Epidural abscess differential diagnosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]

Overview

An epidural abscess is a rare suppurative infection of the central nervous system, a collection of pus localised in the epidural space lying outside the dura mater, which accounts for less than 2% of focal CNS infections. It may occur in two different places: intracranially or in the spinal canal. The diagnosis of epidural abscess, due to the unspecific clinical symptoms, is rarely a quick diagnosis. It is suspected based on clinical findings, along with laboratory data and imaging tests, however it can only be confirmed by surgical drainage. According to the location of the abscess, different conditions must be considered in the differential diagnosis.

Differential Diagnosis

Intracranial Epidural Abscess

An intracranial epidural abscess can replicate the signs and symptoms of any intracranial mass lesion. It may be presented by headache, vomiting, fever, altered mental status, seizures, cranial nerve abnormalities and paresis. However, these signs may not be present initially, and may be shared by other conditions, which increases the complexity of the differential diagnosis. Therefore, the differential diagnosis includes:

• Primary parenchymal tumor - consists in any intracranial tumor located, and with its origin, at the brain parenchyma. Although they can be located anywhere in the brain parenchyma, in children they are commonly located in the posterior cranial fossa, while in adults, they can affect any part of the brain. Because of the diversity of locations brain parenchymal tumors may take, there may also be many different signs and symptoms. These include: focal neurologic signs, increasing intracranial pressure and seizures.
• Metastatic tumor - consists in any intracranial tumor, which has spread from another organ or tissue, making the brain tumor, a secondary tumor. Depending on the location of the brain affected, there will be different signs and symptoms. These may include: focal neurologic signs, increasing intracranial pressure, seizures and others, which may mimic sins and symptoms from epidural abscess.
• Meningioma - consists in a tumor arising from the arachnoidal cap cells of the meninges. In 95% of the cases it's a benign tumor. Depending on the size and location of the tumor, different areas of the brain may be affected, therefore it may manifest itself with different signs and symptoms, including focal neurologic signs, increasing intracranial pressure and seizures. Since these are shared with epidural abscess, this condition should be in the differential diagnosis.
• Hematoma - consists in a collection of blood, usually resulting from an haemorrhage. I may appear as a bruise, if it occurs near the skin, or in internal organs. In the case of happening in the brain, it may work as a mass effect, compressing various structures of the brain, hence causing different signs and symptoms. These may me similar to those of epidural abscess and therefore should be part of the differential diagnosis.
• Subdural empyema - consists of a collection of purulent material, accumulating in the subdural space. Once it exerts a mass effect, it may compress other brain structures, causing various signs and symptoms. Since it also represents an inflammatory component, the inflammation might spread to other brain structures, affecting their normal functioning. The signs and symptoms may include: fever, headache, altered mental status and seizures. As these symptoms are shared by epidural abscess, it should be part of the differential diagnosis.
• Brain abscess - consists of a collection of purulent material within the brain tissue. The infection may originate in a local tissue, such as paranasal sinuses, remote tissue, such as lung or kidney, or be introduced during neurosurgery or head trauma Either the infection of the brain tissue, or the mass effect caused by it, may cause signs and symptoms, similar to the ones of epidural abscess.
• Chronic meningitis - consists in the inflammation of the meninges, as a response to infectious agents, certain drugs, trauma or cancer. The inflammatory process will cause signs and symptoms such as headache, nuchal rigidity, fever and altered mental status, which are similar to those of epidural abscess and why it should be in the differential diagnosis.
• Tuberculous meningitis - consists in the inflammation of the meninges, caused by the organism Mycobacterium tuberculosis. Fever and headache are the cardinal symptoms, however, other symptoms such as confusion and focal neurologic signs may also be present, making tuberculous meningitis an important element of the differential diagnosis.
• Cranial arteritis - or temporal arteritis is an inflammation of the blood vessels of the head, commonly the large and medium arteries. Among others, it may manifest with fever, headache and focal neurologic signs, making it an important element of this differential diagnosis

Spinal Epidural Abscess

At the time of presentation, the diagnosis of spinal epidural abscess is only suspected in 40% of the cases. This is due to the fact that there are several other conditions, more common than this type of abscess, presenting with similar signs and symptoms. Spinal epidural abscess usually presents with back pain, fever, motor weakness, and spinal tenderness. Therefore, the differential diagnosis includes:

• Musculoskeletal pain - can be related to several diseases however, it can be an entity in itself, following overuse and over stretching of muscles, or in the context of a viral infection. When located in the lower back, it may be included in the differential diagnosis of epidural abscess, since this is one of the possible symptoms of this condition.
• Degenerative bone disease - may include several conditions of the bone. The common ground is the weakening of the bone structure, such as in osteoporosis which, among others, may cause low back pain or tenderness and weakness. Since these symptoms may be common with epidural abscess, this condition should be part of the differential diagnosis.
• Intervertebral disc disease - degenerative disc disease is a common disorder of the lower spine, in which disc degeneration may lead to spinal stenosis, spondylolisthesis and osteoarthritis. These conditions may present with low back pain, weakness and tenderness, which explain why this condition should be included in the differential diagnosis.
• Bone tuberculosis - a presentation of extrapulmonary tuberculosis, affecting the bones, most often the spine (Pott's disease, at the level of lower thoracic and upper lobar vertebrae. It results from an hematogenous spread of the organism from other sites, commonly the lung. It may have various signs and symptoms, from which back pain, fever and weakness are common to epidural abscess, making this an important element of the differential diagnosis.Template:Seealso
• Primary or metastatic tumor - consists in any tumor arising from the spinal cord, or elsewhere in the body, which metastasises to the spinal cord. Depending on its location, it may be classified in: extradural, intramural or intramedullary spinal tumor. It will create a mass effect, which will compress the spinal cord and weaken the vertebral structure, causing signs and symptoms, such as: incontinence, weakness in the saddle area and back pain Therefore it should also be included in this differential diagnosis.
• Vertebral osteomyelitis - consists in an infection of the bone and bone marrow, concentrated in the spinal region. It may affect two vertebrae and the disc in between and therefore be responsible for the narrowing of the space between the two. The disease may be acute or chronic, however it is more commonly known to be an acute condition. It may manifest with: fever, back pain, swelling, weakness of the vertebral column and surrounding muscles and night sweats. Since some of the symptoms are shared with epidural abscess, this conditions should be in the differential diagnosis.
• Sciatica secondary to disc herniation - consists in a condition affecting the spine, in which a tear in the outer annulus fibrosus of an intervertebral disc, allows the soft, central nucleus pulposus to bulge out. This tear may cause an inflammatory reaction, which will cause severe pain, even in the absence of spinal compression. It may manifest with: lower back and leg pain, sensory changes, such as tingling and numbness, and reflex changes. Since some of these signs and symptoms are shared with epidural abscess, it should be part of the differential diagnosis.
• Meningitis - consists in the inflammation of the meninges, as a response to infectious agents, certain drugs, trauma or cancer. The inflammatory process will cause signs and symptoms such as headache, back pain, nuchal rigidity, fever and altered mental status, which are similar to those of epidural abscess, and why it should be on the differential diagnosis.
• Herpes zoster - (before appearance of skin lesions) commonly known as shingles, consists of a viral disease, characterized by a painful skin rash with blisters in a limited area, on one side of the body, often in a stripe pattern. Signs and symptoms may include fever, headache, chills and tingling sensations. Since some of these are shared by epidural abscess, this condition should be in the differential diagnosis.