Spinal cord compression overview

# Overview
Spinal cord compression develops when the spinal cord is compressed by bone fragments from a vertebral fracture, a tumor, abscess, ruptured intervertebral disc or other lesions. It is regarded as a medical emergency independent of its cause and requires prompt diagnosis and treatment to prevent long-term disability due to irreversible spinal cord injury.

# Pathophysiology
The spinal cord extends from the foramen magnum down to the level of the first and second lumbar vertebrae. The cord is protected by the vertebral column, which is mobile and allows for movement of the spine. It is enclosed by the dura mater and the vessels supplying it. The spinal cord and nerve roots depend on a constant blood supply to perform axonal signaling. Conditions that interfere, either directly or indirectly, with the blood supply will cause malfunction of the transmission pathway. Injury to the spinal cord or nerve roots arises from direct trauma, compression by bone fragments, hematoma, or disc herniation or ischemia. The tissue responses by gliosis, demyelination, and axonal loss. This results in injury to the white matter (myelinated tracts) and the gray matter (cell bodies) in the cord with loss of sensory reflexes (pinprick, joint position sense, vibration, hot/cold, pressure) and motor function.

# Causes
Common causes of spinal cord compression include trauma, primary or metastatic spinal tumor, intervertebral disk herniation, epidural abscess, and epidural hematoma. 

# Differentiating spinal cord compression from other diseases
Acute spinal cord compression presents with sudden onset of paralysis along with back pain, it must be differentiated from other diseases with similar presentation such as muscle weakness and back pain. Transverse myelitis, GBS (Gullian-Barrie syndrome), HIV-myopathy, diabetic neuropathy, multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS) and peripheral neuropathies are some of the diseases to be considered in the differential.

# Epidemiology and Demographics
Trauma is the main cause of acute spinal cord compression followed by compression due to metastasis. The annual incidence rates of spinal cord compression due to trauma is estimated to be approximately 8-246 cases per 100,000 population. Men are more commonly affected with spinal cord compression than females. The male to female ratio is approximately 4 to 1.

# Risk Factors
The most important risk factors in the development of spinal cord compression are cervical spondylosis, atlantoaxial instability, congenital conditions (tethered cord), osteoporosis, ankylosing spondylitis, and rheumatoid arthritis with cervical spine involvement.

# Natural History, Complications and Prognosis
Spinal cord compression is an emergency condition that needs immediate treatment. If left untreated it leads to permanent damage to nerve roots and paralysis. Complications that can develop as a result of spinal cord compression include pressure ulcers, deep vein thrombosis, urinary tract infections, MRSA infection, pulmonary embolism. Prognosis is poor if the syndrome is complete (quadriparesis and with no sensory preservation), and recovery is less than 5%. The mortality rate for 1 year after injury in patients with complete lesions can be 100%. On the contrary, the prognosis is much better for the incomplete cord syndromes with some preserved sensory function with recovery rate greater than 50%.

# Diagnosis

## History and Symptoms
Back pain is the most common presenting symptom in almost all acute cases of spinal cord compression. Symptoms of spinal cord compression depend upon the anatomic level involved. All cases of spinal cord compression present with sensory, motor and autonomic dysfunction. Sensory symptoms include altered sensation below a certain level (e.g. pinprick, touch, vibration, temperature), hemi-sensory loss. Motor symptoms include hemiplegia or hemiparesis (sparing the face), paraplegia or paraparesis, tetraplegia or tetraparesis. Autonomic symptoms include constipation, urinary retention, dizziness (due to hypotension), cold, shivering, and drowsiness (due to hypothermia), erectile dysfunction, abdominal pain and distension (due to ileus), and syncope (due to bradycardia).

## Physical Examination
The most significant physical examination findings in acute cases is point tenderness of back. Other physical examination findings include paralysis of limbs below the level of compression, decreased sensation below the level of compression, Lhermitte's sign (intermittent shooting electrical sensation), hyperreflexia, and upward plantar reflex (Babinski sign).

## Laboratory Findings
Spinal cord compression is diagnosed based on clinical symptoms and imaging studies. Laboratory studies play a minimal role in diagnosing spinal cord compression expect in assessing the patient's condition preoperatively for surgery and to exclude any infection.

## X Ray
X-ray spine plays a minimal role in diagnosing spinal cord compression. There are no x-ray findings associated with spinal cord compression.

## CT spine
CT spine is only indicated when MRI is not available. CT guidance is employed in surgical aspiration or drainage of an epidural abscess after the diagnosis confirmed by MRI.

## MRI
MRI spine is diagnostic of spinal cord compression. Findings include extradural spinal hematoma, abscess or tumor, disc rupture, spinal cord hemorrhage, contusion or edema.

# Treatment

## Medical Therapy
All the patients with acute spinal cord compression must be admitted. The mainstay of treatment includes surgery along with adjuvant therapy. In cases of compression caused by metastasis, the treatment is mostly palliative. Antibiotics are indicated in cases of compression caused by an epidural abscess. Dexamethasone (a potent glucocorticoid) in doses of 16 mg/day may reduce edema around the lesion and protect the cord from injury. It may be given orally or intravenously and is indicated in cases of compression caused by edema or acute inflamation.

## Surgery
Surgery is the mainstay of treatment in localized compression. Emergency radiation therapy (usually 20 Gray in 5 fractions) is the mainstay of treatment for malignant spinal cord compression. It is very effective as pain control and local disease control. Some tumors are highly sensitive to chemotherapy (e.g. lymphomas, small cell lung cancer) and may be treated with chemotherapy alone.