Epidural Space Disorders
Epidural space disorders include epidural infection, epidural hematoma or blood clot, epidural abscess and spread of cancer in epidural space.
Epidural Space Occupying Lesions
The epidural space occupying lesions caused by epidural hematoma, blood clot and spread of cancer growth causes severe back pain. Spinal epidural space is also known as extradural space or peridural space. Epidural space is attached to foramen magnum at the cephalic (top) end and sacrum at the caudal (bottom) end. It is the outermost anatomical space of spinal canal, which spreads within vertebral column. Epidural space contains lymphatic vessels, spinal nerve root, loose fatty tissue, arteries and epidural venous plexus.
Epidural abscess, common epidural space disorder, is mostly located in cervical or lumbar epidural space. Epidural abscess follows infection of epidural soft tissue.(1) Most of the abscess is caused by staphylococcus aureus bacterial infection. S. Aureus bacterial infection is often caused by introduction of contaminated needle or catheter in the epidural space during spinal or epidural anesthesia. Other bacterial infection, which may cause epidural abscess are Pseudomonas, E. Coli, Brucella and Mycobacterium.
Tuberculosis. Rarely in a few cases the cause of abscess is found to be fungus infection. Enlarged spinal epidural abscess causes compression or ischemia of spinal cord. As abscess expands, pressure is transferred to blood vessels, nerves and spinal cord within the epidural space.
Epidural hematoma is a blood clot within epidural space. The blood clots following bleeding within the epidural space. The blood clot is known as hematoma.(2) The injury of the blood vessels within epidural space is caused by sharp or blunt instruments. The insertion of epidural needle or spinal needle during epidural or spinal anesthesia causes tear of vein or arteries in the epidural space. The amount of bleeding from epidural vein or artery depends on extent of tear. Larger the tear of artery or vein higher the volume of bleeding and size of blood clot. Similarly, during surgery use of blunt or sharp instruments for dissection of epidural space may cause injury of blood vessels resulting in epidural bleeding and hematoma. The epidural bleeding is also observed during following whiplash injury, fall or impact of hard object over back. The large volume of blood is discharged if individual is taking blood thinning medication.
Primary or metastatic epidural cancer is extremely rare. Occasional epidural lipoma is observed in middle aged patient. Lipoma is a benign fatty tissue tumor. The metastatic cancer from vertebral column may spread through the epidural space. The cancer may spread rapidly through epidural space and cause rapid neurological deterioration.
Symptoms and Signs of Epidural Space Disorders
- Chronic Pain- Chronic pain is a common sign and symptom of epidural space disorders and is caused because epidural hematoma; abscess or cancer growth causes continuous compression and pressure over the nerve in foramina and spinal cord. Radicular pain spread over nerve distribution is caused by pinch or irritation of spinal nerve in foramina. Similarly, back pain mostly localized over midline and paravertebral area is caused by pressure over meninges, ligaments and facet joint. Pain during initial phase is severe, continuous and often stabbing in character. Later pain becomes neuropathic and chronic. Neuropathic pain is felt as a burning pain.
- Tingling and Numbness- Pain follows with symptom of tingling and numbness if pressure is over spinal nerve continuous. The compression of the sensory nerve causes symptoms like tingling and numbness. Partial and unilateral spinal cord injury causes unilateral tingling and numbness. Symptom of tingling and numbness suggests sensory nerve irritation or damage. The symptom is spread over wider area of skin unlike isolated nerve irritation and injury.
- Weakness- Weakness in either chest, abdominal muscles, upper and lower extremities are observed when one side of spinal cord is irritated or pinched. The weakness in upper extremity is observed following continuous unilateral segmental pressure over spinal cord in neck. Weakness in lower extremity is indication of possible resulting in paraplegia if not treated soon.
- Quadriplegia- Narrowing of spinal canal (spinal stenosis) secondary to space occupying lesions causes compression or irritation of spinal cord. Quadriplegia is a loss of sensory and motor function in entire body below the neck. Patient is unable to move upper and lower extremity. Quadriplegia follows severe spinal cord compression in neck. Cervical (neck) section of spinal cord supplies sensory and motor nerves to entire body below the neck. Compression of spinal cord in neck results in quadriplegia.
- Paraplegia- Paraplegia is a total numbness and weakness of lower extremities. Spinal stenosis (narrowing) of thoracic and lumbar vertebral column causes thoracic and lumbar spinal cord injury. Thoracic spinal cord injury causes numbness and weakness of chest, abdomen and both lower extremities. Similarly, compression of spinal cord in lumbar segment causes total numbness and weakness of lower extremities.
- Bowel and Bladder Incontinence- The parasympathetic nerves to urinary bladder and lower bowel like sigmoid colon, rectum and anus lies in lower spinal segment. Compression of spinal cord in lower lumbar spinal canal causes parasympathetic nerve injury. The injury of parasympathetic nerves causes bladder and bowel incontinence.
Lab Studies to Diagnose Epidural Space Disorders
Abnormal Blood Examination-
Blood examination in most cases is normal.
WBC Count- Occasional white blood cell count is increased in patients suffering with epidural infection and abscess.
ESR (Erythrocyte Sedimentation Rate)- ESR is increased when patient is suffering with epidural abscess and cancer.
Blood Culture and antibiotic sensitivity test- The fluid collected from the epidural space is tested by bacterial growth and antibiotic sensitivity test.
X-Ray- X-ray image shows bone growth of metastasis or primary cancer of the vertebra.
Magnetic Resonance Imaging (MRI)- MRI images of vertebrae, epidural space and spinal cord differentiate cancer growth and fluid collection in epidural space. The fluid collection could be hematoma (blood clots) and abscess. The precise spread of the malignant tumor, abscess and blood clot in epidural space can be diagnosed with MRI.
Disc Biopsy- Needle aspiration of the epidural abscess or blood clot is the important test to differentiate cause of epidural space occupying lesions. The lab study differentiates the blood and abscess.
The malignant tissue is difficult to aspirate with needle. The biopsy of the malignant tissue is performed following surgical exposure. The biopsy samples are studied for type of malignancies.
Ultrasound Studies- Ultrasound study differentiates fluid and solid growth. Ultrasound study may not differentiate blood clot and abscess.
Differential Diagnosis of Diseases of Epidural Space
MRI- MRI images provide evidence of epidural space occupying lesions. MRI differentiates Epidural cancer from epidural abscess and hematoma or blood clot.
Biopsy- Biopsy study of epidural space occupying lesions differentiates cancer, abscess and the blood clot.
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