What is Lateral Recess Stenosis?
In medical terms, Stenosis is a ‘narrowing’ of any tubular vessel or structural passageway within the body. Lateral Recess Stenosis is a condition where the narrowing reduces the available space within the exit doorway (foramen) of the spinal canal. This may be caused by arthritic overgrowth of the facet joints, degeneration of the disc with loss of tension in the disc and loss of disc height, overriding of the facet joints with concurrent bulging of the disc. The loss of height and tension in the disc allows for “sloppy” movement of one vertebra upon another. The orientation of the facet joints and the stretching of the capsule allows one vertebra to slide consistently forwards or backwards upon the lower vertebra thus distorting the foraminal doorway. The resultant distortion and loss of space in the foramen sometimes with additional bone spurs arising from the vertebral margin or facet joint can cause squeezing or pinching of the nerve roots as they exit the spine through the doorway.
What are the symptoms?
Patient feedback during sedation surgery has taught us that superficial pressure or irritation of the nerve causes back pain whilst deeper pressure causes pain perceived to travel further into the limb. In the lower spine this pain radiates to the buttock, groin, thigh, lower leg and foot. The typical clinical pattern of stenosis is that of progressively worsening pain and then dysfunction or weakness in the leg(s). with either symptom aggravated and then halting walking. The symptoms may include heaviness, leadenness or weakness affecting one or both legs so that the sufferer may believe the problems are muscle-related. Specifically, weakness in the thighs, hamstrings or calves, weakness on push off and ‘foot drop’ (weakness in lifting up the toes) may be experienced and the condition can progress to wasting of the legs. Furthermore, the walking distance becomes reduced in a process known as ‘Claudication’ caused by starvation of blood supply to the nerves. When walking ceases, the blood supply recovers and the symptoms subside. The condition can deteriorate quite rapidly leading the patient to a wheelchair existence.
Just to add to the diagnostic conundrum, lateral recess stenosis can present just as low back pain or as buttock pain or as sciatica.
What is wrong with conventional diagnosis?
The main difficulty in diagnosing this condition is that many features are misleading. Indeed, Lateral Recess Stenosis and Axial Stenosis (narrowing of the spinal canal itself – see appropriate page) are related conditions and the pathology frequently occurs together. It is important to distinguish between the two at an early stage because the treatment pathway can be different. In fact, Axial Stenosis is generally over-diagnosed, because the pathology can be more readily seen on MRI and CAT scans.
A degree of lateral recess stenosis can be present on the scans for many years in the absence of symptoms but then a provocative incident activates the symptoms which gradually crescendo.. In short, Axial Stenosis may be a prominent feature on the scans, but it may be less contributory of the presenting symptoms than lateral recess stenosis. This is because lateral recess stenosis may be caused by postural impaction or squeezing of the nerve when walking and in part amplified by the scarring in the foramen which is responsible for damming the flow of venous blood up the foramen. This in turn leads to engorgement of the vessels and damming of the arterial blood supply to the nerve. The nerve itself is often irritated and swollen by the nipping movements of the facet joint, bulging disc and scarring over the nerve or scarring tethering the nerve onto the disc, vertebra or bone spurs. This swelling further reduces the available space for the free movement of the blood supply. The problem is that the true impact of these features is difficult to determine on current MRI scans. Dynamic CT scans can detect the abnormal micromovements on occasions but again cannot certainly indicate which segment is responsible for the lateral recess stenosis as several levels may exhibit similar features.
Normally the pathology of lateral recess stenosis will be facet joint overgrowth, reduction of foraminal volume caused by loss of disc height and or distortion of the foraminal space by slippage of one vertebra upon another. But here again the severity may be enhanced by a foraminal disc protrusion or high intensity zone or bone spur formation.
Is a more accurate diagnosis possible?
It is important to remember that Lateral Recess Stenosis and Axial Stenosis are related conditions and frequently co-exist in different proportions. Lateral Recess Stenosis commonly occurs in the lumbar spine region of the lower back at vertebral levels L3/4, L4/5 & L5/S1, and in the neck at vertebral levels C5/6 & C6/7. Axial Stenosis however commonly occurs in the lumbar spine region of the lower back at vertebral levels L2/3 < L3/4 & L4/5 and in the neck at vertebral levels C4/5 & C5/6 > C6/7. The significant benefit offered by aware state diagnosis (see below) is that it enables the surgeon to accurately target the problem area and thus deliver specific treatment focused only upon that problem area as the other pathology seen on the scans may be a “Red Herring”.
How can the diagnosis be confirmed?
This can be achieved by the use of spinal foraminal probing of the nerve, the contents of the foramen and the epidural space to determine contributory levels. Foraminal probing is at least twice as effective as discography in detecting the source of pain. Hydraulic discography can be used to determine levels causing compression of the nerve exiting the spinal space. This procedure enables the surgeon to re-tension the disc and ligaments, restore disc height, realign the facet joints and restore the volume of the foramen at the suspected level for a short period. This is particularly useful where the symptoms of weakness, pins and needles, numbness or hypersensitivity or ”Leadenness” predominate and are caused by activity or walking and pain is an intermittent or minor symptom.
Hydraulic Discography techniques involve the injection of an X-ray visible liquid into the disc, raising the disc height and open up the ‘Foramen’ or spinal spaces effectively liberating the nerve temporarily.
Where pain rather than compression is the predominant symptom then insertion of anaesthetic or steroid in to the disc (Differential Discography) can be used to distinguish the role played by each level in the symptom complex. The steroids or anaesthetic agent can be instilled by means of a CT Guided Nerve Root Block or more rarely their injection into the target discs. This can be particularly valuable in cases with a concurrent high intensity zone. If the symptoms are significantly modified for 5 hours, then the causal segment is that into which anaesthetic was instilled. If the symptoms are temporarily worsened for 48 hours and then eased for 7 days or more then the causal segment is the one containing the steroids. If these studies transiently reverse the symptoms, then the specific causal segment can be identified without having to open the back at several levels. In cases of failed back surgery, this will demonstrate whether or not the original surgery addressed the causal segment or whether it addressed the correct level but failed to treat the pathology adequately.
What is wrong with conventional surgery?
Conventional surgical treatments offer a wide range of alternatives; all of which have a place but are not necessarily efficacious or optimal. Please note however that this is a general guide and that individual cases should be correctly assessed by a competent spinal surgeon in order to decide upon the most appropriate treatment. The following brief guide is included so that the lay person may gain a basic understanding of the conventional options they may be offered:
- Laminectomy is the removal of substantial areas of bone from the ‘Lamina’ or vertebral arch. It releases space within the spinal column but also removes muscle purchase points and can lead to extensive scarring on local and related tissues and nerves within the spine. In many cases, it can also lead to increased spinal “instability” and the need for spinal fusion at a later date.
- Laminoplasty is a procedure whereby the Laminar arch is split apart to increase the volume of available space. The resultant gap or split is maintained by bone grafting or by the insertion of tissue or implants. These techniques fail to provide sufficient access & liberation of the nerves throughout the foramen.
- Medial Facetectomy is the removal of the inner part of the facet joint on either side of the vertebrae to preserve as much of the Laminar arch as possible. This may destabilise the facet joint and lead “instability” and the need for a fusion procedure.
- Endoscopic Medial Facetectomy is a similar procedure but is facilitated by the insertion of an endoscope between the laminae. However, it offers only limited access as these techniques fail to provide sufficient access & liberation of the nerves laterally through the foramen.
- Interspinous Spacers can be inserted using keyhole surgery rrin the back of the spine between the spinous processes in order to restore some of the original posterior spacing of the vertebrae in cases where disc height has been lost through degeneration. Often, these spacers take the form of a cushion or a metal implant. By spreading the spinous processes this attempts to restore some segmental height, re-tension the spine and enlarge the foramen. The outcome depends in part upon the amount of residual disc that is present and may alter the posture of the lower lumbar spine and cannot be applied at the L5/S1 level and should not be used in patients with scoliosis. The technique will fail to ease symptoms if the nerve is significantly tethered in the foramen.
- Intervertebral Vertebral Fusion using pedicle screws and bone graft or cages in the disc space can be used to restore disc height and immobilise the segment. But here again this is only effective if it releases the compression and tethering of the nerve throughout the foramen. The technique requires successful graft incorporation and results in strain overload of the adjacent discs.
All of the above use ‘posterior’ approaches to the spine. The major problem with these techniques (with the possible exception of the interspinous spacers) is that they cannot adequately clear the foramen of compression as they only permit removal of material from inner areas of the foramen and it is within the lateral areas that the greatest need exists. This means that the surgeon may address too many levels in an ‘overkill’ operation and still not adequately solve the problem.
What is aware state diagnosis?
Conventionally the cause of the pain is diagnosed from the pattern of the pain and static MRI and CT scans but these techniques are inaccurate. However, the causal pain sources can now be accurately defined through aware state surgical examination, during which the surgeon seeks to replicate the pain by gentle foraminal probing at several levels. When this provokes a response, matching the predominant presenting symptoms then the surgeon is assured of the causal segment and can carry out discography to determine the distribution of degeneration in the disc and the presence of leakage and proceed to endoscopic treatment of the foraminal contents with the patient protected by circulating intravenous painkillers.
Sometimes, when the response is only partially akin to the presenting symptoms or when the response is at more than one spinal level, additional techniques such as Differential Discography are used. These techniques enable the surgeon to determine the relative importance of each site in the totality of the patient’s pain and condition. In Differential Discography, the steroid or anaesthetic agents can be injected into the target discs. Steroids are placed into the disc which appears to be contributor of pain. This technique can be particularly valuable in cases with a concurrent high intensity zone. If the symptoms are significantly modified for 5 hours, then the causal segment is that into which anaesthetic was instilled. If the symptoms are temporarily worsened for 48 hours and then eased for 7 days or more then the causal segment is the one containing the steroids.
Why is this better than conventional diagnosis?
This ‘live’ approach to diagnosis means that causes of pain can be defined and ultimately confirmed. It means that misdiagnosis due to strange nerve anatomy can be avoided. Subsequent endoscopic examination with the patient awake then leads the surgeon to the precise source of pain within that specified intervertebral level. This is in complete contrast to conventional diagnostic techniques which rely upon pre-operative ‘guesstimation’ based upon X-rays, MRI scans and CAT scans and often results in the “overkill” of multiple level surgery performed to attempt a treatment “catch all”.
How is Lateral Recess Stenosis treated minimally invasively?
Following aware state diagnosis, the patient is treated using Transforaminal Endoscopic Lumbar Decompression & Foraminoplasty. This facilitates the accurate clearance of scarring around the nerves in the foramen. At the same time, the nerve can be liberated from tethering to the disc, the facet joint margin and specific ligaments (Superior Foraminal Ligament) and from bone spurs arising from the facet joint margin or vertebral body margin by lasing, manual or power reaming, tissue and bone removal. After this, any bulging disc areas can be removed and shrunk by Laser Disc Decompression and Annuloplasty. This enables the surgeon to open up the narrowest portion of the foramen, termed the isthmus and restore free pulsatility and movement to the nerve. At the same time, the surgeon can seal leaks and tears in the disc wall which may be contributing to the irritation of the nerve in the foramen.
Why is this better than conventional surgery?
The benefit of Transforaminal Endoscopic Lumbar Decompression and Foraminoplasty is that it enables the surgeon to treat the condition specifically, precisely and with minimum collateral damage to tissues, reduced risk to the patient and enhanced long-term outcome. Foraminoplasty preserves natural segmental movement and muscular support and holds open the deployment of more advanced techniques as these evolve in the future. This is in contrast to conventional surgery, especially where multi-level conditions are suspected. Under these circumstances, the surgeon will treat all the involved levels using ‘overkill’ multilevel surgery with problems including blood loss, potential nerve and tissue damage, extended post-operative care and unnecessarily operating on non-causal levels. Unlike conventional surgery, minimally invasive techniques can be used in all age groups and offer treatment for the frail, the infirm and the elderly because they avoid the use of General Anaesthesia. They also open up the opportunity to treat long term symptoms where the diagnosis is in question and where the patient would otherwise be referred for palliative Chronic Pain Management.
What proof is there of successful treatment?
Aware State Diagnosis and ELDF Surgery are delivering encouraging results in well over 80% of patients when reviewed 2-4 years later1, and 70% at 10 years2 later.Aware State Diagnosis and ELDF Surgery are delivering encouraging results in well over 80% of patients when reviewed 2-4 years later, and 70% at 10 years later.
References
1. Knight MTN, Goswami A, Patko JT, et al. Endoscopic foraminoplasty: a prospective study on 250 consecutive patients with independent evaluation. J Clin Laser Med Surg 2001;19(2):73-81.
2. Knight MT, Jago I, Norris C, et al. Transforaminal endoscopic lumbar decompression & foraminoplasty: a 10 year prospective survivability outcome study of the treatment of foraminal stenosis and failed back surgery. Int J Spine Surg 2014;8 doi: 10.14444/1021
