the region. The thoracic outlet is an area at the root of the neck that allows the transmission of blood vessels and nerves to the arms. If compression occurs, it can cause problems with the blood vessels only, the nerves only or both. Classically the symptoms become worse with posture, particularly when the arms are raised. History, examination and static imaging may be insufficient. Dynamic imaging including ultrasound with arm movement or nerve conduction studies may be required.
Treatment of this condition is not always surgical. Symptoms may subside with removal of an aggravating factor such as working with the arms above shoulder level or changing a gym routine. When surgery is required, it is generally required to remove part of the 1st rib to open the thoracic outlet and allow the blood vessels and nerves to relax. Occasionally, division of a congenital (since birth) fibrous band or extra cervical rib may be sufficient.
Ulnar Nerve Decompression
The ulnar nerve is a nerve that arises from the nerve roots in the neck, travels through the brachial plexus in the root of the neck and moves into the arm in one muscular compartment before diving down into another through a fibrous membrane. That nerve then swings around the inside of the elbow before again diving down between the two attachments of a muscle in the forearm to supply various muscles and sensation to the small and ring fingers of the hand and that border of the hand also. When the C8 nerve in the neck is compressed, it can cause very similar sensory symptoms to concerns with the ulnar nerve because the ulnar nerve has a large component made up by that C8 nerve root. It must always be differentiated from a C8 nerve root compression in the neck and often nerve conduction studies will help make that differentiation.
When it has been identified that the ulnar nerve is a concern and that the symptoms are significant enough to warrant surgical intervention, then surgical decompression needs to consider the three areas where the nerve could be compressed. That could be at times through the muscle compartment in the arm, around the elbow or as it dives under that muscle into the forearm. Generally speaking, the incision has to be carefully placed to ensure when the elbow bends that the scar does not stretch back over the nerve and cause the symptoms once more. This surgery usually requires an overnight stay and is more uncomfortable than carpal tunnel surgery in the short term. Again, the nuances of surgery should be discussed with your Neurosurgeon, not all incidences of ulnar dysfunction require surgical decompression, though those that do generally respond well.
Meralgia paraesthetica is a burning pain on the front aspect of the thigh that manifests due to a problem with the lateral femoral cutaneous nerve of the thigh. There can be an overlap of symptoms from the ilio-inguinal nerve. Meralgia paraesthetica can occur due to direct trauma in relation to the nerve, and this can be even due to surgeries around the inguinal or groin region. It can manifest in the absence of trauma with rapid weight gain or weight loss of a considerable nature, which can include during pregnancy.
The lateral femoral cutaneous nerve of the thigh comes out of the pelvis underneath the inguinal ligament, which is the binding area that forms the groin. The nerve can be variable in its trajectory and be at a greater or lesser risk based on that variability. This burning pain must be differentiated from discomfort that arises from nerve roots that exit from the mid to upper aspect of the lumbar spine. Though this often can be done clinically, it is prudent to image the lumbar spine to ensure that nothing has been overlooked.
Treatment ranges from medications through to guided injections and potentially decompression. When surgery is contemplated, it is usually when other aspects of management have failed. Surgery can replace the pain with numbness, which though not as significant can still be a troubling symptom. Meralgia paraesthetica can be quite debilitating, and if other treatments have failed, surgical correction through decompression of the nerve is a not unreasonable treatment. As with any surgical endeavour there are risks, which ought to be discussed with your Neurosurgeon prior to proceeding.
Greater Occipital Neuralgia
There are many reasons for headache and many reasons for headache at the back of the head. Tension headache inclusive of neck pain that refers pain to the head is exceptionally common. A much less common reason for pain at the back of the head is greater occipital neuralgia. The greater occipital nerve is a branch of the nerve coming from the C2 vertebra. It arises close to the base of the skull, travels through the dense muscle at the base of the head and neck before becoming more superficial as it travels under the scalp to the top of the head at the back. There is a greater occipital nerve on each side of the head, and there are nerves of a similar derivation that go to the ear region. Pain arising from the greater occipital nerve, which is of a neuropathic nature (often burning) in a distribution of the greater occipital nerve, can be considered to be possibly greater occipital neuralgia.
Clinical examination is to rule out any tumours of that nerve, as this is a rare cause of the condition. Often in that case it is a one sided discomfort. Other causes can cause bilateral concern. Treatments revolve around medications and guided injections in the main; though other considerations are pulsed radiofrequency and peripheral nerve stimulation (see section on pain).
In the absence of these modalities working, it is only very rare that surgery is required. Surgery is generally required when a compression can be identified, or a tumour has been located. Both are rare occurrences.
Nerve tumours in the peripheral neurological system are not common. They can be as part of a clinical syndrome, such as neurofibromatosis. They are more common to be singular. These tumours can arise from the peripheral nerves origin in the spinal cord all the way through to the end organ.
Schwannoma and neurofibromas can look and behave very similarly but are manifestly different. Schwannomas arise from the lining of the nerve and often are attached to the edge of the nerve itself whereas neurofibromas are more classically an expansion of the nerve that arises within the nerve itself. Both are benign. Both a schwannoma and neurofibroma can cause nerve dysfunction. This can be caused due to intrinsic disruption of the neural fibres in the case of the neurofibroma or compression of the neural fibres in either case. Local pain is perhaps the most common symptom and also the feeling of a lump that may change in size over the course of time, though usually slowly.
The diagnosis can often be made on the basis of imaging and clinical examination alone in association with patient history. If surgical intervention is required due to symptoms or other concerns, an incomplete removal is often undertaken followed by clinical and radiological review to preserve neurological function.
A schwannoma is much more likely to be able to be removed due to its anatomical features than a neurofibroma, which is more diffusely associated with the surrounding nerve.
Occasionally a plexiform neurofibroma may arise. This is where multiple neurofibromas form in a cluster and can be quite uncomfortable if they are in a superficial area. They are difficult entities to treat. Not all plexiform neurofibromas are amenable to treatment surgically or otherwise.
A neuroma is where most usually a nerve has been injured, and it has tried to repair of its own accord. That repair has not been successful, and a small tuft of nerve tissue has formed that is not of a functional nature. This can be very painful. These nerve fibres can transmit sensations such as light touch as pain. It may require certain management of which surgical removal of the neuroma is one. Whenever a small cutaneous nerve is identified and needs to be divided at the time of surgery it is important, and good practice, to ensure that the nerve is tied off such that a neuroma does not form. You may ask the question why a nerve needs to be divided at surgery. Most small nerves to the skin will regenerate slowly over time, may not cause any symptoms whatsoever and at worse cause areas of numbness. Surgical incisions need to be in certain places to access the underlying tissues, and it is sometimes unavoidable to divide some of these small nerves.
It is also the case that nerves can be damaged during trauma generally. Trauma to any bodily part where a nerve is injured can secondarily manifest as a neuroma and subsequently give significant symptoms. There are of course other treatments other than surgery for neuromas, but these are not always effective.
Tumours otherwise can arise within nerves or tumours can jump to nerves in rare occurrences. Largely these are very unusual circumstances. Usually there is some concern as to what the diagnosis may be, and the symptoms can be many and varied.
Surgery directly on a nerve, just like surgery directly on the spinal cord or the brain itself, is a delicate undertaking. A biopsy alone may be sufficient or appropriate to ensure that the diagnosis is made, and the nerve itself is not rendered dysfunctional. On some occasions, the nerve itself can be spared and the tumour removed in its entirety, this is often something that needs to be decided at the time of surgery.