A herniated disc is a localized displacement of disc material beyond the normal margins of the intervertebral space. The pain pathway originates from the pinching of the nerve root by the herniated disc, which in turn can cause nerve damage through both mechanical and chemical pathways.
Mechanically, nerve compression probably leads to localized ischemia and nerve damage. Equally important is the chemical cascade triggered by the nucleus pulposus at the local level.
This article will look at herniated discs in the cervical, thoracic and lumbar spine, since each one has different intervention thresholds.
| Cervical disc herniation |
Cervical disc herniation (CDH) is a common source of cervical radiculopathy , with an annual incidence of 18.6 per 100,000 and a peak of presentation in the sixth decade of life. The etiology of CDH is multifactorial and risk factors include male sex, smoking, heavy lifting, and occupations that involve operating vibrating equipment.
With respect to pathologic anatomy, the herniated disc may compress the protruding nerve root intraforaminally as it traverses the neuroforamen or, more commonly, posterolaterally as it exits the spinal cord.
Most patients with symptomatic CDH and radiculopathy report severe pain in the neck and arm.
Arm pain typically follows a myotomal pattern, while sensory symptoms (eg, burning, tingling) follow a dermatomal distribution.
These radicular symptoms may also be associated with reflex changes and motor weakness of the upper extremity. Epidemiological studies have shown that the C7 root (C6-7 herniation) is the most commonly affected, followed by the C6 (C5-6 herniation) and C8 (C7-T1 herniation) nerve roots.
The natural history of CDH with radiculopathy is generally considered favorable ; however, high-quality studies are lacking. A recent systematic review found that substantial improvements in symptoms appear within four to six months, with time to complete recovery spanning 24 to 36 months in most patients. In the long term, a small proportion of those affected appeared to have residual impairments, such as pain and activity limitations; however, none presented progressive neurological deficits or developed myelopathy.
Nonsurgical treatment is the initial treatment of choice in most patients with CDH and radiculopathy.
It consists of a number of different modalities including immobilization, physical therapy, manipulation, traction, medication, and cervical steroid injection. Good to excellent results have been reported in up to 90% of patients with nonsurgical treatment of cervical radiculopathy.
There are no clearly recognized indications for surgery in CDH patients with radiculopathy . Signs or symptoms that may warrant early surgical intervention include progressive neurological deficits or signs of myelopathy. A trial of nonsurgical management is usually attempted in the absence of these signs. Despite this, the duration of nonsurgical treatment that should be attempted is unclear.
| Thoracic disc herniation |
Symptomatic thoracic disc herniation (TDH) is a rare condition that affects 1 in 1,000 to 1 in 1,000,000 people in the general population, and accounts for 0.1% to 3% of all spinal disc herniations. . Asymptomatic HDT is more common and is discovered incidentally in 11% to 37% of imaging studies. The peak occurrence of HDT is in adults between 30 and 50 years old, with equal distribution between sexes. The etiology is multifactorial and recognized risk factors are a history of trauma, Scheuermann’s disease, smoking, and being a sedentary worker.
In 75% of cases, the HDT is located below the T7-T8 disc, with the T11-T12 disc being the most vulnerable, and only 4% of cases are located above T3-T4. The distinguishing feature of TDH is the high frequency (42%) of calcification or even ossification of the disc. HDT can also have a very large volume and is labeled as giant when it occupies more than 40% of the spinal canal on computed tomography (CT) or magnetic resonance imaging (MRI).
These giant herniated discs are predominantly calcified (76 to 95% of all giant herniated thoracic discs), and due to their bulky and calcified nature, the risk of intradural extension is 15 to 70%. The thoracic spinal cord is particularly vulnerable due to thoracic kyphosis that pushes the cord against the disc, the dentate ligament that reduces spinal mobility, the large diameter of the thoracic cord relative to the smaller diameter of the spinal canal, and the area of malnutrition. vascularized area.
The onset of HDT is usually gradual, and the main clinical symptom is thoracic back pain, which is present in 92% of cases. Radicular symptoms (intercostal or abdominal radicular pain) may also be present, followed by progressive myelopathy with sensory disturbance, motor deficits in the lower extremities, ataxia, and bladder symptoms. Calcified HDT occurs in 70% to 95% of cases with signs of myelopathy . Due to the slow progression and atypical symptoms, the average time from the onset of the first symptoms to the diagnosis of HDT is 15 months. However, in 11% of cases the onset can be sudden, post-traumatic, with rapid appearance of neurological deficits (paraparesis, Brown-Sequard syndrome, bladder-sphincter disorders and paraplegia).
Most patients will respond favorably to nonsurgical treatment and observation , especially in cases of isolated back pain or isolated radicular pain due to intercostal nerve root entrapment.
Surgical treatment of TDH is indicated if patients fail conservative measures and/or have worsening neurological symptoms.
Most surgeons recommend surgical treatment for giant herniated thoracic discs (HTDs) and giant calcified HTDs because these HTDs often lead to the development of myelopathy.
Some also consider surgical treatment in certain cases where patients with signs of myelopathy are evident on MRI, even in the absence of neurological symptoms. These patients may benefit from surgical treatment before symptoms appear or, worse, become irreversible.
| lumbar disc herniation |
Lumbar disc herniation (LHD) is the most common cause of sciatica and affects between 1% and 5% of the population annually. The main signs and symptoms include radicular pain, sensory abnormalities, and weakness in the distribution of one or more lumbosacral nerve roots. Focal paresis, restricted trunk flexion, and increased pain in the legs when sitting or straining, coughing, and sneezing are also indicative.
The absolute indications for urgent surgical treatment are progressive and significant weakness of the lower limbs or cauda equina syndrome.
However, in the absence of these symptoms, the first-line treatment for LDH is nonsurgical and may consist of rest, drug therapy, physical therapy, and transforaminal or epidural steroid injections.
For symptoms that are resistant to initial conservative treatments, continued conservative care or lumbar discectomy may be considered to remove herniated disc material. Over the past three decades, several RCTs and prospective cohort studies have shown that discectomy provides faster pain relief and/or greater disability recovery and patient satisfaction compared with nonsurgical care.
A recent systematic review and meta-analysis examined 11 studies (3232 patients) that compared discectomy versus nonsurgical care. Discectomy was found to be more effective than non-surgical care in significantly reducing leg and back pain.
Based on the evidence, the International Society for the Advancement of Spine Surgery published a policy on the treatment of patients with symptomatic HDL who do not improve with nonsurgical care. Clinical indications for surgical treatment may be: patients with clinical signs and symptoms associated with HDL, with imaging confirmation of HDL consistent with clinical findings, and lack of improvement after six weeks of conservative treatment.
A recent systematic review evaluated preoperative predictors associated with a positive or negative postoperative clinical outcome. It found that more severe leg pain, better mental health status, shorter duration of symptoms, and younger age are associated with a positive outcome, and negative outcomes are linked to an intact annulus fibrosus, longer duration of sick leave, workers’ compensation and increased severity. of baseline symptoms.
