Intervertebral Disc Herniation and Sciatica

Anatomy of the Spinal Column

The vertebral column is made up of about 32 to 34 vertebrae,7 cervical (C),12 thoracic(T),5 lumbar(L),5 sacral(S) that make up the sacrum and 3 to 5 fused coccygeal.Between the bodies of vertebrae the intervertebral disks are present.These discs are made of the annulus fibrosis that surrounds the gel like nucleus pulposus.Within the vertebral foramen is the spinal cord and the spinal nerves exit on each side through the intervertebral foramina.

DISC HERNIATION

With disc herniation the nucleus pulposus extrudes through a tear at the annulus compressing the nerve root(the so called “ pinched nerve” ) or spinal cord.Stress factors like heavy weight bearing with poor lifting posture and sudden rotational or twisting motion as well as wear and tear due to aging are the usual causes.Prevention is aimed at limiting these stress factors and exercising to strengthen the back muscles(eg.paravertebral muscles) that support the spinal column.Herniated discs occur most often in the lumbar area(eg.L5-S1) and less often in the cervical region.When the L5 or S1 root is impinged “sciatica” occurs.

Note A central herniated disc compressing the nerve roots of the conus medularis may give rise to the “cauda equina syndrome” this needs immediate surgical intervention to prevent bowel and bladder dysfunction.

Sciatica

Symptoms

Pain with muscle weakness,numbness,tingling and reflex loss are present.(see Table 1)The pain radiates from the back to the leg ,calf and foot with predominate leg pain.Restricted back movement and occasional muscle spasms are also experienced.

Table 1 Herniated disc with nerve root compression.

1)Herniated disc level L4-L5

Root L5

Muscle weakness of anterior tibialis(dorsiflexion) and extensor hallus longus(hallus extension)

Sensory deficit of dorsal foot and lateral leg.

Reflex loss of medial hamstrings.

2)Herniated disc level L5-S1

Root S1

Muscle weakness of gastrocnemius and soleus(plantar flexion).

Sensory deficit of lateral foot.

Reflex loss of ankle jerk.

Clinical Evaluation

Pain during the straight leg raising(SLR) test and the crossed SLR test are positive indicators of lumbar disc herniation.Refex loss is also noted eg. a diminished or absent ankle jerk

Diagnostic Tests

Radiography ,electromyography test (EMG),CT and MRI of the spine

Treatment

Benefits can be obtained with a balance of rest and activity(including physiotherapy), analgesics, anti-inflammatory drugs (NSAIDs ,corticosteroids)and muscle relaxants.(see Medications Table 2)These measures after a few months will usually reduce the hernia relieving the symptoms Surgical intervention eg. discectomy is reserved for severe cases that do not improve, have motor disability and excruciating pain.

Medications

Table 2 Drugs used to treat herniated discs.

Analgesics(for pain)eg.acetoaminophen

narcotic eg.codeine(for severe pain)

Neuralgia; gabapentin,tramadol

Anti-inflammatory drugs

1) Non-Steroidal Anti-inflammatory Drugs(NSAIDs); aspirin,ibuprofen

2)Corticosteroids(oral or by epidural injection); dexmethasone,prednisone

Muscle relaxants(for muscle spasm); cyclobenzaprine ,methocarbamol