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How do we evaluate patients with neuropathic pain?
Well, there's four steps that I want you to remember
that we walk through in evaluating the patient with pain.
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First, we're going to ask the question,
is this a central nervous system or peripheral nervous system problem?
Problems in both area can contribute to neuropathic pain.
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Second, if the problems in the peripheral nervous system,
we need to know where it is and localize more specifically
to where the problem may be in the peripheral nervous system.
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Third, I want you to think about the medical treatments that exist for treating this type of pain.
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And then, fourth, we're going to walk through some common conditions
that you should remember where neuropathic pain is a prominent feature.
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So let's start with step one. Is this pain from the central or peripheral nervous system?
When we're evaluating patients both using our history and physical,
there's some clues that suggest a central nervous system localization.
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The first would be other central nervous system signs,
cerebellar dysfunction, cognitive dysfunction, altered mental status.
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Those sorts of things tell us the brain is where the problem lies.
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Hemibody symptoms or hemibody findings commonly arise from the central nervous system
and localized to the brain subcortex or brain stem,
and that would point us to a CNS cause of pain.
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A sensory level tells us something's in the spinal cord
and may suggest that the neuropathic pain description's coming from spinal cord pathology and myelopathy.
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Bowel/bladder involvement could be from central or peripheral nervous system.
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A spastic bladder is suggestive of a central nervous system process.
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Cranial nerve involvement suggests brainstem dysfunction.
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And a good example of that would be trigeminal neuralgia
where that pain is coming from a problem in the central nervous system.
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Some of the common conditions we think about
where there's a central nervous system contribution to pain
or thalamic pain syndrome and cord compression.
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What are the clues to a peripheral nervous system localization to pain?
Well, myotomal or dermatomal distribution,
so weakness that's associated with pain in a specific myotome or sensory changes
that are localized to a specific dermatome point to a peripheral nervous system localization.
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Reduced or absent deep tendon reflexes, urinary retention with overflow incontinence,
length-dependent motor, sensory reflex changes or length-dependent motor
and sensory changes on examination.
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Lack of cranial nerve involvement or normal mental status function.
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A rash or other cutaneous symptoms, all those point to neuropathic pain
originating from the peripheral nervous system.
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We want to figure out what that problem is and uncover the etiology of the pain.
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And we can think about some common conditions like radiculopathy, diabetic polyneuropathy
and post-herpetic neuralgia that may present in this way.