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Showing posts with label MRI. Show all posts
Showing posts with label MRI. Show all posts

Cuases of MRI negative myelopathies

MRI-negative myelopathies refer to spinal cord dysfunctions where the cause cannot be identified through magnetic resonance imaging (MRI). While MRI is a powerful diagnostic tool, it may not detect certain conditions that can cause myelopathy. Some potential causes of MRI-negative myelopathies include:

  1. Vascular disorders: Spinal cord ischemia, arteriovenous malformations, or dural arteriovenous fistulas may not be easily visible on a standard MRI.
  2. Inflammatory or autoimmune conditions: Conditions such as neurosarcoidosis, neuromyelitis optica spectrum disorders, or multiple sclerosis might not always show typical lesions on an MRI.
  3. Infectious causes: Spinal cord infections, such as viral myelitis, bacterial or fungal infections, may not be easily detected on MRI.
  4. Metabolic or nutritional disorders: Vitamin B12 deficiency or copper deficiency can lead to myelopathy, but these may not be visible on MRI.
  5. Genetic or hereditary conditions: Conditions like adrenomyeloneuropathy, hereditary spastic paraplegia, or spinocerebellar ataxias may not always be detected through imaging.
  6. Functional neurological disorders: These disorders involve abnormal nervous system functioning without visible structural damage, and they can mimic myelopathy.
  7. Paraneoplastic syndromes: These rare neurological syndromes can occur as a result of an immune response to cancer and might cause myelopathy without MRI-visible lesions.
  8. Transverse myelitis: In the early stages of this inflammatory spinal cord disorder, MRI findings might be inconclusive or negative.
  9. Traumatic or mechanical causes: Subtle spinal cord trauma or mechanical compression may not be evident on MRI, particularly if the images are not taken in specific positions.
It is important to note that a negative MRI does not rule out the presence of a myelopathy. If a patient presents with clinical symptoms of myelopathy but has a negative MRI, further investigations and diagnostic tests may be required to identify the underlying cause.

Explain the functional MRI mechanism

Functional MRI (fMRI) is a type of brain imaging technique that measures changes in blood flow to different parts of the brain. This technique is based on the fact that when an area of the brain is being used, it requires an increase in blood flow to meet the increased metabolic demands of that activity.

The basic principle of fMRI is known as the blood-oxygen-level-dependent (BOLD) contrast. Oxygen is carried in the blood, and when an area of the brain is active, it requires an increase in blood flow to meet the increased metabolic demand. This increased blood flow is accompanied by a decrease in the amount of oxygen being carried in the blood, resulting in a decrease in the magnetic resonance (MR) signal.

During an fMRI scan, a person is placed inside an MR scanner and a series of MR images are taken while the person performs a specific task or rests. These images can be used to create a map of brain activity, showing which parts of the brain are active during the task.

fMRI has become a widely used tool for studying brain function and has helped to advance our understanding of the brain and its abilities.