Lumbar radicular pain or sciatica, as most commonly known, is defined as pain induced by irritation, inflammation, pressure or injury of a lumbar spinal nerve. The pain is located in the ipsilateral lower extremity and is characterized as a sharp, stabbing, electric shock sensation.
Lumbar radicular pain has to be differentiated from lumbar radiculopathy. In radiculopathy there is sensory or/and motor loss. These two entities should not be confused. Radicular pain is a symptom induced by ectopic excitation, while radiculopathy involves also neurological processes, such as sensory or/and motor changes. The two disorders may co-exist and have the same causes, e.g. intervertebral foraminal stenosis, disc herniation, infection and other inflammatory conditions. There is also the case of patients initially suffering from radiculitis (nerve root inflammation) that later on transforms into radiculopathy.
The annual prevalence in the general population ranges from 9,9%-25% (4) and the condition is described as “lumbar radicular pain radiating to the lower extremity below the knee”. Sciatica is the most commonly occurring neuropathic pain in the general population. The highest predispository risk factors are female gender, obesity, smoking, low back pain history, stress, depression, jobs/tasks requiring long-hour standing and frequent bending, dystocia (difficult labor), heavy weight lifting and exposure of spine to vibrations. (7)
In 60% of patients, sciatica symptoms partially or fully subside within 12 weeks from the onset of symptoms. However, some 30% of patients keep suffering 3 months to 1 year later. The female population with chronic sciatica have worse outcome compared to men.
Lumbar Radiculopathy (Sciatica)
The most common cause of acute and subacute (6-12 weeks) lumbar radicular pain is lumbar disc herniation.
The most common cause of chronic (over 3 months) lumbar radicular pain is the formation of adhesions around some nerve root and its chronic irritation. Adhesions may form as a result of acute inflammation due to disc herniation or after spine surgery.
Other causes of chronic radicular pain may be: spinal canal stenosis, intervertebral foraminal stenosis (at the point where the nerve root exits), spondylolysthesis, piriformis muscle syndrome and radiculitis following radiation or chemotherapy.
Lumbar radicular pain is characterised as sharp, burning, compressive and penetrating pain along the affected nerve pathway. The herniation-induced pain aggravates by bending, sitting, coughing and exerting pressure on the intervetebral disc, while it improves by lying down and, probably, walking. (7) On the contrary, the pain caused by spinal canal stenosis worsens with walking and relieves with bending. (10) In addition, spinal stenosis patients develop paresthesia on the ipsilateral dermatome.
Patients suffering from chronic sciatica due to nerve root entrapment, as a result of adhesions from a previous acute inflammation or after spine surgery, very often complain about experiencing pain after sitting for a few minutes on the chair or in the car while driving. They also report that they are in pain and “get blocked” for a few minutes when getting up from the sitting position and their condition improves with walking. They feel uneasy when lying on the back and have difficulty in sleeping well.
The diagnosis of the disease is based on the history, clinical examination and supplementary tests. The classical neurological examination includes sensory, motor and reflex examination.
The most commonly used test is the Lasegue test. The patient lies on the back and the clinician elevates the affected leg with the knee in full extension and the other leg stretched on the examination bed. Should there be pain with a leg-bed angle less than 60o when the leg elevated passively, then it is very likely that there is disc herniation and radicular inflammation. In cases of chronic radiculitis, the Lasegue test is usually negative.
RED FLAG SIGNS AND SYMPTOMS
1. First symptoms occurring at the age below 20 and over 55 y.o.
2. Constant and gradually aggravating back pain.
3. History of malignancy
4. Long-term use of corticosteroids
5. Drug abuse, immunosuppression, HIV virus
6. Unjustified body weight loss
7. Neurological symptoms, such as muscle weakness, sensory loss, urinary or/and defecation disorders, cauda equina syndrome
When the above symptoms occur, full and thorough investigation is essential to rule out any severe and threatening pathology and take the timely decision for surgery, when and if needed.
The most commonly used supplementary examinations are radiological evaluation, electrophysiological testing and diagnostic selective nerve root blocks. Given that 60-80% of sciatica cases recover within 6-12 weeks of conservative treatment (not necessarily with reduction of herniation size), supplementary examinations are to be conducted only when there is suspicion of a more severe primary pathology. Radiological examinations are used mainly for ruling out other severe primary pathology, such as tumor, infection and vertebral fracture. When pain persists even three months later, MRI is the diagnostic modality of choice.
CT scan provides good information on bone structures but there are limitations with regard to soft tissues. MRI is the diagnostic modality of choice, showing morphological changes taking place in intervertebral discs, spinal cord, nerve roots and surrounding soft tissues. (14) The diagnosis should not be based only on radiological findings, for studies have shown that approximately 30% of patients with MRI findings are asymptomatic. (16)When clinical and radiological findings match, then it is much easier to make proper diagnosis. (17,18,19)
Electrophysiological tests include nerve conduction and electromyography (EMG). These are useful when there is suspicion for nerve defect but they do not provide any particular information regarding pain. They are also useful for making differential diagnosis between peripheral neuropathy (e.g. piriformis muscle syndrome) and lumbar spine radiculitis. (24)
DIAGNOSTIC SELECTIVE NERVE ROOT BLOCKS
These are applied when there is doubt about which specific nerve root causes the pain. With this technique, the nerve root is blocked with 0,5ml local anaesthetic and then the patient has to report whether his/her pain impoves at least by 50%. Each suspicious nerve root is blocked separately in different sessions until the one causing the pain is identified.(23,27)
Α. CONSERVATIVE TREATMENT
For the treatment of acute and subacute condition, anti-inflammatory drugs are recommended but only for a short period, to avoid potential severe cardiovascular and gastrointestinal complications that might occur.(33,34)
The chronic condition is treated with drugs administered in neuropathic pain, such as antidepressants (amitriptyline), antiepileptics (carbamazepine, oxcarbazepine, gabapentin, pregabalin).
In case of resistant pain to therapy, light opioids may be added, such as codeine and tramadol.
Multifactorial rehabilitation is recommended with physical therapy and chiropractic care.
In case pain persists or the patient does not tolerate the potential adverse events of drugs s/he should be taking on a long-term basis and before deciding to administer any strong opioids, it is recommended to apply interventional pain therapies.
Before starting pharmaceutical treatment on a long-term basis, many patients choose a minimally invasive therapy which intervenes straight to the origin of pain, in order to avoid chronic addiction to drugs with several side effects. In many cases, the ideal treatment is achieved with combination of pharmacotherapy and interventional techniques.
1. Epidural Corticosteroid Injection(51-56)
When the disease is in its acute or subacute form, lumbar epidural corticosteroid injection is indicated. The technique used is the posterior translaminar approach and transforaminal epidural injection. The transforaminal epidural injection is more effective than the classical tranlaminar approach because the infusion of the theraupeutic drug solution is selectively targeted to the affected nerve root. Systematic research worldwide leads to the conclusion that the lumbar epidural corticosteroid injection is significantly effective in the treatment of acute and subacute lumbar radicular pain and should always be applied before surgery decision.
2. Neuroplasty therapy (adhesiolysis) with Racz catheter(70-83)
When the disease is in its chronic form -as usually happens after spine surgery or following the acute and subacute phase of radiculitis induced by disc herniation that had been undertreated with conservative therapy- neuroplasty (adhesiolysis) with Racz catheter is indicated.
The American Society of Interventional Pain Physicians (ASIPP) published evidence-based guidelines for interventional techniques in the management of chronic spinal pain.
According to these guidelines, there is strong evidence indicating the efficacy of neuroplasty therapy with corticosteroids in the short and long-term control of pain in refractory radiculopathy and neuropathic spinal pain.
3. Pulsed Radiofrequency Therapy (PRF)(66,67,68,69)
In a retrospective study, Pulsed Radiofrequency was applied on lumbar dorsal root ganglia (LDRG) in a group of 13 patients who had been planned to be operated for their sciatica. Out of them, only one finally underwent discectomy and another one had spine fusion one year following the radiofrequency therapy without him experiencing radicular pain at the time of the operation.
In another retrospective study, pulsed radiofrequency was applied in sciatica patients following herniation disc, spinal canal stenosis and unsuccesful back surgery. Significant improvement in pain and analgesic consumption was observed in patients with disc herniation and spinal canal stenosis but not to the ones who had previously been operated in the back.
4. Spinal Cord Stimulation(84,85,86)
It is a neuromodulatory therapy, which is used in case all other less invasive methods fail. Its efficacy in treating chronic resistant neuropathic pain is significant. According to randomized controlled studies, it is strongly supported that Spinal Cord Stimulation Therapy is more effective in the treatment of sciatica after spine surgery compared to revision surgery.
Surgery is indicated in case of severe compression of cauda equina (last part of spinal cord) resulting in the cauda equina syndrome (CES) with permanent severe irreversible neurological defects. In a randomized study, comparison was made between surgical and conservative treatment and it was found that there was substantial improvement in pain 3 months postoperatively. However, one year later there was no difference between the two patient groups. A small randomized study demonstrated that there are no differences in the neurologic outcome between patients who were treated surgically or conservatively. Thus, surgical operation should be limited only to those patients whose neurological condition requires immediate nerve decompression.
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